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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2015	Mar. 01, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Trading Symbol	RGNX
Entity Registrant Name	REGENXBIO Inc.
Entity Central Index Key	0001590877
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Common Stock, Shares Outstanding		26,328,584
Entity Public Float	$ 331.8

Balance Sheets - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 54,116,000	$ 1,121,000
Marketable securities	60,025,000
Accounts receivable
Trade receivables	2,136,000	805,000
Related party receivables		750,000
Unbilled receivables		327,000
Prepaid expenses	1,020,000	28,000
Other current assets	851,000
Total current assets	118,148,000	3,031,000
Marketable securities	102,226,000
Property and equipment, net	538,000	0
Cost method investments	300,000	303,000
Deferred issuance costs		157,000
Other assets	168,000
Total assets	221,380,000	3,491,000
Current liabilities
Accounts payable	1,014,000	334,000
Accrued expenses and other current liabilities	3,198,000	1,115,000
Due to related party under services agreement		1,423,000
Related party promissory notes		2,403,000
Other related party payables		3,761,000
Advance payments	127,000	153,000
Total current liabilities	4,339,000	9,189,000
Deferred rent, net of current portion	233,000
Total liabilities	4,572,000	9,189,000
Commitments and contingencies (Note 7)
Convertible preferred stock
Convertible preferred stock, value		12,593,000
Stockholders’ equity (deficit)
Preferred stock; $0.0001 par value; 10,000 shares authorized, and no shares issued and outstanding at December 31, 2015; no shares authorized, issued and outstanding at December 31, 2014
Common stock; $0.0001 par value; 100,000 and 9,500 shares authorized at December 31, 2015 and December 31, 2014, respectively; 26,313 and 2,645 shares issued and outstanding at December 31, 2015 and December 31, 2014, respectively	3,000
Additional paid-in capital	269,144,000	10,518,000
Accumulated other comprehensive loss	(719,000)
Accumulated deficit	(51,620,000)	(28,809,000)
Total stockholders’ equity (deficit)	216,808,000	(18,291,000)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 221,380,000	3,491,000
Series A Convertible Preferred Stock [Member]
Convertible preferred stock
Convertible preferred stock, value		3,963,000
Series B Convertible Preferred Stock [Member]
Convertible preferred stock
Convertible preferred stock, value		$ 8,630,000

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Convertible preferred stock, par value		$ 0.0001
Convertible preferred stock, shares authorized		4,299,000
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	9,500,000
Common stock, shares issued	26,313,000	2,645,000
Common stock, shares outstanding	26,313,000	2,645,000
Series A Convertible Preferred Stock [Member]
Convertible preferred stock, par value		$ 0.0001
Convertible preferred stock, shares authorized	0	2,393,000
Convertible preferred stock, shares issued	0	2,393,000
Convertible preferred stock, shares outstanding	0	2,393,000
Preferred stock, shares outstanding		2,393,000
Series B Convertible Preferred Stock [Member]
Convertible preferred stock, par value		$ 0.0001
Convertible preferred stock, shares authorized	0	1,906,000
Convertible preferred stock, shares issued	0	1,906,000
Convertible preferred stock, shares outstanding	0	1,906,000
Preferred stock, shares outstanding		1,906,000

Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues
License revenue	$ 5,025	$ 4,355	$ 1,055
License revenue from related party	2,000	220	2,700
Reagent sales	257	326	368
Grant revenue	306	1,219	1,964
Total revenues	7,588	6,120	6,087
Costs of revenues
Licensing costs (including amounts to related parties)	1,405	885	151
Costs of reagent sales (including amounts to related parties)	98	122	173
Research and development (including amounts to related parties)	17,279	4,961	5,051
General and administrative (including amounts to related parties)	11,912	3,851	5,474
Foreign currency transaction losses	57	30	14
Other operating income	(26)	(47)
Total operating expenses	30,725	9,802	10,863
Loss from operations	(23,137)	(3,682)	(4,776)
Other Income (Expense)
Investment income	346
Interest expense	(20)	(321)	(611)
Total other income (expense)	326	(321)	(611)
Net loss	(22,811)	(4,003)	(5,387)
Other Comprehensive Loss
Unrealized loss on available-for-sale securities	(719)
Total other comprehensive loss	(719)
Comprehensive loss	(23,530)	(4,003)	(5,387)
Reconciliation of net loss to net loss applicable to common stockholders
Net loss	(22,811)	(4,003)	(5,387)
Accretion and dividends on convertible preferred stock	(1,747)	(815)	(422)
Net gain on extinguishment of convertible preferred stock	759
Net loss applicable to common stockholders	$ (23,799)	$ (4,818)	$ (5,809)
Basic and diluted net loss per common share	$ (2.59)	$ (1.82)	$ (2.50)
Weighted-average basic and diluted common shares	9,173	2,643	2,320

Statements of convertible preferred stock and preferred units, and stockholders' and members' equity (deficit) - USD ($) $ in Thousands	Total	Class A Units [Member]	Common Stock [Member]	Additional paid in capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Series A Preferred Stock [Member]	Series B Preferred Stock [Member]	Series A Convertible Preferred Stock [Member]	Series B Convertible Preferred Stock [Member]	Series C Convertible Preferred Stock [Member]	Series D Convertible Preferred Stock [Member]	Convertible Preferred Stock And Preferred Units [Member]
Balances (Shares) at December 31, 2012 at Dec. 31, 2012							119,656,000
Balances at December 31, 2012 at Dec. 31, 2012							$ 3,499						$ 3,499
Issuance of convertible preferred stock, shares		19,476,000						24,155,000
Issuance of convertible preferred stock, net of transaction costs		$ 288				$ (288)		$ 1,965					1,965
Issuance of convertible preferred stock for the conversion of outstanding related party debt, Shares								71,160,000
Issuance of convertible preferred stock for the conversion of outstanding related party debt								$ 5,892					5,892
Accretion of preferred units	$ (422)					(422)	$ 280	$ 142					422
Net loss	(5,387)					(5,387)
Balances (Shares) at December 31, 2013 at Dec. 31, 2013							119,656,000	95,315,000
Balances at December 31, 2013 at Dec. 31, 2013							$ 3,779	$ 7,999					11,778
Balances (Shares) at December 31, 2012 at Dec. 31, 2012		112,672,000
Balances at December 31, 2012 at Dec. 31, 2012	(8,112)	$ 10,597				(18,709)
Balances (Shares) at December 31, 2013 at Dec. 31, 2013		132,148,000
Balances at December 31, 2013 at Dec. 31, 2013	(13,921)	$ 10,885				(24,806)
Accretion of preferred units	(815)			$ (815)					$ 184	$ 631			815
Net loss	$ (4,003)					(4,003)
Balances (Shares) at December 31, 2013 at Dec. 31, 2014	0								2,393,000	1,906,000
Balances at December 31, 2013 at Dec. 31, 2014	$ 12,593								$ 3,963	$ 8,630			12,593
Conversion from LLC to C corporation, Shares		(132,148,000)	2,643,000				(119,656,000)	(95,315,000)	2,393,000	1,906,000
Conversion from LLC to C corporation		$ (10,885)		10,885			$ (3,779)	$ (7,999)	$ 3,779	$ 7,999
Exercise of stock options	1			1
Stock-based compensation expense	319			319
Balances (Shares) at December 31, 2013 at Dec. 31, 2014			2,645,000
Balances at December 31, 2013 at Dec. 31, 2014	(18,291)			10,518		(28,809)
Discount on Related Party Promissory Notes	128			128
Exercise of stock options, Shares			2,000
Issuance of convertible preferred stock, shares			7,245,000								4,047,000	7,367,000
Issuance of convertible preferred stock, net of transaction costs	145,184		$ 1	145,183							$ 26,021		26,021
Issuance of convertible preferred stock, net of transaction costs												$ 67,998	67,998
Issuance of convertible preferred stock for the conversion of outstanding related party debt, Shares											585,000
Issuance of convertible preferred stock for the conversion of outstanding related party debt											$ 3,792		3,792
Accretion of preferred units	(1,747)			(1,747)					(2,280)	1,338	$ 187	$ 2,502	1,747
Net loss	$ (22,811)					(22,811)
Balances (Shares) at December 31, 2013 at Dec. 31, 2015	0
Exercise of stock options	$ 107			107
Stock-based compensation expense	2,921			2,921
Loss (gain) on extinguishment of convertible preferred stock	759			759					$ 1,317	$ (2,076)			(759)
Conversion of convertible preferred stock into common stock upon initial public offering, Shares			16,298,000						(2,393,000)	(1,906,000)	(4,632,000)	(7,367,000)
Conversion of convertible preferred stock into common stock upon initial public offering	111,392		$ 2	111,390					$ (3,000)	$ (7,892)	$ (30,000)	$ (70,500)	$ (111,392)
Unrealized loss on available-for-sale securities	(719)				$ (719)
Balances (Shares) at December 31, 2013 at Dec. 31, 2015			26,313,000
Balances at December 31, 2013 at Dec. 31, 2015	216,808		$ 3	269,144	$ (719)	$ (51,620)
Discount on Related Party Promissory Notes	$ 13			$ 13
Exercise of stock options, Shares			125,000

Statements of convertible preferred stock and preferred units, and stockholders' and members' equity (deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Series B Preferred Stock [Member]
Issuance of Stock, transaction costs	$ 35
Series B Convertible Preferred Stock [Member]
Issuance of Stock, transaction costs	187
Series D Convertible Preferred Stock [Member]
Issuance of Stock, transaction costs	2,502
Common Stock [Member]
Issuance of Stock, transaction costs	$ 14,206

Statements of Cash Flows - USD ($)	12 Months Ended
Statements of Cash Flows - USD ($)	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities
Net loss	$ (22,811,000)	$ (4,003,000)	$ (5,387,000)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	2,921,000	319,000
Imputed interest on related party promissory notes	13,000	128,000
Unrealized foreign currency transaction losses	11,000	44,000	14,000
Net amortization of premiums and accretion of discounts on marketable debt securities	311,000
Depreciation and amortization	80,000	0	0
Non-cash consideration received for licenses granted			(303,000)
Other non-cash adjustments		3,000
Changes in operating assets and liabilities
Trade receivables	(1,342,000)	(799,000)	(36,000)
Related party receivables	750,000	174,000	(924,000)
Unbilled receivables	327,000	(213,000)	109,000
Prepaid expenses	(992,000)	(28,000)
Other current assets	(851,000)
Other assets	(168,000)
Accounts payable	590,000	33,000	257,000
Accrued expenses and other current liabilities	2,221,000	764,000	107,000
Due to related party under services agreement	(34,000)	768,000	3,192,000
Other related party payables	(3,761,000)	258,000	(41,000)
Advance payments	(26,000)	153,000
Deferred rent	246,000
Net cash used in operating activities	(22,515,000)	(2,399,000)	(3,012,000)
Cash flows from investing activities
Purchases of marketable securities	(163,278,000)
Purchases of property and equipment	(522,000)
Net cash used in investing activities	(163,800,000)
Cash flows from financing activities
Proceeds from issuance of Series B preferred units, net of transaction costs			1,965,000
Proceeds from related party promissory notes		2,400,000
Proceeds from exercise of stock options	107,000	1,000
Proceeds from initial public offering of common stock, net of transaction costs	145,184,000
Net cash provided by financing activities	239,310,000	2,401,000	1,965,000
Net increase (decrease) in cash and cash equivalents	52,995,000	2,000	(1,047,000)
Cash and cash equivalents
Beginning of period	1,121,000	1,119,000	2,166,000
End of period	54,116,000	1,121,000	1,119,000
Supplemental cash flow information
Cash paid for interest	7,000	164,000
Supplemental disclosures of non-cash investing and financing activities
Conversion of related party promissory notes into Series C convertible preferred stock	1,389,000
Conversion of convertible preferred stock into common stock upon initial public offering	111,392,000
Purchases of property and equipment in accounts payable and accrued expenses	96,000
Deferred issuance costs for Series C convertible preferred stock in accrued expenses		$ 157,000
Non-cash consideration received for licenses granted			303,000
Series B Preferred Units [Member]
Supplemental disclosures of non-cash investing and financing activities
Conversion of accrued service fees to related party			$ 5,892,000
Series C Convertible Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of convertible preferred stock, net of transaction costs	26,021,000
Supplemental disclosures of non-cash investing and financing activities
Conversion of accrued service fees to related party	2,403,000
Series D Convertible Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of convertible preferred stock, net of transaction costs	$ 67,998,000

Nature of Business	12 Months Ended
Nature of Business	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business	1. Nature of Business REGENXBIO Inc. (the Company) was formed on July 16, 2008 in the state of Delaware as ReGenX, LLC, and on December 22, 2009, changed its name to ReGenX Biosciences, LLC. On September 16, 2014, the Company converted from a limited liability company (LLC) to a C-corporation, and changed its name to REGENXBIO Inc. The Company uses its proprietary NAV^® Technology platform and collaborates with clinical advisors to advance the development of gene therapy treatments for a range of severe diseases with unmet needs. Initial Public Offering On September 22, 2015, the Company completed its initial public offering (IPO) whereby the Company sold 7,245 shares of common stock (inclusive of 945 shares of common stock sold by the Company pursuant to the full exercise of an option to purchase additional shares granted to the underwriters in connection with the offering) at a price of $22.00 per share. The shares began trading on The Nasdaq Global Select Market on September 17, 2015. The aggregate net proceeds received by the Company from the offering were $145,184, net of underwriting discounts and commissions and offering expenses payable by the Company. Upon the closing of the IPO, all outstanding shares of convertible preferred stock converted into 16,298 shares of common stock. Liquidity and Risks As of December 31, 2015, the Company had generated an accumulated deficit of $51,620 since inception. As the Company continues to incur losses, transition to profitability is dependent upon the successful development, approval and commercialization of its product candidates and achieving a level of revenues adequate to support the Company’s cost structure. The Company may never achieve profitability, and unless and until it does, the Company will continue to need to raise additional capital. As of December 31, 2015, the Company had cash, cash equivalents and marketable securities of $216,367, which management believes is sufficient to fund operations for at least the next twelve months. The Company is subject to risks common to companies in the biotechnology industry, including, but not limited to, development by the Company or its competitors of technological innovations, risks of failure of clinical trials, dependence on key personnel, protection of proprietary technology, compliance with government regulations and ability to transition from preclinical manufacturing to commercial production of products.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (GAAP). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States (U.S.) generally accepted accounting principles as found in the Accounting Standards Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB).

Foreign Currency Transactions

Transaction gains (losses) that arise from exchange rate fluctuations on transactions denominated in a currency other than the U.S. dollar are included in the statements of operations and comprehensive loss as incurred.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Actual results could materially differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements. Estimates are used in the following areas, among others: stock-based compensation expense, accrued research and development expenses and the fair value of financial instruments.

Segment and Geographical Information

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker (CODM), or decision making group, in making decisions on how to allocate resources and assess performance. The Company’s CODM, the Chief Executive Officer, views its operations and manages its business as one operating segment.

For the year ended December 31, 2015, 78 percent and 21 percent of the Company’s revenue was generated from customers located in the U.S. and Europe, respectively. For the year ended December 31, 2014, 60 percent and 40 percent of the Company’s revenue was generated from customers located in the U.S. and Europe, respectively. For the year ended December 31, 2013, 86 percent and 13 percent of the Company’s revenue was generated from customers located in the U.S. and Europe, respectively. Country of origin for revenue is determined by the Company based on the country of domicile of licensees for license revenue, the country in which reagent sales are delivered to for reagent sales and the location of grantors for government grant revenue. All of the Company’s assets currently reside in the U.S.

Cash and Cash Equivalents

The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents. Cash and cash equivalents include cash held in banks and money market mutual funds.

Marketable Securities

The Company’s marketable securities are classified as available-for-sale and are carried at fair value. Marketable securities with remaining maturity dates exceeding twelve months which are not intended to be sold prior to maturity for use in current operations are classified as non-current. Unrealized gains and losses, net of any related tax effects, are excluded from earnings and are included in other comprehensive loss and reported as a separate component of stockholders’ equity until realized. A decline in the fair value below cost of available-for-sale securities that is deemed other-than-temporary is charged to results of operations, resulting in the establishment of a new cost basis for the security. Premiums and discounts are amortized or accreted into the cost basis over the life of the related security as adjustments to the yield using the effective-interest method. Interest income is recognized when earned. Realized gains and losses from the sale of marketable securities are based on the specific identification method and are included in results of operations.

The Company regularly evaluates whether declines in the fair value of its investments below their cost are other-than-temporary. The evaluation includes consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of securities in an unrealized loss position, the severity and duration of the unrealized losses, whether the Company has the intent to sell the securities and whether it is more likely than not that the Company will be required to sell the securities before the recovery of their amortized cost basis. If the Company determines that the decline in fair value of an investment is below its accounting basis and this decline is other-than-temporary, the Company would reduce the carrying value of the security it holds and record a loss for the amount of such decline. The Company has not recorded any declines in value judged to be other-than-temporary on its investments.

Concentrations of Credit Risk and Off-balance Sheet Risk

Cash and cash equivalents, marketable securities and accounts receivable are financial instruments that are potentially subject to concentrations of credit risk. The Company’s cash and cash equivalents are deposited in accounts at multiple financial institutions, and amounts may exceed federally insured limits. The Company believes it is not exposed to significant credit risk due to the financial strength of the depository institutions in which the cash and cash equivalents are held. The Company’s marketable securities consist of fixed income corporate debt securities and may subject the Company to concentrations of credit risk. The Company has adopted an investment policy which limits potential concentrations of investments and establishes minimum acceptable credit ratings, thereby reducing credit risk exposure. Management believes that it is not exposed to significant credit risk related to accounts receivable due to the credit quality and history of collections from its significant customers. The Company has no financial instruments with off-balance sheet risk of loss.

The following table summarizes those customers who represented at least 10 percent of revenue or accounts receivable for the periods presented:

	Revenue									Accounts Receivable
	Years Ended December 31,									December 31,
	2015			2014			2013			2015			2014
Customer A	*				33	%	*			*			*
Customer B	*				14	%		11	%		25	%		46	%
Customer C⁽¹⁾		41	%	*				44	%	*				40	%
Customer D	*			*			*			*				11	%
Customer E	*			*				21	%	*			*
Customer F		16	%	*			*				42	%	*
Customer G		22	%	*			*				19	%	*

*	Represented less than 10%

(1)	Represents a related party prior to September 30, 2015

Accounts Receivable

Trade accounts receivable consist of amounts due to the Company resulting from the Company’s licensing arrangements, reagent sales and grant programs. Related party accounts receivable consists of amounts due from related parties (Note 13). Unbilled receivables consist of estimated costs incurred under the Company’s grant programs which have not yet been submitted to the grantor for reimbursement. Receivables are stated net of an allowance for doubtful accounts, if deemed necessary based on the Company’s evaluation of collectability using specific identification of account balances and historical information regarding write-offs. Account balances are charged off against the allowance when the potential for recovery is considered remote. The Company has not recorded an allowance for doubtful accounts as of December 31, 2015 or 2014.

Deferred Issuance Costs

Deferred issuance costs, which consist of direct and incremental fees relating to the issuance of equity securities are capitalized. As of December 31, 2014, the Company capitalized $157 of deferred issuance costs related to Series C convertible preferred stock (Series C Preferred Stock) (Note 8), which were offset against the proceeds from the issuance of the Series C Preferred Stock in January 2015. As of December 31, 2015, no amounts were deferred.

Property and Equipment

Property and equipment is stated at cost. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred. Upon disposal, the related cost and accumulated depreciation is removed from the accounts and any resulting gain or loss is included in the results of operations. Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized. Depreciation and amortization is calculated using the straight-line method over the estimated useful lives of the assets, which are as follows:


Computer equipment and software			3 years
Lab equipment			5 years
Furniture and fixtures			5 years
Leasehold improvements			Shorter of lease term or estimated useful life

Impairment of Long-lived Assets

The Company reviews long-lived assets when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparison of the book values of the assets to estimated future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceed their fair value, which is measured based on the projected discounted future net cash flows arising from the assets. No impairment losses have been recorded during the years ended December 31, 2015, 2014 and 2013.

Cost Method Investments

Cost method investments consist of non-marketable holdings in certain corporations and are stated at cost. The Company accounts for its investments in other entities using the cost method if its ownership interest is below 20 percent and the Company does not have significant influence over the operations of the entity. As of December 31, 2015, the Company’s cost method investment in Audentes Therapeutics, Inc. (Audentes) (Note 9) had a carrying value of $300. As of December 31, 2014, cost method investments in Audentes and Dimension Therapeutics, Inc. (Dimension) (Note 13) had a carrying value of $303.

