Athersys, Inc / New (ATHXQ) 10-K 15 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Mar. 07, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
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		125,830,331
Entity Public Float			$ 161.5

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 29,316	$ 14,753
Accounts receivable	739	598
Prepaid expenses and other	1,135	929
Total current assets	31,190	16,280
Equipment, net	2,206	2,605
Other	197	175
Total assets	33,593	19,060
Current liabilities:
Accounts payable	4,469	4,761
Accrued compensation and related benefits	1,065	1,190
Accrued clinical trial costs	1,453	389
Accrued expenses	425	535
Accrued license fee expense	1,900
Deferred revenue	771
Total current liabilities	10,083	6,875
Advance from customer	134
Warrant liabilities		1,004
Stockholders' equity:
Preferred stock, at stated value; 10,000,000 shares authorized, and no shares issued and outstanding at December 31, 2017 and 2016
Common stock, $0.001 par value; 300,000,000 and 150,000,000 shares authorized at December 31, 2017 and 2016, respectively; 122,077,453 and 86,629,302 shares issued and outstanding at December 31, 2017 and 2016, respectively	122	87
Additional paid-in capital	373,884	329,373
Accumulated deficit	(350,630)	(318,279)
Total stockholders' equity	23,376	11,181
Total liabilities and stockholders' equity	$ 33,593	$ 19,060

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
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	300,000,000	150,000,000
Common stock, shares issued	122,077,453	86,629,302
Common stock, shares outstanding	122,077,453	86,629,302

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Contract revenue	$ 2,843	$ 16,238	$ 10,298
Grant revenue	865	1,109	1,650
Total revenues	3,708	17,347	11,948
Costs and expenses
Research and development (including stock compensation expense of $1,232, $1,192 and $1,277 in 2017, 2016 and 2015, respectively)	27,841	24,838	21,316
General and administrative (including stock compensation expense of $1,812, $1,676 and $1,652 in 2017, 2016 and 2015, respectively)	8,466	7,835	7,536
Depreciation	684	382	267
Total costs and expenses	36,991	33,055	29,119
Gain from insurance proceeds, net		682
Loss from operations	(33,283)	(15,026)	(17,171)
Income (expense) from change in fair value of warrants, net	728	(557)	772
Other income (expense), net	314	209	(61)
Loss before income taxes	(32,241)	(15,374)	(16,460)
Income tax benefit		37	38
Net loss and comprehensive loss	$ (32,241)	$ (15,337)	$ (16,422)
Net loss per common share, basic	$ (0.29)	$ (0.18)	$ (0.20)
Weighted average shares outstanding, basic	112,053,369	84,715,471	82,143,610
Net loss per common share, diluted	$ (0.29)	$ (0.18)	$ (0.20)
Weighted average shares outstanding, diluted	112,053,369	84,715,471	82,851,091

Consolidated Statements of Ope5

Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Research and Development [Member]
Stock compensation expense	$ 1,232	$ 1,192	$ 1,277
General and Administrative [Member]
Stock compensation expense	$ 1,812	$ 1,676	$ 1,652

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2014	$ 20,895		$ 78	$ 307,337	$ (286,520)
Preferred stock shares, beginning balance at Dec. 31, 2014	0	0	0	0	0
Common stock beginning balance, shares at Dec. 31, 2014			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			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
Common stock ending balance, shares at Dec. 31, 2015			83,720,154
Stock-based compensation	$ 2,868			$ 2,868
Issuance of common stock from warrant exercises, Cost	163			163
Issuance of common stock from warrant exercises, Shares			161,366
Issuance of common stock and warrants, net of issuance costs	4,230		$ 2	4,228
Issuance of common stock and warrants, net of issuance costs, Shares			2,191,418
Issuance of common stock under equity compensation plans	(467)		$ 1	(468)
Issuance of common stock under equity compensation plans, Shares			556,364
Net and comprehensive loss	(15,337)				$ (15,337)
Ending balance at Dec. 31, 2016	$ 11,181		$ 87	$ 329,373	$ (318,279)
Preferred stock shares, ending balance at Dec. 31, 2016	0	0	0	0	0
Common stock ending balance, shares at Dec. 31, 2016	86,629,302		86,629,302
Cumulative effect of accounting change	$ (110)				$ (110)
Stock-based compensation	3,154			$ 3,154
Issuance of common stock from warrant exercises, Cost	1,862		$ 2	1,860
Issuance of common stock from warrant exercises, Shares			1,843,363
Issuance of common stock and warrants, net of issuance costs	39,813		$ 33	39,780
Issuance of common stock and warrants, net of issuance costs, Shares			33,172,300
Issuance of common stock under equity compensation plans	$ (283)			(283)
Issuance of common stock under equity compensation plans, Shares	4,266,556		432,488
Net and comprehensive loss	$ (32,241)				(32,241)
Ending balance at Dec. 31, 2017	$ 23,376		$ 122	$ 373,884	$ (350,630)
Preferred stock shares, ending balance at Dec. 31, 2017	0	0	0	0	0
Common stock ending balance, shares at Dec. 31, 2017	122,077,453		122,077,453

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (32,241)	$ (15,337)	$ (16,422)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	684	382	267
Gain from forgiveness of note payable		(190)
Stock-based compensation	3,044	2,868	2,929
Other	(22)	2	23
Stock - based patent license and settlement expense	3,150
Gain from insurance proceeds, net		(682)
Change in fair value of warrant liabilities	(728)	557	(772)
Changes in operating assets and liabilities:
Accounts receivable	(141)	(237)	333
Prepaid expenses and other	(206)	(462)	4
Accounts payable and accrued expenses	1,537	2,413	(296)
Advance from customer	134
Deferred revenue	771	(245)	170
Net cash used in operating activities	(24,018)	(10,931)	(13,764)
Investing activities
Purchase of available-for-sale securities		(16,343)
Sales of available-for-sale securities		16,305
Proceeds from insurance		682
Purchases of equipment	(285)	(1,711)	(132)
Net cash used in investing activities	(285)	(1,067)	(132)
Financing activities
Proceeds from issuance of common stock, net	37,287	4,028	10,310
Proceeds from exercise of warrants	1,862	163	976
Shares retained for withholding tax payments on stock-based awards	(283)	(467)	(490)
Net cash provided by financing activities	38,866	3,724	10,796
Increase (decrease) in cash and cash equivalents	14,563	(8,274)	(3,100)
Cash and cash equivalents at beginning of year	14,753	23,027	26,127
Cash and cash equivalents at end of year	$ 29,316	$ 14,753	$ 23,027

Background

Background	12 Months Ended
	Dec. 31, 2017
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 of research and later-stage product development activities. We incurred losses since our inception in 1995 and had an accumulated deficit of $350.6 million at December 31, 2017. We will require substantial additional capital to continue our research and development programs, including progressing our clinical product candidates to commercialization and preparing for commercial-scale manufacturing. At December 31, 2017, we had available cash and cash equivalents of $29.3 million, and we believe that these funds, used to execute our existing operating plans, are sufficient to meet our obligations as they come due at least for a period of twelve months from the date of the issuance of these consolidated financial statements. In the longer-term, we will make use of available cash, but will have to continue to generate additional capital to meet our needs through new and existing collaborations and related license fees and milestones, the sale of equity securities from time to time including through our equity purchase agreement, grant-funding opportunities, deferring certain discretionary costs and staging certain development costs, as needed.

