0001564590-21-007165 | 10-K | XBRL Viewer

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2020	Feb. 16, 2021	Jun. 30, 2020
Cover [Abstract]
Entity Registrant Name	PLUS THERAPEUTICS, INC.
Entity Central Index Key	0001095981
Trading Symbol	PSTV
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 5.4
Entity Common Stock, Shares Outstanding		21,106,217
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-34375
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0827593
Entity Address, Address Line One	4200 MARATHON BLVD
Entity Address, Address Line Two	SUITE 200
Entity Address, City or Town	AUSTIN
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	78756
City Area Code	(737)
Local Phone Number	255-7194
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement for its 2021 Annual Meeting of Stockholders, which will be filed with the United States Securities and Exchange Commission within 120 days of December 31, 2020, are incorporated by reference into Part III of this Annual Report on Form 10-K.

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 8,346	$ 17,552
Accounts receivable	0	1,169
Restricted cash		40
Inventories, net		107
Other current assets	829	957
Total current assets	9,175	19,825
Property and equipment, net	1,820	2,179
Operating lease right-use-of assets	636	781
Goodwill	372	372
Intangible assets, net	86
Other assets	16	72
Total assets	12,105	23,229
Current liabilities:
Accounts payable and accrued expenses	2,081	3,279
Operating lease liability	123	147
Term loan obligation, net of discount	6,335	11,060
Total current liabilities	8,539	14,486
Noncurrent operating lease liability	528	646
Warrant liability	7	6,929
Other noncurrent liabilities		8
Total liabilities	9,074	22,069
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 1,954 and 1,959 shares issued and outstanding in 2020 and 2019, respectively
Common stock, $0.001 par value; 100,000,000 shares authorized; 6,749,028 and 3,880,588 shares issued and outstanding in 2020 and 2019, respectively	7	4
Additional paid-in capital	436,535	426,426
Accumulated deficit	(433,511)	(425,270)
Total stockholders’ equity	3,031	1,160
Total liabilities and stockholders’ equity	$ 12,105	$ 23,229

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Development revenue:
Government contracts and other	$ 303	$ 6,998
Total development revenues	303	6,998
Operating expenses:
Research and development	2,700	5,365
General and administrative	6,406	5,290
Total operating expenses	9,887	10,655
Operating loss	(9,584)	(3,657)
Other income (expense):
Interest income	50	55
Interest expense	(1,107)	(1,855)
Change in fair value of liability instruments	2,400	3,407
Issuance cost of warrants	0	(1,233)
Total other expense	1,343	374
Loss from continuing operations	(8,241)	(3,283)
Loss from discontinued operations	0	(7,604)
Net loss	(8,241)	(10,887)
Loss from continuing operations	(8,241)	(3,283)
Beneficial conversion feature for convertible preferred stock	0	(554)
Net loss allocable to common stockholders - continuing operations	(8,241)	(3,837)
Net loss allocable to common stockholders - discontinued operations	0	(7,604)
Net loss allocable to common stockholders	$ (8,241)	$ (11,441)
Basic and diluted net loss per share attributable to common stockholders - continuing operations	$ (1.86)	$ (2.77)
Basic and diluted net loss per share attributable to common stockholders - discontinued operations	0	(5.49)
Net loss per share, basic and diluted	$ (1.86)	$ (8.27)
Basic and diluted weighted average shares used in calculating net loss per share attributable to common stockholders	4,427,835	1,384,012
In Process Research and Development [Member] \| Nano Tx Therapeutics [Member]
Operating expenses:
Research and development	$ 781	$ 0

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Nano Tx Therapeutics [Member]	Series C Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member] Series B Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member] Series B and C Convertible Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Nano Tx Therapeutics [Member]	Common Stock [Member] Series B Convertible Preferred Stock [Member]	Common Stock [Member] Series B and C Convertible Preferred Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Nano Tx Therapeutics [Member]	Additional Paid-in Capital [Member] Series C Convertible Preferred Stock [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2018	$ 5,225										$ 418,390			$ 1,218	$ (414,383)
Balance (in shares) at Dec. 31, 2018				4,606			296,609
Share-based compensation	127										127
Sale of common stock and pre-funded warrants, net of offering costs	4,421						$ 4				4,417
Sale of common stock and pre-funded warrants, net of offering costs (in shares)							3,000,000
Sale/Issuance of common stock	2,208										2,208
Sale/Issuance of common stock (in shares)							184,666
Conversion of Convertible Preferred Stock into common stock (share)						(2,647)				334,199
Exercise of warrants	490										490
Exercise of warrants (in shares)							65,114
Warrant liability reclasssified to equity due to exercise of warrants	794										794
Beneficial conversion feature related to Series C Convertible Preferred Stock			$ 554										$ 554
Accretion of beneficial conversion feature related to Series C Convertible Preferred Stock			$ (554)										$ (554)
Foreign currency translation adjustment and accumulated other comprehensive income	(1,218)													$ (1,218)
Net loss	(10,887)														(10,887)
Balance at Dec. 31, 2019	$ 1,160						$ 4				426,426				(425,270)
Balance (in shares) at Dec. 31, 2019	3,880,588			1,959			3,880,588
Share-based compensation	$ 247										247
Issuance of common stock, net of offering costs	3,882						$ 2				3,880
Issuance of common stock, net of offering costs (share)							2,150,113
Conversion of Convertible Preferred Stock into common stock (share)					(5)				37
Exercise of warrants	1,098						$ 1				1,097
Exercise of warrants (in shares)							487,521
Warrant liability reclasssified to equity due to exercise of warrants	4,504										4,504
Issuance of common stock for in process research and development acquired		$ 381										$ 381
Issuance of common stock for in process research and development acquired (in share)								230,769
Net loss	(8,241)														(8,241)
Balance at Dec. 31, 2020	$ 3,031						$ 7				$ 436,535				$ (433,511)
Balance (in shares) at Dec. 31, 2020	6,749,028			1,954			6,749,028

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows used in operating activities:
Net loss	$ (8,241)	$ (10,887)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	366	896
Amortization of deferred financing costs and debt discount	584	550
In process research and development acquired from NanoTx Therapeutics	781	0
Change in fair value of liability instruments	(2,400)	(3,407)
Share-based compensation expense	247	127
Inventory write off	107	0
Noncash lease expense	3	12
Loss on sale of business	0	6,508
Allocation of issuance cost associated with warrants	0	1,233
Increases (decreases) in cash caused by changes in operating assets and liabilities:
Accounts receivable	1,169	(1,203)
Inventories	0	259
Other current assets	126	(211)
Other assets	58	263
Accounts payable and accrued expenses	(1,234)	(28)
Deferred revenue	0	29
Other long-term liabilities	0	(47)
Net cash used in operating activities	(8,434)	(5,906)
Cash flows from (used in) investing activities:
Purchases of property and equipment and intangible assets	(93)	(67)
In process research and development acquired from NanoTx Therapeutics	(400)	0
Proceeds from sale of business	0	5,637
Net cash provided by (used in) investing activities	(493)	5,570
Cash flows from financing activities:
Principal payments of long-term obligations	(5,307)	(3,692)
Payment of financing lease liability	(117)	(131)
Proceeds from exercise of warrants	1,098	490
Proceeds from sale of common stock	4,007	15,964
Net cash (used in) provided by financing activities	(319)	12,631
Effect of exchange rate changes on cash and cash equivalents	0	(4)
Net increase (decrease) in cash and cash equivalents	(9,246)	12,291
Cash, cash equivalents, and restricted cash at beginning of period	17,592	5,301
Cash, cash equivalents, and restricted cash at end of period	8,346	17,592
Cash paid during period for:
Interest	567	1,188
Supplemental schedule of non-cash investing and financing activities:
Issuance costs paid in common stock	463	0
Common stock issued in payment for in process research and development	381	0
Unpaid offering cost	125	0
Reclassification of warrants liability to equity	4,504	794
Proceeds from sales of business, net, paid directly to lender for principal payment of long-term obligations	0	3,050
Offering cost paid in warrants	0	213
Fair value of Convertible Preferred Stock beneficial conversion feature	$ 0	$ 554

Organization and Operations

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Operations

1.	Organization and Operations

The Company

Plus Therapeutics, Inc. is a clinical-stage pharmaceutical company focused on the development, manufacture and commercialization of complex and innovative treatments for patients battling cancer and other life-threatening diseases.

Principles of Consolidation

The accompanying consolidated financial statements include the Company’s accounts and those of its subsidiaries. All significant intercompany transactions and balances have been eliminated in consolidation.

Up to the sale transactions as described below, the Company had five wholly-owned subsidiaries located in Japan, United Kingdom, Switzerland, India and Spain that have been established primarily to support our sales and marketing activities in these regions.

On March 30, 2019, the Company entered into an Asset and Share Sale and Purchase Agreement (the “Lorem Purchase Agreement”) with Lorem Vascular Pte. Ltd. (“Lorem”), pursuant to which, among other things, Lorem agreed to purchase the Company’s UK subsidiary, Cytori Ltd. (the “UK Subsidiary”), and the Company’s cell therapy assets (the “Cell Therapy Assets”), excluding such assets used in Japan or relating to the Company’s contract with the U.S. Department of Health and Human Service’s Biomedical Advanced Research and Development Authority (“BARDA”). Both the Company and Lorem made customary representations, warranties and covenants in the Lorem Purchase Agreement. The transaction was completed on April 24, 2019 and the Company received $4.0 million of cash proceeds, of which $1.7 million was used to pay down principal, interest and fees under the Loan and Security Agreement, dated May 29, 2015 (the “Loan and Security Agreement”), with Oxford Finance, LLC (“Oxford”).

On April 19, 2019, the Company entered into an Asset and Share Sale and Purchase Agreement (the “Shirahama Purchase Agreement”) with Seijirō Shirahama, pursuant to which, among other things, Mr. Shirahama agreed to purchase the Company’s Japanese subsidiary, Cytori Therapeutics, K.K. (the “Japanese Subsidiary”), and substantially all of the Company’s Cell Therapy assets used in Japan. Both the Company and Mr. Shirahama made customary representations, warranties and covenants in the Shirahama Purchase Agreement. The transaction was completed on April 25, 2019 and the Company received $3.0 million of cash proceeds, of which $1.4 million was used to pay down principal, interest and fees under the Loan and Security Agreement (defined in Note 4).

Amendments to Certificate of Incorporation and Reverse Stock Split

On July 29, 2019, the Company amended its Certificate of Incorporation with the State of Delaware to change its corporate name from Cytori Therapeutics, Inc. to Plus Therapeutics, Inc. The Company also changed its trading symbol for its common stock on the Nasdaq Capital Market to “PSTV”.

On August 5, 2019, following stockholder and Board approval, the Company filed a Certificate of Amendment to its Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware to effectuate a one-for-fifty (1:50) reverse stock split of its common stock, par value $0.001 per share, without any change to its par value. Proportional adjustments for the reverse stock split were made to the Company's outstanding stock options, warrants and equity incentive plans for all periods presented.

Certain Risks and Uncertainties

The Company’s prospects are subject to the risks and uncertainties frequently encountered by companies in the early stages of development and commercialization, especially those companies in rapidly evolving and technologically advanced industries such as the biotech/medical device field. The Company’s future viability largely depends on its ability to complete development of new products and receive regulatory approvals for those products. No assurance can be given that the Company’s new products will be successfully developed, regulatory approvals will be granted, or acceptance of these products will be achieved.

Liquidity and Going Concern

The Company incurred net losses of $8.2 million for the year ended December 31, 2020, and as of December 31, 2020, the Company had an accumulated deficit of $433.5 million and cash and cash equivalents of $8.3 million. Additionally, the Company used net cash of $8.4 million to fund its operating activities for the year ended December 31, 2020. In addition, as discussed in Note 13, the full magnitude of the coronavirus pandemic on the Company’s financial condition, liquidity and future results of operations is uncertain. These factors raise substantial doubt about the Company’s ability to continue as a going concern.

On October 23, 2020, the Company entered into an Equity Distribution Agreement (the “Distribution Agreement”) with Canaccord Genuity LLC (“Canaccord”), pursuant to which the Company may issue and sell, from time to time, shares of our common stock having an aggregate offering price of up to $10,000,000 (the “ATM Shares”), depending on market demand, with Canaccord acting as an agent for sales. The Company has no obligation to sell any of the ATM Shares. The Company may instruct Canaccord not to sell the ATM Shares if the sales cannot be effected at or above the price the Company designates from time to time and the Company may at any time suspend sales pursuant to the Distribution Agreement. During the year ended December 31, 2020, the Company issued 1,616,299 shares of its common stock for aggregate net proceeds of $3.2 million. During 2021 and through the date of filing of this Form 10-K, the Company issued 536,070 shares under the Distribution Agreement for net proceeds of $1.5 million.

On September 30, 2020, the Company entered into a purchase agreement (the “2020 Purchase Agreement”) and registration rights agreement pursuant to which Lincoln Park Capital Fund LLC (“Lincoln Park”) has committed to purchase up to $25.0 million of the Company’s common stock. Under the terms and subject to the conditions of the 2020 Purchase Agreement, the Company has the right, but not the obligation, to sell to Lincoln Park, and Lincoln Park is obligated to purchase up to $25.0 million of the Company’s common stock. Such sales of common stock by the Company, if any, will be subject to certain limitations, and may occur from time to time, at the Company’s sole discretion, over the 36-month period commencing on the date that the registration statement covering the resale of shares of common stock that have been and may be issued under the 2020 Purchase Agreement, is declared effective by the SEC and a final prospectus in connection therewith is filed. During the year ended December 31, 2020, the Company sold 353,113 shares, excluding 180,701 shares issued as commitment fee, of common stock under the 2020 Purchase Agreement for net proceeds of $0.7 million. During 2021 and through the date of filing of this Form 10-K, the Company issued 985,186 shares of its common stock under the 2020 Purchase Agreement for total proceeds of $2.9 million.

In September 2019, the Company finalized the indirect cost rate under the contract we were awarded in September 2012 with the Biomedical Advanced Research and Development Authority, or BARDA, a division of the U.S. Department of Health and Human Services (the “BARDA Agreement”), for indirect costs incurred during the years 2012 through 2019, which resulted in approximately $4.6 million of revenue recognized during the year ended December 31, 2019.

