0000950170-23-004099 | 10-K | XBRL Viewer

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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2022	Feb. 17, 2023	Jun. 30, 2022
Cover [Abstract]
Entity Registrant Name	PLUS THERAPEUTICS, INC.
Entity Central Index Key	0001095981
Trading Symbol	PSTV
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 12.1
Entity Common Stock, Shares Outstanding		35,109,885
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2022
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-34375
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0827593
Entity Address, Address Line One	4200 MARATHON BLVD
Entity Address, Address Line Two	SUITE 200
Entity Address, City or Town	AUSTIN
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	78756
City Area Code	737
Local Phone Number	255-7194
Document Annual Report	true
Document Transition Report	false
Auditor Firm ID	243
Auditor Name	BDO USA, LLP
Auditor Location	Austin, Texas
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement for its 2023 Annual Meeting of Stockholders, which will be filed with the United States Securities and Exchange Commission within 120 days of December 31, 2022, are incorporated by reference into Part III of this Annual Report on Form 10-K.

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 18,120	$ 18,400
Other current assets	3,697	1,324
Total current assets	21,817	19,724
Property and equipment, net	1,324	1,477
Operating lease right-use-of assets	248	341
Goodwill	372	372
Intangible assets, net	94	51
Other assets	12	16
Total assets	23,867	21,981
Current liabilities:
Accounts payable and accrued expenses	10,134	4,151
Operating lease liability	110	111
Term loan obligation, current	1,608	1,608
Total current liabilities	11,852	5,870
Noncurrent operating lease liability	141	269
Term loan obligation	3,786	5,005
Deferred grant liability	1,643
Warrant liability		1
Total liabilities	17,422	11,145
Commitments and contingencies (Note 6)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 1,95 shares issued and outstanding as of December 31, 2022 and 2021
Common stock, $0.001 par value; 100,000,000 shares authorized; 33,601,373and 15,510,025 shares issued and outstanding as of December 31, 2022 and 2021, respectively	34	16
Additional paid-in capital	473,596	457,730
Accumulated deficit	(467,185)	(446,910)
Total stockholders’ equity	6,445	10,836
Total liabilities and stockholders’ equity	$ 23,867	$ 21,981

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
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	1,952
Preferred stock, shares outstanding (in shares)	1,952	1,952
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)	33,601,373	15,510,025
Common stock, shares outstanding (in shares)	33,601,373	15,510,025

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Operating expenses:
Research and development	$ 9,698	$ 5,323
In process research and development acquired	0	250
General and administrative	10,238	6,853
Loss on disposal of property and equipment	0	66
Total operating expenses	19,936	12,492
Operating loss	(19,712)	(12,492)
Other income (expense):
Interest income	147	19
Interest expense	(711)	(932)
Change in fair value of liability instruments	1	6
Total other expense	(563)	(907)
Net loss	$ (20,275)	$ (13,399)
Net loss per share, basic	$ (0.77)	$ (1.11)
Net loss per share, diluted	$ (0.77)	$ (1.11)
Basic weighted average shares used in calculating net loss per share attributable to common stockholders	26,255,256	12,089,186
Diluted weighted average shares used in calculating net loss per share attributable to common stockholders	26,255,256	12,089,186
Grant [Member]
Revenue	$ 224

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, 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
Sale of common stock, net	18,581		$ 8	18,573
Sale of common stock, net (in shares)			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 Series B convertible preferred stock into common stock (in shares)		(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
Share-based compensation	606			606
Sale of common stock, net	15,278		$ 18	15,260
Sale of common stock, net (in shares)			18,091,348
Net loss	(20,275)				(20,275)
Balance at Dec. 31, 2022	$ 6,445		$ 34	$ 473,596	$ (467,185)
Balance (in shares) at Dec. 31, 2022		1,952	33,601,373

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Cash flows used in operating activities:
Net loss	$ (20,275)	$ (13,399)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	619	395
Amortization of deferred financing costs and debt discount	389	546
In process research and development acquired	0	250
Change in fair value of liability instruments	(1)	(6)
Loss on disposal of property and equipment	0	66
Share-based compensation expense	606	606
Amortization of operating lease right-of-use assets	93	24
Increases (decreases) in cash caused by changes in operating assets and liabilities:
Other current assets	(2,369)	(496)
Accounts payable and accrued expenses	6,452	1,734
Change in operating lease liabilities	(129)
Other long-term liabilities	1,643	0
Net cash used in operating activities	(12,972)	(10,280)
Cash flows from (used in) investing activities:
Purchases of property and equipment and intangible assets	(509)	(144)
In process research and development acquired	(250)	0
Proceeds from sale of property and equipment	0	62
Net cash used in investing activities	(759)	(82)
Cash flows from financing activities:
Principal payments of long-term obligations	(1,608)	(268)
Payment of finance lease liability	0	(8)
Proceeds from exercise of warrants	0	2,017
Proceeds from sale of common stock	15,059	18,675
Net cash provided by financing activities	13,451	20,416
Net increase (decrease) in cash and cash equivalents	(280)	10,054
Cash and cash equivalents at beginning of period	18,400	8,346
Cash and cash equivalents at end of period	18,120	18,400
Cash paid during period for:
Interest	327	388
Supplemental schedule of non-cash investing and financing activities:
Unpaid offering cost	$ 0	$ 219

Organization and Operations

12 Months Ended

Dec. 31, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

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.

