Athersys, Inc / New (ATHXQ) 10-K 31 Mar 23 2022 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Mar. 28, 2023	Jun. 30, 2022
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-33876
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-4864095
Entity Address, Address Line One	3201 Carnegie Avenue,
Entity Address, City or Town	Cleveland,
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	44115-2634
City Area Code	216
Local Phone Number	431-9900
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	ATHX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 71.2
Entity Common Stock, Shares Outstanding		18,448,489
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Registrant Name	ATHERSYS, INC / NEW
Entity Central Index Key	0001368148

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2022
Audit Information [Abstract]
Auditor Name	Ernst & Young LLP
Auditor Location	Cleveland, Ohio
Auditor Firm ID	42

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 9,038	$ 37,407
Accounts receivable from Healios	716	1,414
Unbilled accounts receivable from Healios	0	3,000
Prepaid clinical trial costs	2,747	2,861
Prepaid expenses and other	1,034	1,345
Total current assets	13,535	46,027
Operating right-of-use assets, net	7,846	8,960
Property and equipment, net	4,214	3,692
Deposits and other	2,136	1,505
Total assets	27,731	60,184
Current liabilities:
Accounts payable	27,765	15,781
Accounts payable to Healios	0	1,119
Operating lease liabilities, current	746	1,011
Accrued compensation and related benefits	1,090	4,133
Accrued clinical trial related costs	7,231	3,773
Accrued expenses and other	1,078	704
Deferred revenue Healios	0	3,340
Warrant liability	534	0
Total current liabilities	38,444	29,861
Operating lease liabilities, non-current	7,939	8,755
Advance from Healios	5,199	5,199
Stockholders’ equity:
Preferred stock, at stated value; 10,000,000 shares authorized, and no shares issued and outstanding at December 31, 2022 and 2021	0	0
Common stock, $0.001 par value; 600,000,000 shares authorized, with 17,986,147 and 9,713,767 shares issued and outstanding at December 31, 2022 and December 31, 2021, respectively	18	10
Additional paid-in capital	632,009	599,703
Accumulated deficit	(655,878)	(583,344)
Total stockholders’ equity	(23,851)	16,369
Total liabilities and stockholders’ equity	$ 27,731	$ 60,184

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Stockholders’ equity:
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	600,000,000	600,000,000
Common stock, shares issued (in shares)	17,986,147	9,713,767
Common stock, shares outstanding (in shares)	17,986,147	9,713,767

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues
Contract revenue from Healios	$ 5,325	$ 5,514	$ 1,432
Grant revenue	0	0	8
Total revenues	5,325	5,514	1,440
Costs and expenses
Research and development (including stock compensation expense of $3,037, $3,642 and $3,351 in 2022, 2021 and 2020, respectively)	65,031	71,080	62,994
General and administrative (including stock compensation expense of $3,166, $4,914 and $4,028 in 2022, 2021 and 2020, respectively)	15,883	20,065	15,888
Depreciation	1,420	1,427	890
Total costs and expenses	82,334	92,572	79,772
Loss from operations	(77,009)	(87,058)	(78,332)
Income from change in fair value of warrants, net	4,197	0	0
Other income (expense), net	278	103	(433)
Net loss	(72,534)	(86,955)	(78,765)
Comprehensive loss	$ (72,534)	$ (86,955)	$ (78,765)
Net loss per common share, basic (in dollars per share)	$ (6.07)	$ (9.69)	$ (10.50)
Net loss per common share, diluted (in dollars per share)	$ (6.07)	$ (9.69)	$ (10.50)
Weighted average shares outstanding, basic (in shares)	11,945	8,971	7,499
Weighted average shares outstanding, diluted (in shares)	11,945	8,971	7,499

Consolidated Statements of Op_2

Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Stock-based compensation expense	$ 6,200	$ 8,600	$ 7,400
Research and Development Expense
Stock-based compensation expense	3,037	3,642	3,351
General and Administrative Expense
Stock-based compensation expense	$ 3,166	$ 4,914	$ 4,028

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	Preferred Stock	Common Stock		Additional Paid-in Capital	Accumulated Deficit
Preferred stock shares, beginning balance (in shares) at Dec. 31, 2019			0
Beginning balance at Dec. 31, 2019		$ 23,271	$ 0	$ 6	[1]	$ 440,889	$ (417,624)
Beginning balance (in shares) at Dec. 31, 2019	[1]			6,391,663
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation		7,379				7,379
Issuance of common stock, net of issuance costs (in shares)	[1]			1,480,500
Issuance of common stock, net of issuance costs		72,782		$ 2	[1]	72,780
Issuance of common stock to Healios (in shares)	[1]			172,421
Issuance of common stock to Healios		7,574				7,574
Issuance of common stock under equity compensation plans (in shares)	[1]			34,359
Issuance of common stock under equity compensation plans		(879)				(879)
Net loss		(78,765)					(78,765)
Net and comprehensive loss		(78,765)					(78,765)
Preferred stock shares, ending balance (in shares) at Dec. 31, 2020			0
Ending balance at Dec. 31, 2020		31,362	$ 0	$ 8	[1]	527,743	(496,389)
Ending balance (in shares) at Dec. 31, 2020	[1]			8,078,943
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation		8,556				8,556
Issuance of common stock, net of issuance costs (in shares)	[1]			1,601,240
Issuance of common stock, net of issuance costs		64,263		$ 2	[1]	64,261
Issuance of common stock under equity compensation plans (in shares)	[1]			33,584
Issuance of common stock under equity compensation plans		(857)				(857)
Net loss		(86,955)					(86,955)
Net and comprehensive loss		$ (86,955)					(86,955)
Preferred stock shares, ending balance (in shares) at Dec. 31, 2021		0	0
Ending balance at Dec. 31, 2021		$ 16,369	$ 0	$ 10	[1]	599,703	(583,344)
Ending balance (in shares) at Dec. 31, 2021		9,713,767		9,713,767	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation		$ 6,203				6,203
Issuance of common stock, net of issuance costs (in shares)	[1]			6,402,835
Issuance of common stock, net of issuance costs		26,290		$ 6	[1]	26,284
Pre-funded warrant exercise (in shares)	[1]			1,797,270
Pre-funded warrant exercise		2		$ 2	[1]
Issuance of common stock under equity compensation plans (in shares)	[1]			72,275
Issuance of common stock under equity compensation plans		(181)				(181)
Net loss		(72,534)					(72,534)
Net and comprehensive loss		$ (72,534)					(72,534)
Preferred stock shares, ending balance (in shares) at Dec. 31, 2022		0	0
Ending balance at Dec. 31, 2022		$ (23,851)	$ 0	$ 18	[1]	$ 632,009	$ (655,878)
Ending balance (in shares) at Dec. 31, 2022		17,986,147		17,986,147	[1]
[1]Reflects the 1-for-25 reverse stock split that became effective August 26, 2022. Refer to Note A, “Organization and Business.”

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating activities
Net loss	$ (72,534)	$ (86,955)	$ (78,765)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and Amortization	1,420	1,427	890
Loss from impairment of assets	7,240	0	0
Compensation related to stock options	6,203	8,556	7,379
Operating right-of-use assets, net	0	235	0
Gain (loss) on sales of assets	(32)	0	0
Change in fair value of warrant liabilities	(4,197)	0	0
Changes in operating assets and liabilities:
Accounts receivable from Healios - billed and unbilled	3,700	(4,325)	856
Prepaid expenses, deposits and other	2,091	(1,605)	(2,126)
Accounts payable, accrued expenses and other	1,619	3,795	9,456
Deferred revenue	(3,340)	3,275	0
Accounts payable to Healios	(1,120)	(586)	637
Advance from Healios	0	(2)	(137)
Deferred revenue	0	0	0
Net cash used in operating activities	(58,950)	(76,185)	(61,810)
Investing activities
Proceeds from the sale of equipment	135	0	0
Purchases of equipment	(397)	(1,360)	(1,162)
Net cash used in investing activities	(262)	(1,360)	(1,162)
Financing activities
Proceeds from issuance of common stock, net of issuance cost	14,500	64,263	72,782
Proceeds from the issuance of common stock and warrants, net of issuance cost	16,520	0	0
Proceeds from the exercise of pre-funded warrants	2	0	7,574
Shares retained for withholding tax payments on stock-based awards	(179)	(857)	(879)
Net cash provided by financing activities	30,843	63,406	79,477
(Decrease) Increase in cash and cash equivalents	(28,369)	(14,139)	16,505
Cash and cash equivalents at beginning of year	37,407	51,546	35,041
Cash and cash equivalents at end of year	9,038	37,407	51,546
Non-cash investing activities:
Right-of-use assets obtained in exchange for lease liabilities	$ 0	$ 9,162	$ 0

Organization and Business

Organization and Business	12 Months Ended
	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Business	Organization and Business Athersys, Inc., including its consolidated subsidiaries (collectively, “we,” “us,” “Athersys,” and the “Company”) is a biotechnology company focused in the field of regenerative medicine and operates in one business segment. Our operations consist of research, clinical development, manufacturing and manufacturing process development activities, and our most advanced program is in a pivotal Phase 3 clinical trial. We expect that the results of our MASTERS-2 clinical trial, will have a significant impact, favorable or unfavorable, on our ability to access capital from potential third-party commercial partners or the equity capital markets. Depending on the nature of these results, we may accelerate or may delay certain programs. In the longer term, we will have to continue to generate additional capital to meet our needs until we would become cash flow positive as a result of the sales of our clinical products, if they are approved for marketing. Such capital would come from new and existing collaborations and the related license fees, milestones and potential royalties and grant-funding opportunities. Reverse stock split

Going Concern

Going Concern	12 Months Ended
	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Going Concern	Going ConcernWe have prepared our consolidated financial statements on a going concern basis, which assumes that we will realize our assets and satisfy our liabilities in the normal course of business. However, we have incurred net losses and have had negative operating cash flows each year since our inception in 1995. In addition, we have negative working capital of $24.9 million as of December 31, 2022. These factors, along with our forecasted future cash flows, indicate that we will be unable to meet our contractual commitments and obligations as they come due in the ordinary course of business within one year following the issuance of these financial statements. These factors, among others, raise substantial doubt about our ability to continue as a going concern within one year after the date that these financial statements are issued.At December 31, 2022, we had cash and cash equivalents of $9.0 million. We will require substantial additional funding to develop our MultiStem product candidate and to continue our operations. Significant additional capital will be required to continue our research and development programs, including progressing our clinical product candidates to potential commercialization and preparing for commercial-scale manufacturing and sales. If we are unable to obtain adequate financing, we likely would have to file for protection under the bankruptcy laws to continue to pursue potential transactions and conduct a wind down of our Company. If we decide to dissolve and liquidate our assets or to seek protection under the bankruptcy laws, it is unclear to what extent we will be able to pay our obligations, and, accordingly, it is further unclear whether and to what extent any resources will be available for distributions to stockholders. For the foreseeable future, our ability to continue our operations is dependent upon the ability to obtain additional funding through public or private equity offerings, debt financings, collaborations and/or licensing arrangements. However, there can be no assurance that we will be able to obtain such funding on terms acceptable to us, on a timely basis or at all, particularly in light of our current stock price and liquidity. If we are unable to obtain funding, we may be required to further delay, reduce or eliminate our MultiStem product candidate approval and commercialization efforts, which would adversely affect our business prospects, and we likely will be unable to continue operations. The accompanying consolidated financial statements do not include any adjustments to reflect the possible future effect on the recoverability and classification of assets or the amounts and classification of liabilities that may result from the outcome of the uncertainty concerning our ability to continue as a going concern.