Declines in the fair value of cost method investments below their carrying value that are deemed to be other-than-temporary are reflected in the statements of operations and comprehensive loss as realized losses. In estimating other-than-temporary impairment losses, management considers, among other things, the length of time and the extent to which the fair value has been less than cost, the financial condition and near-term prospects of the issuer and the intent and ability of the Company to retain its investments in the issuer for a period of time sufficient to allow for the anticipated recovery in fair value. The Company has not identified any events or changes in circumstances that would have an adverse effect on the fair value of its cost method investments. Accordingly, no other-than-temporary impairment losses were recorded for the years ended December 31, 2015, 2014 and 2013.

The Company applies the variable interest model under FASB ASC Topic 810, Consolidation (ASC 810), to any entity in which the Company holds an equity investment or to which the Company has granted a commercial license. If the entity is within the scope of the model, and meets the definition of a variable interest entity (VIE), the Company considers whether it must consolidate the VIE or if further disclosures regarding the Company’s involvement with the VIE are necessary. If the Company is determined to be the primary beneficiary of the VIE, the Company will consolidate the VIE. This analysis is performed at the initial investment in the entity or the inception of the commercial license agreement, or upon any reconsideration event.

The Company considers a legal entity a VIE if (i) its investors do not have sufficient equity at risk for the legal entity to finance its activities without additional subordinated financial support or (ii) as a group, the holders of the equity investment at risk do not have both the power to direct the activities of the legal entity that most significantly impact the entity’s economic performance and the obligation to absorb the expected losses or the right to receive expected residual returns of the legal entity. The Company considers itself to be the primary beneficiary of a VIE if the Company has both the power to direct the activities that most significantly affect the VIE’s economic performance and the obligation to absorb the losses of, or right to receive benefits from, the VIE that could be potentially significant to the VIE. If the Company, or any of the Company’s related parties which have a variable interest in the VIE, individually lack the necessary power and benefits criteria, but the related party group as a whole has the necessary power and benefits, the Company determines which of the related party group members is most closely associated with the VIE and considers that party to be the primary beneficiary. As of December 31, 2015 and 2014, the Company has not consolidated any VIE’s. See Note 13 for further information regarding the Company’s involvement and variable interests in related parties and entities controlled by related parties.

Related Party Debt Instruments

The Company evaluates each of its related party debt instruments (Note 6) with embedded features under FASB ASC Topic 815, Derivatives and Hedging (ASC 815). More specifically, the Company evaluates all of the stated and implied substantive terms and features of the debt, including: (i) whether the debt included redemption features, (ii) how and when any redemption features could be exercised and settled and (iii) the existence and nature of any conversion rights.

Fair Value of Financial Instruments

The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC Topic 820, Fair Value Measurements and Disclosures (ASC 820), establishes a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The three levels of the fair value hierarchy are described below:

Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable.

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Please refer to Note 4 for further information on the fair value measurement of the Company’s financial instruments.

Convertible Preferred Stock and Preferred Units

In accordance with the guidance in FASB ASC Topic 480, Distinguishing Liabilities from Equity, outstanding shares of convertible preferred stock and preferred units (Note 8) were classified outside of permanent equity and within temporary equity as of December 31, 2014 due to their associated redemption features and liquidation preferences. At each reporting date, each series of convertible preferred stock and preferred units is accreted and stated at the amounts in which each series is currently redeemable, which is also equal to the aggregate liquidation preference at that date.

The Company evaluated each series of its convertible preferred stock and preferred units and determined that each individual series is considered a debt host under ASC 815. In making this determination, the Company’s analysis followed the whole instrument approach which compares an individual feature against the entire convertible preferred stock or preferred unit instrument which includes that feature. The Company’s analysis was based on a consideration of the economic characteristics and risks of each series of convertible preferred stock and preferred units. More specifically, the Company evaluated all of the stated and implied substantive terms and features, including: (i) whether the convertible preferred stock and preferred units included redemption features, (ii) how and when any redemption features could be exercised, (iii) whether the holders of convertible preferred stock and preferred units were entitled to dividends and how those dividends were calculated, (iv) the voting rights of the convertible preferred stock and preferred units and (v) the existence and nature of any conversion rights. As a result of the Company’s conclusion that the convertible preferred stock and preferred units represent a debt host, the redemption features of all series of convertible preferred stock and preferred units were considered to be clearly and closely related to the associated debt host instruments. Accordingly, the redemption features of all series of convertible preferred stock were not considered embedded derivatives that required bifurcation. The Company also concluded that the conversion rights under the convertible preferred stock were not clearly and closely related to the debt host instruments. However, the Company concluded that the conversion rights did not meet the net settlement criteria of a derivative and, therefore, were not considered embedded derivatives that required bifurcation.

The Company accounts for potential beneficial conversion features of convertible preferred stock under FASB ASC 470-20, Debt with Conversion and Other Options. At the time of each of the issuances of convertible preferred stock, the Company’s common stock into which each series of the Company’s convertible preferred stock was convertible had an estimated fair value less than the effective conversion prices of the convertible preferred stock. Therefore, there was no intrinsic value on the respective issuance dates.

Revenue Recognition

The Company primarily generates revenue through license agreements with third parties which may grant rights to the research, development, and commercialization of product candidates using the Company’s NAV® Technology. Additionally, the Company has generated revenue from grant programs and sales of licensed reagents to customers for use in research and development.

The Company recognizes revenue in accordance with FASB ASC Topic 605, Revenue Recognition (ASC 605). Accordingly, revenue is recognized for each unit of accounting when all of the following criteria are met:

Persuasive evidence of an arrangement exists;

Delivery has occurred or services have been rendered;

The seller’s price to the buyer is fixed or determinable; and

Collectability is reasonably assured.

Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s balance sheets.

The Company analyzes its revenue arrangements based on the guidance in FASB ASC Topic 605-25, Revenue Recognition-Multiple-Element Arrangements (ASC 605-25). Pursuant to the guidance in ASC 605-25, the Company evaluates multiple-element arrangements to determine (i) the deliverables included in the arrangement and (ii) whether the individual deliverables represent separate units of accounting or whether they must be accounted for as a combined unit of accounting. This evaluation involves subjective determinations and requires management to make judgments about the individual deliverables and whether such deliverables are separable from the other aspects of the contractual relationship. Deliverables are considered separate units of accounting provided that: (i) the delivered item(s) has value to the customer on a standalone basis and (ii) if the arrangement includes a general right of return relative to the delivered item(s), delivery or performance of the undelivered item(s) is considered probable and substantially in the control of the Company. The Company does not have any material revenue arrangements that contain multiple deliverables.

License Revenue and License Revenue From Related Party. The terms of the Company’s license agreements require delivery of an intellectual property license for use of the Company’s intellectual property in research and/or commercial development of product candidates for various diseases. License agreements generally have a term equal to the life of the intellectual property, but are terminable at the option of the licensee. Non-refundable payments to the Company under these arrangements may include: (i) up-front license fees, (ii) option fees to exercise options to obtain commercial licenses, (iii) annual maintenance fees, (iv) sublicense fees, (v) payments based on the achievement of certain milestones based solely on the efforts of the licensees and (vi) royalties on product sales.

Nonrefundable up-front license fees are recognized as revenue upon delivery of the license provided there are no undelivered elements in the arrangement and the necessary criteria under ASC 605 for revenue recognition have been met.

Options to exercise commercial licenses are considered substantive if, at the inception of the arrangement, the Company is at risk as to whether the licensee will choose to exercise the option. Factors that the Company considers in evaluating whether an option is substantive include the overall objective of the arrangement, the benefit the licensee might obtain from the arrangement without exercising the option, the cost to exercise the option and the likelihood that the option will be exercised. For arrangements under which an option is considered substantive, the Company does not consider the item underlying the option to be a deliverable at the inception of the arrangement and the associated option fees are not included in allocable arrangement consideration, provided the option is not priced at a significant and incremental discount. Conversely, for arrangements under which an option is not considered substantive or if an option is priced at a significant and incremental discount, the Company would consider the item underlying the option to be a deliverable at the inception of the arrangement and a corresponding amount would be included in allocable arrangement consideration. As of December 31, 2015 and 2014, all of the options included in the Company’s license agreements have been determined to be substantive, and none of the options are priced at a significant and incremental discount. Option fees are recognized as revenue upon exercise and delivery of the underlying commercial license, provided there are no undelivered elements in the arrangement and the necessary criteria under ASC 605 for revenue recognition have been met.

Annual maintenance fees under the Company’s license agreements do not represent a separate deliverable aside from the delivery of the license since the Company has no further obligations under the agreements. Accordingly, annual maintenance fees are recognized as revenue when billable under the agreement, provided the price is fixed or determinable and collectability is deemed reasonably assured.

Sublicense fees are payable to the Company upon the receipt of certain fees by the licensee from any sublicensees. Sublicense fees received by the Company are recognized as revenue when the price is fixed or determinable and collectability is deemed reasonably assured.

At the inception of an arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the respective milestone and the level of effort and investment required to achieve the respective milestone in making this assessment. There is considerable judgment involved in determining whether a milestone satisfies all of the criteria required to conclude that a milestone is substantive. The Company has concluded that all of the clinical, regulatory and commercial milestones pursuant to its license agreements are substantive. Milestone payments are recognized as revenue upon achievement of the milestone by the licensee, provided that all other revenue recognition criteria are satisfied.

The Company recognizes royalty revenue, if any, in the period of sale of the related product(s) based on the underlying contract terms, provided that the reported sales are reliably measurable and the Company has no remaining performance obligations, and provided that all other revenue recognition criteria under ASC 605 are satisfied. To date, the Company has not generated any royalty revenues.

Please refer to Note 13 for information regarding license revenue from related party.

Grant Revenue. Grant revenue is generated through research and development grant programs offered by the U.S. federal government and the European Union. Government grants provide funds for certain types of expenditures in connection with research and development activities over a contractually defined period. Revenue related to government grants is recognized in the period during which the related costs are incurred and the related services are rendered, provided that the applicable performance obligations under the grants have been met. Funds received under grants are recorded as revenue if the Company is deemed to be the principal participant and primary obligor in the contract arrangements because the activities under the contracts are part of the Company’s development programs. If the Company is not the principal participant or primary obligor, the grant proceeds are recorded as a reduction to research and development expense.

The Company’s grants contain refund provisions. The Company reviews those refund provisions to determine the likelihood of repayment. If the likelihood of repayment of the grant is determined to be remote, the grant is recognized as revenue. If the probability of repayment is determined to be more than remote, the Company records the amount of potential repayment of the grant as a liability, until such time that the grant requirements have been satisfied. Funds received in advance of the performance of the services are recorded as deferred revenue. Please refer to Note 9 for further information regarding the Company’s grant agreements.

Reagent Sales. Reagent sales consist of sales of licensed reagents to third parties for use in research and development. Revenue from reagent sales is recognized upon delivery to customers, provided that all other revenue recognition criteria under ASC 605 are satisfied.

Research and Development Expenses

Research and development costs are charged to expense as costs are incurred. Research and development costs include salaries and benefits, other personnel costs, facilities costs, overhead costs, preclinical and clinical contract services, regulatory, manufacturing and other related costs. Up-front fees incurred in obtaining technology licenses are charged to research and development expense as incurred if the technology licensed has no alternative future use. Advance payments for goods or services for future research and development activities are deferred and expensed as the goods are delivered or the related services are performed.

The Company estimates research and development expenses for manufacturing activities, process development, preclinical studies and clinical trials based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage the activities on the Company’s behalf. In accruing these research and development expenses, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. These estimates are based on communications with the third party service providers and other information available to the Company at each balance sheet date. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. There have been no significant changes from the Company’s original estimates in any of the periods presented.

Stock-based Compensation

The Company accounts for its stock-based compensation awards in accordance with FASB ASC Topic 718, Compensation—Stock Compensation (ASC 718). ASC 718 requires all stock-based payments to employees, including grants of employee stock options, to be recognized in the statement of operations and comprehensive loss based on their fair values.

The Company’s stock-based awards are subject to either service or performance-based vesting conditions. Compensation expense related to awards to employees with service-based vesting conditions is recognized on a straight-line basis based on the estimated grant date fair value over the associated service period of the award, which is generally the vesting term. Compensation expense related to awards to non-employees with service-based vesting conditions is recognized based on the then-current fair value at each financial reporting date prior to the measurement date over the associated service period of the award, which is generally the vesting term, on a straight-line basis. Compensation expense related to awards to employees with performance-based vesting conditions is recognized based on the estimated grant date fair value over the requisite service period using the accelerated attribution method to the extent achievement of the performance condition is probable. Compensation expense related to awards to non-employees with performance-based vesting conditions is recognized based on the then-current fair value at each financial reporting date prior to the measurement date over the requisite service period using the accelerated attribution method to the extent achievement of the performance condition is probable.

The Company estimates the fair value of its option awards to employees and directors using the Black-Scholes option-pricing model, which requires the input of and subjective assumptions, including (i) the fair value of the underlying common stock, (ii) the expected stock price volatility, (iii) the calculation of expected term of the award, (iv) the risk-free interest rate and (v) expected dividends. Due to the lack of company specific historical and implied volatility data of its common stock, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. When selecting these public companies on which it has based its expected stock price volatility, the Company selected companies with comparable characteristics to it, including enterprise value, risk profiles, position within the industry and with historical share price information sufficient to meet the expected term of the stock-based awards. The Company will continue to apply this method of estimating expected volatility until a sufficient amount of historical information regarding the volatility of its own common stock price becomes available. The Company computes historical volatility data using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. The Company has estimated the expected term of its employee stock options using the “simplified” method, whereby, the expected term equals the arithmetic average of the vesting term and the original contractual term of the option due to its lack of sufficient historical data. The risk-free interest rates for periods within the expected term of the option are based on the U.S. Treasury securities with a maturity date commensurate with the expected term of the associated award. The Company has never paid, and does not expect to pay dividends in the foreseeable future.

The Company is also required to estimate forfeitures at the time of grant and revise those estimates in subsequent periods if actual forfeitures differ from its estimates. To date, a forfeiture rate of zero has been used to calculate stock-based compensation expense. To the extent that actual forfeitures differ from the Company’s estimates, the differences are recorded as a cumulative adjustment in the period the estimates were revised. Stock-based compensation expense recognized in the financial statements is based on awards that are ultimately expected to vest.

The Company has granted stock options to non-employees as compensation for advisory services provided to the Company. Consistent with the guidance in FASB ASC Topic 505-50, Equity-Based Payments to Non-Employees, the fair value of each non-employee stock option is estimated at the date of grant using the Black-Scholes option-pricing model with assumptions generally consistent with those used for employee stock options, with the exception of expected term, which is based on the contractual life.

Income Taxes

Income taxes are recorded in accordance with FASB ASC Topic 740, Income Taxes (ASC 740), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. As of December 31, 2015 and 2014, the Company did not have any significant uncertain tax positions.

The Company will recognize interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2015 and 2014, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s statements of operations and comprehensive loss.

Net Loss Per Share

On September 16, 2014, the Company converted from an LLC to a C-corporation. Upon the conversion, every 50 Class A Units, Series A Preferred Units and Series B Preferred Units (Note 8) held were converted into 1 share of common stock, Series A convertible preferred stock (Series A Preferred Stock) and Series B convertible preferred stock (Series B Preferred Stock), respectively. Class A Units of the LLC had similar rights and characteristics of common stock issued upon the conversion. In calculating net loss per share, the Company retrospectively applied the effects of the conversion to the number of Class A Units, Series A Preferred Units and Series B Preferred Units outstanding prior to the conversion. Net loss per share for periods prior to the conversion to a C-corporation refers to net loss per Class A Unit.

The Company computes net loss per share in conformity with the two-class method required for participating securities. The Company considers all series of convertible preferred stock outstanding prior to the IPO, and all series of preferred units outstanding prior to the conversion to a C-corporation, to be participating securities. The holders of convertible preferred stock outstanding prior to the IPO were entitled to receive preferential dividends in the event that a dividend was to be paid to the holders of common stock, and the holders of preferred units outstanding prior to the conversion to a C-corporation were entitled to a preferred return in the event that operating distributions were to be paid to the Class A Unit holders of the LLC. The holders of convertible preferred stock and preferred units did not have a contractual obligation to share in the losses of the Company. As such, the Company’s net losses for the years ended December 31, 2015, 2014 and 2013 were not allocated to these participating securities. In connection with the IPO, all outstanding shares of convertible preferred stock were automatically converted into shares of common stock.

Basic net loss per share is calculated by dividing net loss applicable to holders of common stock by the weighted-average shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting weighted-average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. For purposes of the diluted net loss per share calculation, convertible preferred stock and preferred units, stock options and debt instruments containing share settlement options are considered to be common stock equivalents but have been excluded from the calculation of diluted net loss per share, as their effect would be anti-dilutive. Contingently convertible shares in which conversion is based on non-market-priced contingencies are excluded from the calculations of both basic and diluted net loss per share until the contingency has been fully met. Accordingly, basic and diluted net loss per share and unit were the same for all periods presented.

Comprehensive Loss

The Company’s comprehensive loss includes its net loss as well as net unrealized losses on available-for-sale securities.

Recently Announced Accounting Pronouncements

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) which supersedes FASB ASC Topic 840, Leases (Topic 840) and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than twelve months regardless of classification. Leases with a term of twelve months or less will be accounted for similar to existing guidance for operating leases. The standard is effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted upon issuance. The Company is evaluating the application of this ASU, but has not yet determined the potential effects it may have on the Company’s financial statements.

In January 2016, the FASB issued ASU 2016-01, Financial Instruments—Overall (Topic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, which supersedes the current guidance to classify equity securities with readily determinable fair values into different categories and requires equity securities to be measured at fair value with changes in the fair value recognized through net income (loss). This guidance is effective for annual and interim periods beginning after December 15, 2017. The Company is evaluating the application of this ASU, but has not yet determined the potential effects it may have on the Company’s financial statements.

In February 2015, the FASB issued ASU 2015-2, Consolidation (Topic 810): Amendments to the Consolidation Analysis, which provides clarification regarding the guidance surrounding consolidation of certain legal entities. This guidance is effective for annual and interim periods beginning after December 15, 2015. The Company has evaluated the application of this ASU, and determined that it does not have a material effect on the Company’s financial statements.

In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern, requiring management to evaluate whether events or conditions could impact an entity’s ability to continue as a going concern and to provide disclosures if necessary. Management will be required to perform the evaluation within one year after the date that the financial statements are issued. Disclosures will be required if conditions give rise to substantial doubt and the type of disclosure will be determined based on whether management’s plans will be able to alleviate the substantial doubt. The ASU will be effective for the first annual period ending after December 15, 2016, and for annual periods and interim periods thereafter with early application permitted. The Company is evaluating the application of this ASU, but has not yet determined the potential effects it may have on the Company’s financial statement disclosures.

In June 2014, the FASB issued ASU No. 2014-12, Compensation—Stock Compensation (Topic 718): Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could be Achieved after the Requisite Service Period, which requires the Company to assess share-based awards with performance targets that could be achieved after the requisite service period for potential treatment as performance conditions. Under the ASU, compensation expense is to be recognized when the performance target is deemed probable and should represent the compensation expense attributable to the periods for which service has already been rendered. If the performance target is reached prior to achievement of the service period, the remaining unrecognized compensation cost should be recognized over the remaining service period. The ASU is effective for annual and interim periods beginning after December 15, 2015 with early adoption permitted. The Company has evaluated the application of this ASU, and determined that it does not have a material effect on the Company’s financial statements.

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes the revenue recognition requirements in ASC 605, Revenue Recognition. This ASU is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The ASU also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606), which deferred the effective date of the guidance under ASU No. 2014-09 for entities by one year. The ASU is now effective for annual and interim reporting periods beginning after December 15, 2017. Earlier application is permitted only as of annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. The Company is evaluating the application of this ASU, but has not yet determined the potential effects it may have on the Company’s financial statements.