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2017
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 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. Other than for our collaboration with Healios that has remaining deliverables, we have recognized the full amount of license fees under our collaboration agreements as contract revenue under ASC 605-25 605-S25, non-substantive We recognize revenue, in full, in the period that the milestone is achieved from at-risk, Grant revenue consists of funding under cost reimbursement programs primarily from federal and non-profit We recognize contract 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 reports from the licensee to enable calculation of the royalty due. We began receiving in 2014 tiered royalties from RTI on worldwide commercial sales of implants using our technologies based on a royalty rate starting in the mid-single mid-teens, 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. Cash used in investing activities excluded $0.1 million of accrued capital expenditures in 2016. Investments in Available-for-Sale We determine the appropriate classification of investment securities, if any, at the time of purchase and re-evaluate available-for-sale Available-for-sale available-for-sale available-for-sale available-for-sale Research and Development Research and development expenditures, which consist primarily of costs associated with external clinical and preclinical study fees, investigational product manufacturing costs and process development costs for manufacturing, personnel costs, legal expenses resulting from intellectual property application and maintenance 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, 2017. We may also pay sublicense fees from time-to-time 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. Proceeds from Insurance In 2016, our facility sustained flood damage representing both an unusual and infrequent event. We recognized a net insurance recovery gain of $0.7 million that was reported as a separate component of our loss from operations. Proceeds from insurance settlements, except for those directly related to investing or financing activities, were recognized as cash inflows from operating activities. Since the majority of the damage from the flood was to fully-depreciated leasehold improvements, the amount of losses were less than the amount of the insurance proceeds received. Insurance proceeds are recorded to the extent of the losses and then, only if recovery is realized or probable. Any gains in excess of losses are recognized only when the contingencies regarding the recovery are resolved, and the amount is fixed or determinable. An additional $0.3 million of insurance proceeds were received in 2018. 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 and 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. Generally, warrants are classified as liabilities, as opposed to equity, if the agreement includes the potential for a cash settlement or an adjustment to the exercise price, and warrant liabilities are recorded at their fair values at each balance sheet date. We classify these warrant liabilities on the consolidated balance sheet as non-current 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, 2017, the majority of our accounts receivable are due from granting authorities and two collaborators. 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. Options may be exercised for cash or by a cashless exercise that is permitted under certain conditions. In the event of a cashless exercise, we retain the number of shares equivalent to the exercise cost based on the market value at the time of exercise, and issue the net number of shares to the holder. We recognize income tax benefits and deficiencies as income tax expense or benefit in the income statement and the tax effects of exercised or vested awards are treated as discrete items in the reporting period in which they occur. We also recognize excess tax benefits regardless of whether the benefit reduces taxes payable in the current period. Excess tax benefits are classified along with other income tax cash flows as an operating activity. In regards to forfeitures, we adopted ASU 2016-09 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, 2017 2016 2015 Volatility 71.2% 70.3% 83.9% Risk-free interest rate 2.0% 1.5% 2.1% Expected life of option 6.2 years 6.2 years 6.1 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, 2017 and 2016. 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. Refer to Note H regarding recent tax reform. 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 in which we have outstanding warrant liabilities, we evaluate the income from such warrant liabilities and consider whether it results in a potentially dilutive effect to net loss per share. For the year ended December 31, 2015, 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, 2017, 2016 and 2015, in thousands, except per share data. Year ended December 31, 2017 2016 2015 Numerator: Net loss and comprehensive loss $ (32,241 ) $ (15,337 ) $ (16,422 ) Less: income from change in fair value of warrants — — (332 ) Net loss attributable to common stockholders used to calculate diluted net loss per share $ (32,241 ) $ (15,337 ) $ (16,754 ) Denominator: Weighted-average shares outstanding - Basic 112,053 84,715 82,144 Potentially dilutive common shares outstanding: Warrants — — 707 Weighted-average shares used to calculate diluted net loss per share 112,053 84,715 82,851 Basic – net loss per share $ (0.29 ) $ (0.18 ) $ (0.20 ) Dilutive – net loss per share $ (0.29 ) $ (0.18 ) $ (0.20 ) We have outstanding options, restricted stock units and previously outstanding warrants that were 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, 2017 2016 2015 Stock options 8,919,113 9,236,228 7,052,642 Restricted stock units 1,648,986 1,201,159 1,069,100 Warrants — 1,893,527 2,810,000 10,568,099 12,330,914 10,931,742 Recently Issued Accounting Standards In March 2016, the FASB (“FASB”) issued Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation - Improvements to Employee Share-Based Payment Accounting In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) right-of-use In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) 2014-09 We will adopt this guidance in the first quarter of 2018, utilizing the modified retrospective transition method only with respect to contracts that were not complete as of January 1, 2018. We evaluated all of our collaborative agreements on a contract-by-contract We expect that license-related amounts, including upfront payments, exclusivity fees, additional disease indication fees, and development, regulatory and sales-based milestones will be recognized, generally, at a point in time when earned. Similarly, product supply revenue is expected to be recognized at a point in time while any service revenue will be recognized over time when earned. Topic 606 does not contain guidance specific to milestone payments but rather, requires potential milestone payments to be considered in accordance with the overall model of Topic 606. As a result, revenues from contingent milestone payments may be recognized earlier under Topic 606 than under Topic 605, based on an assessment of the probability of achievement of the milestone and the likelihood of a significant reversal of such milestone revenue at each reporting date. This assessment may result in recognizing milestone revenue before the milestone event has been achieved. In addition, Topic 606 changes guidance regarding the accounting for variable consideration received from license arrangements, which may impact the estimation of, and determination of the timing of, our related revenue recognition. As of December 31, 2017, we have substantially completed our planning to apply the necessary changes to accounting processes, procedures, systems and internal controls, and we plan to finalize our transition adjustment under Topic 606 in the first quarter of 2018.

Equipment

Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Equipment	C. Equipment December 31, Equipment consists of (in thousands): 2017 2016 Laboratory equipment $ 6,262 $ 6,196 Office equipment and leasehold improvements 3,039 3,040 Process development equipment not yet in service 363 965 9,664 10,201 Accumulated depreciation (7,458 ) (7,596 ) $ 2,206 $ 2,605 In 2017 and 2016, we disposed of approximately $0.8 million and $0.6 million, respectively, of obsolete laboratory equipment, office equipment and leasehold improvements, all of which were fully depreciated.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2017
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. At December 31, 2017, we had no financial assets or liabilities measured at fair value on a recurring basis. At December 31, 2016, we had warrant liabilities of $1.0 million that represented Level 3 liabilities under the hierarchy. In March 2017, these warrants were either exercised or expired, and we no longer have any outstanding warrants. 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 any outstanding warrant liabilities at fair value. The fair value is estimated using the expected volatility based on our historical volatility and is determined using probability weighted-average assumptions, when appropriate. A roll-forward of fair value measurements using significant unobservable inputs (Level 3) for the warrants is as follows (in thousands): Year ended Balance January 1, 2017 $ 1,004 Settlements from exercise (276 ) Gain included in income from change in fair value of warrants (728 ) Balance December 31, 2017 $ — 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 2019, and we intend to renew our agreement. 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 2018 and includes options to renew annually through July 2022, with annual rent of approximately $185,000, subject to adjustments based on an inflationary index. Aggregate rent expense was approximately $477,000, $465,000 and $467,000 in 2017, 2016 and 2015, respectively. The future annual minimum lease commitments at December 31, 2017 are approximately $385,000 for 2018 and $75,000 for 2019. We paid no interest during the three years ended December 31, 2017.

