Athersys, Inc / New (ATHXQ) 10-K 11 Mar 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Mar. 08, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	ATHX
Entity Registrant Name	ATHERSYS, INC / NEW
Entity Central Index Key	1,368,148
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		83,720,154
Entity Public Float			$ 95.6

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 23,027	$ 26,127
Accounts receivable	361	694
Prepaid expenses and other	429	427
Total current assets	23,817	27,248
Equipment, net	1,135	1,270
Deferred tax assets	177	200
Total assets	25,129	28,718
Current liabilities:
Accounts payable	2,702	2,767
Accrued compensation and related benefits	1,024	1,060
Accrued clinical trial costs	82	126
Accrued expenses	513	664
Note payable	190
Deferred revenue	245	75
Total current liabilities	4,756	4,692
Note payable		183
Warrant liabilities	649	2,948
Stockholders' equity:
Preferred stock, at stated value; 10,000,000 shares authorized, and no shares issued and outstanding at December 31, 2015 and December 31, 2014	0
Common stock, $0.001 par value; 150,000,000 shares authorized, 83,720,154 and 77,706,816 shares issued and outstanding at December 31, 2015 and December 31, 2014, respectively	84	78
Additional paid-in capital	322,582	307,337
Accumulated deficit	(302,942)	(286,520)
Total stockholders' equity	19,724	20,895
Total liabilities and stockholders' equity	$ 25,129	$ 28,718

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	83,720,154	77,706,816
Common stock, shares outstanding	83,720,154	77,706,816

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues
Contract revenue	$ 10,298	$ 286	$ 755
Grant revenue	1,650	1,337	1,683
Total revenues	11,948	1,623	2,438
Costs and expenses
Research and development (including stock compensation expense of $1,277, $1,158 and $639 in 2015, 2014 and 2013, respectively)	21,316	23,366	20,484
General and administrative (including stock compensation expense of $1,652, $1,447 and $884 in 2015, 2014 and 2013, respectively)	7,536	6,909	6,065
Depreciation	267	360	346
Total costs and expenses	29,119	30,635	26,895
Loss from operations	(17,171)	(29,012)	(24,457)
Income (expense) from change in fair value of warrants, net	772	6,591	(6,324)
Other (expense) income, net	(61)	86	38
Loss before income taxes	(16,460)	(22,335)	(30,743)
Income tax benefit	38	253
Net loss and comprehensive loss	$ (16,422)	$ (22,082)	$ (30,743)
Net loss per common share, basic	$ (0.20)	$ (0.29)	$ (0.53)
Weighted average shares outstanding, basic	82,143,610	76,954,503	57,674,833
Net loss per common share, diluted	$ (0.20)	$ (0.31)	$ (0.53)
Weighted average shares outstanding, diluted	82,851,091	78,541,447	57,674,833

Consolidated Statements of Ope5

Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Research and Development [Member]
Stock compensation expense	$ 1,277	$ 1,158	$ 639
General and Administrative [Member]
Stock compensation expense	$ 1,652	$ 1,447	$ 884

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2012	$ 20,247		$ 53	$ 253,889		$ (233,695)
Preferred stock shares, beginning balance at Dec. 31, 2012	0	0	0	0	0	0
Common stock beginning balance, shares at Dec. 31, 2012			53,058,632
Stock based compensation	$ 1,523			$ 1,523
Issuance of common stock from warrant exercises, Cost	797			797
Issuance of common stock from warrant exercises, Shares			397,826
Issuance of common stock and warrants, net of issuance costs	28,267		$ 17	28,113	$ 137
Issuance of common stock and warrants, net of issuance costs, Shares			16,899,999
Issuance of common stock under equity compensation plans	(270)		$ 1	1	(272)
Issuance of common stock under equity compensation plans, Shares			327,023
Net and comprehensive loss	(30,743)					$ (30,743)
Ending balance at Dec. 31, 2013	$ 19,821		$ 71	$ 284,323	$ (135)	$ (264,438)
Preferred stock shares, ending balance at Dec. 31, 2013	0	0	0	0	0	0
Common stock ending balance, shares at Dec. 31, 2013			70,683,480
Stock based compensation	$ 2,605			$ 2,605
Issuance of common stock from warrant exercises, Cost	938		$ 1	868	$ 69
Issuance of common stock from warrant exercises, Shares			928,924
Issuance of common stock and warrants, net of issuance costs	20,061		$ 5	19,698	358
Issuance of common stock and warrants, net of issuance costs, Shares			5,250,000
Issuance of common stock under equity compensation plans	(448)		$ 1	(157)	$ (292)
Issuance of common stock under equity compensation plans, Shares			844,412
Net and comprehensive loss	(22,082)					$ (22,082)
Ending balance at Dec. 31, 2014	$ 20,895		$ 78	$ 307,337		$ (286,520)
Preferred stock shares, ending balance at Dec. 31, 2014	0	0	0	0	0	0
Common stock ending balance, shares at Dec. 31, 2014	77,706,816		77,706,816
Stock based compensation	$ 2,929			$ 2,929
Issuance of common stock from warrant exercises, Cost	976		$ 1	975
Issuance of common stock from warrant exercises, Shares			966,184
Issuance of common stock and warrants, net of issuance costs	11,835		$ 4	11,831
Issuance of common stock and warrants, net of issuance costs, Shares			4,273,719
Issuance of common stock under equity compensation plans	$ (489)		$ 1	(490)
Issuance of common stock under equity compensation plans, Shares	2,661,835		773,435
Net and comprehensive loss	$ (16,422)					$ (16,422)
Ending balance at Dec. 31, 2015	$ 19,724		$ 84	$ 322,582		$ (302,942)
Preferred stock shares, ending balance at Dec. 31, 2015	0	0	0	0	0	0
Common stock ending balance, shares at Dec. 31, 2015	83,720,154		83,720,154

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (16,422)	$ (22,082)	$ (30,743)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	267	360	346
Stock-based compensation	2,929	2,605	1,523
Deferred tax benefit	23	(200)
Change in fair value of warrant liabilities	(772)	(6,591)	6,324
Changes in operating assets and liabilities:
Accounts receivable	333	(174)	(30)
Prepaid expenses and other	4	(33)	(94)
Accounts payable and accrued expenses	(296)	335	(196)
Deferred revenue	170	(11)	86
Net cash used in operating activities	(13,764)	(25,791)	(22,784)
Investing activities
Purchases of equipment	(132)	(297)	(385)
Net cash used in investing activities	(132)	(297)	(385)
Financing activities
Proceeds from issuance of common stock and warrants, net	10,310	19,621	29,454
Proceeds from exercise of warrants	976	938	402
Purchase of treasury stock	(490)	(292)	(272)
Net cash provided by financing activities	10,796	20,267	29,584
(Decrease) increase in cash and cash equivalents	(3,100)	(5,821)	6,415
Cash and cash equivalents at beginning of year	26,127	31,948	25,533
Cash and cash equivalents at end of year	$ 23,027	$ 26,127	$ 31,948

Background

Background	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Background	A. Background We are an international biotechnology company that is focused primarily in the field of regenerative medicine and operate in one business segment. Our operations consist primarily of research and product development activities.

