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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2015	Nov. 10, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Trading Symbol	HSGX
Entity Registrant Name	Histogenics Corporation
Entity Central Index Key	0001372299
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		13,273,470

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 37,723	$ 58,060
Prepaid expenses and other current assets	365	796
Total current assets	38,088	58,856
Property and equipment, net	5,513	4,878
Intangible asset, net	510	510
Noncurrent deferred tax assets, net	1,053	651
Restricted cash	137	604
Total assets	45,301	65,499
Current liabilities:
Accounts payable	2,001	4,886
Accrued expenses	2,449	1,683
Current portion of deferred rent	225	219
Current portion of deferred lease incentive	379	407
Current portion of equipment loan	583	405
Deferred tax liabilities, net	1,053	651
Total current liabilities	6,690	8,251
Deferred rent, long-term	381	379
Deferred lease incentive, long-term	1,147	1,318
Equipment loan, long-term	907	1,345
Total liabilities	9,125	11,293
Commitments and contingencies (Note 5)
Stockholders' equity:
Preferred stock, $0.01 par value; authorized shares-10,000,000 at September 30, 2015 and December 31, 2014; none issued and outstanding at September 30, 2015 and December 31, 2014
Common stock, $0.01 par value; authorized shares-100,000,000 at September 30, 2015 and December 31, 2014; 13,273,470 shares issued and outstanding at September 30, 2015 and 12,755,012 shares issued and outstanding at December 31, 2014	132	127
Additional paid-in capital	193,260	187,620
Accumulated deficit	(157,216)	(133,541)
Total stockholders' equity	36,176	54,206
Total liabilities and stockholders' equity	$ 45,301	$ 65,499

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred stock par value	$ 0.01	$ 0.01
Preferred stock authorized	10,000,000	10,000,000
Preferred stock issued	0	0
Preferred stock outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	13,273,470	12,755,012
Common stock, shares outstanding	13,273,470	12,755,012

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating expenses:
Research and development	$ 5,848	$ 13,237	$ 17,470	$ 21,280
General and administrative	2,191	1,703	6,035	4,843
Total operating expenses	8,039	14,940	23,505	26,123
Loss from operations	(8,039)	(14,940)	(23,505)	(26,123)
Other income (expense):
Interest expense, net	(23)	(19)	(111)	(19)
Other income (expense), net	(16)	(1)	(59)	(6)
Change in fair value of warrant liability, other liability and net sales distribution payment liability		2,986		2,435
Total other income (expense), net	(39)	2,966	(170)	2,410
Net loss	(8,078)	(11,974)	(23,675)	(23,713)
Loss attributable to common stockholders-basic and diluted	$ (8,078)	$ (11,974)	$ (23,675)	$ (27,233)
Loss per common share-basic and diluted:	$ (0.61)	$ (19.38)	$ (1.79)	$ (45.49)
Weighted-average shares used to compute earnings per common share-basic and diluted:	13,238,997	617,860	13,218,765	598,684

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (23,675)	$ (23,713)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,182	482
Deferred rent and lease incentive	(191)	(247)
Stock-based compensation	854	356
Warrant expense	14
Non-cash consideration for licensed technology		10,000
Change in fair value of liabilities		(2,435)
Amortization of deferred financing costs		(39)
Prepaid expenses and other current assets	431	(172)
Other non-current assets	467	(79)
Accounts payable	(2,885)	1,993
Accrued expenses	766	594
Net cash used in operating activities	(23,037)	(13,260)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(1,818)	(1,577)
Net cash used in investing activities	(1,818)	(1,577)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from overallotment, net of issuance costs	4,738
Borrowings under equipment term loan		464
Payment on equipment term loan	(260)
Issuance of Series A-1 preferred stock, net of cash issuance costs of $73		10,314
Costs associated with Initial Public Offering		(1,443)
Proceeds from the exercise of common stock options	40	26
Net cash provided by financing activities	4,518	9,361
Net decrease in cash and cash equivalents	(20,337)	(5,476)
Cash and cash equivalents-Beginning of period	58,060	8,734
Cash and cash equivalents-End of period	$ 37,723	$ 3,258

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Statement of Cash Flows [Abstract]
Issuance costs	$ 73	$ 73

Nature of Business

9 Months Ended

Sep. 30, 2015

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of Business

1. NATURE OF BUSINESS

Organization

Histogenics Corporation (the “Company”) is a Delaware corporation and has its principal operations in Waltham, Massachusetts. The Company is a regenerative medicine company engaged in developing and commercializing products in the musculoskeletal segment of the marketplace. The Company is developing technology and products to treat cartilage damage, including NeoCart for the repair of cartilage lesions. NeoCart is currently in a Phase 3 clinical trial in the United States under a special protocol assessment with the U.S. Food and Drug Administration (“FDA”) for the treatment of knee cartilage damage.

Since its inception, the Company has devoted substantially all of its efforts to product development, recruiting management and technical staff, raising capital, starting up production and building infrastructure and has not generated revenues from its planned principal operations. Expenses have primarily been for research and development and administrative costs.

The Company is subject to a number of risks. Principal among these risks are: the successful development of its products, successfully enrolling patients in its clinical trials in a timely manner, protection of its intellectual property, obtaining FDA approval for its products and maintaining ongoing compliance with government regulations, the ability to obtain adequate financing, fluctuations in operating results, dependence on key personnel and collaborative partners, adoption of the Company’s products by the physician community, rapid technological changes inherent in the markets targeted, and substitute products and competition from larger companies.

Initial public offering

On December 8, 2014, the Company closed its initial public offering (“IPO”) whereby the Company sold 5,909,091 shares of common stock at a price of $11.00 per share for gross proceeds of $65,000. The shares began trading on The Nasdaq Global Market on December 3, 2014. On January 6, 2015, an additional 465,000 shares of common stock were sold at the IPO price of $11.00 per share following the underwriters’ exercise in part of their overallotment option for gross proceeds of $5,115. Gross proceeds from the offering, inclusive of the overallotment, were $70,115. After giving effect to underwriting discounts and commissions and offering expenses payable by the Company, net proceeds were $61,277. In addition, each of the following occurred in connection with the completion of the IPO on December 8, 2014:

•

the conversion of all outstanding shares of the Company’s convertible redeemable preferred stock and accrued dividends into 5,158,407 shares of common stock;

•

the conversion of $11,100 in convertible notes payable and accrued interest into 1,009,115 shares of common stock;

•

the net exercise of certain warrants into 44,531 shares of common stock and the surrender of 5,839 warrant shares to satisfy the contingent payment payable to Purpose Co., Ltd. (“Other Liability”), resulting in the settlement of the related warrant liability and Other Liability upon the closing of the IPO of $490 and $612, respectively, to additional paid-in capital;

•

the termination of the redemption provision of the net sales distribution payment; and

•

the authorization to issue 100,000,000 shares of common stock and 10,000,000 shares of preferred stock.

