0001564590-22-006708 | 10-K | XBRL Viewer

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CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 18,400	$ 8,346
Other current assets	1,324	829
Total current assets	19,724	9,175
Property and equipment, net	1,477	1,820
Operating lease right-use-of assets	341	636
Goodwill	372	372
Intangible assets, net	51	86
Other assets	16	16
Total assets	21,981	12,105
Current liabilities:
Accounts payable and accrued expenses	4,151	2,081
Operating lease liability	111	123
Term loan obligation, current	1,608	6,335
Total current liabilities	5,870	8,539
Noncurrent operating lease liability	269	528
Term loan obligation	5,005
Warrant liability	1	7
Total liabilities	11,145	9,074
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 1,952 and 1,954 shares issued and outstanding in 2021 and 2020, respectively
Common stock, $0.001 par value; 100,000,000 shares authorized; 15,510,025 and 6,749,028 shares issued and outstanding in 2021 and 2020, respectively	16	7
Additional paid-in capital	457,730	436,535
Accumulated deficit	(446,910)	(433,511)
Total stockholders’ equity	10,836	3,031
Total liabilities and stockholders’ equity	$ 21,981	$ 12,105

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
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)	1,952	1,954
Preferred stock, shares outstanding (in shares)	1,952	1,954
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)	15,510,025	6,749,028
Common stock, shares outstanding (in shares)	15,510,025	6,749,028

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Development revenue:
Government contracts and other		$ 303
Total development revenues		303
Operating expenses:
Research and development	$ 5,323	2,700
In process research and development acquired	250	781
General and administrative	6,853	6,406
Loss on disposal of property and equipment	66	0
Total operating expenses	12,492	9,887
Operating loss	(12,492)	(9,584)
Other income (expense):
Interest income	19	50
Interest expense	(932)	(1,107)
Change in fair value of liability instruments	6	2,400
Total other expense	(907)	1,343
Net loss	$ (13,399)	$ (8,241)
Net loss per share, basic and diluted	$ (1.11)	$ (1.86)
Basic and diluted weighted average shares used in calculating net loss per share attributable to common stockholders	12,089,186	4,427,835

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2019	$ 1,160		$ 4	$ 426,426	$ (425,270)
Balance (in shares) at Dec. 31, 2019		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
Issuance of common stock for exercise of warrants	1,098		$ 1	1,097
Issuance of common stock for exercise of warrants (in shares)			487,521
Reclassification of warrant liabilities	4,504			4,504
Issuance of common stock for in process research and development acquired from NanoTx Therapeutics	381			381
Issuance of common stock for in process research and development acquired (in share)			230,769
Conversion of convertible preferred stock into common stock (share)		(5)	37
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		1,954	6,749,028
Share-based compensation	606			606
Issuance of common stock, net of offering costs	18,581		$ 8	18,573
Issuance of common stock, net of offering costs (share)			7,864,379
Issuance of common stock for exercise of warrants	2,017		$ 1	2,016
Issuance of common stock for exercise of warrants (in shares)			896,500
Conversion of convertible preferred stock into common stock (share)		(2)	118
Net loss	(13,399)				(13,399)
Balance at Dec. 31, 2021	$ 10,836		$ 16	$ 457,730	$ (446,910)
Balance (in shares) at Dec. 31, 2021		1,952	15,510,025

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Statement Of Stockholders Equity [Abstract]
Offering costs,net	$ 0.3	$ 0.6

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows used in operating activities:
Net loss	$ (13,399)	$ (8,241)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	395	366
Amortization of deferred financing costs and debt discount	546	584
In process research and development acquired	250	781
Change in fair value of liability instruments	(6)	(2,400)
Loss on disposal of property and equipment	66	0
Share-based compensation expense	606	247
Inventory write off	0	107
Non-cash lease expense	24	3
Increases (decreases) in cash caused by changes in operating assets and liabilities:
Accounts receivable	0	1,169
Other current assets	(496)	126
Other assets	0	58
Accounts payable and accrued expenses	1,734	(1,234)
Other long-term liabilities	0	0
Net cash used in operating activities	(10,280)	(8,434)
Cash flows from (used in) investing activities:
Purchases of property and equipment and intangible assets	(144)	(93)
Proceeds from sale of property and equipment	62	0
In process research and development acquired from NanoTx Therapeutics	0	(400)
Net cash used in investing activities	(82)	(493)
Cash flows from financing activities:
Principal payments of long-term obligations	(268)	(5,307)
Payment of financing lease liability	(8)	(117)
Proceeds from exercise of warrants	2,017	1,098
Proceeds from sale of common stock	18,675	4,007
Net cash provided by (used in) financing activities	20,416	(319)
Net increase (decrease) in cash and cash equivalents	10,054	(9,246)
Cash and cash equivalents at beginning of period	8,346	17,592
Cash and cash equivalents at end of period	18,400	8,346
Cash paid during period for:
Interest	388	567
Supplemental schedule of non-cash investing and financing activities:
Unpaid offering cost	219	125
Issuance costs paid in common stock	0	463
Common stock issued in payment for in process research and development	0	381
Reclassification of warrants liability to equity	$ 0	$ 4,504

Organization and Operations

12 Months Ended

Dec. 31, 2021

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.

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

The Company incurred net losses of $13.4 million for the year ended December 31, 2021, and as of December 31, 2021, the Company had an accumulated deficit of $446.9 million and cash and cash equivalents of $18.4 million. Additionally, the Company used net cash of $10.3 million to fund its operating activities for the year ended December 31, 2021. In addition, as discussed in Note 14, the full magnitude of the coronavirus pandemic on the Company’s financial condition, liquidity and future results of operations is uncertain. The Company expect that its research and development expenditures will increase in absolute dollars in 2022.

As disclosed in more detail in Note 12, the Company had entered into various financing agreements during 2020 through January 2022, and raised capital by issuing its common stock. The Company believes its current cash and cash equivalents will be sufficient to fund its operations for at least the next 12 months from the date these consolidated financial statements are issued.

The Company continues to seek additional capital through strategic transactions and from other financing alternatives. 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.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2021

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 include cash in readily available checking and savings accounts. The Company held no investments as of December 31, 2021 and 2020. 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.

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 of the long-term debt is materially consistent with 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, 2021 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

The Company did not have any revenue or related costs during 2021. Prior to 2021, the Company earned 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 were recorded as government contract and other within development revenue. Government contract revenue was recorded at the gross amount of the reimbursement. The costs associated with these reimbursements were reflected as a component of research and development

expense in the Company’s statements of operations. The Company recognized $0.3 million in BARDA revenue for the year ended December 31, 2020.

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.

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 qualified expenses that were incurred for the years ended December 31, 2020, related to the BARDA Agreement. There was no BARDA related costs during the year ended December 31, 2021.

Acquired In-Process Research and Development (IPR&D)

Acquired IPR&D represents the value assigned to research and development assets that have not reached technological feasibility. Upon the acquisition of IPR&D, the Company completes an assessment of whether the acquisition constitutes the purchase of a single asset or group of assets. The Company considers multiple factors in this assessment, including the nature of the technology acquired, the presence or absence of separate cash flows, the development process and stage of completion, quantitative significance, and the Company's rationale for entering into the transaction.

If the Company acquires a business as defined under applicable accounting standards, then the acquired IPR&D is capitalized as an intangible asset on the consolidated balance sheets and recorded at fair value. If the Company acquires an asset or group of assets that do not meet the definition of a business under applicable accounting standards, then the acquired IPR&D is expensed as research and development in the consolidated statements of operations and comprehensive loss on its acquisition date. Future costs to develop these assets are recorded to research and development expense as they are incurred until such time that the asset or group of assets reaches technological feasibility, if ever.