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Accounting Policies	B. Accounting Policies Principles of Consolidation The consolidated financial statements include our accounts and results of operations and those of our wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. Revenue Recognition Our license and collaboration agreementsmay contain multiple elements, including license and technology access fees, research and development funding, manufacturing revenue, cost-sharing, milestones and royalties. The deliverables under such an arrangement are evaluated under Accounting Standards Codification (“ASC”) 605-25, Multiple-Element Arrangements. As of December 31, 2015, we have recognized the full amount of license fees under our collaboration agreements as contract revenue under ASC 605-25, since the performance periods for our multiple element arrangements have concluded. This excludes the Healios collaboration that was entered into in 2016. For agreements entered into prior to January 1, 2011 and not materially modified thereafter (such as Pfizer and Bristol-Myers Squibb contract revenue), we continue to apply our prior accounting policy with respect to such arrangements. Under this policy, the deliverables under the arrangement are evaluated to assess whether they have standalone value and objective and reliable evidence of fair value, and if so, are accounted for as a single unit. We then recognize revenue for each unit based on the culmination of the earnings process under ASC 605-S25, issued as Staff Accounting Bulletin (“SAB”) Topic 13, and our estimated performance period for the single units of accounting based on the specific terms of each collaborative agreement. The performance period for such agreements has concluded. We recognize revenue from at-risk, performance milestones that are substantive in the period that the milestone is achieved, as defined in the respective contracts. Also included in contract revenue are license fees received from Bristol-Myers Squibb, which are specifically set forth in the license and collaboration agreement as amounts due to us based on our completion of certain tasks (e.g., delivery and acceptance of a cell line) and development milestones (e.g., clinical trial phases), and as such, are not based on estimates that are susceptible to change. Such amounts are invoiced and recorded as revenue as tasks are completed and as milestones are achieved. Similarly, grant revenue consists of funding under cost reimbursement programs primarily from federal and state sources for qualified research and development activities performed by us, and as such, are not based on estimates that are susceptible to change. Such amounts are invoiced (unless prepaid) and recorded as revenue as tasks are completed. We recognize revenue from royalties relating to the sale by a licensee of the licensed product. Royalty revenue is recognized on an accrual basis in accordance with the substance of the relevant agreement and based on the receipt from the licensee of the relevant information to enable calculation of the royalty due. Cash and Cash Equivalents We consider all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash equivalents are primarily invested in money market funds and commercial paper. The carrying amount of our cash equivalents approximates fair value due to the short maturity of the investments. Research and Development Research and development expenditures, which consist primarily of costs associated with external clinical and preclinical study fees, manufacturing costs, salaries and related personnel costs, legal expenses resulting from intellectual property application processes, and laboratory supply and reagent costs, including direct and allocated overhead expenses, are charged to expense as incurred. Collaborative Arrangements Collaborative arrangements that involve cost or future profit sharing are reviewed to determine the nature of the arrangement and the nature of the collaborative parties’ businesses. The arrangements are also reviewed to determine if one party has sole or primary responsibility for an activity, or whether the parties have shared responsibility for the activity. If responsibility for an activity is shared and there is no principal party, then the related costs of that activity are recognized by us on a net basis in the statement of operations (e.g., total cost less reimbursement from collaborator). If we are deemed to be the principal party for an activity, then the costs and revenues associated with that activity are recognized on a gross basis in the statement of operations. The accounting may be susceptible to change if the nature of a collaborator’s business changes. Currently, we have no collaborations accounted for on a net basis. Clinical Trial Costs Clinical trial costs are accrued based on work performed by outside contractors that manage and perform the trials, and that manufacture clinical product. We obtain initial estimates of total costs based on enrollment of subjects, project management estimates, manufacturing estimates and other activities. Actual costs are typically charged to us and recognized as the tasks are completed by the contractor, and if we are invoiced based on progress payments as opposed to actual costs, we develop estimates of work completed to date. Accrued clinical trial costs may be subject to revisions as clinical trials progress, and any revisions are recorded in the period in which the facts that give rise to the revisions become known. Royalties We may be required to make future royalty payments to certain parties based on product sales under license agreements. We did not pay any royalties during the three-year period ended December 31, 2015. Long-Lived Assets Equipment is stated at acquired cost less accumulated depreciation. Laboratory and office equipment are depreciated on the straight-line basis over the estimated useful lives (three to ten years). Leasehold improvements are amortized over the shorter of the lease term or estimated useful life. Long-lived assets are evaluated for impairment when events or changes in circumstances indicate that the carrying amount of the asset or related group of assets may not be recoverable. If the expected future undiscounted cash flows are less than the carrying amount of the asset, an impairment loss is recognized at that time. Measurement of impairment may be based upon appraisal, market value of similar assets or discounted cash flows. Patent Costs and Rights Costs of prosecuting and maintaining patents and patent rights are expensed as incurred. We have filed for broad intellectual property protection on our proprietary technologies. We currently have numerous United States and international patents and patent applications related to our technologies. Warrant Liabilities We account for common stock warrants as either liabilities or as equity instruments depending on the specific terms of the warrant agreements. Registered common stock warrants that could require cash settlement are accounted for as liabilities. We classify these warrant liabilities on the consolidated balance sheet as non-current liabilities. The warrant liabilities are revalued at fair value at each balance sheet date subsequent to the initial issuance. Changes in the fair market value of the warrants are reflected in the consolidated statement of operations as income or expense from change in fair value of warrants. Concentration of Credit Risk Our accounts receivable are generally comprised of amounts due from collaborators and granting authorities and are subject to concentration of credit risk due to the absence of a large number of customers. At December 31, 2015, the majority of our accounts receivable are due from granting authorities. We do not require collateral from these customers. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. Stock-Based Compensation We recognize stock-based compensation expense on the straight-line method and use a Black-Scholes option-pricing model to estimate the fair value of option awards. The expected term of options granted represent the period of time that option grants are expected to be outstanding. We use the “simplified” method to calculate the expected life of option grants given our limited history of exercise activity and determine volatility by using our historical stock volatility. The fair value of our restricted stock units are equal to the closing price of our common stock on the date of grant and is expensed over the vesting period on a straight-line basis. Estimates of fair value are not intended to predict actual future events or the value ultimately realized by persons that receive equity awards. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. If actual forfeitures vary from the estimate, we recognize the difference in compensation expense in the period the actual forfeitures occur or when options vest. All of the aforementioned estimates and assumptions are evaluated on a quarterly basis and may change as facts and circumstances warrant. Changes in these assumptions can materially affect the estimate of the fair value of our share-based payments and the related amount recognized in our financial statements. The following weighted-average input assumptions were used in determining the fair value of the Company’s stock options: December 31, 2015 2014 2013 Volatility 83.9% 104.0% 109.2% Risk-free interest rate 2.1% 2.1% 1.5% Expected life of option 6.14 years 6.09 years 6.14 years Expected dividend yield 0.0% 0.0% 0.0% Income Taxes Deferred tax liabilities and assets are determined based on the differences between the financial reporting and tax basis of assets and liabilities and are measured using the tax rate and laws currently in effect. We evaluate our deferred income taxes to determine if a valuation allowance should be established against the deferred tax assets or if the valuation allowance should be reduced based on consideration of all available evidence, both positive and negative, using a “more likely than not” standard. We had no liability for uncertain income tax positions as of December 31, 2015 and 2014. Our policy is to recognize potential accrued interest and penalties related to the liability for uncertain tax benefits, if applicable, in income tax expense. Net operating loss and credit carryforwards since inception remain open to examination by taxing authorities, and will for a period post utilization. Net Loss per Share Basic and diluted net loss per share have been computed using the weighted-average number of shares of common stock outstanding during the period. For each reporting period, we evaluate the income from our warrant liabilities and consider whether it results in a potentially dilutive effect to net loss per share. For the years ended December 31, 2015 and 2014, we had such a dilutive effect related to our warrants with an exercise price of $1.01, which are included in the table below. Any such warrants are then omitted from the subsequent following table of instruments that were excluded from the calculation of diluted net loss per share. The table below reconciles the net loss and the number of shares used to calculate basic and diluted net loss per share for the years ended December 31, 2015, 2014 and 2013, in thousands. Year ended December 31, 2015 2014 2013 Numerator: Net loss and comprehensive loss $ (16,422 ) $ (22,082 ) $ (30,743 ) Less: income from change in fair value of warrants (332 ) (2,141 ) — Net loss attributable to common stockholders used to calculate diluted net loss per share $ (16,754 ) $ (24,223 ) $ (30,743 ) Denominator: Weighted-average shares outstanding - basic 82,144 76,955 57,675 Potentially dilutive common shares outstanding: Warrants 707 1,586 — Weighted-average shares used to calculate diluted net loss per share 82,851 78,541 57,675 Basic – net loss per share $ (0.20 ) $ (0.29 ) $ (0.53 ) Dilutive – net loss per share $ (0.20 ) $ (0.31 ) $ (0.53 ) We have outstanding options, restricted stock units and warrants that are not used in the calculation of diluted net loss per share because to do so would be antidilutive. The following instruments were excluded from the calculation of diluted net loss per share because their effects would be antidilutive: Year ended December 31, 2015 2014 2013 Stock options 7,052,642 6,383,457 5,129,579 Restricted stock units 1,069,100 1,889,267 2,449,346 Warrants 2,810,000 6,310,000 8,909,027 10,931,742 14,582,724 16,487,952 Reclassifications Certain prior year amounts have been reclassfied to conform with current year presentations. Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements - Going Concern, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes ,

Equipment

Equipment	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Equipment	C. Equipment December 31, Equipment consists of (in thousands): 2015 2014 Laboratory equipment $ 6,232 $ 6,162 Office equipment and leasehold improvements 2,691 2,849 8,923 9,011 Accumulated depreciation (7,788 ) (7,741 ) $ 1,135 $ 1,270 In 2015 and 2014, we disposed of approximately $0.2 million and $0.8 million, respectively, of obsolete laboratory equipment, office equipment and leasehold improvements, all of which was fully depreciated.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2015
Investments, All Other Investments [Abstract]
Financial Instruments	D. Financial Instruments Fair Value Measurements We classify the inputs used to measure fair value into the following hierarchy: Level 1 Unadjusted quoted prices in active markets for identical assets or liabilities. Level 2 Unadjusted quoted prices in active markets for similar assets or liabilities, or unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs other than quoted prices that are observable for the asset or liability. Level 3 Unobservable inputs for the asset or liability. The following table provides a summary of the financial assets and liabilities measured at fair value on a recurring basis as follows: (in thousands): Fair Value Measurements at December 31, 2015 Using Description Balance as of Quoted Prices in Active Significant Other Significant Warrant liabilities $ 649 $ — $ — $ 649 Fair Value Measurements at December 31, 2014 Using Description Balance as of Quoted Prices in Active Significant Other Significant Warrant liabilities $ 2,948 $ — $ — $ 2,948 We review and reassess the fair value hierarchy classifications on a quarterly basis. Changes from one quarter to the next related to the observability of inputs in a fair value measurement may result in a reclassification between fair value hierarchy levels. There were no reclassifications for all periods presented. The estimated fair value of warrants accounted for as liabilities, representing a level 3 fair value measure, was determined on the issuance date and subsequently marked to market at each financial reporting date. We use the Black-Scholes valuation model to value the warrant liabilities at fair value. The fair value is estimated using the expected volatility based on our historical volatility for warrants issued after January 1, 2013, or for warrants issued prior to 2013, using the historical volatilities of comparable companies from a representative peer group selected based on industry and market capitalization. The fair value of the warrants is determined using probability weighted-average assumptions, when appropriate. The following inputs were used at December 31, 2015: Expected Volatility Risk-Free Interest Rate Expected Life Warrants with one year or less remaining term 52.31% - 72.20% 0.14% – 0.49% 0.09 – 0.54 year Warrants with greater than one year remaining term 69.60% 0.65% 1.20 years A roll-forward of fair value measurements using significant unobservable inputs (Level 3) for the warrants is as follows (in thousands): Year ended December 31, 2015 Balance January 1, 2015 $ 2,948 Settlements from exercise (1,527 ) Income for the period (772 ) Balance December 31, 2015 $ 649 Financing Arrangements We lease office and laboratory space under operating leases. The lease for our corporate offices and laboratories began in 2000 and currently expires in March 2017, and we have the option to renew annually through 2019. Our rent is $267,000 per year and our rental rate has not changed since the lease inception in 2000. Also, we lease office and laboratory space for our Belgian subsidiary, which currently expires in July 2016 and includes options to renew annually through July 2022, with annual rent of approximately $174,000, subject to adjustments based on an inflationary index. We also have an option for additional space in Belgium that expires in June 2016. Aggregate rent expense was approximately $467,000, $517,000 and $491,000 in 2015, 2014 and 2013, respectively. The future annual minimum lease commitments at December 31, 2015 are approximately $373,000 for 2016 and $75,000 for 2017. In 2012, we entered into an arrangement with the Global Cardiovascular Innovation Center (“GCIC”), and the Cleveland Clinic Foundation in which we were entitled to proceeds of up to $500,000 in the form of a forgivable loan to fund certain preclinical work. Interest on the loan accrued at a fixed rate of 4.25% per annum and was added to the outstanding principal, and the loan carried an expiration date of March 31, 2016. In February 2016, the loan was forgiven according to its terms based on the achievement of certain milestones. As of December 31, 2015, the loan of $166,000 ($190,000 including accrued interest) was recorded as a current liability, and the income from forgiveness will be recognized in February 2016. The fair value of our note payable at December 31, 2015 is not determinable due to lack of marketability of the note payable. We paid no interest during the three years ended December 31, 2015.