Basis of Presentation and Principles of Consolidation

The condensed consolidated financial statements are unaudited and have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial reporting. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. These interim condensed consolidated financial statements, in the opinion of the Company’s management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the interim periods ended September 30, 2015 and 2014. The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2014, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on March 27, 2015.

The condensed consolidated financial statements include the accounts of Histogenics Corporation and its wholly-owned subsidiaries, ProChon Biotech Ltd. (“ProChon”) and Histogenics Securities Corporation. All intercompany accounts and transactions are eliminated in consolidation.

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2015

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

The significant accounting policies described in the Company’s audited financial statements as of and for the year ended December 31, 2014, and the notes thereto, which are included in the Annual Report on Form 10-K, have had no material changes during the nine months ended September 30, 2015, except as noted below.

Reclassifications

The Company has reclassified certain prior period amounts to conform to the current period presentation. The amounts reclassified impact research and development expenses and general and administrative expenses for the three months and nine months ended September 30, 2014.

Segment and Geographic Information

Information about the Company’s operations in different geographic regions is presented in the tables below:


	September 30,		December 31,
	2015		2014
Long-lived assets:
United States	$	5,504	$	4,866
Israel		9		12

Total long-lived assets	$	5,513	$	4,878

Fair Value Measurements

The carrying amounts reported in the Company’s condensed consolidated financial statements for cash and cash equivalents, accounts payable and accrued liabilities approximate their respective fair values because of the short-term nature of these accounts.

As a basis for determining the fair value of certain of the Company’s financial instruments, the Company utilizes a three-tier value hierarchy, which prioritizes the inputs used in measuring fair value as follows:

Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date of identical, unrestricted assets.

Level 2: Quoted prices for similar assets, or inputs that are observable, either directly or indirectly, for substantially the full term through corroboration with observable market data. Level 2 includes investments valued at quoted prices adjusted for legal or contractual restrictions specific to the security.

Level 3: Pricing inputs are unobservable for the assets. Level 3 assets include private investments that are supported by little or no market activity. Level 3 valuations are for instruments that are not traded in active markets or are subject to transfer restrictions and may be adjusted to reflect illiquidity and/or non-transferability, with such adjustment generally based on available market evidence. In the absence of such evidence, management’s best estimate is used.

The Company had no assets or liabilities classified as Level 1 or Level 2 as of September 30, 2015 and December 31, 2014, other than the money market fund described in the “Cash and Cash Equivalents” section below, and there were no material re-measurements of fair value with respect to financial assets and liabilities during the periods presented, other than those assets and liabilities that are measured at fair value on a recurring basis. The Company had no assets or liabilities classified as Level 3 as of September 30, 2015 and December 31, 2014. Historically, the Company did have liabilities classified as Level 3 including a warrant liability, the “Other Liability” and the net sales distribution payment liability. These were all settled or terminated upon the closing of the IPO in December 2014.

Transfers are calculated on values as of the transfer date. There were no transfers between Levels 1, 2 and 3 during the nine months ended September 30, 2015 and 2014.

The Company has no liabilities classified as Level 3 that are measured by management at fair value on a quarterly basis as of September 30, 2015.

Cash and Cash Equivalents

The Company considers all highly liquid securities with original final maturities of three months or less from the date of purchase to be cash equivalents. As of September 30, 2015, cash and cash equivalents comprise cash deposits of $5,973 and money market funds of $31,750.

The money market funds are measured at fair value on a recurring basis based on quoted market prices.


					Significant		Significant
			Prices in		other		unobservable
			active markets		observable inputs		inputs
Description	Total		(Level 1)		(Level 2)		(Level 3)
September 30, 2015
Money market funds	$	31,750	$	31,750	$	—	$	—

	$	31,750	$	31,750	$	—	$	—
December 31, 2014
Money market funds	$	49,750	$	49,750	$	—

	$	49,750	$	49,750	$	—	$	—

Intangible Asset

As of September 30, 2015 and December 31, 2014, the Company’s intangible asset consists of acquired in-process research and development (“IPR&D”).

For the nine months ended September 30, 2015 and 2014, the Company determined that there were no triggering events indicating impairment of its IPR&D.

Intangible assets, net of accumulated impairment charges, are summarized as follows:


	As of September 30, 2015							As of December 31, 2014
			Accumulated			Net Book				Accumulated			Net Book
	Cost		Impairment			Value		Cost		Impairment			Value
IPR&D	$	630	$	(120	)	$	510	$	630	$	(120	)	$	510

	$	630	$	(120	)	$	510	$	630	$	(120	)	$	510

Stock-Based Compensation

The Company accounts for stock options and restricted stock based on their grant date fair value and recognizes compensation expense on a straight-line basis over their vesting period. The Company estimates the fair value of stock options as of the date of grant using the Black-Scholes option pricing model, with the exception of stock options that include a market condition, and of restricted stock based on the fair value of the underlying common stock as of the date of grant or the value of the services provided, whichever is more readily determinable. The expense is adjusted for actual forfeitures at year end. Stock-based compensation expense recognized in the condensed consolidated financial statements is based on awards that are ultimately expected to vest. Stock-based compensation expense is classified as research and development or general and administrative based on the grantee’s respective compensation classification.

For stock option grants with vesting triggered by the achievement of performance-based milestones, the expense is recorded over the remaining service period after the point when the achievement of the milestone is probable or the performance condition has been achieved. For stock option grants with both performance-based milestones and market conditions, expense is recorded over the derived service period after the point when the achievement of the performance-based milestone is probable or the performance condition has been achieved. For stock option grants with market conditions, the expense is calculated using the Monte Carlo model based on the grant date fair value of the option and is recorded on a straight line basis over the requisite service period, which represents the derived service period and accelerated when the market condition is satisfied. The Company issued awards with market conditions during the three months ended September 30, 2015. The Company accounts for stock options and restricted stock awards to non-employees using the fair value approach. Stock options and restricted stock awards to non-employees are subject to periodic revaluation over their vesting terms.

Recent Accounting Pronouncements

In May 2014, the FASB issued Accounting Standards Update No. 2014-09 (ASU 2014-09), Revenue from Contracts with Customers (Topic 606), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. In July 2015, the FASB issued a one-year deferral of the effective date of the new revenue recognition standard. The new guidance will be effective for the Company’s first quarter of fiscal year 2018 and early application for fiscal year 2017 would be permitted. The Company’s adoption of this guidance is not expected to have a material impact on the consolidated financial statements.