Accounting Policies

Accounting Policies	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Accounting Policies	Accounting Policies Accounting Standards Adopted In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes , which simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The ASU is effective for fiscal years beginning after December 15, 2020. We adopted this ASU prospectively as of January 1, 2021 and the adoption of this ASU did not have a material impact on our consolidated financial statements and disclosures. Accounting Standards Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments (Topic 326) . This ASU replaces the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. Subsequent to issuing ASU 2016-13, the FASB issued ASU 2019-10, Financial Instruments - Credit Losses (Topic 326): Effective Dates , delaying the effective date for smaller reporting companies until January 2023. We are currently evaluating the potential impact of adoption of this standard on our consolidated financial statements and disclosures, and we do not intend to early adopt. 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. 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. Reclassification Certain reclassifications of prior period presentations have been made to conform to the current period presentation. Revenue Recognition Our license and collaboration agreements may contain multiple elements, including license and technology access fees, research and development funding, product supply revenue, service revenue, cost-sharing, milestones and royalties. The deliverables under our arrangements are evaluated under FASB Accounting Standards Codification No. 606 (“Topic 606”) which requires an entity to recognize revenue in a manner that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Milestone Payments 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 are recognized based on an assessment of the probability of milestone achievement 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. Since milestone payments in the Healios arrangement are generally related to development and commercial milestone achievement by Healios, we only include milestones that are unconditionally entitled to in the estimated transaction price of the Healios arrangement. Conditional or contingent milestones are constrained to the extent that a significant reversal of revenue could result in future periods. Refer to Note F, Collaborative Arrangements and Revenue Recognition, for further information. Grant Revenue Grant revenue, which is not within the scope of Topic 606 for our grant arrangements, consists of funding under cost reimbursement programs primarily from federal and non-profit foundation sources for qualified research and development activities performed by us, and as such, are not based on estimates that are susceptible to change. Such amounts are invoiced and recorded as revenue as grant-funded activities are performed, with any advance funding recorded as deferred revenue until the activities are performed. Contractual Right to Consideration and Deferred Revenue Amounts included in deferred revenue or contract assets are determined at the contract level, and for our Healios arrangement, such amounts are included in a contract asset or liability depending on the overall status of the arrangement. Amounts received from customers or collaborators in advance of our performance of services or other deliverables are included in deferred revenue, while amounts for performance of services or other deliverables in excess of the customer payment received are included in contract assets, with those accounts that are unconditional and billed being included in accounts receivable separate from contract assets. Grant proceeds received in advance of our performance under the grant is included in deferred revenue. 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. The carrying amount of our cash equivalents approximates fair value due to the short maturity of the investments. Research and Development Research and development expenditures, which consist primarily of costs associated with clinical trials, preclinical research, clinical product manufacturing and process development for manufacturing, personnel, legal fees 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. Clinical Trial Costs Clinical trial costs are accrued based on work performed by outside contractors that manage and perform the trials, and those that manufacture the investigational product. We obtain initial estimates of total costs based on enrollment of subjects, trial duration, project management estimates, manufacturing estimates, patient treatment costs and other activities. Actual costs may be charged to us and recognized as the tasks are completed by the contractor or, alternatively, may be invoiced in accordance with agreed-upon payment schedules and recognized based on 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. We have agreements with our primary contract manufacturing organization for the manufacture of our MultiStem product candidate to supply our planned and ongoing clinical trials. As of December 31, 2022, we owe this contract manufacturing organization approximately $20.3 million that is in our accounts payable balance as of year-end. We have prepaid and other assets of $2.7 million with this contract manufacturing organization. Royalty Payments and Sublicense Fees We are required to make royalty payments to certain parties based on our product sales under license agreements. No royalties were recorded during the year ended December 31, 2022, 2021 and 2020, since we have not yet generated sales revenue. We are also required to record sublicense fees from time-to-time in connection with license fees from collaborators and clinical and commercial milestone achievement. Sublicenses fees were not significant in 2022 and 2021, and we recorded sublicense fees of $0.1 million in research and development expenses in the consolidated statements of operations and comprehensive loss in the year ended December 31, 2020. Long-Lived Assets Property and equipment is stated at acquired cost net of depreciation and amortization. Laboratory and office equipment are depreciated on the straight-line basis over the estimated useful lives ( three 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 or related group of assets, 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. Leasing Arrangements We lease equipment, buildings and office space under operating lease arrangements. We have various supply agreements with third-party manufacturers, which involve the lease of manufacturing facilities and equipment, as defined in Topic 842. We have elected to separate lease and non-lease components for these arrangements. These manufacturing agreements have variable lease payments, which typically become binding once certain manufacturing milestones are achieved, and as such, are not included in right-of-use (“ROU”) assets and lease liabilities until such payments are no longer variable. We do not separate lease and non-lease components for all other currently existing asset classes. We apply the short-term lease exemption to all qualified lease agreements. The short-term lease exemption allows for the non-recognition of ROU assets and lease liabilities for leases with a term of twelve months or less. We determine if an arrangement is or contains a lease at contract inception and exercise judgment and apply certain assumptions when determining the discount rate, lease term and lease payments. Generally, we do not have knowledge of the discount rate implicit in the lease and, therefore, in most cases we use the incremental borrowing rate to compute the present value of future lease payments. The incremental borrowing rate is determined based on lease term and leased asset, and is adjusted for the impacts of collateral. The lease term includes the non-cancelable period of the lease plus any additional periods covered by an option to extend that we are reasonably certain to exercise, or an option to extend that is controlled by the lessor. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Payments for certain lease agreements are adjusted annually for changes in an index or rate. We had no finance leases, residual value guarantees, restrictive covenants, subleases or sale leaseback transactions at December 31, 2022 and 2021. All ROU assets are periodically reviewed for impairment losses. Refer to Note K, Leasing Arrangements , for further information. Patent Costs and Rights Costs of applying for, prosecuting and maintaining patents and patent rights are expensed to research and development expenses 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. Warrants 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. Refer to Note G, Capitalization and Warrant Instruments , for a discussion of common stock warrants. Concentration of Credit Risk Our accounts receivable are generally comprised of amounts due from collaborators and granting authorities and are subject to concentration of credit risk due to the absence of a large number of customers. At December 31, 2022 and 2021, our accounts receivable are due from Healios. We do not typically require collateral from our customers. Legal Matters We evaluate the development of legal matters on a regular basis and accrue a liability when we believe a loss is probable and the amounts can be reasonably estimated. Healios has alleged that we are in material breach of our Framework Agreement for, among other things, not meeting our supply obligations and cooperation and assistance obligations. We strongly disagree with Healios’ allegations and will continue to work with Healios to try to resolve this dispute. However, there can be no assurance that we will be able to resolve this dispute without legal proceedings. Stock-Based Compensation Compensation expense related to stock options granted is measured at the grant date based on the estimated fair value of the award and is recognized using the straight-line method over the requisite service period, for awards without performance conditions. We determine the estimated fair value of each stock option on the date of grant using the Black-Scholes option-pricing model. The expected term of stock options granted represent the period of time that stock option grants are expected to be outstanding. The risk-free interest rate is based on the U.S. Treasury yield for a period consistent with the expected term of the stock option at the time of the grant. We determine volatility by using our historical stock volatility. We account for forfeitures as they occur. We have never paid or declared dividends or paid dividends on our common stock and have no plans to do so in the foreseeable future. Changes in these assumptions may lead to variability with respect to the amount of stock compensation expense we recognize related to stock options. Stock-based compensation for an award with a performance condition is recognized when the achievement of such performance condition is determined to be probable. If the outcome of such performance condition is not determined to be probable or is not met, no compensation expense is recognized. Prior to June 2020, we used the “simplified” method to calculate the expected term of option grants. In June 2020, we modified our stock option awards for all then-current employees and directors by providing an extension to the period of time during which vested stock options can be exercised. The extension to the period of time during which stock options can be exercised also applies to all stock options granted after June 2020. Subsequent to the modification date, our stock options no longer qualify to use the “simplified” method, and the expected term of our option grants is determined based on the historical experience and patterns, as well as current trends as previously described. The fair value of our restricted stock units is 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. Restricted stock units generally vest over a four-year period. Refer to Note H, Stock-Based Compensation , for additional information. Stock option awards to employees typically vest over a four-year period, have an exercise price equal to the fair market value of a share of common stock on the grant date and have a contractual term of 10 years. The following weighted-average input assumptions were used in determining the fair value of our stock options granted: December 31, 2022 2021 2020 Volatility 83.0 % 75.2 % 72.2 % Risk-free interest rate 2.4 % 0.8 % 0.6 % Expected life of option 5.60 years 5.4 years 5.7 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, 2022 and 2021. Our policy is to recognize potential accrued interest and penalties related to the liability for uncertain tax benefits, if applicable, in income tax expense. Net operating loss and credit carryforwards since inception remain open to examination by taxing authorities and will for a period post utilization. Net Loss per Share Basic and diluted net loss per share have been computed using the weighted-average number of shares of common stock outstanding during the period. We have outstanding options, restricted stock units and warrants that were not used in the calculation of diluted net loss per share because to do so would be antidilutive. We have warrants outstanding to purchase an aggregate of 400,000 shares of our common stock that were issued to HEALIOS K.K. (“Healios”) in August 2021 and are not exercisable according to their terms. Additionally, we issued warrants to purchase 1,920,000, 2,000,000, and 10,009,090 shares of our common stock in August 2022, September 2022, and November 2022, respectively. Refer to Note G. Capitalization and Warrant Instruments , for a discussion of the common stock warrants. The following instruments, were excluded from the calculation of diluted net loss per share because their effects would be antidilutive: Years ended December 31, 2022 2021 2020 Stock options 1,203,029 921,160 725,903 Restricted stock units 772,151 79,308 94,749 Warrants 14,329,090 400,000 — 16,304,270 1,400,468 820,652

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Property and Equipment, net	Property and Equipment, net December 31, Property and equipment consists of (in thousands): 2022 2021 Laboratory equipment $ 7,576 $ 9,352 Office equipment and leasehold improvements 3,934 4,000 Process development equipment not yet in service 2,313 458 13,823 13,810 Accumulated depreciation and amortization (9,609) (10,118) $ 4,214 $ 3,692

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Financial Instruments	Financial Instruments Fair Value Measurements The Company evaluates its financial assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level in which to classify them for each reporting period. This requires judgements to be made. 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. Cash equivalents primarily consist of money market funds with overnight liquidity and no stated maturities. We classified cash equivalents as a Level 1 due to the short-term nature of these instruments and measured the fair value based on quoted prices in active markets for identical assets. Our Level 3 financial liabilities consist of the warrant liabilities for which there is no current market such that the determination of fair value requires judgement or estimation. Changes in fair value measurements categorized within Level 3 of the fair value hierarchy are analyzed each period based on changes in estimates or assumptions and recorded as appropriate. The Company uses the Black-Scholes option valuation model to value the Level 3 warrant liabilities at inception and on subsequent valuation dates. This model incorporates transaction detail such as the Company’s stock price, contractual terms, maturing, risk free rates as well as volatility. The unobservable input for the Level 3 warrant liabilities includes volatility, which is not significant to the fair value measurement of the warrant liabilities. A reconciliation of the beginning and ending balances for the warrant liabilities which are measured at fair value on a recurring basis using significant unobservable inputs (Level 3) is as follows (in thousands): Warrant Liabilities Balance June 30, 2022 — Issuance - Common Warrant Liabilities (3,940,000) Issuance - Pre-funded Warrant Liability (2,231,000) Exercise - Pre-funded Warrant Liability 2,231,000 Issuance - New Warrants (413,000) Fair Value Adjustment - September 30, 2022 2,406,000 Fair Value Adjustment - December 31, 2022 1,413,000 Balance December 31, 2022 (534,000)