Collaborative Arrangements and

Collaborative Arrangements and Revenue Recognition	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborative Arrangements and Revenue Recognition	E. Collaborative Arrangements and Revenue Recognition Healios In 2016, we entered into a license agreement (“Healios Agreement”) with Healios to develop and commercialize MultiStem cell therapy for ischemic stroke in Japan and to provide Healios with access to our proprietary MAPC technology for use in its “organ bud” program, initially for transplantation to treat liver disease or dysfunction. Under the Healios Agreement, Healios 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 may exercise its option to expand the collaboration prior to certain milestone dates that are expected to occur within the next several years. Under the terms of the Healios Agreement, we received a nonrefundable, up-front mark-up. For the ischemic stroke indication, we may also receive additional success-based development, regulatory approval and sales milestones, which are non-refundable non-creditable If Healios exercises the option to expand the collaboration to include ARDS and another indication in the orthopedic area, we would be entitled to receive a cash payment of $10 million at the time of exercise and royalties from product sales and success-based development, regulatory approval and sales milestones, as well as payments for product supply related to the additional indications covered by the option. 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 certain dates in the future. To determine the appropriate accounting for the license agreement, we evaluated the Healios Agreement and related facts and circumstances, focusing in particular on the rights and obligations of the arrangement. We determined that our obligations under the Healios Agreement represent multiple deliverables, and 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 or 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) Given Healios’ ability to sublicense under the Healios Agreement and its ability to conduct the ongoing development efforts at the inception of the arrangement, we concluded that the license had stand-alone value and would be treated as a separate unit of accounting, noting that there was no general right of return associated with the license. Furthermore, the preclinical and clinical manufacturing services and certain near-term regulatory advisory services provided to Healios were also determined to have stand-alone value and considered separate units of accounting. We were unable to establish vendor-specific objective evidence of selling price or third-party evidence for either the license or the services, and thus, instead, allocated the arrangement consideration between the license and the services based on their relative selling prices using a best estimate of selling price (“BESP”). We developed the BESP of the license using a probability-weighted, discounted cash flow analysis using the income approach, taking into consideration market assumptions, including the estimated development and commercialization timeline, data regarding patient population, discount rate related to our industry, and probability of success using market data for both our industry and therapeutic field. We estimated the BESP of the manufacturing services and certain near-term regulatory advisory services using actual historical experience and best estimates of the cost of obtaining these services at arm’s length from a third-party provider, including an estimated mark-up. Other contingent deliverables that were not accounted for at the inception of the arrangement, and will not be accounted for until the contingency is resolved, included the potential expansion of the collaboration to include additional indications, and the milestones that are not substantive since they are dependent on the activities of Healios. Furthermore, the Healios arrangement contemplates our providing manufacturing services for commercial product supply, the terms of which are not defined and are to be agreed upon in the future under a separate supply agreement. Upon the removal of the contingencies or modifications to the deliverables under the arrangement, we will reevaluate the allocation of consideration to the remaining undelivered items, including the estimated selling prices, with any changes in estimates accounted for on a prospective basis. In January 2017, we signed a clinical trial supply agreement for the manufacturing of investigational product for Healios for its Japan clinical study, the terms of which were consistent with the Healios Agreement. The clinical trial supply agreement was amended in July 2017 to clarify a cost-sharing arrangement associated with our supply of clinical materials. The proceeds from Healios that relate specifically to the cost-sharing arrangement may result in a reduction in the proceeds we receive from Healios upon the achievement of two future milestones, and an increase to a later-stage commercial milestone. Of the aggregate $225 million of potential proceeds from success-based development, regulatory approval and sales milestones, the maximum net decrease related to this cost-sharing arrangement amounts to less than 3% of the aggregate milestones. While the amendment to the supply agreement resulted in a revision to the terms associated with the product supply under the Healios Agreement, namely the cost of product supply, the revision did not affect any of the deliverables under the overall arrangement. Therefore, the allocation of revenue as of the inception of the arrangement to the undelivered items was unchanged, and the cost-sharing proceeds received are recognized on the balance sheet as a non-current In September 2017, we entered into a services agreement with Healios, in which Healios provides financial support to establish a contract manufacturer in Japan to produce product for Healios, and services began in the fourth quarter of 2017. We evaluated this amendment as a combined agreement along with the Healios Agreement due to its connection to the license and the product supply under the Healios Agreement. The costs of the services are reimbursed by Healios at our actual cost, without mark-up. Furthermore, in September 2017, we amended the Healios Agreement to confer to Healios a limited license to manufacture MultiStem in the event that we are acquired by a third party. Such amendment was evaluated as a combined agreement along with the Healios Agreement, noting that the amendment represented a contingent deliverable and, therefore, had no impact on the allocation of revenue to the remaining undelivered items. Refer to Note B for a discussion of the expected impact of our adoption of Topic 606 on January 1, 2018. Refer to Note J for disclosure of subequent events related to our Healios collaboration. Chugai In October 2015, we and Chugai Pharmaceutical Co. Ltd. (“Chugai”) agreed to terminate the License Agreement (the “Chugai 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 Chugai Agreement and on the development strategy, as proposed by Chugai, of our MultiStem cell therapy for the treatment of ischemic stroke in Japan. Pursuant to the terms of the Chugai Agreement, upon termination, we regained all rights for developing our stem cell technologies and products for ischemic stroke in Japan, retained the $10 million non-refundable Other Under our agreement with RTI to develop and commercialize biologic implants using our technology for certain orthopedic applications in the bone graft substitutes market, we are eligible to receive up to $34.5 million in remaining cash payments upon the successful achievement of certain commercial milestones, after the first commercial milestone payment of $1.0 million was received in 2017. In addition, we receive tiered royalties on worldwide commercial sales of implants using our technologies based on a royalty rate starting in the mid-single mid-teens. In January 2017, we received an option fee related to an agreement with a global leader in the animal health business segment to evaluate our cell therapy technology for application in an animal health area. Under the terms of the agreement, we received the payment in exchange for an exclusive period to evaluate our cell therapy technology with an option to negotiate for a license for the development and commercialization of the technology for the animal health area. The option fee is recorded as deferred revenue at December 31, 2017 since the performance obligation of granting a license has not occurred. If the option is exercised, we will include the option fee in the overall consideration for the license arrangement, to be evaluated at that time. If the option is not exercised, the option fee will be recognized as revenue at that time since there will be no more performance obligations. The evaluation of our technology for this application is currently ongoing.