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 (ASU 2014-12). The amendments in ASU 2014-12 require that a performance target that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. A reporting entity should apply existing guidance in ASC 718, as it relates to awards with performance conditions that affect vesting to account for such awards. The amendments in ASU 2014-12 are effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Early adoption is permitted. Entities may apply the amendments in ASU 2014-12 either: (a) prospectively to all awards granted or modified after the effective date; or (b) retrospectively to all awards with performance targets that are outstanding as of the beginning of the earliest annual period presented in the financial statements and to all new or modified awards thereafter. The Company’s adoption of this guidance is not expected to have a material impact on the consolidated financial statements.

In August 2014, the FASB issued ASU No. 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 (ASU 2014-15), which is intended to define management’s responsibility to evaluate whether there is substantial doubt about an organization’s ability to continue as a going concern and to provide related footnote disclosures. The accounting standards update provides guidance to an organization’s management, with principles and definitions that are intended to reduce diversity in the timing and content of disclosures that are commonly provided by organizations today in the financial statement footnotes. The amendments are effective for annual periods ending after December 15, 2016, and interim periods within annual periods beginning after December 15, 2016. Early adoption is permitted for annual or interim reporting periods for which the financial statements have not previously been issued. The Company does not intend to early adopt this standard. The Company does not anticipate that the adoption of this standard will have a material impact on the consolidated financial statements.

Loss Per Common Share

9 Months Ended

Sep. 30, 2015

Earnings Per Share [Abstract]

Loss Per Common Share

3. LOSS PER COMMON SHARE

The Company computes basic and diluted loss per share using a methodology that gives effect to the impact of outstanding participating securities (the “two-class method”). As the three and nine month periods ended September 30, 2015 and 2014 resulted in net losses, there is no income allocation required under the two-class method or dilution attributed to the weighted-average shares outstanding in the calculation of diluted loss per share.

The following potentially dilutive securities have been excluded from the computation of diluted weighted-average shares outstanding, as they would be anti-dilutive (in common stock equivalent shares):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Convertible redeemable preferred stock and dividends		—		4,558,483		—		4,558,483
Restricted stock and options to purchase common stock		1,233,494		553,982		1,233,494		553,982
Warrants exercisable into common stock		170,102		168,543		170,102		168,543

The Company also had certain warrants and other liabilities outstanding as of September 30, 2014 which could have obligated the Company, its stockholders, or both to issue shares of common stock upon the occurrence of various future events at prices and in amounts that were not determinable until the occurrence of those future events. For the nine months ended September 30, 2014, these included the net sales distribution payment liability. Because the necessary conditions for the conversion or exercise of these instruments had not been satisfied as of September 30, 2014, the Company has excluded these instruments from the table above and the calculation of diluted net income per share for that period. There were no such instruments outstanding during the three months and nine months ended September 30, 2015.

Property and Equipment

9 Months Ended

Sep. 30, 2015

Property, Plant and Equipment [Abstract]

Property and Equipment

4. PROPERTY AND EQUIPMENT

Property and equipment consisted of the following:


	September 30,			December 31,
	2015			2014
Office equipment	$	531		$	467
Laboratory equipment		4,292			2,978
Leasehold improvements		7,682			7,503
Construction in progress		469			270
Software		96			35

Total property and equipment		13,070			11,253
Less: accumulated depreciation		(7,557	)		(6,375	)

Property and equipment, net	$	5,513		$	4,878

Depreciation expense related to property and equipment amounted to $414 and $169 for the three months ended September 30, 2015 and 2014, respectively, and $1,182 and $482 for the nine months ended September 30, 2015 and 2014, respectively.

Commitments and Contingencies

9 Months Ended

Sep. 30, 2015

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

5. COMMITMENTS AND CONTINGENCIES

Operating Leases

The Company leases its office and research facilities in Waltham and Lexington, Massachusetts under non-cancellable operating leases that expire at various dates through year 2023. Terms of the agreements generally provide for an initial rent-free period and future rent escalation, and provide that in addition to minimum lease rental payments, the Company is responsible for a pro-rata share of common area operating expenses. The Company’s wholly-owned subsidiary, ProChon, also leases facilities in Woburn, Massachusetts and Israel.

Rent expense under operating lease agreements amounted to approximately $266 and $275 for the three months ended September 30, 2015 and 2014, respectively, and $857 and $608 for the nine months ended September 30, 2015 and 2014, respectively. In addition, the Company maintained a stand-by letter of credit in connection with the Lexington facility lease of $137 at September 30, 2015 and December 31, 2014. This amount is classified as restricted cash in the condensed consolidated balance sheets.

As an inducement to enter into its Waltham facility lease, the lessor agreed to provide the Company with a construction allowance of up to $3,184 towards the total cost of tenant improvements. The Company has recorded these costs in the condensed consolidated balance sheet as leasehold improvements, with the corresponding liability as deferred lease incentive. This liability is amortized on a straight-line basis over the term of the lease as a reduction of rent expense.

As an inducement to enter into its Lexington facility lease, the lessor agreed to provide the Company with a construction allowance of up to $996 towards the total cost of tenant improvements. The tenant improvement is recorded within leasehold improvements and included as a deferred lease incentive liability in the condensed consolidated balance sheet. Rent expense is recognized on a straight-line basis over the term of the lease and is reduced by the construction allowance.

License Agreements

From time to time, the Company enters into various licensing agreements whereby the Company may use certain technologies in conjunction with its product research and development.

Licensing agreements and the Company’s commitments under the agreements are as follows:

Hydrogel License

In May 2005, the Company entered into an exclusive license agreement with Angiotech Pharmaceuticals (US), Inc. for the use of certain patents, patent application, and knowledge related to the manufacture and use of a hydrogel material in conjunction with NeoCart and certain other products (“Hydrogel License Agreement”). As of September 30, 2015, the Company has paid an aggregate $3,200 in commercialization milestones under the terms of the Hydrogel License Agreement, which have been expensed to research and development.

Under the terms of the Hydrogel License Agreement, the Company’s future commitments include:

•

A one-time $3,000 payment upon approval of an eligible product by the FDA; and

•

Single digit royalties on the net sales of NeoCart and certain other future products.

Tissue Regeneration License

In April 2001, the Company entered into an exclusive license agreement with The Board of Trustees of the Leland Stanford Junior University (“Stanford University”) for the use of certain technology to develop, manufacture and sell licensed products in the field of growth and regeneration of cartilage (“Tissue Regeneration License Agreement”). The term of the Tissue Regeneration License Agreement extends to the expiration date of Stanford University’s last to expire domestic or foreign patents. As of September 30, 2015, the Company has paid an aggregate $642 in patent reimbursement costs, royalty fees, and commercialization milestone payments under the terms of the Tissue Regeneration License Agreement, which have been recorded to research and development expense.