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 $20.3 million for the year ended December 31, 2022, and as of December 31, 2022, the Company had an accumulated deficit of $467.2 million and cash and cash equivalents of $18.1 million. Additionally, the Company used net cash of $13.0 million to fund its operating activities for the year ended December 31, 2022. The Company expects that its research and development expenditures will increase in absolute dollars in 2023 and beyond.

As disclosed in more detail in Note 12, the Company has entered into various financing agreements 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 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 in the future, the Company may eventually 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.

On May 24, 2022, the Company received notice from The Nasdaq Stock Market LLC (“Nasdaq”) that, because the closing bid price for the Company’s common stock had fallen below $1.00 per share for 30 consecutive business days, the Company no longer complied with the minimum bid price requirement pursuant to Nasdaq Listing Rule 5550(a)(2) (the “Minimum Bid Requirement”).

Nasdaq’s notice had no immediate effect on the listing or trading of the Company’s common stock. On November 22, 2022, the Company received a second letter from Nasdaq advising that the Company had been granted an additional 180 calendar days, or to May 22, 2023, to regain compliance with the Minimum Bid Requirement, in accordance with Nasdaq Listing Rule 5810(c)(3)(A).

The Company intends to continue to actively monitor the closing bid price of its common stock and will evaluate available options to regain compliance with the Minimum Bid Requirement. Specifically, the Company has confirmed to Nasdaq that, if necessary, it will implement a reverse stock split of its outstanding common stock (if approved by the Company’s stockholders) to attempt to regain compliance. If the Company does not regain compliance within the additional compliance period, Nasdaq will provide notice that the Company’s common stock will be subject to delisting. The Company would then be entitled to appeal that determination to a Nasdaq hearings panel. There can be no assurance that the Company will regain compliance with the Minimum Bid Requirement during the 180-day additional compliance period or maintain compliance with the other Nasdaq listing requirements.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Use of Estimates

The preparation of 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 grant revenue recognition, reviewing assets for impairment, and determining the assumptions used in measuring share-based compensation expense.

Actual results could differ from these estimates. Management’s estimates and assumptions are reviewed regularly, and the effects of revisions are reflected in the 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, 2022 and 2021. 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, other current assets, accounts payable, accrued expenses, other liabilities and long-term debt. The carrying values of cash equivalents, 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 currently 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, 2022 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 statements of operations and comprehensive loss.

Grant Receivable and Revenue Recognition

In applying the provisions of Accounting Standards Codification ("ASC") Topic 606, Revenue from Contracts with Customers (“ASC 606”), the Company has determined that government grants are out of the scope of ASC 606 because the funding entities do not meet the definition of a “customer”, as defined by ASC 606, as there is not considered to be a transfer of control of goods or services. With respect to the grant, the Company determines if it has a collaboration in accordance with ASC Topic 808, Collaborative Arrangements (“ASC 808”). For grants outside the scope of ASC 808, the Company applies ASC 606 or International Accounting Standards No. 20, Accounting for Government Grants and Disclosure of Government Assistance, by analogy, and revenue is recognized when the Company incurs expenses related to the grant for the amount the Company is entitled to under the provisions of the contract.

The Company also considers the guidance in ASC Topic 730, Research and Development (“ASC 730”), which requires an assessment, at the inception of the grant, of whether the agreement is a liability. If the Company is obligated to repay funds received regardless of the outcome of the related research and development activities, then the Company is required to estimate and recognize that liability. Alternatively, if the Company is not required to repay the funds, then payments received are recorded as revenue or contra-expense as the expenses are incurred.

Deferred grant liability represents grant funds received or receivable for which the allowable expenses have not yet been incurred as of the balance sheet date.

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.

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.

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, 2022 and 2021, 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, 2022 and 2021, the Company is managed as a single operating segment, and therefore reports its 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, 2022 and 2021, 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 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 will adopt the new guidance for the quarter beginning on January 1, 2023, and it does not expect that adoption of this standard will have a material impact on its financial statements and related disclosures.

Fair Value Measurements

12 Months Ended

Dec. 31, 2022

Fair Value Disclosures [Abstract]

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. The Company follows

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.

Certain warrants issued in an underwritten public offering in September 2019 (“Series U Warrants”) are classified as liability instruments. The Company estimated the fair value of the Series U Warrants with the Black Scholes model. Because some of the inputs to the Company’s 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.

Liability-classified Series U Warrants are marked to market as of each balance sheet date until they are exercised or upon expiration, with the changes in fair value recorded as non-operating income or loss in the statements of operations. As of December 31, 2022 and 2021, the fair value of the Series U Warrants was immaterial, and the change in the fair value of liability classified Series U Warrants during year ended December 31, 2022 and 2021 was immaterial.