In September 2019, the Company entered into an underwriting agreement with H.C. Wainwright & Co., LLC (the “Representative”), as representative of the underwriters (the “Underwriters”), pursuant to which the Company sold in an underwritten public offering an aggregate of (i) 289,000 Class A Units, each consisting of one share of common stock, par value $0.001 per share, of the Company and one Series U warrant to purchase one share of common stock, and (ii) 2,711,000 Class B Units, each consisting of one pre-funded Series V warrant to purchase one share of common stock and one Series U Warrant to purchase one share of common stock at a public offering price of $5.00 per Class A Unit and $4.9999 per Class B Unit (the “September 2019 Offering”). In addition, the Company granted the Underwriters a 45-day option to purchase up to an additional 450,000 shares of the Company’s common stock and/or Series U Warrants at the public offering price, less the underwriting discounts and commissions. The Underwriters exercised their option to purchase an additional 450,000 Series U warrants. The Company also issued to the Representative warrants (in the form of the Series U warrants) to purchase 75,000 shares of common stock with an exercise price of $6.25 per share of common stock (the “Representative Warrants”).

On April 24, 2019, the Company received $3.3 million of net cash proceeds related to the sale of the UK Subsidiary and the Cell Therapy Assets (excluding such assets used in Japan or relating to the Company’s contract with BARDA), of which $1.7 million was used to pay down principal, interest and fees on the Loan and Security Agreement, and on April 25, 2019 the Company received $2.4 million of net cash proceeds related to the sale of the Japanese Subsidiary, and substantially all of the Company’s Cell Therapy assets used in Japan, of which $1.4 million was used to pay down principal, interests and fees on the Loan and Security Agreement.

The Company continues to seek additional capital through strategic transactions and from other financing alternatives. Without additional capital, the Company’s current working capital will not provide adequate funding to make debt repayments or support its research, and product development activities at their current levels. If sufficient capital is not raised, the Company will at a minimum need to significantly reduce or curtail its research and development and other operations, and this would negatively affect its ability to achieve corporate growth goals.

Should the Company fail to raise additional cash from outside sources, this would have a material adverse impact on its operations.

The accompanying consolidated financial statements have been prepared assuming the Company will continue to operate as a going concern, which contemplates the realization of assets and settlement of liabilities in the normal course of business, and do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classifications of liabilities that may result from uncertainty related to its ability to continue as a going concern.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of Significant Accounting Policies

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions affecting the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the reporting period. The most significant estimates and critical accounting policies involve reviewing assets for impairment, determining the assumptions used in measuring share-based compensation expense, valuing warrants and valuing allowances for doubtful accounts.

Actual results could differ from these estimates. Management’s estimates and assumptions are reviewed regularly, and the effects of revisions are reflected in the consolidated financial statements in the periods they are determined to be necessary.

Cash and cash equivalents

The Company considers all highly liquid investments with maturities of three months or less at the time of purchase to be cash equivalents.

Cash and cash equivalents includes cash in readily available checking and savings accounts. The Company held no investments as of December 31, 2020 and 2019. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institution in which those deposits are held.

Restricted Cash

Restricted cash consists of cash invested in certificate of deposits used as collateral for the issuance of letters of credit pursuant to lease agreements for leasing of property at 3020 and 3030 Callan Road, San Diego, CA, which required us to execute a letter of credit for $40,000 naming the landlord as a beneficiary as of December 31, 2019. There was no restricted cash as of December 31, 2020.

Accounts Receivable

Accounts receivable are recorded at the invoiced amount and do not bear interest. As of December 31, 2019, accounts receivable represents outstanding invoices under the BARDA Agreement for work performed prior to the BARDA contract termination. There were no accounts receivable as of December 31, 2020.

Financial Instruments

Financial instruments include cash equivalents, accounts receivable, other current assets, accounts payable, accrued expenses, other liabilities and long-term debt. The carrying values of cash equivalents, accounts receivable, other current assets, accounts payable, accrued expenses, other liabilities generally approximate fair value due to the short-term nature of these instruments. Based on level 3 inputs and the borrowing rates current available for loans with similar terms, the Company believes the fair value the long-term debt approximates its carrying value.

Property and Equipment

Property and equipment are stated at cost, net of accumulated depreciation. Depreciation expense, which includes the amortization of capitalized leasehold improvements, is provided for on a straight-line basis over the estimated useful lives of the assets, or the life of the lease, whichever is shorter, and range from three to five years. When assets are sold or otherwise disposed of, the cost and related accumulated depreciation are removed from the accounts and the resulting gain or loss, if any, is included in operations. Maintenance and repairs are charged to operations as incurred.

Impairment

The Company assesses its property and equipment for potential impairment when there is a change in circumstances that indicates carrying values of assets may not be recoverable. Such long-lived assets are deemed to be impaired when the undiscounted cash flows expected to be generated by the asset (or asset group) are less than the asset’s carrying amount. Any required impairment loss would be measured as the amount by which the asset’s carrying value exceeds its fair value and would be recorded as a reduction in the carrying value of the related asset and a charge to operating expense. The Company recognized no impairment losses during any of the periods presented in these financial statements.

Goodwill

The Company’s goodwill represents the excess of the cost over the fair value of net assets acquired from its business combinations. The determination of the value of goodwill arising from business combinations requires extensive use of accounting estimates and judgments to allocate the purchase price to the fair value of the net tangible and intangible assets acquired.

Goodwill is not amortized; however, it is assessed for impairment using fair value measurement techniques on an annual basis or more frequently if facts and circumstance warrant such a review. Goodwill is considered to be impaired if the Company determines that the carrying value of the reporting unit exceeds its fair value.

The Company performs its impairment test annually during the fourth quarter by comparing the Company’s estimated fair value, calculated from the Company’s market capitalization, to its carrying amount. The Company’s annual evaluation for impairment of goodwill consists of one reporting unit. The Company completed its most recent annual evaluation for impairment as of December 31, 2020 and determined that no impairment existed.

Warrant Liability

Warrants are accounted for in accordance with the applicable authoritative accounting guidance as either liabilities or as equity instruments depending on the specific terms of the agreements. Liability-classified instruments are recorded at fair value at each reporting period with any change in fair value recognized as a component of change in fair value of warrant liabilities in the consolidated statements of operations and comprehensive loss.

Revenue Recognition

Development Revenue

The Company earns revenue for performing tasks under research and development agreements with governmental agencies like BARDA. Revenue derived from reimbursement of direct out-of-pocket expenses for research costs associated with government contracts are recorded as government contract and other within development revenue. Government contract revenue is recorded at the gross amount of the reimbursement. The costs associated with these reimbursements are reflected as a component of research and development expense in our statements of operations. The Company recognized $0.3 million and $7.0 million in BARDA revenue for the years ended December 31, 2020 and 2019, respectively.

The BARDA Agreement was terminated by the U.S. Department of Health and Human Services effective in December 2019 and the contract close out process was completed during 2020.

Concentration of Significant Customers & Geographical Sales

After the Company sold its Cell Therapy business, BARDA accounted for 100% of our revenue from continuing operations which are recognized for year ended December 31, 2020 and 2019 and accounted for 100% of total outstanding accounts receivable presented in the accompanying consolidated financial statements.

Research and Development

Research and development expenditures, which are charged to operations in the period incurred, include costs associated with the design, development, testing and enhancement of the Company’s products, regulatory fees, the purchase of laboratory supplies, and pre-clinical and clinical studies as well as salaries and benefits for our research and development employees.

Also included in research and development expenditures are costs incurred to support the government reimbursement contract, including $0.3 million and $1.5 million qualified expenses that were incurred for the years ended December 31, 2020 and 2019, related to the BARDA Agreement.

Deferred Financing Costs and Other Debt-Related Costs

Deferred financing costs are capitalized, recorded as an offset to debt balances and amortized to interest expense over the term of the associated debt instrument using the effective interest method. If the maturity of the debt is accelerated because of default or early debt repayment, then the amortization would be accelerated.

Income Taxes

Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income (loss) in the years in which those temporary differences are expected to be recovered or settled. Due to our history of losses, a full valuation allowance has been recognized against our deferred tax assets.

The Company’s policy is to recognize interest and penalties related to income tax matters in income tax expense. For the years ended December 31, 2020 and 2019, the Company has not recorded any interest or penalties related to income tax matters. The Company does not foresee any material changes to unrecognized tax benefits within the next twelve months.

Share-Based Compensation

The Company recognizes the fair value of all share-based payment awards in our statements of operations over the requisite vesting period of each award, which approximates the period during which the employee and non-employee director is required to provide service in exchange for the award. The Company estimates the fair value of these options using the Black-Scholes option pricing model using assumptions for expected volatility, expected term, and risk-free interest rate. Expected volatility is based primarily on historical volatility and is computed using daily pricing observations for recent periods that correspond to the expected term of the options. The expected term is calculated based on historical data for and applied to all employee awards as a single group as the Company does not expect (nor does historical data suggest) substantially different exercise or post-vesting termination behavior amongst our employee population. The risk-free interest rate is the interest rate for treasury instruments with maturities that approximate the expected term.

Segment Information

For the years ended December 31, 2020 and 2019, the Company is managed as a single operating segment, therefore we report our results in one operating segment.

Loss Per Share

Basic per share data is computed by dividing net income or loss applicable to common stockholders by the weighted average number of common shares outstanding during the period. Diluted per share data is computed by dividing net income or loss applicable to common stockholders by the weighted average number of common shares outstanding during the period increased to include, if dilutive, the number of additional common shares that would have been outstanding as calculated using the treasury stock method. Potential common shares were related entirely to outstanding but unexercised options, warrants and convertible preferred stocks for all periods presented.

The Company excluded all potentially dilutive securities from the calculation of diluted loss per share attributable to common stockholders for the years ended December 31, 2020 and 2019, as their inclusion would be antidilutive.

Reclassification

Certain amounts have been reclassified to conform to current year presentation.

Recently Issued and Recently Adopted Accounting Pronouncements

Recently Issued Accounting Pronouncements

In September 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. The standard amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. For available-for-sale debt securities, entities will be required to recognize an allowance for credit losses rather than a reduction in carrying value of the asset. Entities will no longer be permitted to consider the length of time that fair value has been less than amortized cost when evaluating when credit losses should be recognized. This new guidance is effective in the first quarter of 2023 for calendar-year SEC filers that are smaller reporting companies as of the one-time determination date. Early adoption is permitted beginning in 2019. The Company plans to adopt the new guidance on January 1, 2023, and it does not expect that adoption of this standard will have a material impact on its consolidated financial statements and related disclosures.

In August 2020, the FASB issued ASU No. 2020-06, Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”). ASU 2020-06 eliminates the beneficial conversion and cash conversion accounting models for convertible instruments. It also amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions. In addition, ASU 2020-06 modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted EPS computation. The amendments in ASU 2020-06 are effective for smaller reporting companies as defined by the SEC for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020. The Company is currently evaluating the impact of ASU 2020-06 on its financial statements.

Recently Adopted Accounting Pronouncements

In August 2018, the FASB issued ASU No. 2018-13 (ASU 2018-13), Changes to the Disclosure Requirements for Fair Value Measurement. This ASU eliminates, adds and modifies certain disclosure requirements for fair value measurements as part of its disclosure framework project. The standard is effective for all entities for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. The Company adopted ASU 2018-13 as of January 1, 2020, which did not have a material impact on the Company's financial statements.

Fair Value

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value

3.	Fair Value Measurements

Fair value measurements are market-based measurements, not entity-specific measurements. Therefore, fair value measurements are determined based on the assumptions that market participants would use in pricing the asset or liability. We follow a three-level hierarchy to prioritize the inputs used in the valuation techniques to derive fair values. The basis for fair value measurements for each level within the hierarchy is described below:

•

Level 1: Quoted prices in active markets for identical assets or liabilities.

•

Level 2: Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets.

•

Level 3: Valuations derived from valuation techniques in which one or more significant inputs are unobservable in active markets.

Warrants issued by the Company in connection with the 2018 Rights Offering in July 2018 (“Series T Warrants”) and in the September 2019 Offering (“Series U Warrants”) were classified as liabilities at issuance. The Series T and Series U warrants were marked to market at each subsequent reporting date through as non-operating income or loss in the statement of operations. As described in more detail in Note 12, during 2020 the Company amended the terms of 3,522,500 Series U Warrants such that those amended Series U Warrants met the requirements to be classified within stockholders’ equity and were no longer required to be re-measured at fair value at each balance sheet date.

Expected volatility was computed using daily pricing observations of traded shares of the Company for recent periods that correspond to the expected term of the warrants. The Company believes this method produces an estimate that is representative of our expectations of future volatility over the expected term of these warrants. The Company currently has no reason to believe future volatility over the expected remaining life of these warrants is likely to differ materially from historical volatility. The expected life is based on the remaining contractual term of the warrants. The risk-free interest rate is the U.S. Treasury bond rate as of the valuation date. Because some of the inputs to our valuation model are either not observable or are not derived principally from or corroborated by observable market data by correlation or other means, the warrant liability is classified as Level 3 in the fair value hierarchy. Fluctuations in the fair value of the warrants are impacted by unobservable inputs. Significant increases (decreases) in this input in isolation would result in a significantly higher (lower) fair value measurement.

The Series T Warrants are not traded in an active securities market, and as such the estimated fair value as of December 31, 2020 and 2019 was determined by using an option pricing model with the following assumptions. All outstanding Series T warrants expired unexercised in January 2021.

	As of December 31, 2020			As of December 31, 2019
Expected term	0.1 years			1.1 years
Common stock market price	$	2.02		$	2.40
Risk-free interest rate		0.08	%		1.59	%
Expected volatility		57	%		168	%
Resulting fair value (per warrant)	$	0.05		$	1.47

The Company estimated the fair value of the liability-classified Series U Warrants on the issuance date as well as at each subsequent balance sheet date with the Black Scholes model. The assumptions used in the Black Scholes option pricing model to determine the fair value of the Series U warrants were as follows:

	As of December 31, 2020			As of December 31, 2019
Expected term	3.75 years			4.75 years
Common stock market price	$	2.02		$	2.40
Risk-free interest rate		0.24	%		1.68	%
Expected volatility		149.0	%		134.5	%
Resulting fair value (per warrant)	$	1.56		$	1.94

The following table summarizes the change in our Level 3 warrant liability value (in thousands):

	Years ended December 31,
Warrant liability	2020			2019
Beginning balance	$	6,929		$	916
Issuance of warrants		—			10,214
Exercises		—			(794	)
Change in fair value of warrants		(2,418	)		(3,407	)
Reclassification to equity		(4,504	)		—
Ending balance	$	7		$	6,929

On September 30, 2020, the Company committed to issue 180,701 shares to Lincoln Park as a committee fee (“Commitment Shares”) in connection with the 2020 Purchase Agreement, and these shares were issued on October 2, 2020. The change in fair value of the Commitment Shares between September 30, 2020 and the issuance date, in the amount of $18,000 and calculated using the closing stock prices on respective dates, was recorded in change in fair value of liability-classified instruments on the statement of operations and comprehensive income/loss.