Under the terms of the Tissue Regeneration License Agreement, the Company’s future commitments include:

•

A one-time $300 payment upon approval of an eligible product by the FDA;

•

An annual minimum non-refundable royalty fee of $10 for the life of the license that may be used to offset up to 50% of each earned royalty described below; and

•

Low single digit royalties on net sales.

Honeycomb License

In March 2013, the Company entered into a license agreement with Koken Co., Ltd. (“Koken”) and paid a fee for a non-exclusive, non-transferable and non-sublicensable right to use its know-how related to the process for manufacturing atelocollagen honeycomb sponge materials, which is used in scaffolds (the “Honeycomb License Agreement”). Under the terms of the Honeycomb License Agreement, future commitments will be based on the amount of materials supplied to the Company and may vary from period to period over the term of the agreement.

Plasmid License

In January 2008, the Company entered into an exclusive license agreement with Yeda Research and Development Co., Ltd. (“Yeda”) for rights relating to high level expression of heterologous proteins and plasmid p80 BS (the “Plasmid License Agreement”), which rights are jointly owned by Yeda and the Company. Under the terms of the Plasmid License Agreement, the Company was granted an exclusive worldwide license to manufacture, use and sell heterologous proteins and plasmid p80 BS.

The Company is required to pay Yeda a yearly, non-refundable license fee of $2, which is creditable against royalties payable by the Company to Yeda during the one-year period in which such fee was paid. Yeda is also entitled to low single digit royalties on net sales of the licensed products and on net sales for combination products (meaning the combination of the licensed product with at least one other active ingredient, material or medical device that would have a clinical effect if administered independently) and a low double digit percentage of all of the Company’s sublicensing receipts.

Tissue Processor Sub-License

In December 2005, the Company entered into an exclusive agreement to sub-license certain technology from Purpose, Co. (“Purpose”), which is owned by a stockholder of the Company (“Sub-License Agreement”). Purpose entered into the original license agreement (“Original Agreement”) with Brigham and Women’s Hospital, Inc. (“Brigham and Women’s”) in August 2001. The Original Agreement shall remain in effect for the licensed patents owned by Brigham and Women’s unless extended or terminated as provided for in the agreement. The technology is to be used to develop, manufacture, use and sell licensed products that cultivate cell or tissue development. The Sub-License Agreement extends to the expiration date of the last to expire domestic or foreign patents covered by the agreement. As of September 30, 2015, the Company has paid an aggregate $941 over the term of the Sub-License Agreement in royalty and sub-license payments under the terms of the Sub-License Agreement, which was recorded to research and development expense in the condensed consolidated statements of operations.

The Sub-License Agreement was amended and restated in June 2012. Under the amended and restated agreement, the Company made Purpose the sole supplier of equipment the Company uses in its manufacturing processes, and granted Purpose distribution rights of the Company’s products for certain territories. In exchange, Purpose allowed for the use of its technology (owned or licensed) and manufactured and serviced exogenous tissue processors by the Company. Under the terms of the agreement, as amended, Purpose granted the Company (a) exclusive rights to all of Purpose’s technology (owned or licensed) related to the exogenous tissue processors, (b) continued supply of exogenous tissue processors during the Company’s clinical trials, and (c) rights to manufacture the exogenous tissue processors at any location the Company chooses. In exchange for such consideration, the Company granted Purpose an exclusive license in Japan for the use of all of the Company’s technology and made a payment of $250 to reimburse Purpose for development costs on a next generation tissue processer.

In addition to the above, the Company’s future commitments under the terms of the Original Agreement and Sub-License Agreement include:

•

A minimum non-refundable annual royalty fee of $20, for the life of the license;

•

$200 in potential milestone payments; and

•

Low single digit royalties on net sales of a licensed product.

The OCS Agreement

In connection with its research and development, the Company received grants from the Office of Chief Scientist of the Ministry of Industry and Trade in Israel (“OCS”) in the aggregate of $1,100 for funding the fibroblast growth factor (“FGF”) program. In consideration for this grant, the Company is committed to pay royalties at a rate of 3% to 5% of the sales of sponsored products developed using the grant money, up to the amount of the participation payments received. The Company committed to pay up to 100% of grants received plus interest according to the LIBOR interest rate if the sponsored product is produced in Israel. If the manufacturing of the sponsored product takes place outside of Israel, the royalties can increase up to, but no more than, 300% of grants received plus interest based on the LIBOR interest rate, depending on the percentage of the manufacturing of sponsored product that takes place outside of Israel.

Engineering Agreement

The Company entered into an agreement with a development corporation to purchase a multi-unit bioreactor system. Pursuant to the agreement, as of September 30, 2015, the Company has made payments of $377 with a remaining $190 due upon the Company’s acceptance of the system, which is expected in 2016.

Collagen Supply Agreement

In September 2015, the Company entered into an agreement with Collagen Solutions (UK) Limited (the “Supplier”) to purchase soluble collagen that meets specifications provided by the Company. The initial term of the agreement is three years and will automatically renew from year to year thereafter unless otherwise terminated with at least 180 days’ notice by either party. Pursuant to the agreement, starting 12 months after entering into the agreement, the Company will be required to order a minimum amount of material and/or services totaling $150 from the Supplier in each calendar year until the expiration of the initial term of the agreement. The Company is also committed to pay a non-refundable payment totaling $121 by the end of 2015. As of September 30, 2015, the Company has paid an aggregate $93 under the terms of the agreement. Payment of the remaining amount of $28 is expected to be paid in December 2015, which has been recorded to research and development expense as of September 30, 2015.