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, 2022

Earnings Per Share [Abstract]

Loss per Share

4. 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,
	2022		2021
Outstanding stock options		1,175,016		1,170,890
Preferred stock		422,867		422,867
Outstanding warrants		2,141,378		2,141,378
Total		3,739,261		3,735,135

Composition of Certain Financial Statement Captions

12 Months Ended

Dec. 31, 2022

Composition Of Certain Financial Statement Captions [Abstract]

Composition of Certain Financial Statement Captions

5. Composition of Certain Financial Statement Captions

Other Current Assets

As of December 31, 2022 and 2021, other current assets were comprised of the following (in thousands):


	December 31,
	2022		2021
Prepaid services	$	2,999	$	622
Prepaid insurance		698		695
Other		—		7
	$	3,697	$	1,324

Property and Equipment, net

As of December 31, 2022 and 2021, property and equipment, net, were comprised of the following (in thousands):


	December 31,
	2022			2021
Office and computer equipment	$	1,474		$	1,231
Leasehold improvements		1,810			1,661
		3,284			2,892
Less accumulated depreciation		(1,960	)		(1,415	)
	$	1,324		$	1,477

Depreciation expense totaled $0.5 million and $0.4 million for the year ended December 31, 2022 and 2021, respectively.

Intangible Assets, net

As of December 31, 2022, intangible assets included the net book value of costs incurred for software upgrades. Amortization

expenses totaled $0.1 million and $32 thousand for the year ended December 31, 2022 and 2021, respectively.

Accounts Payable and Accrued Expenses

As of December 31, 2022 and 2021, accounts payable and accrued expenses were comprised of the following (in thousands):


	December 31,
	2022		2021
Accounts payable	$	8,364	$	2,611
Accrued payroll and bonus		989		781
Accrued professional fees		147		189
Accrued vacation and compensation		325		252
Accrued R&D studies		309		196
Other current liabilities		—		122
	$	10,134	$	4,151

Commitments and Contingencies

12 Months Ended

Dec. 31, 2022

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

6. 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 finance leases are recorded within property and equipment, net in the balance sheets. Leases with an initial term of 12 months or less are not recorded on the balance sheets. Instead, the Company recognizes lease expense for these leases on a straight-line basis over the lease term in the statements of operations.

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 and certain office space in Charlottesville, Virginia (the “Charlottesville Lease”). The Charlottesville Lease has a term of 12 months and the Company has the ability to renew for three additional one-year periods. The Charlottesville Lease is currently set to expire on March 31, 2023. 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 of April 1, 2021. In addition, the Company has entered into leases for certain equipment under various operating and finance leases. 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, 2022 or 2021. The Company’s existing operating 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 Company’s operating lease liabilities and corresponding right-of-use assets are included in the balance sheets. As of December 31, 2022, the weighted average discount rate used to measure operating lease liabilities and the operating leases remaining term were 9% and 2.03 years, respectively.

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


	Year Ended December 31,
		2022		2021
Lease expense:
Operating lease expense	$	159	$	211
Finance lease expense:
Depreciation of right-of-use assets		—		7
Total lease expense	$	159	$	218

Cash payment information:
Operating cash used for operating leases	$	159	$	206
Financing cash used for financing leases		—		8
Total cash paid for amounts included in the measurement of lease liabilities	$	159	$	214

Total rent expenses for each of the years ended December 31, 2022 and 2021 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 finance leases at December 31, 2022 are as follows (in thousands):



	Operating Leases
2023		137
2024		113
2025		18
Total minimum lease payments	$	268
Less: amount representing interest		(17	)
Present value of obligations under leases		251
Less: current portion		(110	)
Noncurrent lease obligations	$	141

Services Agreement and Sales Order with Medidata

On March 31, 2022, the Company and Medidata Solutions, Inc. (“Medidata”) entered into a Sales Order (the “Sales Order”), pursuant to which Medidata will build a Synthetic Control Arm® (SCA) platform that facilitates the use of historical clinical data to incorporate into the Company’s Phase 2 clinical trial of rhenium (186Re) obisbemeda in recurrent glioblastoma (“GBM”). The Sales Order is governed under the terms of a services agreement (the “Services Agreement”), dated November 5, 2021. The Sales Order had a term of six (6) months, and work under the Sales Order has been completed. Costs related to the Sales Order of $1.5 million were expensed in the statement of operations for the year ended December 31, 2022.

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 rhenium (186Re) obisbemeda-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, 2022, 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 alleged 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 Asset and Equity Purchase Agreement, dated March 29, 2019, between the Company and Lorem (the “Lorem Agreement”). Lorem also claimed 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 claimed entitlement to at least $6,000,000 in compensatory damages and operational costs and expenses (collectively, the “Lorem Claim”). On December 9, 2022, the Company entered into a settlement agreement (the “Settlement Agreement”) with Lorem to settle the Lorem Claim. Under the terms of the Settlement Agreement, the Company made a payment to Lorem, and Lorem moved to dismiss the lawsuit with prejudice. The Settlement Agreement released us from all claims made by Lorem. The parties to the Settlement Agreement recognized that it did not constitute an admission of liability, wrongdoing, or any matter of fact or law. The Settlement was conditioned on the customary terms contained in the Settlement Agreement and was approved by the Court and the case was dismissed on January 17, 2023. As of December 31, 2022, the Company accrued the settlement amount, as well as the accounts that the Company has confirmed to be recoverable under its insurance claims on the matter. The net amount of $1.4 million that was not recoverable under the Company's insurance has been reflected as an expense in the year ended December 31, 2022. The full settlement amount was paid in January 2023. All legal costs related to the Lorem Claim were expensed as incurred.

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.

License Agreements

12 Months Ended

Dec. 31, 2022

License Agreement [Abstract]

License Agreements

7. 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 was required to make an upfront payment, 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 of $0.3 million was paid in cash in January 2022.

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.