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, 2021 and 2020, 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, 2021 and 2020, 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, 2021 and 2020, as their inclusion would be antidilutive.

Concentration Risk

Although the Company’s contracts with its vendors are not exclusive, the Company currently uses sole source providers for core materials used in its clinical trials.

Recently Issued and Recently Adopted Accounting Pronouncements

Recently Issued Accounting Pronouncements

In June 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. 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 December 2019, the FASB issued ASU No. 2019-12, Income Taxes, Simplifying the Accounting for Income Taxes (“ASU 2019-12”). The new guidance eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. It also clarifies and simplifies other aspects of the accounting for income taxes. ASU 2019-12 became effective for the Company on January 1, 2021. Adoption of ASU 2019-12 did not have a material impact on the Company’s consolidated financial statements.

Fair Value Measurements

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurements

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 sale of common stock in a registration offering in September 2019 (“Series U Warrants”) were classified as liabilities at issuance. The Series U warrants were marked to market at each subsequent reporting date 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 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, 2021			As of December 31, 2020
Expected term		2.75 years		3.75 years
Common stock market price	$	1.05		$	2.02
Risk-free interest rate		0.91	%		0.24	%
Expected volatility		143.2	%		149.0	%
Resulting fair value (per warrant)	$	0.58		$	1.56

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

	Years ended December 31,
Warrant liability	2021			2020
Beginning balance	$	7		$	6,929
Change in fair value of warrants		(6	)		(2,418	)
Reclassification to equity		—			(4,504	)
Ending balance	$	1		$	7

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 for the year ended December 31, 2020.

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.

Loss per Share

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Loss per Share

5.	Loss per Share

The following were excluded from the diluted loss per share calculation for the periods presented because their effect would be anti-dilutive:

	For the Year Ended December 31,
	2021		2020
Outstanding stock options		1,170,890		531,336
Preferred stock		422,867		422,985
Outstanding warrants		2,141,378		3,113,625
Total		3,735,135		4,067,946

Composition of Certain Financial Statement Captions

12 Months Ended

Dec. 31, 2021

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, 2021 and 2020, other current assets were comprised of the following (in thousands):

	December 31,
	2021		2020
Prepaid services	$	622	$	131
Prepaid insurance		695		639
Other		7		59
	$	1,324	$	829

Property and Equipment, net

As of December 31, 2021 and 2020, property and equipment, net, were comprised of the following (in thousands):

	December 31,
	2021			2020
Office and computer equipment	$	1,231		$	1,525
Leasehold improvements		1,661			1,682
		2,892			3,207
Less accumulated depreciation		(1,415	)		(1,387	)
	$	1,477		$	1,820

Depreciation expense totaled $0.4 million for each of the years ended December 31, 2021 and 2020, respectively.

Intangible Assets, net

As of December 31, 2021, intangible assets included the net book value of costs incurred for software upgrades.

Accounts Payable and Accrued Expenses

As of December 31, 2021 and 2020, accounts payable and accrued expenses were comprised of the following (in thousands):

	December 31,
	2021		2020
Accounts payable	$	2,611	$	789
Accrued payroll and bonus		781		738
Accrued professional fees		189		276
Accrued vacation and compensation		252		245
Finance lease obligation -- current		—		10
Other current liabilities		122		23
Accrued R&D studies		196		—
	$	4,151	$	2,081

Commitments and Contingencies

12 Months Ended

Dec. 31, 2021

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. Lease renewable options are included in the estimation of lease term when it is reasonably certain that the Company will exercise such options.

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.

The Company leases laboratory, office and storage facilities in San Antonio, Texas, under operating lease agreements that expire in 2025. The Company also leases certain office space in Austin, Texas under a month-to-month operating lease agreement.

On March 1, 2021, the Company entered into a lease agreement for office space in Charlottesville, Virginia (the “Charlottesville Lease”). The Charlottesville Lease has a term of 12 months and is renewable for four additional one-year periods. The minimum lease payment is $30,000 for the first twelve months, subject to a 3% annual increase if and when the lease is renewed. The lease commencement date is April 1, 2021. The Company measured the operating lease right-of-use asset and related lease liability related to the Charlottesville Lease as of the lease commencement date.

In addition, the Company has entered into leases for 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.

During 2021, contractual terms of all finance leases had expired and the Company did not have any right-of-use assets or lease liabilities relating to finance leases as of December 31, 2021. 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):

		2021			2020
Assets
Operating	$	341		$	636
Financing		—			7
Total leased assets	$	341		$	643

Liabilities
Current:
Operating	$	111		$	123
Financing	—			10
Noncurrent:
Operating	269			528
Total lease liabilities	$	380		$	661

Weighted-average remaining lease term (years) - operating leases	2.86			6.57
Weighted-average remaining lease term (years) - finance leases	—			0.42
Weighted-average discount rate - operating leases		9.00	%		7.79	%
Weighted-average discount rate - finance leases		N/A			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,
		2021		2020
Lease expense:
Operating lease expense	$	211	$	210
Finance lease expense:
Depreciation of right-of-use assets		7	127
Interest expense on lease liabilities	—		4
Total lease expense	$	218	$	341

Cash payment information:
Operating cash used for operating leases	$	206	$	204
Financing cash used for financing leases	8		117
Total cash paid for amounts included in the measurement of lease liabilities	$	214	$	321

Total rent expenses for each of the years ended December 31, 2021 and 2020 was $0.2 million, 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, 2021 are as follows (in thousands):


		Operating Leases
2022	$	159
2023		137
2024		113
2025		18
Thereafter			—
Total minimum lease payments	$		427
Less: amount representing interest			(47	)
Present value of obligations under leases			380
Less: current portion			(111	)
Noncurrent lease obligations	$		269

Piramal Master Services Agreement

On January 8, 2021, the Company entered into a Master Services Agreement (the “MSA”) with Piramal Pharma Solutions, Inc. (“Piramal”), for Piramal to perform certain services related to the development, manufacture, and supply of the Company’s ¹⁸⁶RNL-Liposome Intermediate Drug Product. The MSA includes the transfer of analytical methods, development of microbiological methods, process transfer and optimization, intermediate drug product manufacturing, and stability studies for the Company, which has been initiated at Piramal’s facility located in Lexington, Kentucky.

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. Either party may terminate the MSA upon an uncured material breach by the other party or upon the bankruptcy or insolvency of the other party.

Other Commitments and Contingencies

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, 2021, the Company did not have any clinical research study obligations.

Legal proceedings

On June 22, 2021, the Company was named as a defendant in an action brought by Lorem Vascular, Pte. Ltd. (“Lorem”) in the District Court for the District of Delaware. The complaint alleges false representations were made to Lorem regarding the manufacturing facility in the United Kingdom (the “UK Facility”) that Lorem purchased from the Company under the Equity Purchase Agreement, dated March 29, 2019, between the Company and Lorem (the “Lorem Agreement”). Lorem also claims that false representations were made regarding the UK Facility’s certification to sell and distribute devices in the European Union and export such devices to China. In connection with these allegations, Lorem claims entitlement to at least $6,000,000 in compensatory damages and operational costs and expenses (collectively, the “Lorem Claim”). The Company believes that the claims from Lorem are without merit and intends to vigorously defend the case and on August 12, 2021, the Company filed a Motion to Dismiss asking the District Court to dismiss the Lorem Claim. Lorem filed an opposition on September 9, 2021, which the Company responded to on September 30, 2021. On February 7, 2022, a hearing was held on the Company’s Motion to Dismiss and the presiding judge ruled against the Motion to Dismiss. The Company is moving forward with discovery in this case.

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.