Nonfinancial Assets and Liabilities

The Company applies fair value techniques on a non-recurring basis, if and when necessary, associated with: (1) valuing potential impairment losses related to goodwill which are accounted for pursuant to the authoritative guidance for intangibles—goodwill and other; and (2) valuing potential impairment losses related to long-lived assets which are accounted for pursuant to the authoritative guidance for property, plant and equipment.

Discontinued Operations

12 Months Ended

Dec. 31, 2020

Discontinued Operations And Disposal Groups [Abstract]

Discontinued Operations

4.	Discontinued Operations

As explained in Note 1, on April 24, 2019 and April 25, 2019, the Company completed the sale of its Cell Therapy business to Lorem and Mr. Shirahama. The following table summarizes the calculation of the loss on sale of the Cell Therapy business, which was finalized during the fourth quarter of 2019 (in thousands):

Consideration received	$	7,000
Transaction costs		(1,363	)
Net cash proceeds		5,637
Less:
Carrying value of business and assets sold		12,145
Net loss on sale of business	$	(6,508	)

There were no assets or liabilities related to discontinued operations as of December 31, 2020 or 2019.

The following table summarizes the results of discontinued operations for the periods presented (in thousands).

	Year ended December 31,
	2019
Product revenue	$	901
Cost of revenue		857
Gross profit		44
Operating expenses:
Research and development		656
Sales and marketing		411
General and administrative		185
Total operating expenses		1,252
Operating loss		(1,208	)
Other income (expense)		112
Loss from discontinued operations	$	(1,096	)
Loss from sale of business		(6,508	)
Net loss from discontinued operations	$	(7,604	)

During the year ended December 31, 2019, revenue from discontinued operations were related to the Cell Therapy business. Because of the sale of the Cell Therapy business to Lorem and Mr. Shirahama, all product revenue and costs of product revenue for these periods have been recorded in loss from discontinued operations in the consolidated statements of operations.

Included in the statement of cash flows are the following non-cash adjustments related to the discontinued operations (in thousands):


	For the year ended December 31, 2019
Depreciation and amortization	$	467
Provision for excess inventory	$	—
Loss on asset disposal	$	—

Composition of Certain Financial Statement Captions

12 Months Ended

Dec. 31, 2020

Composition Of Certain Financial Statement Captions [Abstract]

Composition of Certain Financial Statement Captions

6.	Composition of Certain Financial Statement Captions

Other Current Assets

As of December 31, 2020 and 2019, other current assets were comprised of the following (in thousands):

	December 31,
	2020		2019
Prepaid services	$	131	$	277
Prepaid insurance		639		536
Other		59		144
	$	829	$	957

Property and Equipment, net

As of December 31, 2020 and 2019, property and equipment, net, were comprised of the following (in thousands):

	December 31,
	2020			2019
Office and computer equipment	$	1,525		$	1,518
Leasehold improvements		1,682			1,682
		3,207			3,200
Less accumulated depreciation		(1,387	)		(1,021	)
	$	1,820		$	2,179

Depreciation expense totaled $0.4 million and $0.9 million for the years ended December 31, 2020 and 2019, respectively.

Intangible Assets, net

As of December 31, 2020, intangible assets included the net book value of costs incurred for software upgrades.

Accounts Payable and Accrued Expenses

As of December 31, 2020 and 2019, accounts payable and accrued expenses were comprised of the following (in thousands):

	December 31,
	2020		2019
Accounts payable	$	789	$	327
Accrued payroll and bonus		738		679
Accrued professional fees		276		332
Accrued vacation and compensation		245		166
Finance lease obligation - current		10		120
Other current liabilities		23		6
Accrued expenses		—		791
Accrued R&D studies		—		858
	$	2,081	$	3,279

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7.	Commitments and Contingencies

Leases

At the inception of a contractual arrangement, the Company determines whether the contract contains a lease by assessing whether there is an identified asset and whether the contract conveys the right to control the use of the identified asset in exchange for consideration over a period of time. If both criteria are met, the Company calculates the associated lease liability and corresponding right-of-use asset upon lease commencement using a discount rate based on the rate implicit in the lease or an incremental borrowing rate commensurate with the term of the lease.

The Company records lease liabilities within current liabilities or long-term liabilities based upon the length of time associated with the lease payments. The Company records its operating lease right-of-use assets as long-term assets. Right-of-use assets for financing leases are recorded within property and equipment, net in the Balance Sheet. Leases with an initial term of 12 months or less are not recorded on the Balance Sheet. Instead, the Company recognizes lease expense for these leases on a straight-line basis over the lease term. In connection with certain operating leases, the Company has security deposits recorded and maintained as restricted cash totaling $40 thousand as of December 31, 2019. There was no security deposit as of December 31, 2020.

The Company leases laboratory, office and storage facilities in San Antonio, Texas, under operating lease agreements that expire in 2028. The Company also leases certain office space in Austin, Texas under a month-to-month operating lease agreement. In addition, the Company leases certain equipment under various operating and finance leases. The lease agreements generally provide for periodic rent increases, and renewal and termination options. The Company’s lease agreements do not contain any material variable lease payments, residual value guarantees or material restrictive covenants.

Certain leases require the Company to pay taxes, insurance, and maintenance. Payments for the transfer of goods or services such as common area maintenance and utilities represent non-lease components. The Company elected the package of practical expedients and therefore does not separate non-lease components from lease components.

The table below summarizes the Company’s lease liabilities and corresponding right-of-use assets (in thousands, except years and rates):

		2020			2019
Assets
Operating	$	636		$	781
Financing		7			134
Total leased assets	$	643		$	915

Liabilities
Current:
Operating	$	123		$	147
Financing	10			120
Noncurrent:
Operating	528			646
Financing		—		8
Total lease liabilities	$	661		$	921

Weighted-average remaining lease term (years) - operating leases	6.57			6.89
Weighted-average remaining lease term (years) - finance leases	0.42			1.08
Weighted-average discount rate - operating leases		7.79	%		7.93	%
Weighted-average discount rate - finance leases		5.00	%		5.00	%

The table below summarizes the Company’s lease costs from its consolidated statements of operations, and cash payments from its consolidated statements of cash flows.

	Year Ended December 31,
		2020		2019
Lease expense:
Operating lease expense	$	210	$	225
Finance lease expense:
Depreciation of right-of-use assets		127	116
Interest expense on lease liabilities	4		9
Total lease expense	$	341	$	350

Cash payment information:
Operating cash used for operating leases	$	204	$	213
Financing cash used for financing leases	117		131
Total cash paid for amounts included in the measurement of lease liabilities	$	321	$	344

Total rent expenses for the years ended December 31, 2020 and 2019 was $0.2 million and $0.7 million, respectively, which includes leases in the table above, month-to-month operating leases, and common area maintenance charges.

The Company’s future minimum annual lease payments under operating and financing leases at December 31, 2020 are as follows (in thousands):


	Financing Leases		Operating Leases

2021	$	10	$	183
2022		—	123
2023		—	100
2024		—	106
2025		—	108
Thereafter		—		233
Total minimum lease payments	$	10	$	853
Less: amount representing interest		—		(202	)
Present value of obligations under leases		10		651
Less: current portion	$	10	$	(123	)
Noncurrent lease obligations		—		528

Other commitments

The Company has entered into agreements with various research organizations for pre-clinical and clinical development studies, which have provisions for cancellation. Under the terms of these agreements, the vendors provide a variety of services including conducting research, recruiting and enrolling patients, monitoring studies and data analysis. Payments under these agreements typically include fees for services and reimbursement of expenses. The timing of payments due under these agreements is estimated based on current study progress. As of December 31, 2020, the Company did not have any clinical research study obligations.

The Company is subject to various claims and contingencies related to legal proceedings. Due to their nature, such legal proceedings involve inherent uncertainties including, but not limited to, court rulings, negotiations between affected parties and governmental actions. Management assesses the probability of loss for such contingencies and accrues a liability and/or discloses the relevant circumstances, as appropriate.

The Company is currently engaged in a dispute with a third party arising out of its sale of certain assets pursuant to an asset and equity purchase agreement entered into in 2019 (the "APA"). In October 2020, the Company received correspondence from such third party informing it of an alleged breach of certain representations and warranties in the APA and asserting indemnification claims. In December 2020, the Company responded to the third party and asserted that its improper use of the Company’s intellectual property constituted a breach of the APA and further asserted an indemnification claim against the third party for the Company’s losses in connection therewith. While management believe the claims asserted against the Company to be spurious and without merit, this dispute remains ongoing and there can be no assurance that it will not result in litigation. Resolution of this matter or any resulting litigation would be expensive and time-consuming and the outcome is uncertain. It is not possible to predict with certainty the outcome of these unresolved legal actions or the range of possible loss.

Term Loan Obligations

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Term Loan Obligations

8.	Term Loan Obligations

On May 29, 2015, the Company entered into the Loan and Security Agreement, pursuant to which Oxford funded an aggregate principal amount of $17.7 million (the “Term Loan”), subject to the terms and conditions set forth in the Loan and Security Agreement. The Term Loan accrues interest at a floating rate of at least 8.95% per annum, comprised of a three-month LIBOR rate with a floor of 1.00% plus 7.95%. Pursuant to the Loan and Security Agreement, as amended, the Company is required to make interest only payments through May 1, 2021 and thereafter it is required to make payments of principal and accrued interest in equal monthly installments sufficient to amortize the Term Loan through September 1, 2024, the maturity date. At maturity of the Term Loan, or earlier repayment in full following voluntary prepayment or upon acceleration, the Company is required to make a final payment in an aggregate amount equal to approximately $3.2 million. In connection with the Term Loan, on May 29, 2015, the Company issued to Oxford warrants to purchase an aggregate of 188 shares of the Company’s common stock at an exercise price of $5,175 per share. These warrants became exercisable as of November 30, 2015 and will expire on May 29, 2025 and, following the authoritative accounting guidance, are equity classified and its respective fair value was recorded as a discount to the debt.

From September 2017 to March 2019, the Company entered into a total of seven amendments to the Term Loan which, amongst other things, extended the interest only period, required repayment of $3.1 million using the proceeds received from sale of the Company’s former UK and Japan subsidiaries as described in Note 1, increased the final payment, increased the final payment fee upon maturity or early repayment of the Term Loan, and increased the minimum liquidity covenant level to $2.0 million.

On March 29, 2020, the Company entered into the Ninth Amendment of the Loan and Security Agreement (“Ninth Amendment”), pursuant to which Oxford agreed to defer the start date of principal repayment from May 1, 2020 to May 1, 2021 and extended the term of the Term loan from September 1, 2021 to September 1, 2024. In addition, pursuant to the Ninth Amendment, on April 1, 2020, the Company made a $5.0 million paydown of principal upon execution of the Ninth Amendment and $0.3 million of related final payment. After giving effect to this payment, $4.3 million of principal remains outstanding under the Loan Agreement. In addition, an amendment fee of $1.0 million will be payable in connection with the Amendment at the earlier of the maturity date, acceleration of the loans and the making of certain prepayments. All other major terms remained consistent.

Under authoritative guidance, the Ninth Amendment does not meet the criteria to be accounted for as a troubled debt restructuring. In addition, the Company performed a quantitative analysis and determined that the terms of the new debt and original debt instrument are not substantially different. Accordingly, the Ninth Amendment is accounted for as debt modification. A new effective interest rate that equates the revised cash flows to the carrying amount of the original debt is computed and applied prospectively.

The Term Loan, as amended, is collateralized by a security interest in substantially all of the Company’s existing and subsequently acquired assets, including its intellectual property assets, subject to certain exceptions set forth in the Loan and Security Agreement, as amended. The intellectual property asset collateral will be released upon the Company achieving a certain liquidity level when the total principal outstanding under the Loan and Security Agreement is less than $3 million. As of December 31, 2020, there was $4.3 million principal amount outstanding under the Term Loan, excluding the $3.2 million final payment fee, and the Company was in compliance with all of the debt covenants under the Loan and Security Agreement.

The Company’s interest expense for the years ended December 31, 2020 and 2019 was $1.1 million and $1.9 million, respectively. Interest expense is calculated using the effective interest method, therefore it is inclusive of non-cash amortization in the amount of $0.6 million and $0.5 million for the year ended December 31, 2020 and 2019, respectively, related to the amortization of the debt discount, capitalized loan costs, and accretion of final payment.

The Loan and Security Agreement, as amended, contains customary indemnification obligations and customary events of default, including, among other things, the Company’s failure to fulfill certain obligations under the Term Loan, as amended, and the occurrence of a material adverse change, which is defined as a material adverse change in the Company’s business, operations, or condition (financial or otherwise), a material impairment of the prospect of repayment of any portion of the loan. In the event of default by the Company or a declaration of material adverse change by its lender, under the Term Loan, the lender would be entitled to exercise its remedies thereunder, including the right to accelerate the debt, upon which the Company may be required to repay all amounts then outstanding under the Term Loan, which could materially harm the Company’s financial condition. As of December 31, 2020, the Company has not received any notification or indication from Oxford to invoke the material adverse change clause. However, due to the Company’s current cash flow position and the substantial doubt about its ability to continue as a going concern, the entire principal amount of the Term Loan is presented as short-term. The Company will continue to evaluate the debt classification on a quarterly basis and evaluate for reclassification in the future should its financial condition improve.