Marketable Securities

12 Months Ended

Dec. 31, 2015

Investments Debt And Equity Securities [Abstract]

Marketable Securities

3. Marketable Securities

The following table presents a summary of the Company’s marketable securities, which consist solely of available-for-sale securities:

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2015
Corporate bonds	$	157,977	$	4	$	(759	)	$	157,222
Commercial paper		4,990		—		—			4,990
Common equity securities		3		36		—			39
	$	162,970	$	40	$	(759	)	$	162,251

The Company’s common equity securities consist of shares of common stock of Dimension, which became a publicly traded company in October 2015. The Company obtained these shares in connection with a license granted to Dimension in October 2013 (Note 13). The Company is restricted from trading these securities until April 2016 pursuant to a lock-up agreement entered into in connection with Dimension’s IPO. The Company has classified these shares as available-for-sale securities and recognized an unrealized gain of $36 which is included in other comprehensive loss for the year ended December 31, 2015. Prior to Dimension’s IPO, the shares were not marketable and were accounted for as a cost method investment on the Company’s balance sheets.

As of December 31, 2015, no available-for-sale securities had remaining maturities greater than three years. The Company did not hold any available-for-sale securities as of December 31, 2014.

The amortized cost of available-for-sale securities is adjusted for amortization of premiums and accretion of discounts to maturity. As of December 31, 2015, the balance in the Company’s accumulated other comprehensive loss consisted solely of net unrealized gains and losses on available-for-sale securities. For the year ended December 31, 2015, the Company recognized net unrealized losses on available-for-sale securities of $719, which is included in other comprehensive loss. There were no realized gains or losses recognized on the sale or maturity of available-for-sale securities during the year ended December 31, 2015, and as a result, the Company did not reclassify any amounts out of accumulated other comprehensive loss for the period.

As of December 31, 2015, the Company did not hold any available-for-sale securities in an unrealized loss position for more than twelve months. The aggregate fair value of securities held by the Company in an unrealized loss position for less than twelve months as of December 31, 2015 was $155,486, which consisted of corporate debt securities with credit ratings of A-2/A or higher. The Company has the intent and ability to hold such securities until recovery. The Company determined that there have been no material changes in the credit risk of these investments since their initial purchases. As a result, the Company determined that none of these investments are other-than-temporarily impaired as of December 31, 2015.

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References + Details

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

4. Fair Value of Financial Instruments

Financial instruments reported at fair value on a recurring basis include cash equivalents and marketable securities. Cash equivalents consist solely of money market mutual funds. Marketable securities consist of corporate debt securities, including corporate bonds and commercial paper, as well as common equity securities as disclosed in Note 3. The following tables present the fair value of cash equivalents and marketable securities in accordance with the hierarchy discussed in Note 2:

	Quoted		Significant
	prices		other		Significant
	in active		observable		unobservable
	markets		inputs		inputs
	(Level 1)		(Level 2)		(Level 3)		Total
December 31, 2015
Money market mutual funds (cash equivalents)	$	—	$	54,104	$	—	$	54,104
Corporate bonds (marketable securities)		—		157,222		—		157,222
Commercial paper (marketable securities)		—		4,990		—		4,990
Common equity securities (marketable securities)		39		—		—		39
	$	39	$	216,316	$	—	$	216,355

	Quoted		Significant
	prices		other		Significant
	in active		observable		unobservable
	markets		inputs		inputs
	(Level 1)		(Level 2)		(Level 3)		Total
December 31, 2014
Money market mutual funds (cash equivalents)	$	—	$	844	$	—	$	844
	$	—	$	844	$	—	$	844

Management estimates that the carrying amounts of its accounts receivable, accounts payable, accrued expenses and other current liabilities and related party payables approximate fair value due to the short-term nature of those instruments.

Certain debt instruments (Note 6) outstanding at December 31, 2014 accrued interest at below market rates. The Company has recorded a discount to the face value of the instrument to account for the difference between the present value of the debt at an estimated market rate versus face value. Accordingly, management believes that the carrying values of all debt instruments approximate fair value.

The Company has determined that it is not practicable to estimate the fair value of cost method investments. The Company has not identified any events or changes in circumstances that would have an adverse effect on the fair value of its cost method investments.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Property and Equipment, Net

12 Months Ended

Dec. 31, 2015

Property Plant And Equipment [Abstract]

Property and Equipment, Net

5. Property and Equipment, Net

Property and equipment, net consists of the following:

	December 31,
	2015
Computer equipment and software	$	458
Furniture and fixtures		105
Leasehold improvements		55
Total property and equipment		618
Accumulated depreciation and amortization		(80	)
Property and equipment, net	$	538

As of December 31, 2014, the Company had no property and equipment because the Company’s resources used in operations were provided by a related party (Note 13). Accordingly, no depreciation or amortization expense was recorded for the years ended December 31, 2014 and 2013. The Company recorded $80 of depreciation and amortization expense for the year ended December 31, 2015.

Related Party Debt Instruments	12 Months Ended
Related Party Debt Instruments	Dec. 31, 2015
Debt Disclosure [Abstract]
Related Party Debt Instruments	6. Related Party Debt Instruments Due to Related Party Under Services Agreement Until terminated in January 2015, the Company was party to a services agreement with FoxKiser LLP (FoxKiser), a related party (Note 13). Under the services agreement, the Company paid a fixed monthly fee and a support fee to FoxKiser. Amounts outstanding under the services agreement in excess of 30 days from their due date accrued interest at 1.5 percent per month, compounding monthly. The Company entered into an agreement (the Initial Conversion Agreement) with FoxKiser in which all principal and interest owed under the services agreement as of September 30, 2013, which was $5,892, may be settled at the option of FoxKiser, in whole or in part, (i) upon the next issuance of preferred equity securities by the Company, in shares of such preferred equity securities issued at a price per share equal to the issuance price of such shares, or (ii) if an issuance of preferred equity securities has not taken place by December 31, 2013, in shares of common equity securities of the Company at a price per share equal to the fair value of such common equity securities as determined by the Board of Directors. The debt is deemed fully settled upon conversion into equity securities of the Company. On October 30, 2013, in conjunction with the Company’s issuance of Series B Preferred Units (Note 8), FoxKiser converted the entire $5,892 outstanding under the Initial Conversion Agreement into 71,160 Series B Preferred Units at a price per unit of $0.082798. On July 31, 2014, the Company entered into another agreement (the Second Conversion Agreement) with FoxKiser. Under the Second Conversion Agreement, all principal and interest owed under the services agreement between the Company and FoxKiser on or after July 31, 2014, with a maximum amount of $2,000, may be settled at the option of FoxKiser, in whole or in part, (i) upon the next issuance of preferred equity securities by the Company, in shares of such preferred equity securities issued at a price per share equal to the issuance price of such shares, or (ii) if an issuance of preferred equity securities has not taken place by December 31, 2014, in shares of common equity securities of the Company at a price per share equal to the fair value of such common equity securities as determined by the Board of Directors. The debt is deemed fully settled upon conversion into equity securities of the Company. As of December 31, 2014, the Company had accrued $1,423 payable to FoxKiser under the services agreement, which contained an option to be settled in preferred or common shares in accordance with the Second Conversion Agreement. Related Party Promissory Notes On July 31, 2014, the Company received $1,800 in exchange for a promissory note issued to FoxKiser. On September 15, 2014, the Company received $600 in exchange for a second promissory note issued to FoxKiser. Both promissory notes accrued interest at the Short-Term Applicable Federal Rate (0.34% at December 31, 2014), compounding annually, and were payable on demand by FoxKiser at the earlier of December 31, 2014 or the next issuance of preferred equity securities by the Company. Both promissory notes may be settled at the option of FoxKiser, in whole or in part, (i) upon the next issuance of preferred equity securities by the Company, in shares of such preferred equity securities issued at a price per share equal to the issuance price of such shares, or (ii) if an issuance of preferred equity securities has not taken place by December 31, 2014, in shares of common equity securities of the Company at a price per share equal to the fair value of such common equity securities as determined by the Board of Directors. The debt is fully settled upon conversion into equity securities of the Company. The promissory notes with FoxKiser bear interest at below-market rates. Accordingly, the Company imputed interest on the promissory notes and recorded a discount equal to the difference between the face value of the promissory notes and the present value of the notes at an estimated market rate of 15 percent. The aggregate discount of $128 on the promissory notes was amortized using the effective interest method through December 31, 2014, at which date the notes became payable upon demand by FoxKiser. The discount was recorded as additional paid-in capital from FoxKiser due to the related party nature of the borrowing arrangements. Amortization of the discount is recorded as interest expense in the statements of operations and comprehensive loss. As of December 31, 2014, the promissory notes had an outstanding principal of $2,400, and accrued interest of $3. The Company evaluated the embedded features of each of its debt instruments under ASC 815. The Company has concluded that the redemption features, including all put and call features, with the exception of settlement upon a liquidation or change in control as discussed further below, are clearly and closely related to the debt host instruments and, therefore, are not considered embedded derivatives that require bifurcation. Additionally, the Company concluded that the share settlement rights of the debt instruments do not require bifurcation as embedded derivatives because in the event of a settlement in shares, the debt is settled in a variable number of equity securities with an aggregate fair value equaling the debt principal outstanding on the debt host instruments. Pursuant to the terms of the Initial Conversion Agreement, Second Conversion Agreement and each of the promissory notes with FoxKiser, in the event of a liquidation or change in control, as defined in the agreements, the Company shall pay two times (2x) the principal and accrued interest then outstanding in order to settle the debt. The Company evaluated this redemption feature in accordance with ASC 815 and determined that it is an embedded derivative that should be bifurcated from each of the debt host instruments. However, due to the low probability of a liquidation or change in control event, the Company has determined that the liability associated with this derivative instrument is de minimis as of December 31, 2014. As discussed below, upon the conversion of the debt instruments into Series C Convertible Preferred Stock in January 2015, this redemption feature is no longer outstanding. On January 13, 2015, in conjunction with the Company’s issuance of Series C Preferred Stock (Note 8), FoxKiser elected its share settlement options and converted $1,389 of the amount due under the services agreement and $2,403 of principal and interest due under the promissory notes, for a total of $3,792, into 585 shares of Series C Preferred Stock at a per share price of $6.477. The promissory notes were settled in full upon the conversion, and the Company terminated the services agreement with FoxKiser and paid the remainder of the outstanding service fees in full. As of December 31, 2015, no amounts were outstanding under the services agreement or promissory notes with FoxKiser. Interest expense to FoxKiser under the services agreement and promissory notes, inclusive of imputed interest, for the years ended December 31, 2015, 2014 and 2013 was $20, $321 and $611, respectively.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2015

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7. Commitments and Contingencies

Lease Agreements

The Company recognizes rent expense on a straight-line basis over the term of its operating leases commencing on the date the Company takes possession of the leased property. Tenant improvement allowances which are considered to be lease incentives from the lessor are recorded as deferred rent and amortized as a reduction of rent expense over the term of the lease from the possession date.

In January 2015, the services agreement with FoxKiser (Note 13) was terminated and the Company entered into an operating lease with FoxKiser for office space in Washington, D.C. The lease agreement, which had a month-to-month term, required monthly payments of $20. The lease was terminated in April 2015.

In March 2015, the Company entered into a 5.5-year, non-cancelable operating lease for office space in Rockville, Maryland. The lease commenced in April 2015, and expires in September 2020. The Company has options to extend the lease for up to 6 years. Initial monthly payments required under the lease were $24 beginning in October 2015 and escalate annually in accordance with the lease.

In September 2015, and again in October 2015, the Company amended its operating lease in Rockville, Maryland to include additional office and laboratory space and extend the term of the lease for its existing space to October 2020. The lease for the additional space is expected to commence in April 2016, and has a 5-year term. The Company has options to extend the lease for the additional space to be coterminous with the Company’s existing lease at that facility. Initial monthly payments required under the lease for the additional space are $41 and escalate annually in accordance with the lease. The Company received a $286 tenant improvement allowance from the landlord which will be deferred and amortized on a straight-line basis as a reduction of rent expense over the term of lease.

The Company has entered into various short-term operating leases for office and laboratory space in Bethesda, Maryland and Philadelphia, Pennsylvania, which expire at various dates through June 2016.

As of December 31, 2015, future minimum lease payments under non-cancelable operating leases are as follows:

	Operating
	Leases
2016	$	777
2017		824
2018		848
2019		874
2020		832
Thereafter		144
Total minimum lease payments	$	4,299

Rent expense under all operating leases, including additional rent charges for utilities, parking, property management, operating expenses and real estate taxes for the years ended December 31, 2015, 2014 and 2013 was $396, $45 and $45, respectively.

In January 2016, the Company entered into a non-cancelable operating lease for additional office space in Rockville, Maryland. The lease is expected to commence by March 2016, and has term of approximately 7.5 years. Initial monthly payments required under the lease are $38 beginning seven months from the commencement date and escalate annually in accordance with the lease. The Company received a $725 tenant improvement allowance from the landlord which, if used by the Company, will be deferred and amortized on a straight-line basis as a reduction of rent expense over the term of lease.

Licenses Granted to the Company

Licenses granted to the Company may require the Company to make future payments relating to sublicense fees, milestone fees for milestones not met as of December 31, 2015 and royalties on future sales of licensed products. Additionally, the Company may be responsible for the cost of the maintenance of the intellectual property as incurred by its licensors. Up-front fees to obtain licensed technology are included in research and development expenses and patent maintenance costs are included in general and administrative expenses in the statements of operations and comprehensive loss. Sublicense fees are based on a specified percentage of license fees earned by the Company and are included in licensing costs in the statements of operations and comprehensive loss. Royalties on sales of licensed reagents for use in research and development are included in costs of reagent sales in the statements of operations and comprehensive loss. The Company has not commercialized any product candidates or paid any royalties under these agreements other than for the sales of licensed reagents.

The Trustees of the University of Pennsylvania. On February 20, 2009, the Company entered into a license agreement, as amended, with The Trustees of the University of Pennsylvania (Penn) for exclusive, worldwide rights to certain patents owned by Penn underlying the Company’s NAV® Technology platform. Under the terms of the agreement, in consideration for the license, the Company issued to Penn 24.5 percent of the then outstanding membership interest in the LLC on a fully diluted basis after issuance. The Company is obligated to pay Penn royalties on net sales and sublicense fees, if any. Additionally, the Company is obligated to reimburse Penn for certain costs incurred related to the maintenance of the licensed patents.

Expenses incurred by the Company related to its license from Penn were as follows:

	Years Ended December 31,
	2015		2014		2013
Sublicense fees	$	703	$	443	$	76
Royalties on sales of reagents		9		17		18
Maintenance of licensed patents		154		256		120
	$	866	$	716	$	214

As of December 31, 2015 and 2014, the Company had accrued $440 and $305, respectively, in expenses payable to Penn under the license agreement. As of December 31, 2015, these amounts are included in accounts payable and accrued expenses and as of December 31, 2014, these amounts are included in other related party payables on the Company’s balance sheets. Until September 30, 2015, the Company considered Penn to be a related party. For the nine months ended September 30, 2015, the Company incurred $264, $8 and $118 in expenses for sublicense fees, royalties on reagent sales and reimbursement of patent maintenance costs, respectively, under its license from Penn. See Note 13 for further information on related party transactions with Penn.

GlaxoSmithKline LLC. On March 6, 2009, the Company entered into a license agreement, as amended, with GlaxoSmithKline LLC (GSK) for exclusive, worldwide rights to certain patents underlying the Company’s NAV® Technology platform which are owned by Penn and exclusively licensed to GSK. Under the terms of the agreement, in consideration for the license the Company issued to GSK 19.9 percent of then outstanding membership interest in the LLC on a fully diluted basis after issuance. The Company is obligated to pay GSK royalties on net sales and sublicense fees, if any. Additionally, the Company is obligated to reimburse GSK for certain costs incurred and invoiced to the Company related to the maintenance of the licensed patents. The Company is obligated to pay GSK up to $1,500 upon the achievement of various milestones. As of December 31, 2015, no milestones have been achieved and accordingly no milestone payments were payable to GSK.

Expenses incurred by the Company related to its license from GSK were as follows:

	Years Ended December 31,
	2015		2014		2013
Sublicense fees	$	703	$	443	$	76
Royalties on sales of reagents		5		10		11
Maintenance of licensed patents		573		432		455
	$	1,281	$	885	$	542

As of December 31, 2015 and 2014, the Company had accrued $526 and $2,028, respectively, in expenses payable to GSK under the license agreement. As of December 31, 2015, these amounts are included in accounts payable and accrued expenses and as of December 31, 2014, these amounts are included in other related party payables on the Company’s balance sheets. Until September 30, 2015, the Company considered GSK to be a related party. For the nine months ended September 30, 2015, the Company incurred $264, $5 and $474 in expenses for sublicense fees, royalties on reagent sales and reimbursement of patent maintenance costs, respectively, under its license from GSK. See Note 13 for further information on related party transactions with GSK.

ARIAD Pharmaceuticals, Inc. On November 19, 2010, the Company entered into a license agreement with ARIAD Pharmaceuticals, Inc. (ARIAD), for exclusive, worldwide rights to certain patents owned and exclusively licensed by ARIAD. In consideration for the license, the Company issued Class A Units to ARIAD with a fair value of $726. Under the terms of the agreement, the Company is obligated to pay ARIAD royalties on net sales, and sublicense fees, if any. Additionally, the Company is obligated to pay ARIAD up to $2,300 and annual maintenance fees of $50 upon the achievement of various milestones. As of December 31, 2015, no milestones have been achieved and accordingly no milestone payments or maintenance fees were payable to ARIAD. Additionally, the Company has not incurred any royalties or sublicense fees payable to ARIAD since the inception of the agreement. The Company had no amounts due to ARIAD under the agreement as of December 31, 2015 and 2014.

Regents of the University of Minnesota. On November 10, 2014, the Company entered into a license agreement with Regents of the University of Minnesota (Minnesota), for an exclusive license under certain patent rights to commercialize products covered by the licensed patent rights in any country or territory in which a licensed patent has been issued and is unexpired, or a licensed patent application is pending. In consideration for the license, the Company paid an up-front fee of $25 and reimbursed Minnesota for patent maintenance expenses of $9. Under the terms of the agreement, the Company is obligated to pay Minnesota annual maintenance fees between $5 and $15 per year on each anniversary date of the agreement. Additionally, the Company is obligated to pay royalties on net sales and sublicense fees, if any, and up to $125 per licensed product upon the achievement of various milestones. As of December 31, 2015 and 2014, no milestones have been achieved and accordingly no milestone payments were payable to Minnesota. Additionally, the Company has not incurred any royalties or sublicense fees payable to Minnesota since the inception of the agreement. The Company had no amounts due to Minnesota under the agreement as of December 31, 2015 and 2014.

Guarantees and Indemnifications

In the normal course of business, the Company enters into agreements that contain a variety of representations and provide for general indemnification. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. As of December 31, 2015 and 2014, the Company did not have any material indemnification claims that were probable or reasonably possible and consequently has not recorded any related liabilities.

Capitalization

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Capitalization

8. Capitalization

In connection with the IPO, which closed on September 22, 2015, all of the outstanding shares of the Company’s convertible preferred stock were converted into 16,298 shares of its common stock. As of December 31, 2015, the authorized capital stock of the Company included 100,000 shares of common stock, par value $0.0001 per share, and 10,000 shares of preferred stock, par value $0.0001 per share. The Company’s restated certificate of incorporation and bylaws, which were adopted in connection with the IPO, contain the rights, preferences and privileges of the Company’s stockholders and their respective shares.

As of December 31, 2014, the authorized capital stock of the Company included 9,500 shares of common stock, par value $0.0001 per share, and 4,299 shares of preferred stock, par value $0.0001 per share. The Company’s authorized preferred stock included 2,393 shares designated as Series A Preferred Stock and 1,906 shares designated as Series B Preferred Stock.

Preferred Units

On December 31, 2010, the Company issued 119,656 Series A Preferred Units at a per unit price of $0.0251 for aggregate proceeds of $3,000. On October 30, 2013, the Company issued 95,315 Series B Preferred Units at a per unit price of $0.082798 for an aggregate amount of $7,857, net of issuance costs of $35. The aggregate purchase price of $7,857 included $1,965 of net cash proceeds from new investors and the conversion $5,892 of debt under the Initial Conversion Agreement (Note 6) with FoxKiser. The Series A Preferred Units and Series B Preferred Units are herein collectively referred to as “Preferred Units.”

Holders of the Preferred Units were entitled to a pre-tax cumulative internal rate of return of 8 percent per annum, compounding annually (the Preferred Return). Subsequent to the issuance of the Series B Preferred Units, Preferred Units were redeemable by the holder upon the majority vote of all Preferred Unit holders on a per unit basis on or after October 30, 2018. The redemption price of the Preferred Units was equal to the original issue price of each unit held plus any amounts due under the Preferred Return on the redemption date.