Term Loan Obligations

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Term Loan Obligations

8.	Term Loan Obligations

On May 29, 2015, the Company entered into the Loan and Security Agreement (the “Loan and Security Agreement”), pursuant to which Oxford Finance, LLC (“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 June 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 in April 2019, 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 (the “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 June 1, 2024. The principal repayment start date was further deferred to November 1, 2021. 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 Term Loan. 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, 2021, there was $4.0 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 year ended December 31, 2021 and 2020 was $0.9 million and $1.1 million, respectively. Interest expense is calculated using the effective interest method; therefore it is inclusive of non-cash amortization in the amount of $0.5 million and $0.6 million for the year ended December 31, 2021 and 2020, respectively, related to the amortization of the debt discount, deferred financing 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, 2021, the Company has not received any notification or indication from Oxford to invoke the material adverse change clause.

Additional details relating to the outstanding Term Loan as of December 31, 2021 and 2020 are presented in the following table (in thousands):

Year ended December 31, 2021

Origination Date

Original

Loan

Amount

Interest

Rate**

Current

Monthly

Payment***

Amended expiration date

Remaining

Principal

(Face Value)

May 2015

17,700

8.95

134

June 1, 2024

4,021

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

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

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

***	Monthly payment as of December 2021, which reflects principal and interest

As of December 31, 2021, the future contractual principal and final fee payments on all of our debt obligations are as follows (as thousands):

Years Ending December 31,
2022	$	1,608
2023		1,608
2024		3,996
Total	$	7,212

Reconciliation of Face Value to Book Value as of December 31, 2021
Total debt obligations, including final payment fee (Face Value)	$	7,212
Less: Debt discount		(599	)
Total obligation		6,613
Less: Current portion		1,608
Term loan obligation	$	5,005

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

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+ Details

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

9.	Income Taxes

The Company has recorded a full valuation allowance against its net deferred tax assets and due to our net losses for the years ended December 31, 2021 and 2020, there was no provision or benefit for income taxes recorded.

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, 2021 and 2020, respectively, is as follows:

	2021			2020
Income tax expense (benefit) at federal statutory rate		(21.0	)%		(21.0	)%
Change in valuation allowance		0.9	%		23.6	%
Income tax expense (benefit) at state statutory rate		(0.6	)%		(8.9	)%
Stock compensation		0.7	%		6.9	%
NOLs expiring and adjustments to NOL		20.3	%		6.0	%
Research credit		(0.8	)%		(1.1	)%
Return to provision		0.5	%		1.0	%
Change in state rate		—			(0.5	)%
Mark to market adjustment		—			(6.1	)%
Other, net		—			0.1	%
		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, 2021 and 2020 are as follows (in thousands):

	2021			2020
Deferred tax assets:
Accrued expenses	$	41		$	128
Stock based compensation		164			168
Net operating loss carryforwards		95,310			95,114
Income tax credit carryforwards		8,864			8,756
Property and equipment, principally due to differences in depreciation		19			16
Intangible assets		451			556
Other, net		82			182
		104,931			104,920
Valuation allowance		(104,857	)		(104,742	)
Total deferred tax assets, net of allowance		74			178
Deferred tax liabilities:
Other		(74	)		(178	)
Total deferred tax liability		(74	)		(178	)
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 tax assets are realizable, the valuation allowance will be reduced. The Company has recorded a full valuation allowance of $104.9 million as of December 31, 2021 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 $0.1 million during the year ended December 31, 2021.

At December 31, 2021, we had federal, and state tax loss carry forwards of approximately $395.7 million, and $175.8 million, respectively. The federal and state net operating loss carry forwards begin to expire in 2023 and 2028, respectively, if unused. The federal net operating loss carryover includes $45.5 million of net operating losses generated after 2017. 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 $6.5 million and $5.5 million, respectively, before 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 2022, 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, 2021 and 2020.

Following is a tabular reconciliation of the unrecognized tax benefits activity during the years ended December 31, 2021 and 2020 (in thousands):

	2021			2020
Unrecognized Tax Benefits – Beginning	$	2,223		$	2,234
Gross decreases – tax positions in prior period		(44	)		(44	)
Gross increase – current-period tax positions		69			33
Unrecognized Tax Benefits – Ending	$	2,248		$	2,223

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, 2021.

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 2018 (federal) and 2017 (CA) remain open to examination by the taxing authority. While not open to examination, the tax attributes generated in tax years 2002 (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.

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+ Details

Employee Benefit Plan

12 Months Ended

Dec. 31, 2021

Compensation And Retirement Disclosure [Abstract]

Employee Benefit Plan

10.	Employee Benefit Plan

The Company implemented a 401(k) retirement savings and profit sharing plan (the “Plan”) effective January 1, 1999. During 2021, the Company commenced safe harbor matching contribution for up to 4% of eligible employee contributions. Total matching contribution under the Plan amounted to approximately $40,000 for the year ended December 31, 2021. The Company made no matching contribution to the Plan in 2020.

License Agreement

12 Months Ended

Dec. 31, 2021

License Agreement [Abstract]

License Agreement

11. License Agreements

UT Health Science Center at San Antonio (“UTHSA”) License Agreement

On December 31, 2021, the Company entered into a Patent and Know-How License Agreement (the “UTHSA License Agreement”) with The University of Texas Health Science Center at San Antonio, pursuant to which UTHSA granted the Company an irrevocable, perpetual, exclusive, fully paid-up license, with the right to sublicense and to make, develop, commercialize and otherwise exploit certain patents, know-how and technology related to the development of biodegradable alginate microspheres (BAM) containing nanoliposomes loaded with imaging and/or therapeutic payloads.

Pursuant to the UTHSA License Agreement, the Company is required to make an upfront payment of $250,000, which was recorded as in process research and development acquired in the statement of operations for the year ended December 31, 2021. The upfront payment was paid in cash in January 2022. Furthermore, the Company may pay up to $30.3 million in development and sales milestone payments and a tiered single digit royalty on U.S. and European sales. In addition, the Company is obligated to pay a $50,000 annual maintenance fee starting 2024, as well as low single digit of sales-based royalty under the UTHSA License Agreement.

NanoTx License Agreement

On March 29, 2020, the Company and NanoTx, Corp. (“NanoTx”) entered into a Patent and Know-How License Agreement (the“NanoTx License Agreement”), pursuant to which NanoTx granted the Company an irrevocable, perpetual, exclusive, fully

paid-up license, with the right to sublicense and to make, develop, commercialize and otherwise exploit certain patents, know-how and technology related to the development of radiolabeled nanoliposomes.

On May 7, 2020, all closing conditions under the NanoTx License Agreement were satisfied and the Company paid an upfront payment of $400,000 in cash and issued 230,769 shares of its common stock to NanoTx. Cash and the fair value of common stock issued totaled $781,000 and is recorded as in-process research and development expenses, pursuant to authoritative literature for asset acquisition, in the consolidated statement of operations and comprehensive loss for the year ended December 31, 2020. Pursuant to the terms of the NanoTx License Agreement, the Company may be required to pay up to $136.5 million in development and sales milestone payments and a tiered single-digit royalty on U.S. and European sales.

Stockholders' Equity

12 Months Ended

Dec. 31, 2021

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. On September 21, 2021, Series A 3.6% Convertible Preferred Stock was eliminated. There were no shares of Series A 3.6% Convertible Preferred Stock immediately prior to September 21, 2021, or December 31, 2020. There were 1,014 and 1,016 shares of Series B Convertible Preferred Stock outstanding as of December 31, 2021 and December 31, 2020, respectively. There were 938 shares of Series C Preferred Stock outstanding as of each of December 31, 2021 and December 31, 2020.

As of December 31, 2021, 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 1,014 shares of Series B Convertible Preferred Stock that can be converted into an aggregate of 5,978 shares of common stock.