Collaborations and Revenue Reco

Collaborations and Revenue Recognition	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborations and Revenue Recognition	E. Collaborations and Revenue Recognition Chugai In October 2015, we and Chugai Pharmaceutical Co. Ltd. (“Chugai”) agreed to terminate the License Agreement (the “Agreement”), dated February 28, 2015, between the parties, as a result of an inability to reach an agreement on the modification of the financial terms of the Agreement and on the development strategy, as proposed by Chugai, of our MultiStem ® Under the Agreement, we received a non-refundable, up-front cash payment of $10 million from Chugai, of which approximately $2.0 million was temporarily withheld by Japan taxing authorities and was refunded in September 2015. The $10 million upfront payment from Chugai was recorded as deferred revenue since we had concluded that the license grant did not have standalone value (as defined in ASC 605-25) at the inception of the arrangement. In connection with the termination and the parties having no further obligations under the Agreement, we recognized the $10 million upfront payment from Chugai as revenue in October 2015. Pfizer In 2009, we entered into a collaboration with Pfizer Inc. (“Pfizer”) to develop and commercialize our MultiStem product candidate to treat inflammatory bowel disease for the worldwide market on an exclusive basis. In addition, Pfizer conducted a Phase 2 clinical study exploring the potential of MultiStem cell therapy to treat advanced and severe ulcerative colitis, and would be responsible for any subsequent development. Overall, the study results were disappointing, even though a single administration of the cell therapy may have had some short-term beneficial effects. Taking these results into account, following an internal portfolio review, Pfizer determined that it would not invest further in this program, as would be required by the collaboration, and notified us of this decision to terminate the license agreement effective in the third quarter of 2015. In connection with the termination, all rights that Pfizer had to the program reverted to us, and intellectual property generated through the collaboration is owned by us. RTI Surgical, Inc. In 2010, we entered into an agreement with RTI Surgical, Inc. (“RTI”) to develop and commercialize biologic implants using our technology for certain orthopedic applications in the bone graft substitutes market on an exclusive basis. Under the terms of the agreement, we received a non-refundable license fee in installments and performed certain services that were concluded in 2012, and we are eligible to receive cash payments upon the successful achievement of certain commercial milestones. We evaluated the nature of the events triggering these contingent payments and concluded that these events are substantive and that revenue will be recognized in the period in which each underlying triggering event occurs. No milestone revenue has been recognized to date. In addition, we began receiving in 2014 tiered royalties on worldwide commercial sales of implants using our technologies based on a royalty rate starting in the mid-single digits and increasing into the mid-teens. Any royalties may be subject to a reduction if third-party payments for intellectual property rights are necessary or commercially desirable to permit the manufacture or sale of the product. Grant Award In 2015, we and Cell Therapy Catapult, a not-for-profit center focused on the development of the United Kingdom regenerative medicine industry, were each awarded a grant from Innovate UK in support of a Phase 2a clinical study evaluating the administration of MultiStem cell therapy to acute respiratory distress syndrome patients. The aggregate grant funding is expected to provide up to £2.0 million ($2.9 million based on the December 31, 2015 exchange rate) in support over the course of the study. Of the £2.0 million total award, our grant of £750,000 ($1.1 million based on the December 31, 2015 exchange rate) will be used primarily to fund the clinical product and related costs. Cell Therapy Catapult will use their grant proceeds of £1.25 million primarily to fund the clinical site costs and their service costs as study coordinators. We recognized approximately $130,000 of grant revenue in 2015 in connection with this grant.

Capitalization and Warrant Liab

Capitalization and Warrant Liability	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Capitalization and Warrant Liability	F. Capitalization and Warrant Liability Capitalization At both December 31, 2015 and 2014, we had 150.0 million shares of common stock and 10.0 million shares of undesignated preferred stock authorized. No shares of preferred stock have been issued as of December 31, 2015. The following shares of common stock were reserved for future issuance: December 31 2015 2014 Stock-based compensation plans 8,838,165 9,903,583 Warrants to purchase common stock — 2011 offering 1,310,000 1,310,000 Warrants to purchase common stock — 2012 offering 2,054,893 3,021,077 Warrants to purchase common stock — 2013 offering — 3,500,000 Warrants to purchase common stock — 2014 offering 1,500,000 1,500,000 13,703,058 19,234,660 As of December 31, 2015, the terms of our outstanding warrants to purchase shares of common stock with a weighted average price of $2.77 per share were as follows: Number of Underlying Shares Exercise Price Expiration 1,310,000 $3.55 February 2, 2016 2.054,893 $1.01 March 14, 2017 1,500,000 $4.50 July 15, 2016 4,864,893 In January 2014, we completed a registered direct offering generating net proceeds of approximately $18.8 million through the issuance of 5,000,000 shares of common stock and immediately exercisable warrants to purchase 1,500,000 shares of common stock with an exercise price of $4.50 per share that expire on July 15, 2016. The securities were sold in multiples of a fixed combination of one share of common stock and a warrant to purchase 0.30 shares of common stock at an offering price of $4.10 per fixed combination. In December 2013, we completed a registered direct offering generating net proceeds of approximately $18.4 million through the issuance of 10,000,000 shares of common stock and warrants to purchase 3,500,000 shares of common stock with an exercise price of $2.50 per share and an expiration date of March 31, 2015. The securities were sold in multiples of a fixed combination of one share of common stock and a warrant to purchase 0.35 shares of common stock at an offering price of $2.00 per fixed combination. In January 2015, we amended all of the December 2013 warrants to purchase 3,500,000 shares of common stock to increase the exercise price from $2.50 to $2.75 per share, and to extend the expiration date from March 31, 2015 to May 31, 2015. All 3,500,000 warrants expired unexercised in May 2015. Warrants associated with a March 2012 private placement financing with an exercise price of $1.01 per share have been exercised from time to time, and as of December 31, 2015, warrants to purchase an aggregate of 2,292,934 shares of common stock have been exercised to date, resulting in aggregate proceeds of approximately $2.3 million. Aspire Capital In November 2011, we entered into an equity purchase agreement with Aspire Capital Fund, LLC (“Aspire Capital”), which provided that Aspire Capital was committed to purchase up to an aggregate of $20.0 million of shares of our common stock over a two-year term, subject to our election to sell any such shares. As part of the agreement, Aspire Capital made an initial investment of $1.0 million in us and received 266,667 additional shares as compensation for its commitment. As of September 2013, we had sold all the remaining shares that were available under the equity facility, which was due to expire. In October 2013, we terminated the expiring 2011 equity purchase agreement and entered into a new 2013 equity purchase agreement with Aspire Capital to purchase up to an aggregate of $25.0 million of shares of our common stock over a new two-year period. The terms of the 2013 equity facility were similar to the previous arrangement, and we issued 333,333 shares of our common stock Aspire Capital as a commitment fee in October 2013 and filed a registration statement for the resale of 10,000,000 shares of common stock in connection with the new equity facility. During the years ended December 31, 2015 and 2014, we sold 4,023,719 and 250,000 shares, respectively, to Aspire Capital at average prices of $2.58 and $3.78 per share, respectively. As of the 2013 equity facility’s expiration in November 2015, we received proceeds of approximately $24.8 million in aggregate under the Aspire equity purchase agreements since its inception in 2011. In December 2015, we entered into a new 2015 equity purchase agreement with Aspire Capital to purchase up to an aggregate of $30.0 million of shares of our common stock over a new three-year period. The terms of the 2015 equity facility are similar to the previous arrangements, and we issued 250,000 shares of our common stock to Aspire Capital as a commitment fee in December 2015, which are accounted for as a cost of the offering, and filed a registration statement for the resale of 16,600,000 shares of common stock in connection with the new equity facility. Warrant Liabilities The warrants we issued in the January 2014 and December 2013 registered direct offerings contain(ed) a provision for a cash payment in the event that the shares are not delivered to the holder within two trading days. The cash payment equals $10 per day per $2,000 of warrant shares for each day late. The warrants we issued in both the March 2012 private placement and the February 2011 registered direct offering each contain(ed) a provision for net cash settlement in the event that there is a fundamental transaction (e.g., merger, sale of substantially all assets, tender offer, or share exchange). If a fundamental transaction occurs in which the consideration issued consists of all cash or stock in a non-public company, then the warrant holder has the option to receive cash equal to a Black Scholes value of the remaining unexercised portion of the warrant. Further, the March 2012 warrants include price protection in the event we sell stock below the exercise price, as defined, and the exercise price was reduced in February 2013 to $1.01 per share as a result of the October 2012 public offering. The warrants have been classified as liabilities, as opposed to equity, due to the potential adjustment to the exercise price that could result upon late delivery of the shares or potential cash settlement upon the occurrence of certain events as described above, and are recorded at their fair values at each balance sheet date