The transaction terms included an upfront payment of $0.4 million in cash and $0.3 million in the Company's voting stock. The transaction terms also included success-based milestone and royalty payments contingent on key clinical, regulatory and sales milestones, as well as the requirement to pay 15% of any non-dilutive monetary awards or grants received from external agencies

to support product development of the nanoliposome encapsulated BMEDA-chelated radioisotope, which includes grants from the Cancer Prevention & Research Institute of Texas ("CPRIT"). As of December 31, 2022, the Company accrued $0.3 million of payments due to NanoTx as a result of the CPRIT grant received (Note 9).

Term Loan Obligations

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

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 was 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 their respective fair value was recorded as a discount to the debt.

The Term Loan 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, 2022, there was $2.4 million principal amount outstanding under the Term Loan, excluding the $3.2 million final payment fee, and the Company was in compliance with all of the debt covenants under the Loan and Security Agreement.

The Company’s interest expense for the years ended December 31, 2022 and 2021 was $0.7 million and $0.9 million, respectively. Interest expense is calculated using the effective interest method; therefore it is inclusive of non-cash amortization in the amount of $0.4 million and $0.5 million for the year ended December 31, 2022 and 2021, respectively, related to the amortization of the debt discount, deferred financing costs, and accretion of final payment.

The Loan and Security Agreement 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, 2022, 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, 2022 and 2021 are presented in the following table (in thousands):


Year ended December 31, 2022
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	$	2,412


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

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

** Monthly payment reflects principal and interest

As of December 31, 2022, the future contractual principal and final fee payments on all of our debt obligations are as follows (as thousands):


Years Ending December 31,
2023	$	1,608
2024		3,996
Total	$	5,604


Reconciliation of Face Value to Book Value as of December 31, 2022
Total debt obligations, including final payment fee (Face Value)	$	5,604
Less: Debt discount		(210	)
Total obligation		5,394
Less: Current portion		(1,608	)
Term loan obligation -- noncurrent	$	3,786

- 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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-URI https://asc.fasb.org/topic&trid=2208564

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

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+ Details

Grant Revenue

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

Grant Revenue

9. Grant Revenue

On September 19, 2022, the Company entered into the CPRIT Contract, effective as of August 31, 2022, with CPRIT, pursuant to which CPRIT will provide the Company a grant of up to $17.6 million (the “CPRIT Grant”) over a three-year period to fund the continued development of rhenium (186Re) obisbemeda for the treatment of patients with leptomeningeal metastases (“LM”). The CPRIT Grant is subject to customary CPRIT funding conditions, including, but not limited to, a matching fund requirement (one dollar for every two dollars awarded by CPRIT), revenue sharing obligations upon commercialization of rhenium (186Re) obisbemeda based on specific dollar thresholds and tiered low single digit royalty rates until CPRIT receives the aggregate amount of 400% of the proceeds awarded under the CPRIT Grant, and certain reporting requirements.

The CPRIT Contract will terminate on August 30, 2025, unless terminated earlier by (a) the mutual written consent of all parties to the CPRIT Contract, (b) CPRIT for an event of default by the Company, (c) CPRIT, if the funds allocated to the CPRIT Grant become legally unavailable during the term of the CPRIT Contract and CPRIT is unable to obtain additional funds for such purposes, and (d) the Company for convenience. CPRIT may require the Company to repay some or all of the disbursed CPRIT Grant proceeds (with interest not to exceed 5% annually) in the event of the early termination of the CPRIT Contract by CPRIT for an event of default by the Company or by the Company for convenience.

The Company will retain ownership over any intellectual property developed under the contract ("Project Result"). With respect to non-commercial use of any Project Result, the Company agreed to grant to CPRIT a nonexclusive, irrevocable, royalty-free, perpetual, worldwide license with right to sublicense any necessary additional intellectual property rights to exploit all Project Results by CPRIT, other governmental entities and agencies of the State of Texas, and private or independent institutions of higher education located in Texas, for education, research and other non-commercial purposes.

The Company determined that the CPRIT Contract is not in the scope of ASC 808 or ASC 606. Applying ASC 606 by analogy, the Company recognizes proceeds received under the CPRIT Contract as grant revenue on the statement of operations when related costs are incurred. The Company recognized $0.2 million in grant revenue from the CPRIT Contract during the year ended December 31, 2022.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Income Taxes

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Income Taxes

10. Income Taxes

Pursuant to the Internal Revenue Code (“IRC”) of 1986, as amended, specifically IRC §382 ("Section 382") and IRC §383, the Company’s ability to use net operating loss ("NOLs") and R&D tax credit carry forwards (“tax attribute carry forwards”) to offset future taxable income is limited if the Company experiences a cumulative change in ownership of more than 50% within a three-year testing period. In preparation of the financial statements as of and for the year ended December 31, 2022, the Company performed an ownership change analysis and concluded that it was probable that an ownership change within the meaning of IRC §382 occurred prior to December 31, 2020.

As a result, the Company has determined that approximately $346.8 million for federal NOL carryforwards and $173.0 million for state NOL carryforwards were subject to limitation. Consequently, approximately $84.9 million of deferred tax assets related to NOL carryforwards were eliminated. In addition, deferred tax assets related to federal and state research and development credits of approximately $6.0 million and $5.5 million were eliminated, resulting in a total reduction of deferred tax assets of $8.4 million, which was completely offset by a corresponding adjustment to the Company's valuation allowance. The deferred tax assets relating to net operating loss carryforwards and income tax credit carryforwards and the related valuation allowance as

of December 31, 2021 reflected in the table below have been adjusted to give effect to this. These revisions had no impact on the Company’s balance sheet, statement of operations or statement of cash flows.