Additional details relating to the outstanding Term Loan as of December 31, 2020 and 2019 are presented in the following table (in thousands):

Year ended December 31, 2020

Origination Date

Original

Loan

Amount

Interest

Rate**

Current

Monthly

Payment***

Amended expiration date

Remaining

Principal

(Face Value)

May 2015

17,700

8.95

May 31, 2024

4,289

Year ended December 31, 2019

Origination Date

Original

Loan

Amount

Interest

Rate**

Current

Monthly

Payment*

Original

Term

Remaining

Principal

(Face Value)

May 2015

17,700

8.95

48 Months

9,288

*	Monthly payment as of December 2019, which reflects interest only

**	3 month LIBOR rate with a floor of 1% plus 7.95%

***	Monthly payment as of December 2020, which reflects interest only

As of December 31, 2020, the future contractual principal and final fee payments on all of our debt obligations are as follows (as thousands):

Years Ending December 31,
2021	$	1,016
2022		1,354
2023		1,354
2024		3,757
Total	$	7,481

Reconciliation of Face Value to Book Value as of December 31, 2019
Total debt obligations, including final payment fee (Face Value)	$	7,481
Less: Debt discount		(1,146	)
Total obligation	$	6,335

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

9.	Income Taxes

The Company has recorded a full valuation allowance against deferred tax assets and due to our net losses for the years ended December 31, 2020 and 2019, there was no provision or benefit for income taxes recorded.

The components of income/(loss) from continuing operations before income tax provision (benefit) as of December 31, 2020 and 2019 are as follows (in thousands):

	2020			2019
U.S.	$	(8,241	)	$	(3,439	)
Foreign		—			403
	$	(8,241	)	$	(3,036	)

A reconciliation of the total income tax provision tax rate to the statutory federal income tax rates of 21% for the years ended December 31, 2020 and 2019, respectively, is as follows:

	2020			2019
Income tax expense (benefit) at federal statutory rate		(21.0	)%		(21.0	)%
Change in valuation allowance		23.6	%		23.0	%
Income tax expense (benefit) at state statutory rate		(8.9	)%		(12.2	)%
Stock compensation		6.9	%		13.7	%
Mark to market adjustment		(6.1	)%		(24.0	)%
NOLs expiring and adjustments to NOL		6.0	%		19.2	%
Research credit		(1.1	)%		(1.8	)%
Return to provision		1.0	%		3.1	%
Change in state rate		(0.5	)%		(1.3	)%
Permanent interest adjustments		—			1.1	%
Other, net		0.1	%		0.2	%
		0.0	%		0.0	%

The tax effects of temporary differences that give rise to significant portions of our deferred tax assets and deferred tax liabilities as of December 31, 2020 and 2019 are as follows (in thousands):

	2020			2019
Deferred tax assets:
Allowances and reserves	$	—		$	6
Accrued expenses		128			283
Stock based compensation		168			657
Net operating loss carryforwards		95,114			92,659
Income tax credit carryforwards		8,756			8,749
Property and equipment, principally due to differences in depreciation		16			95
Intangible assets		556			370
Other, net		182			217
		104,920			103,036
Valuation allowance		(104,742	)		(102,822	)
Total deferred tax assets, net of allowance		178			214
Deferred tax liabilities:
Other		(178	)		(214	)
Total deferred tax liability		(178	)		(214	)
Net deferred tax assets (liability)	$	—		$	—

The Company has established a valuation allowance against its net deferred tax assets due to the uncertainty surrounding the realization of such assets. The Company periodically evaluates the recoverability of the deferred tax assets. At such time as it is determined that it is more likely than not that deferred assets are realizable, the valuation allowance will be reduced. The Company has recorded a full valuation allowance of $104.8 million as of December 31, 2020 as it does not believe it is more likely than not our net deferred tax assets will be realized. The Company increased its valuation allowance by approximately $1.9 million during the year ended December 31, 2020.

At December 31, 2020, we had federal, and state tax loss carry forwards of approximately $396.2 million, and $173.7 million, respectively. The federal and state net operating loss carry forwards begin to expire in 2021 and 2028, respectively, if unused. The federal net operating loss carryover includes $33.6 million of net operating losses generated in 2019. Federal net operating losses generated from 2018 onwards carryover indefinitely and may generally be used to offset up to 80% of future taxable income. At December 31, 2020, we had federal and state tax credit carry forwards of approximately $6.4 million and $5.5 million, respectively, after reduction for uncertain tax positions. The Company has not performed a formal research and development credit study with respect to these credits. The federal credits will begin to expire in 2021, if unused, and the state credits carry forward indefinitely.

Pursuant to the Internal Revenue Code (“IRC”) of 1986, as amended, specifically IRC §382 and IRC §383, The Company’s ability to use net operating loss and R&D tax credit carry forwards (“tax attribute carry forwards”) to offset future taxable income is limited if we experience a cumulative change in ownership of more than 50% within a three-year testing period. The Company has not completed an ownership change analysis pursuant to IRC Section 382 for taxable years ended after December 31, 2007. If ownership changes within the meaning of IRC Section 382 are identified as having occurred subsequent to 2007, the amount of remaining tax attribute carry forwards available to offset future taxable income and income tax expense in future years may be significantly restricted or eliminated. Further, the Company’s deferred tax assets associated with such tax attributes could be significantly reduced upon realization of an ownership change within the meaning of IRC §382.

The Company follows the provisions of income tax guidance which provides recognition criteria and a related measurement model for uncertain tax positions taken or expected to be taken in income tax returns. The guidance requires that a position taken or expected to be taken in a tax return be recognized in the financial statements when it is more likely than not that the position would be sustained upon examination by tax authorities. Tax positions that meet the more likely than not threshold are then measured using a probability weighted approach recognizing the largest amount of tax benefit that is greater than 50% likely of being realized upon ultimate settlement. The Company has not recognized any liability for uncertain tax positions as of December 31, 2020 and 2019.

Following is a tabular reconciliation of the unrecognized tax benefits activity during the years ended December 31, 2020 and 2019 (in thousands):

	2020			2019
Unrecognized Tax Benefits – Beginning	$	2,234		$	2,216
Gross decreases – tax positions in prior period		(44	)		(18	)
Gross increase – current-period tax positions		33			36
Unrecognized Tax Benefits – Ending	$	2,223		$	2,234

The unrecognized tax benefit amounts are reflected in the determination of the Company’s deferred tax assets. If recognized, none of these amounts would affect the Company’s effective tax rate, since it would be offset by an equal reduction in the deferred tax asset valuation allowance. The Company does not foresee material changes to its liability for uncertain tax benefits within the next twelve months.

The Company did not recognize interest related to unrecognized tax benefits in interest expense and penalties in operating expenses as of December 31, 2020.

The Company’s material tax jurisdictions are the United States and California. To its knowledge, the Company is currently not under examination by the Internal Revenue Service or any other taxing authority.

The Company’s tax years for 2016 (federal) and 2015 (CA) remain open to examination by the taxing authority. While not open to examination, the tax attributes generated in tax years 1998 (federal) and 1997 (CA) and forward are subject to adjustment by the taxing authorities if utilized in tax years which are still open to examination.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Stockholders' Equity

12 Months Ended

Dec. 31, 2020

Stockholders Equity Note [Abstract]

Stockholders' Equity

12. Stockholders’ Equity

Preferred Stock

The Company has authorized 5,000,000 shares of preferred stock, par value $0.001 per share. The Company’s Board of Directors is authorized to designate the terms and conditions of any preferred stock the Company issues without further action by the common stockholders. There were no shares of Series A 3.6% Convertible Preferred Stock outstanding as of December 31, 2020 and 2019. There were 1,016 and 1,021 shares of Series B Convertible Preferred Stock outstanding as of each of December 31, 2020 and December 31, 2019, respectively. There were 938 shares of Series C Preferred Stock outstanding as of December 31, 2020 and December 31, 2019.

As of December 31, 2020, there were 938 outstanding shares of Series C Preferred Stock that can be converted into an aggregate of 416,889 shares of common stock, and 1,016 shares of Series B Convertible Preferred Stock that can be converted into an aggregate of 6,096 shares of common stock. On September 25, 2019, in connection with the September 2019 Offering, the conversion price of the Series C Preferred Stock was reduced from $7.50 to $3.2132. In April 2020, in connection with the Warrant Amendments (defined below), the conversion price of the Series C Preferred Stock was reduced from $3.2132 per share to $2.25 per share.

Warrants

On April 27, 2018, the Company registered and distributed to holders of its common stock and Series B Convertible Preferred Stock, at no charge, non-transferable subscription rights to purchase up to an aggregate of 20,000 units for $1,000 a unit. Each unit consisted of one share of Series C Preferred Stock and 1,050 warrants (“Series T Warrants”). Pursuant to the rights offering the 2018 Rights Offering, the Company sold an aggregate of 6,723 units, resulting in total net proceeds to the Company of approximately $5.7 million. In April 2020, in connection with Warrant Amendments (defined below), the exercise price of the Series T Warrants was further adjusted such that every 50 warrants can be exercised into one share of common stock for $2.25.

As of December 31, 2020, there were 3,787,350 outstanding Series T Warrants which can be exercised into in aggregate 75,747 shares of common stock. All Series T Warrants expired unexercised in January 2021.

On September 25, 2019, the Company completed an underwritten public offering. The Company issued 289,000 shares of its common stock, along with pre-funded warrants to purchase 2,711,000 shares of its common stock and Series U Warrants to purchase 3,450,000 shares of its common stock at $5.00 per share. The Series U Warrants have a term of five years from the issuance date. In addition, the Company issued warrants to H.C. Wainwright & Co., LLC, as representatives of the underwriters, to purchase 75,000 shares of its common stock at $6.25 per share with a term of 5 years from the issuance date, in the form of Series U Warrants (the “Representative Warrants”).

In accordance with authoritative guidance, the pre-funded warrants are classified as equity. The Series U Warrants and the Representative Warrants are classified at issuance as liabilities due to a contingent obligation for the Company to settle the Series U Warrants with cash upon certain change in control events.

Between April and September 2020, the Company entered into revised warrant agreements with the holders of 3,447,500 Series U Warrants (“Warrant Amendments”). In return for reducing the strike price of the warrants to $2.25 per share, the warrant holders agreed to amend the settlement provisions upon a fundamental transaction such that the warrants would meet the requirements to be classified within stockholders’ equity. In September 2020, the Company entered into revised warrant agreements for the Representative Warrants that reduced the strike price of the warrants to $2.81 per share, and the warrant holders agreed to amend the settlement provisions upon a fundamental transaction such that the Representative Warrants would meet the requirements to be classified within stockholders’ equity. Accordingly, approximately $4.5 million of warrant liability was reclassified to stockholders’ equity on the respective effective date of the Warrant Amendments. In addition, approximately $0.7 million of other income representing change in the fair value of amended warrants from April 1, 2020 to the respective effective date of the Warrant Amendments is recorded in the consolidated statement of operations and comprehensive loss for the year ended December 31, 2020.

As of December 31, 2020, there were 3,037,500 outstanding Series U Warrants which can be exercised into an aggregate of 3,037,500 shares of common stock.

Common Stock

Lincoln Park Purchase Agreements

On September 21, 2018, the Company entered into a purchase agreement (the “2018 Purchase Agreement”) with Lincoln Park pursuant to which the Company had the right to sell to Lincoln Park and Lincoln Park was obligated to purchase up to $5.0 million of shares of the Company’s common stock over the 24-month period following October 15, 2018. Through December 31, 2018, the Company sold a total of 12,802 shares for proceeds of approximately $0.3 million through the 2018 Purchase Agreement. During the year ended December 31, 2019, the Company sold a total of 32,170 shares for proceeds of approximately $0.3 million. There was no amount remaining available under this financing facility as of December 31, 2020.

On September 30, 2020, the Company entered into a new purchase agreement (the “2020 Purchase Agreement”) and registration rights agreement pursuant to which Lincoln Park has committed to purchase up to $25.0 million of the Company’s common stock. Under the terms and subject to the conditions of the 2020 Purchase Agreement, the Company has the right, but not the obligation, to sell to Lincoln Park, and Lincoln Park is obligated to purchase up to $25.0 million of the Company’s common stock. Such sales of common stock by the Company, if any, will be subject to certain limitations, and may occur from time to time, at the Company’s sole discretion, over the 36-month period commencing on November 6, 2020, subject to the satisfaction of certain conditions.

The 2020 Purchase Agreement provides that the number of shares the Company may sell to Lincoln Park on any single business day in a regular purchase is 50,000, but that amount may be increased up to 100,000 shares, depending upon the market price of the Company’s common stock at the time of sale and subject to a maximum limit of $500,000 per regular purchase. The purchase price per share for each such regular purchase will be based on prevailing market prices of the Company’s common stock immediately preceding the time of sale as computed under the 2020 Purchase Agreement. In addition to regular purchases, the Company may also direct Lincoln Park to purchase other amounts as accelerated purchases or as additional accelerated purchases if the closing sale price of the common stock exceeds certain threshold prices as set forth in the 2020 Purchase Agreement. There are no trading volume requirements or restrictions under the Lincoln Park Purchase Agreement. There is no upper limit on the price per share that Lincoln Park must pay for common stock under a regular purchase or an accelerated purchase and in no event will shares be sold to Lincoln Park on a day when the Company’s common stock closing sale price is less than $0.25 per share.

On June 16, 2020, the Company received stockholder approval to permit issuances of the Company’s common stock (including the issuance of more than 19.99% of the Company’s common stock) to Lincoln Park pursuant to the 2020 Purchase Agreement. Based on the closing price of the Company’s common stock of $1.05 per share on March 16, 2020, the maximum number of shares the Company could issue and sell under the 2020 Purchase Agreement is approximately 23.8 million shares. Accordingly, the Company requested and received stockholder approval for the issuance of up to 23.8 million shares of the Company’s common stock under the 2020 Purchase Agreement. The Company would seek additional stockholder approval before issuing more than 23.8 million shares.

Lincoln Park has no right to require the Company to sell any shares of common stock to Lincoln Park, but Lincoln Park is obligated to make purchases as the Company directs, subject to certain conditions.

Actual sales of shares of common stock to Lincoln Park under the 2020 Purchase Agreement will depend on a variety of factors to be determined by the Company from time to time, including, among others, market conditions, the trading price of the common stock and determinations by the Company as to the appropriate sources of funding for the Company and its operations. During the year ended December 31, 2020, the Company issued 353,113 shares, excluding 180,701 shares issued as commitment fee, of common stock under the 2020 Purchase Agreement for total net proceeds of approximately $0.7 million. During 2021 and through the date of filing of this Form 10-K, the Company issued 985,186 shares of its common stock under the 2020 Purchase Agreement for total proceeds of $2.9 million.