Warrants

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 (the “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 for the year ended December 31, 2020.

As of December 31, 2021, there were 2,141,000 outstanding Series U Warrants (of which 2,138,500 warrants were equity classified) which can be exercised into an aggregate of 2,141,000 shares of common stock.

Common Stock

Lincoln Park Purchase Agreements

On September 30, 2020, the Company entered into the 2020 Purchase Agreement and registration rights agreement pursuant to which Lincoln Park 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 had the right, but not the obligation, to sell to Lincoln Park, and Lincoln Park was obligated to purchase up to $25.0 million of the Company’s common stock. Such sales of common stock by the Company were 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 provided 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 could 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 was 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 could 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 exceeded 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 can 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 had no right to require the Company to sell any shares of common stock to Lincoln Park, but Lincoln Park was obligated to make purchases as the Company directed, subject to certain conditions.

During the year ended December 31, 2020, the Company issued 353,113 shares, excluding 180,701 shares issued as a commitment fee, of common stock under the 2020 Purchase Agreement for total net proceeds of approximately $0.7 million. During the year ended December 31, 2021, the Company issued 5,685,186 shares of its common stock under the 2020 Purchase Agreement for net proceeds of approximately $12.5 million. As described in Note 15, subsequent to January 1, 2022, the Company issued approximately 5,665,000 shares of its common stock for net proceeds of $7.0 million. The Company no longer had any additional shares of common stock registered to sell under the 2020 Purchase Agreement.

At-the-market Issuances

On January 14, 2022, the Company entered into an Equity Distribution Agreement (the “2022 Distribution Agreement”) with Canaccord Genuity LLC (the “Agent”), 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 $5,000,000 Share, with the Agent acting as an agent for sales. The Agent will use its commercially reasonable efforts to sell the Shares requested by the Company to be sold on its behalf. The Company has no obligation to sell any of the Shares. The Company has no obligation to sell any of the Shares. The Company may instruct the Agent not to sell the Shares if the sales cannot be effected at or above the price designated by us from time to time and the Company may at any time suspend sales pursuant to the 2022 Distribution Agreement. As described in Note 15, subsequent to January 1, 2022, the Company issued 1,000,000 shares under the 2022 Distribution Agreement for net proceeds of approximately $0.9 million.

On October 23, 2020, the Company entered into the 2020 Distribution Agreement with Canaccord Genuity LLC (“Canaccord”), pursuant to which the Company issued and sold the ATM Shares, depending on market demand, with Canaccord acting as an agent for sales. The Company had no obligation to sell any of the ATM Shares and it could instruct Canaccord not to sell the ATM Shares if the sales could not be effected at or above the price the Company designated from time to time and the Company could at any time suspend sales pursuant to the 2020 Distribution Agreement.

During the year ended December 31, 2020, the Company issued 1,616,331 shares under the 2020 Distribution Agreement for net proceeds of approximately $3.2 million. During the year ended December 31, 2021, the Company issued 2,179,193 shares under the 2020 Distribution Agreement for net proceeds of $6.3 million. As of December 31, 2021, there were no remaining shares that may be issued and sold under the 2020 Distribution Agreement.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Stock-based Compensation

12 Months Ended

Dec. 31, 2021

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, 2021, there were 90,389 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 (the “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). On May 17, 2021, the stockholders of the Company approved an amendment and restatement to the 2020 Plan to increase the total number of shares of common stock reserved for issuance under the 2020 Plan by 1,000,000 shares. As of December 31, 2021, there were 640,212 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, 2021 is as follows:

	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Balance as of December 31, 2020		531,336		$	10.01
Granted		680,227		$	2.52
Cancelled/forfeited		(40,673	)	$	16.69
Balance as of December 31, 2021		1,170,890		$	5.01		9.00	$	-
Vested and expected to vest at December 31, 2021		378,010		$	10.37		8.70	$	-
Exercisable at December 31, 2021		1,089,944		$	5.16		9.00	$	-

The Company settles exercises of stock options with newly issued shares of its common stock. There were no stock options exercised in 2021 or 2020.

The fair value of each option awarded during the years ended December 31, 2021 and 2020 was estimated on the date of grant using the Black-Scholes-Merton option valuation model based on the following weighted-average assumptions:

	December 31, 2021			December 31, 2020
Expected term		6 years		5.8 years
Risk-free interest rate		1.00	%		0.58	%
Expected volatility		127.0	%		128.6	%
Dividends		0	%		0	%
Resulting fair value	$	2.23		$	1.87

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, 2021 and 2020 in the statement of operations and comprehensive loss:

	Years ended December 31,
	2021		2020
Research and development	$	75	$	32
General and administrative		531		215
Total share-based compensation	$	606	$	247

As of December 31, 2021, the total compensation cost related to non-vested stock options and stock awards not yet recognized for all our plans is approximately $1.5 million, which is expected to be recognized as a result of vesting under service conditions over a weighted average period of 2.9 years.

COVID-19 Pandemic and CARES Act

12 Months Ended

Dec. 31, 2021

Risks And Uncertainties [Abstract]

COVID-19 Pandemic and CARES Act

14. COVID-19 Pandemic and CARES Act

A novel strain of coronavirus (COVID-19) was declared a global pandemic by the World Health Organization in March 2020. COVID-19 has presented substantial public health and economic challenges and is affecting economies, financial markets and business operations around the world. International and U.S. governmental authorities in impacted regions have taken action in an effort to slow the spread of COVID-19, including issuing varying forms of “stay-at-home” orders, and restricting business functions outside of one’s home. In response, the Company put restrictions on employee travel and working from its executive offices with many employees continuing their work remotely. While the Company has implemented additional health and safety precautions and protocols in response to the pandemic and government guidelines, the Company has not experienced a significant impact on its business and operations. However, the Company may experience disruptions that could adversely impact its business operations as well as its preclinical studies and clinical trials. The Company is currently continuing the clinical trials it has underway in sites across the U.S., and, although there has been no significant impact to date, the Company expects that COVID-19 precautions may directly or indirectly impact the timeline for some of its clinical trials. Some of the Company’s clinical trial sites, including those located in areas severely impacted by the pandemic, have placed new patient enrollment into clinical trials on hold. In addition, some clinical trial sites have imposed limited accessibility to conduct clinical monitoring and training on-site. The Company considered the impacts of COVID-19 on the assumptions and estimates used to prepare its consolidated financial statements and determined that there were no material adverse impacts on the Company’s results of operations and financial position at December 31, 2021. The full extent to which the COVID-19 pandemic will directly or indirectly impact its business, results of operations and financial condition, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat it, as well as the economic impact on local, regional, national and international markets.

In response to the COVID-19 pandemic, the CARES Act was signed into law on March 27, 2020. The CARES Act, among other things, includes tax provisions relating to refundable payroll tax credits, deferment of employer’s social security payments, net operating loss utilization and carryback periods, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property (QIP). The CARES Act had no material impact on the Company’s income tax provision for the year ended December 31, 2021. The Company continues to evaluate the impact of the CARES Act on its financial position, results of operations and cash flows.

Subsequent Events

12 Months Ended

Dec. 31, 2021

Subsequent Events [Abstract]

Subsequent Events

15. Subsequent Events

From January 1, 2022 through the date of filing of this Form 10-K, the Company issued approximately 5,665,000 shares of its common stock for net proceeds of $7.0 million under the 2020 Purchase Agreement. In addition, the Company issued 1,000,000 shares under the 2022 Distribution Agreement for net proceeds of approximately $0.9 million.

Financial Statement Schedules

12 Months Ended

Dec. 31, 2021

Valuation And Qualifying Accounts [Abstract]

Financial Statement Schedules

(a) (2)

Financial Statement Schedules.