Collaborative Arrangements and

Collaborative Arrangements and Revenue Recognition	12 Months Ended
	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborative Arrangements and Revenue Recognition	Collaborative Arrangements and Revenue Recognition Healios Collaboration In 2016, we entered into a license agreement (the “First License 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 Healios’ organ bud program, initially for transplantation to treat liver disease or dysfunction. Under the terms of the First License Agreement, Healios also obtained a right to expand the scope of the collaboration to include the exclusive rights to develop and commercialize MultiStem for the treatment of two additional indications in Japan which included acute respiratory distress syndrome (“ARDS”) and another indication in the orthopedic area, and all indications for the organ bud program. Under the collaboration, Healios is responsible for the development and commercialization of the MultiStem product in the licensed territories, and we provide manufacturing services to Healios, comprising the supply of product for its clinical trials, technology transfer services and services related to commercial readiness in Japan. In 2017, we signed a clinical trial supply agreement for delivering the planned manufacturing services for Healios’ clinical trial in Japan, entitled, “ Treatment Evaluation of Acute Stroke for Using in Regenerative Cell Elements ” (“TREASURE”). The clinical trial supply agreement was amended later that year to clarify the operational elements, terms and cost-sharing arrangement associated with our supply of clinical material and certain adjustments to potential milestone payments related to the clinical product supply for TREASURE. Also in 2017, we entered into a technology transfer services agreement with Healios, in which Healios provides financial support to establish a contract manufacturer in Japan to produce product for Healios’ use. Related to the technology transfer services agreement with Healios, at the request of Healios, we entered into a manufacturing services agreement with Nikon CeLL innovation (“NCLi”) a subsidiary of Nikon Corp. and a significant Healios shareholder. At that time, we also amended the First License Agreement to confer to Healios a limited license to manufacture MultiStem if we are acquired by a third-party. The technology transfer services agreement with Healios was complete as of September 2019 and NCLi continued to provide technology transfer services to us. In the fourth quarter of 2019, the Company and Healios entered into a memorandum of understanding (the “Memorandum”) to provide additional technology transfer services. In June 2018, as contemplated by the First License Agreement, Healios exercised its option to expand the collaboration and entered into the Collaboration Expansion Agreement (the “CEA”) that included new license agreements and rights that further broadened the collaboration. Under the CEA, Healios (i) expanded its First License Agreement to include ARDS in Japan, expanded the organ bud license to include all transplantation indications, and terminated Healios’ right to include a designated orthopedic indication per the First License Agreement; (ii) obtained a worldwide exclusive license, or the Ophthalmology License Agreement, for use of MultiStem product to treat certain ophthalmological indications; (iii) obtained an exclusive license in Japan, the Combination Product License Agreement, for use of the MultiStem product to treat diseases of the liver, kidney, pancreas and intestinal tissue through local administration of MultiStem in combination with iPSC-derived cells; (iv) obtained an exclusive, time-limited right of first negotiation (“ROFN Period”) to enter into an option for a license to develop and commercialize certain MultiStem treatments in China, which has since expired; and (v) an option for an additional non-therapeutic technology license, which has also expired. For each of the ischemic stroke indication and the ARDS indication, we may receive success-based regulatory filing and approval and sales milestones aggregating up to $225.0 million in aggregate for each indication, subject to potential milestone credits. Milestone payments are non-refundable and non-creditable towards future royalties or any other payment due from Healios. We may also receive tiered royalties on net product sales, starting in the low double digits and increasing incrementally into the high teens depending on net sales levels. For standalone products sold by Healios under the Ophthalmology License Agreement, we are entitled to receive success-based regulatory filing and approval and sales milestones aggregating up to $135.6 million and tiered royalties on net product sales in the single digits depending on net sales levels. For the combination products under the Ophthalmology License Agreement, we will be entitled to receive a low single-digit royalty, but no milestone payments. Under the Combination Product License Agreement, we are entitled to receive a low single-digit royalty on net sales of the combination product treatments, but no milestone payments. For the organ bud product, we are entitled to receive a fractional royalty percentage on net sales of the organ bud products. Under the CEA, the ROFN Period with respect to the option for a license in China was extended to June 30, 2019 in exchange for a $2.0 million payment from Healios that we received in December 2018. The extension payment will be applied as a credit against any potential milestone payments under the current licenses, subject to certain limitations. The ROFN Period expired on June 30, 2019. In connection with the entry into the CEA, we amended the terms of the Healios Warrant as addressed in Note G, Capitalization and Warrant Instruments . In August 2021, the Company and Healios entered into the Framework Agreement, which provided for clarification under and modified the existing agreements between the parties. It also provided Healios with deferral of certain milestone payments. Under the Framework Agreement, the Company was entitled to payments for reimbursable services of which $0.7 million and $1.4 million are included in accounts receivable from Healios at December 31, 2022 and 2021, respectively. In addition, under the Framework Agreement, the Company was entitled to a $3.0 million milestone payment from Healios and was obligated to pay Healios $1.1 million by December 31, 2022. In September 2022, we received $1.9 million from Healios, which represents the milestone payment net of amounts owed to Healios. Additionally, to assist Healios with the advancement of its ischemic stroke and ARDS programs in Japan, in September 2022, we granted to Healios, subject to the terms of the licensing agreement, a non-exclusive license to make and have made MultiStem for the treatment of ischemic stroke and ARDS worldwide solely for import for use in Japan. In connection with the execution of the Framework Agreement, the Cooperation Agreement was amended to extend certain customary standstill provisions until the conclusion of our 2023 annual meeting of stockholders. We also issued warrants ( the “2021 Warrants”) to Healios in connection with the Framework Agreement to purchase up to a total of 400,000 shares of our common stock. The 2021 Warrants are being accounted for as consideration paid or payable to a customer according to Topic 606, Revenue from Contracts with Customers , and Topic 718, Compensation Stock Compensation, under which the recognition of such equity instruments is required at the time that the underlying performance conditions become probable or are satisfied. As of December 31, 2022, the 2021 Warrants have not been recorded as the underlying performance conditions have not been satisfied and are not yet considered probable. Refer to Note G Capitalization and Warrant Instruments, for further information. Healios Revenue Recognition At the inception of the Healios arrangement and again each time that the arrangement has been modified, all material performance obligations were identified, which include (i) licenses to our technology, (ii) product supply services, and (iii) manufacturing services provided on Healios’ behalf. In order to determine the transaction price, in addition to the fixed payments, we estimate the amount of variable consideration utilizing the expected value or most likely amount method, depending on the facts and circumstances relative to the contract, and the estimates for variable consideration are reassessed each reporting period. We constrain, or reduce, the estimates of variable consideration if it is probable that a significant revenue reversal could occur in future periods. At inception and upon each date a modification has resulted under the Healios arrangement, once the estimated transaction price is established, amounts are allocated to each separate performance obligation on a relative standalone selling price basis. These performance obligations include any remaining, undelivered elements at the time of the modification and any new elements from a modification to the Healios arrangement as the conditions are not met for being treated as a separate agreement. For performance obligations satisfied over time, we apply an appropriate method of measuring progress each reporting period and, if necessary, adjust the estimates of performance and the related revenue recognition. Our services provided on Healios’ behalf are satisfied over time, and we recognize revenue in proportion to the contractual services provided, measured by costs incurred compared to total estimated costs. For performance obligations satisfied at a point in time (i.e., product supply), we recognize revenue upon delivery. Under the Framework Agreement, it was determined there was one performance obligation for services necessary for regulatory approvals, manufacturing readiness, and commercial launch in Japan. We determined the transaction price included estimated payments for reimbursable services to be performed by us for Healios and the $3.0 million milestone payment. We allocated the total transaction price to this one performance obligation. We began recognizing revenue in the third quarter of 2021 as the services were being performed. At December 31, 2022, the services related to this performance obligation are largely complete and consist of minimal close-out activities which are immaterial. The transaction price for the remaining close-out activities is immaterial at December 31, 2022. We recognized revenue of approximately $5.3 million for the twelve months ended December 31, 2022, $0.5 million for the twelve months ended December 31, 2021, and no revenue for the twelve months ended December 31, 2020 from performance obligations partially satisfied in previous periods. Accounts receivable from Healios Accounts receivable from Healios are related to our contracts and are recorded when the right to consideration is unconditional at the amount that management expects to collect. Accounts receivable from Healios do not bear interest if paid when contractually due, and payments are generally due within thirty Unbilled Accounts Receivable from Healios Unbilled accounts receivable from Healios represent amounts due to us under contractual arrangements and for which we have an unconditional right to consideration, but for which we have not yet invoiced Healios. At December 31, 2022, we had no unbilled accounts receivable from Healios. Deferred Revenue - Healios Amounts included in deferred revenue - Healios on the consolidated balance sheets, are considered a contract liability. During the twelve months ended December 31, 2022 and 2021, revenue recognized from contract liabilities as of the beginning of the respective period was $3.3 million and $0.1 million, respectively. No revenue was recognized during the twelve months ended December 31, 2020. At December 31, 2022, there is no contract liability included in deferred revenue - Healios. Advance from Healios In 2017, we amended the clinical trial supply agreement for the manufacturing of clinical product for TREASURE to clarify a cost-sharing arrangement. The proceeds from Healios that relate specifically to the cost-sharing arrangement may either (i) result in a reduction, as defined in the clinical trial supply agreement, in the proceeds we receive from Healios upon the achievement of two potential milestones and an increase to a commercial milestone under the First License Agreement for stroke or (ii) be repaid to Healios at our election, as defined in the clinical trial supply agreement. The cost-sharing proceeds received are recognized on the balance sheet as a non-current advance from customer until the related milestone is achieved, unless such amounts are repaid to Healios at our election, at which time, the culmination of the earnings process will be complete and revenue will be recognized. Disaggregation of Revenues We recognize license-related amounts, including upfront payments, exclusivity fees, additional disease indication fees, and development, regulatory and sales-based milestones, at a point in time when earned. Similarly, product supply revenue is recognized at a point in time, while service revenue is recognized when earned over time. The following table presents our contract revenues disaggregated by timing of revenue recognition and excludes royalty revenue (in thousands): Twelve Months Ended Twelve Months Ended Twelve Months Ended Point in Time Over Time Point in Time Over Time Point in Time Over Time Contract revenue from Healios: License fee revenue $ — $ — $ — $ — $ — $ — Product supply revenue 46 — 283 $ — 1,432 — Service revenue — 5,279 — $ 5,231 — — Total disaggregated revenues $ 46 $ 5,279 $ 283 $ 5,231 $ 1,432 $ —