Capitalization and Warrant Liab

Capitalization and Warrant Liability	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Capitalization and Warrant Liability	F. Capitalization and Warrant Liability Capitalization At December 31, 2017, we had 300 million (150 million at December 31, 2016) shares of common stock and 10.0 million shares of undesignated preferred stock authorized. In June 2017, our stockholders approved an amendment to our certificate of incorporation to increase the number of authorized shares of common stock to 300 million. No shares of preferred stock have been issued as of December 31, 2017. Other than the change to the number of authorized shares of common stock, there were no changes to the terms of our common stock. In February 2017, we completed a public offering generating net proceeds of approximately $20.9 million through the issuance of 22,772,300 shares of common stock at an offering price of $1.01 per share. The following shares of common stock were reserved for future issuance: December 31 2017 2016 Stock-based compensation plans 16,952,125 17,940,618 Warrants to purchase common stock — 1,893,527 Shares issuable upon patent milestone 500,000 — 17,452,125 19,834,145 The outstanding warrants as of December 31, 2016 to purchase shares of common stock had an exercise price of $1.01 per share and expired or were exercised by March 2017. Proceeds from warrant exercises were $1.9 million, $0.2 million and $1.0 million in 2017, 2016 and 2015, respectively. Aspire Capital We have had an equity purchase arrangement in place with Aspire Capital Fund LLC (“Aspire Capital”) since 2011, through two-to-three License Agreement and Settlement In October 2017, we entered into an agreement to settle longstanding intellectual property disagreements with a third party. As part of the agreement, we were granted a worldwide, non-exclusive license, with the right to sublicense, to the other party’s patents and applications that were at the core of the intellectual property dispute, for use related to the treatment or prevention of disease or conditions using cells. In return, we agreed not to enforce our intellectual property rights against the party with respect to certain patent claims, nor to further challenge the patentability or validity of certain applications or patents. In connection with the license and settlement agreement, we paid $500,000 and issued 1,000,000 shares of our common stock with a fair value of $2.3 million upon execution of the agreement, and we will pay an additional $250,000 over each of the next four quarters. Additionally, we will issue 500,000 shares of common stock upon the issuance of a patent from the party’s patent applications at the core of the dispute, which we deem to be probable. There will be no royalty, milestone or other payments due to the third party associated with the development and commercialization of our cell therapy products. We have included the $1.0 million cash obligation and the contingent obligation to issue 500,000 shares of common stock, at fair value of $0.9 million at December 31, 2017, in accrued license fee expense on the consolidated balance sheets.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	G. Stock-Based Compensation We have an incentive plan that authorized an aggregate of 20,035,000 shares of common stock for awards to employees, directors and consultants. The equity incentive plan authorizes 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. As of December 31, 2017, a total of 4,266,556 shares (including 232,622 shares related to an expired incentive plan) of common stock have been issued under our equity incentive plan. As of December 31, 2017, a total of 6,384,026 shares were available for issuance under our equity compensation plan, and stock-based awards to purchase 10,568,099 shares (including 951,059 shares related to an expired incentive plan) of common stock were outstanding. We recognized $3.0 million, $2.9 million and $2.9 million of stock-based compensation expense in 2017, 2016 and 2015, respectively. Stock Options The weighted average fair value of options granted in 2017, 2016 and 2015 was $0.95, $1.35 and $0.94 per share, respectively. The total fair value of options vested during 2017, 2016 and 2015 was $2.0 million, $1.7 million and $1.2 million, respectively. At December 31, 2017, total unrecognized estimated compensation cost related to unvested stock options was approximately $4.5 million, which is expected to be recognized by the end of 2021 using the straight-line method. The weighted average contractual life of unvested options at December 31, 2017 was 8.86 years. The aggregate intrinsic value of fully vested option shares and option shares expected to vest as of December 31, 2017 was $1.8 million. A summary of our stock option activity and related information is as follows: Number Weighted Outstanding January 1, 2015 6,383,457 $ 3.31 Granted 1,215,296 1.31 Exercised (32,439 ) 1.60 Forfeited / Terminated / Expired (513,672 ) 2.34 Outstanding December 31, 2015 7,052,642 3.05 Granted 2,840,000 2.13 Exercised (164,827 ) 1.56 Forfeited / Expired (491,587 ) 3.57 Outstanding December 31, 2016 9,236,228 2.76 Granted 2,596,480 1.47 Exercised (136,056 ) 1.50 Forfeited / Expired (2,777,539 ) 4.76 Outstanding December 31, 2017 8,919,113 $ 1.78 Vested during 2017 1,666,915 $ 1.78 Vested and exercisable at December 31, 2017 4,803,470 $ 1.86 December 31, 2017 Options Outstanding Options Vested and Exercisable Exercise Price Number Weighted Weighted Number Weighted Weighted $1.01 – 1.96 6,326,094 7.73 $ 1.53 3,516,361 6.69 $ 1.58 $2.09 – 3.84 2.423.519 8.04 $ 2.24 1,117,609 7.53 $ 2.30 $4.00 – 5.28 169,500 1.09 $ 4.69 169,500 1.09 $ 4.69 8,919,113 4,803,470 Restricted Stock Units A summary of our restricted stock unit activity and related information is as follows: Number Weighted Outstanding January 1, 2015 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 Granted 933,552 2.19 Vested-common stock issued (732,720 ) 1.71 Forfeited / Expired (68,773 ) 1.90 Number Weighted Outstanding December 31, 2016 1,201,159 1.92 Granted 1,054,720 1.46 Vested-common stock issued (571,118 ) 1.75 Forfeited / Expired (35,775 ) 1.82 Outstanding December 31, 2017 1,648,986 $ 1.69 Vested/Issued cumulative at December 31, 2017 3,828,441 $ 1.71 The total fair value of restricted stock units vested during 2017, 2016 and 2015 was $1.0 million, $1.3 million and $1.8 million, respectively. At December 31, 2017, total unrecognized estimated compensation cost related to unvested restricted stock units was approximately $2.7 million, which is expected to be recognized by the end of 2021 using the straight-line method.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	H. Income Taxes At December 31, 2017, we had U.S. federal net operating loss and research and development tax credit carryforwards of approximately $136.6 million and $7.3 million, 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 2021 and 2037. We also had foreign net operating loss carryforwards of approximately $19.9 million. Such foreign net operating loss carryforwards do not expire. We also had state and city net operating loss carryforwards aggregating approximately $69.4 million. Such operating losses may be used to reduce future taxable income and tax liabilities and will expire at various dates between 2018 and 2037. 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, (the “IRC”) as a result of our equity offering that occurred in October 2012. We generated U.S. federal net operating loss carryforwards of $99.9 million, research and development tax credits of $7.3 million, and state and local net operating loss carryforwards of $69.4 million since 2012. We will update our analysis under Section 382 prior to using these attributes. A reconciliation of the Federal statutory income tax rate to our effective tax rate is as follows: Percent of Income 2017 2016 Statutory Federal income tax rate 34.0 % 34.0 % State income taxes - net of Federal tax benefit 0.8 % 0.8 % Other permanent differences (5.5 %) (8.1 %) Valuation allowances 24.1 % (37.0 %) Federal rate change (57.9 %) 0.0 % Research and development - U.S. 4.5 % 10.3 % Research and development - Foreign 0.0 % 0.2 % Effective tax rate for the year 0.0 % 0.2 % Significant components of our deferred tax assets are as follows (in thousands): December 31, 2017 2016 Net operating loss carryforwards $ 35,409 $ 44,929 Research and development credit carryforwards 7,301 6,017 Compensation expense 652 2,735 Other 1,467 1,266 Total deferred tax assets 44,829 54,947 December 31, 2017 2016 Valuation allowance for deferred tax assets (44,829 ) (54,772 ) Net deferred tax assets $ — $ 175 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, 2017. On December 22, 2017, the U.S. federal government enacted legislation commonly referred to as the “Tax Cuts and Jobs Act” (the “TCJA”). The TCJA makes widespread changes to the IRC, including, among other items, a reduction in the federal corporate tax rate from 35% to 21%, effective January 1, 2018. The carrying value of our deferred tax assets and liabilities is also determined by the enacted U.S. corporate income tax rate. Consequently, any changes in the U.S. corporate income tax rate will impact the carrying value of our deferred tax assets and liabilities. Under the new corporate income tax rate of 21%, deferred income tax assets, net, have provisionally decreased by $18.7 million and the valuation allowance has had a corresponding decrease. The Deemed Repatriation Transition Tax (Transition Tax) is a tax on previously untaxed accumulated and current earnings and profit (E&P) of certain of our foreign subsidiaries. To determine the amount of Transition Tax, a company must determine, in addition to other factors, the amount of post-1986 E&P of the relevant foreign subsidiaries as well as the amount of non-U.S. income tax paid on such earnings. The Company believes it has an overall foreign E&P deficit and accordingly has not recorded any provisional Transition Tax obligation as of December 31, 2017. However, the Company is continuing to gather additional information to finalize its Transition Tax liability. We determined that the provisional calculations will be finalized after the underlying timing differences and foreign earnings and profits are finalized with our 2017 federal tax return filing. Furthermore, we are still analyzing certain aspects of the TCJA and refining our calculations which could potentially affect the measurement of these balances or potentially give rise to new or additional deferred tax amounts. We will consider additional guidance from the U.S. Treasury Department, IRS or other standard-setting bodies. Further adjustments, if any, will be recorded by us during the measurement period in 2018, as permitted by SEC Staff Accounting Bulletin 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act

Profit Sharing Plan and 401(k)

Profit Sharing Plan and 401(k) Plan	12 Months Ended
	Dec. 31, 2017
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 $0.3 million in each of 2017, 2016 and 2015.

Subsequent and Other Events

Subsequent and Other Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent and Other Events	J. Subsequent and Other Events In March 2018, we entered into a binding letter of intent (the “LOI”) with Healios to significantly expand Healios’ license to develop MultiStem products. Under the terms of the LOI, we and Healios will work to execute the agreements necessary to expand the existing collaboration by April 30, 2018. If the expansion is consummated, Healios would, among other things, (i) expand its license in Japan to include ARDS, including idiopathic pulmonary fibrosis (“ARDS Field”), trauma and use of MultiStem for organ buds for all organ diseases, (ii) obtain a worldwide exclusive license for use of MultiStem product to treat certain ophthalmological indications, and (iii) obtain an exclusive option to a license to develop and commercialize MultiStem products for ischemic stroke, the ARDS Field and trauma in China. In exchange, we would be entitled to receive payments of $35 million ($10 million of which is guaranteed to be paid to us), as well as additional possible payments, including milestones and royalties. If the expansion agreements are entered into and, thereafter, Healios elects to exercise its option for the license in China, Healios would pay us license fees, milestone payments and escalating royalties or profit-sharing for each indication in China. Also in March 2018, Healios purchased 12,000,000 shares of our common stock and a warrant to purchase up to an additional 20,000,000 shares of common stock for $21,100,000, or approximately $1.76 per share. The warrant does not become effective until the expansion agreements are effective, has a term that expires in September 2020 (subject to a potential nine-month extension), includes both fixed and floating exercise price mechanisms, and is capped such that in no event will Healios own more than 19.9% of our common stock. We and Healios have entered into an investor rights agreement that governs certain rights and obligations relating to Healios’ ownership of our common stock, including rights regarding Board of Director nominees.