Warrants	9 Months Ended
Warrants	Sep. 30, 2015
Text Block [Abstract]
Warrants	6. WARRANTS Consulting Agreement Warrant In March 2015, in connection with a consulting agreement entered into for an interim chief financial officer, the Company issued a common stock warrant as compensation to the consulting firm. The warrant provides the holder with the right to purchase an aggregate of 7,398 shares of the Company’s common stock at a per share exercise price of $9.75, the closing price of the Company’s common stock on the date of issuance. The warrant vests and becomes exercisable in monthly installments over 24 months beginning March 31, 2015. The warrant expires on the tenth anniversary of issuance. The warrant is equity classified and accounted for using the fair value approach. The fair value of the warrant is estimated using the Black-Scholes option pricing model and is subject to re-measurement at each reporting period until the measurement date is reached. Expense is included in general and administrative expenses on a straight-line basis over the expected service period, which is the vesting period. Affiliates of an Advisor Warrant In connection with the issuance of the Series A Preferred on July 20, 2012, the Company issued a warrant to purchase its common stock to affiliates of an advisor. The warrant provides the holders with the right to purchase an aggregate of 161,977 shares of the Company’s common stock at a per share exercise price of $0.01. The warrants are exercisable, in whole or in part, immediately and may be exercised on a cashless basis. The warrants expire on the tenth anniversary of issuance. The fair value of the warrants of $117 was estimated using the Black-Scholes option pricing model and was recorded as a reduction to Series A Preferred and a credit to additional paid-in capital. On December 8, 2014, the Company completed its IPO and warrants for 5,839 shares of common stock were surrendered to partially settle the Other Liability and common stock was issued by the Company to Purpose for the warrant shares surrendered. As of September 30, 2015 and December 31, 2014, warrants to purchase an aggregate of 156,138 shares of the Company’s common stock at an exercise price of $0.01 are outstanding. Equipment Line of Credit Warrant On July 9, 2014, the Company entered into a loan and security agreement with Silicon Valley Bank, which provides for a line of credit to purchase equipment. The amount of the line of credit is up to an aggregate of $1,750 with an annual interest rate of 2.75% plus the greater of 3.25% and the prime rate at the date of each draw, and is payable in equal monthly installments over 36 months beginning six months after the funding date, which ranged from August 2014 to November 2014. In connection with entering into the loan and security agreement, the Company granted Silicon Valley Bank a warrant to purchase 6,566 shares of common stock at a per share exercise price of $7.99. The warrant is exercisable, in whole or in part, immediately and may be exercised on a cashless basis and expires on the tenth anniversary of issuance. The fair value of the warrant as of July 9, 2014 was estimated at $51 with the following inputs: (a) risk-free interest rate of 2.58%; (b) implied volatility of the Company’s common stock of 87%; (c) the expected term of 10 years. The fair value of the warrant was recorded as a debt issuance cost with a corresponding credit to additional paid-in capital.

Stock-Based Compensation

9 Months Ended

Sep. 30, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

7. STOCK-BASED COMPENSATION

Stock option activity under the Company’s 2012 Equity Incentive Plan (the “2012 Plan”) and 2013 Equity Incentive Plan (the “2013 Plan”) for the nine months ended September 30, 2015 is summarized as follows:


	Number of Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2014		537,683		$	6.19
Granted		863,722
Exercised		(53,458	)
Cancelled		(121,057	)

Outstanding at September 30, 2015		1,226,890		$	7.51		9.2	$	(4,361	)

Vested and expected to vest at September 30, 2015		1,131,524		$	7.47		9.2	$	(3,955	)

Exercisable at September 30, 2015		290,014		$	4.41		7.8	$	(125	)

As of September 30, 2015, the unrecognized compensation cost related to outstanding options was $4,438 and is expected to be recognized as expense over approximately 2.87 years. As of September 30, 2015, the weighted average grant date fair value of vested options was $3.67 and the weighted average grant date fair value of shares outstanding was $4.68.

The weighted average grant date fair value per share of employee option grants within the period was $3.22 and $7.29 for the three months ended September 30, 2015 and 2014, respectively, and $4.55 and $6.74 for the nine months ended September 30, 2015 and 2014, respectively.

Restricted stock awards under the 2012 Plan and 2013 Plan for the nine months ended September 30, 2015 are summarized as follows:


				Weighted- Average
	Number of			Grant Date
	Shares			Fair Value
Unvested at December 31, 2014		8,493		$	1.04
Vesting of restricted stock		(1,889	)

Unvested at September 30, 2015		6,604		$	1.00

As of September 30, 2015, the unrecognized compensation cost related to restricted stock awards was $5 and is expected to be recognized as expense over approximately 1.36 years.

Stock-Based Compensation Expense

The Company granted stock options to employees for the three months ended September 30, 2015 and 2014. The Company estimates the fair value of stock options as of the date of grant using the Black-Scholes option pricing model and restricted stock based on the stock price, with the exception of those stock options that included a market condition. The Company estimates the fair value of stock options that include a market condition using the Monte-Carlo model. Stock options and restricted stock issued to non-board member, non-employees are accounted for using the fair value approach and are subject to periodic revaluation over their vesting terms.

Stock-based compensation expense amounted to $362 and $168 for the three months ended September 30, 2015 and 2014, respectively, and $854 and $356 for the nine months ended September 30, 2015 and 2014, respectively.

The allocation of stock-based compensation for all options granted and restricted stock awards are as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Research and development	$	126	$	46	$	319	$	104
General and administrative		236		122		535		252

Total stock-based compensation expense	$	362	$	168	$	854	$	356

Stock-based compensation by award type is as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Stock options	$	361	$	167	$	851	$	353
Restricted stock		1		1		3		3

Total stock-based compensation expense	$	362	$	168	$	854	$	356

The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants were as follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2015			2014			2015			2014
Risk-free interest rate		1.73	%		1.78	%		1.67	%		1.83	%
Expected volatility		60.1	%		104.4	%		62.8	%		104.5	%
Expected term (in years)		6.08			6.08			6.04			6.08
Expected dividend yield		0.0	%		0.0	%		0.0	%		0.0	%

The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the non-employee stock option grants were as follows:


	Three months ended September 30,						Nine months ended September 30,
	2015			2014			2015			2014
Risk-free interest rate		1.79	%		0.95	%		1.66	%		1.07	%
Expected volatility		60.8	%		98.2	%		63.3	%		95.2	%
Expected term (in years)		7.48			2.97			5.81			2.72
Expected dividend yield		0.0	%		0.0	%		0.0	%		0.0	%

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	8. INCOME TAXES Deferred tax assets and deferred tax liabilities are recognized based on temporary differences between the financial reporting and tax basis of assets and liabilities using statutory rates. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all of the deferred tax assets will not be realized. Due to the uncertainty surrounding the realization of the favorable tax attributes in future tax returns, the Company has recorded a full valuation allowance against the Company’s otherwise recognizable net deferred tax assets. The Company has allocated its valuation allowance in accordance with the provisions of ASC 740, Income Taxes , which resulted in a non-current deferred tax asset of $1,053 and a current deferred tax liability of $1,053 as of September 30, 2015.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2015

Accounting Policies [Abstract]

Reclassifications

Reclassifications

Segment and Geographic Information

Segment and Geographic Information

Information about the Company’s operations in different geographic regions is presented in the tables below:


	September 30,		December 31,
	2015		2014
Long-lived assets:
United States	$	5,504	$	4,866
Israel		9		12

Total long-lived assets	$	5,513	$	4,878

Fair Value Measurements

Fair Value Measurements

Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date of identical, unrestricted assets.