The Company's use of federal and state NOLs and research credits could be limited further by the provisions of Section 382 depending upon the timing and amount of additional equity securities that the Company has issued or will issue. State NOL carryforwards may be similarly limited. If a change in ownership were to have occurred, NOL and tax credits carryforwards could be eliminated or restricted. If eliminated, the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance. Due to the existence of the valuation allowance, limitations created by ownership changes, if any, will not impact the Company's effective tax rate.

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, 2022 and 2021, 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, 2022 and 2021, respectively, is as follows:


	2022			2021
Income tax expense (benefit) at federal statutory rate		(21.0	)%		(21.0	)%
Change in valuation allowance		22.5	%		(699.5	)%
Income tax expense (benefit) at state statutory rate		(0.2	)%		(0.6	)%
Share based compensation		0.9	%		0.7	%
NOLs expiring and adjustments to NOL		0.5	%		720.7	%
Research credit		(2.5	)%		(0.8	)%
Return to provision		(0.1	)%		0.5	%
Change in state rate		(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, 2022 and 2021 are as follows (in thousands):


	2022			2021
Deferred tax assets:
Accrued expenses	$	262		$	41
Share based compensation		107			164
Net operating loss carryforwards		12,605			10,404
Income tax credit carryforwards		956			447
Property and equipment, principally due to differences in depreciation		89			19
Intangible assets		2,073			451
Other, net		53			82
		16,145			11,608
Valuation allowance		(16,092	)		(11,534	)
Total deferred tax assets, net of allowance		53			74
Deferred tax liabilities:
Other		(53	)		(74	)
Total deferred tax liability		(53	)		(74	)
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 $16.1 million as of December 31, 2022 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 $4.6 million during the year ended December 31, 2022.

At December 31, 2022, the Company had federal and state tax loss carry forwards of approximately $59.6 million, and $1.8 million, respectively. The federal net operating loss carry forwards begin to expire in 2037, if unused. The state net operating loss carries over indefinitely. The federal net operating loss carryover includes $56.2 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, 2022, the Company had federal tax credit carry forwards of approximately $1.2 million, before reduction for uncertain tax positions. The federal credits will begin to expire in 2039, if unused.

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, 2022 and 2021.

Following is a tabular reconciliation of the unrecognized tax benefits activity during the years ended December 31, 2022 and 2021 (in thousands):


	2022			2021
Unrecognized Tax Benefits – Beginning	$	81		$	2,223
Gross decreases – tax positions in prior period		(1	)		(2,211	)
Gross increase – current-period tax positions		129			69
Unrecognized Tax Benefits – Ending	$	209		$	81

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 for the year ended December 31, 2022.

The Company files income tax returns with the United States and various state jurisdictions. To its knowledge, the Company is currently not under examination by the Internal Revenue Service or any other taxing authority.

With few exceptions, the Company’s tax years prior to 2019 are no longer open to examination by the taxing authority. While not open to examination, the tax attributes generated in tax years 2017 and forward remain subject to adjustment by the taxing authorities if utilized in tax years which are still open to examination.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Employee Benefit Plan

12 Months Ended

Dec. 31, 2022

Retirement Benefits [Abstract]

Employee Benefit Plan

11. Employee Benefit Plan

The Company implemented a 401(k) retirement savings and profit sharing plan (the “Plan”) effective January 1, 1999. During 2022, the Company commenced safe harbor matching contribution for up to 4% of eligible employee contributions. Total matching contribution under the Plan amounted to approximately $100,000 and $40,000 for the year ended December 31, 2022 and 2021, respectively.

Stockholders' Equity

12 Months Ended

Dec. 31, 2022

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 issued prior to September 21, 2021. There were 1,014 shares of Series B Convertible Preferred Stock and 938 shares of Series C Preferred Stock outstanding as of each of December 31, 2022 and 2021, respectively.

As of December 31, 2022, 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 five years from the issuance date, in the form of Series U Warrants (the “Representative Warrants”).

As of December 31, 2022, there were 2,141,000 outstanding Series U Warrants which can be exercised into an aggregate of 2,141,000 shares of common stock.

Common Stock

Lincoln Park Purchase Agreements

On August 2, 2022, the Company entered into a purchase agreement (the “2022 Purchase Agreement”) and registration rights agreement pursuant to which Lincoln Park committed to purchase up to $50.0 million of the Company’s common stock. Under the terms and subject to the conditions of the 2022 Purchase Agreement, the Company has the right, but not the obligation, to sell to Lincoln Park, and Lincoln Park is obligated to purchase up to $50.0 million of the Company’s common stock. Such sales of common stock by the Company are subject to certain limitations, and can occur from time to time, at the Company’s sole discretion, over the 36-month period commencing on August 17, 2022, subject to the satisfaction of certain conditions. Lincoln Park has no right to require the Company to sell any shares of common stock to Lincoln Park, but Lincoln Park is obligated to make purchases as the Company directs, subject to certain conditions.

On May 16, 2022, the Company received stockholder approval for purposes of the Nasdaq listing rules to permit issuances of up to 57.5 million shares of the Company’s common stock (including the issuance of more than 19.99% of the Company’s common stock) to Lincoln Park, and it was pursuant to that approval that the Company entered into the 2022 Purchase Agreement.