Quarterly Financial Data (unaud

Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2017
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, 2017 and 2016, in thousands, except per share data: 2017 First Second Third Fourth Full Year Revenues $ 1,470 $ 669 $ 399 $ 1,170 $ 3,708 Net loss $ (5,631 ) $ (6,267 ) $ (7,243 ) $ (13,100 ) $ (32,241 ) Basic net loss per common share $ (0.06 ) $ (0.06 ) $ (0.06 ) $ (0.11 ) $ (0.29 ) Diluted net loss per common share $ (0.06 ) $ (0.06 ) $ (0.06 ) $ (0.11 ) $ (0.29 ) 2016 First Second Third Fourth Full Year Revenues $ 15,458 $ 595 $ 311 $ 983 $ 17,347 Net income (loss) $ 4,750 $ (6,956 ) $ (6,004 ) $ (7,127 ) $ (15,337 ) Basic net income (loss) per common share $ 0.06 $ (0.08 ) $ (0.07 ) $ (0.08 ) $ (0.18 ) Diluted net income (loss) per common share $ 0.06 $ (0.08 ) $ (0.07 ) $ (0.10 ) $ (0.18 ) 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, 2017
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, 2017 Deducted from asset accounts: Allowance for doubtful accounts- note receivable $ 376 $ — $ (376 ) $ 0 (A) Tax valuation allowances $ 54,772 $ — $ (9,943 ) $ 44,829 (B) Total 2017 $ 55,148 $ — $ (10,319 ) $ 44,829 Year Ended December 31, 2016 Deducted from asset accounts: Allowance for doubtful accounts- note receivable $ 363 $ 13 $ — $ 376 (A) Tax valuation allowances $ 48,921 $ 5,851 $ — $ 54,772 (B) Total 2016 $ 49,284 $ 5,864 $ — $ 55,148 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 (B) Total 2015 $ 42,204 $ 7,080 $ — $ 49,284 (A) – Reserve on note receivable that was fully-reserved. We wrote-off (B) – Substantially all of our deferred tax assets are offset by valuation allowances.

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
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. Other than for our collaboration with Healios that has remaining deliverables, we have recognized the full amount of license fees under our collaboration agreements as contract revenue under ASC 605-25 605-S25, non-substantive We recognize revenue, in full, in the period that the milestone is achieved from at-risk, Grant revenue consists of funding under cost reimbursement programs primarily from federal and non-profit We recognize contract 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 reports from the licensee to enable calculation of the royalty due. We began receiving in 2014 tiered royalties from RTI on worldwide commercial sales of implants using our technologies based on a royalty rate starting in the mid-single mid-teens,
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. Cash used in investing activities excluded $0.1 million of accrued capital expenditures in 2016.
Investments in Available-for-Sale Securities	Investments in Available-for-Sale We determine the appropriate classification of investment securities, if any, at the time of purchase and re-evaluate available-for-sale Available-for-sale available-for-sale available-for-sale available-for-sale
Research and Development	Research and Development Research and development expenditures, which consist primarily of costs associated with external clinical and preclinical study fees, investigational product manufacturing costs and process development costs for manufacturing, personnel costs, legal expenses resulting from intellectual property application and maintenance 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, 2017. We may also pay sublicense fees from time-to-time
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.
Proceeds from Insurance	Proceeds from Insurance In 2016, our facility sustained flood damage representing both an unusual and infrequent event. We recognized a net insurance recovery gain of $0.7 million that was reported as a separate component of our loss from operations. Proceeds from insurance settlements, except for those directly related to investing or financing activities, were recognized as cash inflows from operating activities. Since the majority of the damage from the flood was to fully-depreciated leasehold improvements, the amount of losses were less than the amount of the insurance proceeds received. Insurance proceeds are recorded to the extent of the losses and then, only if recovery is realized or probable. Any gains in excess of losses are recognized only when the contingencies regarding the recovery are resolved, and the amount is fixed or determinable. An additional $0.3 million of insurance proceeds were received in 2018.
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 and 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. Generally, warrants are classified as liabilities, as opposed to equity, if the agreement includes the potential for a cash settlement or an adjustment to the exercise price, and warrant liabilities are recorded at their fair values at each balance sheet date. We classify these warrant liabilities on the consolidated balance sheet as non-current
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, 2017, the majority of our accounts receivable are due from granting authorities and two collaborators. 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. Options may be exercised for cash or by a cashless exercise that is permitted under certain conditions. In the event of a cashless exercise, we retain the number of shares equivalent to the exercise cost based on the market value at the time of exercise, and issue the net number of shares to the holder. We recognize income tax benefits and deficiencies as income tax expense or benefit in the income statement and the tax effects of exercised or vested awards are treated as discrete items in the reporting period in which they occur. We also recognize excess tax benefits regardless of whether the benefit reduces taxes payable in the current period. Excess tax benefits are classified along with other income tax cash flows as an operating activity. In regards to forfeitures, we adopted ASU 2016-09 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, 2017 2016 2015 Volatility 71.2% 70.3% 83.9% Risk-free interest rate 2.0% 1.5% 2.1% Expected life of option 6.2 years 6.2 years 6.1 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, 2017 and 2016. 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. Refer to Note H regarding recent tax reform.
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 in which we have outstanding warrant liabilities, we evaluate the income from such warrant liabilities and consider whether it results in a potentially dilutive effect to net loss per share. For the year ended December 31, 2015, 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, 2017, 2016 and 2015, in thousands, except per share data. Year ended December 31, 2017 2016 2015 Numerator: Net loss and comprehensive loss $ (32,241 ) $ (15,337 ) $ (16,422 ) Less: income from change in fair value of warrants — — (332 ) Net loss attributable to common stockholders used to calculate diluted net loss per share $ (32,241 ) $ (15,337 ) $ (16,754 ) Denominator: Weighted-average shares outstanding - Basic 112,053 84,715 82,144 Potentially dilutive common shares outstanding: Warrants — — 707 Weighted-average shares used to calculate diluted net loss per share 112,053 84,715 82,851 Basic – net loss per share $ (0.29 ) $ (0.18 ) $ (0.20 ) Dilutive – net loss per share $ (0.29 ) $ (0.18 ) $ (0.20 ) We have outstanding options, restricted stock units and previously outstanding warrants that were 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, 2017 2016 2015 Stock options 8,919,113 9,236,228 7,052,642 Restricted stock units 1,648,986 1,201,159 1,069,100 Warrants — 1,893,527 2,810,000 10,568,099 12,330,914 10,931,742
Recently Issued Accounting Standards	Recently Issued Accounting Standards In March 2016, the FASB (“FASB”) issued Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation - Improvements to Employee Share-Based Payment Accounting In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) right-of-use In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) 2014-09 We will adopt this guidance in the first quarter of 2018, utilizing the modified retrospective transition method only with respect to contracts that were not complete as of January 1, 2018. We evaluated all of our collaborative agreements on a contract-by-contract We expect that license-related amounts, including upfront payments, exclusivity fees, additional disease indication fees, and development, regulatory and sales-based milestones will be recognized, generally, at a point in time when earned. Similarly, product supply revenue is expected to be recognized at a point in time while any service revenue will be recognized over time when earned. Topic 606 does not contain guidance specific to milestone payments but rather, requires potential milestone payments to be considered in accordance with the overall model of Topic 606. As a result, revenues from contingent milestone payments may be recognized earlier under Topic 606 than under Topic 605, based on an assessment of the probability of achievement of the milestone and the likelihood of a significant reversal of such milestone revenue at each reporting date. This assessment may result in recognizing milestone revenue before the milestone event has been achieved. In addition, Topic 606 changes guidance regarding the accounting for variable consideration received from license arrangements, which may impact the estimation of, and determination of the timing of, our related revenue recognition. As of December 31, 2017, we have substantially completed our planning to apply the necessary changes to accounting processes, procedures, systems and internal controls, and we plan to finalize our transition adjustment under Topic 606 in the first quarter of 2018.
Fair Value Measurements	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. At December 31, 2017, we had no financial assets or liabilities measured at fair value on a recurring basis. At December 31, 2016, we had warrant liabilities of $1.0 million that represented Level 3 liabilities under the hierarchy. In March 2017, these warrants were either exercised or expired, and we no longer have any outstanding warrants. 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 any outstanding warrant liabilities at fair value. The fair value is estimated using the expected volatility based on our historical volatility and is determined using probability weighted-average assumptions, when appropriate.