None.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2021
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 include cash in readily available checking and savings accounts. The Company held no investments as of December 31, 2021 and 2020. 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.
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 of the long-term debt is materially consistent with 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, 2021 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 The Company did not have any revenue or related costs during 2021. Prior to 2021, the Company earned 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 were recorded as government contract and other within development revenue. Government contract revenue was recorded at the gross amount of the reimbursement. The costs associated with these reimbursements were reflected as a component of research and development expense in the Company’s statements of operations. The Company recognized $0.3 million in BARDA revenue for the year ended December 31, 2020. 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.
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 qualified expenses that were incurred for the years ended December 31, 2020, related to the BARDA Agreement. There was no BARDA related costs during the year ended December 31, 2021.
Acquired In-Process Research and Development (IPR&D)	Acquired In-Process Research and Development (IPR&D) Acquired IPR&D represents the value assigned to research and development assets that have not reached technological feasibility. Upon the acquisition of IPR&D, the Company completes an assessment of whether the acquisition constitutes the purchase of a single asset or group of assets. The Company considers multiple factors in this assessment, including the nature of the technology acquired, the presence or absence of separate cash flows, the development process and stage of completion, quantitative significance, and the Company's rationale for entering into the transaction. If the Company acquires a business as defined under applicable accounting standards, then the acquired IPR&D is capitalized as an intangible asset on the consolidated balance sheets and recorded at fair value. If the Company acquires an asset or group of assets that do not meet the definition of a business under applicable accounting standards, then the acquired IPR&D is expensed as research and development in the consolidated statements of operations and comprehensive loss on its acquisition date. Future costs to develop these assets are recorded to research and development expense as they are incurred until such time that the asset or group of assets reaches technological feasibility, if ever.
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, 2021 and 2020, 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, 2021 and 2020, 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, 2021 and 2020, as their inclusion would be antidilutive.
Concentration Risk	Concentration Risk Although the Company’s contracts with its vendors are not exclusive, the Company currently uses sole source providers for core materials used in its clinical trials.
Recently Issued and Recently Adopted Accounting Pronouncements	Recently Issued and Recently Adopted Accounting Pronouncements Recently Issued Accounting Pronouncements In June 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. 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 December 2019, the FASB issued ASU No. 2019-12, Income Taxes, Simplifying the Accounting for Income Taxes (“ASU 2019-12”). The new guidance eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. It also clarifies and simplifies other aspects of the accounting for income taxes. ASU 2019-12 became effective for the Company on January 1, 2021. Adoption of ASU 2019-12 did not have a material impact on the Company’s consolidated financial statements.

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

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	2021			2020
Beginning balance	$	7		$	6,929
Change in fair value of warrants		(6	)		(2,418	)
Reclassification to equity		—			(4,504	)
Ending balance	$	1		$	7

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, 2021			As of December 31, 2020
Expected term		2.75 years		3.75 years
Common stock market price	$	1.05		$	2.02
Risk-free interest rate		0.91	%		0.24	%
Expected volatility		143.2	%		149.0	%
Resulting fair value (per warrant)	$	0.58		$	1.56

Loss per Share (Tables)

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities Excluded from Diluted Income (Loss) per Share

The following were excluded from the diluted loss per share calculation for the periods presented because their effect would be anti-dilutive:

	For the Year Ended December 31,
	2021		2020
Outstanding stock options		1,170,890		531,336
Preferred stock		422,867		422,985
Outstanding warrants		2,141,378		3,113,625
Total		3,735,135		4,067,946

Composition of Certain Financial Statement Captions (Tables)

12 Months Ended

Dec. 31, 2021

Composition Of Certain Financial Statement Captions [Abstract]

Other Current Assets

As of December 31, 2021 and 2020, other current assets were comprised of the following (in thousands):

	December 31,
	2021		2020
Prepaid services	$	622	$	131
Prepaid insurance		695		639
Other		7		59
	$	1,324	$	829

Property and Equipment, net

As of December 31, 2021 and 2020, property and equipment, net, were comprised of the following (in thousands):

	December 31,
	2021			2020
Office and computer equipment	$	1,231		$	1,525
Leasehold improvements		1,661			1,682
		2,892			3,207
Less accumulated depreciation		(1,415	)		(1,387	)
	$	1,477		$	1,820

Accounts Payable and Accrued Expenses

As of December 31, 2021 and 2020, accounts payable and accrued expenses were comprised of the following (in thousands):

	December 31,
	2021		2020
Accounts payable	$	2,611	$	789
Accrued payroll and bonus		781		738
Accrued professional fees		189		276
Accrued vacation and compensation		252		245
Finance lease obligation -- current		—		10
Other current liabilities		122		23
Accrued R&D studies		196		—
	$	4,151	$	2,081

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2021

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):

		2021			2020
Assets
Operating	$	341		$	636
Financing		—			7
Total leased assets	$	341		$	643

Liabilities
Current:
Operating	$	111		$	123
Financing	—			10
Noncurrent:
Operating	269			528
Total lease liabilities	$	380		$	661

Weighted-average remaining lease term (years) - operating leases	2.86			6.57
Weighted-average remaining lease term (years) - finance leases	—			0.42
Weighted-average discount rate - operating leases		9.00	%		7.79	%
Weighted-average discount rate - finance leases		N/A			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,
		2021		2020
Lease expense:
Operating lease expense	$	211	$	210
Finance lease expense:
Depreciation of right-of-use assets		7	127
Interest expense on lease liabilities	—		4
Total lease expense	$	218	$	341

Cash payment information:
Operating cash used for operating leases	$	206	$	204
Financing cash used for financing leases	8		117
Total cash paid for amounts included in the measurement of lease liabilities	$	214	$	321

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, 2021 are as follows (in thousands):


		Operating Leases
2022	$	159
2023		137
2024		113
2025		18
Thereafter			—
Total minimum lease payments	$		427
Less: amount representing interest			(47	)
Present value of obligations under leases			380
Less: current portion			(111	)
Noncurrent lease obligations	$		269

Term Loan Obligations (Tables)

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Term Loan Outstanding

Additional details relating to the outstanding Term Loan as of December 31, 2021 and 2020 are presented in the following table (in thousands):

Year ended December 31, 2021

Origination Date

Original

Loan

Amount

Interest

Rate**

Current

Monthly

Payment***

Amended expiration date

Remaining

Principal

(Face Value)

May 2015

17,700

8.95

134

June 1, 2024

4,021

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

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

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

***	Monthly payment as of December 2021, which reflects principal and interest

Future Payments under Obligation

As of December 31, 2021, the future contractual principal and final fee payments on all of our debt obligations are as follows (as thousands):

Years Ending December 31,
2022	$	1,608
2023		1,608
2024		3,996
Total	$	7,212

Face Value to Book Value Reconciliation

Reconciliation of Face Value to Book Value as of December 31, 2021
Total debt obligations, including final payment fee (Face Value)	$	7,212
Less: Debt discount		(599	)
Total obligation		6,613
Less: Current portion		1,608
Term loan obligation	$	5,005

- 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.