Upon execution of the 2022 Purchase Agreement, the Company paid $0.1 million in cash as the initial commitment fee, and issued 492,698 shares as the initial commitment shares, to Lincoln Park as consideration for its irrevocable commitment to purchase shares of the Company's common stock at its direction under the Purchase Agreement. The Company has agreed to pay an additional commitment fee, which it may elect to pay in cash and/or shares of its common stock, upon receipt of $25.0 million aggregate gross proceeds from sales of common stock to Lincoln Park under the 2022 Purchase Agreement.

On August 17, 2022, a registration statement was declared effective to cover the resale of up to 9,500,000 shares of the Company's common stock comprised of (i) the 492,698 initial commitment shares, and (ii) up to 9,007,302 that the Company has reserved for issuance and sale to Lincoln Park under the Purchase Agreement from time to time from and after the date of this prospectus. The Company cannot sell more shares under the 2022 Purchase Agreement without registering additional shares.

Actual sales of shares of common stock to Lincoln Park under the 2022 Purchase Agreement depend on a variety of factors to be determined by the Company from time to time, including, among others, market conditions, the trading price of the common stock and determinations by the Company as to the appropriate sources of funding for the Company and its operations. The net proceeds under the 2022 Purchase Agreement to the Company depend on the frequency and prices at which the Company sells shares of its stock to Lincoln Park.

During the period from August 17, 2022 to December 31, 2022, the Company issued 4,000,000 shares under the 2022 Purchase Agreement for net proceeds of approximately $3.2 million. From January 1, 2023 to the date of filing of these financial statements, the Company did not issue any shares under the 2022 Purchase Agreement.

On September 30, 2020, the Company entered into a purchase agreement (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 could 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.

On June 16, 2020, the Company received stockholder approval for purposes of the Nasdaq listing rules to permit issuances of up to 23.8 million shares of the Company’s common stock (including the issuance of more than 19.99% of the Company’s common stock) to Lincoln Park, and it was pursuant to that approval that the Company entered into the 2020 Purchase Agreement.

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 directs, subject to certain conditions.

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. During the year issued December 31, 2022, the Company issued 5,665,000 shares of its common stock under the 2020 Purchase Agreement for net proceeds of approximately $7.0 million. The Company no longer has any additional shares of common stock registered to sell under the 2020 Purchase Agreement.

At-the-market Issuances

On September 9, 2022, the Company entered into an Equity Distribution Agreement (the “September 2022 Distribution Agreement”) with Canaccord Genuity LLC ("Canaccord”), pursuant to which the Company may issue and sell, from time to time, shares of its common stock having an aggregate offering price of up to $5,000,000, depending on market demand, with Canaccord acting as an agent for sales. Sales of the Company's common stock may be made by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415(a)(4) of the Securities Act of 1933, as amended (the “Securities Act”), including, without limitation, sales made directly on or through the NASDAQ Capital Market. Canaccord will use its commercially reasonable efforts to sell common stock requested by the Company to be sold on its behalf, consistent with Canaccord's normal trading and sales practices, under the terms and subject to the conditions set forth in the September 2022 Distribution Agreement. The Company has no obligation to sell any of its common stock. The Company may instruct Canaccord not to sell any common stock if the sales cannot be effected at or above the price designated by the Company from time to time and the Company may at any time suspend sales pursuant to the September 2022 Distribution Agreement. During the period from September 9, 2022 to December 31, 2022, the Company issued 1,031,371 shares under the September 2022 Distribution Agreement for net proceeds of approximately $0.6 million. From January1, 2023 to the date of filing of this Form 10-K, the Company issued 1,812,785 shares under the September 2022 Distribution Agreement for net proceeds of approximately $0.7 million.

The Company is obligated to pay Canaccord a commission of up to 3.0% of the gross proceeds from the sale of its common stock under the September 2022 Distribution Agreement. The Company has also agreed to reimburse Canaccord for its reasonable documented out-of-pocket expenses, including fees and disbursements of its counsel, in the amount of $50,000. In addition, the Company has agreed to provide customary indemnification rights to Canaccord.

The Offering will terminate upon the earlier of (1) the issuance and sale of all shares of the Company’s common stock subject to the September 2022 Distribution Agreement, or (2) the termination of the Distribution Agreement as permitted therein, including by either party at any time without liability of any party.

On January 14, 2022, the Company entered into an Equity Distribution Agreement (the “January 2022 Distribution Agreement”) with Canaccord, pursuant to which the Company could issue and sell, from time to time, shares of its common stock having an aggregate offering price of up to $5,000,000 shares, with Canaccord acting as an agent for sales. The Company had no obligation to sell any of the Company’s shares and it could instruct Canaccord not to sell any shares if the sales could not be effected at or above the price designated by the Company from time to time and the Company could at any time suspend sales pursuant to the January 2022 Distribution Agreement. During the year ended December 31, 2022, the Company issued 6,902,279 shares under the January 2022 Distribution Agreement for net proceeds of approximately $4.8 million. The January 2022 Distribution Agreement has been terminated after all available registered shares were fully utilized.