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
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, 2017 2016 2015 Volatility 71.2% 70.3% 83.9% Risk-free interest rate 2.0% 1.5% 2.1% Expected life of option 6.2 years 6.2 years 6.1 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, 2017, 2016 and 2015, in thousands, except per share data. Year ended December 31, 2017 2016 2015 Numerator: Net loss and comprehensive loss $ (32,241 ) $ (15,337 ) $ (16,422 ) Less: income from change in fair value of warrants — — (332 ) Net loss attributable to common stockholders used to calculate diluted net loss per share $ (32,241 ) $ (15,337 ) $ (16,754 ) Denominator: Weighted-average shares outstanding - Basic 112,053 84,715 82,144 Potentially dilutive common shares outstanding: Warrants — — 707 Weighted-average shares used to calculate diluted net loss per share 112,053 84,715 82,851 Basic – net loss per share $ (0.29 ) $ (0.18 ) $ (0.20 ) Dilutive – net loss per share $ (0.29 ) $ (0.18 ) $ (0.20 )
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, 2017 2016 2015 Stock options 8,919,113 9,236,228 7,052,642 Restricted stock units 1,648,986 1,201,159 1,069,100 Warrants — 1,893,527 2,810,000 10,568,099 12,330,914 10,931,742

Equipment (Tables)

Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Equipment	December 31, Equipment consists of (in thousands): 2017 2016 Laboratory equipment $ 6,262 $ 6,196 Office equipment and leasehold improvements 3,039 3,040 Process development equipment not yet in service 363 965 9,664 10,201 Accumulated depreciation (7,458 ) (7,596 ) $ 2,206 $ 2,605

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, All Other Investments [Abstract]
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 Balance January 1, 2017 $ 1,004 Settlements from exercise (276 ) Gain included in income from change in fair value of warrants (728 ) Balance December 31, 2017 $ —

Capitalization and Warrant Li24

Capitalization and Warrant Liability (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Common Stock Shares Reserved for Future Issuance	The following shares of common stock were reserved for future issuance: December 31 2017 2016 Stock-based compensation plans 16,952,125 17,940,618 Warrants to purchase common stock — 1,893,527 Shares issuable upon patent milestone 500,000 — 17,452,125 19,834,145

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
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 Weighted Outstanding January 1, 2015 6,383,457 $ 3.31 Granted 1,215,296 1.31 Exercised (32,439 ) 1.60 Forfeited / Terminated / Expired (513,672 ) 2.34 Outstanding December 31, 2015 7,052,642 3.05 Granted 2,840,000 2.13 Exercised (164,827 ) 1.56 Forfeited / Expired (491,587 ) 3.57 Outstanding December 31, 2016 9,236,228 2.76 Granted 2,596,480 1.47 Exercised (136,056 ) 1.50 Forfeited / Expired (2,777,539 ) 4.76 Outstanding December 31, 2017 8,919,113 $ 1.78 Vested during 2017 1,666,915 $ 1.78 Vested and exercisable at December 31, 2017 4,803,470 $ 1.86
Summarizes Information Concerning Options Outstanding and Options Vested and Exercisable	December 31, 2017 Options Outstanding Options Vested and Exercisable Exercise Price Number Weighted Weighted Number Weighted Weighted $1.01 – 1.96 6,326,094 7.73 $ 1.53 3,516,361 6.69 $ 1.58 $2.09 – 3.84 2.423.519 8.04 $ 2.24 1,117,609 7.53 $ 2.30 $4.00 – 5.28 169,500 1.09 $ 4.69 169,500 1.09 $ 4.69 8,919,113 4,803,470
Summary of Restricted Stock Unit Activity and Related Information	A summary of our restricted stock unit activity and related information is as follows: Number Weighted Outstanding January 1, 2015 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 Granted 933,552 2.19 Vested-common stock issued (732,720 ) 1.71 Forfeited / Expired (68,773 ) 1.90 Number Weighted Outstanding December 31, 2016 1,201,159 1.92 Granted 1,054,720 1.46 Vested-common stock issued (571,118 ) 1.75 Forfeited / Expired (35,775 ) 1.82 Outstanding December 31, 2017 1,648,986 $ 1.69 Vested/Issued cumulative at December 31, 2017 3,828,441 $ 1.71

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
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 2017 2016 Statutory Federal income tax rate 34.0 % 34.0 % State income taxes - net of Federal tax benefit 0.8 % 0.8 % Other permanent differences (5.5 %) (8.1 %) Valuation allowances 24.1 % (37.0 %) Federal rate change (57.9 %) 0.0 % Research and development - U.S. 4.5 % 10.3 % Research and development - Foreign 0.0 % 0.2 % Effective tax rate for the year 0.0 % 0.2 %
Components of Deferred Tax Assets	Significant components of our deferred tax assets are as follows (in thousands): December 31, 2017 2016 Net operating loss carryforwards $ 35,409 $ 44,929 Research and development credit carryforwards 7,301 6,017 Compensation expense 652 2,735 Other 1,467 1,266 Total deferred tax assets 44,829 54,947 December 31, 2017 2016 Valuation allowance for deferred tax assets (44,829 ) (54,772 ) Net deferred tax assets $ — $ 175

Quarterly Financial Data (una27

Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	The following table presents quarterly data for the years ended December 31, 2017 and 2016, in thousands, except per share data: 2017 First Second Third Fourth Full Year Revenues $ 1,470 $ 669 $ 399 $ 1,170 $ 3,708 Net loss $ (5,631 ) $ (6,267 ) $ (7,243 ) $ (13,100 ) $ (32,241 ) Basic net loss per common share $ (0.06 ) $ (0.06 ) $ (0.06 ) $ (0.11 ) $ (0.29 ) Diluted net loss per common share $ (0.06 ) $ (0.06 ) $ (0.06 ) $ (0.11 ) $ (0.29 ) 2016 First Second Third Fourth Full Year Revenues $ 15,458 $ 595 $ 311 $ 983 $ 17,347 Net income (loss) $ 4,750 $ (6,956 ) $ (6,004 ) $ (7,127 ) $ (15,337 ) Basic net income (loss) per common share $ 0.06 $ (0.08 ) $ (0.07 ) $ (0.08 ) $ (0.18 ) Diluted net income (loss) per common share $ 0.06 $ (0.08 ) $ (0.07 ) $ (0.10 ) $ (0.18 )

Background - Additional Informa

Background - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)Segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Accounting Policies [Abstract]
Number of business segments | Segment	1
Accumulated deficit	$ (350,630)	$ (318,279)
Cash and cash equivalents	$ 29,316	$ 14,753	$ 23,027	$ 26,127

Accounting Policies - Additiona

Accounting Policies - Additional Information (Detail)	Jan. 01, 2017USD ($)	Feb. 28, 2018USD ($)	Dec. 31, 2017USD ($)Facility	Dec. 31, 2016USD ($)$ / shares	Dec. 31, 2015USD ($)$ / shares	Dec. 31, 2017USD ($)Facility
Significant Accounting Policies [Line Items]
Contract revenue			$ 2,843,000	$ 16,238,000	$ 10,298,000
Liquid investments with a maturity			Three months or less
Accrued capital expenditures				100,000
Available for sale securities			$ 0			$ 0
Realized gains and losses			0
Payments for Royalties						0
Sublicense fees				300,000	$ 200,000
Gain from insurance proceeds, net				682,000
Liability for uncertain income tax			$ 0	$ 0		$ 0
Warrant exercise price per share | $ / shares				$ 1.01	$ 1.01
Accumulated deficit recognized due to adoption of new accounting policy	$ 100,000
Number of operating leases facilities that need to be evaluated under the ASU 2016-02 | Facility			2			2
Subsequent Event [Member]
Significant Accounting Policies [Line Items]
Insurance proceeds received in 2018		$ 300,000
Collaboration [Member]
Significant Accounting Policies [Line Items]
Contract revenue			$ 1,000,000	$ 600,000
Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of long-lived assets			3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of long-lived assets			10 years