Stockholders_ Equity and Warran

Stockholders’ Equity and Warrant Instruments	12 Months Ended
	Dec. 31, 2022
Equity [Abstract]
Stockholders’ Equity and Warrant Instruments	Stockholders’ Equity and Warrant Instruments In June 2021, our stockholders approved an amendment to our certificate of incorporation to increase the number of shares of the Company’s authorized common stock from 300,000,000 shares to 600,000,000 shares. At December 31, 2022 and December 31, 2021, we had 600,000,000 shares of common stock and 10,000,000 shares of undesignated preferred stock authorized. No shares of preferred stock have been issued as of December 31, 2022 and 2021. In April 2020, we completed an underwritten public offering of common stock generating net proceeds of approximately $53.7 million through the issuance of 1,023,500 shares of common stock at the offering price of $56.25 per share. The following shares, in thousands, of common stock were reserved for future issuance: December 31, 2022 2021 Stock-based compensation 2,267 1,128 Warrants to purchase common stock 14,329 400 16,596 1,528 August 2022 Securities Purchase Agreement On August 15, 2022, the Company entered into a placement agency agreement with A.G.P./Alliance Global Partners (“A.G.P”)., pursuant to which A.G.P. agreed to serve as exclusive placement agent for the issuance and sale of common stock and warrants. A.G.P. received a placement fee of approximately $0.8 million and approximately $0.1 million for the reimbursement of expenses. On August 15, 2022, the Company entered into a securities purchase agreement, (the “August 2022 Purchase Agreement”), with an investor, pursuant to which the Company agreed to issue and sell, in a registered direct offering, (i) an aggregate of 1,200,000 shares of the Company’s common stock, (ii) pre-funded warrants (the “August 2022 Pre-Funded Warrants”) exercisable for an aggregate of 720,000 shares of common stock and (iii) warrants (the “August 2022 Common Warrants”) exercisable for an aggregate of 1,920,000 shares of common stock, in combinations of one share of common stock or one August 2022 Pre-Funded Warrant and one August 2022 Common Warrant for a combined purchase price of $6.25 (less $0.0025 for any August 2022 Pre-Funded Warrant). Subject to certain ownership limitations, under the terms of the August 2022 Purchase Agreement, the August 2022 Pre-Funded Warrants were exercisable upon issuance, and the August 2022 Common Warrants were exercisable upon the six-month anniversary of issuance for a five-year period. Under the August 2022 Purchase Agreement, each August 2022 Pre-Funded Warrant was exercisable for one share of common stock at a price per share of $0.0025 and each August 2022 Common Warrant was exercisable for one share of common stock at a price per share of $6.385. The offering closed on August 17, 2022 and the Company received net proceeds of approximately $11.0 million, after giving effect to the payment of placement fees and expenses. On August 29, 2022, the August 2022 Pre-Funded Warrants were exercised in full and re-measured to fair value. Upon remeasurement and exercise, we recorded a gain of $0.8 million to adjust the warrant liability associated with the August 2022 Pre-Funded Warrants to fair value and reclassified the $3.8 million warrant liability to additional paid-in capital. The fair value adjustment is recorded in other income, net on the condensed consolidated statement of operations and comprehensive loss. Pursuant to the August 2022 Purchase Agreement, in the event the Company proposes a future offering to sell shares of common stock during the twelve months following the closing date, the investor has the right to participate in each offering in an amount up to 30.0%. On September 22, 2022, the Company entered into an amendment to the Purchase Agreement (the “August 2022 Purchase Agreement Amendment”) with the investor to, among other things, (i) amend the August 2022 Common Warrants to be exercisable for a seven-year period after the six-month anniversary of the closing date, (ii) reduce the standstill period, (iii) reduce the term and the amount of the participation right, and (iv) require the investor, subject to certain conditions, to participate in future offerings to sell certain securities to investors primarily for capital raising purposes. On September 22, 2022, in consideration of the August 2022 Purchase Agreement Amendment, and without receiving any cash proceeds, the Company issued to the investor additional warrants exercisable for 2,000,000 shares of common stock, the “New Warrants” at a price of $6.385 for a seven-year period after the six-month anniversary of the date of issuance thereof. November 2022 Securities Purchase Agreement On November 9, 2022, the Company entered into a placement agency agreement with A.G.P. pursuant to which A.G.P. agreed to serve as exclusive placement agent for the issuance and sale of common stock and warrants. A.G.P received a placement fee of approximately $0.4 million and approximately $0.1 million for the reimbursement of expenses. On November 9, 2022, the Company entered into a securities purchase agreement or “the November 2022 Purchase Agreement”, with investors, pursuant to which the Company agreed to issue and sell, in a public offering, (i) an aggregate of 3,927,275 shares of the Company’s common stock, (ii) pre-funded warrants (the “November 2022 Pre-Funded Warrants”) exercisable for an aggregate of 1,077,270 shares of common stock and (iii) warrants, (the “November 2022 Common Warrants”), exercisable for an aggregate of 10,009,090 shares of common stock, in combinations of one share of common stock or one November 2022 Pre-Funded Warrant and two November 2022 Common Warrants for a combined purchase price of $1.10 (less $0.0001 for any November 2022 Pre-Funded Warrant). Subject to certain ownership limitations, under the terms of the November 2022 Purchase Agreement, the November 2022 Pre-Funded Warrants and November 2022 Common Warrants were exercisable upon issuance. Under the November 2022 Purchase Agreement, each November 2022 Pre-Funded Warrant was exercisable for one share of common stock at a price per share of $0.0001 and each November 2022 Common Warrant is exercisable for one share of common stock at a price per share of $1.10 for a five-year period after the date of issuance. The offering closed on November 10, 2022 and the Company received net proceeds of approximately $5.0 million, after giving effect to the payment of placement fees and expenses. The November 2022 Pre-Funded Warrants were exercised in full at the closing. The Company has assessed the August 2022 Pre-Funded Warrants, the August 2022 Common Warrants and the New Warrants (collectively, the “August 2022 Warrants”) for appropriate equity or liability classification pursuant to the Company’s accounting policy as described in Note C. The August 2022 Warrants contain a provision pursuant to which the warrant holder has the option to receive cash in the event there is a fundamental transaction (contractually defined to include various merger, acquisition or stock transfer activities). The August 2022 Warrants meet the definition of a derivative pursuant to ASC 815 , Derivatives and Hedging, and do not meet the derivative scope exception. As a result, the August 2022 Warrants were initially recorded as liabilities and measured at fair value using the Black-Scholes valuation model. Issuance costs of $0.5 million were allocated to the August 2022 Pre-Funded Warrants and recorded in other income, net on the condensed consolidated statement of operations and comprehensive loss. The remaining issuance costs of $0.4 million were allocated to the common stock and recorded in additional paid-in capital. During the year ended December 31, 2022, the Company recognized a net gain of $3.8 million for the fair value adjustment related to the warrant liabilities, which includes a charge of $0.4 million recorded upon issuance of the New Warrants. As of December 31, 2022, the fair value of the warrant liabilities was $0.5 million. The November 2022 Common Warrants meet the requirements to be classified as equity in accordance with ASC 815, Derivatives and Hedging. The November 2022 Common Warrants were recorded at their relative fair value at issuance in the stockholders’ equity section of the balance sheet. Healios Investor Rights Agreement In March 2018, we entered into an investor rights agreement, (the “Investor Rights Agreement”), with Healios that governs certain of our and Healios’ rights relating to its ownership of our common stock. Under the Investor Rights Agreement, Healios is permitted to participate in certain equity issuances as a means to maintain its proportionate ownership of our common stock as of the time of such issuance. In May 2020, we entered into a purchase agreement with Healios, providing for Healios to purchase shares of our common stock in connection with certain equity issuances to Aspire Capital Fund, LLC, or “Aspire Capital”. Healios purchased 12,416 shares of our common stock at $43.00 per share for an aggregate purchase price of $0.5 million, in accordance with the terms of the Investor Rights Agreement. Under the Investor Rights Agreement, we further agreed that during such time as Healios beneficially owns more than 5.0% but less than 15.0% of our outstanding common stock, our Board of Directors, the Board, will nominate a Healios nominee suitable to us to become a member of the Board, and during such time as Healios beneficially owns 15.0% or more of our outstanding common stock, our Board will nominate two suitable Healios nominees to become members of the Board, at each annual election of directors. Healios nominated an individual to the Board, who was elected at the 2018 annual stockholders’ meeting. As a result of Healios’ investment, Healios became a related party, and the transactions with Healios are separately identified within these financial statements as related party transactions. In connection with the Framework Agreement, Healios agreed to terminate its existing right under the Investor Rights Agreement to nominate two nominees for election to the Board, if Healios beneficially owned 15.0% or more of our outstanding shares of common stock. Healios retains the right to appoint one nominee for election to the Board if Healios beneficially owns 5.0% or more of our outstanding shares of common stock. Healios Warrants In March 2018, we issued to Healios a warrant to purchase up to 800,000 shares of our common stock, (the “2018 Warrant”). Based upon the terms of the 2018 Warrant as amended in June 2018, it was no longer exercisable for up to 640,000 warrant shares as of June 2019. In March 2020, Healios elected to exercise the 2018 Warrant in full, and we issued 160,000 shares of our common stock at an exercise price equal to the reference price of $44.00 per share, as defined in the 2018 Warrant. Proceeds of approximately $7.0 million were received in April 2020 in accordance with the terms of the 2018 Warrant. In August 2021, we issued the 2021 Warrants to purchase up to an aggregate of 400,000 shares of our common stock. One of the 2021 Warrants is for the purchase of up to 120,000 shares at an exercise price of $45.00 per share, subject to specified increases, and generally is only exercisable within 60 days of receipt of either conditional or full marketing approval from the Pharmaceuticals and Medical Devices Agency in Japan, “PMDA”, for the intravenous administration of MultiStem to treat patients who are suffering from ARDS. The other 2021 Warrant is for the purchase of up to 280,000 shares at an exercise price of $60.00 per share, subject to specified increases, and generally is only exercisable within 60 days of receipt of either conditional or full marketing approval from the PMDA for the intravenous administration of MultiStem to treat patients who are suffering from ischemic stroke. The 2021 Warrants may be terminated by us under certain conditions and have an exercise cap triggered at Healios’ ownership of 19.9% of our common stock. Equity Purchase Agreement We previously had equity purchase agreements in place since 2011 with Aspire Capital that provided us the ability to sell shares to Aspire Capital from time to time. On May 12, 2022 we entered into an agreement, or “the 2022 Equity Facility”, that included Aspire Capital’s commitment to purchase up to an aggregate of $100.0 million of shares of our common stock over a defined timeframe. The terms of the 2022 Equity Facility were similar to the previous equity facilities with Aspire Capital. Our prior equity facility that was entered into in June 2021, or the 2021 Equity Facility, and includes Aspire Capital’s commitment to purchase up to an aggregate of $100.0 million of shares of our common stock over a defined timeframe. The terms of the 2021 Equity Facility are similar to the previous equity facilities with Aspire Capital, and we filed a registration statement for the resale of 1,600,000 shares of our common stock in connection with the 2021 Equity Facility. Our prior equity facility that was entered into in 2019, or the 2019 Equity Facility, was fully utilized and terminated during the third quarter of 2021. On July 6, 2022, Aspire Capital terminated the 2022 Equity Facility. Aspire Capital had the right to terminate the 2022 Equity Facility at the time or any time after any of the Company’s then current executive officers ceased to be an executive officer or full-time employee of the Company, which right was triggered in connection with the departures of William Lehmann, former president and Chief Operating Officer, John Harrington, Former Executive Vice President and Chief Scientific Officer, and Ivor MacLeod, former Chief Financial Officer. During the years ended December 31, 2022, 2021 and 2020, we sold 1,275,000, 1,601,240 and 457,000 shares, respectively, to Aspire Capital at average prices of $11.37, $40.23 and $41.75 per share, respectively.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation Our 2019 Equity and Incentive Compensation Plan (the “EICP”) authorized at inception an aggregate of approximately 1,700,000 shares of common stock for awards to employees, directors and consultants. The EICP was approved in June 2019 and replaced our prior long-term incentive plans. The EICP authorizes the issuance of stock-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, 2022, a total of 444,196 shares (including 11,289 shares related to an expired incentive plan) of common stock have been issued under our equity incentive plans. In June 2020, we modified option awards granted under the EICP and our prior equity plans for all then-current employees and directors by providing an extension to the period of time during which vested stock options can be exercised, subject to certain tenure-related conditions being met. The modification was applied to all then-outstanding nonqualified stock option awards outstanding on the modification date and to those incentive stock options held by individuals who accepted the modification. Following evaluation of the modification of the stock option awards, we recorded stock compensation expense of $1.2 million for the incremental value of stock option awards vested prior to the modification date. The remaining incremental value of $0.5 million determined at the modification date associated with the unvested stock option awards is being recognized over the remaining vesting period of these modified stock option awards. As of December 31, 2022, a total of 291,388 shares were available for issuance under our EICP, and stock-based awards representing 1,545,680 shares (including 28,575 shares related to an expired incentive plan) of common stock were outstanding. Additionally, inducement stock options granted outside of our equity incentive plans to purchase 429,500 shares of common stock were outstanding at December 31, 2022. We recognized $6.2 million, $8.6 million and $7.4 million of stock-based compensation expense in 2022, 2021 and 2020, respectively. Stock Options The weighted average fair value of options granted in 2022, 2021 and 2020 was $10.88, $28.08 and $40.15 per share, respectively. The total fair value of options vested during 2022, 2021 and 2020 was $4.1 million, $4.8 million and $3.5 million, respectively. No options were exercised during the year ended December 31, 2022, and the total intrinsic value of options exercised was not significant during the year ended December 31, 2021. The total intrinsic value of options exercised was $0.7 million during the year ended December 31, 2020. At December 31, 2022, total unrecognized estimated compensation cost related to unvested stock options was approximately $3.6 million, which is expected to be recognized by the end of 2026 using the straight-line method. The weighted average contractual life of unvested options at December 31, 2022 was 7.2 years. The aggregate intrinsic value of fully vested and exercisable option shares and option shares expected to vest as of December 31, 2022 not significant. A summary of our stock option activity and related information is as follows: Number Weighted Outstanding January 1, 2020 558,909 $ 44.35 Granted 208,519 61.04 Exercised (14,488) 42.54 Forfeited / Expired (27,037) 57.99 Outstanding December 31, 2020 725,903 48.67 Granted 249,599 45.14 Exercised (3,560) 37.74 Forfeited / Expired (50,332) 55.20 Outstanding December 31, 2021 921,610 47.38 Granted 556,464 16.43 Exercised — — Forfeited / Expired (275,045) 40.19 Outstanding December 31, 2022 1,203,029 $ 34.79 Vested during 2022 135,221 $ 49.68 Vested and exercisable at December 31, 2022 640,176 $ 47.69 December 31, 2022 Options Outstanding Options Vested and Exercisable Exercise Price Number Weighted Weighted Number Weighted Weighted $1.95 - $30.00 530,426 9.2 years $ 17.80 11,000 7.2 years $ 29.50 $30.01 - $50.00 380,589 2.4 years $ 39.13 344,882 2.0 years $ 38.97 $50.01 - $89.25 292,014 3.4 years $ 59.64 274,294 3.2 years $ 59.37 1,203,029 630,176 Restricted Stock Units A summary of our restricted stock unit activity and related information is as follows: Number Weighted Unvested January 1, 2020 81,077 $ 42.78 Granted 62,138 69.03 Vested-common stock issued (43,502) 49.57 Forfeited (4,964) 48.82 Unvested December 31, 2020 94,749 56.60 Granted 50,156 40.71 Vested-common stock issued (51,363) 52.18 Forfeited (14,234) 57.42 Unvested December 31, 2021 79,308 49.18 Granted 827,580 2.08 Vested-common stock issued (86,978) 23.69 Forfeited (47,759) 27.23 Unvested December 31, 2022 772,151 $ 2.92 Vested/Issued cumulative at December 31, 2022 402,215 $ 41.17 The total fair value of restricted stock units vested during 2022, 2021 and 2020 was $2.1 million, $2.7 million and $2.2 million, respectively. At December 31, 2022, total unrecognized estimated compensation cost related to unvested restricted stock units was approximately $2.0 million, which is expected to be recognized by the end of 2025 using the straight-line method.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes At December 31, 2022, we had U.S. federal net operating loss and research and development tax credit carryforwards of approximately $263.5 million and $24.4 million, respectively. Included in our federal net operating loss as of December 31, 2022 are federal net operating loss carryforwards generated after 2017 of $248.2 million that have an indefinite life, but with usage limited to 80% of taxable income in any given year. The remaining federal net operating losses and tax credits will expire at various dates between 2032 and 2041. We also had foreign net operating loss carryforwards of approximately $33.4 million. Such foreign net operating loss carryforwards do not expire. We also had state and city net operating loss carryforwards aggregating approximately $140.3 million. Such state and city net operating loss carryforwards may be used to reduce future taxable income and tax liabilities and will expire at various dates between 2023 and 2042. Certain state net operating losses do not expire. 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”). We generated U.S. federal net operating loss carryforwards of $348.1 million, research and development tax credits of $24.4 million, and state and local net operating loss carryforwards of $140.3 million since 2012. Utilization of some of the federal and state net operating loss and tax credit carryforwards generated after October 2012 may be subject to additional annual limitations due to the “change in ownership” provisions of the IRC and similar state provisions. The annual limitations may result in the expiration of net operating losses and credits before utilization. The Company has not performed a Section 382 study subsequent to October 2012 as of December 31, 2022 . 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 2022 2021 Statutory federal income tax rate 21.0 % 21.0 % State income taxes - net of federal tax benefit 0.9 % 1.0 % Unrealized G/L for warranty liability 1.2 % — % Executive Comp Limitation (1.4) % — % Other permanent differences (0.9) % (2.1) % Valuation allowances (25.2) % (24.8) % Research and development - U.S. 4.4 % 4.9 % Effective tax rate for the year — % — % Significant components of our deferred tax assets and liabilities are as follows (in thousands): December 31, 2022 2021 Deferred tax assets: Net operating loss carryforwards $ 80,355 $ 79,473 Research and development credit carryforwards 24,620 20,587 R&D expenses 10,260 $ — Operating lease liabilities 1,913 $ 1,918 Compensation expense 3,791 3,336 Other 3,540 2,618 Total deferred tax assets before valuation allowance 124,479 107,932 Valuation allowance for deferred tax assets (122,750) (106,186) Net deferred tax assets after valuation allowance 1,729 1,746 Deferred tax liabilities: Right-of-use asset (1,729) (1,746) Total deferred tax liabilities (1,729) (1,746) Net deferred tax assets $ — $ — Because of our cumulative losses, substantially all 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, 2022. We file income tax returns with the Internal Revenue Service (“IRS”) and certain other taxing jurisdictions. We are subject to income tax examinations by the IRS and by state tax authorities until the net operating losses are settled.