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	G. Stock-Based Compensation We have two incentive plans that authorized an aggregate of 11,500,000 shares of common stock for awards to employees, directors and consultants. These equity incentive plans authorize the issuance of equity-based compensation in the form of stock options, stock appreciation rights, restricted stock, restricted stock units, performance shares and units, and other stock-based awards to qualified employees, directors and consultants. As of December 31, 2015, a total of 2,661,835 shares of common stock have been issued under our equity incentive plans. As of December 31, 2015, a total of 716,423 shares were available for issuance under our equity compensation plans and stock-based awards to purchase 8,121,742 shares of common stock were outstanding. We recognized $2,929,000, $2,605,000 and $1,523,000 of stock-based compensation expense in 2015, 2014 and 2013, respectively. Stock Options The weighted average fair value of options granted in 2015, 2014 and 2013 was $0.94, $1.29 and $1.42 per share, respectively. The total fair value of options vested during 2015, 2014 and 2013 was $1,225,000, $940,000 and $585,000, respectively. At December 31, 2015, total unrecognized estimated compensation cost related to unvested stock options was approximately $2,245,000, which is expected to be recognized by mid-2019 using the straight-line method. The weighted average contractual life of unvested options at December 31, 2015 was 8.73 years. A summary of our stock option activity and related information is as follows: Number Weighted Outstanding January 1, 2013 4,058,184 $ 4.36 Granted 1,336,928 1.71 Exercised (1,312 ) 1.26 Forfeited / Terminated / Expired (264,221 ) 3.36 Outstanding December 31, 2013 5,129,579 3.72 Granted 1,420,800 1.68 Exercised (103,481 ) 1.75 Forfeited / Expired (63,441 ) 1.98 Outstanding December 31, 2014 6,383,457 3.31 Granted 1,215,296 1.31 Exercised (32,439 ) 1.60 Forfeited / Expired (513,672 ) 2.34 Outstanding December 31, 2015 7,052,642 $ 3.05 Vested during 2015 945,297 $ 1.62 Vested and exercisable at December 31, 2015 5,065,143 $ 3.65 December 31, 2015 Options Outstanding Options Vested and Exercisable Exercise Price Number Weighted Weighted Number Weighted Weighted $1.16 – 1.86 3,815,059 8.22 $ 1.55 1,841,560 7.66 $ 1.61 $2.09 – 3.84 244,583 5.14 $ 2.73 234,583 4.99 $ 2.73 $4.00 – 5.28 2,993,000 1.49 $ 4.98 2,989,000 1.48 $ 4.98 7,052,642 5,065,143 Restricted Stock Units A summary of our restricted stock unit activity and related information is as follows: Number Weighted Outstanding January 1, 2013 70,814 $ 1.86 Granted 2,851,964 1.71 Vested-common stock issued (486,359 ) 1.72 Forfeited/expired (5,073 ) 1.77 Outstanding December 31, 2013 2,449,346 1.71 Granted 460,112 1.65 Vested-common stock issued (1,013,446 ) 1.71 Forfeited/expired (6,745 ) 1.68 Outstanding December 31, 2014 1,889,267 1.70 Granted 455,776 1.28 Vested-common stock issued (1,032,979 ) 1.69 Forfeited/expired (242,964 ) 1.62 Outstanding December 31, 2015 1,069,100 $ 1.55 Vested/Issued cumulative at December 31, 2015 2,524,603 $ 1.71 The total fair value of restricted stock units vested during 2015, 2014 and 2013 was $1,773,000, $1,734,000 and $805,000, respectively. At December 31, 2015, total unrecognized estimated compensation cost related to unvested restricted stock units was approximately $1,533,000, which is expected to be recognized by mid-2019 using the straight-line method.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	H. Income Taxes At December 31, 2015, we had U.S. federal net operating loss and research and development tax credit carryforwards of approximately $102,261,000 and $4,277,000, respectively. Such operating losses and tax credits may be used to reduce future taxable income and tax liabilities and will expire at various dates between 2020 and 2036. We also had foreign net operating losses and foreign tax credit carryforwards of approximately $12,724,000 and $177,000, respectively. Such foreign operating losses do not expire and foreign tax credits will expire between 2016 and 2020. We also had state and city net operating loss carryforwards aggregating approximately $53,657,000. Such operating losses may be used to reduce future taxable income and tax liabilities and will expire at various dates between 2016 and 2036. The utilization of net operating loss and tax credit carryforwards generated prior to October 2012 (the “Section 382 Limited Attributes”) is substantially limited under Section 382 of the Internal Revenue Code of 1986, as amended, as a result of our equity offering that occurred in October 2012. U.S. federal net operating loss carryforwards of $65,633,000, research and development tax credits of $4,277,000, and state and local net operating loss carryforwards of $48,484,000 generated since 2012, as well as foreign net operating loss carryforwards of $12,724,000 and foreign tax credits of $177,000, are not subject to annual limitations. The Section 382 Limited Attributes may be used to reduce future taxable income and tax liabilities and will expire at various dates between 2016 and 2031. A reconciliation of the Federal statutory income tax rate to our effective tax rate is as follows: Percent of Income/(Loss) 2015 2014 Statutory Federal income tax rate 34.0 % 34.0 % State income taxes - net of Federal tax benefit 1.5 % 1.0 % Other permanent differences (3.5 %) 6.6 % Valuation allowance (40.2 %) (48.1 %) Research and development - U.S. 8.2 % 6.5 % Research and development - Foreign 0.2 % 0.9 % Effective tax rate for the year 0.2 % 0.9 % Significant components of our deferred tax assets are as follows (in thousands): December 31, 2015 2014 Net operating loss carryforwards $ 40,215 $ 34,657 Research and development credit carryforwards 4,454 3,134 Compensation expense 3,300 3,177 Other 1,129 1,084 Total deferred tax assets 49,098 42,052 Valuation allowance for deferred tax assets (48,921 ) (41,852 ) Net deferred tax assets $ 177 $ 200 Because of our cumulative losses, substantially all of the deferred tax assets have been fully offset by a valuation allowance. We have not paid income taxes for the three-year period ended December 31, 2015. In 2015 and 2014, we recognized a refundable tax benefit related to research and development credits associated with our foreign subsidiary.

Profit Sharing Plan and 401(k)

Profit Sharing Plan and 401(k) Plan	12 Months Ended
	Dec. 31, 2015
Postemployment Benefits [Abstract]
Profit Sharing Plan and 401(k) Plan	I. Profit Sharing Plan and 401(k) Plan We have a profit sharing and 401(k) plan that covers substantially all employees and allows for discretionary contributions by us. We make employer contributions to this plan, and the expense was approximately $314,000 in 2015, $284,000 in 2014, and $97,000 in 2013.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	J. Subsequent Events Healios On January 8, 2016, we entered into a license agreement with Healios K.K. (“Healios”) to develop and commercialize MultiStem cell therapy for ischemic stroke in Japan, and to provide Healios with access to Athersys’ proprietary MAPC technology for use in Healios’ “organ bud” program, initially for transplantation to treat liver disease or dysfunction. Under the agreement, Healios also obtained a right to expand the scope of the collaboration to include the exclusive rights to develop and commercialize MultiStem for the treatment of two additional indications in Japan, which include acute respiratory distress syndrome (“ARDS”) and another indication in the orthopedic area, and to include all indications for the organ bud program. Healios will develop and commercialize the MultiStem product in Japan, and we will provide the manufactured product to Healios. Under the terms of the agreement, we received an up-front cash payment of $15 million from Healios, and the collaboration can be expanded at Healios’ election. If Healios expands the collaboration, we will be entitled to receive a cash payment of $10 million. Healios may exercise its option to expand the collaboration by the date that is the later of (i) December 31, 2016 and (ii) the receipt of the initial results from Athersys’ ongoing ARDS clinical trial. For the ischemic stroke indication, we may also receive additional success-based development and regulatory approval milestones aggregating up to $30 million, as well as potential sales milestones of up to $185 million. We will also receive tiered royalties on product sales, starting in the low double digits and increasing incrementally on net sales levels. Additionally, we will receive payments for product supplied to Healios under a manufacturing supply agreement. If Healios exercises the option to expand to collaboration, we would be entitled to receive royalties from product sales and success-based development, regulatory approval and sales milestones, as well as payments for product supply for the two additional indications. For the organ bud product, we are entitled to receive a fractional royalty percentage on net sales of the organ bud products and will receive payments for manufactured product supplied to Healios under a manufacturing supply agreement. Additionally, we have a right of first negotiation for commercialization of an organ bud product in North America, with such right expiring on the later of (i) the date five years from the effective date of the agreement and (ii) 30 days after authorization to initiate clinical studies on an organ bud product under the first investigational new drug application or equivalent in Japan, North America or the European Union. To determine the appropriate accounting for the license agreement, we will evaluate the agreement and related facts and circumstances, focusing in particular on the rights and obligations of the arrangement. We have determined that our obligations under the agreement represent multiple deliverables. For deliverables with standalone value, our policy is to account for these as separate units of accounting We allocate the overall consideration of the arrangement that is fixed and determinable, excluding consideration that is contingent upon future deliverables, to the separate units of accounting based on estimated selling prices (as defined in ASC 605-25) of each deliverable.

Quarterly Financial Data (unaud

Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (unaudited)	K. Quarterly Financial Data (unaudited) The following table presents quarterly data for the years ended December 31, 2015 and 2014, in thousands, except per share data: 2015 First Second Third Fourth Full Year Revenues $ 731 $ 216 $ 396 $ 10,605 $ 11,948 Net income (loss) $ (12,482 ) $ (1,035 ) $ (6,497 ) $ 3,592 $ (16,422 ) Basic net income (loss) per common share $ (0.16 ) $ (0.01 ) $ (0.08 ) $ 0.04 $ (0.20 ) Diluted net loss per common share $ (0.16 ) $ (0.05 ) $ (0.08 ) $ 0.04 $ (0.20 ) 2014 First Second Third Fourth Full Year Revenues $ 707 $ 388 $ 293 $ 235 $ 1,623 Net income (loss) $ (11,484 ) $ 675 $ (4,719 ) $ (6,554 ) $ (22,082 ) Basic net income (loss) per common share $ (0.15 ) $ 0.01 $ (0.06 ) $ (0.08 ) $ (0.29 ) Diluted net loss per common share $ (0.15 ) $ (0.04 ) $ (0.08 ) $ (0.08 ) $ (0.31 ) Due to the effect of quarterly changes to outstanding shares of common stock and weightings, the annual loss per share will not necessarily equal the sum of the respective quarters.