Accounting Policies - Fair Valu

Accounting Policies - Fair Value of Stock-Based Compensation Awards (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Volatility	71.20%	70.30%	83.90%
Risk-free interest rate	2.00%	1.50%	2.10%
Expected life of option	6 years 2 months 12 days	6 years 2 months 12 days	6 years 1 month 6 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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net loss and comprehensive loss									$ (32,241)	$ (15,337)	$ (16,422)
Less: income from change in fair value of warrants											(332)
Net loss attributable to common stockholders used to calculate diluted net loss per share									$ (32,241)	$ (15,337)	$ (16,754)
Denominator:
Weighted-average shares outstanding - Basic									112,053,369	84,715,471	82,143,610
Potentially dilutive common shares outstanding:
Warrants											707,000
Weighted-average shares used to calculate diluted net loss per share									112,053,369	84,715,471	82,851,091
Basic - net loss per share	$ (0.11)	$ (0.06)	$ (0.06)	$ (0.06)	$ (0.08)	$ (0.07)	$ (0.08)	$ 0.06	$ (0.29)	$ (0.18)	$ (0.20)
Dilutive - net loss per share	$ (0.11)	$ (0.06)	$ (0.06)	$ (0.06)	$ (0.10)	$ (0.07)	$ (0.08)	$ 0.06	$ (0.29)	$ (0.18)	$ (0.20)

Accounting Policies - Instrumen

Accounting Policies - Instruments Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	10,568,099	12,330,914	10,931,742
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	8,919,113	9,236,228	7,052,642
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	1,648,986	1,201,159	1,069,100
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total		1,893,527	2,810,000

Equipment - Equipment (Detail)

Equipment - Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Equipment, Gross	$ 9,664	$ 10,201
Accumulated depreciation	(7,458)	(7,596)
Equipment, net	2,206	2,605
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Equipment, Gross	6,262	6,196
Office Equipment and Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Equipment, Gross	3,039	3,040
Process Development Equipment Not Yet in Service [Member]
Property, Plant and Equipment [Line Items]
Equipment, Gross	$ 363	$ 965

Equipment - Additional Informat

Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Disposal of obsolete equipment	$ 0.8	$ 0.6

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended			36 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Mar. 31, 2017
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Financial assets measured at fair value on recurring basis	$ 0			$ 0
Financial liabilities measured at fair value on recurring basis	0			0
Warrant liabilities		$ 1,004,000
Rent	$ 267,000
Lease expiration period	2019-03
Aggregate rent expense	$ 477,000	465,000	$ 467,000
Future annual minimum lease commitments for 2018	385,000			385,000
Future annual minimum lease commitments for 2019	75,000			75,000
Interest paid				$ 0
Belgium [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Rent	$ 185,000
Lease expiration period	2018-07
Fair Value Measurements, Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrant liabilities		$ 1,000,000			$ 0

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, 2017USD ($)
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Beginning Balance	$ 1,004
Settlements from exercise	(276)
Gain included in income from change in fair value of warrants	(728)
Ending Balance	$ 0

Collaborative Arrangements an37

Collaborative Arrangements and Revenue Recognition - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)Milestone
RTI Surgical Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Commercial milestone revenue	$ 1,000,000
RTI Surgical Inc [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash payment eligible to receive on achievement of certain commercial milestone	34,500,000
Healios License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Up-front cash payment received	15,000,000
Potential near-term payment received	10,000,000
License revenue	15,000,000
Healios License Agreement [Member] | Regulatory and Sales Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Commercial milestone revenue	$ 225,000,000
Number of future milestones achieved | Milestone	2
Healios License Agreement [Member] | Maximum [Member] | Regulatory and Sales Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum increase of current cost-sharing proceeds	3.00%
Chugai Collaboration [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Up-front cash payment received	$ 10,000,000

Capitalization and Warrant Li38

Capitalization and Warrant Liability - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Feb. 28, 2018	Jan. 31, 2018	Oct. 31, 2017	Feb. 28, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2017
Class of Warrant or Right [Line Items]
Common stock, shares authorized					300,000,000	150,000,000		300,000,000
Preferred stock, shares authorized					10,000,000	10,000,000
Preferred stock, shares issued					0	0
Net proceeds through issuance of common stock				$ 20,900	$ 37,287	$ 4,028	$ 10,310
Common stock share issued in public offering				22,772,300
Common stock offering price				$ 1.01
Warrant exercise price per share						$ 1.01	$ 1.01
Expiration						Mar. 31, 2017
Proceeds from warrants exercise					$ 1,862	$ 163	$ 976
Shares remaining for sale					17,452,125	19,834,145
Payment to acquire intellectual property rights			$ 500
Future additional payments to acquire intellectual property rights, each quarter			$ 250
Additional shares issuable upon issuance of intellectual property rights			500,000
Accrued License Fees [Member] | Cash Obligation [Member]
Class of Warrant or Right [Line Items]
Payment to acquire intellectual property rights					$ 1,000
Intellectual Property [Member]
Class of Warrant or Right [Line Items]
Stock issued during period, shares, issued for intellectual property rights			1,000,000
Stock issued during period, amount, issued for intellectual property rights			$ 2,300
Intellectual Property [Member] | Accrued License Fees [Member] | Contingent Obligation [Member]
Class of Warrant or Right [Line Items]
Stock issued during period, shares, issued for intellectual property rights					500,000
Stock issued during period, amount, issued for intellectual property rights					$ 900
Aspire Capital [Member]
Class of Warrant or Right [Line Items]
Net proceeds through issuance of common stock					$ 45,200
Common stock share issued in public offering					9,400,000	2,191,418	4,023,719
Issuance of common stock per share					$ 1.75	$ 1.84	$ 2.58
Subsequent Event [Member] | Aspire Capital [Member]
Class of Warrant or Right [Line Items]
Net proceeds through issuance of common stock	$ 1,000
Equity purchase agreement, value	$ 100,000
Equity purchase agreement, term	3 years
Common stock issued as commitment fees	450,000
Common stock registered for resale	24,700,000
Issuance of common stock per share	$ 2
Subsequent Event [Member] | Aspire Capital [Member] | 2015 Agreement [Member]
Class of Warrant or Right [Line Items]
Net proceeds through issuance of common stock	$ 4,500	$ 4,500
Shares remaining for sale	2,000,000

Capitalization and Warrant Li39

Capitalization and Warrant Liability - Common Stock Shares Reserved for Future Issuance (Detail) - shares	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance	17,452,125	19,834,145
Stock-Based Compensation Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance	16,952,125	17,940,618
Warrants To Purchase Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance		1,893,527
Shares Issuable Upon Patent Milestone [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance	500,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)Plan$ / sharesshares	Dec. 31, 2016USD ($)$ / shares	Dec. 31, 2015USD ($)$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of incentive plan | Plan	1
Common stock authorized for equity incentive plan | shares	20,035,000
Common stock shares issued | shares	4,266,556
Shares available for issuance | shares	6,384,026
Shares of common stock outstanding | shares	10,568,099
Stock-based compensation expense | $	$ 3,044	$ 2,868	$ 2,929
Weighted average fair value of options granted | $ / shares	$ 0.95	$ 1.35	$ 0.94
Total fair value of options vested | $	$ 2,000	$ 1,700	$ 1,200
Total unrecognized estimated compensation cost | $	$ 4,500
Weighted average contractual life of unvested options	8 years 10 months 10 days
Compensation cost related to unvested stock-based awards not yet recognized, expected year for recognition	2,021
Aggregate intrinsic value of fully vested option shares | $	$ 1,800
Restricted stock vested | $	1,000	$ 1,300	$ 1,800
Estimated compensation cost of unvested restricted stock | $	$ 2,700
Expired Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares issued | shares	232,622
Shares of common stock outstanding | shares	951,059