Share Repurchase Program

On August 15, 2022, the Company announced that its Board of Directors has approved a share repurchase program pursuant to which the Company is authorized to repurchase up to $2.0 million of the Company’s outstanding common stock. The timing and amount of any shares repurchased will be determined based on the Company’s evaluation of market conditions and other factors, including consent of Oxford. Repurchases may be made from time to time on the open market over the course of 12 months. The Company is not obligated to acquire any shares and the program may be discontinued or suspended at any time. Through the date of filing of this Form 10-K, the Company has not repurchased any of its common stock under this share repurchase program.

- 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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 505
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+ Details

Share-based Compensation

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Share-based Compensation

13.

Share-based Compensation

Under the Company’s 2015 New Employee Incentive Plan (the “2015 Plan”), awards may only be granted 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, 2022, there were 90,389 shares of common stock remaining and available for future issuances under the 2015 Plan.

The Company’s 2020 Stock Incentive Plan (the “2020 Plan”), which replaced the Company’s 2014 Equity Incentive 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 to directors, officers, employees and consultants of the Company. The 2020 Plan, as amended, provides for the issuance of up to 3,550,000 shares of common stock, plus the number of shares available for issuance is increased to the extent that awards granted under the 2020 Plan and the Company’s 2014 Equity Incentive Plan are forfeited or expire (except as otherwise provided in the 2020 Plan). As of December 31, 2022, there were 2,635,717 shares remaining and available for future issuances under the 2020 Plan.

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

A summary of activity for the year ended December 31, 2022 is as follows:


	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Balance as of December 31, 2021		1,170,890		$	5.01		9.00
Granted		13,000		$	0.53
Cancelled/forfeited		(8,874	)	$	60.08
Balance as of December 31, 2022		1,175,016		$	4.54		8.00	$	-
Vested and expected to vest at December 31, 2022		1,135,664		$	4.57		8.00	$	-
Exercisable at December 31, 2022		671,892		$	6.11		7.84	$	-

The Company settles exercises of stock options with newly issued shares of its common stock. There were no stock options exercised in 2022 or 2021.

The fair value of each option awarded during the years ended December 31, 2022 and 2021 was estimated on the date of grant using the Black-Scholes-Merton option valuation model based on the following weighted-average assumptions:


	December 31, 2022			December 31, 2021
Expected term	6.0 years			6.0 years
Risk-free interest rate		2.83	%		1.00	%
Expected volatility		123.4	%		127.0	%
Dividends		0	%		0	%
Resulting fair value	$	0.47		$	2.23

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, the Company uses 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, 2022 and 2021 in the statement of operations and comprehensive loss:


	Years ended December 31,
	2022		2021
Research and development	$	87	$	75
General and administrative		519		531
Total share-based compensation	$	606	$	606

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 $0.9 million, which is expected to be recognized as a result of vesting under service conditions over a weighted average period of 2.2 years.

Financial Statement Schedules

12 Months Ended

Dec. 31, 2021

SEC Schedule, 12-09, 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, 2022
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of 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 grant revenue recognition, reviewing assets for impairment, and determining the assumptions used in measuring share-based compensation expense. Actual results could differ from these estimates. Management’s estimates and assumptions are reviewed regularly, and the effects of revisions are reflected in the 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, 2022 and 2021. 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, other current assets, accounts payable, accrued expenses, other liabilities and long-term debt. The carrying values of cash equivalents, 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 currently 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, 2022 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 statements of operations and comprehensive loss.
Grant Receivable and Revenue Recognition	Grant Receivable and Revenue Recognition In applying the provisions of Accounting Standards Codification ("ASC") Topic 606, Revenue from Contracts with Customers (“ASC 606”), the Company has determined that government grants are out of the scope of ASC 606 because the funding entities do not meet the definition of a “customer”, as defined by ASC 606, as there is not considered to be a transfer of control of goods or services. With respect to the grant, the Company determines if it has a collaboration in accordance with ASC Topic 808, Collaborative Arrangements (“ASC 808”). For grants outside the scope of ASC 808, the Company applies ASC 606 or International Accounting Standards No. 20, Accounting for Government Grants and Disclosure of Government Assistance, by analogy, and revenue is recognized when the Company incurs expenses related to the grant for the amount the Company is entitled to under the provisions of the contract. The Company also considers the guidance in ASC Topic 730, Research and Development (“ASC 730”), which requires an assessment, at the inception of the grant, of whether the agreement is a liability. If the Company is obligated to repay funds received regardless of the outcome of the related research and development activities, then the Company is required to estimate and recognize that liability. Alternatively, if the Company is not required to repay the funds, then payments received are recorded as revenue or contra-expense as the expenses are incurred. Deferred grant liability represents grant funds received or receivable for which the allowable expenses have not yet been incurred as of the balance sheet date.
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.
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.
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, 2022 and 2021, 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, 2022 and 2021, the Company is managed as a single operating segment, and therefore reports its 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, 2022 and 2021, 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 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 will adopt the new guidance for the quarter beginning on January 1, 2023, and it does not expect that adoption of this standard will have a material impact on its financial statements and related disclosures.