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2015
Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	Schedule II – Valuation and Qualifying Accounts (In thousands) Balance at Additions Deductions Balance at Year Ended December 31, 2015 Deducted from asset accounts: Allowance for doubtful accounts- note receivable $ 352 $ 11 $ — $ 363 (A) Tax valuation allowances $ 41,852 $ 7,069 $ — $ 48,921 Total 2015 $ 42,204 $ 7,080 $ — $ 49,284 Year Ended December 31, 2014 Deducted from asset accounts: Allowance for doubtful accounts- note receivable $ 341 $ 11 $ — $ 352 (A) Tax valuation allowances $ 26,042 $ 15,810 $ — $ 41,852 Total 2014 $ 26,383 $ 15,812 $ — $ 42,204 Year Ended December 31, 2013 Deducted from asset accounts: Allowance for doubtful accounts- note receivable $ 330 $ 11 $ — $ 341 (A) Tax valuation allowances $ 34,222 $ 10,126 $ 18,306 (B) $ 26,042 Total 2013 $ 34,552 $ 10,137 $ 18,306 $ 26,383 (A) – Reserve on note receivable; fully-reserved. (B) – Substantially all of our deferred tax assets are offset by valuation allowances. All other schedules for which provision is made in the applicable accounting regulation of the SEC are not required under the related instructions or are inapplicable and, therefore, omitted.

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include our accounts and results of operations and those of our wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Revenue Recognition	Revenue Recognition Our license and collaboration agreements may contain multiple elements, including license and technology access fees, research and development funding, manufacturing revenue, cost-sharing, milestones and royalties. The deliverables under such an arrangement are evaluated under Accounting Standards Codification (“ASC”) 605-25, Multiple-Element Arrangements. As of December 31, 2015, we have recognized the full amount of license fees under our collaboration agreements as contract revenue under ASC 605-25, since the performance periods for our multiple element arrangements have concluded. This excludes the Healios collaboration that was entered into in 2016. For agreements entered into prior to January 1, 2011 and not materially modified thereafter (such as Pfizer and Bristol-Myers Squibb contract revenue), we continue to apply our prior accounting policy with respect to such arrangements. Under this policy, the deliverables under the arrangement are evaluated to assess whether they have standalone value and objective and reliable evidence of fair value, and if so, are accounted for as a single unit. We then recognize revenue for each unit based on the culmination of the earnings process under ASC 605-S25, issued as Staff Accounting Bulletin (“SAB”) Topic 13, and our estimated performance period for the single units of accounting based on the specific terms of each collaborative agreement. The performance period for such agreements has concluded. We recognize revenue from at-risk, performance milestones that are substantive in the period that the milestone is achieved, as defined in the respective contracts. Also included in contract revenue are license fees received from Bristol-Myers Squibb, which are specifically set forth in the license and collaboration agreement as amounts due to us based on our completion of certain tasks (e.g., delivery and acceptance of a cell line) and development milestones (e.g., clinical trial phases), and as such, are not based on estimates that are susceptible to change. Such amounts are invoiced and recorded as revenue as tasks are completed and as milestones are achieved. Similarly, grant revenue consists of funding under cost reimbursement programs primarily from federal and state sources for qualified research and development activities performed by us, and as such, are not based on estimates that are susceptible to change. Such amounts are invoiced (unless prepaid) and recorded as revenue as tasks are completed. We recognize revenue from royalties relating to the sale by a licensee of the licensed product. Royalty revenue is recognized on an accrual basis in accordance with the substance of the relevant agreement and based on the receipt from the licensee of the relevant information to enable calculation of the royalty due.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash equivalents are primarily invested in money market funds and commercial paper. The carrying amount of our cash equivalents approximates fair value due to the short maturity of the investments.
Research and Development	Research and Development Research and development expenditures, which consist primarily of costs associated with external clinical and preclinical study fees, manufacturing costs, salaries and related personnel costs, legal expenses resulting from intellectual property application processes, and laboratory supply and reagent costs, including direct and allocated overhead expenses, are charged to expense as incurred.
Collaborative Arrangements	Collaborative Arrangements Collaborative arrangements that involve cost or future profit sharing are reviewed to determine the nature of the arrangement and the nature of the collaborative parties’ businesses. The arrangements are also reviewed to determine if one party has sole or primary responsibility for an activity, or whether the parties have shared responsibility for the activity. If responsibility for an activity is shared and there is no principal party, then the related costs of that activity are recognized by us on a net basis in the statement of operations (e.g., total cost less reimbursement from collaborator). If we are deemed to be the principal party for an activity, then the costs and revenues associated with that activity are recognized on a gross basis in the statement of operations. The accounting may be susceptible to change if the nature of a collaborator’s business changes. Currently, we have no collaborations accounted for on a net basis.
Clinical Trial Costs	Clinical Trial Costs Clinical trial costs are accrued based on work performed by outside contractors that manage and perform the trials, and that manufacture clinical product. We obtain initial estimates of total costs based on enrollment of subjects, project management estimates, manufacturing estimates and other activities. Actual costs are typically charged to us and recognized as the tasks are completed by the contractor, and if we are invoiced based on progress payments as opposed to actual costs, we develop estimates of work completed to date. Accrued clinical trial costs may be subject to revisions as clinical trials progress, and any revisions are recorded in the period in which the facts that give rise to the revisions become known.
Royalties	Royalties We may be required to make future royalty payments to certain parties based on product sales under license agreements. We did not pay any royalties during the three-year period ended December 31, 2015.
Long-Lived Assets	Long-Lived Assets Equipment is stated at acquired cost less accumulated depreciation. Laboratory and office equipment are depreciated on the straight-line basis over the estimated useful lives (three to ten years). Leasehold improvements are amortized over the shorter of the lease term or estimated useful life. Long-lived assets are evaluated for impairment when events or changes in circumstances indicate that the carrying amount of the asset or related group of assets may not be recoverable. If the expected future undiscounted cash flows are less than the carrying amount of the asset, an impairment loss is recognized at that time. Measurement of impairment may be based upon appraisal, market value of similar assets or discounted cash flows.
Patent Costs and Rights	Patent Costs and Rights Costs of prosecuting and maintaining patents and patent rights are expensed as incurred. We have filed for broad intellectual property protection on our proprietary technologies. We currently have numerous United States and international patents and patent applications related to our technologies.
Warrant Liabilities	Warrant Liabilities We account for common stock warrants as either liabilities or as equity instruments depending on the specific terms of the warrant agreements. Registered common stock warrants that could require cash settlement are accounted for as liabilities. We classify these warrant liabilities on the consolidated balance sheet as non-current liabilities. The warrant liabilities are revalued at fair value at each balance sheet date subsequent to the initial issuance. Changes in the fair market value of the warrants are reflected in the consolidated statement of operations as income or expense from change in fair value of warrants.
Concentration of Credit Risk	Concentration of Credit Risk Our accounts receivable are generally comprised of amounts due from collaborators and granting authorities and are subject to concentration of credit risk due to the absence of a large number of customers. At December 31, 2015, the majority of our accounts receivable are due from granting authorities. We do not require collateral from these customers.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.
Stock-Based Compensation	Stock-Based Compensation We recognize stock-based compensation expense on the straight-line method and use a Black-Scholes option-pricing model to estimate the fair value of option awards. The expected term of options granted represent the period of time that option grants are expected to be outstanding. We use the “simplified” method to calculate the expected life of option grants given our limited history of exercise activity and determine volatility by using our historical stock volatility. The fair value of our restricted stock units are equal to the closing price of our common stock on the date of grant and is expensed over the vesting period on a straight-line basis. Estimates of fair value are not intended to predict actual future events or the value ultimately realized by persons that receive equity awards. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. If actual forfeitures vary from the estimate, we recognize the difference in compensation expense in the period the actual forfeitures occur or when options vest. All of the aforementioned estimates and assumptions are evaluated on a quarterly basis and may change as facts and circumstances warrant. Changes in these assumptions can materially affect the estimate of the fair value of our share-based payments and the related amount recognized in our financial statements. The following weighted-average input assumptions were used in determining the fair value of the Company’s stock options: December 31, 2015 2014 2013 Volatility 83.9% 104.0% 109.2% Risk-free interest rate 2.1% 2.1% 1.5% Expected life of option 6.14 years 6.09 years 6.14 years Expected dividend yield 0.0% 0.0% 0.0%
Income Taxes	Income Taxes Deferred tax liabilities and assets are determined based on the differences between the financial reporting and tax basis of assets and liabilities and are measured using the tax rate and laws currently in effect. We evaluate our deferred income taxes to determine if a valuation allowance should be established against the deferred tax assets or if the valuation allowance should be reduced based on consideration of all available evidence, both positive and negative, using a “more likely than not” standard. We had no liability for uncertain income tax positions as of December 31, 2015 and 2014. Our policy is to recognize potential accrued interest and penalties related to the liability for uncertain tax benefits, if applicable, in income tax expense. Net operating loss and credit carryforwards since inception remain open to examination by taxing authorities, and will for a period post utilization.
Net Loss per Share	Net Loss per Share Basic and diluted net loss per share have been computed using the weighted-average number of shares of common stock outstanding during the period. For each reporting period, we evaluate the income from our warrant liabilities and consider whether it results in a potentially dilutive effect to net loss per share. For the years ended December 31, 2015 and 2014, we had such a dilutive effect related to our warrants with an exercise price of $1.01, which are included in the table below. Any such warrants are then omitted from the subsequent following table of instruments that were excluded from the calculation of diluted net loss per share. The table below reconciles the net loss and the number of shares used to calculate basic and diluted net loss per share for the years ended December 31, 2015, 2014 and 2013, in thousands. Year ended December 31, 2015 2014 2013 Numerator: Net loss and comprehensive loss $ (16,422 ) $ (22,082 ) $ (30,743 ) Less: income from change in fair value of warrants (332 ) (2,141 ) — Net loss attributable to common stockholders used to calculate diluted net loss per share $ (16,754 ) $ (24,223 ) $ (30,743 ) Denominator: Weighted-average shares outstanding - basic 82,144 76,955 57,675 Potentially dilutive common shares outstanding: Warrants 707 1,586 — Weighted-average shares used to calculate diluted net loss per share 82,851 78,541 57,675 Basic – net loss per share $ (0.20 ) $ (0.29 ) $ (0.53 ) Dilutive – net loss per share $ (0.20 ) $ (0.31 ) $ (0.53 ) We have outstanding options, restricted stock units and warrants that are not used in the calculation of diluted net loss per share because to do so would be antidilutive. The following instruments were excluded from the calculation of diluted net loss per share because their effects would be antidilutive: Year ended December 31, 2015 2014 2013 Stock options 7,052,642 6,383,457 5,129,579 Restricted stock units 1,069,100 1,889,267 2,449,346 Warrants 2,810,000 6,310,000 8,909,027 10,931,742 14,582,724 16,487,952
Reclassifications	Reclassifications Certain prior year amounts have been reclassfied to conform with current year presentations.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements - Going Concern, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes ,