The net proceeds under the 2020 Purchase Agreement to the Company will depend on the frequency and prices at which the Company sells shares of its stock to Lincoln Park. On October 2, 2020, the Company issued 180,701 shares of common stock, with the fair value of $0.5 million, to Lincoln Park as a commitment fee in connection with entering into the 2020 Purchase Agreement, which was recorded as cost of capital in stockholders’ equity.

At-the-market Issuances

On October 23, 2020, the Company entered into an Equity Distribution Agreement (the “Distribution Agreement”) with Canaccord Genuity LLC (“Canaccord”), pursuant to which the Company may issue and sell, from time to time, shares of its common stock having an aggregate offering price of up to $10,000,000 (the “ATM Shares”), depending on market demand, with Canaccord acting as an agent for sales. The Company has no obligation to sell any of the ATM Shares. The Company may instruct Canaccord not to sell the ATM Shares if the sales cannot be effected at or above the price the Company designates from time to time and the Company may at any time suspend sales pursuant to the Distribution Agreement. During the year ended December 31, 2020, the Company issued 1,616,331 shares under the Distribution Agreement for net proceeds of approximately $3.2 million. During 2021 and through the date of filing of this Form 10-K, the Company issued 536,070 shares under the Distribution Agreement for net proceeds of $1.5 million.

Stock-based Compensation

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

13.	Stock-based Compensation

On February 6, 2020, the Company amended the Company’s 2015 New Employee Incentive Plan (the “2015 Plan”) to increase the total number of shares of common stock reserved for issuance under the plan by 250,000 shares. Awards may only be granted under the 2015 Plan to employees who were not previously an employee or director of the Company, or following a bona fide period of non-employment, as a material inducement to entering into employment with the Company. As of December 31, 2020 there were 210,389 shares of common stock remaining and available for future issuances under the 2015 Plan.

On June 16, 2020, the stockholders of the Company approved the Company’s 2020 Stock Incentive Plan (“2020 Plan”), which replaced the Company’s 2014 Equity Incentive Plan. The 2020 Plan provides for the award or sale of shares of common stock (including restricted stock), the award of stock units and stock appreciation rights, and the grant of both incentive stock options to purchase common stock. The 2020 Plan provides for the issuance of up to 550,000 shares of common stock, and the number of shares available for issuance will be increased to the extent that awards granted under the 2020 Plan and the Company’s 2014 Equity Incentive Plan are forfeited or expire (except as otherwise provided in the 2020 Plan). As of December 31, 2020, there were 159,939 shares of common stock remaining and available for future issuances under the 2020 Plan.

Stock Options

Generally, options issued under the 2020 Plan are subject to a two-year or four-year vesting schedule with 25% of the options vest on one year anniversary of the grant date, and have a contractual term of 10 years.

A summary of activity for the year ended December 31, 2020 is as follows:

	Options			Weighted Average Exercise Price
Balance as of December 31, 2019		1,865		$	2,968.22
Granted		530,000		$	2.12
Cancelled/forfeited		(529	)	$	2,486.82
Balance as of December 31, 2020		531,336		$	10.01

	Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Balance as of December 31, 2020		531,336	$	10.01		9.41	$	-
Vested and expected to vest at December 31, 2020		490,008	$	10.52		9.41	$	-
Exercisable at December 31, 2020		75,028	$	56.84		9.43	$	-

The Company settles exercises of stock options with newly issued shares of its common stock. There were no stock options exercised in 2020 or 2019.

The fair value of each option awarded during the years ended December 31, 2020 and 2019 was estimated on the date of grant using the Black-Scholes-Merton option valuation model based on the following weighted-average assumptions:

	December 31, 2020			December 31, 2019
Expected term	5.8 years			7.0 years
Risk-free interest rate		0.58	%		2.41	%
Expected volatility		128.6	%		96.5	%
Dividends		0	%		0	%
Resulting fair value	$	1.87		$	0.26

The weighted average risk-free interest rate represents the interest rate for treasury constant maturity instruments published by the Federal Reserve Board. If the term of available treasury constant maturity instruments is not equal to the expected term of an employee option, we use the weighted average of the two Federal Reserve securities closest to the expected term of the employee option.

The dividend yield has been assumed to be zero as the Company (a) has never declared or paid any dividends and (b) does not currently anticipate paying any cash dividends on its outstanding shares of common stock in the foreseeable future.

The following table summarizes share-based compensation recognized during the years ended December 31, 2020 and 2019 in the statement of operations and comprehensive loss:

	Years ended December 31,
	2020		2019
Research and development	$	32	$	40
General and administrative		215		87
Total share-based compensation	$	247	$	127

As of December 31, 2020, the total compensation cost related to non-vested stock options and stock awards not yet recognized for all our plans is approximately $704,000, which is expected to be recognized as a result of vesting under service conditions over a weighted average period of 2.81 years.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2020
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions affecting the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the reporting period. The most significant estimates and critical accounting policies involve reviewing assets for impairment, determining the assumptions used in measuring share-based compensation expense, valuing warrants and valuing allowances for doubtful accounts. Actual results could differ from these estimates. Management’s estimates and assumptions are reviewed regularly, and the effects of revisions are reflected in the consolidated financial statements in the periods they are determined to be necessary.
Cash and cash equivalents	Cash and cash equivalents The Company considers all highly liquid investments with maturities of three months or less at the time of purchase to be cash equivalents. Cash and cash equivalents includes cash in readily available checking and savings accounts. The Company held no investments as of December 31, 2020 and 2019. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institution in which those deposits are held.
Restricted Cash	Restricted Cash Restricted cash consists of cash invested in certificate of deposits used as collateral for the issuance of letters of credit pursuant to lease agreements for leasing of property at 3020 and 3030 Callan Road, San Diego, CA, which required us to execute a letter of credit for $40,000 naming the landlord as a beneficiary as of December 31, 2019. There was no restricted cash as of December 31, 2020.
Accounts Receivable	Accounts Receivable Accounts receivable are recorded at the invoiced amount and do not bear interest. As of December 31, 2019, accounts receivable represents outstanding invoices under the BARDA Agreement for work performed prior to the BARDA contract termination. There were no accounts receivable as of December 31, 2020.
Financial Instruments	Financial Instruments Financial instruments include cash equivalents, accounts receivable, other current assets, accounts payable, accrued expenses, other liabilities and long-term debt. The carrying values of cash equivalents, accounts receivable, other current assets, accounts payable, accrued expenses, other liabilities generally approximate fair value due to the short-term nature of these instruments. Based on level 3 inputs and the borrowing rates current available for loans with similar terms, the Company believes the fair value the long-term debt approximates its carrying value.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, net of accumulated depreciation. Depreciation expense, which includes the amortization of capitalized leasehold improvements, is provided for on a straight-line basis over the estimated useful lives of the assets, or the life of the lease, whichever is shorter, and range from three to five years. When assets are sold or otherwise disposed of, the cost and related accumulated depreciation are removed from the accounts and the resulting gain or loss, if any, is included in operations. Maintenance and repairs are charged to operations as incurred.
Impairment	Impairment The Company assesses its property and equipment for potential impairment when there is a change in circumstances that indicates carrying values of assets may not be recoverable. Such long-lived assets are deemed to be impaired when the undiscounted cash flows expected to be generated by the asset (or asset group) are less than the asset’s carrying amount. Any required impairment loss would be measured as the amount by which the asset’s carrying value exceeds its fair value and would be recorded as a reduction in the carrying value of the related asset and a charge to operating expense. The Company recognized no impairment losses during any of the periods presented in these financial statements.
Goodwill	Goodwill The Company’s goodwill represents the excess of the cost over the fair value of net assets acquired from its business combinations. The determination of the value of goodwill arising from business combinations requires extensive use of accounting estimates and judgments to allocate the purchase price to the fair value of the net tangible and intangible assets acquired. Goodwill is not amortized; however, it is assessed for impairment using fair value measurement techniques on an annual basis or more frequently if facts and circumstance warrant such a review. Goodwill is considered to be impaired if the Company determines that the carrying value of the reporting unit exceeds its fair value. The Company performs its impairment test annually during the fourth quarter by comparing the Company’s estimated fair value, calculated from the Company’s market capitalization, to its carrying amount. The Company’s annual evaluation for impairment of goodwill consists of one reporting unit. The Company completed its most recent annual evaluation for impairment as of December 31, 2020 and determined that no impairment existed.
Warrant Liability	Warrant Liability Warrants are accounted for in accordance with the applicable authoritative accounting guidance as either liabilities or as equity instruments depending on the specific terms of the agreements. Liability-classified instruments are recorded at fair value at each reporting period with any change in fair value recognized as a component of change in fair value of warrant liabilities in the consolidated statements of operations and comprehensive loss.
Revenue Recognition	Revenue Recognition Development Revenue The Company earns revenue for performing tasks under research and development agreements with governmental agencies like BARDA. Revenue derived from reimbursement of direct out-of-pocket expenses for research costs associated with government contracts are recorded as government contract and other within development revenue. Government contract revenue is recorded at the gross amount of the reimbursement. The costs associated with these reimbursements are reflected as a component of research and development expense in our statements of operations. The Company recognized $0.3 million and $7.0 million in BARDA revenue for the years ended December 31, 2020 and 2019, respectively. The BARDA Agreement was terminated by the U.S. Department of Health and Human Services effective in December 2019 and the contract close out process was completed during 2020. Concentration of Significant Customers & Geographical Sales After the Company sold its Cell Therapy business, BARDA accounted for 100% of our revenue from continuing operations which are recognized for year ended December 31, 2020 and 2019 and accounted for 100% of total outstanding accounts receivable presented in the accompanying consolidated financial statements.
Research and Development	Research and Development Research and development expenditures, which are charged to operations in the period incurred, include costs associated with the design, development, testing and enhancement of the Company’s products, regulatory fees, the purchase of laboratory supplies, and pre-clinical and clinical studies as well as salaries and benefits for our research and development employees. Also included in research and development expenditures are costs incurred to support the government reimbursement contract, including $0.3 million and $1.5 million qualified expenses that were incurred for the years ended December 31, 2020 and 2019, related to the BARDA Agreement.
Deferred Financing Costs and Other Debt-Related Costs	Deferred Financing Costs and Other Debt-Related Costs Deferred financing costs are capitalized, recorded as an offset to debt balances and amortized to interest expense over the term of the associated debt instrument using the effective interest method. If the maturity of the debt is accelerated because of default or early debt repayment, then the amortization would be accelerated.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income (loss) in the years in which those temporary differences are expected to be recovered or settled. Due to our history of losses, a full valuation allowance has been recognized against our deferred tax assets. The Company’s policy is to recognize interest and penalties related to income tax matters in income tax expense. For the years ended December 31, 2020 and 2019, the Company has not recorded any interest or penalties related to income tax matters. The Company does not foresee any material changes to unrecognized tax benefits within the next twelve months.
Share-Based Compensation	Share-Based Compensation The Company recognizes the fair value of all share-based payment awards in our statements of operations over the requisite vesting period of each award, which approximates the period during which the employee and non-employee director is required to provide service in exchange for the award. The Company estimates the fair value of these options using the Black-Scholes option pricing model using assumptions for expected volatility, expected term, and risk-free interest rate. Expected volatility is based primarily on historical volatility and is computed using daily pricing observations for recent periods that correspond to the expected term of the options. The expected term is calculated based on historical data for and applied to all employee awards as a single group as the Company does not expect (nor does historical data suggest) substantially different exercise or post-vesting termination behavior amongst our employee population. The risk-free interest rate is the interest rate for treasury instruments with maturities that approximate the expected term.
Segment Information	Segment Information For the years ended December 31, 2020 and 2019, the Company is managed as a single operating segment, therefore we report our results in one operating segment.
Loss Per Share	Loss Per Share Basic per share data is computed by dividing net income or loss applicable to common stockholders by the weighted average number of common shares outstanding during the period. Diluted per share data is computed by dividing net income or loss applicable to common stockholders by the weighted average number of common shares outstanding during the period increased to include, if dilutive, the number of additional common shares that would have been outstanding as calculated using the treasury stock method. Potential common shares were related entirely to outstanding but unexercised options, warrants and convertible preferred stocks for all periods presented. The Company excluded all potentially dilutive securities from the calculation of diluted loss per share attributable to common stockholders for the years ended December 31, 2020 and 2019, as their inclusion would be antidilutive.
Reclassification	Reclassification Certain amounts have been reclassified to conform to current year presentation.
Recently Issued and Recently Adopted Accounting Pronouncements	Recently Issued and Recently Adopted Accounting Pronouncements Recently Issued Accounting Pronouncements In September 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. The standard amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. For available-for-sale debt securities, entities will be required to recognize an allowance for credit losses rather than a reduction in carrying value of the asset. Entities will no longer be permitted to consider the length of time that fair value has been less than amortized cost when evaluating when credit losses should be recognized. This new guidance is effective in the first quarter of 2023 for calendar-year SEC filers that are smaller reporting companies as of the one-time determination date. Early adoption is permitted beginning in 2019. The Company plans to adopt the new guidance on January 1, 2023, and it does not expect that adoption of this standard will have a material impact on its consolidated financial statements and related disclosures. In August 2020, the FASB issued ASU No. 2020-06, Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”). ASU 2020-06 eliminates the beneficial conversion and cash conversion accounting models for convertible instruments. It also amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions. In addition, ASU 2020-06 modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted EPS computation. The amendments in ASU 2020-06 are effective for smaller reporting companies as defined by the SEC for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020. The Company is currently evaluating the impact of ASU 2020-06 on its financial statements. Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-13 (ASU 2018-13), Changes to the Disclosure Requirements for Fair Value Measurement. This ASU eliminates, adds and modifies certain disclosure requirements for fair value measurements as part of its disclosure framework project. The standard is effective for all entities for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. The Company adopted ASU 2018-13 as of January 1, 2020, which did not have a material impact on the Company's financial statements.