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+ Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

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, 2021 and 2020, respectively, is as follows:

	2021			2020
Income tax expense (benefit) at federal statutory rate		(21.0	)%		(21.0	)%
Change in valuation allowance		0.9	%		23.6	%
Income tax expense (benefit) at state statutory rate		(0.6	)%		(8.9	)%
Stock compensation		0.7	%		6.9	%
NOLs expiring and adjustments to NOL		20.3	%		6.0	%
Research credit		(0.8	)%		(1.1	)%
Return to provision		0.5	%		1.0	%
Change in state rate		—			(0.5	)%
Mark to market adjustment		—			(6.1	)%
Other, net		—			0.1	%
		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, 2021 and 2020 are as follows (in thousands):

	2021			2020
Deferred tax assets:
Accrued expenses	$	41		$	128
Stock based compensation		164			168
Net operating loss carryforwards		95,310			95,114
Income tax credit carryforwards		8,864			8,756
Property and equipment, principally due to differences in depreciation		19			16
Intangible assets		451			556
Other, net		82			182
		104,931			104,920
Valuation allowance		(104,857	)		(104,742	)
Total deferred tax assets, net of allowance		74			178
Deferred tax liabilities:
Other		(74	)		(178	)
Total deferred tax liability		(74	)		(178	)
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, 2021 and 2020 (in thousands):

	2021			2020
Unrecognized Tax Benefits – Beginning	$	2,223		$	2,234
Gross decreases – tax positions in prior period		(44	)		(44	)
Gross increase – current-period tax positions		69			33
Unrecognized Tax Benefits – Ending	$	2,248		$	2,223

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Option Activity

A summary of activity for the year ended December 31, 2021 is as follows:

	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Balance as of December 31, 2020		531,336		$	10.01
Granted		680,227		$	2.52
Cancelled/forfeited		(40,673	)	$	16.69
Balance as of December 31, 2021		1,170,890		$	5.01		9.00	$	-
Vested and expected to vest at December 31, 2021		378,010		$	10.37		8.70	$	-
Exercisable at December 31, 2021		1,089,944		$	5.16		9.00	$	-

Weighted-average Assumptions

	December 31, 2021			December 31, 2020
Expected term		6 years		5.8 years
Risk-free interest rate		1.00	%		0.58	%
Expected volatility		127.0	%		128.6	%
Dividends		0	%		0	%
Resulting fair value	$	2.23		$	1.87

Summary of Share-Based Compensation Recognized

The following table summarizes share-based compensation recognized during the years ended December 31, 2021 and 2020 in the statement of operations and comprehensive loss:

	Years ended December 31,
	2021		2020
Research and development	$	75	$	32
General and administrative		531		215
Total share-based compensation	$	606	$	247

Organization and Operations - Additional Information (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
	Jan. 01, 2022	Sep. 30, 2020	Dec. 31, 2021	Dec. 31, 2020
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of common stock			$ 18,675	$ 4,007
Sale of common stock, net			18,581	3,882
Net loss			(13,399)	(8,241)
Accumulated deficit			(446,910)	(433,511)
Net cash used in operating activities			(10,280)	(8,434)
Cash and cash equivalents			$ 18,400	$ 8,346
Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares)			7,864,379	2,150,113
Sale of common stock, net			$ 8	$ 2
2020 Repurchase Agreement [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of common stock			$ 12,500	$ 700
Common stock issued (in shares)			5,685,186	353,113
Sale of common stock, net		$ 25,000
Period exercisable from the date of issuance		36 months
2020 Repurchase Agreement [Member] \| Common Stock [Member] \| Commitment Fee [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Common stock issued (in shares)				180,701
Subsequent Event [Member] \| 2020 Repurchase Agreement [Member] \| Common Stock [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of common stock	$ 7,000
Common stock issued (in shares)	5,665,000
Remaining common stock issued and sold (in shares)	0

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) ReportableUnit Segment	Dec. 31, 2020 USD ($) Segment
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents investments with original maturities	$ 0	$ 0
Impairment loss	0	0
Impairment charges	$ 0
Number of reporting units \| ReportableUnit	1
Qualifying expenditures related to research	$ 0	300,000
Interest or penalties related to income tax matters	$ 0	$ 0
Number of operating segment \| Segment	1	1
ASU 2019-12 [Member]
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted [true false]	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2021
Change in accounting principle, accounting standards update, immaterial effect [true false]	true
BARDA Contract [Member] \| Development [Member]
Summary Of Significant Accounting Policies [Line Items]
Revenue recognized	$ 0	$ 300,000
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

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands			12 Months Ended
	Oct. 02, 2020	Sep. 30, 2020	Dec. 31, 2021	Dec. 31, 2020
Lincoln Park [Member] \| 2020 Purchase Agreement [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Commitment shares issued as commitment fee	180,701
Change in fair value of commitment shares		$ 18,000
Series U Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants issued, registration offering, period			2019-09
Reclassification of number of warrants to equity from amendment of warrants				3,522,500

Fair Value Measurements - Schedule of Estimated Fair Value Determined Using Option Pricing Model Assumptions (Details) - Series U Warrants [Member] - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants expected term	5 years
Level 3 [Member] \| Expected Term [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants expected term	2 years 9 months	3 years 9 months
Level 3 [Member] \| Common Stock Market Price [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	1.05	2.02
Level 3 [Member] \| Risk-free Interest Rate [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	0.91	0.24
Level 3 [Member] \| Expected Volatility [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	143.2	149.0
Level 3 [Member] \| Resulting Fair Value (Per Warrant) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	0.58	1.56

Fair Value Measurements - Summary of Change in Level 3 Warrant Liability Value (Details) - Warrant Liability [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Warrant liability
Beginning balance	$ 7	$ 6,929
Change in fair value of warrants	(6)	(2,418)
Reclassification to equity		(4,504)
Ending balance	$ 1	$ 7

Loss per Share - Schedule of Antidilutive Securities Excluded from Diluted Income (Loss) per Share (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
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)	3,735,135	4,067,946
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)	1,170,890	531,336
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)	422,867	422,985
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)	2,141,378	3,113,625

Composition of Certain Financial Statement Captions - Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Other Current Assets [Abstract]
Prepaid services	$ 622	$ 131
Prepaid insurance	695	639
Other	7	59
Total other current assets	$ 1,324	$ 829

Composition of Certain Financial Statement Captions - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property and Equipment, net [Abstract]
Office and computer equipment	$ 1,231	$ 1,525
Leasehold improvements	1,661	1,682
Property and equipment, gross	2,892	3,207
Less accumulated depreciation	(1,415)	(1,387)
Property and equipment, net	$ 1,477	$ 1,820

Composition of Certain Financial Statement Captions - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Composition Of Certain Financial Statement Captions [Abstract]
Depreciation expense	$ 0.4	$ 0.4

Composition of Certain Financial Statement Captions - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounts Payable and Accrued Expenses [Abstract]
Accounts payable	$ 2,611	$ 789
Accrued payroll and bonus	781	738
Accrued professional fees	189	276
Accrued vacation and compensation	$ 252	245
Finance lease obligation -- current		$ 10
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accounts payable and accrued expenses, Total	Accounts payable and accrued expenses, Total
Other current liabilities	$ 122	$ 23
Accrued R&D studies	196
Accounts payable and accrued expenses, Total	$ 4,151	$ 2,081

Commitments and Contingencies - Additional Information (Details) - USD ($)				12 Months Ended
	Jun. 22, 2021	Mar. 01, 2021	Jan. 08, 2021	Dec. 31, 2021	Dec. 31, 2020
Recorded Unconditional Purchase Obligation [Line Items]
Minimum lease payment				$ 427,000
Rent expense				200,000	$ 200,000
Contractual obligation				7,212,000
Lorem Vascular Pte Ltd [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Compensatory damages and operational	$ 6,000,000
Pre-clinical Research Study Obligations [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Contractual obligation				$ 0
Charlottesville [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Lessee, operating lease, option to extend		The Charlottesville Lease has a term of 12 months and is renewable for four additional one-year periods.
Lessee, operating lease, term of contract		12 months
Lessee, operating lease, existence of option to extend [true false]		true
Lessee, operating lease, renewal term		1 year
Minimum lease payment		$ 30,000
Annual increase in lease rate		3.00%
Lease commencement date		Apr. 01, 2021
Piramal Pharma Solutions, Inc. [Member]
Recorded Unconditional Purchase Obligation [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.
San Antonio, Texas [Member] \| Office Laboratory and Storage Space [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Operating leases expiry year				2025