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Fair Value of Stock-Based Compensation Awards	The following weighted-average input assumptions were used in determining the fair value of the Company’s stock options: December 31, 2015 2014 2013 Volatility 83.9% 104.0% 109.2% Risk-free interest rate 2.1% 2.1% 1.5% Expected life of option 6.14 years 6.09 years 6.14 years Expected dividend yield 0.0% 0.0% 0.0%
Net Loss and Number of Shares Used to Calculate Basic and Diluted Net Loss Per Share	The table below reconciles the net loss and the number of shares used to calculate basic and diluted net loss per share for the years ended December 31, 2015, 2014 and 2013, in thousands. Year ended December 31, 2015 2014 2013 Numerator: Net loss and comprehensive loss $ (16,422 ) $ (22,082 ) $ (30,743 ) Less: income from change in fair value of warrants (332 ) (2,141 ) — Net loss attributable to common stockholders used to calculate diluted net loss per share $ (16,754 ) $ (24,223 ) $ (30,743 ) Denominator: Weighted-average shares outstanding - basic 82,144 76,955 57,675 Potentially dilutive common shares outstanding: Warrants 707 1,586 — Weighted-average shares used to calculate diluted net loss per share 82,851 78,541 57,675 Basic – net loss per share $ (0.20 ) $ (0.29 ) $ (0.53 ) Dilutive – net loss per share $ (0.20 ) $ (0.31 ) $ (0.53 )
Instruments Excluded from Calculation of Diluted Net Loss Per Share	The following instruments were excluded from the calculation of diluted net loss per share because their effects would be antidilutive: Year ended December 31, 2015 2014 2013 Stock options 7,052,642 6,383,457 5,129,579 Restricted stock units 1,069,100 1,889,267 2,449,346 Warrants 2,810,000 6,310,000 8,909,027 10,931,742 14,582,724 16,487,952

Equipment (Tables)

Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Equipment	December 31, Equipment consists of (in thousands): 2015 2014 Laboratory equipment $ 6,232 $ 6,162 Office equipment and leasehold improvements 2,691 2,849 8,923 9,011 Accumulated depreciation (7,788 ) (7,741 ) $ 1,135 $ 1,270

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Investments, All Other Investments [Abstract]
Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table provides a summary of the financial assets and liabilities measured at fair value on a recurring basis as follows: (in thousands): Fair Value Measurements at December 31, 2015 Using Description Balance as of Quoted Prices in Active Significant Other Significant Warrant liabilities $ 649 $ — $ — $ 649 Fair Value Measurements at December 31, 2014 Using Description Balance as of Quoted Prices in Active Significant Other Significant Warrant liabilities $ 2,948 $ — $ — $ 2,948
Fair Value of Warrants Based on Historical Volatilities	The following inputs were used at December 31, 2015: Expected Volatility Risk-Free Interest Rate Expected Life Warrants with one year or less remaining term 52.31% - 72.20% 0.14% – 0.49% 0.09 – 0.54 year Warrants with greater than one year remaining term 69.60% 0.65% 1.20 years
Roll-Forward of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) for Warrants	A roll-forward of fair value measurements using significant unobservable inputs (Level 3) for the warrants is as follows (in thousands): Year ended December 31, 2015 Balance January 1, 2015 $ 2,948 Settlements from exercise (1,527 ) Income for the period (772 ) Balance December 31, 2015 $ 649

Capitalization and Warrant Li24

Capitalization and Warrant Liability (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Common Stock Shares Reserved for Future Issuance	The following shares of common stock were reserved for future issuance: December 31 2015 2014 Stock-based compensation plans 8,838,165 9,903,583 Warrants to purchase common stock — 2011 offering 1,310,000 1,310,000 Warrants to purchase common stock — 2012 offering 2,054,893 3,021,077 Warrants to purchase common stock — 2013 offering — 3,500,000 Warrants to purchase common stock — 2014 offering 1,500,000 1,500,000 13,703,058 19,234,660
Outstanding Warrants to Purchase Shares of Common Stock	As of December 31, 2015, the terms of our outstanding warrants to purchase shares of common stock with a weighted average price of $2.77 per share were as follows: Number of Underlying Shares Exercise Price Expiration 1,310,000 $3.55 February 2, 2016 2.054,893 $1.01 March 14, 2017 1,500,000 $4.50 July 15, 2016 4,864,893

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Activity and Related Information	A summary of our stock option activity and related information is as follows: Number of Options Weighted Average Exercise Price Outstanding January 1, 2013 4,058,184 $ 4.36 Granted 1,336,928 1.71 Exercised (1,312 ) 1.26 Forfeited / Terminated / Expired (264,221 ) 3.36 Outstanding December 31, 2013 5,129,579 3.72 Granted 1,420,800 1.68 Exercised (103,481 ) 1.75 Forfeited / Expired (63,441 ) 1.98 Outstanding December 31, 2014 6,383,457 3.31 Granted 1,215,296 1.31 Exercised (32,439 ) 1.60 Forfeited / Expired (513,672 ) 2.34 Outstanding December 31, 2015 7,052,642 $ 3.05 Vested during 2015 945,297 $ 1.62 Vested and exercisable at December 31, 2015 5,065,143 $ 3.65
Summarizes Information Concerning Options Outstanding and Options Vested and Exercisable	December 31, 2015 Options Outstanding Options Vested and Exercisable Exercise Price Number Weighted Weighted Number Weighted Weighted $1.16 – 1.86 3,815,059 8.22 $ 1.55 1,841,560 7.66 $ 1.61 $2.09 – 3.84 244,583 5.14 $ 2.73 234,583 4.99 $ 2.73 $4.00 – 5.28 2,993,000 1.49 $ 4.98 2,989,000 1.48 $ 4.98 7,052,642 5,065,143
Summary of Restricted Stock Unit Activity and Related Information	A summary of our restricted stock unit activity and related information is as follows: Number of Restricted Stock Units Weighted Average Fair Value Outstanding January 1, 2013 70,814 $ 1.86 Granted 2,851,964 1.71 Vested-common stock issued (486,359 ) 1.72 Forfeited/expired (5,073 ) 1.77 Outstanding December 31, 2013 2,449,346 1.71 Granted 460,112 1.65 Vested-common stock issued (1,013,446 ) 1.71 Forfeited/expired (6,745 ) 1.68 Outstanding December 31, 2014 1,889,267 1.70 Granted 455,776 1.28 Vested-common stock issued (1,032,979 ) 1.69 Forfeited/expired (242,964 ) 1.62 Outstanding December 31, 2015 1,069,100 $ 1.55 Vested/Issued cumulative at December 31, 2015 2,524,603 $ 1.71

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Reconciliation of Federal Statutory Income Tax Rate to Effective Tax Rate	A reconciliation of the Federal statutory income tax rate to our effective tax rate is as follows: Percent of Income/(Loss) 2015 2014 Statutory Federal income tax rate 34.0 % 34.0 % State income taxes - net of Federal tax benefit 1.5 % 1.0 % Other permanent differences (3.5 %) 6.6 % Valuation allowance (40.2 %) (48.1 %) Research and development - U.S. 8.2 % 6.5 % Research and development - Foreign 0.2 % 0.9 % Effective tax rate for the year 0.2 % 0.9 %
Components of Deferred Tax Assets	Significant components of our deferred tax assets are as follows (in thousands): December 31, 2015 2014 Net operating loss carryforwards $ 40,215 $ 34,657 Research and development credit carryforwards 4,454 3,134 Compensation expense 3,300 3,177 Other 1,129 1,084 Total deferred tax assets 49,098 42,052 Valuation allowance for deferred tax assets (48,921 ) (41,852 ) Net deferred tax assets $ 177 $ 200

Quarterly Financial Data (una27

Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	The following table presents quarterly data for the years ended December 31, 2015 and 2014, in thousands, except per share data: 2015 First Second Third Fourth Full Year Revenues $ 731 $ 216 $ 396 $ 10,605 $ 11,948 Net income (loss) $ (12,482 ) $ (1,035 ) $ (6,497 ) $ 3,592 $ (16,422 ) Basic net income (loss) per common share $ (0.16 ) $ (0.01 ) $ (0.08 ) $ 0.04 $ (0.20 ) Diluted net loss per common share $ (0.16 ) $ (0.05 ) $ (0.08 ) $ 0.04 $ (0.20 ) 2014 First Second Third Fourth Full Year Revenues $ 707 $ 388 $ 293 $ 235 $ 1,623 Net income (loss) $ (11,484 ) $ 675 $ (4,719 ) $ (6,554 ) $ (22,082 ) Basic net income (loss) per common share $ (0.15 ) $ 0.01 $ (0.06 ) $ (0.08 ) $ (0.29 ) Diluted net loss per common share $ (0.15 ) $ (0.04 ) $ (0.08 ) $ (0.08 ) $ (0.31 )