Profit Sharing and 401(k) Plan

Profit Sharing and 401(k) Plan	12 Months Ended
	Dec. 31, 2022
Postemployment Benefits [Abstract]
Profit Sharing and 401(k) Plan	Profit Sharing and 401(k) PlanWe 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 $0.4 million, $0.6 million and $0.5 million in 2022, 2021 and 2020, respectively.

Leasing Arrangements

Leasing Arrangements	12 Months Ended
	Dec. 31, 2022
Leases [Abstract]
Leasing Arrangements	Leasing ArrangementsAs of December 31, 2022 and 2021, ROU assets were $7.8 million and $9.0 million, respectively, and lease liabilities were $8.7 million and $9.8 million, respectively. The weighted-average remaining term for lease contracts was 8.4 years at December 31, 2022, 8.9 years at December 31, 2021 and 1.5 years at December 31, 2020. As of December 31, 2022, maturities ranged from 3 months to 102 months. The weighted-average discount rate was 9.0% at December 31, 2022, 8.8% at December 31, 2021, and 5.0% at December 31, 2020. We paid $1.8 million, $1.3 million and $0.5 million for operating leases included in the measurement of lease liabilities during the year ended December 31, 2022, 2021 and 2020, respectively. Warehouse Lease Agreement In January 2021, we entered into an operating lease agreement to lease approximately 214,000 square feet of warehouse and office space. The initial lease term is approximately ten years and includes five renewal options with terms of five years each. The lease commenced on May 1, 2021, upon us taking control of the warehouse and office space on that date. Base annual rent for the first year is approximately $1.3 million with 2.0% annual rent escalators. As of the lease commencement date, the right-of-use asset and corresponding operating lease liability was approximately $9.2 million, which represented the present value of remaining lease payments over the initial lease term, using an incremental borrowing rate of 9.0%. The terms of the lease agreement also include an allowance in the amount of $0.7 million for the cost of construction of office and laboratory space, some of which was completed as of December 31, 2022. We are also obligated to pay certain variable expenses separately from the base rent, including utilities, real estate taxes and common area maintenance. Such costs and have been excluded from the calculation of the right-of-use asset and corresponding operating lease liability and are being expensed in the period they are incurred. As of December 31, 2022, we have undertaken efforts to sublet our leased facility at Stow, Ohio. We have made no decision to exit the facility. We do not believe the right-of use asset related to the Stow lease is impaired. Lease Costs The table below presents certain information related to the lease costs (in thousands) for operating leases as of December 31, 2022, 2021 and 2020: Twelve months ended December 31, 2022 2021 2020 Operating lease cost $ 1,926 $ 1,458 $ 516 Short-term lease cost 116 134 111 Variable lease cost (1) 3,234 7,113 1,321 Total lease cost $ 5,276 $ 8,705 $ 1,948 (1) Includes lease components from our third-party manufacturing agreements. Undiscounted Cash Flows The following table summarizes future maturities (in thousands) for operating lease liabilities as of December 31, 2022: 2023 $ 1,502 2024 1,390 2025 1,404 2026 1,432 2027 1,461 2028 and beyond 5,342 Total minimum lease payments 12,531 Less: amount of lease payments representing interest 3,845 Present value of operating lease liabilities $ 8,686

Restructuring Charges

Restructuring Charges	12 Months Ended
	Dec. 31, 2022
Restructuring and Related Activities [Abstract]
Restructuring Charges	Restructuring Charges In June 2022, we announced a restructuring of our organization, including an approximate 70% reduction in our workforce. As part of the Plan we also announced changes to our executive team. Mr. Lehmann left the Company on May 31, 2022. Dr. Harrington and Mr. Macleod left the Company on June 30, 2022. The Company’s restructuring efforts are intended to preserve cash and reduce operating expenses going forward. In addition to the workforce reductions, the Company’s restructuring efforts include the reduction of our internal research function, the decommissioning of certain equipment and pausing our manufacturing and process development efforts toward commercializing our MultiStem product candidate. We are attempting to negotiate payment terms with our primary contract manufacturing organization responsible for the manufacture of Multistem and potential future restructuring charges, if any are not probable or estimable at December 31, 2022. The following table sets forth certain details associated with the restructuring charges incurred in the three and twelve months ended December 31, 2022 and the obligations recorded for the expenses associated with the Plan (in thousands). It is anticipated the Plan will be completed by mid-2023. Balances Cash Balances January 1, 2022 Charges (payments) December 31, 2022 Employee severance and benefits $ — $ 2,538,229 $ (1,603,170) $ 935,059 Legal and professional fees $ — $ 211,485 $ (188,700) $ 22,785 Other $ — $ 15,003 $ (15,003) $ — $ — $ 2,764,717 $ (1,806,873) $ 957,844 All of restructuring accrual is in current liabilities, in accrued compensation and related benefits and accounts payable. Restructuring charges of $1.5 million and $1.3 million are included in research and development costs and expenses and general and administrative costs and expenses, respectively, for the twelve months ended December 31, 2022.

Accounting Policies (Policies)

Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Accounting Standards Adopted and Accounting Standards Not Yet Adopted	Accounting Standards Adopted In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes , which simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. The ASU is effective for fiscal years beginning after December 15, 2020. We adopted this ASU prospectively as of January 1, 2021 and the adoption of this ASU did not have a material impact on our consolidated financial statements and disclosures. Accounting Standards Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments (Topic 326) . This ASU replaces the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. Subsequent to issuing ASU 2016-13, the FASB issued ASU 2019-10, Financial Instruments - Credit Losses (Topic 326): Effective Dates , delaying the effective date for smaller reporting companies until January 2023. We are currently evaluating the potential impact of adoption of this standard on our consolidated financial statements and disclosures, and we do not intend to early adopt.
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.
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.
Reclassification	ReclassificationCertain reclassifications of prior period presentations have been made to conform to the current period presentation.
Revenue Recognition	Revenue Recognition Our license and collaboration agreements may contain multiple elements, including license and technology access fees, research and development funding, product supply revenue, service revenue, cost-sharing, milestones and royalties. The deliverables under our arrangements are evaluated under FASB Accounting Standards Codification No. 606 (“Topic 606”) which requires an entity to recognize revenue in a manner that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Milestone Payments 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 are recognized based on an assessment of the probability of milestone achievement 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. Since milestone payments in the Healios arrangement are generally related to development and commercial milestone achievement by Healios, we only include milestones that are unconditionally entitled to in the estimated transaction price of the Healios arrangement. Conditional or contingent milestones are constrained to the extent that a significant reversal of revenue could result in future periods. Refer to Note F, Collaborative Arrangements and Revenue Recognition, for further information. Grant Revenue Grant revenue, which is not within the scope of Topic 606 for our grant arrangements, consists of funding under cost reimbursement programs primarily from federal and non-profit foundation sources for qualified research and development activities performed by us, and as such, are not based on estimates that are susceptible to change. Such amounts are invoiced and recorded as revenue as grant-funded activities are performed, with any advance funding recorded as deferred revenue until the activities are performed. Contractual Right to Consideration and Deferred Revenue
Cash and Cash Equivalents	Cash and Cash EquivalentsWe 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. The carrying amount of our cash equivalents approximates fair value due to the short maturity of the investments.
Research and Development	Research and Development Research and development expenditures, which consist primarily of costs associated with clinical trials, preclinical research, clinical product manufacturing and process development for manufacturing, personnel, legal fees 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.
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 those that manufacture the investigational product. We obtain initial estimates of total costs based on enrollment of subjects, trial duration, project management estimates, manufacturing estimates, patient treatment costs and other activities. Actual costs may be charged to us and recognized as the tasks are completed by the contractor or, alternatively, may be invoiced in accordance with agreed-upon payment schedules and recognized based on 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. We have agreements with our primary contract manufacturing organization for the manufacture of our MultiStem product candidate to supply our planned and ongoing clinical trials. As of December 31, 2022, we owe this contract manufacturing organization approximately $20.3 million that is in our accounts payable balance as of year-end. We have prepaid and other assets of $2.7 million with this contract manufacturing organization.
Royalty Payments and Sublicense Fees	Royalty Payments and Sublicense Fees We are required to make royalty payments to certain parties based on our product sales under license agreements. No royalties were recorded during the year ended December 31, 2022, 2021 and 2020, since we have not yet generated sales revenue. We are also required to record sublicense fees from time-to-time in connection with license fees from collaborators and clinical and commercial milestone achievement. Sublicenses fees were not significant in 2022 and 2021, and we recorded sublicense fees of $0.1 million in research and development expenses in the consolidated statements of operations and comprehensive loss in the year ended December 31, 2020.
Long-Lived Assets	Long-Lived Assets Property and equipment is stated at acquired cost net of depreciation and amortization. Laboratory and office equipment are depreciated on the straight-line basis over the estimated useful lives ( three 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 or related group of assets, 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.
Leasing Arrangements	Leasing Arrangements We lease equipment, buildings and office space under operating lease arrangements. We have various supply agreements with third-party manufacturers, which involve the lease of manufacturing facilities and equipment, as defined in Topic 842. We have elected to separate lease and non-lease components for these arrangements. These manufacturing agreements have variable lease payments, which typically become binding once certain manufacturing milestones are achieved, and as such, are not included in right-of-use (“ROU”) assets and lease liabilities until such payments are no longer variable. We do not separate lease and non-lease components for all other currently existing asset classes. We apply the short-term lease exemption to all qualified lease agreements. The short-term lease exemption allows for the non-recognition of ROU assets and lease liabilities for leases with a term of twelve months or less. We determine if an arrangement is or contains a lease at contract inception and exercise judgment and apply certain assumptions when determining the discount rate, lease term and lease payments. Generally, we do not have knowledge of the discount rate implicit in the lease and, therefore, in most cases we use the incremental borrowing rate to compute the present value of future lease payments. The incremental borrowing rate is determined based on lease term and leased asset, and is adjusted for the impacts of collateral. The lease term includes the non-cancelable period of the lease plus any additional periods covered by an option to extend that we are reasonably certain to exercise, or an option to extend that is controlled by the lessor. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Payments for certain lease agreements are adjusted annually for changes in an index or rate.
Patent Costs and Rights	Patent Costs and Rights Costs of applying for, prosecuting and maintaining patents and patent rights are expensed to research and development expenses 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.
Warrants	WarrantsWe 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.
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, 2022 and 2021, our accounts receivable are due from Healios. We do not typically require collateral from our customers.
Legal Matters	Legal Matters We evaluate the development of legal matters on a regular basis and accrue a liability when we believe a loss is probable and the amounts can be reasonably estimated.
Stock-Based Compensation	Stock-Based Compensation Compensation expense related to stock options granted is measured at the grant date based on the estimated fair value of the award and is recognized using the straight-line method over the requisite service period, for awards without performance conditions. We determine the estimated fair value of each stock option on the date of grant using the Black-Scholes option-pricing model. The expected term of stock options granted represent the period of time that stock option grants are expected to be outstanding. The risk-free interest rate is based on the U.S. Treasury yield for a period consistent with the expected term of the stock option at the time of the grant. We determine volatility by using our historical stock volatility. We account for forfeitures as they occur. We have never paid or declared dividends or paid dividends on our common stock and have no plans to do so in the foreseeable future. Changes in these assumptions may lead to variability with respect to the amount of stock compensation expense we recognize related to stock options. Stock-based compensation for an award with a performance condition is recognized when the achievement of such performance condition is determined to be probable. If the outcome of such performance condition is not determined to be probable or is not met, no compensation expense is recognized. Prior to June 2020, we used the “simplified” method to calculate the expected term of option grants. In June 2020, we modified our stock option awards for all then-current employees and directors by providing an extension to the period of time during which vested stock options can be exercised. The extension to the period of time during which stock options can be exercised also applies to all stock options granted after June 2020. Subsequent to the modification date, our stock options no longer qualify to use the “simplified” method, and the expected term of our option grants is determined based on the historical experience and patterns, as well as current trends as previously described. The fair value of our restricted stock units is 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. Restricted stock units generally vest over a four-year period. Refer to Note H, Stock-Based Compensation , for additional information.
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, 2022 and 2021. Our policy is to recognize potential accrued interest and penalties related to the liability for uncertain tax benefits, if applicable, in income tax expense. Net operating loss and credit carryforwards since inception remain open to examination by taxing authorities and will for a period post utilization.
Net Loss per Share	Net Loss per ShareBasic and diluted net loss per share have been computed using the weighted-average number of shares of common stock outstanding during the period.
Fair Value Measurements	Fair Value Measurements The Company evaluates its financial assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level in which to classify them for each reporting period. This requires judgements to be made. 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. Cash equivalents primarily consist of money market funds with overnight liquidity and no stated maturities. We classified cash equivalents as a Level 1 due to the short-term nature of these instruments and measured the fair value based on quoted prices in active markets for identical assets. Our Level 3 financial liabilities consist of the warrant liabilities for which there is no current market such that the determination of fair value requires judgement or estimation. Changes in fair value measurements categorized within Level 3 of the fair value hierarchy are analyzed each period based on changes in estimates or assumptions and recorded as appropriate. The Company uses the Black-Scholes option valuation model to value the Level 3 warrant liabilities at inception and on subsequent valuation dates. This model incorporates transaction detail such as the Company’s stock price, contractual terms, maturing, risk free rates as well as volatility. The unobservable input for the Level 3 warrant liabilities includes volatility, which is not significant to the fair value measurement of the warrant liabilities.

Accounting Policies (Tables)

Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Fair Value of Stock-Based Compensation Awards	The following weighted-average input assumptions were used in determining the fair value of our stock options granted: December 31, 2022 2021 2020 Volatility 83.0 % 75.2 % 72.2 % Risk-free interest rate 2.4 % 0.8 % 0.6 % Expected life of option 5.60 years 5.4 years 5.7 years Expected dividend yield 0.0 % 0.0 % 0.0 %
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: Years ended December 31, 2022 2021 2020 Stock options 1,203,029 921,160 725,903 Restricted stock units 772,151 79,308 94,749 Warrants 14,329,090 400,000 — 16,304,270 1,400,468 820,652

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, net	December 31, Property and equipment consists of (in thousands): 2022 2021 Laboratory equipment $ 7,576 $ 9,352 Office equipment and leasehold improvements 3,934 4,000 Process development equipment not yet in service 2,313 458 13,823 13,810 Accumulated depreciation and amortization (9,609) (10,118) $ 4,214 $ 3,692

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Schedule of Warrant Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs	A reconciliation of the beginning and ending balances for the warrant liabilities which are measured at fair value on a recurring basis using significant unobservable inputs (Level 3) is as follows (in thousands): Warrant Liabilities Balance June 30, 2022 — Issuance - Common Warrant Liabilities (3,940,000) Issuance - Pre-funded Warrant Liability (2,231,000) Exercise - Pre-funded Warrant Liability 2,231,000 Issuance - New Warrants (413,000) Fair Value Adjustment - September 30, 2022 2,406,000 Fair Value Adjustment - December 31, 2022 1,413,000 Balance December 31, 2022 (534,000)

Collaborative Arrangements an_2

Collaborative Arrangements and Revenue Recognition (Tables)	12 Months Ended
	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Contract Revenues Disaggregated by Timing of Revenue Recognition	The following table presents our contract revenues disaggregated by timing of revenue recognition and excludes royalty revenue (in thousands): Twelve Months Ended Twelve Months Ended Twelve Months Ended Point in Time Over Time Point in Time Over Time Point in Time Over Time Contract revenue from Healios: License fee revenue $ — $ — $ — $ — $ — $ — Product supply revenue 46 — 283 $ — 1,432 — Service revenue — 5,279 — $ 5,231 — — Total disaggregated revenues $ 46 $ 5,279 $ 283 $ 5,231 $ 1,432 $ —

Stockholders_ Equity and Warr_2

Stockholders’ Equity and Warrant Instruments (Tables)	12 Months Ended
	Dec. 31, 2022
Equity [Abstract]
Common Stock Shares Reserved for Future Issuance	The following shares, in thousands, of common stock were reserved for future issuance: December 31, 2022 2021 Stock-based compensation 2,267 1,128 Warrants to purchase common stock 14,329 400 16,596 1,528

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2022
Share-Based Payment Arrangement [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, 2020 558,909 $ 44.35 Granted 208,519 61.04 Exercised (14,488) 42.54 Forfeited / Expired (27,037) 57.99 Outstanding December 31, 2020 725,903 48.67 Granted 249,599 45.14 Exercised (3,560) 37.74 Forfeited / Expired (50,332) 55.20 Outstanding December 31, 2021 921,610 47.38 Granted 556,464 16.43 Exercised — — Forfeited / Expired (275,045) 40.19 Outstanding December 31, 2022 1,203,029 $ 34.79 Vested during 2022 135,221 $ 49.68 Vested and exercisable at December 31, 2022 640,176 $ 47.69
Summarizes Information Concerning Options Outstanding and Options Vested and Exercisable	December 31, 2022 Options Outstanding Options Vested and Exercisable Exercise Price Number Weighted Weighted Number Weighted Weighted $1.95 - $30.00 530,426 9.2 years $ 17.80 11,000 7.2 years $ 29.50 $30.01 - $50.00 380,589 2.4 years $ 39.13 344,882 2.0 years $ 38.97 $50.01 - $89.25 292,014 3.4 years $ 59.64 274,294 3.2 years $ 59.37 1,203,029 630,176
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 Unvested January 1, 2020 81,077 $ 42.78 Granted 62,138 69.03 Vested-common stock issued (43,502) 49.57 Forfeited (4,964) 48.82 Unvested December 31, 2020 94,749 56.60 Granted 50,156 40.71 Vested-common stock issued (51,363) 52.18 Forfeited (14,234) 57.42 Unvested December 31, 2021 79,308 49.18 Granted 827,580 2.08 Vested-common stock issued (86,978) 23.69 Forfeited (47,759) 27.23 Unvested December 31, 2022 772,151 $ 2.92 Vested/Issued cumulative at December 31, 2022 402,215 $ 41.17

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
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 2022 2021 Statutory federal income tax rate 21.0 % 21.0 % State income taxes - net of federal tax benefit 0.9 % 1.0 % Unrealized G/L for warranty liability 1.2 % — % Executive Comp Limitation (1.4) % — % Other permanent differences (0.9) % (2.1) % Valuation allowances (25.2) % (24.8) % Research and development - U.S. 4.4 % 4.9 % Effective tax rate for the year — % — %
Components of Deferred Tax Assets	Significant components of our deferred tax assets and liabilities are as follows (in thousands): December 31, 2022 2021 Deferred tax assets: Net operating loss carryforwards $ 80,355 $ 79,473 Research and development credit carryforwards 24,620 20,587 R&D expenses 10,260 $ — Operating lease liabilities 1,913 $ 1,918 Compensation expense 3,791 3,336 Other 3,540 2,618 Total deferred tax assets before valuation allowance 124,479 107,932 Valuation allowance for deferred tax assets (122,750) (106,186) Net deferred tax assets after valuation allowance 1,729 1,746 Deferred tax liabilities: Right-of-use asset (1,729) (1,746) Total deferred tax liabilities (1,729) (1,746) Net deferred tax assets $ — $ —

Leasing Arrangements (Tables)

Leasing Arrangements (Tables)	12 Months Ended
	Dec. 31, 2022
Leases [Abstract]
Components of Lease Costs	The table below presents certain information related to the lease costs (in thousands) for operating leases as of December 31, 2022, 2021 and 2020: Twelve months ended December 31, 2022 2021 2020 Operating lease cost $ 1,926 $ 1,458 $ 516 Short-term lease cost 116 134 111 Variable lease cost (1) 3,234 7,113 1,321 Total lease cost $ 5,276 $ 8,705 $ 1,948 (1) Includes lease components from our third-party manufacturing agreements.
Future Minimum Lease Payments for Operating Leases	The following table summarizes future maturities (in thousands) for operating lease liabilities as of December 31, 2022: 2023 $ 1,502 2024 1,390 2025 1,404 2026 1,432 2027 1,461 2028 and beyond 5,342 Total minimum lease payments 12,531 Less: amount of lease payments representing interest 3,845 Present value of operating lease liabilities $ 8,686