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity and Related Information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Options Outstanding, Beginning Balance	9,236,228	7,052,642	6,383,457
Number of Options, Granted	2,596,480	2,840,000	1,215,296
Number of Options, Exercised	(136,056)	(164,827)	(32,439)
Number of Options, Forfeited/Terminated/ Expired	(2,777,539)	(491,587)	(513,672)
Number of Options Outstanding, Ending Balance	8,919,113	9,236,228	7,052,642
Weighted Average Exercise Price Outstanding, Beginning Balance	$ 2.76	$ 3.05	$ 3.31
Number of Options, Vested during 2017	1,666,915
Weighted Average Exercise Price, Granted	$ 1.47	2.13	1.31
Number of Options, Vested and exercisable at December 31, 2017	4,803,470
Weighted Average Exercise Price, Exercised	$ 1.50	1.56	1.60
Weighted Average Exercise Price, Forfeited/Terminated/ Expired	4.76	3.57	2.34
Weighted Average Exercise Price Outstanding, Ending Balance	1.78	$ 2.76	$ 3.05
Weighted Average Exercise Price, Vested during 2017	1.78
Weighted Average Exercise Price, Vested and exercisable at December 31, 2017	$ 1.86

Stock-Based Compensation - Su42

Stock-Based Compensation - Summarizes Information Concerning Options Outstanding and Options Vested and Exercisable (Detail)	12 Months Ended
	Dec. 31, 2017$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, Number of Options | shares	8,919,113
Options Vested and Exercisable, Number of Options | shares	4,803,470
1.01 - 1.96 Exercise Price [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range	$ 1.01
Exercise price upper range	$ 1.96
Options outstanding, Number of Options | shares	6,326,094
Option Outstanding, Weighted Average Remaining Contractual Life	7 years 8 months 23 days
Options Outstanding, Weighted Average Exercise Price	$ 1.53
Options Vested and Exercisable, Number of Options | shares	3,516,361
Options Vested and Exercisable, Weighted Average Remaining Contractual Life	6 years 8 months 9 days
Options Vested and Exercisable, Weighted Average Exercise Price	$ 1.58
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	2,423,519
Option Outstanding, Weighted Average Remaining Contractual Life	8 years 15 days
Options Outstanding, Weighted Average Exercise Price	$ 2.24
Options Vested and Exercisable, Number of Options | shares	1,117,609
Options Vested and Exercisable, Weighted Average Remaining Contractual Life	7 years 6 months 10 days
Options Vested and Exercisable, Weighted Average Exercise Price	$ 2.30
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	169,500
Option Outstanding, Weighted Average Remaining Contractual Life	1 year 1 month 2 days
Options Outstanding, Weighted Average Exercise Price	$ 4.69
Options Vested and Exercisable, Number of Options | shares	169,500
Options Vested and Exercisable, Weighted Average Remaining Contractual Life	1 year 1 month 2 days
Options Vested and Exercisable, Weighted Average Exercise Price	$ 4.69

Stock-Based Compensation - Su43

Stock-Based Compensation - Summary of Restricted Stock Unit Activity and Related Information (Detail) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Restricted Stock Units, Outstanding, Beginning balance	1,201,159	1,069,100	1,889,267
Number of Restricted Stock Units, Granted	1,054,720	933,552	455,776
Number of Restricted Stock Units, Vested/issued	(571,118)	(732,720)	(1,032,979)
Number of Restricted Stock Units, Forfeited / Expired	(35,775)	(68,773)	(242,964)
Number of Restricted Stock Units, Outstanding, Ending balance	1,648,986	1,201,159	1,069,100
Weighted Average Fair Value, Beginning Balance	$ 1.92	$ 1.55	$ 1.70
Number of Restricted Stock Units, Vested/Issued Cumulative	3,828,441
Weighted Average Fair Value, Granted	$ 1.46	2.19	1.28
Weighted Average Fair Value, Vested/Issued	1.75	1.71	1.69
Weighted Average Fair Value, Forfeited/Expired	1.82	1.90	1.62
Weighted Average Fair Value, Ending Balance	1.69	$ 1.92	$ 1.55
Weighted Average Fair Value Vested and Exercisable	$ 1.71

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Income tax paid		$ 0
Statutory Federal income tax rate		34.00%	34.00%
Decrease in deferred income tax assets, net due to change in tax rate		$ 18,700,000
U.S. Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards		136,600,000
Research and development tax credit		7,300,000
Foreign [Member]
Income Taxes [Line Items]
Net operating loss carryforwards		19,900,000
State and City [Member]
Income Taxes [Line Items]
Net operating loss carryforwards		$ 69,400,000
Earliest Tax Year [Member] | U.S. Federal [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year		2,021
Tax credit carryforwards, expiration year		2,021
Earliest Tax Year [Member] | State and City [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year		2,018
Latest Tax Year [Member] | U.S. Federal [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year		2,037
Tax credit carryforwards, expiration year		2,037
Latest Tax Year [Member] | State and City [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year		2,037
Not Subject To Annual Limitations [Member] | U.S. Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards		$ 99,900,000
Research and development tax credit		7,300,000
Not Subject To Annual Limitations [Member] | State and City [Member]
Income Taxes [Line Items]
Net operating loss carryforwards		$ 69,400,000
Scenario, Plan [Member]
Income Taxes [Line Items]
Statutory Federal income tax rate	21.00%

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, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation [Line Items]
Statutory Federal income tax rate	34.00%	34.00%
State income taxes - net of Federal tax benefit	0.80%	0.80%
Other permanent differences	(5.50%)	(8.10%)
Valuation allowances	24.10%	(37.00%)
Federal rate change	(57.90%)	0.00%
Effective tax rate for the year	0.00%	0.20%
U.S. Federal [Member]
Effective Income Tax Rate Reconciliation [Line Items]
Research and development	4.50%	10.30%
Foreign [Member]
Effective Income Tax Rate Reconciliation [Line Items]
Research and development	0.00%	0.20%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 35,409	$ 44,929
Research and development credit carryforwards	7,301	6,017
Compensation expense	652	2,735
Other	1,467	1,266
Total deferred tax assets	44,829	54,947
Valuation allowance for deferred tax assets	$ (44,829)	(54,772)
Net deferred tax assets		$ 175

Profit Sharing Plan and 401(k47

Profit Sharing Plan and 401(k) Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Postemployment Benefits [Abstract]
Employer contribution for profit sharing plan	$ 0.3	$ 0.3	$ 0.3

Subsequent and Other Events - A

Subsequent and Other Events - Additional Information (Detail) - USD ($)	1 Months Ended
	Mar. 14, 2018	Feb. 28, 2017
Subsequent Event [Line Items]
Shares of common stock issued		22,772,300
Subsequent Event [Member] | Healios License Agreement [Member]
Subsequent Event [Line Items]
Expansion agreement, payment entitlement	$ 35,000,000
Expansion agreement, guaranteed payment	$ 10,000,000
Shares of common stock issued	12,000,000
Warrants issued to purchase additional shares of common stock	20,000,000
Warrants to purchase additional shares of common stock, value	$ 21,100,000
Warrants to purchase additional shares of common stock, price per share	$ 1.76
Maximum ownership percentage that Heallios will have have	19.90%

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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Revenues	$ 1,170	$ 399	$ 669	$ 1,470	$ 983	$ 311	$ 595	$ 15,458	$ 3,708	$ 17,347	$ 11,948
Net income (loss)	$ (13,100)	$ (7,243)	$ (6,267)	$ (5,631)	$ (7,127)	$ (6,004)	$ (6,956)	$ 4,750	$ (32,241)	$ (15,337)	$ (16,422)
Basic net income (loss) per common share	$ (0.11)	$ (0.06)	$ (0.06)	$ (0.06)	$ (0.08)	$ (0.07)	$ (0.08)	$ 0.06	$ (0.29)	$ (0.18)	$ (0.20)
Diluted net income (loss) per common share	$ (0.11)	$ (0.06)	$ (0.06)	$ (0.06)	$ (0.10)	$ (0.07)	$ (0.08)	$ 0.06	$ (0.29)	$ (0.18)	$ (0.20)

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance at Beginning of Year	$ 55,148	$ 49,284	$ 42,204
Additions		5,864	7,080
Deductions	(10,319)
Balance at End of Year	44,829	55,148	49,284
Allowance for Doubtful Accounts [Member]
Balance at Beginning of Year	376	363	352
Additions		13	11
Deductions	(376)
Balance at End of Year	0	376	363
Valuation Allowance of Deferred Tax Assets [Member]
Balance at Beginning of Year	54,772	48,921	41,852
Additions		5,851	7,069
Deductions	(9,943)
Balance at End of Year	$ 44,829	$ 54,772	$ 48,921