Fair Value (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]

Summary of Change in Level 3 Warrant Liability Value

The following table summarizes the change in our Level 3 warrant liability value (in thousands):

	Years ended December 31,
Warrant liability	2020			2019
Beginning balance	$	6,929		$	916
Issuance of warrants		—			10,214
Exercises		—			(794	)
Change in fair value of warrants		(2,418	)		(3,407	)
Reclassification to equity		(4,504	)		—
Ending balance	$	7		$	6,929

Series T Warrants [Member]

Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]

Schedule of Estimated Fair Value Determined Using Option Pricing Model Assumptions

	As of December 31, 2020			As of December 31, 2019
Expected term	0.1 years			1.1 years
Common stock market price	$	2.02		$	2.40
Risk-free interest rate		0.08	%		1.59	%
Expected volatility		57	%		168	%
Resulting fair value (per warrant)	$	0.05		$	1.47

Series U Warrants [Member]

Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]

Schedule of Estimated Fair Value Determined Using Option Pricing Model Assumptions

The assumptions used in the Black Scholes option pricing model to determine the fair value of the Series U warrants were as follows:

	As of December 31, 2020			As of December 31, 2019
Expected term	3.75 years			4.75 years
Common stock market price	$	2.02		$	2.40
Risk-free interest rate		0.24	%		1.68	%
Expected volatility		149.0	%		134.5	%
Resulting fair value (per warrant)	$	1.56		$	1.94

Discontinued Operations (Tables)

12 Months Ended

Dec. 31, 2020

Summary of Assets and Liabilities Held for Sale and Operating Results Related to Discontinued Operations

The following table summarizes the results of discontinued operations for the periods presented (in thousands).

	Year ended December 31,
	2019
Product revenue	$	901
Cost of revenue		857
Gross profit		44
Operating expenses:
Research and development		656
Sales and marketing		411
General and administrative		185
Total operating expenses		1,252
Operating loss		(1,208	)
Other income (expense)		112
Loss from discontinued operations	$	(1,096	)
Loss from sale of business		(6,508	)
Net loss from discontinued operations	$	(7,604	)

Included in the statement of cash flows are the following non-cash adjustments related to the discontinued operations (in thousands):


	For the year ended December 31, 2019
Depreciation and amortization	$	467
Provision for excess inventory	$	—
Loss on asset disposal	$	—

Discontinued Operations Disposed of By Sale [Member]

Summary of Business Consideration to Calculation of the Loss on Sale

The following table summarizes the calculation of the loss on sale of the Cell Therapy business, which was finalized during the fourth quarter of 2019 (in thousands):

Consideration received	$	7,000
Transaction costs		(1,363	)
Net cash proceeds		5,637
Less:
Carrying value of business and assets sold		12,145
Net loss on sale of business	$	(6,508	)

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

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+ Details

Composition of Certain Financial Statement Captions (Tables)

12 Months Ended

Dec. 31, 2020

Composition Of Certain Financial Statement Captions [Abstract]

Other Current Assets

As of December 31, 2020 and 2019, other current assets were comprised of the following (in thousands):

	December 31,
	2020		2019
Prepaid services	$	131	$	277
Prepaid insurance		639		536
Other		59		144
	$	829	$	957

Property and Equipment, net

As of December 31, 2020 and 2019, property and equipment, net, were comprised of the following (in thousands):

	December 31,
	2020			2019
Office and computer equipment	$	1,525		$	1,518
Leasehold improvements		1,682			1,682
		3,207			3,200
Less accumulated depreciation		(1,387	)		(1,021	)
	$	1,820		$	2,179

Accounts Payable and Accrued Expenses

As of December 31, 2020 and 2019, accounts payable and accrued expenses were comprised of the following (in thousands):

	December 31,
	2020		2019
Accounts payable	$	789	$	327
Accrued payroll and bonus		738		679
Accrued professional fees		276		332
Accrued vacation and compensation		245		166
Finance lease obligation - current		10		120
Other current liabilities		23		6
Accrued expenses		—		791
Accrued R&D studies		—		858
	$	2,081	$	3,279

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Summary of Lease Liabilities and Right-of-Use Assets

The table below summarizes the Company’s lease liabilities and corresponding right-of-use assets (in thousands, except years and rates):

		2020			2019
Assets
Operating	$	636		$	781
Financing		7			134
Total leased assets	$	643		$	915

Liabilities
Current:
Operating	$	123		$	147
Financing	10			120
Noncurrent:
Operating	528			646
Financing		—		8
Total lease liabilities	$	661		$	921

Weighted-average remaining lease term (years) - operating leases	6.57			6.89
Weighted-average remaining lease term (years) - finance leases	0.42			1.08
Weighted-average discount rate - operating leases		7.79	%		7.93	%
Weighted-average discount rate - finance leases		5.00	%		5.00	%

Summary of Lease Costs

The table below summarizes the Company’s lease costs from its consolidated statements of operations, and cash payments from its consolidated statements of cash flows.

	Year Ended December 31,
		2020		2019
Lease expense:
Operating lease expense	$	210	$	225
Finance lease expense:
Depreciation of right-of-use assets		127	116
Interest expense on lease liabilities	4		9
Total lease expense	$	341	$	350

Cash payment information:
Operating cash used for operating leases	$	204	$	213
Financing cash used for financing leases	117		131
Total cash paid for amounts included in the measurement of lease liabilities	$	321	$	344

Summary of Future Minimum Annual Lease Payments under Operating and Financing Leases

The Company’s future minimum annual lease payments under operating and financing leases at December 31, 2020 are as follows (in thousands):


	Financing Leases		Operating Leases

2021	$	10	$	183
2022		—	123
2023		—	100
2024		—	106
2025		—	108
Thereafter		—		233
Total minimum lease payments	$	10	$	853
Less: amount representing interest		—		(202	)
Present value of obligations under leases		10		651
Less: current portion	$	10	$	(123	)
Noncurrent lease obligations		—		528

Term Loan Obligations (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Term Loan Outstanding

Additional details relating to the outstanding Term Loan as of December 31, 2020 and 2019 are presented in the following table (in thousands):

Year ended December 31, 2020

Origination Date

Original

Loan

Amount

Interest

Rate**

Current

Monthly

Payment***

Amended expiration date

Remaining

Principal

(Face Value)

May 2015

17,700

8.95

May 31, 2024

4,289

Year ended December 31, 2019

Origination Date

Original

Loan

Amount

Interest

Rate**

Current

Monthly

Payment*

Original

Term

Remaining

Principal

(Face Value)

May 2015

17,700

8.95

48 Months

9,288

*	Monthly payment as of December 2019, which reflects interest only

**	3 month LIBOR rate with a floor of 1% plus 7.95%

***	Monthly payment as of December 2020, which reflects interest only

Future Payments under Obligation

As of December 31, 2020, the future contractual principal and final fee payments on all of our debt obligations are as follows (as thousands):

Years Ending December 31,
2021	$	1,016
2022		1,354
2023		1,354
2024		3,757
Total	$	7,481

Face Value to Book Value Reconciliation

Reconciliation of Face Value to Book Value as of December 31, 2019
Total debt obligations, including final payment fee (Face Value)	$	7,481
Less: Debt discount		(1,146	)
Total obligation	$	6,335

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
-Paragraph 1
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 505
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-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Components of Income/(Loss) Before Income Tax Provision (Benefit)

The components of income/(loss) from continuing operations before income tax provision (benefit) as of December 31, 2020 and 2019 are as follows (in thousands):

	2020			2019
U.S.	$	(8,241	)	$	(3,439	)
Foreign		—			403
	$	(8,241	)	$	(3,036	)

Reconciliation of Total Income Tax Provision

A reconciliation of the total income tax provision tax rate to the statutory federal income tax rates of 21% for the years ended December 31, 2020 and 2019, respectively, is as follows:

	2020			2019
Income tax expense (benefit) at federal statutory rate		(21.0	)%		(21.0	)%
Change in valuation allowance		23.6	%		23.0	%
Income tax expense (benefit) at state statutory rate		(8.9	)%		(12.2	)%
Stock compensation		6.9	%		13.7	%
Mark to market adjustment		(6.1	)%		(24.0	)%
NOLs expiring and adjustments to NOL		6.0	%		19.2	%
Research credit		(1.1	)%		(1.8	)%
Return to provision		1.0	%		3.1	%
Change in state rate		(0.5	)%		(1.3	)%
Permanent interest adjustments		—			1.1	%
Other, net		0.1	%		0.2	%
		0.0	%		0.0	%

Deferred Tax Assets and Liabilities

The tax effects of temporary differences that give rise to significant portions of our deferred tax assets and deferred tax liabilities as of December 31, 2020 and 2019 are as follows (in thousands):

	2020			2019
Deferred tax assets:
Allowances and reserves	$	—		$	6
Accrued expenses		128			283
Stock based compensation		168			657
Net operating loss carryforwards		95,114			92,659
Income tax credit carryforwards		8,756			8,749
Property and equipment, principally due to differences in depreciation		16			95
Intangible assets		556			370
Other, net		182			217
		104,920			103,036
Valuation allowance		(104,742	)		(102,822	)
Total deferred tax assets, net of allowance		178			214
Deferred tax liabilities:
Other		(178	)		(214	)
Total deferred tax liability		(178	)		(214	)
Net deferred tax assets (liability)	$	—		$	—

Unrecognized Tax Benefits Activity

Following is a tabular reconciliation of the unrecognized tax benefits activity during the years ended December 31, 2020 and 2019 (in thousands):

	2020			2019
Unrecognized Tax Benefits – Beginning	$	2,234		$	2,216
Gross decreases – tax positions in prior period		(44	)		(18	)
Gross increase – current-period tax positions		33			36
Unrecognized Tax Benefits – Ending	$	2,223		$	2,234

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Option Activity

A summary of activity for the year ended December 31, 2020 is as follows:

	Options			Weighted Average Exercise Price
Balance as of December 31, 2019		1,865		$	2,968.22
Granted		530,000		$	2.12
Cancelled/forfeited		(529	)	$	2,486.82
Balance as of December 31, 2020		531,336		$	10.01

Stock Options Vested and Expected to Vest

	Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Balance as of December 31, 2020		531,336	$	10.01		9.41	$	-
Vested and expected to vest at December 31, 2020		490,008	$	10.52		9.41	$	-
Exercisable at December 31, 2020		75,028	$	56.84		9.43	$	-

Weighted-average Assumptions

	December 31, 2020			December 31, 2019
Expected term	5.8 years			7.0 years
Risk-free interest rate		0.58	%		2.41	%
Expected volatility		128.6	%		96.5	%
Dividends		0	%		0	%
Resulting fair value	$	1.87		$	0.26

Summary of Share-Based Compensation Recognized

The following table summarizes share-based compensation recognized during the years ended December 31, 2020 and 2019 in the statement of operations and comprehensive loss:

	Years ended December 31,
	2020		2019
Research and development	$	32	$	40
General and administrative		215		87
Total share-based compensation	$	247	$	127

Organization and Operations - Additional Information (Details)										1 Months Ended	2 Months Ended	9 Months Ended	12 Months Ended
	Feb. 17, 2021 USD ($) shares	Oct. 23, 2020 USD ($) shares	Oct. 02, 2020 shares	Sep. 30, 2020 USD ($)	Jun. 16, 2020 shares	Aug. 05, 2019 $ / shares	Apr. 25, 2019 USD ($)	Apr. 24, 2019 USD ($)	Sep. 21, 2018 USD ($)	Sep. 30, 2019 $ / shares shares	Feb. 17, 2021 USD ($) shares	Sep. 30, 2020 USD ($) shares	Dec. 31, 2020 USD ($) Subsidiary $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Feb. 28, 2021 shares
Basis Of Presentation And New Accounting Standards [Line Items]
Number of wholly-owned subsidiaries \| Subsidiary													5
Proceeds from sale of business													$ 0	$ 5,637,000
Reverse stock split of common stock						0.02
Common stock, par value (in dollars per share) \| $ / shares						$ 0.001							$ 0.001	$ 0.001
Net loss													$ (8,241,000)	$ (10,887,000)
Accumulated deficit													(433,511,000)	(425,270,000)
Net cash used in operating activities													(8,434,000)	(5,906,000)
Cash and cash equivalents													$ 8,346,000	17,552,000
Substantial doubt about going concern, description													These factors raise substantial doubt about the Company’s ability to continue as a going concern
Proceeds from sale of common stock													$ 4,007,000	15,964,000
Sale of common stock, net														2,208,000
Reimbursement revenue recognized														$ 4,600,000
Option granted \| shares													530,000
Warrant exercise price (in dollars per share) \| $ / shares													$ 2.25
Maximum [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Option vesting period													4 years
Minimum [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Option vesting period													2 years
Common Class A [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares													289,000
Common Class B [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Number of securities called by warrant or right \| shares													2,711,000
Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares														184,666
Warrant exercised \| shares													487,521	65,114
Series U Warrants [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares													3,450,000
Sale of Stock, Price Per Share \| $ / shares													$ 5.00
Representative Warrants [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Number of securities called by warrant or right \| shares													75,000
Warrant exercise price (in dollars per share) \| $ / shares													$ 6.25
2020 Repurchase Agreement [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares			180,701									0	353,113
Proceeds from sale of common stock													$ 700,000
Sale of common stock, net												$ 25,000,000
Period exercisable from the date of issuance												36 months
2020 Repurchase Agreement [Member] \| Common Stock [Member] \| Maximum [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares					23,800,000
Canaccord Genuity LLC [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares													1,616,331
Proceeds from sale of common stock		$ 10,000,000											$ 3,200,000
Remaining availability under financing facility		$ 0
Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares														32,170
Proceeds from sale of common stock														$ 300,000
Remaining availability under financing facility													$ 0
Sale of common stock, net									$ 5,000,000
Period exercisable from the date of issuance									24 months
Lincoln Park Capital Fund, LLC [Member] \| 2020 Repurchase Agreement [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares													353,113
Proceeds from sale of common stock													$ 700,000
Sale of common stock, net				$ 25,000,000
Period exercisable from the date of issuance				36 months
Underwriter [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Underwritten public offering description										pursuant to which the Company sold in an underwritten public offering an aggregate of (i) 289,000 Class A Units, each consisting of one share of common stock, par value $0.001 per share, of the Company and one Series U warrant to purchase one share of common stock, and (ii) 2,711,000 Class B Units, each consisting of one pre-funded Series V warrant to purchase one share of common stock and one Series U Warrant to purchase one share of common stock at a public offering price of $5.00 per Class A Unit and $4.9999 per Class B Unit (the “September 2019 Offering”). In addition, the Company granted the Underwriters a 45-day option to purchase up to an additional 450,000 shares of the Company’s common stock and/or Series U Warrants at the public offering price, less the underwriting discounts and commissions. The Underwriters exercised their option to purchase an additional 450,000 Series U warrants. The Company also issued to the Representative warrants (in the form of the Series U warrants) to purchase 75,000 shares of common stock with an exercise price of $6.25 per share of common stock (the “Representative Warrants”).
Option vesting period										45 days
Warrant granted \| shares										450,000
Underwriter [Member] \| Maximum [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Option granted \| shares										450,000
Underwriter [Member] \| Common Class A [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock, par value (in dollars per share) \| $ / shares										$ 0.001
Common stock issued (in shares) \| shares										289,000
Underwriter [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares		1,616,299
Proceeds from sale of common stock		$ 3,200,000
Underwriter [Member] \| Series V Warrants \| Common Class B [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Number of securities called by warrant or right \| shares										2,711,000
Underwriter [Member] \| Series U Warrants [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Warrant exercised \| shares										450,000
Underwriter [Member] \| Series U Warrants [Member] \| Common Class A [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Sale of Stock, Price Per Share \| $ / shares										$ 5.00
Underwriter [Member] \| Series U Warrants [Member] \| Common Class B [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Sale of Stock, Price Per Share \| $ / shares										$ 4.9999
Underwriter [Member] \| Representative Warrants [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Number of securities called by warrant or right \| shares										75,000
Warrant exercise price (in dollars per share) \| $ / shares										$ 6.25
Subsequent Event [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Number of securities called by warrant or right \| shares															896,500
Subsequent Event [Member] \| 2020 Repurchase Agreement [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares	985,186
Proceeds from sale of common stock	$ 2,900,000
Subsequent Event [Member] \| Canaccord Genuity LLC [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares	536,070
Proceeds from sale of common stock	$ 1,500,000
Subsequent Event [Member] \| Lincoln Park Capital Fund, LLC [Member] \| 2020 Repurchase Agreement [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares											985,186
Proceeds from sale of common stock											$ 2,900,000
Subsequent Event [Member] \| Underwriter [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares) \| shares											536,070
Proceeds from sale of common stock											$ 1,500,000
Sale of UK Subsidiary and Certain Assets [Member] \| Loan and Security Agreement [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of business								$ 4,000,000
Payments for principal, interest and fees								1,700,000
Sale of the Japanese Subsidiary and Certain Assets [Member] \| Loan and Security Agreement [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of business							$ 3,000,000
Payments for principal, interest and fees							1,400,000
UK Subsidiary and Cell Therapy Assets [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of business								3,300,000
UK Subsidiary and Cell Therapy Assets [Member] \| Amendmend to Loan and Security Agreement [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Payments for principal, interest and fees								$ 1,700,000
Japanese Subsidiary and Cell Therapy Assets [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of business							2,400,000
Japanese Subsidiary and Cell Therapy Assets [Member] \| Amendmend to Loan and Security Agreement [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Payments for principal, interest and fees							$ 1,400,000