Transfers are calculated on values as of the transfer date. There were no transfers between Levels 1, 2 and 3 during the nine months ended September 30, 2015 and 2014.

The Company has no liabilities classified as Level 3 that are measured by management at fair value on a quarterly basis as of September 30, 2015.

Cash and Cash Equivalents

Cash and Cash Equivalents

The money market funds are measured at fair value on a recurring basis based on quoted market prices.


					Significant		Significant
			Prices in		other		unobservable
			active markets		observable inputs		inputs
Description	Total		(Level 1)		(Level 2)		(Level 3)
September 30, 2015
Money market funds	$	31,750	$	31,750	$	—	$	—

	$	31,750	$	31,750	$	—	$	—
December 31, 2014
Money market funds	$	49,750	$	49,750	$	—

	$	49,750	$	49,750	$	—	$	—

Intangible Assets

Intangible Asset

As of September 30, 2015 and December 31, 2014, the Company’s intangible asset consists of acquired in-process research and development (“IPR&D”).

For the nine months ended September 30, 2015 and 2014, the Company determined that there were no triggering events indicating impairment of its IPR&D.

Intangible assets, net of accumulated impairment charges, are summarized as follows:


	As of September 30, 2015							As of December 31, 2014
			Accumulated			Net Book				Accumulated			Net Book
	Cost		Impairment			Value		Cost		Impairment			Value
IPR&D	$	630	$	(120	)	$	510	$	630	$	(120	)	$	510

	$	630	$	(120	)	$	510	$	630	$	(120	)	$	510

Stock-Based Compensation

Stock-Based Compensation

Recent Accounting Pronouncements

Recent Accounting Pronouncements

- Definition

Disclosure of accounting policy for cash and cash equivalents, including the policy for determining which items are treated as cash equivalents. Other information that may be disclosed includes (1) the nature of any restrictions on the entity's use of its cash and cash equivalents, (2) whether the entity's cash and cash equivalents are insured or expose the entity to credit risk, (3) the classification of any negative balance accounts (overdrafts), and (4) the carrying basis of cash equivalents (for example, at cost) and whether the carrying amount of cash equivalents approximates fair value.

+ References + Details

Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2015

Accounting Policies [Abstract]

Summary of Operations in Different Geographic Regions

Information about the Company’s operations in different geographic regions is presented in the tables below:


	September 30,		December 31,
	2015		2014
Long-lived assets:
United States	$	5,504	$	4,866
Israel		9		12

Total long-lived assets	$	5,513	$	4,878

Summary of Cash Equivalents Measured at Fair Value on Recurring Basis

The money market funds are measured at fair value on a recurring basis based on quoted market prices.


					Significant		Significant
			Prices in		other		unobservable
			active markets		observable inputs		inputs
Description	Total		(Level 1)		(Level 2)		(Level 3)
September 30, 2015
Money market funds	$	31,750	$	31,750	$	—	$	—

	$	31,750	$	31,750	$	—	$	—
December 31, 2014
Money market funds	$	49,750	$	49,750	$	—

	$	49,750	$	49,750	$	—	$	—

Summary of Intangible Assets, Net of Accumulated Impairment Charges

Intangible assets, net of accumulated impairment charges, are summarized as follows:


	As of September 30, 2015							As of December 31, 2014
			Accumulated			Net Book				Accumulated			Net Book
	Cost		Impairment			Value		Cost		Impairment			Value
IPR&D	$	630	$	(120	)	$	510	$	630	$	(120	)	$	510

	$	630	$	(120	)	$	510	$	630	$	(120	)	$	510

Loss Per Common Share (Tables)

9 Months Ended

Sep. 30, 2015

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share


	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Convertible redeemable preferred stock and dividends		—		4,558,483		—		4,558,483
Restricted stock and options to purchase common stock		1,233,494		553,982		1,233,494		553,982
Warrants exercisable into common stock		170,102		168,543		170,102		168,543

Property and Equipment (Tables)

9 Months Ended

Sep. 30, 2015

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment

Property and equipment consisted of the following:


	September 30,			December 31,
	2015			2014
Office equipment	$	531		$	467
Laboratory equipment		4,292			2,978
Leasehold improvements		7,682			7,503
Construction in progress		469			270
Software		96			35

Total property and equipment		13,070			11,253
Less: accumulated depreciation		(7,557	)		(6,375	)

Property and equipment, net	$	5,513		$	4,878

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock Option Activity Under the 2012 and 2013 Plans


	Number of Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2014		537,683		$	6.19
Granted		863,722
Exercised		(53,458	)
Cancelled		(121,057	)

Outstanding at September 30, 2015		1,226,890		$	7.51		9.2	$	(4,361	)

Vested and expected to vest at September 30, 2015		1,131,524		$	7.47		9.2	$	(3,955	)

Exercisable at September 30, 2015		290,014		$	4.41		7.8	$	(125	)

Schedule of Restricted Stock Awards Under the 2012 and 2013 Plans

Restricted stock awards under the 2012 Plan and 2013 Plan for the nine months ended September 30, 2015 are summarized as follows:


				Weighted- Average
	Number of			Grant Date
	Shares			Fair Value
Unvested at December 31, 2014		8,493		$	1.04
Vesting of restricted stock		(1,889	)

Unvested at September 30, 2015		6,604		$	1.00

Summary of Stock-Based Compensation for All Options Granted and Restricted Stock Awards

The allocation of stock-based compensation for all options granted and restricted stock awards are as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Research and development	$	126	$	46	$	319	$	104
General and administrative		236		122		535		252

Total stock-based compensation expense	$	362	$	168	$	854	$	356

Summary of Stock-Based Compensation by Award

Stock-based compensation by award type is as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Stock options	$	361	$	167	$	851	$	353
Restricted stock		1		1		3		3

Total stock-based compensation expense	$	362	$	168	$	854	$	356

Summary of Weighted-Average Assumptions Used in the Black-Scholes Option Pricing Model to Determine the Fair Value of the Employee Stock Option Grants

The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants were as follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2015			2014			2015			2014
Risk-free interest rate		1.73	%		1.78	%		1.67	%		1.83	%
Expected volatility		60.1	%		104.4	%		62.8	%		104.5	%
Expected term (in years)		6.08			6.08			6.04			6.08
Expected dividend yield		0.0	%		0.0	%		0.0	%		0.0	%

Summary of Weighted-Average Assumptions Used in the Black-Scholes Option Pricing Model to Determine the Fair Value of the Non-Employee Stock Option Grants