Background - Additional Informa

Background - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015Segment
Accounting Policies [Abstract]
Number of business segments	1

Accounting Policies - Additiona

Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Jan. 31, 2015	Dec. 31, 2014	Jan. 31, 2014	Dec. 31, 2013	Feb. 28, 2013
Significant Accounting Policies [Line Items]
Liquid investments with a maturity	Three months or less
Payments for Royalties	$ 0
Liability for uncertain income tax	$ 0		$ 0
Warrants exercise price	$ 1.01		$ 1.01	$ 4.50		$ 1.01
Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of long-lived assets	3 years
Warrants exercise price					$ 2.50
Maximum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of long-lived assets	10 years
Warrants exercise price		$ 2.75

Accounting Policies - Fair Valu

Accounting Policies - Fair Value of Stock-Based Compensation Awards (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Volatility	83.90%	104.00%	109.20%
Risk-free interest rate	2.10%	2.10%	1.50%
Expected life of option	6 years 1 month 21 days	6 years 1 month 2 days	6 years 1 month 21 days
Expected dividend yield	0.00%	0.00%	0.00%

Accounting Policies - Net Loss

Accounting Policies - Net Loss and Number of Shares Used to Calculate Basic and Diluted Net Loss Per Share (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
Numerator:
Net loss and comprehensive loss									$ (16,422)	$ (22,082)	$ (30,743)
Less: income from change in fair value of warrants									(332)	(2,141)
Net loss attributable to common stockholders used to calculate diluted net loss per share									$ (16,754)	$ (24,223)	$ (30,743)
Denominator:
Weighted-average shares outstanding - basic									82,143,610	76,954,503	57,674,833
Potentially dilutive common shares outstanding:
Warrants									707,000	1,586,000
Weighted-average shares used to calculate diluted net loss per share									82,851,091	78,541,447	57,674,833
Basic - net loss per share	$ 0.04	$ (0.08)	$ (0.01)	$ (0.16)	$ (0.08)	$ (0.06)	$ 0.01	$ (0.15)	$ (0.20)	$ (0.29)	$ (0.53)
Dilutive - net loss per share	$ 0.04	$ (0.08)	$ (0.05)	$ (0.16)	$ (0.08)	$ (0.08)	$ (0.04)	$ (0.15)	$ (0.20)	$ (0.31)	$ (0.53)

Accounting Policies - Instrumen

Accounting Policies - Instruments Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	10,931,742	14,582,724	16,487,952
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	7,052,642	6,383,457	5,129,579
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	1,069,100	1,889,267	2,449,346
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	2,810,000	6,310,000	8,909,027

Equipment - Equipment (Detail)

Equipment - Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Equipment, Gross	$ 8,923	$ 9,011
Accumulated depreciation	(7,788)	(7,741)
Equipment, net	1,135	1,270
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Equipment, Gross	6,232	6,162
Office Equipment and Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Equipment, Gross	$ 2,691	$ 2,849

Equipment - Additional Informat

Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Disposal of obsolete equipment	$ 0.2	$ 0.8

Financial Instruments - Summary

Financial Instruments - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities	$ 649	$ 2,948
Fair Value Measurements, Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities	649	2,948
Fair Value Measurements, Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant liabilities	$ 649	$ 2,948

Financial Instruments - Fair Va

Financial Instruments - Fair Value of Warrants Based on Historical Volatilities (Detail)	12 Months Ended
	Dec. 31, 2015
Warrants With Greater Than One Year Remaining Term [Member]
Class of Warrant or Right [Line Items]
Expected Volatility	69.60%
Risk-Free Interest Rate	0.65%
Expected Life	1 year 2 months 12 days
Warrants With One Year or Less Remaining Term [Member] | Minimum [Member]
Class of Warrant or Right [Line Items]
Expected Volatility	52.31%
Risk-Free Interest Rate	0.14%
Expected Life	1 month 2 days
Warrants With One Year or Less Remaining Term [Member] | Maximum [Member]
Class of Warrant or Right [Line Items]
Expected Volatility	72.20%
Risk-Free Interest Rate	0.49%
Expected Life	6 months 15 days

Financial Instruments - Roll-Fo

Financial Instruments - Roll-Forward of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) for Warrants (Detail) - Outstanding Warrants [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Beginning Balance	$ 2,948
Settlements from exercise	(1,527)
Income for the period	(772)
Ending Balance	$ 649

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended			36 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Rent	$ 267,000
Lease expiration period	2017-03
Aggregate rent expense	$ 467,000	$ 517,000	$ 491,000
Future annual minimum lease commitments for 2016	373,000			$ 373,000
Future annual minimum lease commitments for 2017	75,000			75,000
Interest paid				$ 0
Belgium [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Rent	$ 174,000
Lease expiration period	2016-07
Lease expiration period, additional space in Belgium	2016-06

Collaborations and Revenue Re39

Collaborations and Revenue Recognition - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Sep. 30, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2015GBP (£)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Oct. 31, 2015USD ($)	Feb. 28, 2015USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expected grant revenue		$ 1,650,000		$ 1,337,000	$ 1,683,000
RTI Surgical Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Commercial milestone revenue		0
Chugai Collaboration [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Up-front cash payment received	$ 10,000,000					$ 10,000,000	$ 10,000,000
UNITED KINGDOM | Innovate UK [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expected grant revenue		2,900,000	£ 2,000,000
UNITED KINGDOM | Innovate UK [Member] | Clinical Product And Related Costs [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expected grant revenue		1,100,000	750,000
UNITED KINGDOM | Innovate UK [Member] | Clinical Site Costs and Service Costs [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expected grant revenue		$ 130,000	£ 1,250,000
National Tax Agency, Japan [Member] | Chugai Collaboration [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash withheld by tax authorities refunded	$ 2,000,000

Capitalization and Warrant Li40

Capitalization and Warrant Liability - Additional Information (Detail)	1 Months Ended						12 Months Ended
	May. 31, 2015shares	Jan. 31, 2015$ / sharesshares	Jan. 31, 2014USD ($)$ / sharesshares	Dec. 31, 2013USD ($)$ / sharesshares	Oct. 31, 2013USD ($)shares	Nov. 30, 2011USD ($)shares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)$ / sharesshares	Dec. 31, 2013USD ($)$ / sharesshares	Feb. 28, 2013$ / shares
Class of Warrant or Right [Line Items]
Common stock, shares authorized							150,000,000	150,000,000
Preferred stock, shares authorized							10,000,000	10,000,000
Preferred stock, shares issued							0	0
Common stock exercise price | $ / shares			$ 4.50				$ 1.01	$ 1.01		$ 1.01
Net proceeds through issuance of common stock | $			$ 18,800,000	$ 18,400,000
Issuance of common stock, new issues			5,000,000	10,000,000
Warrants issued to purchase common stock		3,500,000	1,500,000	3,500,000			2,292,934		3,500,000
Warrants exercise expiration date		May 31, 2015	Jul. 15, 2016	Mar. 31, 2015
Common stock per warrant conversion ratio			0.30	0.35
Common stock and warrant combined offering price | $ / shares			$ 4.10	$ 2
Warrants expired, unexercised	3,500,000
Proceeds from warrants exercise | $							$ 976,000	$ 938,000	$ 402,000
Terms of issuance of warrant demanding cash payments							The warrants we issued in the January 2014 and December 2013 registered direct offerings contain a provision for a cash payment in the event that the shares are not delivered to the holder within two trading days. The cash payment equals $10 per day per $2,000 of warrant shares for each day late.
Number of trading days to deliver shares under warrants provision							2 days
Value of warrants considered for cash payment for late delivery of shares | $							$ 2,000
Cash payment per day for warrants shares not delivered as per provision | $							$ 10
Minimum [Member]
Class of Warrant or Right [Line Items]
Common stock exercise price | $ / shares				$ 2.50					$ 2.50
Maximum [Member]
Class of Warrant or Right [Line Items]
Common stock exercise price | $ / shares		$ 2.75
Common Stock [Member]
Class of Warrant or Right [Line Items]
Common stock exercise price | $ / shares							$ 2.77
Issuance of common stock, new issues							4,273,719	5,250,000	16,899,999
Aspire [Member]
Class of Warrant or Right [Line Items]
Net proceeds through issuance of common stock | $							$ 24,800,000
Issuance of common stock, new issues							4,023,719	250,000
Equity purchase agreement, value | $					$ 25,000,000	$ 20,000,000	$ 30,000,000
Equity purchase agreement, term					2 years	2 years	3 years
Initial investment | $						$ 1,000,000
Common stock issued as commitment fees					333,333		250,000
Common stock registered for resale					10,000,000		16,600,000
Sale of additional shares at an average price | $ / shares							$ 2.58	$ 3.78
Aspire [Member] | Equity Purchase Agreement [Member]
Class of Warrant or Right [Line Items]
Common stock issuance (shares) under equity purchase agreement						266,667

Capitalization and Warrant Li41

Capitalization and Warrant Liability - Common Stock Shares Reserved for Future Issuance (Detail) - shares	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance	13,703,058	19,234,660
Stock-Based Compensation Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance	8,838,165	9,903,583
Warrants to Purchase Common Stock 2011 Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance	1,310,000	1,310,000
Warrants to Purchase Common Stock 2012 Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance	2,054,893	3,021,077
Warrants to Purchase Common Stock 2013 Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance		3,500,000
Warrants to Purchase Common Stock 2014 Offering [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance	1,500,000	1,500,000

Capitalization and Warrant Li42

Capitalization and Warrant Liability - Outstanding Warrants to Purchase Shares of Common Stock (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Jan. 31, 2014	Feb. 28, 2013
Class of Warrant or Right [Line Items]
Number of Underlying Shares	4,864,893
Exercise Price	$ 1.01	$ 1.01	$ 4.50	$ 1.01
February 2, 2016 [Member]
Class of Warrant or Right [Line Items]
Number of Underlying Shares	1,310,000
Exercise Price	$ 3.55
Expiration	Feb. 2, 2016
March 14, 2017 [Member]
Class of Warrant or Right [Line Items]
Number of Underlying Shares	1,500,000
Exercise Price	$ 4.50
Expiration	Jul. 15, 2016
July 15, 2016 [Member]
Class of Warrant or Right [Line Items]
Number of Underlying Shares	2,054,893
Exercise Price	$ 1.01
Expiration	Mar. 14, 2017