Conversion to C-corporation

On September 16, 2014, the Company converted from an LLC to a C-corporation. Upon the conversion, Preferred Units were subject to a 50-to-1 reverse unit split, and converted into Series A Preferred Stock and Series B Preferred Stock of the Company. Specifically, the 119,656 Series A Preferred Units issued and outstanding on the conversion date were converted into 2,393 shares of Series A Preferred Stock, and the 95,315 Series B Preferred Units issued and outstanding on the conversion date were converted into 1,906 shares of Series B Preferred Stock.

Upon the conversion to a C-corporation and filing of the Company’s certificate of incorporation on September 16, 2014, and as of December 31, 2014, rights, preferences and privileges of Series A Preferred Stock and Series B Preferred Stock consisted of the following:

Dividends. The holders of Series A Preferred Stock and Series B Preferred Stock were entitled to receive dividends, in preference to common stock, on a pro rata basis, at a dividend rate equal to $0.1003 and $0.331192 per annum for each share of Series A Preferred Stock and Series B Preferred stock, respectively. Dividends were cumulative and accrued on each share of Series A Preferred Stock and Series B Preferred Stock from the respective original date of issuance of each share. After payment dividends to holders of Series A Preferred Stock and Series B Preferred Stock, any additional dividends were to be made to the holders of Series A Preferred Stock, Series B Preferred Stock and common stock in proportion to the number of shares of common stock that would be held by each holder if all shares of Series A Preferred Stock and Series B Preferred Stock were converted to common stock at the then effective conversion rate. As of December 31, 2015 the Company has not declared or paid any dividends or operating distributions since its inception.

Liquidation Preference. In the event of a liquidation event, as defined below, either voluntary or involuntary, the holders of Series A Preferred Stock and Series B Preferred Stock had preference over common stock to any proceeds from liquidation at an amount equal to the original issuance price per share of Series A Preferred Stock and Series B Preferred Stock plus any accrued but unpaid dividends, whether declared or not, and any other declared but unpaid dividends. A liquidation event includes (i) the sale or disposition of substantially all of the Company’s assets or the exclusive license of substantially all of the Company’s intellectual property, (ii) a merger or consolidation in which the stockholders of the Company prior to the transaction no longer hold at least 50 percent of the voting power of the merged or consolidated entity, (iii) a transaction, or series of transactions, which results in a single party, or group of affiliated entities representing a single party, owning 50 percent of more the Company’s equity securities or (iv) a liquidation, dissolution, or winding up of the Company. For purposes of the liquidation preference, the original issuance price of Series A Preferred Stock and Series B Preferred Stock was $1.255 and $4.1399 per share, respectively. If proceeds from the liquidation event were insufficient to pay the entire liquidation preference to holders of Series A Preferred Stock and Series B Preferred Stock, then the proceeds were to be distributed ratably among the holders of Series A Preferred Stock and Series B Preferred Stock in proportion to the total preferential amount each holder was entitled to under the liquidation preference. Upon full payment of the liquidation preference, any remaining proceeds were to be distributed among the holders of Series A Preferred Stock and Series B Preferred Stock and common stock pro rata based on the number of shares of common stock, assuming full conversion of all Series A Preferred Stock and Series B Preferred Stock into common stock, held by each holder. For purposes of determining the amount each holder of Preferred Stock was entitled to receive with respect to a liquidation event, holders of Series A Preferred Stock and Series B Preferred Stock were deemed to have their shares converted into shares of common stock immediately prior to the liquidation event if, as a result of an actual conversion, the holder would receive an aggregate amount greater than the amount that would be distributed if the holder’s preferred shares had not been converted into common stock. If the holder was deemed to have converted shares of Series A Preferred Stock and Series B Preferred Stock into shares of common stock for purposes of the liquidation preference, then the holder was not entitled to receive any distribution that would be made to holders of preferred shares that were not converted.

Redemption. Series A Preferred Stock and Series B Preferred Stock was redeemable upon the majority vote of all Series A Preferred Stock and Series B Preferred Stock holders on a per share basis, after October 30, 2018. The redemption price of the Series A Preferred Stock and Series B Preferred Stock was equal to the original issue price of each share held plus all accrued but unpaid dividends, whether or not declared, and was to be paid in three annual installments beginning on the first redemption date. For purposes of the redemption price, the original issuance price of Series A Preferred Stock and Series B Preferred Stock was $1.255 and $4.1399 per share, respectively.

Conversion. Each share of Series A Preferred Stock and Series B Preferred Stock was convertible at the option of the holder at any point in time into fully paid and non-assessable shares of common stock. Upon conversion, the Series A Preferred Stock and Series B Preferred Stock would be fully settled. Each share of Series A Preferred Stock and Series B Preferred Stock was convertible into that number of shares of common stock as determined by dividing the original issuance price of such share by the applicable conversion price. For purposes of determining the conversion rate, the original issuance price of Series A Preferred Stock and Series B Preferred Stock was $1.255 and $4.1399 per share, respectively. As of December 31, 2014, the conversion rate was 1:1, but was subject to future adjustments to the conversion price upon the occurrence of certain events including (i) certain future issuances of common stock at a price less than the conversion price in effect on the date of such issuance, and (ii) future stock splits, subdivisions or combinations of outstanding common stock.

Each share of Series A Preferred Stock and Series B Preferred Stock would automatically convert into shares of common stock at the applicable conversion rate upon (i) a qualified public offering, as defined in the Certificate of Incorporation, at a per share price no less than $20.6995 per share (as adjusted for any stock splits, stock dividends, combinations, subdivisions, recapitalizations or the like) and $50,000 in aggregate gross proceeds, prior to deduction of underwriting discounts and commissions, or (ii) the majority vote of the holders of Series A Preferred Stock and Series B Preferred Stock on a per share and as-converted to common stock basis.

Voting. The holders of each share of Series A Preferred Stock and Series B Preferred Stock had the right to one vote for each share of common stock into which the shares could then be converted. Holders of Series A Preferred Stock and Series B Preferred Stock had full voting rights and powers equal to those of common stock holders. As long as shares of Series A Preferred Stock remained outstanding, the holders of Series A Preferred Stock, voting as a separate class, were entitled to elect three directors to the Board of Directors. As long as shares of Series B Preferred Stock remained outstanding, the holders of Series B Preferred Stock, voting as a separate class, were entitled to elect one director to the Board of Directors. The holders of outstanding common stock, voting as a separate class, were entitled to elect one director to the Board of Directors. The holders of Preferred Stock and common stock, voting together as a single class on an as-converted basis for Preferred Stock, were entitled to elect any remaining directors of the Company.

The Company evaluated the conversion of Series A Preferred Units and Series B Preferred Units into Series A Preferred Stock and Series B Preferred Stock, respectively, giving consideration to all changes in the rights, preferences and privileges of each class of securities. As a result of the conversion, holders of previously issued preferred units were given a conversion option to convert their newly issued preferred stock into common stock. Additionally, dividends on the newly issued preferred shares were no longer compounded annually as they were under the Preferred Return, which decreased the liquidation and redemption values of the securities. Management determined that the changes to these rights, privileges and preferences should be accounted for as a modification of the securities.

Issuance of Series C Preferred Stock

On January 13, 2015, the Company completed the issuance and sale of 4,632 shares of Series C Preferred Stock, par value $0.0001 per share, at a per share price of $6.477 for aggregate gross proceeds of $30,000. The aggregate purchase price of $30,000 included $26,021 of cash proceeds, net of issuance costs of $187, and the conversion of $3,792 of debt as discussed in Note 6.

Extinguishment of Preferred Stock

In connection with the issuance of the Series C Preferred Stock in January 2015, the rights, preferences and privileges of Series A Preferred Stock and Series B Preferred Stock then outstanding were modified. More specifically, Series C Preferred Stock received preference in dividends and liquidation proceeds over Series A Preferred Stock and Series B Preferred Stock. Additionally, the dividend rights changed from cumulative dividend rights to non-cumulative dividend rights, and all accrued but unpaid cumulative dividends on the Series A Preferred Stock and Series B Preferred Stock as of January 13, 2015 were forfeited. As a result of this modification, the redemption value and liquidation preferences of Series A Preferred Stock and Series B Preferred Stock, which were previously equal to original issue price plus accrued but unpaid cumulative dividends, were reduced to original issue price plus non-cumulative dividends declared. Additionally, the redemption date of Series A Preferred Stock and Series B Preferred Stock was changed from October 30, 2018 to December 31, 2019.

The Company has accounted for the amendment to the rights, preferences and privileges of the Series A Preferred Stock and Series B Preferred Stock as an extinguishment of the original convertible preferred stock and issuance of new convertible preferred stock due to the significance of the modifications to the substantive contractual terms of the convertible preferred stock and the associated fundamental changes to the nature of the convertible preferred stock. Accordingly, upon extinguishment the Company recorded a loss of $1,317 on the Series A Preferred Stock and a gain of $2,076 on the Series B Preferred Stock within stockholders’ equity (deficit) equal to the difference between the fair value of the new shares of preferred stock issued and the carrying amount of the old shares of preferred stock extinguished. The Company allocated the entire net gain on extinguishment of convertible preferred stock of $759 to additional paid-in capital. The net gain on extinguishment is reflected in the calculation of net loss available to common stockholders in accordance with FASB ASC Topic 260, Earnings per Share. The fair value of the Series A Preferred Stock and Series B Preferred Stock was determined using the option-pricing method (OPM) back-solve method on the per share price of Series C Preferred Stock to estimate aggregate equity value. The OPM was used to allocate equity value to the Series A Preferred Stock and Series B Preferred stock using the Black-Scholes option-pricing model.

Issuance of Series D Preferred Stock

On May 15, 2015, the Company completed the sale and issuance of 7,367 shares of Series D Preferred Stock, par value $0.0001 per share, at a per share price of $9.5699 for proceeds of $67,998, net of issuance costs of $2,502.

In connection with the issuance of the Series D Preferred Stock, the Company amended and restated its certificate of incorporation. Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock and Series D Preferred Stock are herein collectively referred to as Preferred Stock. Under the amended and restated certificate of incorporation in effect prior to the IPO, the rights, preferences and privileges of Preferred Stock consisted of the following:

Dividends. The holders of Series D Preferred Stock were entitled to receive dividends, in preference to Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock and common stock when and if declared by the Company’s Board of Directors. After payment of dividends to holders of Series D Preferred Stock, holders of Series C Preferred Stock were entitled to receive dividends in preference to Series A Preferred Stock, Series B Preferred Stock and common stock. After payment of dividends to holders of Series C Preferred Stock, holders of Series A Preferred Stock and Series B Preferred Stock were entitled to receive dividends in preference to common stock. Dividends to holders of Preferred Stock were non-cumulative and had a dividend rate equal to $0.1003, $0.331192, $0.51816 and $0.765592 per annum for each share of Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock and Series D Preferred Stock, respectively. After payment of dividends to holders of Preferred Stock, any additional dividends were to be made to the holders of Preferred Stock and common stock in proportion to the number of shares of common stock that would be held by each holder if all shares of Preferred Stock were converted to common stock at the then effective conversion rate.

Liquidation Preference. In the event of a liquidation event, as defined below, either voluntary or involuntary, the holders of Series D Preferred Stock had preference over Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock and common stock to any proceeds from liquidation. Upon payment of the liquidation preference to holders of Series D Preferred Stock, holders of Series C Preferred Stock had preference in liquidation proceeds over holders of Series A Preferred Stock, Series B Preferred Stock and common stock. Upon payment of the liquidation preference to holders of Series C Preferred Stock, holders of Series A Preferred Stock and Series B Preferred Stock had preference in liquidation proceeds over holders of common stock. Liquidation preferences of Preferred Stock were at an amount equal to the original issuance price per share of Preferred Stock plus any accrued but unpaid dividends, whether declared or not, and any other declared but unpaid dividends. A liquidation event included (i) the sale or disposition of substantially all of the Company’s assets or the exclusive license of substantially all of the Company’s intellectual property, (ii) a merger or consolidation in which the stockholders of the Company prior to the transaction no longer hold at least 50 percent of the voting power of the merged or consolidated entity, (iii) a transaction, or series of transactions, which results in a single party, or group of affiliated entities representing a single party, owning 50 percent or more of the Company’s equity securities, or (iv) a liquidation, dissolution, or winding up of the Company. For purposes of the liquidation preference, the original issuance price of Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock and Series D Preferred Stock was $1.255, $4.1399, $6.477 and $9.5699 per share, respectively. If proceeds from the liquidation event were insufficient to pay the entire liquidation preference to holders of any series of Preferred Stock, then the proceeds were to be distributed ratably among the holders of that series of Preferred Stock in proportion to the total preferential amount each holder is entitled to under the liquidation preference. Upon full payment of the liquidation preference, any remaining proceeds were to be distributed among the holders of Preferred Stock and common stock pro rata based on the number of shares of common stock, assuming full conversion of all Preferred Stock into common stock, held by each holder. For purposes of determining the amount each holder of Preferred Stock was entitled to receive with respect to a liquidation event, holders of Preferred Stock were deemed to have their shares of Preferred Stock converted into shares of common stock immediately prior to the liquidation event if, as a result of an actual conversion, the holder would receive an aggregate amount greater than the amount that would be distributed if the holder’s Preferred Shares had not been converted into common stock. If the holder was deemed to have converted shares of Preferred Stock into shares of common stock for purposes of the liquidation preference, then the holder was not entitled to receive any distribution that would be made to holders of Preferred Stock that were not converted.

Redemption. All series of Preferred Stock were redeemable upon the majority vote of all Preferred Stock holders on a per share basis, after December 31, 2019. The redemption price of the Preferred Stock was equal to the original issue price of each share held plus all accrued but unpaid dividends, whether or not declared, and was to be paid in three annual installments beginning on the first redemption date. For purposes of the redemption price, the original issuance price of Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock and Series D Preferred Stock was $1.255, $4.1399, $6.477 and $9.5699 per share, respectively.

Conversion. Each share of Preferred Stock was convertible at the option of the holder at any point in time into fully paid and non-assessable shares of common stock. Upon conversion, the Preferred Stock would be fully settled. Each share of Preferred Stock was convertible into that number of shares of common stock as determined by dividing the original issuance price of such share by the applicable conversion price. For purposes of determining the conversion rate, the original issuance price of Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock and Series D Preferred Stock was $1.255, $4.1399, $6.477 and $9.5699 per share, respectively. Initially, the conversion rate was 1:1 for each series of Preferred Stock, but was subject to future adjustments to the conversion price upon the occurrence of certain events including (i) certain future issuances of common stock at a price less than the conversion price in effect on the date of such issuance and (ii) future stock splits, subdivisions, or combinations of outstanding common stock.

Each share of Preferred Stock was to automatically convert into shares of common stock at the applicable conversion rate upon (i) a qualified public offering, as defined in the Company’s amended and restated certificate of incorporation, of at least $40,000 in aggregate gross proceeds, prior to deduction of underwriting discounts and commissions, or (ii) the majority vote of the holders of Preferred Stock on a per share and as-converted to common stock basis.

Voting. The holders of each share of Preferred Stock had the right to one vote for each share of common stock into which the Preferred Stock could then be converted. Holders of Preferred Stock had full voting rights and powers equal to those of common stockholders.

As long as shares of Series A Preferred Stock remained outstanding, the holders of Series A Preferred Stock, voting as a separate class, were entitled to elect three directors to the Board of Directors. As long as shares of Series B Preferred Stock remained outstanding, the holders of Series B Preferred Stock, voting as a separate class, were entitled to elect one director to the Board of Directors. As long as shares of Series C Preferred Stock remained outstanding, the holders of Series C Preferred Stock, voting as a separate class, were entitled to elect one director to the Board of Directors. As long as shares of Series D Preferred Stock remained outstanding, the holders of Series D Preferred Stock, voting as a separate class, were entitled to elect one director to the Board of Directors. The holders of outstanding common stock, voting as a separate class, were entitled to elect one director to the Board of Directors. The holders of Preferred Stock and common stock, voting together as a single class on an as-converted basis for Preferred Stock, were entitled to elect any remaining directors of the Company.

Prior to the closing of the IPO on September 22, 2015, all of the outstanding shares of the Company’s Preferred Stock were converted into 16,298 shares of its common stock. As of December 31, 2015, the Company did not have any preferred equity securities (including Preferred Stock) issued or outstanding.

Common Stock, Class A Units and Class B Units

Class A Units. The Company’s authorized Class A Units were initially issued for the contributions of the various members, which included capital, services and intellectual property. Additionally, certain members received Class A Units in accordance with anti-dilution provisions in the Company’s LLC agreement. In conjunction with the October 30, 2013 issuance of Series B Preferred Units, certain holders of Class A Units received an aggregate of 19,476 additional Class A Units as a result of the anti-dilution provisions. Upon the completion of the Series B Preferred Units issuance, all anti-dilution provisions had been fully utilized and were no longer outstanding.

Upon the Company’s conversion from an LLC to a C-corporation on September 16, 2014, the 132,148 of then issued and outstanding Class A Units were subject to a 50-to-1 reverse unit split, and converted into 2,643 shares of common stock.

Class B Units. In December 2009, the Company entered into the 2009 Equity Incentive Plan. Under the 2009 Equity Incentive Plan, which was administered by the Board of Managers, the Company was authorized to grant Class B Units. Class B Units were designed to provide equity incentive compensation to managers, employees, advisory board members and consultants of the Company, with such terms and conditions including vesting and forfeiture determined by the Board of Managers in its sole discretion. The Class B Units represented a profits interest in the Company as that term is defined in the Internal Revenue Code. The holders of Class B Units had no voting power and were only eligible for distributions resulting from a qualified liquidity event of the Company, as defined by the LLC agreement, and if the proceeds from such event exceed a fixed distribution threshold per unit. Distribution thresholds were determined by the Board of Managers for each Class B Unit awarded. In the case of a qualified public offering, as defined in the 2009 Equity Incentive Plan, the Class B Units would convert into shares of restricted common stock and continue to vest in accordance with each award agreement. The Class B Units were non-transferable and upon termination of service, the Company had the option to purchase all vested units from the award holder. The Company did not repurchase any Class B Units.

As of December 31, 2013, the Company had authorized up to 24,500 Class B Units for issuance, 22,828 of which were issued and subject to vesting conditions set forth in each Class B Unit award. Upon the Company’s conversion from an LLC to a C-corporation on September 16, 2014, all outstanding Class B Units were terminated along with the 2009 Equity Incentive Plan, and the Company executed the 2014 Stock Plan and granted stock options. Please refer to Note 10 for further information regarding the 2014 Stock Plan.

Management evaluated the Class B Unit awards and determined that they should be accounted for as a share-based payments in accordance with ASC 718. However, since no distribution is to be made to Class B Unit holders unless a qualified liquidity event occurs, management has determined that the awards are subject to both a service condition (vesting period) and a performance condition (qualified liquidity event). Additionally, the awards only convert into restricted common stock upon the event of a qualified public offering. Management did not consider a qualified liquidity event or public offering to be probable at any point during the outstanding terms of the Class B Units, and accordingly, no compensation expense was recorded in connection with the awards.

The Company accounted for the termination of the Class B Units and simultaneous grant of stock options under the 2014 Stock Plan as a modification to share-based payments under ASC 718. Since the performance conditions under the Class B Unit awards were deemed improbable of achievement, no incremental compensation cost from the modification was recognized. Please refer to Note 10 for information on stock-based compensation expense regarding stock options issued by the Company.

Common stock. As of December 31, 2014 and prior to the closing of the Company’s IPO on September 22, 2015, the dividend, liquidation and voting rights of the Company’s common stockholders were subject to, and qualified by, the rights, preferences and privileges of the holders of the outstanding Preferred Stock.

The Company’s reserved shares of common stock for future issuance are as follows:

	December 31,
	2015		2014
Series A convertible preferred stock		—		2,393
Series B convertible preferred stock		—		1,906
Reserved for issuance under equity incentive plans		5,998		2,500
Reserved for issuance under employee stock purchase plan		254		—
Debt with share settlement option (Note 6)		—		3,715
		6,252		10,514

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Paragraph 4
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Paragraph 2
-Subparagraph (SAB TOPIC 4.E)
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 505
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-Paragraph 5
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
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-Subparagraph (SX 210.3-04)
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
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-Publisher FASB
-Name Accounting Standards Codification
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Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

+ Details

Significant Agreements

12 Months Ended

Dec. 31, 2015

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Significant Agreements

9. Significant Agreements

Please refer to Note 13 for significant agreements with related parties and Note 7 for licenses granted to the Company.