The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the non-employee stock option grants were as follows:


	Three months ended September 30,						Nine months ended September 30,
	2015			2014			2015			2014
Risk-free interest rate		1.79	%		0.95	%		1.66	%		1.07	%
Expected volatility		60.8	%		98.2	%		63.3	%		95.2	%
Expected term (in years)		7.48			2.97			5.81			2.72
Expected dividend yield		0.0	%		0.0	%		0.0	%		0.0	%

Nature of Business - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jan. 06, 2015	Dec. 08, 2014	Sep. 30, 2015	Dec. 31, 2014
Nature Of Business And Basis Of Presentation [Line Items]
Gross proceeds from initial public offering		$ 70,115
Net proceeds from initial public offering		$ 61,277
Conversion of redeemable preferred stock and accrued dividends		5,158,407
Net exercise of warrants, shares		44,531	156,138	156,138
Surrender of warrant to satisfy other liability		5,839
Additional paid-in capital			$ 193,260	$ 187,620
Common stock, shares authorized		100,000,000	100,000,000	100,000,000
Preferred stock shares authorized		10,000,000	10,000,000	10,000,000
IPO [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Sale of common stock shares		5,909,091
Initial public offering price per share		$ 11.00
Gross proceeds from initial public offering		$ 65,000
Convertible notes payable to common stock		$ 11,100
Accrued interest to common stock		1,009,115
Over-Allotment Option [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Sale of common stock shares	465,000
Initial public offering price per share	$ 11.00
Gross proceeds from initial public offering	$ 5,115
Warrant Liability [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Additional paid-in capital		$ 490
Other Liability [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Additional paid-in capital		$ 612

Summary of Significant Accounting Policies - Summary of Operations in Different Geographic Regions (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Long-lived assets	$ 5,513	$ 4,878
United States [Member]
Segment Reporting Information [Line Items]
Long-lived assets	5,504	4,866
Israel [Member]
Segment Reporting Information [Line Items]
Long-lived assets	$ 9	$ 12

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents, fair value	$ 31,750,000		$ 49,750,000
IPR&D [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment of intangible assets	0	$ 0
Significant Unobservable Inputs (Level 3) [Member]
Summary Of Significant Accounting Policies [Line Items]
Assets, fair value disclosure, recurring	0		0
Liabilities, fair value disclosure, recurring	0		0
Liabilities, fair value disclosure	0
Prices in Active Markets (Level 1) [Member]
Summary Of Significant Accounting Policies [Line Items]
Assets, fair value disclosure, recurring	0		0
Liabilities, fair value disclosure, recurring	0		0
Cash and cash equivalents, fair value	31,750,000		49,750,000
Significant Other Observable Inputs (Level 2) [Member]
Summary Of Significant Accounting Policies [Line Items]
Assets, fair value disclosure, recurring	0		0
Liabilities, fair value disclosure, recurring	0		0
Cash Deposits [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents, fair value	5,973,000
Money Market Funds [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents, fair value	31,750,000		49,750,000
Money Market Funds [Member] \| Prices in Active Markets (Level 1) [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents, fair value	$ 31,750,000		$ 49,750,000

Summary of Significant Accounting Policies - Summary of Cash Equivalents Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, fair value	$ 31,750	$ 49,750
Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, fair value	31,750	49,750
Prices in Active Markets (Level 1) [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, fair value	31,750	49,750
Prices in Active Markets (Level 1) [Member] \| Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents, fair value	$ 31,750	$ 49,750

Summary of Significant Accounting Policies - Summary of Intangible Assets, Net of Accumulated Impairment Charges (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Cost	$ 630	$ 630
Accumulated Impairment	(120)	(120)
Net Book Value	510	510
IPR&D [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	630	630
Accumulated Impairment	(120)	(120)
Net Book Value	$ 510	$ 510

Loss Per Common Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Convertible Redeemable Preferred Stock and Dividends [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share		4,558,483		4,558,483
Restricted Stock and Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	1,233,494	553,982	1,233,494	553,982
Warrants Exercisable into Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	170,102	168,543	170,102	168,543

Loss Per Common Share - Additional Information (Detail) - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015
Earnings Per Share [Abstract]
Instruments outstanding	0	0

Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 13,070	$ 11,253
Less: accumulated depreciation	(7,557)	(6,375)
Property and equipment, net	5,513	4,878
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	531	467
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	4,292	2,978
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	7,682	7,503
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	469	270
Software [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 96	$ 35

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 414	$ 169	$ 1,182	$ 482

Commitments and Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Loss Contingencies [Line Items]
Rent expense under operating lease agreements	$ 266,000	$ 275,000	$ 857,000	$ 608,000
Research and development expense	5,848,000	$ 13,237,000	$ 17,470,000	$ 21,280,000
Massachusetts [Member] \| Waltham [Member]
Loss Contingencies [Line Items]
Lease expiration period			2023
Hydrogel License Agreement [Member]
Loss Contingencies [Line Items]
Research and development expense			$ 3,200,000
One-time payment amount	3,000,000		3,000,000
Tissue Regeneration License Agreement [Member]
Loss Contingencies [Line Items]
Research and development expense			642,000
One-time payment amount	300,000		$ 300,000
Percentage of royalty offsetting			50.00%
Plasmid License Agreement [Member]
Loss Contingencies [Line Items]
Non-refundable license fee	2,000		$ 2,000
Maximum [Member] \| Waltham [Member]
Loss Contingencies [Line Items]
Construction allowance to total cost of tenant improvements			3,184,000
Maximum [Member] \| Lexington [Member]
Loss Contingencies [Line Items]
Construction allowance to total cost of tenant improvements			996,000
Minimum [Member] \| Tissue Regeneration License Agreement [Member]
Loss Contingencies [Line Items]
Non-refundable royalty fee			10,000
Tissue Processor Sub License Agreement [Member]
Loss Contingencies [Line Items]
Research and development expense			941,000
Reimbursement for development cost			250,000
Potential milestone payment	200,000		200,000
Tissue Processor Sub License Agreement [Member] \| Minimum [Member]
Loss Contingencies [Line Items]
Non-refundable royalty fee			20,000
OCS Agreement [Member]
Loss Contingencies [Line Items]
Accrued and received grants, aggregate	1,100,000		$ 1,100,000
OCS Agreement [Member] \| Maximum [Member]
Loss Contingencies [Line Items]
Royalties payment, rate			5.00%
Royalty payment percentage as percentage of grant received			300.00%
OCS Agreement [Member] \| Minimum [Member]
Loss Contingencies [Line Items]
Royalties payment, rate			3.00%
Royalty payment percentage as percentage of grant received			100.00%
Stand-By Letter of Credit [Member] \| Lexington [Member]
Loss Contingencies [Line Items]
Stand-by letter of credit maintained by company	137,000		$ 137,000		$ 137,000
Engineering Agreement [Member]
Loss Contingencies [Line Items]
Amount paid to suppliers			377,000
Purchase amount, remaining to be paid	190,000		190,000
Collagen Supply Agreement [Member]
Loss Contingencies [Line Items]
Amount paid to suppliers			93,000
Purchase amount, remaining to be paid	$ 28,000		28,000
Minimum amount of material and/or services			150,000
Non-refundable payment			$ 121,000
Initial term of the agreement			3 years
Supplier agreement description			The initial term of the agreement is three years and will automatically renew from year to year thereafter unless otherwise terminated with at least 180 days' notice by either party.