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)Plans$ / sharesshares	Dec. 31, 2014USD ($)$ / shares	Dec. 31, 2013USD ($)$ / shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of incentive plans | Plans	2
Common stock authorized for equity incentive plans | shares	11,500,000
Common stock shares issued | shares	2,661,835
Shares available for issuance | shares	716,423
Shares of common stock outstanding | shares	8,121,742
Stock-based compensation expense	$ 2,929,000	$ 2,605,000	$ 1,523,000
Weighted average fair value of options granted | $ / shares	$ 0.94	$ 1.29	$ 1.42
Total fair value of options vested	$ 1,225,000	$ 940,000	$ 585,000
Total unrecognized estimated compensation cost	$ 2,245,000
Weighted average contractual life of unvested options	8 years 8 months 23 days
Compensation cost related to unvested stock-based awards not yet recognized, expected year for recognition	2,019
Restricted stock vested	$ 1,773,000	$ 1,734,000	$ 805,000
Estimated compensation cost of unvested restricted stock	$ 1,533,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity and Related Information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Options Outstanding, Beginning Balance	6,383,457	5,129,579	4,058,184
Number of Options, Granted	1,215,296	1,420,800	1,336,928
Number of Options, Exercised	(32,439)	(103,481)	(1,312)
Number of Options, Forfeited/Terminated/ Expired	(513,672)	(63,441)	(264,221)
Number of Options Outstanding, Ending Balance	7,052,642	6,383,457	5,129,579
Weighted Average Exercise Price Outstanding, Beginning Balance	$ 3.31	$ 3.72	$ 4.36
Number of Options, Vested during 2014	945,297
Weighted Average Exercise Price, Granted	$ 1.31	1.68	1.71
Number of Options, Vested and exercisable at December 31, 2014	5,065,143
Weighted Average Exercise Price, Exercised	$ 1.60	1.75	1.26
Weighted Average Exercise Price, Forfeited/Terminated/ Expired	2.34	1.98	3.36
Weighted Average Exercise Price Outstanding, Ending Balance	3.05	$ 3.31	$ 3.72
Weighted Average Exercise Price, Vested during 2014	1.62
Weighted Average Exercise Price, Vested and exercisable at December 31, 2014	$ 3.65

Stock-Based Compensation - Su45

Stock-Based Compensation - Summarizes Information Concerning Options Outstanding and Options Vested and Exercisable (Detail)	12 Months Ended
	Dec. 13, 2015$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Number of Options | shares	7,052,642
Options Vested and Exercisable, Number of Options | shares	5,065,143
1.16 - 1.86 Exercise Price [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range	$ 1.16
Exercise price upper range	$ 1.86
Options outstanding, Number of Options | shares	3,815,059
Option Outstanding, Weighted Average Remaining Contractual Life	8 years 2 months 19 days
Options Outstanding, Weighted Average Exercise Price	$ 1.55
Options Vested and Exercisable, Number of Options | shares	1,841,560
Options Vested and Exercisable, Weighted Average Remaining Contractual Life	7 years 7 months 28 days
Options Vested and Exercisable, Weighted Average Exercise Price	$ 1.61
2.09 - 3.84 Exercise Price [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range	2.09
Exercise price upper range	$ 3.84
Options outstanding, Number of Options | shares	244,583
Option Outstanding, Weighted Average Remaining Contractual Life	5 years 1 month 21 days
Options Outstanding, Weighted Average Exercise Price	$ 2.73
Options Vested and Exercisable, Number of Options | shares	234,583
Options Vested and Exercisable, Weighted Average Remaining Contractual Life	4 years 11 months 27 days
Options Vested and Exercisable, Weighted Average Exercise Price	$ 2.73
4.00 - 5.28 Exercise Price [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range	4
Exercise price upper range	$ 5.28
Options outstanding, Number of Options | shares	2,993,000
Option Outstanding, Weighted Average Remaining Contractual Life	1 year 5 months 27 days
Options Outstanding, Weighted Average Exercise Price	$ 4.98
Options Vested and Exercisable, Number of Options | shares	2,989,000
Options Vested and Exercisable, Weighted Average Remaining Contractual Life	1 year 5 months 23 days
Options Vested and Exercisable, Weighted Average Exercise Price	$ 4.98

Stock-Based Compensation - Su46

Stock-Based Compensation - Summary of Restricted Stock Unit Activity and Related Information (Detail) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Restricted Stock Units, Outstanding, Beginning balance	1,889,267	2,449,346	70,814
Number of Restricted Stock Units, Granted	455,776	460,112	2,851,964
Number of Restricted Stock Units, Vested/issued	(1,032,979)	(1,013,446)	(486,359)
Number of Restricted Stock Units, Forfeited / Expired	(242,964)	(6,745)	(5,073)
Number of Restricted Stock Units, Outstanding, Ending balance	1,069,100	1,889,267	2,449,346
Weighted Average Fair Value, Beginning Balance	$ 1.70	$ 1.71	$ 1.86
Number of Restricted Stock Units, Vested/Issued Cumulative	2,524,603
Weighted Average Fair Value, Granted	$ 1.28	1.65	1.71
Weighted Average Fair Value, Vested/Issued	1.69	1.71	1.72
Weighted Average Fair Value, Forfeited/Expired	1.62	1.68	1.77
Weighted Average Fair Value, Ending Balance	1.55	$ 1.70	$ 1.71
Weighted Average Fair Value Vested and Exercisable	$ 1.71

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015USD ($)
Income Taxes [Line Items]
Income tax paid	$ 0
U.S. Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	102,261,000
Research and development tax credit	4,277,000
Foreign [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	12,724,000
Research and development tax credit	177,000
State and City [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 53,657,000
Earliest Tax Year [Member] | U.S. Federal [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2,020
Tax credit carryforwards, expiration year	2,020
Earliest Tax Year [Member] | Foreign [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2,016
Tax credit carryforwards, expiration year	2,036
Earliest Tax Year [Member] | State and City [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2,016
Latest Tax Year [Member] | U.S. Federal [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2,036
Tax credit carryforwards, expiration year	2,016
Latest Tax Year [Member] | Foreign [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2,020
Tax credit carryforwards, expiration year	2,020
Latest Tax Year [Member] | State and City [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2,036
Not Subject To Annual Limitations [Member] | U.S. Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 65,633,000
Research and development tax credit	4,277,000
Not Subject To Annual Limitations [Member] | Foreign [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	12,724,000
Research and development tax credit	177,000
Not Subject To Annual Limitations [Member] | State and City [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 48,484,000
Not Subject To Annual Limitations [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2,016
Tax credit carryforwards, expiration year	2,016
Not Subject To Annual Limitations [Member] | Latest Tax Year [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2,031
Tax credit carryforwards, expiration year	2,031

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Federal Statutory Income Tax Rate to Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation [Line Items]
Statutory Federal income tax rate	34.00%	34.00%
State income taxes - net of Federal tax benefit	1.50%	1.00%
Other permanent differences	(3.50%)	6.60%
Valuation allowance	(40.20%)	(48.10%)
Effective tax rate for the year	0.20%	0.90%
U.S. Federal [Member]
Effective Income Tax Rate Reconciliation [Line Items]
Research and development	8.20%	6.50%
Foreign [Member]
Effective Income Tax Rate Reconciliation [Line Items]
Research and development	0.20%	0.90%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 40,215	$ 34,657
Research and development credit carryforwards	4,454	3,134
Compensation expense	3,300	3,177
Other	1,129	1,084
Total deferred tax assets	49,098	42,052
Valuation allowance for deferred tax assets	(48,921)	(41,852)
Net deferred tax assets	$ 177	$ 200

Profit Sharing Plan and 401 (k)

Profit Sharing Plan and 401 (k) Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Postemployment Benefits [Abstract]
Employer contribution for profit sharing plan	$ 314,000	$ 284,000	$ 97,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] - Healios License Agreement [Member] $ in Millions	Jan. 08, 2016USD ($)
Subsequent Event [Line Items]
Up-front cash payment received	$ 15
Potential near-term payment received	10
Regulatory Milestones [Member]
Subsequent Event [Line Items]
Commercial milestone revenue	30
Sales Milestones [Member]
Subsequent Event [Line Items]
Maximum revenue that could be recognized	$ 185

Quarterly Financial Data - Quar

Quarterly Financial Data - Quarterly Financial Data (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
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Revenues	$ 10,605	$ 396	$ 216	$ 731	$ 235	$ 293	$ 388	$ 707	$ 11,948	$ 1,623	$ 2,438
Net income (loss)	$ 3,592	$ (6,497)	$ (1,035)	$ (12,482)	$ (6,554)	$ (4,719)	$ 675	$ (11,484)	$ (16,422)	$ (22,082)	$ (30,743)
Basic net income (loss) per common share	$ 0.04	$ (0.08)	$ (0.01)	$ (0.16)	$ (0.08)	$ (0.06)	$ 0.01	$ (0.15)	$ (0.20)	$ (0.29)	$ (0.53)
Diluted net loss per common share	$ 0.04	$ (0.08)	$ (0.05)	$ (0.16)	$ (0.08)	$ (0.08)	$ (0.04)	$ (0.15)	$ (0.20)	$ (0.31)	$ (0.53)

Schedule II - Valuation and Q53

Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 42,204	$ 26,383	$ 34,552
Additions	7,080	15,812	10,137
Deductions			18,306
Balance at End of Year	49,284	42,204	26,383
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	352	341	330
Additions	11	11	11
Balance at End of Year	363	352	341
Tax valuation allowances [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	41,852	26,042	34,222
Additions	7,069	15,810	10,126
Deductions			18,306
Balance at End of Year	$ 48,921	$ 41,852	$ 26,042