Licenses Granted by the Company

The Company has granted a number of intellectual property licenses to other biotechnology and pharmaceutical companies. The terms of the licenses vary, however licenses may be exclusive or non-exclusive and may be sublicensable by the licensee. Licenses may grant intellectual property rights for purposes of internal and preclinical research and development only, or may include the rights, or options to obtain future rights, to commercialize drug therapies for specific diseases using the Company’s NAV® Technology. License agreements generally have a term equal to the life of the underlying patents and are terminable only at the option of the licensee. License agreements may require licensees to pay non-refundable up-front fees, option fees and annual maintenance fees. Additional contingent consideration under the licenses may include sublicense fees, milestone fees and royalties on net sales of commercialized products. Sublicense fees vary by license and range from a mid-single digit percentage to a low-double digit percentage of license fees received by licensees as a result of sublicenses. Royalties on net sales of commercialized products vary by license and range from a mid-single digit percentage to a low-teen percentage of net sales by licensees.

In July 2013, the Company granted an exclusive commercial license to Audentes. The license required an up-front fee of $600, $300 of which was payable in cash and the remainder in common stock of Audentes. As discussed in Note 2, the investment in Audentes is accounted for under the cost method. The carrying value of the equity investment in Audentes was $300 at December 31, 2015 and 2014, and is included in cost method investments on the balance sheets.

Milestone fees are payable to the Company upon the achievement of specific clinical and regulatory developments by licensees. As of December 31, 2015, the Company’s license agreements, excluding additional licenses that could be granted upon the exercise of options by licensees, could result in aggregate milestone fees payable to the Company of up to $500 upon the submission of preclinical regulatory filings, $16,650 upon the commencement of various stages of clinical trials, $28,000 upon the submission of regulatory approval filings, $73,500 upon the approval of commercial products by regulatory agencies and $47,000 upon the achievement of specified sales targets for licensed products.

License revenue, including amounts from related parties, consists of the following:

	Years Ended December 31,
	2015		2014		2013
Up-front fees and option fees for commercial licenses	$	5,900	$	4,000	$	3,400
Milestone fees for commercial licenses		250		—		—
Maintenance fees for commercial licenses		635		385		200
Research and other license revenue		240		190		155
	$	7,025	$	4,575	$	3,755

Grant Programs

MeuSIX. In December 2012, as part of a consortium of research and development entities called MeuSIX, the Company was awarded a long-term grant by the European Commission’s Seventh Framework Program, to perform preclinical and clinical research and development services for the treatment of MPS VI, a severe lysosomal storage disorder. Under the grant agreement, the Company is reimbursed by the grantor for 75 percent of qualified research and development costs, up to approximately €2,273 (approximately $2,859 based on the average conversion rate for the grant period to date through December 31, 2015) of such costs over the five year grant period. Funds received under the grant are subject to refund in the case of non-compliance with the provisions of the grant, which include, but are not limited to, the eligibility of costs, calculation of personnel rates, selection of subcontractors, and other provisions. As of December 31, 2015, the Company is in compliance with all provisions of the grants and no refunds are payable to the grantor. During the years ended December 31, 2015, 2014 and 2013, the Company incurred $912, $1,109 and $882, respectively, of research and development expenses under the grant program. The Company recorded grant revenue of $258, $832 and $661 related to the grant program for the years ended December 31, 2015, 2014 and 2013, respectively. As of December 31, 2015 and 2014, the Company had $534 and $865, respectively, of accounts receivable under the grant program, of which $0 and $320, respectively, is included in unbilled receivables on the balance sheets.

Federal Grants. The Company has received grant awards from agencies of the U.S. federal government to support critical research and development projects for the Company. In 2010, the Company was awarded two grants from the National Institute of Health (NIH) in amounts totaling $3,063. In 2012, the Company was awarded two additional grants from the NIH totaling $515. In 2013, the Company was awarded an additional grant from the NIH totaling $261. Funds received under the grants are subject to refund in the case of non-compliance with the provisions of the grant, which include, but are not limited to, the eligibility of costs, calculation of personnel rates, selection of subcontractors, and other provisions. As of December 31, 2015, the Company is in compliance with all provisions of the grants and no refunds are payable to the grantor. As a result of the NIH grants, the Company has recorded revenue from reimbursement of qualified research and development costs of $46, $387 and $1,303 for the years ended December 31, 2015, 2014 and 2013, respectively. As of December 31, 2014 the Company had $51 of accounts receivable under the NIH grants. As of January 2015, all NIH grants were completed and the Company has no amounts receivable under the grants as of December 31, 2015.

Stock-based Compensation

12 Months Ended

Dec. 31, 2015

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

10. Stock-based Compensation

Equity Incentive Plans

In September 2014, the Board of Directors adopted the 2014 Stock Plan (2014 Plan). As of December 31, 2014, the number of shares of common stock authorized for issuance under the 2014 Plan was 2,500.

In June 2015, the Company’s Board of Directors adopted the 2015 Equity Incentive Plan (2015 Plan), which became effective on September 16, 2015, the date on which the registration statement for the IPO was declared effective. The 2015 Plan replaced the 2014 Plan, and as of the effective date of the 2015 Plan, no further awards may be issued under the 2014 Plan. Any options or awards outstanding under the 2014 Plan at the effective date of the 2015 Plan remained outstanding and effective. The initial amount of shares authorized for issuance under the 2015 Plan was 2,952. The number of authorized shares under the 2015 Plan automatically increases annually on January 1, beginning January 1, 2016, by the lesser of (i) 4% of the total number of shares of common stock outstanding on December 31 of the prior year, or (ii) a number of common shares determined by the Board of Directors. As of December 31, 2015, the total number of shares of common stock authorized for issuance under the 2015 Plan and 2014 Plan is 6,125, of which 2,314 remain available for future grants under the 2015 Plan.

The 2014 Plan and 2015 Plan provide for the issuance of stock options, stock appreciation rights, restricted and unrestricted stock awards and performance cash awards to employees, members of the Board of Directors and consultants of the Company. No stock appreciation rights, restricted or unrestricted stock awards or performance cash awards have been granted under the 2014 Plan and 2015 Plan, since the inception of the plans. Stock options under the 2014 Plan and 2015 Plan generally expire ten years following the date of grant. Options typically vest over a four year period, but vesting provisions can vary by award based on the discretion of the Board of Directors. Certain awards issued by the Company include performance conditions that must be achieved in order for vesting to occur. Stock options under the 2014 Plan and 2015 Plan carry an exercise price at least equal to the estimated fair value of the Company’s common stock on the date of grant.

Shares of common stock underlying awards previously issued under the 2014 Plan and 2015 Plan which are reacquired by the Company, withheld by the Company in payment of the purchase price, exercise price or withholding taxes, expired, cancelled due to forfeiture or otherwise terminated other than by exercise, are added to the number of shares of common stock available for issuance under the 2015 Plan. Shares available for issuance under the 2015 Plan may be authorized but unissued shares of the Company’s common stock or common stock reacquired by the Company and held in treasury. The 2015 Plan expires in June 2025, ten years from the date it was adopted by the Board of Directors, unless earlier terminated.

The following table summarizes stock option activity under the Company’s equity incentive plans:

						Weighted-
						average
				Weighted-		Remaining
				average		Contractual		Aggregate
				Exercise		Life		Intrinsic
	Shares			Price		(Years)		Value (a)
Outstanding at December 31, 2013		—		$	—		—	$	—
Granted		2,132		$	0.85
Exercised		(2	)	$	0.85
Cancelled or forfeited		(23	)	$	0.85
Outstanding at December 31, 2014		2,107		$	0.85		9.8	$	379
Granted		1,727		$	10.80
Exercised		(125	)	$	0.85
Cancelled or forfeited		(25	)	$	1.19
Outstanding at December 31, 2015		3,684		$	5.52		9.1	$	44,472
Exercisable at December 31, 2015		1,328		$	1.45		8.8	$	20,194
Vested and expected to vest at December 31, 2015		3,684		$	5.52		9.1	$	44,472

(a)	The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money at the dates reported.

The weighted-average grant date fair value per share of options granted during the years ended December 31, 2015 and 2014 was $7.08 and $0.51, respectively. The weighted-average grant date fair value per share of options vested during the years ended December 31, 2015 and 2014 was $1.10 and $0.51, respectively. During the years ended December 31, 2015 and 2014, the total number of stock options exercised was 125 and 2, respectively, resulting in total proceeds of $107 and $1, respectively. The total intrinsic value of options exercised during the years ended December 31, 2015 and 2014 was $525 and $0, respectively. There were no stock options granted prior to the year ended December 31, 2014.

Stock-based compensation expense relates solely to stock options granted under the 2014 Plan and 2015 Plan. The Company has recorded aggregate stock-based compensation expense related to the issuance of stock option awards to employees and non-employees in the statement of operations and comprehensive loss as follows:

	Years Ended December 31,
	2015		2014
Research and development	$	1,760	$	60
General and administrative		1,161		259
	$	2,921	$	319

There were no stock options granted prior to the year ended December 31, 2014, and accordingly, no stock-based compensation expense was recorded for the year ended December 31, 2013.

Valuation of Common Stock. Prior to the Company’s IPO, the Company estimated the fair value of its common stock underlying stock option awards at the grant date of the award. Valuation estimates were prepared by management in accordance with the framework of the American Institute of Certified Public Accountants Practice Aid, Valuation of Privately-Held-Company Equity Securities Issued as Compensation, as well as through independent third-party valuations and were approved by the Company’s Board of Directors. Valuation estimates were based on a variety of factors including the Company’s financial position and historical financial performance, the Company’s stage of development, the valuations of comparable publicly traded companies, marketplace and macro-economic factors, the illiquid nature of the common stock, arm’s-length sales of the Company’s preferred equity securities, the effect of the rights, preferences and privileges of preferred shareholders and preferred unit holders and the prospects of a liquidity event, among others. After the completion of the Company’s IPO in September 2015, the fair value of the common stock is based on the closing price of the common stock on the date of grant.

Stock Options Granted to Employees. For the years ended December 31, 2015 and 2014, the Company recorded $1,443 and $299, respectively, of stock-based compensation expense related to employees’ stock options. The fair value of options granted to employees was estimated at the date of grant using the Black-Scholes valuation model with the following weighted-average assumptions:

	Years Ended December 31,
	2015			2014
Expected volatility		68	%		64	%
Expected term (in years)		6.1			6.0
Risk-free interest rate		1.7	%		2.0	%
Expected dividend yield		0.0	%		0.0	%

As of December 31, 2015, there was $11,133 of unrecognized stock-based compensation expense related to employees’ awards that is expected to be recognized over a weighted-average period of 3.48 years.

Stock Options Granted to Non-employees. Stock-based compensation expense related to stock options granted to non-employees is recognized as the stock options are earned. The Company believes that the estimated fair value of the stock options is more readily measurable than the fair value of the services rendered. For the years ended December 31, 2015 and 2014, the Company recorded $1,478 and $20, respectively, of stock-based compensation expense related to non-employees’ stock options. The Company used the following weighted-average assumptions in estimating non-employees’ stock-based compensation expense:

	Years Ended December 31,
	2015			2014
Expected volatility		75	%		65	%
Expected term (in years)		9.5			9.9
Risk-free interest rate		2.1	%		2.4	%
Expected dividend yield		0.0	%		0.0	%

Employee Stock Purchase Plan

In June 2015, the Company’s Board of Directors adopted the 2015 Employee Stock Purchase Plan (2015 ESPP), which became effective on September 16, 2015, the date on which the registration statement for the IPO was declared effective. The 2015 ESPP authorizes the initial issuance of up to a total of 254 shares of the Company’s common stock to participating employees. The number of shares reserved for issuance under the 2015 ESPP automatically increases on the first business day of each fiscal year, commencing in 2016, by a number equal to the lesser of (i) 1% of the shares of common stock outstanding on the last business day of the prior fiscal year; or (ii) the number of shares determined by the Company’s Board of Directors. Unless otherwise determined by the administrator of the 2015 ESPP, two offering periods of six months’ duration will begin each year on January 1 and July 1. As of December 31, 2015, there was no activity under the 2015 ESPP.

Retirement Plan	12 Months Ended
Retirement Plan	Dec. 31, 2015
Postemployment Benefits [Abstract]
Retirement Plan	11. Retirement Plan In February 2015, the Company established a defined-contribution retirement plan under Section 401(k) of the Internal Revenue Code (the 401(k) Plan). The 401(k) Plan covers all employees who meet defined minimum age and service requirements, and allows participants to defer a portion of their annual compensation. The Company matches employee deferrals up to 5.75 percent of eligible compensation. For the year ended December 31, 2015, the Company contributed $184 in matching contributions to the 401(k) Plan. As of December 31, 2014, the Company did not sponsor any retirement plans.

Income Taxes

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Income Taxes

12. Income Taxes

From inception through September 16, 2014, the Company was a Delaware LLC for federal and state income tax purposes, and therefore, all items of income or loss through September 16, 2014 flowed through to the members of the LLC. Effective September 16, 2014, the Company converted from an LLC to a C-corporation for federal and state income tax purposes. Prior to the conversion to a C-corporation, the Company did not record deferred tax assets or liabilities or have any net operating loss (NOL) carryforwards for federal income tax purposes. However, the Company had recorded a deferred tax asset for state income tax purposes, which consisted primarily of NOL carryforwards for state jurisdictions that did not recognize the Company’s LLC status.

Effective upon the conversion to a C-corporation, the Company became subject to income tax at the federal and state levels. Accordingly, as of December 31, 2015 and 2014 the Company recorded a deferred tax asset for federal and state income taxes.

As all of the Company’s income is generated in the U.S., and attributable to the U.S. jurisdiction, there are no foreign income tax expenses for the years ended December 31, 2015, 2014 and 2013.

The Company did not record a current or deferred income tax expense or benefit for the years ended December 31, 2015, 2014 and 2013. Since the Company was an LLC for the year ended December 31, 2013, the Company was not subject to federal income tax. A reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate of 34 percent to income tax expense (benefit) as reflected in the financial statements is as follows:

	Years Ended December 31,
	2015			2014			2013
Federal income tax benefit at statutory rate	$	(7,756	)	$	(1,089	)	$	—
State income tax benefit, net of federal benefit		(1,511	)		(264	)		(537	)
Change in income tax rates upon conversion to C-corporation		—			427			—
Federal deferred tax assets upon conversion to C-corporation		—			(105	)		—
Step-up in assets upon conversion to C-corporation		(709	)		(448	)		—
Stock-based compensation expense for incentive stock options		283			98			—
Imputed interest on related party promissory notes		—			52			—
Taxable gain upon conversion to C-corporation		—			73			—
Other non-deductible expenses and reconciling items		240			4			—
Change in valuation allowance		9,453			1,252			537
Total income tax expense (benefit)	$	—		$	—		$	—

The significant components of the Company’s deferred tax assets are as follows:

	December 31,
	2015			2014
Deferred tax assets:
Net operating loss carryforwards	$	9,254		$	1,844
Step-up in assets upon conversion to C-corporation		1,046			438
Stock-based compensation expense for non-qualified stock options		855			31
Unrealized losses on marketable securities		284			—
Deferred rent		97			—
Accruals and other		568			42
Total deferred tax assets before valuation allowance		12,104			2,355
Valuation allowance		(12,093	)		(2,355	)
Total deferred tax assets		11			—
Deferred tax liabilities:
Depreciation		(11	)		—
Total deferred tax liabilities		(11	)		—
Net deferred tax assets	$	—		$	—

The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets. Based on the Company’s history of operating losses, the Company has concluded that it is more likely than not that the benefit of its deferred tax assets will not be realized. Accordingly, the Company has provided a full valuation allowance for its net deferred tax assets as of December 31, 2015 and 2014. The valuation allowance increased approximately $9,453 and $1,252 during the years ended December 31, 2015 and 2014, respectively, due primarily to the conversion to a C-corporation and the federal and state net operating losses generated during the periods.

As of December 31, 2015 and 2014, the Company had U.S. federal NOL carryforwards of approximately $21,215 and $2,979, respectively, which may be available to offset future income tax liabilities and expire at various dates through 2035. As of December 31, 2015 and 2014, the Company also had U.S. state NOL carryforwards of approximately $34,199 and $13,406, respectively, which may be available to offset future income tax liabilities and expire at various dates through 2035.

Under the provisions of the Internal Revenue Code, the NOL carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. NOL carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50 percent, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has completed several financings since its inception which may have resulted in a change in control as defined by Sections 382 and 383 of the Internal Revenue Code, or could result in a change in control in the future.

The Company files income tax returns in the U.S. at the federal level and in states in which the Company conducts business activities. The federal and state income tax returns are generally subject to tax examinations for the tax years ended December 31, 2012 through December 31, 2015. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service or state tax authorities to the extent utilized in a future period.

Related Party Transactions

12 Months Ended

Dec. 31, 2015

Related Party Transactions

13. Related Party Transactions

The Trustees of the University of Pennsylvania

Penn is a stockholder of the Company as a result of the intellectual property license granted to the Company in February 2009, and prior to September 30, 2015 the Company considered Penn to be a related party. See Note 7 for further information, including costs incurred by the Company, regarding its license from Penn.

As a result of various factors, including the dilution to the Company’s stockholders resulting from the sale and issuance of Series C Preferred Stock and Series D Preferred Stock, and the closing of the Company’s IPO on September 22, 2015, the Company no longer considers Penn to be a related party subsequent to the period ended September 30, 2015.

In addition to the license agreement, Penn also provides manufacturing and research and development services to the Company. Expenses incurred by the Company for manufacturing and research and development for the nine months ended September 30, 2015 and the years ended December 31, 2014 and 2013 are as follows:

	Nine Months Ended		Years Ended
	September 30,		December 31,
	2015		2014		2013
Manufacturing of reagents for sale	$	80	$	92	$	143
Research and development services		5,136		1,286		2,778
	$	5,216	$	1,378	$	2,921

As of December 31, 2014, the Company had accrued $677 in manufacturing and research and development costs to Penn which are included in other related party payables on the balance sheets.

GlaxoSmithKline LLC

GSK is a stockholder of the Company as a result of the intellectual property license granted to the Company in March 2009, and prior to September 30, 2015 the Company considered GSK to be a related party. See Note 7 for further information, including costs incurred by the Company, regarding its license from GSK.

As a result of various factors, including the dilution to the Company’s stockholders resulting from the sale and issuance of Series C Preferred Stock and Series D Preferred Stock, and the closing of the Company’s IPO on September 22, 2015, the Company no longer considers GSK to be a related party subsequent to the period ended September 30, 2015.

Dimension Therapeutics, Inc.

The Company and a number of its members, directors and management received common stock of Dimension as consideration for a license granted to Dimension in October 2013. Additionally, at the date of the license three of the Company’s board members also served on the board of directors of Dimension. As a result, prior to September 30, 2015 the Company considered Dimension to be a related party.

As of September 30, 2015, the Company no longer had any overlapping board members with Dimension. Additionally, the Company’s directors and management do not have significant influence over Dimension. Accordingly, the Company no longer considers Dimension to be a related party subsequent to the period ended September 30, 2015.

On October 30, 2013, the Company granted an exclusive, sublicensable, worldwide commercial license to Dimension for preclinical and clinical research and development and commercialization of drug therapies using the Company’s licensed patents for the treatment of hemophilia A and hemophilia B, as well as a one year option to obtain exclusive licenses for the commercialization of two other diseases to be elected by Dimension in the future. The agreement requires on-going annual maintenance fees of $35, for each indication elected by Dimension, beginning in October 2014. The agreement also requires Dimension to pay royalties on net sales, if any, to the Company at an amount intended to approximate the royalties that will be due by the Company to Penn and GSK on such sales. In consideration for the license granted, Dimension issued the Company, and various members, directors and executives of the Company, an aggregate total of 10,000 shares of its common stock with an estimated fair value of $2,700. The Company recorded $2,700 as revenue upon delivery of the license. Of the 10,000 shares, a total of 10 shares were issued to the Company, with an estimated fair value of $3, which is included in cost method investments on the balance sheet as of December 31, 2014. As of the December 31, 2015 the investment in Dimension is included in marketable securities on the balance sheet as Dimension completed its IPO in October 2015 and the shares are now marketable. In consideration for the efforts by the various members, directors and executives of the Company which were responsible for executing the license agreement with Dimension, the Company recorded expenses equal to the estimated fair value of the 9,990 shares of common stock of Dimension received by those parties of $2,697, which is included in general and administrative expenses in the statements of operations and comprehensive loss for the year ended December 31, 2013. In accordance with its revenue recognition policy, the Company has determined that the $2,700 in revenue from the license granted to Dimension should be recognized in full upon the delivery of the license, as the Company has no further significant performance obligations under the agreement. Additionally, the Company determined that the $2,697 of general and administrative expenses to related parties should be recognized in full upon the execution of the agreement with Dimension, as those parties have no further performance obligations to the Company.