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) ReportableUnit Segment	Dec. 31, 2019 USD ($) Segment
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents investments with original maturities	$ 0	$ 0
Restricted cash	0	40,000
Accounts receivable	0	1,169,000
Impairment loss	0	0
Impairment charges	$ 0
Number of reporting units \| ReportableUnit	1
Qualifying expenditures related to research	$ 300,000	1,500,000
Interest or penalties related to income tax matters	$ 0	$ 0
Number of operating segment \| Segment	1	1
BARDA Contract [Member] \| Development [Member]
Summary Of Significant Accounting Policies [Line Items]
Revenue recognized	$ 300,000	$ 7,000,000
Customer Concentration Risk [Member] \| Revenue Recognized [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	100.00%
Customer Concentration Risk [Member] \| Accounts Receivable [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	100.00%	100.00%
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	5 years
Letter of Credit [Member]
Summary Of Significant Accounting Policies [Line Items]
Letters of credit amount pursuant to lease agreement		$ 40,000

Discontinued Operations - Summary of Operating Results Related to Discontinued Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Discontinued Operations And Disposal Groups [Abstract]
Product revenue		$ 901
Cost of revenue		857
Gross profit		44
Operating expenses:
Research and development		656
Sales and marketing		411
General and administrative		185
Total operating expenses		1,252
Operating loss		(1,208)
Other income (expense)		112
Loss from discontinued operations		(1,096)
Loss from sale of business		(6,508)
Net loss from discontinued operations	$ 0	$ (7,604)

Composition of Certain Financial Statement Captions - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts Payable and Accrued Expenses [Abstract]
Accounts payable	$ 789	$ 327
Accrued payroll and bonus	738	679
Accrued professional fees	276	332
Accrued vacation and compensation	245	166
Finance lease obligation - current	10	120
Other current liabilities	23	6
Accrued expenses		791
Accrued R&D studies		858
Accounts payable and accrued expenses, Total	$ 2,081	$ 3,279

Commitments and Contingencies - Summary of Lease Liabilities and Right-of-Use Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets
Operating	$ 636	$ 781
Financing	7	134
Total leased assets	643	915
Liabilities
Operating lease liabilities, current	123	147
Financing lease liabilities, current	10	120
Operating lease liabilities. noncurrent	528	646
Financing lease liabilities, noncurrent		8
Total lease liabilities	$ 661	$ 921
Weighted-average remaining lease term (years) - operating leases	6 years 6 months 25 days	6 years 10 months 20 days
Weighted-average remaining lease term (years) - finance leases	5 months 1 day	1 year 29 days
Weighted-average discount rate - operating leases	7.79%	7.93%
Weighted-average discount rate - finance leases	5.00%	5.00%

Commitments and Contingencies - Summary of Future Minimum Annual Lease Payments under Operating and Financing Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Leases
2021	$ 10
2022
2023
2024
2025
Thereafter
Total minimum lease payments	10
Less: amount representing interest
Present value of obligations under leases	10
Finance lease obligation - current	10	$ 120
Financing lease liabilities, noncurrent		8
Operating Leases
2021	183
2022	123
2023	100
2024	106
2025	108
Thereafter	233
Total minimum lease payments	853
Less: amount representing interest	(202)
Present value of obligations under leases	651
Less: current portion	(123)	(147)
Noncurrent operating lease liability	$ 528	$ 646

Term Loan Obligations (Details) - USD ($)				12 Months Ended
Term Loan Obligations (Details) - USD ($)	Mar. 29, 2020	Mar. 28, 2020	May 29, 2015	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Warrant exercise price (in dollars per share)				$ 2.25
Interest expense				$ 1,107,000	$ 1,855,000
Non-cash amortization				$ 600,000	$ 500,000
LIBOR [Member] \| Interest Rate Floor [Member]
Debt Instrument [Line Items]
Basis variable rate			1.00%
Term Loan [Member]
Debt Instrument [Line Items]
Origination Date				May 29, 2015	May 29, 2015
Original Loan Amount			$ 17,700,000	$ 17,700,000	$ 17,700,000
Basis variable rate			7.95%
Maturity date	Sep. 01, 2024	Sep. 01, 2021	May 01, 2021
Fees amount associated with loan			$ 3,200,000	$ 3,200,000
Number of securities called by warrant or right			188
Warrant exercise price (in dollars per share)			$ 5,175
Date from which warrants are exercisable					Nov. 30, 2015
Warrant expiration date					May 29, 2025
Minimum liquidity covenant					$ 2,000,000
Debt principal repayment start date	May 01, 2021	May 01, 2020
Prepayments of term loan	$ 5,000,000
Related final payment	300,000
Term loan, remaining amount	4,300,000
Amendment fee	$ 1,000,000
Debt Instrument, Covenant Compliance				the Company was in compliance with all of the debt covenants under the Loan and Security Agreement.
Term Loan [Member] \| Loan and Security Agreement [Member] \| Sale of the Japanese Subsidiary and Certain Assets [Member]
Debt Instrument [Line Items]
Payments for principal, interest and fees			$ 3,100,000
Minimum [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Interest rate			8.95%
Maximum [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Original Loan Amount				$ 3,000,000
Long Term Debt Outstanding Threshold Amount				$ 4,300,000

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Provision or benefit for income taxes	$ 0	$ 0
Income Tax Contingency [Abstract]
Valuation allowance	104,800,000
Increase (decrease) in valuation allowance	$ 1,900,000
Net operating loss carryforwards, Expire date	begin to expire in 2021 and 2028
State tax credit carryforwards	$ 5,500,000
Cumulative change in ownership	50.00%
Period of net operating loss and R&D tax credit carry forwards to offset future taxable income	3 years
Liability for uncertain tax positions	$ 0	$ 0
Period for material changes of liability for uncertain tax benefits	12 months
Interest related to unrecognized tax benefits in interest expense and penalties	$ 0
Federal [Member]
Income Tax Contingency [Abstract]
Tax loss carryforwards	396,200,000
Federal tax carry forward	$ 6,400,000
Federal tax credit carryforward, Expiration date	begin to expire in 2021
Net operating losses	$ 33,600,000
Federal [Member] \| Maximum [Member]
Income Tax Contingency [Abstract]
Percentage of federal net operating losses used to offset of future taxable income	80.00%
State [Member]
Income Tax Contingency [Abstract]
Tax loss carryforwards	$ 173,700,000

Income Taxes - Reconciliation of Total Income Tax Provision (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of the total income tax provision tax rate [Abstract]
Income tax expense (benefit) at federal statutory rate	(21.00%)	(21.00%)
Change in valuation allowance	23.60%	23.00%
Income tax expense (benefit) at state statutory rate	(8.90%)	(12.20%)
Stock compensation	6.90%	13.70%
Mark to market adjustment	(6.10%)	(24.00%)
NOLs expiring and adjustments to NOL	6.00%	19.20%
Research credit	(1.10%)	(1.80%)
Return to provision	1.00%	3.10%
Change in state rate	(0.50%)	(1.30%)
Permanent interest adjustments		1.10%
Other, net	0.10%	0.20%
Total income tax provision	0.00%	0.00%

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets [Abstract]
Allowances and reserves		$ 6
Accrued expenses	$ 128	283
Stock based compensation	168	657
Net operating loss carryforwards	95,114	92,659
Income tax credit carryforwards	8,756	8,749
Property and equipment, principally due to differences in depreciation	16	95
Intangible assets	556	370
Other, net	182	217
Deferred tax assets (Total)	104,920	103,036
Valuation allowance	(104,742)	(102,822)
Total deferred tax assets, net of allowance	178	214
Deferred tax liabilities [Abstract]
Other	(178)	(214)
Total deferred tax liability	(178)	(214)
Net deferred tax assets (liability)	$ 0	$ 0

Stockholders' Equity - Warrants (Details) - USD ($)			12 Months Ended
Stockholders' Equity - Warrants (Details) - USD ($)	Jul. 25, 2018	Jul. 17, 2018	Dec. 31, 2020	Dec. 31, 2019	Apr. 30, 2020
Preferred Stock [Abstract]
Warrant exercise price (in dollars per share)			$ 2.25
Warrant liability			$ 7,000	$ 6,929,000
Change in fair value of warrants			(2,400,000)	$ (3,407,000)
Outstanding Warrants [Member]
Preferred Stock [Abstract]
Warrant liability			4,500,000
Change in fair value of warrants			$ 700,000
Series U Warrants [Member]
Preferred Stock [Abstract]
Common stock issued (in shares)			3,450,000
Sale of Stock, Price Per Share			$ 5.00
Warrants expected term			5 years
Representative Warrants [Member]
Preferred Stock [Abstract]
Number of securities called by warrant or right			75,000
Warrant exercise price (in dollars per share)			$ 6.25
Warrant exercise price decrease			$ 2.81
Common Stock [Member]
Preferred Stock [Abstract]
Common stock issued (in shares)				184,666
Warrants expected term			5 years
Series C Convertible Preferred Stock [Member]
Preferred Stock [Abstract]
Warrant exercise price (in dollars per share)					$ 2.25
Common Class A [Member]
Preferred Stock [Abstract]
Common stock issued (in shares)			289,000
Common Class B [Member]
Preferred Stock [Abstract]
Number of securities called by warrant or right			2,711,000
2018 Rights Offering [Member]
Preferred Stock [Abstract]
Number of securities called by warrant or right		1
Common stock issued (in shares)	6,723
Gross proceeds from private placement of stock	$ 5,700,000
2018 Rights Offering [Member] \| Outstanding Warrants [Member]
Preferred Stock [Abstract]
Number of securities called by warrant or right		1,050
2018 Rights Offering [Member] \| Common Stock and Series B Convertible Preferred Stock [Member]
Preferred Stock [Abstract]
Charge on Non Transferable Subscription Rights		$ 0
2018 Rights Offering [Member] \| Series C Convertible Preferred Stock [Member]
Preferred Stock [Abstract]
Number of securities called by warrant or right		20,000
2018 Rights Offering [Member] \| Series C Convertible Preferred Stock [Member] \| Outstanding Warrants [Member]
Preferred Stock [Abstract]
Warrant exercise price (in dollars per share)		$ 1,000
2018 Rights Offering [Member] \| Common Stock [Member]
Preferred Stock [Abstract]
Number of securities called by warrant or right					1
2018 Rights Offering [Member] \| Common Stock [Member] \| Outstanding Warrants [Member]
Preferred Stock [Abstract]
Number of securities called by warrant or right					50
Series T Warrants [Member] \| 2018 Rights Offering [Member] \| Outstanding Warrants [Member]
Preferred Stock [Abstract]
Class of warrant outstanding			3,787,350
Number of warrants exercised			75,747
Series U Warrants [Member] \| Outstanding Warrants [Member]
Preferred Stock [Abstract]
Number of securities called by warrant or right			3,447,500
Class of warrant outstanding			3,037,500
Number of warrants exercised			3,037,500