Warrants - Additional Information (Detail) - USD ($)				3 Months Ended	9 Months Ended
Warrants - Additional Information (Detail) - USD ($)	Dec. 08, 2014	Jul. 09, 2014	Jul. 20, 2012	Mar. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Class of Warrant or Right [Line Items]
Class of Warrants or right to purchase common stock	44,531				156,138	156,138
Class of Warrants or right to purchase common stock, exercise price					$ 0.01	$ 0.01
Warrants expiry period			10 years
Fair value of warrants			$ 117,000
Surrender of warrant to satisfy other liability	5,839
Silicon Valley Bank [Member]
Class of Warrant or Right [Line Items]
Class of Warrants or right to purchase common stock					6,566
Class of Warrants or right to purchase common stock, exercise price					$ 7.99
Warrants expiry period					10 years
Fair value of warrants		$ 51,000
Aggregate maximum amount of line of credit facility		$ 1,750,000
Line of credit facility, basis spread on variable rate		3.25%
Line of credit facility, interest rate, stated percentage		2.75%
Bank loan and security agreement, repayment period		36 months
Fair value of the warrants, risk free interest rate		2.58%
Fair value of the warrants, implied volatility		87.00%
Fair value of the warrants, expected term to liquidity		10 years
Series A Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Class of Warrants or right to purchase common stock			161,977
Class of Warrants or right to purchase common stock, exercise price			$ 0.01
Consulting Agreement Warrant [Member]
Class of Warrant or Right [Line Items]
Class of Warrants or right to purchase common stock				7,398
Class of Warrants or right to purchase common stock, exercise price				$ 9.75
Warrants exercisable period				24 months
Warrants expiry period				10 years

Stock-Based Compensation - Summary of Stock Option Activity Under the 2012 and 2013 Plans (Detail) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) $ / shares shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Options, Outstanding Beginning Balance	537,683
Number of Options, Granted	863,722
Exercised	(53,458)
Number of Options, Cancelled	(121,057)
Number of Options, Outstanding Ending Balance	1,226,890
Number of Options, Vested and expected to vest outstanding	1,131,524
Number of Options, Exercisable	290,014
Weighted Average Exercise Price, Outstanding Beginning Balance \| $ / shares	$ 6.19
Weighted Average Exercise Price, Granted \| $ / shares	0
Weighted Average Exercise Price, Cancelled \| $ / shares	0
Weighted Average Exercise Price, Outstanding Ending Balance \| $ / shares	7.51
Weighted Average Exercise Price, Vested and expected to vest outstanding \| $ / shares	7.47
Weighted Average Exercise Price, Exercisable \| $ / shares	$ 4.41
Weighted Average Remaining Contractual Term, Outstanding	9 years 2 months 12 days
Weighted Average Remaining Contractual Term, Vested and expected to vest outstanding	9 years 2 months 12 days
Weighted Average Remaining Contractual Term, Exercisable	7 years 9 months 18 days
Aggregate Intrinsic Value, Outstanding \| $	$ (4,361)
Aggregate Intrinsic Value, Vested and expected to vest outstanding \| $	(3,955)
Aggregate Intrinsic Value, Exercisable \| $	$ (125)

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to outstanding options	$ 4,438		$ 4,438
Weighted average grant date fair value of vested options			$ 3.67
Weighted average grant date fair value of shares outstanding	$ 4.68		4.68
Weighted average grant date fair value per share of employee option granted	$ 3.22	$ 7.29	$ 4.55	$ 6.74
Stock-based compensation expense	$ 362	$ 168	$ 854	$ 356
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, recognition period			2 years 10 months 13 days
Stock-based compensation expense	361	167	$ 851	353
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, recognition period			1 year 4 months 10 days
Unrecognized compensation cost related to restricted stock awards	5		$ 5
Stock-based compensation expense	$ 1	$ 1	$ 3	$ 3

Stock-Based Compensation - Schedule of Restricted Stock Awards Under the 2012 and 2013 Plans (Detail) - Restricted Stock [Member]	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, Unvested beginning balance	8,493
Vesting of restricted stock	(1,889)
Number of shares, Unvested ending balance	6,604
Weighted-average grant date fair value, Unvested beginning balance \| $ / shares	$ 1.04
Weighted-average grant date fair value, Unvested ending balance \| $ / shares	$ 1.00

Stock-Based Compensation - Summary of Stock-Based Compensation for all Options Granted and Restricted Stock Awards (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 362	$ 168	$ 854	$ 356
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	126	46	319	104
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 236	$ 122	$ 535	$ 252

Stock-Based Compensation - Summary of Stock-Based Compensation by Award (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 362	$ 168	$ 854	$ 356
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	361	167	851	353
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1	$ 1	$ 3	$ 3

Stock-Based Compensation - Summary of Weighted-Average Assumptions Used in the Black-Scholes Option Pricing Model to Determine the Fair Value of the Employee Stock Option Grants (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Risk-free interest rate	1.73%	1.78%	1.67%	1.83%
Expected volatility	60.10%	104.40%	62.80%	104.50%
Expected term (in years)	6 years 29 days	6 years 29 days	6 years 15 days	6 years 29 days
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

Stock-Based Compensation - Summary of Weighted-Average Assumptions Used in the Black-Scholes Option Pricing Model to Determine the Fair Value of the Non-Employee Stock Option Grants (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Goods and Nonemployee Services Transaction [Abstract]
Risk-free interest rate	1.79%	0.95%	1.66%	1.07%
Expected volatility	60.80%	98.20%	63.30%	95.20%
Expected term (in years)	7 years 5 months 23 days	2 years 11 months 19 days	5 years 9 months 22 days	2 years 8 months 19 days
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Noncurrent deferred tax assets, net	$ 1,053	$ 651
Current deferred tax liability, net	$ 1,053	$ 651