In addition to related parties of the Company holding common stock in Dimension as a result of the license agreement noted above, three of the Company’s board members served on the board of directors of Dimension on the effective the date of the license. Management evaluated the consolidation guidance under ASC 810 and determined that Dimension was considered a VIE on the date of the license and as of December 31, 2014, however, it did not consolidate Dimension because it lacked the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance. The carrying amount of the investment in Dimension as of December 31, 2014 was $3 and receivables due from Dimension as of December 31, 2014 were $750. As a result of capital raised by Dimension in its IPO in October 2015, the Company no longer considers Dimension to be a VIE as of December 31, 2015.

In connection with the license agreement granted to Dimension, the Company entered into an arrangement with Penn and Dimension in which the Company helped coordinate and manage research and development activities performed by Penn on behalf of Dimension. Under the arrangement, Dimension reimbursed the Company at an amount equal to costs incurred and paid to Penn, and the Company retains rights to certain intellectual property discovered under the contracted research and development. Due to the uncertainty of any future intellectual property rights that may be discovered and retained by the Company, and because such intellectual property would have no future alternative use due to the stage of development of the drug therapies under development, the Company has not recognized any benefit from the arrangement as consideration paid by Dimension to the Company as a result of the license agreement. Management has evaluated the facts and circumstances of the arrangements with regards to ASC 605-45 Revenue Recognition-Principal Agent Considerations and determined that the proceeds received from Dimension should be recorded on a net basis. Accordingly, proceeds received from Dimension under the arrangement were recorded as a reduction of research and development expense in the statements of operations and comprehensive loss. For the years ended December 31, 2014 and 2013, the Company recorded research and development expense to Penn, and related reimbursements from Dimension of $6,177 and $924, respectively, for a net cost of $0 for each period. As of December 31, 2014, the Company had recorded a related party payable of $750 to Penn and a related party receivable of $750 from Dimension under the arrangement. The arrangement expired on December 31, 2014 and as of December 31, 2015 the final payments under this arrangement were received by the Company and paid to Penn, and the arrangement has ended.

In September 2014, Dimension elected its third indication under the license agreement, and the license was amended to extend the term of the option to elect the fourth and final disease indication for an additional six months. In consideration for the extension of the option, Dimension paid an extension fee of $150. In January 2015, Dimension elected its fourth and final indication under the license.

In March 2015, the Company entered into an option and license agreement with Dimension that grants Dimension options to commercial exclusive licenses for four new disease indications to be elected by Dimension in the future. If elected, each option carries an option fee of $1,000 payable to the Company upon exercise, and annual maintenance fees of $50. Additionally, for each option exercised, Dimension is obligated to pay the Company up to $9,000 upon achievement of various substantive milestones, as well as mid to upper-single digit percentage royalties on net sales of licensed products and mid-single digit to low-double digit percentage sublicense fees, if any. In May 2015, Dimension exercised its first option under the agreement and paid $1,000 to the Company. In August 2015, Dimension exercised its second option under the agreement and paid $1,000 to the Company. In December 2015, Dimension exercised its third option under the agreement and paid $1,000 to the Company.

During the nine months ended September 30, 2015, and the years ended 2014 and 2013, the Company recognized $2,000, $220 and $2,700, respectively, in license revenue from license agreements with Dimension which is included in license revenue from related party in the statements of operations and comprehensive loss. License revenue recognized from Dimension subsequent to September 30, 2015 is no longer included in license revenue from related party in the statements of operations and comprehensive loss.

During the year ended December 31, 2014, the Company received $200 from Dimension for the purchase of materials owned by the Company and used in the Company’s manufacturing process for research and development and clinical trials. The $200 is recognized as a gain on disposal of the material as the material is delivered to Dimension. For the years ended December 31, 2015 and 2014, the Company recognized gains of $26 and $47, respectively, related to the delivery of purchased material. Gains resulting from the delivery of the purchased material to Dimension is included in other operating income in the statements of operations. As of December 31, 2015 and 2014, the Company recorded an advance payment liability of $127 and $153, respectively, for proceeds received for undelivered material.

FoxKiser

The Company was party to a services agreement, as amended from time to time, with FoxKiser, an affiliate of certain stockholders of the Company and affiliate of one current and one former member of the Board of Directors, which was terminated in January 2015. Under the agreement, the Company paid a fixed monthly fee plus an additional support fee, as determined by FoxKiser on a monthly basis, as consideration for office facilities, equipment, supplies, general management, accounting, financial management, human resources, legal, secretarial, regulatory compliance and other services provided to the Company. The amounts outstanding to FoxKiser under the services agreement in excess of 30 days from their due date accrued interest at 1.5 percent per month, compounding monthly. The Company allocated the service fees from FoxKiser between research and development and general and administrative expense. Costs incurred by the Company under the services agreement with FoxKiser were as follows:

	Years Ended December 31,
	2015		2014		2013
Research and development	$	168	$	1,283	$	1,111
General and administrative		237		1,696		1,469
	$	405	$	2,979	$	2,580

As of December 31, 2014, the Company had recorded $1,423 payable to FoxKiser under the services agreement. As discussed in Note 6, amounts owed under the services agreement were converted into Series C Preferred Stock on January 13, 2015. In January 2015, the services agreement was terminated and the remaining amounts due to the FoxKiser under the agreement were paid in full in cash. The Company also entered into promissory notes with FoxKiser as discussed in Note 6.

The Company entered into a Professional Services Agreement with FoxKiser effective as of January 1, 2016, pursuant to which the Company incurs a fixed monthly fee of $80 in consideration for certain strategic planning, development and regulatory services to be provided by FoxKiser. The Professional Services Agreement has an initial term of one year and is terminable by either party, at any time, upon sixty days prior written notice to the other party.

Chief Scientific Advisor

In September 2014, the Company entered into an advisory agreement with its Chief Scientific Advisor, who is also the Chairman of the Company’s Scientific Advisory Board. The agreement was amended in May 2015 and expires in March 2017. During the years ended December 31, 2015 and 2014, the Company incurred advisory fees of $180 and $45, respectively, to the Chief Scientific Advisor under the agreement. Additionally, the Company granted 70 and 142 options to purchase common stock to the Chief Scientific Advisor during the years ended December 31, 2015 and 2014, respectively, as compensation for services to be provided to the Company, which vest partially upon the completion of future service conditions, and partially upon the achievement of specified performance conditions as set forth in the award agreements.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

Net Loss Per Share

12 Months Ended

Dec. 31, 2015

Earnings Per Share [Abstract]

Net Loss Per Share

14. Net Loss Per Share

The following potentially dilutive securities outstanding at the end of the period were excluded from the computations of diluted weighted-average shares outstanding for the periods indicated as they would be anti-dilutive:

	Years Ended December 31,
	2015		2014		2013
Series A convertible preferred stock and preferred units		—		2,393		2,393
Series B convertible preferred stock and preferred units		—		1,906		1,906
Stock options issued and outstanding		3,684		2,107		—
Debt with share settlement option (Note 6)		—		3,715		—
		3,684		10,121		4,299

Amounts in the table above reflect the common stock equivalents of the noted instruments.

Supplemental Disclosures

12 Months Ended

Dec. 31, 2015

Payables And Accruals [Abstract]

Supplemental Disclosures

15. Supplemental Disclosures

Accrued expenses and other current liabilities consists of the following:

	As of December 31,
	2015		2014
Accrued personnel costs	$	1,371	$	—
Accrued external research and development		791		781
Accrued sublicense fees and royalties on reagent sales		260		—
Other accrued expenses and current liabilities		776		334
	$	3,198	$	1,115

Accrued external research and development, accrued sublicense fees and royalties on reagent sales and other accrued expenses to Penn and GSK as of December 31, 2014 were included in related party payables on the Company’s balance sheet. Subsequent to September 30, 2015, neither party is considered to be a related party of the Company. See Note 13 for further information on related party transactions with Penn and GSK prior to September 30, 2015.

Selected Quarterly Financial Information (Unaudited)

12 Months Ended

Dec. 31, 2015

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Information (Unaudited)

16. Selected Quarterly Financial Information (Unaudited)

The following table contains quarterly financial information for 2015 and 2014. Management believes that the following information reflects all normal recurring adjustments necessary for a fair statement of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period. Amounts in the following table are in thousands, except per share data.

	Quarters Ended
	March 31, 2015			June 30, 2015			September 30, 2015			December 31, 2015
Total revenues	$	644		$	1,363		$	1,140		$	4,441
Total operating expenses	$	4,637		$	7,659		$	8,487		$	9,942
Net loss	$	(4,011	)	$	(6,290	)	$	(7,332	)	$	(5,178	)
Basic and diluted net loss per common share	$	(0.94	)	$	(3.24	)	$	(1.52	)	$	(0.20	)

	Quarters Ended
	March 31, 2014		June 30, 2014			September 30, 2014			December 31, 2014
Total revenues	$	2,937	$	1,549		$	483		$	1,151
Total operating expenses	$	2,102	$	2,150		$	2,184		$	3,366
Net income (loss)	$	795	$	(672	)	$	(1,793	)	$	(2,333	)
Basic and diluted net income (loss) per common share	$	0.08	$	(0.34	)	$	(0.73	)	$	(0.97	)

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Subsequent Events

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Basis of Presentation

Foreign Currency Transactions

Use of Estimates

Segment and Geographical Information

Cash and Cash Equivalents

Marketable Securities

Concentrations of Credit Risk and Off-balance Sheet Risk

The following table summarizes those customers who represented at least 10 percent of revenue or accounts receivable for the periods presented:

	Revenue									Accounts Receivable
	Years Ended December 31,									December 31,
	2015			2014			2013			2015			2014
Customer A	*				33	%	*			*			*
Customer B	*				14	%		11	%		25	%		46	%
Customer C⁽¹⁾		41	%	*				44	%	*				40	%
Customer D	*			*			*			*				11	%
Customer E	*			*				21	%	*			*
Customer F		16	%	*			*				42	%	*
Customer G		22	%	*			*				19	%	*

*	Represented less than 10%

(1)	Represents a related party prior to September 30, 2015

Accounts Receivable

Deferred Issuance Costs

Property and Equipment


Computer equipment and software			3 years
Lab equipment			5 years
Furniture and fixtures			5 years
Leasehold improvements			Shorter of lease term or estimated useful life

Impairment of Long-lived Assets

Cost Method Investments

Related Party Debt Instruments

Fair Value of Financial Instruments

Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable.

Convertible Preferred Stock and Preferred Units

Revenue Recognition

Persuasive evidence of an arrangement exists;

Delivery has occurred or services have been rendered;

The seller’s price to the buyer is fixed or determinable; and

Collectability is reasonably assured.

Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s balance sheets.

Please refer to Note 13 for information regarding license revenue from related party.

Research and Development Expense

Research and Development Expenses

Share-based Compensation

Stock-based Compensation

Income Taxes

Net Loss Per Share

Comprehensive Loss

The Company’s comprehensive loss includes its net loss as well as net unrealized losses on available-for-sale securities.

Recently Announced Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Schedule of Revenue or Accounts Receivable by Major Customers

The following table summarizes those customers who represented at least 10 percent of revenue or accounts receivable for the periods presented:

	Revenue									Accounts Receivable
	Years Ended December 31,									December 31,
	2015			2014			2013			2015			2014
Customer A	*				33	%	*			*			*
Customer B	*				14	%		11	%		25	%		46	%
Customer C⁽¹⁾		41	%	*				44	%	*				40	%
Customer D	*			*			*			*				11	%
Customer E	*			*				21	%	*			*
Customer F		16	%	*			*				42	%	*
Customer G		22	%	*			*				19	%	*

*	Represented less than 10%

(1)	Represents a related party prior to September 30, 2015

Summary of Estimated Useful Lives of Assets

Depreciation and amortization is calculated using the straight-line method over the estimated useful lives of the assets, which are as follows:


Computer equipment and software			3 years
Lab equipment			5 years
Furniture and fixtures			5 years
Leasehold improvements			Shorter of lease term or estimated useful life

Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2015

Investments Debt And Equity Securities [Abstract]

Summary of Company Marketable Securities

The following table presents a summary of the Company’s marketable securities, which consist solely of available-for-sale securities:

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2015
Corporate bonds	$	157,977	$	4	$	(759	)	$	157,222
Commercial paper		4,990		—		—			4,990
Common equity securities		3		36		—			39
	$	162,970	$	40	$	(759	)	$	162,251

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Schedule of Fair Value of Cash Equivalents and Marketable Securities

The following tables present the fair value of cash equivalents and marketable securities in accordance with the hierarchy discussed in Note 2:

	Quoted		Significant
	prices		other		Significant
	in active		observable		unobservable
	markets		inputs		inputs
	(Level 1)		(Level 2)		(Level 3)		Total
December 31, 2015
Money market mutual funds (cash equivalents)	$	—	$	54,104	$	—	$	54,104
Corporate bonds (marketable securities)		—		157,222		—		157,222
Commercial paper (marketable securities)		—		4,990		—		4,990
Common equity securities (marketable securities)		39		—		—		39
	$	39	$	216,316	$	—	$	216,355

	Quoted		Significant
	prices		other		Significant
	in active		observable		unobservable
	markets		inputs		inputs
	(Level 1)		(Level 2)		(Level 3)		Total
December 31, 2014
Money market mutual funds (cash equivalents)	$	—	$	844	$	—	$	844
	$	—	$	844	$	—	$	844

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2015

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment

Property and equipment, net consists of the following:

	December 31,
	2015
Computer equipment and software	$	458
Furniture and fixtures		105
Leasehold improvements		55
Total property and equipment		618
Accumulated depreciation and amortization		(80	)
Property and equipment, net	$	538

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2015

Schedule of Future Minimum Lease Payments Under Non-Cancelable Operating Leases

As of December 31, 2015, future minimum lease payments under non-cancelable operating leases are as follows:

	Operating
	Leases
2016	$	777
2017		824
2018		848
2019		874
2020		832
Thereafter		144
Total minimum lease payments	$	4,299

The Trustees of the University of Pennsylvania [Member]

Summary of Expenses Incurred by Company

Expenses incurred by the Company related to its license from Penn were as follows:

	Years Ended December 31,
	2015		2014		2013
Sublicense fees	$	703	$	443	$	76
Royalties on sales of reagents		9		17		18
Maintenance of licensed patents		154		256		120
	$	866	$	716	$	214

GlaxoSmithKline LLC [Member]

Summary of Expenses Incurred by Company

Expenses incurred by the Company related to its license from GSK were as follows:

	Years Ended December 31,
	2015		2014		2013
Sublicense fees	$	703	$	443	$	76
Royalties on sales of reagents		5		10		11
Maintenance of licensed patents		573		432		455
	$	1,281	$	885	$	542

Capitalization (Tables)

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Schedule of Reserved Shares of Common Stock for Future Issuance

The Company’s reserved shares of common stock for future issuance are as follows:

	December 31,
	2015		2014
Series A convertible preferred stock		—		2,393
Series B convertible preferred stock		—		1,906
Reserved for issuance under equity incentive plans		5,998		2,500
Reserved for issuance under employee stock purchase plan		254		—
Debt with share settlement option (Note 6)		—		3,715
		6,252		10,514

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=27011957&loc=d3e177068-122764

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21553-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6403732&loc=d3e21300-112643

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.28,29)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 30
-Article 5

+ Details

Significant Agreements (Tables)

12 Months Ended

Dec. 31, 2015

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of License Revenue

License revenue, including amounts from related parties, consists of the following:

	Years Ended December 31,
	2015		2014		2013
Up-front fees and option fees for commercial licenses	$	5,900	$	4,000	$	3,400
Milestone fees for commercial licenses		250		—		—
Maintenance fees for commercial licenses		635		385		200
Research and other license revenue		240		190		155
	$	7,025	$	4,575	$	3,755

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Stock-Based Compensation Expense Related to Issuance of Stock Option Awards to Employees and Non-employees

The Company has recorded aggregate stock-based compensation expense related to the issuance of stock option awards to employees and non-employees in the statement of operations and comprehensive loss as follows:

	Years Ended December 31,
	2015		2014
Research and development	$	1,760	$	60
General and administrative		1,161		259
	$	2,921	$	319

Schedule of Fair Value of Options Granted to Employees Valuation Assumptions

The fair value of options granted to employees was estimated at the date of grant using the Black-Scholes valuation model with the following weighted-average assumptions:

	Years Ended December 31,
	2015			2014
Expected volatility		68	%		64	%
Expected term (in years)		6.1			6.0
Risk-free interest rate		1.7	%		2.0	%
Expected dividend yield		0.0	%		0.0	%

Non Employee Stock Option [Member]

Schedule of Non-Employees Stock Purchase Plan Valuation Assumptions

The Company used the following weighted-average assumptions in estimating non-employees’ stock-based compensation expense:

	Years Ended December 31,
	2015			2014
Expected volatility		75	%		65	%
Expected term (in years)		9.5			9.9
Risk-free interest rate		2.1	%		2.4	%
Expected dividend yield		0.0	%		0.0	%

2015 Equity Incentive Plan [Member]

Summary of Stock Option Activity

The following table summarizes stock option activity under the Company’s equity incentive plans:

						Weighted-
						average
				Weighted-		Remaining
				average		Contractual		Aggregate
				Exercise		Life		Intrinsic
	Shares			Price		(Years)		Value (a)
Outstanding at December 31, 2013		—		$	—		—	$	—
Granted		2,132		$	0.85
Exercised		(2	)	$	0.85
Cancelled or forfeited		(23	)	$	0.85
Outstanding at December 31, 2014		2,107		$	0.85		9.8	$	379
Granted		1,727		$	10.80
Exercised		(125	)	$	0.85
Cancelled or forfeited		(25	)	$	1.19
Outstanding at December 31, 2015		3,684		$	5.52		9.1	$	44,472
Exercisable at December 31, 2015		1,328		$	1.45		8.8	$	20,194
Vested and expected to vest at December 31, 2015		3,684		$	5.52		9.1	$	44,472

(a)	The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money at the dates reported.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of Effective Income Tax Expense (Benefit)

A reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate of 34 percent to income tax expense (benefit) as reflected in the financial statements is as follows:

	Years Ended December 31,
	2015			2014			2013
Federal income tax benefit at statutory rate	$	(7,756	)	$	(1,089	)	$	—
State income tax benefit, net of federal benefit		(1,511	)		(264	)		(537	)
Change in income tax rates upon conversion to C-corporation		—			427			—
Federal deferred tax assets upon conversion to C-corporation		—			(105	)		—
Step-up in assets upon conversion to C-corporation		(709	)		(448	)		—
Stock-based compensation expense for incentive stock options		283			98			—
Imputed interest on related party promissory notes		—			52			—
Taxable gain upon conversion to C-corporation		—			73			—
Other non-deductible expenses and reconciling items		240			4			—
Change in valuation allowance		9,453			1,252			537
Total income tax expense (benefit)	$	—		$	—		$	—

Components of Deferred Tax Assets

The significant components of the Company’s deferred tax assets are as follows:

	December 31,
	2015			2014
Deferred tax assets:
Net operating loss carryforwards	$	9,254		$	1,844
Step-up in assets upon conversion to C-corporation		1,046			438
Stock-based compensation expense for non-qualified stock options		855			31
Unrealized losses on marketable securities		284			—
Deferred rent		97			—
Accruals and other		568			42
Total deferred tax assets before valuation allowance		12,104			2,355
Valuation allowance		(12,093	)		(2,355	)
Total deferred tax assets		11			—
Deferred tax liabilities:
Depreciation		(11	)		—
Total deferred tax liabilities		(11	)		—
Net deferred tax assets	$	—		$	—

Related Party Transactions (Tables)

12 Months Ended

Dec. 31, 2015

The Trustees of the University of Pennsylvania [Member]

Summary of Expenses Incurred for Manufacturing and Research and Development

Expenses incurred by the Company for manufacturing and research and development for the nine months ended September 30, 2015 and the years ended December 31, 2014 and 2013 are as follows:

	Nine Months Ended		Years Ended
	September 30,		December 31,
	2015		2014		2013
Manufacturing of reagents for sale	$	80	$	92	$	143
Research and development services		5,136		1,286		2,778
	$	5,216	$	1,378	$	2,921

Summary of Expenses Incurred by Company

Expenses incurred by the Company related to its license from Penn were as follows:

	Years Ended December 31,
	2015		2014		2013
Sublicense fees	$	703	$	443	$	76
Royalties on sales of reagents		9		17		18
Maintenance of licensed patents		154		256		120
	$	866	$	716	$	214

FoxKiser,LLP [Member]

Summary of Expenses Incurred by Company

Costs incurred by the Company under the services agreement with FoxKiser were as follows:

	Years Ended December 31,
	2015		2014		2013
Research and development	$	168	$	1,283	$	1,111
General and administrative		237		1,696		1,469
	$	405	$	2,979	$	2,580

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2015

Earnings Per Share [Abstract]

Schedules for Computation of Diluted Weighted-Average Shares Outstanding

	Years Ended December 31,
	2015		2014		2013
Series A convertible preferred stock and preferred units		—		2,393		2,393
Series B convertible preferred stock and preferred units		—		1,906		1,906
Stock options issued and outstanding		3,684		2,107		—
Debt with share settlement option (Note 6)		—		3,715		—
		3,684		10,121		4,299

Supplemental Disclosures (Tables)

12 Months Ended

Dec. 31, 2015

Payables And Accruals [Abstract]

Schedules of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consists of the following:

	As of December 31,
	2015		2014
Accrued personnel costs	$	1,371	$	—
Accrued external research and development		791		781
Accrued sublicense fees and royalties on reagent sales		260		—
Other accrued expenses and current liabilities		776		334
	$	3,198	$	1,115

Selected Quarterly Financial Information (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2015

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Information

	Quarters Ended
	March 31, 2015			June 30, 2015			September 30, 2015			December 31, 2015
Total revenues	$	644		$	1,363		$	1,140		$	4,441
Total operating expenses	$	4,637		$	7,659		$	8,487		$	9,942
Net loss	$	(4,011	)	$	(6,290	)	$	(7,332	)	$	(5,178	)
Basic and diluted net loss per common share	$	(0.94	)	$	(3.24	)	$	(1.52	)	$	(0.20	)

	Quarters Ended
	March 31, 2014		June 30, 2014			September 30, 2014			December 31, 2014
Total revenues	$	2,937	$	1,549		$	483		$	1,151
Total operating expenses	$	2,102	$	2,150		$	2,184		$	3,366
Net income (loss)	$	795	$	(672	)	$	(1,793	)	$	(2,333	)
Basic and diluted net income (loss) per common share	$	0.08	$	(0.34	)	$	(0.73	)	$	(0.97	)

Nature of Business - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
	Sep. 22, 2015	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Accumulated deficit		$ (51,620)	$ (28,809)
Cash, cash equivalents and marketable securities		$ 216,367
Common Stock [Member]
Class of Stock [Line Items]
Issuance of convertible preferred stock, shares		7,245
Conversion of convertible preferred stock into common stock upon initial public offering, Shares	16,298	16,298
Initial Public Offering [Member]
Class of Stock [Line Items]
Issuance of convertible preferred stock, shares	7,245
Stock issuance price per share	$ 22.00
Initial Public Offering [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Net proceeds from issuance of common stock	$ 145,184
Overallotment Option [Member]
Class of Stock [Line Items]
Issuance of convertible preferred stock, shares	945

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) Segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Significant Accounting Policies [Line Items]
Number of operating segments \| Segment	1
Allowance for doubtful accounts receivable	$ 0	$ 0
Deferred offering costs	0	157,000
Impairment losses	0	0	$ 0
Cost method investments	300,000	303,000
Other-than-temporary impairment losses	0	0	$ 0
Accrued interest or penalties related to uncertain tax positions	0	0
Unrecognized tax benefits	$ 0	$ 0
Customer Concentration Risk [Member] \| United States [Member] \| Revenue [Member]
Significant Accounting Policies [Line Items]
Concentration risk percentage	78.00%	60.00%	86.00%
Customer Concentration Risk [Member] \| Europe [Member] \| Revenue [Member]
Significant Accounting Policies [Line Items]
Concentration risk percentage	21.00%	40.00%	13.00%

Summary of Significant Accounting Policies - Schedule of Revenue or Accounts Receivable by Major Customers (Detail) - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Customer A [Member] \| Revenue [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage		33.00%
Customer B \| Revenue [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage		14.00%	11.00%
Customer B \| Accounts Receivable [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	25.00%	46.00%
Customer C \| Revenue [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	41.00%		44.00%
Customer C \| Accounts Receivable [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage		40.00%
Customer D \| Accounts Receivable [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage		11.00%
Customer E \| Revenue [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage			21.00%
Customer F \| Revenue [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	16.00%
Customer F \| Accounts Receivable [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	42.00%
Customer G \| Revenue [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	22.00%
Customer G \| Accounts Receivable [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk percentage	19.00%

Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Assets (Detail)	12 Months Ended
	Dec. 31, 2015
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Property plant and equipment estimated useful lives	3 years
Lab equipment [Member]
Property Plant And Equipment [Line Items]
Property plant and equipment estimated useful lives	5 years
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Property plant and equipment estimated useful lives	5 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property plant and equipment estimated useful lives	Shorter of lease term or estimated useful life

Marketable Securities - Summary of Company Marketable Securities (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 162,970,000
Unrealized Gains	40,000
Unrealized Losses	(759,000)
Fair Value	162,251,000	$ 0
Common Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	3,000
Unrealized Gains	36,000
Fair Value	39,000
Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	157,977,000
Unrealized Gains	4,000
Unrealized Losses	(759,000)
Fair Value	157,222,000
Commercial Paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	4,990,000
Fair Value	$ 4,990,000

Marketable Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Unrealized loss on available-for-sale securities	$ (719,000)
Available for sale securities remaining maturities greater than three years	0
Available for sale securities	162,251,000	$ 0
Realized gains or losses available for sale securities	0
Aggregate fair value of securities in an unrealized loss position for less than twelve months	155,486,000
Other-than-temporary impaired	0
Common Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Unrealized loss on available-for-sale securities	36,000
Available for sale securities	$ 39,000

Fair Value of Financial Instruments - Schedule of Fair Value of Cash Equivalents and Marketable Securities (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Available for sale securities	$ 162,251,000	$ 0
Assets fair value disclosure	216,355,000	844,000
Common Equity Securities [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Available for sale securities	39,000
Corporate Bonds [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Available for sale securities	157,222,000
Commercial Paper [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Available for sale securities	4,990,000
Money Market Mutual Funds [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Money market mutual funds (cash equivalents)	54,104,000	844,000
Quoted Prices in Active Markets (Level 1) [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Assets fair value disclosure	39,000
Quoted Prices in Active Markets (Level 1) [Member] \| Common Equity Securities [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Available for sale securities	39,000
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Assets fair value disclosure	216,316,000	844,000
Significant Other Observable Inputs (Level 2) [Member] \| Corporate Bonds [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Available for sale securities	157,222,000
Significant Other Observable Inputs (Level 2) [Member] \| Commercial Paper [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Available for sale securities	4,990,000
Significant Other Observable Inputs (Level 2) [Member] \| Money Market Mutual Funds [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Money market mutual funds (cash equivalents)	$ 54,104,000	$ 844,000

Property and Equipment Net - Schedule of Property and Equipment (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Line Items]
Total property and equipment	$ 618,000
Accumulated depreciation and amortization	(80,000)
Property and equipment, net	538,000	$ 0
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	458,000
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	105,000
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	$ 55,000

Property and Equipment Net - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property Plant And Equipment [Abstract]
Property and equipment, net	$ 538,000	$ 0
Depreciation or amortization expense	$ 80,000	$ 0	$ 0

Related Party Debt Instruments - Additional Information (Detail) - USD ($)			12 Months Ended
	Jan. 13, 2015	Oct. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Sep. 15, 2014	Jul. 31, 2014	Sep. 30, 2013
Related Party Transaction [Line Items]
Preferred stock, par value			$ 0.0001	$ 0.0001
Due to related party under services agreement				$ 1,423,000
Interest expense			$ 20,000	321,000	$ 611,000
Series B Preferred Stock [Member]
Related Party Transaction [Line Items]
Issuance of convertible preferred stock for the conversion of outstanding related party debt					$ 5,892,000
Issuance of convertible preferred stock for the conversion of outstanding related party debt, Shares					71,160,000
FoxKiser,LLP [Member]
Related Party Transaction [Line Items]
Due to related party under services agreement				1,423,000
FoxKiser,LLP [Member] \| Promissory Notes [Member]
Related Party Transaction [Line Items]
Due to related party under services agreement				$ 2,400,000
Accounts receivable from related party							$ 1,800,000
Short-term debt, federal interest rate				0.34%
Estimated market rate			15.00%
Aggregate discount				$ 128,000
Accrued interest				3,000
FoxKiser,LLP [Member] \| Second Promissory Notes [Member]
Related Party Transaction [Line Items]
Accounts receivable from related party						$ 600,000
FoxKiser,LLP [Member] \| Initial Conversion Agreement [Member] \| Series B Preferred Stock [Member]
Related Party Transaction [Line Items]
Issuance of convertible preferred stock for the conversion of outstanding related party debt		$ 5,892,000
Issuance of convertible preferred stock for the conversion of outstanding related party debt, Shares		71,160
Preferred stock, par value		$ 0.082798
FoxKiser,LLP [Member] \| Initial Conversion Agreement [Member] \| Preferred Stock [Member]
Related Party Transaction [Line Items]
Amount owed under service agreement								$ 5,892,000
FoxKiser,LLP [Member] \| Service Agreements [Member]
Related Party Transaction [Line Items]
Accrued interest compounding monthly on amount outstanding			1.50%
Related party transaction, description			The amounts outstanding to FoxKiser under the services agreement in excess of 30 days from their due date accrued interest at 1.5 percent per month, compounding monthly.
Due to related party under services agreement				1,423,000
FoxKiser,LLP [Member] \| Service Agreements [Member] \| Promissory Notes [Member]
Related Party Transaction [Line Items]
Interest expense			$ 20,000	$ 321,000	$ 611,000
FoxKiser,LLP [Member] \| Service Agreements [Member] \| Series C Preferred Stock [Member]
Related Party Transaction [Line Items]
Issuance of convertible preferred stock for the conversion of outstanding related party debt, Shares	585
Preferred stock, par value	$ 6.477
Due to related party under services agreement			$ 0
FoxKiser,LLP [Member] \| Service Agreements [Member] \| Series C Preferred Stock [Member] \| Promissory Notes [Member]
Related Party Transaction [Line Items]
Issuance of convertible preferred stock for the conversion of outstanding related party debt	$ 3,792,000
FoxKiser,LLP [Member] \| Service Agreements [Member] \| Series C Preferred Stock [Member] \| Second Promissory Notes [Member]
Related Party Transaction [Line Items]
Issuance of convertible preferred stock for the conversion of outstanding related party debt	2,403,000
FoxKiser,LLP [Member] \| Service Agreements [Member] \| Series C Preferred Stock [Member] \| Primary Promissory Notes [Member]
Related Party Transaction [Line Items]
Issuance of convertible preferred stock for the conversion of outstanding related party debt	$ 1,389,000
FoxKiser,LLP [Member] \| Second Conversion Agreement [Member] \| Preferred Stock [Member] \| Maximum [Member]
Related Party Transaction [Line Items]
Amount owed under service agreement							$ 2,000,000

Commitments and Contingencies - Additional Information (Detail)					1 Months Ended				9 Months Ended	12 Months Ended
	Jan. 31, 2015 USD ($)	Nov. 10, 2014 USD ($)	Nov. 19, 2010 USD ($)	Mar. 06, 2009 USD ($)	Jan. 31, 2016 USD ($)	Oct. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Mar. 31, 2015	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) Milestone	Dec. 31, 2014 USD ($) Milestone	Dec. 31, 2013 USD ($)
Other Commitments [Line Items]
Tenant improvement allowance received							$ 286,000
Operating Leases, Rent Expense, Net										$ 396,000	$ 45,000	$ 45,000
Claims paid to date related to indemnification issues										0
Accruals or expenses related to indemnification issues										$ 0	0
Rockville, Maryland [Member]
Other Commitments [Line Items]
Monthly lease payments						$ 24,000	$ 41,000
Lease period							5 years	5 years 6 months
Lease expiration date								Sep. 30, 2020
Options to extend the lease								6 years
Lease commenced date								2015-04
Lease term										Extend the term of the existing lease to October 2020
Rockville, Maryland [Member] \| Subsequent Event [Member]
Other Commitments [Line Items]
Monthly lease payments					$ 38,000
Lease period					7 years 6 months
Lease commenced date					2016-03
Tenant improvement allowance received					$ 725,000
FoxKiser,LLP [Member]
Other Commitments [Line Items]
Monthly lease payments	$ 20,000
Related party transaction expense										$ 405,000	2,979,000	2,580,000
The Trustees of the University of Pennsylvania [Member]
Other Commitments [Line Items]
Percentage of ownership interest issued as consideration for license agreement										24.50%
Accrued expenses										$ 440,000	305,000
Related party transaction expense									$ 5,216,000		1,378,000	2,921,000
The Trustees of the University of Pennsylvania [Member] \| License Fees [Member]
Other Commitments [Line Items]
Related party transaction expense										866,000	716,000	214,000
The Trustees of the University of Pennsylvania [Member] \| License Fees [Member] \| Sublicense Fees [Member]
Other Commitments [Line Items]
Related party transaction expense									264,000	703,000	443,000	76,000
The Trustees of the University of Pennsylvania [Member] \| License Fees [Member] \| Royalties on Sales of Reagents [Member]
Other Commitments [Line Items]
Related party transaction expense									8,000	9,000	17,000	18,000
The Trustees of the University of Pennsylvania [Member] \| License Fees [Member] \| Maintenance of Licensed Patents [Member]
Other Commitments [Line Items]
Related party transaction expense									118,000	154,000	256,000	120,000
GlaxoSmithKline LLC [Member]
Other Commitments [Line Items]
Percentage of ownership interest issued as consideration for license agreement				19.90%
Accrued expenses										526,000	2,028,000
Related party transaction expense										$ 1,281,000	885,000	542,000
Number of milestone \| Milestone										0
Milestone payment obligation				$ 1,500,000						$ 0
GlaxoSmithKline LLC [Member] \| Sublicense Fees [Member]
Other Commitments [Line Items]
Related party transaction expense									264,000	703,000	443,000	76,000
GlaxoSmithKline LLC [Member] \| Royalties on Sales of Reagents [Member]
Other Commitments [Line Items]
Related party transaction expense									5,000	5,000	10,000	11,000
GlaxoSmithKline LLC [Member] \| Maintenance of Licensed Patents [Member]
Other Commitments [Line Items]
Related party transaction expense									$ 474,000	$ 573,000	432,000	$ 455,000
ARIAD Pharmaceuticals, Inc [Member]
Other Commitments [Line Items]
Number of milestone \| Milestone										0
Annual maintenance fees			$ 50,000							$ 0
Milestone payments										0
Royalty expense incurred										0
Sublicense fees										0
Amounts due under agreement										$ 0	$ 0
ARIAD Pharmaceuticals, Inc [Member] \| Maximum [Member]
Other Commitments [Line Items]
Contractual obligation			2,300,000
ARIAD Pharmaceuticals, Inc [Member] \| Common Class A [Member]
Other Commitments [Line Items]
Fair value of stock issued for license			$ 726,000
Regents of the University of Minnesota [Member]
Other Commitments [Line Items]
Number of milestone \| Milestone										0	0
Annual maintenance fees		$ 9,000
Milestone payments										$ 0	$ 0
Amounts due under agreement										$ 0	$ 0
Up-front fee paid		25,000
Regents of the University of Minnesota [Member] \| Annual License Maintenance Fee [Member] \| Maximum [Member]
Other Commitments [Line Items]
Contractual obligation		15,000
Regents of the University of Minnesota [Member] \| Annual License Maintenance Fee [Member] \| Minimum [Member]
Other Commitments [Line Items]
Contractual obligation		5,000
Regents of the University of Minnesota [Member] \| Royalties And Sublicense Fees [Member] \| Maximum [Member]
Other Commitments [Line Items]
Contractual obligation		$ 125,000

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Non-Cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2015 USD ($)
Operating Leases Future Minimum Payments Due [Abstract]
2016	$ 777
2017	824
2018	848
2019	874
2020	832
Thereafter	144
Total minimum lease payments	$ 4,299

Commitments and Contingencies - Summary of Expenses Incurred by Company (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
The Trustees of the University of Pennsylvania [Member]
Other Commitments [Line Items]
Total related party transaction expense	$ 5,216		$ 1,378	$ 2,921
GlaxoSmithKline LLC [Member]
Other Commitments [Line Items]
Total related party transaction expense		$ 1,281	885	542
Sublicense Fees [Member] \| GlaxoSmithKline LLC [Member]
Other Commitments [Line Items]
Total related party transaction expense	264	703	443	76
Royalties on Sales of Reagents [Member] \| GlaxoSmithKline LLC [Member]
Other Commitments [Line Items]
Total related party transaction expense	5	5	10	11
Maintenance of Licensed Patents [Member] \| GlaxoSmithKline LLC [Member]
Other Commitments [Line Items]
Total related party transaction expense	474	573	432	455
License Fees [Member] \| The Trustees of the University of Pennsylvania [Member]
Other Commitments [Line Items]
Total related party transaction expense		866	716	214
License Fees [Member] \| Sublicense Fees [Member] \| The Trustees of the University of Pennsylvania [Member]
Other Commitments [Line Items]
Total related party transaction expense	264	703	443	76
License Fees [Member] \| Royalties on Sales of Reagents [Member] \| The Trustees of the University of Pennsylvania [Member]
Other Commitments [Line Items]
Total related party transaction expense	8	9	17	18
License Fees [Member] \| Maintenance of Licensed Patents [Member] \| The Trustees of the University of Pennsylvania [Member]
Other Commitments [Line Items]
Total related party transaction expense	$ 118	$ 154	$ 256	$ 120