Restructuring Charges (Tables)

Restructuring Charges (Tables)	12 Months Ended
	Dec. 31, 2022
Restructuring and Related Activities [Abstract]
Schedule of Restructuring Reserve by Type of Expenses	The following table sets forth certain details associated with the restructuring charges incurred in the three and twelve months ended December 31, 2022 and the obligations recorded for the expenses associated with the Plan (in thousands). It is anticipated the Plan will be completed by mid-2023. Balances Cash Balances January 1, 2022 Charges (payments) December 31, 2022 Employee severance and benefits $ — $ 2,538,229 $ (1,603,170) $ 935,059 Legal and professional fees $ — $ 211,485 $ (188,700) $ 22,785 Other $ — $ 15,003 $ (15,003) $ — $ — $ 2,764,717 $ (1,806,873) $ 957,844

Organization and Business (Deta

Organization and Business (Details)		12 Months Ended
	Aug. 26, 2022	Dec. 31, 2022 segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of business segments		1
Reverse stock split, conversion ratio	0.04

Going Concern (Details)

Going Concern (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 9,038	$ 37,407
Working capital amount	$ (24,900)

Accounting Policies - Additiona

Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Nov. 30, 2022	Sep. 30, 2022	Aug. 31, 2022	Aug. 31, 2021	Mar. 31, 2018
Significant Accounting Policies [Line Items]
Prepaid clinical trial costs	$ 2,747,000	$ 2,861,000
Payments for royalties	0	0	$ 0
Sublicense fees	$ 100,000	100,000
Awards vesting period (in years)	4 years
Award expiration period (in years)	10 years
Liability for uncertain income tax	$ 0	$ 0
Shares called by warrants (in shares)								800,000
MultiStem Product
Significant Accounting Policies [Line Items]
Clinical trial costs	20,300,000
Prepaid clinical trial costs	$ 2,700,000
Healios Framework Agreement
Significant Accounting Policies [Line Items]
Shares called by warrants (in shares)				10,009,090	2,000,000	1,920,000	400,000
RSUs
Significant Accounting Policies [Line Items]
Awards vesting period (in years)	4 years
Minimum
Significant Accounting Policies [Line Items]
Estimated useful life of long-lived assets (in years)	3 years
Maximum
Significant Accounting Policies [Line Items]
Estimated useful life of long-lived assets (in years)	10 years

Accounting Policies - Fair Valu

Accounting Policies - Fair Value of Stock-Based Compensation Awards (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Volatility	83%	75.20%	72.20%
Risk-free interest rate	2.40%	0.80%	0.60%
Expected life of option (in years)	5 years 7 months 6 days	5 years 4 months 24 days	5 years 8 months 12 days
Expected dividend yield	0%	0%	0%

Accounting Policies - Instrumen

Accounting Policies - Instruments Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	16,304,270	1,400,468	820,652
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	1,203,029	921,160	725,903
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	772,151	79,308	94,749
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	14,329,090	400,000	0

Property and Equipment, net - S

Property and Equipment, net - Schedule of Property and Equipment, net (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 13,823	$ 13,810
Accumulated depreciation and amortization	(9,609)	(10,118)
Property and equipment, net	4,214	3,692
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	7,576	9,352
Office equipment and leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,934	4,000
Process development equipment not yet in service
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,313	$ 458

Property and Equipment, net - A

Property and Equipment, net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Loss from impairment of assets		$ 7,240	$ 0	$ 0
Disposal of obsolete equipment		$ 100
Accelerated depreciation	$ 500

Financial Instruments (Details)

Financial Instruments (Details) - Warrants - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2022	Sep. 30, 2022
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ 0
Fair Value Adjustment	$ 1,413	2,406
Ending balance	$ (534)
August 2022 Common Warrant
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Issuance		(3,940)
August 2022 Pre-Funded Warrants
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Issuance		(2,231)
Exercise		2,231
New Warrants
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Issuance		$ (413)

Collaborative Arrangements an_3

Collaborative Arrangements and Revenue Recognition - Additional Information (Details)	1 Months Ended				12 Months Ended
	Sep. 30, 2022 USD ($) shares	Aug. 31, 2021 USD ($) shares	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2017 milestone	Nov. 30, 2022 shares	Aug. 31, 2022 shares	Mar. 31, 2018 shares
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable from Healios					$ 716,000	$ 1,414,000
Shares called by warrants (in shares) | shares											800,000
Unbilled accounts receivable from Healios					0	3,000,000
Revenue recognized related to the advance from Healios					$ 3,300,000	100,000
Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable, payments due within period of invoicing					30 days
Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts receivable, payments due within period of invoicing					45 days
Healios
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential near-term payment received			$ 2,000,000
Healios | Regulatory and Sales Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential revenue from approvals and milestones				$ 225,000,000
Number of future milestones achieved | milestone								2
Ophthalmology License Agreement | Regulatory and Sales Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential revenue from approvals and milestones				$ 135,600,000
Healios Framework Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential revenue from milestones		$ 3,000,000
Milestones obligated to pay					$ 1,100,000
Received milestones payment	$ 1,900,000
Shares called by warrants (in shares) | shares	2,000,000	400,000							10,009,090	1,920,000
Revenue recognized from performance obligations satisfied in previous periods					5,300,000	$ 500,000	$ 0
Unbilled accounts receivable from Healios					$ 0

Collaborative Arrangements an_4

Collaborative Arrangements and Revenue Recognition - Summary of Revenues Disaggregated by Recognition at Point in Time and Over Time (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Total disaggregated revenues	$ 5,325	$ 5,514	$ 1,432
Point in Time | Healios
Disaggregation of Revenue [Line Items]
Total disaggregated revenues	46	283	1,432
Point in Time | Healios | License fee revenue
Disaggregation of Revenue [Line Items]
Total disaggregated revenues	0	0	0
Point in Time | Healios | Product supply revenue
Disaggregation of Revenue [Line Items]
Total disaggregated revenues	46	283	1,432
Point in Time | Healios | Service revenue
Disaggregation of Revenue [Line Items]
Total disaggregated revenues	0	0	0
Over Time | Healios
Disaggregation of Revenue [Line Items]
Total disaggregated revenues	5,279	5,231	0
Over Time | Healios | License fee revenue
Disaggregation of Revenue [Line Items]
Total disaggregated revenues	0	0	0
Over Time | Healios | Product supply revenue
Disaggregation of Revenue [Line Items]
Total disaggregated revenues	0	0	0
Over Time | Healios | Service revenue
Disaggregation of Revenue [Line Items]
Total disaggregated revenues	$ 5,279	$ 5,231	$ 0

Stockholders_ Equity and Warr_3

Stockholders’ Equity and Warrant Instruments - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands

1 Months Ended

12 Months Ended

Nov. 09, 2022

Sep. 22, 2022

Aug. 29, 2022

Aug. 17, 2022

Aug. 15, 2022

May 12, 2022

Aug. 31, 2021

May 31, 2020

Apr. 30, 2020

Mar. 31, 2020

Nov. 30, 2019

Mar. 31, 2018

Dec. 31, 2022

Dec. 31, 2021

Dec. 31, 2020

Jun. 30, 2022

Jun. 30, 2021

May 31, 2021

Class of Warrant or Right [Line Items]

Common stock, shares authorized (in shares)

600,000,000

600,000,000

600,000,000

300,000,000

Preferred stock, shares authorized (in shares)

10,000,000

10,000,000

Preferred stock, shares issued (in shares)

0

0

Shares called by warrants (in shares)

800,000

Income from change in fair value of warrants, net

$ 4,197

$ 0

$ 0

Reclass of warrant liability to additional paid-in capital upon exercise

2

Warrant issuance costs allocated to equity

400

Remaining exercisable warrants (in shares)

640,000

Proceeds from the exercise of pre-funded warrants

2

$ 0

$ 7,574

Warrants

Class of Warrant or Right [Line Items]

Fair value of warrant liabilities

(534)

$ 0

Healios

Class of Warrant or Right [Line Items]

Common stock issued upon exercise of warrant (in shares)

160,000

Common stock issued, price per share (in dollars per share)

$ 44

Proceeds from the exercise of pre-funded warrants

$ 7,000

Healios | Minimum

Class of Warrant or Right [Line Items]

Investor Rights Agreement, Board of Directors triggering event, ownership percentage in outstanding common stock

5%

Healios | Maximum

Class of Warrant or Right [Line Items]

Investor Rights Agreement, Board of Directors triggering event, ownership percentage in outstanding common stock

15%

August 2022 Pre-Funded Warrants

Class of Warrant or Right [Line Items]

Issuance costs allocated to warrant liabilities

500

New Warrants

Class of Warrant or Right [Line Items]

Income from change in fair value of warrants, net

$ 400

2021 Warrants

Class of Warrant or Right [Line Items]

Shares called by warrants (in shares)

400,000

2021 Warrants | Healios

Class of Warrant or Right [Line Items]

Ownership percentage in common stock for exercise cap to be triggered

19.90%

Warrant One

Class of Warrant or Right [Line Items]

Shares called by warrants (in shares)

120,000

Exercise price of warrant (in dollars per share)

$ 45

Exercise period (in days)

60 days

Warrant Two

Class of Warrant or Right [Line Items]

Shares called by warrants (in shares)

280,000

Exercise price of warrant (in dollars per share)

$ 60

Exercise period (in days)

60 days

Aspire Capital

Class of Warrant or Right [Line Items]

Common stock share issued (in shares)

1,275,000

1,601,240

457,000

Issuance of common stock per share (in dollars per share)

$ 11.37

$ 40.23

$ 41.75

April 2020 Public Stock Offering

Class of Warrant or Right [Line Items]

Net proceeds from public offering

$ 53,700

Shares issued and sold (in shares)

1,023,500

Offering price (in dollars per share)

$ 56.25

August 2022 Purchase Agreement

Class of Warrant or Right [Line Items]

Shares issued and sold (in shares)

1,200,000

Proceeds from the issuance of common stock and warrants, net of issuance cost

$ 11,000

Participation right percentage

30%

August 2022 Purchase Agreement | Common Stock

Class of Warrant or Right [Line Items]

Number of shares called by each warrant (in shares)

1

August 2022 Purchase Agreement | August 2022 Pre-Funded Warrants

Class of Warrant or Right [Line Items]

Shares issued and sold (in shares)

720,000

Number of shares called by each warrant (in shares)

1

Exercise price of warrant (in dollars per share)

$ 0.0025

Income from change in fair value of warrants, net

$ (800)

Reclass of warrant liability to additional paid-in capital upon exercise

$ 3,800

August 2022 Purchase Agreement | August 2022 Pre-Funded Warrants | Common Stock

Class of Warrant or Right [Line Items]

Number of shares called by each warrant (in shares)

1

August 2022 Purchase Agreement | August 2022 Common Warrant

Class of Warrant or Right [Line Items]

Shares issued and sold (in shares)

1,920,000

Number of shares called by each warrant (in shares)

1

Exercise price of warrant (in dollars per share)

$ 6.385

Warrants, exercisable period

6 months

Warrants term

5 years

August 2022 Purchase Agreement | August 2022 Common Warrant | Common Stock

Class of Warrant or Right [Line Items]

Number of shares called by each warrant (in shares)

1

August 2022 Purchase Agreement | August 2022 Warrant

Class of Warrant or Right [Line Items]

Exercise price of warrant (in dollars per share)

$ 6.25

Placement Agency Agreement With Alliance Global Partners | Alliance Global Partners

Class of Warrant or Right [Line Items]

Placement fee

$ 400

$ 800

Placement fee reimbursement

$ 100

$ 100

August 2022 Purchase Agreement Amendment | August 2022 Common Warrant

Class of Warrant or Right [Line Items]

Warrants, exercisable period

6 months

Warrants term

7 years

August 2022 Purchase Agreement Amendment | New Warrants

Class of Warrant or Right [Line Items]

Shares called by warrants (in shares)

2,000,000

Exercise price of warrant (in dollars per share)