Commitments and Contingencies - Summary of Lease Liabilities and Right-of-Use Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets
Operating	$ 341	$ 636
Financing		$ 7
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Total leased assets	$ 341	$ 643
Liabilities
Operating lease liabilities, current	111	123
Financing lease liabilities, current		10
Operating lease liabilities. noncurrent	269	528
Total lease liabilities	$ 380	$ 661
Weighted-average remaining lease term (years) - operating leases	2 years 10 months 9 days	6 years 6 months 25 days
Weighted-average remaining lease term (years) - finance leases		5 months 1 day
Weighted-average discount rate - operating leases	9.00%	7.79%
Weighted-average discount rate - finance leases		5.00%

Commitments and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Lease expense:
Operating lease expense	$ 211	$ 210
Finance lease expense:
Depreciation of right-of-use assets	7	127
Interest expense on lease liabilities		4
Total lease expense	218	341
Cash payment information:
Operating cash used for operating leases	206	204
Financing cash used for financing leases	8	117
Total cash paid for amounts included in the measurement of lease liabilities	$ 214	$ 321

Commitments and Contingencies - Summary of Future Minimum Annual Lease Payments under Operating and Financing Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Operating Leases
2022	$ 159
2023	137
2024	113
2025	18
Total minimum lease payments	427
Less: amount representing interest	(47)
Present value of obligations under leases	380
Less: current portion	(111)	$ (123)
Noncurrent operating lease liability	$ 269	$ 528

Term Loan Obligations (Details) - USD ($)				12 Months Ended
Term Loan Obligations (Details) - USD ($)	Mar. 29, 2020	Mar. 28, 2020	May 29, 2015	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Warrant exercise price (in dollars per share)					$ 2.25
Interest expense				$ 932,000	$ 1,107,000
Non-cash amortization				$ 500,000	$ 600,000
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	Jun. 01, 2024	Sep. 01, 2021	May 01, 2021
Fees amount associated with loan			$ 3,200,000	$ 3,200,000
Number of shares callable by warrants (in shares)			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				$ 2,000,000.0
Debt principal repayment start date	May 01, 2021	May 01, 2020
Prepayments of term loan	$ 5,000,000.0
Related final payment	300,000
Term loan, remaining amount	4,300,000
Amendment fee	$ 1,000,000.0
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				$ 4,000,000.0

Term Loan Obligations - Term Loan Outstanding (Details) - Term Loan [Member] - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2021

Dec. 31, 2020

May 29, 2015

Additional details relating term loan that is outstanding [Abstract]

Origination Date

May 29, 2015

Original Loan Amount

$ 17,700

Interest Rate

^[1]

8.95%

Current Monthly Payment

$ 134

^[2]

$ 32

^[3]

Amended expiration date

Jun. 01, 2024

May 31, 2024

Remaining Principal (Face Value)

$ 4,021

$ 4,289

[1]	3 month LIBOR rate with a floor of 1% plus 7.95%
[2]	Monthly payment as of December 2021,
[3]	Monthly payment as of December 2020, which reflects interest only

Term Loan Obligations - Future Payments under Obligation (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Future contractual principal and final fee payments on all debt [Abstract]
2022	$ 1,608
2023	1,608
2024	3,996
Total	$ 7,212

Term Loan Obligations - Face Value to Book Value Reconciliation (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Face Value to Book Value [Abstract]
Total debt obligations, including final payment fee (Face Value)	$ 7,212
Less: Debt discount	(599)
Total obligation	6,613
Term loan obligation, current	1,608	$ 6,335
Term loan obligation	$ 5,005

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Provision or benefit for income taxes	$ 0	$ 0
Income Tax Contingency [Abstract]
Valuation allowance	104,900,000
Increase (decrease) in valuation allowance	$ 100,000
Net operating loss carryforwards, Expire date	begin to expire in 2023 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	$ 395,700,000
Federal tax carry forward		$ 6,500,000
Federal tax credit carryforward, Expiration date	begin to expire in 2022
Net operating losses	$ 45,500,000
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	$ 175,800,000

Income Taxes - Reconciliation of Total Income Tax Provision (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
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	0.90%	23.60%
Income tax expense (benefit) at state statutory rate	(0.60%)	(8.90%)
Stock compensation	0.70%	6.90%
NOLs expiring and adjustments to NOL	20.30%	6.00%
Research credit	(0.80%)	(1.10%)
Return to provision	0.50%	1.00%
Change in state rate		(0.50%)
Mark to market adjustment		(6.10%)
Other, net		0.10%
Total income tax provision	0.00%	0.00%

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets [Abstract]
Accrued expenses	$ 41	$ 128
Stock based compensation	164	168
Net operating loss carryforwards	95,310	95,114
Income tax credit carryforwards	8,864	8,756
Property and equipment, principally due to differences in depreciation	19	16
Intangible assets	451	556
Other, net	82	182
Deferred tax assets (Total)	104,931	104,920
Valuation allowance	(104,857)	(104,742)
Total deferred tax assets, net of allowance	74	178
Deferred tax liabilities [Abstract]
Other	(74)	(178)
Total deferred tax liability	(74)	(178)
Net deferred tax assets (liability)	$ 0	$ 0

Income Taxes - Unrecognized Tax Benefits Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Schedule of reconciliation of unrecognized tax benefits activity [Roll Forward]
Unrecognized Tax Benefits – Beginning	$ 2,223	$ 2,234
Gross decreases – tax positions in prior period	(44)	(44)
Gross increase – current-period tax positions	69	33
Unrecognized Tax Benefits – Ending	$ 2,248	$ 2,223

Employee Benefit Plan - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Defined Contribution Plan Disclosure [Line Items]
Discretionary or matching contributions	$ 40,000	$ 0
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of matching contribution for employee contributions	4.00%

License Agreement - Additional Information (Details) - USD ($)		12 Months Ended
	May 07, 2020	Dec. 31, 2021	Dec. 31, 2020
Common stock, shares issued (in shares)		15,510,025	6,749,028
Common stock, $0.001 par value; 100,000,000 shares authorized; 15,510,025 and 6,749,028 shares issued and outstanding in 2021 and 2020, respectively		$ 16,000	$ 7,000
UTHSA License Agreement [Member]
License fee payment in cash		250,000
License agreement maintenance fee		50,000
UTHSA License Agreement [Member] \| Development And Sales Milestone [Member]
Milestone payments		$ 30,300,000
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; 15,510,025 and 6,749,028 shares issued and outstanding in 2021 and 2020, respectively	$ 781,000
Nano Tx Licenses Agreement [Member] \| Development And Sales Milestone [Member]
Milestone payments	$ 136,500,000

Stockholders' Equity - Preferred Stock (Details) - $ / shares			12 Months Ended
	Sep. 21, 2021	Sep. 20, 2021	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)			5,000,000	5,000,000
Preferred stock, par value (in dollars per share)			$ 0.001	$ 0.001
Preferred stock, shares outstanding (in shares)			1,952	1,954
Series A Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)		0		0
Convertible preferred stock		3.60%		3.60%
Series A 3.6% Convertible preferred stock eliminated date	Sep. 21, 2021
Series B Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)			1,014	1,016
Series B Convertible Preferred Stock [Member] \| 2018 Rights Offering [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)			1,014
Number of preferred stock, shares converted			5,978
Series C Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)			938	938
Series C Convertible Preferred Stock [Member] \| 2018 Rights Offering [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)			938
Number of preferred stock, shares converted			416,889