Capitalization - Additional Information (Detail)						12 Months Ended
Capitalization - Additional Information (Detail)	May 15, 2015 USD ($) $ / shares shares	Jan. 13, 2015 USD ($) $ / shares shares	Sep. 16, 2014 USD ($) Installment Director $ / shares shares	Oct. 30, 2013 USD ($) $ / shares shares	Dec. 31, 2010 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) Installment Director $ / shares shares	Dec. 31, 2014 $ / shares shares	Dec. 31, 2013 shares
Schedule of Capitalization [Line Items]
Closing date of IPO						Sep. 22, 2015
Outstanding convertible preferred stock into common stock \| shares						16,298,000
Common stock, shares authorized \| shares						100,000,000	9,500,000
Common stock, par value						$ 0.0001	$ 0.0001
Preferred stock, shares authorized \| shares						10,000,000	0
Preferred stock, par value						$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized \| shares							4,299,000
Convertible preferred stock, par value							$ 0.0001
Pre-tax cumulative internal rate of return						8.00%
Redemption date of preferred stock						Oct. 30, 2018
Number of Installments \| Installment						3
Conversion Rate						1
Voting right of the preferred stock holders						one vote for each share of common stock
Number of directors entitled to elect by outstanding common stock holders \| Director						1
Net gain on extinguishment of convertible preferred stock \| $						$ 759,000
Common Stock [Member] \| Class A Units [Member]
Schedule of Capitalization [Line Items]
Capital units additional units issued \| shares						19,476,000
Minimum [Member]
Schedule of Capitalization [Line Items]
Gross proceeds from issuance and sale of convertible preferred stock \| $						$ 40,000,000
Percentage of voting power held by stockholders						50.00%
Conversion to C-corporation [Member]
Schedule of Capitalization [Line Items]
Reverse stock split conversion ratio			50
Percentage of voting power held by stockholders			50.00%
Number of Installments \| Installment			3
Conversion Rate							1
Voting right of the preferred stock holders						one vote for each share of common stock
Number of directors entitled to elect by outstanding common stock holders \| Director			1
Conversion to C-corporation [Member] \| Class A Units [Member]
Schedule of Capitalization [Line Items]
Reverse stock split conversion ratio			50
Conversion of stock shares converted \| shares			2,643
Conversion to C-corporation [Member] \| Common Stock [Member] \| Class A Units [Member]
Schedule of Capitalization [Line Items]
Capital units issued \| shares			132,148
Capital units, outstanding \| shares			132,148
Conversion to C-corporation [Member] \| Common Stock [Member] \| Class B Units [Member] \| 2009 Equity Incentive Plan [Member]
Schedule of Capitalization [Line Items]
Capital units issued \| shares								22,828,000
Capital units, authorized \| shares								24,500,000
Stock-based compensation expense \| $						$ 0
Incremental compensation cost \| $						$ 0
Conversion to C-corporation [Member] \| Minimum [Member]
Schedule of Capitalization [Line Items]
Gross proceeds from issuance and sale of convertible preferred stock \| $			$ 50,000,000
Original issuance price of conversion rate per share			$ 0.206995
Series A Convertible Preferred Stock [Member]
Schedule of Capitalization [Line Items]
Convertible preferred stock, shares authorized \| shares						0	2,393,000
Convertible preferred stock, par value							$ 0.0001
Convertible preferred stock, shares issuance and sale \| shares					119,656,000	0	2,393,000
Convertible preferred stock, per share price					$ 0.0251
Gross proceeds from issuance and sale of convertible preferred stock \| $					$ 3,000,000
Redemption date of preferred stock						Dec. 31, 2019
Preferred stock dividend rate per annum for each share						$ 0.1003
Original issuance redemption price per share						1.255
Original issuance price of conversion rate per share						$ 1.255
Number of directors entitled to elect by temporary equity holders \| Director						3
Net gain on extinguishment of convertible preferred stock \| $						$ (1,317,000)
Original issuance price of liquidation preference per share						$ 1.255
Convertible preferred stock, shares outstanding \| shares						0	2,393,000
Series A Convertible Preferred Stock [Member] \| Conversion to C-corporation [Member]
Schedule of Capitalization [Line Items]
Preferred stock, par value			$ 1.255
Preferred Units, Issued \| shares			119,656
Preferred Units, Outstanding \| shares			119,656
Conversion of stock shares converted \| shares			2,393
Preferred stock dividend rate per annum for each share			$ 0.1003
Original issuance redemption price per share			1.255
Original issuance price of conversion rate per share			$ 1.255
Number of directors entitled to elect by temporary equity holders \| Director			3
Series B Convertible Preferred Stock [Member]
Schedule of Capitalization [Line Items]
Convertible preferred stock, shares authorized \| shares						0	1,906,000
Convertible preferred stock, par value							$ 0.0001
Convertible preferred stock, shares issuance and sale \| shares				95,315,000		0	1,906,000
Convertible preferred stock, per share price				$ 0.082798
Gross proceeds from issuance and sale of convertible preferred stock \| $				$ 7,857,000
Convertible preferred stock, net of issuance cost \| $				35,000
Proceeds from exercise of stock options \| $				1,965,000
Convertible preferred stock, conversion of other debt \| $				$ 5,892,000
Redemption date of preferred stock						Dec. 31, 2019
Preferred stock dividend rate per annum for each share						$ 0.331192
Original issuance redemption price per share						4.1399
Original issuance price of conversion rate per share						$ 4.1399
Number of directors entitled to elect by temporary equity holders \| Director						1
Net gain on extinguishment of convertible preferred stock \| $						$ 2,076,000
Original issuance price of liquidation preference per share						$ 4.1399
Convertible preferred stock, shares outstanding \| shares						0	1,906,000
Series B Convertible Preferred Stock [Member] \| Conversion to C-corporation [Member]
Schedule of Capitalization [Line Items]
Preferred stock, par value			$ 4.1399
Preferred Units, Issued \| shares			95,315
Preferred Units, Outstanding \| shares			95,315
Conversion of stock shares converted \| shares			1,906
Preferred stock dividend rate per annum for each share			$ 0.331192
Original issuance redemption price per share			4.1399
Original issuance price of conversion rate per share			$ 4.1399
Number of directors entitled to elect by temporary equity holders \| Director			1
Series C Convertible Preferred Stock [Member]
Schedule of Capitalization [Line Items]
Convertible preferred stock, par value		$ 0.000001
Convertible preferred stock, shares issuance and sale \| shares		4,632,000
Convertible preferred stock, per share price		$ 0.06477
Gross proceeds from issuance and sale of convertible preferred stock \| $		$ 30,000,000				$ 26,021,000
Convertible preferred stock, net of issuance cost \| $		187,000
Proceeds from exercise of stock options \| $		26,021,000
Convertible preferred stock, conversion of other debt \| $		$ 3,792,000
Redemption date of preferred stock						Dec. 31, 2019
Preferred stock dividend rate per annum for each share						$ 0.51816
Original issuance redemption price per share						6.477
Original issuance price of conversion rate per share						$ 6.477
Number of directors entitled to elect by temporary equity holders \| Director						1
Original issuance price of liquidation preference per share						$ 6.477
Series D Convertible Preferred Stock [Member]
Schedule of Capitalization [Line Items]
Convertible preferred stock, par value	$ 0.0001
Convertible preferred stock, shares issuance and sale \| shares	7,367,000
Convertible preferred stock, per share price	$ 9.5699
Gross proceeds from issuance and sale of convertible preferred stock \| $	$ 67,998,000					$ 67,998,000
Convertible preferred stock, net of issuance cost \| $	$ 2,502,000
Redemption date of preferred stock						Dec. 31, 2019
Preferred stock dividend rate per annum for each share						$ 0.765592
Original issuance redemption price per share						9.5699
Original issuance price of conversion rate per share						$ 9.5699
Number of directors entitled to elect by temporary equity holders \| Director						1
Original issuance price of liquidation preference per share						$ 9.5699
Convertible Preferred Stock [Member]
Schedule of Capitalization [Line Items]
Convertible preferred stock, shares issuance and sale \| shares						0
Convertible preferred stock, shares outstanding \| shares						0

Capitalization - Schedule of Reserved Shares of Common Stock for Future Issuance (Detail) - shares shares in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Capitalization [Line Items]
Reserved common shares	6,252	10,514
Series A Convertible Preferred Stock [Member]
Schedule of Capitalization [Line Items]
Reserved common shares		2,393
Series B Convertible Preferred Stock [Member]
Schedule of Capitalization [Line Items]
Reserved common shares		1,906
Equity Incentive Plans [Member]
Schedule of Capitalization [Line Items]
Reserved common shares	5,998	2,500
Employee Stock Purchase Plan [Member]
Schedule of Capitalization [Line Items]
Reserved common shares	254
Debt with Share Settlement Option [Member]
Schedule of Capitalization [Line Items]
Reserved common shares		3,715

Significant Agreements - Additional Information (Detail) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 EUR (€)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($) Grant	Dec. 31, 2012 USD ($) Grant	Dec. 31, 2010 USD ($) Grant
Significant Agreements [Line Items]
License fee									$ 600
Fee payable in cash									$ 300
License fee payment description									In July 2013, the Company granted an exclusive commercial license to Audentes. The license required an up-front fee of $600, $300 of which was payable in cash and the remainder in common stock of Audentes.	In July 2013, the Company granted an exclusive commercial license to Audentes. The license required an up-front fee of $600, $300 of which was payable in cash and the remainder in common stock of Audentes.
Cost method investments	$ 300				$ 303				$ 300		$ 303
Milestone fee upon submission of preclinical regulatory filings									500
Milestone fee upon commencement of clinical trials in humans									16,650
Milestone fee upon submission of regulatory approval filings									28,000
Milestone fee upon approval of commercial products by regulatory agencies									73,500
Milestone fee upon achievement of specified sales targets for licensed products									47,000
Research and development (including amounts to related parties)									17,279		4,961	$ 5,051
Grant revenue									306		1,219	1,964
Accounts receivable	2,136				805				2,136		805
Unbilled receivables					327						327
Revenue recorded from reimbursement	4,441	$ 1,140	$ 1,363	$ 644	1,151	$ 483	$ 1,549	$ 2,937	$ 7,588		6,120	6,087
MeuSIX [Member]
Significant Agreements [Line Items]
Percentage of reimbursed by grantor									75.00%	75.00%
Maximum amount of reimbursed cost recognized for grant \| €										€ 2,273,000
Grant value based on average conversion rate									$ 2,859
Period of grant									5 years	5 years
Research and development (including amounts to related parties)									$ 912		1,109	882
Grant revenue									258		832	661
Accounts receivable	534				865				534		865
Unbilled receivables	0				320				0		320
National Institute of Health [Member]
Significant Agreements [Line Items]
Grant revenue												$ 261	$ 515	$ 3,063
Accounts receivable	0				51				0		51
Number of grants awarded \| Grant												1	2	2
Refunds payable to grantor	0								0
National Institute of Health [Member] \| Research and Development Costs [Member]
Significant Agreements [Line Items]
Revenue recorded from reimbursement									46		387	$ 1,303
Audentes Therapeutics Inc
Significant Agreements [Line Items]
Cost method investments	$ 300				$ 300				$ 300		$ 300

Significant Agreements - Schedule of License Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
License Agreement Revenue Recognition [Abstract]
Up-front fees and option fees for commercial licenses	$ 5,900	$ 4,000	$ 3,400
Milestone fees for commercial licenses	250
Maintenance fees for commercial licenses	635	385	200
Research and other license revenue	240	190	155
Licenses revenue including amounts from related parties	$ 7,025	$ 4,575	$ 3,755

Stock-based Compensation - Additional Information (Detail) - USD ($)		12 Months Ended
	Sep. 16, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from exercise of stock options		$ 107,000	$ 1,000
Unrecognized stock-based compensation expense related to employees' awards		$ 11,133,000
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation, weighted-average period		3 years 5 months 23 days
2014 Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares authorized for issuance			2,500,000
2015 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares authorized for issuance	2,952,000	6,125,000
Percentage of annual increase in number of shares available for future issuance		4.00%
Shares available for future grants		2,314,000
Stock options expiration date		10 years
Stock options vesting period		4 years
Stock plan expiration date		2025-06
Weighted-average fair values of options granted		$ 7.08	$ 0.51
Weighted-average grant date fair value of option, vested		$ 1.10	$ 0.51
Exercise of stock options, Shares		125,000	2,000
Total intrinsic value of options exercised		$ 525,000	$ 0
Stock options granted		1,727,000	2,132,000	0
Stock-based compensation expense				$ 0
2015 Equity Incentive Plan [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 1,443,000	$ 299,000
2015 Equity Incentive Plan [Member] \| Non Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 1,478,000	$ 20,000
2015 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, description		The number of shares reserved for issuance under the 2015 ESPP automatically increases on the first business day of each fiscal year, commencing in 2016
Share-based compensation arrangement by share-based payment award, percentage of outstanding stock minimum	1.00%
2015 Employee Stock Purchase Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares authorized for issuance	254,000

Stock-based Compensation - Summary of Stock Option Activity (Detail) - 2015 Equity Incentive Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Shares Outstanding, Beginning Balance	2,107,000
Shares, Granted	1,727,000	2,132,000	0
Shares, Exercised	(125,000)	(2,000)
Shares, Cancelled or forfeited	(25,000)	(23,000)
Shares Outstanding, Ending Balance	3,684,000	2,107,000
Shares, Exercisable	1,328,000
Shares, Vested and expected to vest	3,684,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average Exercise Price Outstanding, Beginning Balance	$ 0.85
Weighted-average Exercise Price, Granted	10.80	$ 0.85
Weighted-average Exercise Price, Exercised	0.85	0.85
Weighted-average Exercise Price, Cancelled or forfeited	1.19	0.85
Weighted-average Exercise Price, Outstanding, Ending Balance	5.52	$ 0.85
Weighted-average Exercise Price, Exercisable	1.45
Weighted-average Exercise Price, Vested and expected to vest	$ 5.52
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average Remaining Contractual Life (Years) Outstanding	9 years 1 month 6 days	9 years 9 months 18 days	0 years
Weighted-average Remaining Contractual Life (Years), Exercisable	8 years 9 months 18 days
Weighted-average Remaining Contractual Life (Years), Vested and expected to vest	9 years 1 month 6 days
Aggregate Intrinsic Value Outstanding, Beginning Balance	$ 379
Aggregate Intrinsic Value Outstanding, Ending Balance	44,472	$ 379
Aggregate Intrinsic Value, Exercisable	20,194
Aggregate Intrinsic Value, Vested and expected to vest	$ 44,472

Stock-based Compensation - Stock-Based Compensation Expense Related to Issuance of Stock Option Awards to Employees and Non-employees (Detail) - 2014 and 2015 Equity Incentive Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,921	$ 319
Research and Development Costs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,760	60
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,161	$ 259

Stock-based Compensation - Schedule of Employees Stock Purchase Plan Valuation Assumptions (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	68.00%	64.00%
Expected term (in years)	6 years 1 month 6 days	6 years
Risk-free interest rate	1.70%	2.00%
Expected dividend yield	0.00%	0.00%
Non Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	75.00%	65.00%
Expected term (in years)	9 years 6 months	9 years 10 months 24 days
Risk-free interest rate	2.10%	2.40%
Expected dividend yield	0.00%	0.00%

Retirement Plan - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Contribution by company	$ 184
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Company's matching contribution, percentage of employee deferrals	5.75%

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Line Items]
Income tax expenses, foreign	$ 0	$ 0	$ 0
Income tax expense (benefit)	$ 0	0	$ 0
Federal statutory income tax rate, percent	34.00%
Increase in valuation allowance	$ 9,453,000	1,252,000
Cumulative changes in ownership Interest percentage threshold, subject to annual limitation of NOL	50.00%
Ownership interest change period	3 years
Domestic Country
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 21,215,000	2,979,000
Operating Loss Carryforwards Expiration Year	2035
U. S State Tax Authority [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 34,199,000	$ 13,406,000
Operating Loss Carryforwards Expiration Year	2035

Income Taxes - Schedule of Reconciliation of Effective Income Tax Expense (Benefit) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal income tax benefit at statutory rate	$ (7,756,000)	$ (1,089,000)
State income tax benefit, net of federal benefit	(1,511,000)	(264,000)	$ (537,000)
Change in income tax rates upon conversion to C-corporation		427,000
Federal deferred tax assets upon conversion to C-corporation		(105,000)
Step-up in assets upon conversion to C-corporation	(709,000)	(448,000)
Stock-based compensation expense for incentive stock options	283,000	98,000
Imputed interest on related party promissory notes		52,000
Taxable gain upon conversion to C-corporation		73,000
Other non-deductible expenses and reconciling items	240,000	4,000
Change in valuation allowance	9,453,000	1,252,000	537,000
Total income tax expense (benefit)	$ 0	$ 0	$ 0

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 9,254	$ 1,844
Step-up in assets upon conversion to C-corporation	1,046	438
Stock-based compensation expense for non-qualified stock options	855	31
Unrealized losses on marketable securities	284
Deferred rent	97
Accruals and other	568	42
Total deferred tax assets before valuation allowance	12,104	2,355
Valuation allowance	(12,093)	(2,355)
Total deferred tax assets	11
Deferred tax liabilities:
Depreciation	(11)
Total deferred tax liabilities	(11)
Net deferred tax assets	$ 0	$ 0

Related Party Transactions - Summary of Expenses Incurred by Company (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
The Trustees of the University of Pennsylvania [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	$ 5,216		$ 1,378	$ 2,921
The Trustees of the University of Pennsylvania [Member] \| Manufacturing of Reagents for Sale [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	80		92	143
The Trustees of the University of Pennsylvania [Member] \| Research and Development Services [Member]
Related Party Transaction [Line Items]
Total related party transaction expense	$ 5,136		1,286	2,778
FoxKiser,LLP [Member]
Related Party Transaction [Line Items]
Total related party transaction expense		$ 405	2,979	2,580
FoxKiser,LLP [Member] \| Research and Development Costs [Member]
Related Party Transaction [Line Items]
Total related party transaction expense		168	1,283	1,111
FoxKiser,LLP [Member] \| General and Administrative [Member]
Related Party Transaction [Line Items]
Total related party transaction expense		$ 237	$ 1,696	$ 1,469

Related Party Transactions - Additional Information (Detail) - USD ($) shares in Thousands, $ in Thousands		1 Months Ended							9 Months Ended	12 Months Ended
	Jan. 02, 2016	Oct. 31, 2015	Aug. 31, 2015	May 31, 2015	Mar. 31, 2015	Sep. 30, 2014	Dec. 31, 2013	Oct. 30, 2013	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Research and other license revenue										$ 240	$ 190	$ 155
General and administrative (including amounts to related parties)										11,912	3,851	5,474
Related party receivables											750
Due to related party under services agreement										(34)	768	3,192
Related party receivables										(750)	$ (174)	924
Agreement expiry date											Dec. 31, 2014
License revenue from license agreements										5,025	$ 4,355	1,055
Advance payment liability for proceeds received for undelivered material										(26)	153
Due to related party under services agreement											1,423
Service Agreements [Member] \| Subsequent Event [Member]
Related Party Transaction [Line Items]
Amount received for purchase of materials from related party	$ 80
Commercial License Agreement [Member]
Related Party Transaction [Line Items]
Consideration in shares issued by Dimension for license granted		9,990						10,000
License agreement, estimated fair value of stock issued								$ 2,700
Research and other license revenue							$ 2,700				$ 2,700
General and administrative (including amounts to related parties)							$ 2,697
Commercial License Agreement [Member] \| Parent Company [Member]
Related Party Transaction [Line Items]
Consideration in shares issued by Dimension for license granted											10
License agreement, estimated fair value of stock issued											$ 3
Selling, General and Administrative Expenses [Member] \| Commercial License Agreement [Member]
Related Party Transaction [Line Items]
License agreement, estimated fair value of stock issued		$ 2,697
The Trustees of the University of Pennsylvania [Member]
Related Party Transaction [Line Items]
Manufacturing and research and development costs											677
Dimension Therapeutics, Inc. [Member]
Related Party Transaction [Line Items]
Annual maintenance fees					$ 50
Carrying amount of investment											3
Related party receivables											750
Research and development expense reimbursements earned											6,177	924
Related party receivables											750
Net reimbursable costs											0	0
Extension fee paid by Dimension for extension of option						$ 150
Option fee payable upon exercise					1,000
Milestone payment received from option and license agreement			$ 1,000	$ 1,000	$ 9,000					1,000
License revenue from license agreements									$ 2,000		220	2,700
Amount received for purchase of materials from related party											200
Gain on disposal of the material to related party											200
Gains related to delivery of purchased material										26	47
Advance payment liability for proceeds received for undelivered material										$ 127	153
Dimension Therapeutics, Inc. [Member] \| Commercial License Agreement [Member]
Related Party Transaction [Line Items]
License agreement initiation date										Oct. 30, 2013
Annual maintenance fees										$ 35
Penn [Member]
Related Party Transaction [Line Items]
Research and development expense to Penn											6,177	$ 924
Due to related party under services agreement											750
FoxKiser,LLP [Member]
Related Party Transaction [Line Items]
Due to related party under services agreement											1,423
FoxKiser,LLP [Member] \| Service Agreements [Member]
Related Party Transaction [Line Items]
Related party transaction, description										The amounts outstanding to FoxKiser under the services agreement in excess of 30 days from their due date accrued interest at 1.5 percent per month, compounding monthly.
Accrued interest compounding monthly on amount outstanding										1.50%
Due to related party under services agreement											1,423
Chief Scientific Advisor [Member]
Related Party Transaction [Line Items]
Related party transaction expenses from transactions with related party advisory fees										$ 180	$ 45
Shares, Granted										70	142

Net Loss Per Share - Schedules for Computation of Diluted Weighted-Average Shares Outstanding (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding	3,684	10,121	4,299
Series A Convertible Preferred Stock and Preferred Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding		2,393	2,393
Series B Convertible Preferred Stock and Preferred Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding		1,906	1,906
Stock Options Issued and Outstanding [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding	3,684	2,107
Debt with Share Settlement Option [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted weighted average shares outstanding		3,715

Supplemental Disclosures - Schedules of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Accrued personnel costs	$ 1,371
Accrued external research and development	791	$ 781
Accrued sublicense fees and royalties on reagent sales	260
Other accrued expenses and current liabilities	776	334
Accrued expenses and other current liabilities	$ 3,198	$ 1,115

Selected Quarterly Financial Information (Unaudited) - Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue recorded from reimbursement	$ 4,441	$ 1,140	$ 1,363	$ 644	$ 1,151	$ 483	$ 1,549	$ 2,937	$ 7,588	$ 6,120	$ 6,087
Total operating expenses	9,942	8,487	7,659	4,637	3,366	2,184	2,150	2,102	30,725	9,802	10,863
Net loss	$ (5,178)	$ (7,332)	$ (6,290)	$ (4,011)	$ (2,333)	$ (1,793)	$ (672)	$ 795	$ (22,811)	$ (4,003)	$ (5,387)
Basic and diluted net income (loss) per common share	$ (0.20)	$ (1.52)	$ (3.24)	$ (0.94)	$ (0.97)	$ (0.73)	$ (0.34)	$ 0.08	$ (2.59)	$ (1.82)	$ (2.50)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details