$ 6.385

Warrants term

7 years

November 2022 Purchase Agreement

Class of Warrant or Right [Line Items]

Shares issued and sold (in shares)

3,927,275

Proceeds from the issuance of common stock and warrants, net of issuance cost

$ 5,000

November 2022 Purchase Agreement | Common Stock

Class of Warrant or Right [Line Items]

Number of shares called by each warrant (in shares)

1

November 2022 Purchase Agreement | November 2022 Pre-Funded Warrants

Class of Warrant or Right [Line Items]

Shares issued and sold (in shares)

1,077,270

Number of shares called by each warrant (in shares)

1

Exercise price of warrant, price difference (in dollars per share)

$ 0.0001

November 2022 Purchase Agreement | November 2022 Pre-Funded Warrants | Common Stock

Class of Warrant or Right [Line Items]

Number of shares called by each warrant (in shares)

1

November 2022 Purchase Agreement | November 2022 Common Warrants

Class of Warrant or Right [Line Items]

Shares issued and sold (in shares)

10,009,090

Number of shares called by each warrant (in shares)

1

Exercise price of warrant (in dollars per share)

$ 1.10

Warrants term

5 years

November 2022 Purchase Agreement | November 2022 Common Warrants | Common Stock

Class of Warrant or Right [Line Items]

Number of shares called by each warrant (in shares)

2

Securities Purchase Agreement with Healios | Healios

Class of Warrant or Right [Line Items]

Net proceeds from public offering

$ 500

Shares issued and sold (in shares)

12,416

Offering price (in dollars per share)

$ 43

2022 Equity Facility | Aspire Capital

Class of Warrant or Right [Line Items]

Number of shares committed to be purchased (in shares)

$ 100,000

2021 Equity Facility | Aspire Capital

Class of Warrant or Right [Line Items]

Number of shares committed to be purchased (in shares)

$ 100,000

Common stock registered for resale (in shares)

1,600,000

Stockholders_ Equity and Warr_4

Stockholders’ Equity and Warrant Instruments - Common Stock Shares Reserved for Future Issuance (Details) - shares	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares reserved for future issuance (in shares)	16,596,000	1,528,000
Stock-based compensation
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares reserved for future issuance (in shares)	2,267,000	1,128,000
Warrants to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares reserved for future issuance (in shares)	14,329,000	400,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 6.2	$ 8.6	$ 7.4
Total unrecognized compensation cost		$ 3.6
Weighted average fair value of options granted (in dollars per share)		$ 10.88	$ 28.08	$ 40.15
Total fair value of options vested		$ 4.1	$ 4.8	$ 3.5
Options, exercised (in shares)		0	3,560	14,488
Total intrinsic value of options exercised		$ 0	$ 0	$ 0.7
Weighted average contractual life of unvested options (in years)		7 years 2 months 12 days
Restricted stock vested, fair value		$ 2.1	$ 2.7	$ 2.2
Estimated compensation cost of unvested restricted stock		$ 2
2019 Equity and Incentive Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock authorized for equity incentive plan (in shares)					1,700,000
Common stock shares issued (in shares)		444,196
Shares available for issuance (in shares)		291,388
Shares of common stock outstanding (in shares)		1,545,680
Expired Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares issued (in shares)		11,289
Shares of common stock outstanding (in shares)		28,575
2019 Equity And Incentive Compensation Plan, Modification
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1.2
Total unrecognized compensation cost	$ 0.5
Inducement Awards Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock outstanding (in shares)		429,500

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity and Related Information (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Number of Options
Beginning Balance (in shares)	921,610	725,903	558,909
Granted (in shares)	556,464	249,599	208,519
Exercised (in shares)	0	(3,560)	(14,488)
Forfeited / Expired (in shares)	(275,045)	(50,332)	(27,037)
Ending Balance (in shares)	1,203,029	921,610	725,903
Vested during current period (in shares)	135,221
Vested and exercisable at period end (in shares)	640,176
Weighted Average Exercise Price
Beginning Balance (in dollars per share)	$ 47.38	$ 48.67	$ 44.35
Granted (in dollars per share)	16.43	45.14	61.04
Exercised (in dollars per share)	0	37.74	42.54
Forfeited / Expired (in dollars per share)	40.19	55.20	57.99
Ending Balance (in dollars per share)	34.79	$ 47.38	$ 48.67
Vested during current period (in dollars per share)	49.68
Vested and exercisable at period end (in dollars per share)	$ 47.69

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summarizes Information Concerning Options Outstanding and Options Vested and Exercisable (Details)	12 Months Ended
	Dec. 31, 2022 $ / shares shares
Options Outstanding
Number of options (in shares) | shares	1,203,029
Options Vested and Exercisable
Number of options (in shares) | shares	630,176
Range One
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range (in dollars per share)	$ 1.95
Exercise price upper range (in dollars per share)	$ 30
Options Outstanding
Number of options (in shares) | shares	530,426
Weighted Average Remaining Contractual Life	9 years 2 months 12 days
Weighted average exercise price (in dollars per share)	$ 17.80
Options Vested and Exercisable
Number of options (in shares) | shares	11,000
Weighted Average Remaining Contractual Life	7 years 2 months 12 days
Weighted average exercise price (in dollars per share)	$ 29.50
Range Two
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range (in dollars per share)	30.01
Exercise price upper range (in dollars per share)	$ 50
Options Outstanding
Number of options (in shares) | shares	380,589
Weighted Average Remaining Contractual Life	2 years 4 months 24 days
Weighted average exercise price (in dollars per share)	$ 39.13
Options Vested and Exercisable
Number of options (in shares) | shares	344,882
Weighted Average Remaining Contractual Life	2 years
Weighted average exercise price (in dollars per share)	$ 38.97
Range Three
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price lower range (in dollars per share)	50.01
Exercise price upper range (in dollars per share)	$ 89.25
Options Outstanding
Number of options (in shares) | shares	292,014
Weighted Average Remaining Contractual Life	3 years 4 months 24 days
Weighted average exercise price (in dollars per share)	$ 59.64
Options Vested and Exercisable
Number of options (in shares) | shares	274,294
Weighted Average Remaining Contractual Life	3 years 2 months 12 days
Weighted average exercise price (in dollars per share)	$ 59.37

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Restricted Stock Unit Activity and Related Information (Details) - RSUs - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Number of Restricted Stock Units
Beginning balance (in shares)	79,308	94,749	81,077
Granted (in shares)	827,580	50,156	62,138
Vested-common stock issued (in shares)	(86,978)	(51,363)	(43,502)
Forfeited (in shares)	(47,759)	(14,234)	(4,964)
Ending balance (in shares)	772,151	79,308	94,749
Vested/Issued cumulative at period end (in shares)	402,215
Weighted Average Fair Value
Beginning balance (in dollars per share)	$ 49.18	$ 56.60	$ 42.78
Granted (in dollars per share)	2.08	40.71	69.03
Vested-common stock issued (in dollars per share)	23.69	52.18	49.57
Forfeited (in dollars per share)	27.23	57.42	48.82
Ending balance (in dollars per share)	2.92	$ 49.18	$ 56.60
Vested/Issued cumulative at period end (in dollars per share)	$ 41.17

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Income tax paid	$ 0	$ 0	$ 0
U.S. Federal
Income Taxes [Line Items]
Net operating loss carryforwards	263,500,000
Research and development tax credit	24,400,000
U.S. Federal | Subject To Annual Limitations
Income Taxes [Line Items]
Net operating loss carryforwards	248,200,000
U.S. Federal | Not Subject To Annual Limitations
Income Taxes [Line Items]
Net operating loss carryforwards	348,100,000
Research and development tax credit	24,400,000
Foreign
Income Taxes [Line Items]
Net operating loss carryforwards	33,400,000
State and City
Income Taxes [Line Items]
Net operating loss carryforwards	140,300,000
State and City | Not Subject To Annual Limitations
Income Taxes [Line Items]
Net operating loss carryforwards	$ 140,300,000

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Federal Statutory Income Tax Rate to Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21%	21%
State income taxes - net of federal tax benefit	0.90%	1%
Unrealized G/L for warranty liability	1.20%	0%
Executive Comp Limitation	(1.40%)	0%
Other permanent differences	(0.90%)	(2.10%)
Valuation allowances	(25.20%)	(24.80%)
Research and development - U.S.	4.40%	4.90%
Effective tax rate for the year	0%	0%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating loss carryforwards	$ 80,355	$ 79,473
Research and development credit carryforwards	24,620	20,587
R&D expenses	10,260	0
Operating lease liabilities	1,913	1,918
Compensation expense	3,791	3,336
Other	3,540	2,618
Total deferred tax assets before valuation allowance	124,479	107,932
Valuation allowance for deferred tax assets	(122,750)	(106,186)
Net deferred tax assets after valuation allowance	1,729	1,746
Deferred tax liabilities:
Right-of-use asset	(1,729)	(1,746)
Total deferred tax liabilities	(1,729)	(1,746)
Net deferred tax assets	$ 0	$ 0

Profit Sharing and 401(k) Plan

Profit Sharing and 401(k) Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Postemployment Benefits [Abstract]
Employer contribution for profit sharing plan	$ 0.4	$ 0.6	$ 0.5

Leasing Arrangements - Addition

Leasing Arrangements - Additional Information (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2021 USD ($) renewalOption ft²	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	May 01, 2021 USD ($)
Lessee, Lease, Description [Line Items]
Operating right-of-use assets, net		$ 7,846	$ 8,960
Lease liabilities		$ 8,686	$ 9,800
Weighted average remaining lease term (in years)		8 years 4 months 24 days	8 years 10 months 24 days	1 year 6 months
Weighted average discount rate (percent)		9%	8.80%	5%
Payment for operating leases		$ 1,800	$ 1,300	$ 500
Payment due for base annual rent in first year		$ 1,502
Warehouse and office space
Lessee, Lease, Description [Line Items]
Operating right-of-use assets, net					$ 9,200
Lease liabilities					$ 9,200
Lease term (in months)	10 years
Number of square feet leased | ft²	214,000
Number of renewal options | renewalOption	5
Renewal term (in years)	5 years
Payment due for base annual rent in first year	$ 1,300
Retention stock option award vesting rights (as a percent)	2%
Borrowing rate					9%
Allowance					$ 700
Minimum
Lessee, Lease, Description [Line Items]
Lease term (in months)		3 months
Maximum
Lessee, Lease, Description [Line Items]
Lease term (in months)		102 months

Leasing Arrangements - Componen

Leasing Arrangements - Components of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease cost	$ 1,926	$ 1,458	$ 516
Short-term lease cost	116	134	111
Variable lease cost	3,234	7,113	1,321
Total lease cost	$ 5,276	$ 8,705	$ 1,948

Leasing Arrangements - Future M

Leasing Arrangements - Future Minimum Lease Payments for Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
2023	$ 1,502
2024	1,390
2025	1,404
2026	1,432
2027	1,461
2028 and beyond	5,342
Total minimum lease payments	12,531
Less: amount of lease payments representing interest	3,845
Present value of operating lease liabilities	$ 8,686	$ 9,800

Restructuring Charges - Additio

Restructuring Charges - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2022
Restructuring Cost and Reserve [Line Items]
Percentage of reduction in workforce	70%
Restructuring charges		$ 2,764,717
Research and Development Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges		1,500,000
General and Administrative Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 1,300,000

Restructuring Charges - Schedul

Restructuring Charges - Schedule of Restructuring Reserve (Details)	12 Months Ended
	Dec. 31, 2022 USD ($)
Restructuring Cost and Reserve [Line Items]
Beginning balance	$ 0
Restructuring Charges	2,764,717
Cash payments	(1,806,873)
Ending balance	957,844
Employee severance and benefits
Restructuring Cost and Reserve [Line Items]
Beginning balance	0
Restructuring Charges	2,538,229
Cash payments	(1,603,170)
Ending balance	935,059
Legal and professional fees
Restructuring Cost and Reserve [Line Items]
Beginning balance	0
Restructuring Charges	211,485
Cash payments	(188,700)
Ending balance	22,785
Other
Restructuring Cost and Reserve [Line Items]
Beginning balance	0
Restructuring Charges	15,003
Cash payments	(15,003)
Ending balance	$ 0