Stockholders' Equity - Common Stock (Details) - USD ($)							2 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
Stockholders' Equity - Common Stock (Details) - USD ($)	Feb. 17, 2021	Oct. 23, 2020	Oct. 02, 2020	Sep. 30, 2020	Jun. 16, 2020	Sep. 21, 2018	Feb. 17, 2021	Dec. 31, 2018	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Mar. 16, 2020
Common Stock [Abstract]
Common stock issued, value											$ 2,208,000
Proceeds from sale of common stock										$ 4,007,000	15,964,000
Sale/Issuance of common stock											$ 2,208,000
Common Stock [Member]
Common Stock [Abstract]
Common stock issued (in shares)											184,666
Common Stock [Member] \| Lincoln Park Capital Fund, LLC [Member]
Common Stock [Abstract]
Common stock issued, value						$ 5,000,000
Period exercisable from the date of issuance						24 months
Common stock issued (in shares)											32,170
Proceeds from sale of common stock											$ 300,000
Remaining availability under financing facility										$ 0
Sale/Issuance of common stock						$ 5,000,000
Common Stock [Member] \| Canaccord Genuity LLC [Member]
Common Stock [Abstract]
Common stock issued (in shares)										1,616,331
Proceeds from sale of common stock		$ 10,000,000								$ 3,200,000
Remaining availability under financing facility		0
Common Stock [Member] \| Canaccord Genuity LLC [Member] \| Subsequent Event [Member]
Common Stock [Abstract]
Common stock issued (in shares)	536,070
Proceeds from sale of common stock	$ 1,500,000
Common Stock [Member] \| Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member]
Common Stock [Abstract]
Common stock issued (in shares)								12,802
Proceeds from sale of common stock								$ 300,000
Common Stock [Member] \| 2020 Repurchase Agreement [Member]
Common Stock [Abstract]
Common stock issued, value									$ 25,000,000
Period exercisable from the date of issuance									36 months
Common stock issued (in shares)			180,701						0	353,113
Proceeds from sale of common stock										$ 700,000
Sale/Issuance of common stock									$ 25,000,000
Closing price per share												$ 1.05
Fair value of commitment fee			$ 500,000
Common Stock [Member] \| 2020 Repurchase Agreement [Member] \| Subsequent Event [Member]
Common Stock [Abstract]
Common stock issued (in shares)	985,186
Proceeds from sale of common stock	$ 2,900,000
Common Stock [Member] \| 2020 Repurchase Agreement [Member] \| Commitment Fee
Common Stock [Abstract]
Common stock issued (in shares)										180,701
Common Stock [Member] \| 2020 Repurchase Agreement [Member] \| Minimum [Member] \| Single Regular Purchase [Member]
Common Stock [Abstract]
Common stock issued, value				$ 500,000
Common stock issued (in shares)				50,000
Sale/Issuance of common stock				$ 500,000
Common Stock [Member] \| 2020 Repurchase Agreement [Member] \| Maximum [Member]
Common Stock [Abstract]
Common stock issued (in shares)					23,800,000
Percentage issuance of common stock					19.99%
Common Stock [Member] \| 2020 Repurchase Agreement [Member] \| Maximum [Member] \| Single Regular Purchase [Member]
Common Stock [Abstract]
Common stock issued (in shares)				100,000
Closing price per share				$ 0.25					$ 0.25
Common Stock [Member] \| 2020 Repurchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member]
Common Stock [Abstract]
Common stock issued, value				$ 25,000,000
Period exercisable from the date of issuance				36 months
Common stock issued (in shares)										353,113
Proceeds from sale of common stock										$ 700,000
Sale/Issuance of common stock				$ 25,000,000
Common Stock [Member] \| 2020 Repurchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Subsequent Event [Member]
Common Stock [Abstract]
Common stock issued (in shares)							985,186
Proceeds from sale of common stock							$ 2,900,000
Common Stock [Member] \| Sales Agreement [Member] \| Canaccord Genuity LLC [Member] \| At The Market Offering Program [Member]
Common Stock [Abstract]
Remaining availability under financing facility		0
Common Stock [Member] \| Sales Agreement [Member] \| Canaccord Genuity LLC [Member] \| Maximum [Member] \| At The Market Offering Program [Member]
Common Stock [Abstract]
Proceeds from sale of common stock		$ 10,000,000

Stock-based Compensation - Additional Information (Details) - USD ($)		12 Months Ended
	Jun. 16, 2020	Dec. 31, 2020	Dec. 31, 2019	Feb. 06, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares to be issued (in shares)		530,000
Stock Option Activity [Abstract]
Stock option vesting percentage		25.00%
Stock option contractual term		10 years
Weighted Average Remaining Contractual Terms [Abstract]
Stock options exercised		$ 0	$ 0
Dividend yield assumed		0
Total unamortized compensation cost related to outstanding unvested stock options and restricted stock awards		$ 704,000
Weighted average period for recognition of cost		2 years 9 months 21 days
Minimum [Member]
Stock Option Activity [Abstract]
Stock option vesting period		2 years
Maximum [Member]
Stock Option Activity [Abstract]
Stock option vesting period		4 years
2015 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increased in the total number of shares of common stock reserved for issuance				250,000
Securities remaining and available for future issuances (in shares)		210,389
2020 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Securities remaining and available for future issuances (in shares)		159,939
Common stock shares to be issued (in shares)	550,000

Stock-based Compensation - Stock Options Vested and Expected to Vest (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Options [Roll Forward]
Balance as of December 31, 2020	531,336	1,865
Vested and expected to vest at December 31, 2020	490,008
Exercisable at December 31, 2020	75,028
Weighted Average Exercise Price [Roll Forward]
Balance as of December 31, 2020 (in dollars per share)	$ 10.01
Vested and expected to vest at December 31, 2020	10.52
Exercisable at December 31, 2020	$ 56.84
Weighted Average Remaining Contractual Term [Roll Forward]
Balance as of December 31, 2020	9 years 4 months 28 days
Vested and expected to vest at December 31, 2020	9 years 4 months 28 days
Exercisable at December 31, 2020	9 years 5 months 4 days

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement Of Stockholders Equity [Abstract]
Sale of stock for common stock and pre funded warrants, offering costs		$ 0.6
Offering costs,net	$ 0.6

Loss per Share - Schedule of Antidilutive Securities Excluded from Diluted Income (Loss) per Share (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive common shares excluded from the calculations of diluted loss per share (in shares)	4,067,946	3,936,865
Outstanding Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive common shares excluded from the calculations of diluted loss per share (in shares)	531,336	1,865
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive common shares excluded from the calculations of diluted loss per share (in shares)	422,985	298,000
Outstanding Warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive common shares excluded from the calculations of diluted loss per share (in shares)	3,113,625	3,637,000

Loss per Share (Details) - Series C Convertible Preferred Stock [Member] - USD ($)	1 Months Ended		12 Months Ended
	Apr. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Preferred stock conversion price (in dollars per share)	$ 3.2132	$ 3.2132	$ 39.93
Preferred stock conversion price reduced (in dollars per share)	$ 2.25	$ 7.50	$ 7.50
Dividend Paid [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dividends payable			$ 554,000

Commitments and Contingencies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Recorded Unconditional Purchase Obligation [Line Items]
Restricted cash	$ 0	$ 40,000
Security deposit	0
Contractual obligation	7,481,000
Operating Lease Obligations [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Rent expense	200,000	$ 700,000
Pre-clinical Research Study Obligations [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Contractual obligation	$ 0
San Antonio, Texas [Member] \| Office Laboratory and Storage Space [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Operating leases expiry year	2028

NanoTx License Agreement - Additional Information (Details) - USD ($)	May 07, 2020	Dec. 31, 2020	Dec. 31, 2019
Common stock, shares issued (in shares)		6,749,028	3,880,588
Common stock, $0.001 par value; 100,000,000 shares authorized; 6,749,028 and 3,880,588 shares issued and outstanding in 2020 and 2019, respectively		$ 7,000	$ 4,000
Nano Tx Licenses Agreement [Member]
License fee payment in cash	$ 400,000
Common stock, shares issued (in shares)	230,769
Common stock, $0.001 par value; 100,000,000 shares authorized; 6,749,028 and 3,880,588 shares issued and outstanding in 2020 and 2019, respectively	$ 781,000
Nano Tx Licenses Agreement [Member] \| Development And Sales Milestone [Member]
Milestone payments	$ 136,500,000

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Stockholders’ equity:
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	1,954	1,959
Preferred stock, shares outstanding (in shares)	1,954	1,959
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	6,749,028	3,880,588
Common stock, shares outstanding (in shares)	6,749,028	3,880,588

Fair Value - Summary of Change in Level 3 Warrant Liability Value (Details) - Warrant Liability [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Warrant liability
Beginning balance	$ 6,929	$ 916
Issuance of warrants		10,214
Exercises		(794)
Change in fair value of warrants	(2,418)	(3,407)
Reclassification to equity	(4,504)
Ending balance	$ 7	$ 6,929

Discontinued Operations - Summary of Business Consideration to Calculation of the Loss on Sale (Details) - USD ($) $ in Thousands		12 Months Ended
	Apr. 25, 2019	Dec. 31, 2020	Dec. 31, 2019
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net cash proceeds		$ 0	$ 5,637
Net loss on sale of business			$ (6,508)
Discontinued Operations Disposed of By Sale [Member] \| Cell Therapy Business [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Consideration received	$ 7,000
Transaction costs	(1,363)
Net cash proceeds	5,637
Carrying value of business and assets sold	12,145
Net loss on sale of business	$ (6,508)

Discontinued Operations - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Discontinued Operations And Disposal Groups [Abstract]
Assets Related to Discontinued Operation	$ 0	$ 0
Liabilities Related to Discontinued Operation	$ 0	$ 0

Discontinued Operations - Summary of Non-Cash Adjustments Related to Discontinued Operations (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Noncash Investing and Financing Items [Abstract]
Depreciation and amortization	$ 467
Loss on asset disposal	$ (6,508)

Composition of Certain Financial Statement Captions - Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Other Current Assets [Abstract]
Prepaid services	$ 131	$ 277
Prepaid insurance	639	536
Other	59	144
Total other current assets	$ 829	$ 957

Composition of Certain Financial Statement Captions - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property and Equipment, net [Abstract]
Office and computer equipment	$ 1,525	$ 1,518
Leasehold improvements	1,682	1,682
Property and equipment, gross	3,207	3,200
Less accumulated depreciation	(1,387)	(1,021)
Property and equipment, net	$ 1,820	$ 2,179

Commitments and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease expense:
Operating lease expense	$ 210	$ 225
Finance lease expense:
Depreciation of right-of-use assets	127	116
Interest expense on lease liabilities	4	9
Total lease expense	341	350
Cash payment information:
Operating cash used for operating leases	204	213
Financing cash used for financing leases	117	131
Total cash paid for amounts included in the measurement of lease liabilities	$ 321	$ 344

Term Loan Obligations - Future Payments under Obligation (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Future contractual principal and final fee payments on all debt [Abstract]
2021	$ 1,016
2022	1,354
2023	1,354
2024	3,757
Total	$ 7,481

Term Loan Obligations - Face Value to Book Value Reconciliation (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Reconciliation of Face Value to Book Value [Abstract]
Total debt obligations, including final payment fee (Face Value)	$ 7,481
Less: Debt discount	(1,146)
Total obligation	$ 6,335

Income Taxes - Unrecognized Tax Benefits Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Schedule of reconciliation of unrecognized tax benefits activity [Roll Forward]
Unrecognized Tax Benefits – Beginning	$ 2,234	$ 2,216
Gross decreases – tax positions in prior period	(44)	(18)
Gross increase – current-period tax positions	33	36
Unrecognized Tax Benefits – Ending	$ 2,223	$ 2,234

Employee Benefit Plan (Details) - USD ($)	12 Months Ended
Employee Benefit Plan (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Discretionary or matching contributions	$ 0	$ 0

Stock-based Compensation - Stock Option Activity (Details)	12 Months Ended
	Dec. 31, 2020 $ / shares shares
Options [Roll Forward]
Balance as of December 31, 2019 (in shares) \| shares	1,865
Granted (in shares) \| shares	530,000
Cancelled/forfeited (in shares) \| shares	(529)
Balance as of December 31, 2020 (in shares) \| shares	531,336
Weighted Average Exercise Price [Roll Forward]
Balance as of December 31, 2019 (in dollars per share) \| $ / shares	$ 2,968.22
Granted (in dollars per share) \| $ / shares	2.12
Cancelled/forfeited (in dollars per share) \| $ / shares	2,486.82
Balance as of December 31, 2020 (in dollars per share) \| $ / shares	$ 10.01

Stock-based Compensation - Weighted-average Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Black-Scholes-Merton option valuation model based on weighted-average assumptions [Abstract]
Expected term	5 years 9 months 18 days	7 years
Risk-free interest rate	0.58%	2.41%
Expected volatility	128.60%	96.50%
Dividends	0.00%	0.00%
Resulting fair value	$ 1.87	$ 0.26

Subsequent Events - Additional Information (Details) - USD ($)					1 Months Ended	9 Months Ended	12 Months Ended
	Feb. 17, 2021	Jan. 08, 2021	Oct. 23, 2020	Oct. 02, 2020	Feb. 28, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Proceeds from sale of common stock							$ 4,007,000	$ 15,964,000
Common Stock [Member]
Subsequent Event [Line Items]
Common stock issued (in shares)								184,666
Common Stock [Member] \| 2020 Repurchase Agreement [Member]
Subsequent Event [Line Items]
Common stock issued (in shares)				180,701		0	353,113
Proceeds from sale of common stock							$ 700,000
Common Stock [Member] \| Canaccord Genuity LLC [Member]
Subsequent Event [Line Items]
Common stock issued (in shares)							1,616,331
Proceeds from sale of common stock			$ 10,000,000				$ 3,200,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of securities called by warrant or right					896,500
Proceeds from warrant exercises					$ 2,000,000
Subsequent Event [Member] \| Common Stock [Member] \| 2020 Repurchase Agreement [Member]
Subsequent Event [Line Items]
Common stock issued (in shares)	985,186
Proceeds from sale of common stock	$ 2,900,000
Subsequent Event [Member] \| Common Stock [Member] \| Canaccord Genuity LLC [Member]
Subsequent Event [Line Items]
Common stock issued (in shares)	536,070
Proceeds from sale of common stock	$ 1,500,000
Piramal Pharma Solutions, Inc. [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Master service agreement date		Jan. 08, 2021
Master services agreement initial term		5 years
Master services agreement terms, Description		The MSA has a term of five years and will automatically renew for successive one-year terms unless either party notifies the other no later than six months prior to the original term or any additional terms of its intention to not renew the MSA. The Company has the right to terminate the MSA for convenience upon thirty days’ prior written notice.