Stockholders' Equity - Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Warrant exercise price (in dollars per share)		$ 2.25
Warrant liability	$ 1	$ 7
Change in fair value of warrants	$ (6)	$ (2,400)
Series U Warrants [Member]
Class of Stock [Line Items]
Common stock issued (in shares)	3,450,000
Sale of Stock, Price Per Share	$ 5.00
Warrants expected term	5 years
Representative Warrants [Member]
Class of Stock [Line Items]
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]
Class of Stock [Line Items]
Common stock issued (in shares)	7,864,379	2,150,113
Warrants expected term	5 years
Outstanding Warrants [Member]
Class of Stock [Line Items]
Warrant liability		$ 4,500
Change in fair value of warrants		$ 700
Outstanding Warrants [Member] \| Series U Warrants [Member]
Class of Stock [Line Items]
Number of securities called by warrant or right		3,447,500
Class of warrant outstanding	2,141,000
Number of warrant classified as equity	2,138,500
Number of warrants exercised	2,141,000
Common Class A [Member]
Class of Stock [Line Items]
Common stock issued (in shares)	289,000
Common Class B [Member]
Class of Stock [Line Items]
Number of securities called by warrant or right	2,711,000

Stockholders' Equity - Common stock (Details) - USD ($)						9 Months Ended	12 Months Ended
Stockholders' Equity - Common stock (Details) - USD ($)	Feb. 24, 2022	Jan. 14, 2022	Jan. 01, 2022	Sep. 30, 2020	Jun. 16, 2020	Sep. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Oct. 23, 2020
Class of Stock [Line Items]
Sale of common stock, net							$ 18,581,000	$ 3,882,000
Proceeds from sale of common stock							18,675,000	4,007,000
Common Stock [Member]
Class of Stock [Line Items]
Sale of common stock, net							$ 8,000	$ 2,000
Common stock issued (in shares)							7,864,379	2,150,113
2020 Repurchase Agreement [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Sale of common stock, net						$ 25,000,000.0
Common stock issued (in shares)							5,685,186	353,113
Period exercisable from the date of issuance						36 months
Closing price per share					$ 1.05
Proceeds from sale of common stock							$ 12,500,000	$ 700,000
2020 Repurchase Agreement [Member] \| Common Stock [Member] \| Subsequent Event [Member]
Class of Stock [Line Items]
Common stock issued (in shares)			5,665,000
Proceeds from sale of common stock			$ 7,000,000.0
Remaining common stock issued and sold (in shares)			0
2020 Repurchase Agreement [Member] \| Common Stock [Member] \| Commitment Fee [Member]
Class of Stock [Line Items]
Common stock issued (in shares)								180,701
2020 Repurchase Agreement [Member] \| Common Stock [Member] \| Minimum [Member]
Class of Stock [Line Items]
Percentage issuance of common stock					19.99%
2020 Repurchase Agreement [Member] \| Common Stock [Member] \| Minimum [Member] \| Single Regular Purchase [Member]
Class of Stock [Line Items]
Sale of common stock, net				$ 500,000
Common stock issued (in shares)				50,000
2020 Repurchase Agreement [Member] \| Common Stock [Member] \| Maximum [Member]
Class of Stock [Line Items]
Common stock issued (in shares)					23,800,000
2020 Repurchase Agreement [Member] \| Common Stock [Member] \| Maximum [Member] \| Single Regular Purchase [Member]
Class of Stock [Line Items]
Common stock issued (in shares)				100,000
Closing price per share				$ 0.25		$ 0.25
Sales Agreement [Member] \| Common Stock [Member] \| At The Market Offering Program [Member]
Class of Stock [Line Items]
Remaining availability under financing facility									$ 0
Sales Agreement [Member] \| Common Stock [Member] \| Subsequent Event [Member] \| At The Market Offering Program [Member]
Class of Stock [Line Items]
Remaining availability under financing facility		$ 0
Sales Agreement [Member] \| Common Stock [Member] \| Maximum [Member] \| Subsequent Event [Member] \| At The Market Offering Program [Member]
Class of Stock [Line Items]
Proceeds from sale of common stock		$ 5,000,000
2022 Distribution Agreement [Member] \| Common Stock [Member] \| Subsequent Event [Member]
Class of Stock [Line Items]
Common stock issued (in shares)	1,000,000		1,000,000
Proceeds from sale of common stock	$ 900,000		$ 900,000
2020 Distribution Agreement [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Common stock issued (in shares)							2,179,193	1,616,331
Proceeds from sale of common stock							$ 6,300,000	$ 3,200,000
Remaining availability under financing facility							$ 0

Stock-based Compensation - Additional Information (Details) - USD ($)		12 Months Ended
	Jun. 16, 2020	Dec. 31, 2021	Dec. 31, 2020	May 17, 2021	Feb. 06, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares to be issued (in shares)		680,227
Stock Option Activity [Abstract]
Stock option vesting period		1 year
Stock option contractual term		10 years
Stock option vesting percentage		25.00%
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		$ 1,500,000
Weighted average period for recognition of cost		2 years 10 months 24 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)		90,389
2020 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				1,000,000
Securities remaining and available for future issuances (in shares)		640,212
Common stock shares to be issued (in shares)	550,000

Stock-based Compensation - Stock Option Activity (Details)	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Options [Roll Forward]
Balance as of December 31, 2020 (in shares) \| shares	531,336
Granted (in shares) \| shares	680,227
Cancelled/forfeited (in shares) \| shares	(40,673)
Balance as of December 31, 2021 (in shares) \| shares	1,170,890
Vested and expected to vest at December 31, 2021 (in shares) \| shares	378,010
Exercisable at December 31, 2021 \| shares	1,089,944
Weighted Average Exercise Price [Roll Forward]
Balance as of December 31, 2020 (in dollars per share) \| $ / shares	$ 10.01
Granted (in dollars per share) \| $ / shares	2.52
Cancelled/forfeited (in dollars per share) \| $ / shares	16.69
Balance as of December 31, 2021 (in dollars per share) \| $ / shares	5.01
Vested and expected to vest at December 31, 2021 (in dollars per share) \| $ / shares	10.37
Exercisable at December 31, 2021 (in dollars per share) \| $ / shares	$ 5.16
Weighted Average Remaining Contractual Life (years) [Roll Forward]
Balance as of December 31, 2021	9 years
Vested and expected to vest at December 31, 2021	8 years 8 months 12 days
Exercisable at December 31, 2021	9 years

Stock-based Compensation - Weighted-average Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Black-Scholes-Merton option valuation model based on weighted-average assumptions [Abstract]
Expected term	6 years	5 years 9 months 18 days
Risk-free interest rate	1.00%	0.58%
Expected volatility	127.00%	128.60%
Dividends	0.00%	0.00%
Resulting fair value	$ 2.23	$ 1.87

Stock-based Compensation - Summary of Share-Based Compensation Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 606	$ 247
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	75	32
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 531	$ 215

Subsequent Events - Additional Information (Details) - USD ($) $ in Thousands			12 Months Ended
	Feb. 24, 2022	Jan. 01, 2022	Dec. 31, 2021	Dec. 31, 2020
Subsequent Event [Line Items]
Proceeds from sale of common stock			$ 18,675	$ 4,007
Common Stock [Member]
Subsequent Event [Line Items]
Common stock issued (in shares)			7,864,379	2,150,113
Subsequent Event [Member] \| 2020 Purchase Agreement [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Common stock issued (in shares)	5,665,000
Proceeds from sale of common stock	$ 7,000
Subsequent Event [Member] \| 2022 Distribution Agreement [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Common stock issued (in shares)	1,000,000	1,000,000
Proceeds from sale of common stock	$ 900	$ 900