Loss per Share (Tables)

12 Months Ended

Dec. 31, 2022

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,
	2022		2021
Outstanding stock options		1,175,016		1,170,890
Preferred stock		422,867		422,867
Outstanding warrants		2,141,378		2,141,378
Total		3,739,261		3,735,135

Composition of Certain Financial Statement Captions (Tables)

12 Months Ended

Dec. 31, 2022

Composition Of Certain Financial Statement Captions [Abstract]

Other Current Assets

As of December 31, 2022 and 2021, other current assets were comprised of the following (in thousands):


	December 31,
	2022		2021
Prepaid services	$	2,999	$	622
Prepaid insurance		698		695
Other		—		7
	$	3,697	$	1,324

Property and Equipment, net

As of December 31, 2022 and 2021, property and equipment, net, were comprised of the following (in thousands):


	December 31,
	2022			2021
Office and computer equipment	$	1,474		$	1,231
Leasehold improvements		1,810			1,661
		3,284			2,892
Less accumulated depreciation		(1,960	)		(1,415	)
	$	1,324		$	1,477

Accounts Payable and Accrued Expenses

As of December 31, 2022 and 2021, accounts payable and accrued expenses were comprised of the following (in thousands):


	December 31,
	2022		2021
Accounts payable	$	8,364	$	2,611
Accrued payroll and bonus		989		781
Accrued professional fees		147		189
Accrued vacation and compensation		325		252
Accrued R&D studies		309		196
Other current liabilities		—		122
	$	10,134	$	4,151

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2022

Commitments and Contingencies Disclosure [Abstract]

Summary of Lease Costs

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


	Year Ended December 31,
		2022		2021
Lease expense:
Operating lease expense	$	159	$	211
Finance lease expense:
Depreciation of right-of-use assets		—		7
Total lease expense	$	159	$	218

Cash payment information:
Operating cash used for operating leases	$	159	$	206
Financing cash used for financing leases		—		8
Total cash paid for amounts included in the measurement of lease liabilities	$	159	$	214

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

The Company’s future minimum annual lease payments under operating and finance leases at December 31, 2022 are as follows (in thousands):



	Operating Leases
2023		137
2024		113
2025		18
Total minimum lease payments	$	268
Less: amount representing interest		(17	)
Present value of obligations under leases		251
Less: current portion		(110	)
Noncurrent lease obligations	$	141

Term Loan Obligations (Tables)

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

Term Loan Outstanding

Additional details relating to the outstanding Term Loan as of December 31, 2022 and 2021 are presented in the following table (in thousands):


Year ended December 31, 2022
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	$	2,412


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

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

** Monthly payment reflects principal and interest

Future Payments under Obligation

As of December 31, 2022, the future contractual principal and final fee payments on all of our debt obligations are as follows (as thousands):


Years Ending December 31,
2023	$	1,608
2024		3,996
Total	$	5,604

Face Value to Book Value Reconciliation


Reconciliation of Face Value to Book Value as of December 31, 2022
Total debt obligations, including final payment fee (Face Value)	$	5,604
Less: Debt discount		(210	)
Total obligation		5,394
Less: Current portion		(1,608	)
Term loan obligation -- noncurrent	$	3,786

- 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, 2022

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, 2022 and 2021, respectively, is as follows:


	2022			2021
Income tax expense (benefit) at federal statutory rate		(21.0	)%		(21.0	)%
Change in valuation allowance		22.5	%		(699.5	)%
Income tax expense (benefit) at state statutory rate		(0.2	)%		(0.6	)%
Share based compensation		0.9	%		0.7	%
NOLs expiring and adjustments to NOL		0.5	%		720.7	%
Research credit		(2.5	)%		(0.8	)%
Return to provision		(0.1	)%		0.5	%
Change in state rate		(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, 2022 and 2021 are as follows (in thousands):


	2022			2021
Deferred tax assets:
Accrued expenses	$	262		$	41
Share based compensation		107			164
Net operating loss carryforwards		12,605			10,404
Income tax credit carryforwards		956			447
Property and equipment, principally due to differences in depreciation		89			19
Intangible assets		2,073			451
Other, net		53			82
		16,145			11,608
Valuation allowance		(16,092	)		(11,534	)
Total deferred tax assets, net of allowance		53			74
Deferred tax liabilities:
Other		(53	)		(74	)
Total deferred tax liability		(53	)		(74	)
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, 2022 and 2021 (in thousands):


	2022			2021
Unrecognized Tax Benefits – Beginning	$	81		$	2,223
Gross decreases – tax positions in prior period		(1	)		(2,211	)
Gross increase – current-period tax positions		129			69
Unrecognized Tax Benefits – Ending	$	209		$	81

Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Stock Option Activity

A summary of activity for the year ended December 31, 2022 is as follows:


	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Balance as of December 31, 2021		1,170,890		$	5.01		9.00
Granted		13,000		$	0.53
Cancelled/forfeited		(8,874	)	$	60.08
Balance as of December 31, 2022		1,175,016		$	4.54		8.00	$	-
Vested and expected to vest at December 31, 2022		1,135,664		$	4.57		8.00	$	-
Exercisable at December 31, 2022		671,892		$	6.11		7.84	$	-

Weighted-average Assumptions


	December 31, 2022			December 31, 2021
Expected term	6.0 years			6.0 years
Risk-free interest rate		2.83	%		1.00	%
Expected volatility		123.4	%		127.0	%
Dividends		0	%		0	%
Resulting fair value	$	0.47		$	2.23

Summary of Share-Based Compensation Recognized

The following table summarizes share-based compensation recognized during the years ended December 31, 2022 and 2021 in the statement of operations and comprehensive loss:


	Years ended December 31,
	2022		2021
Research and development	$	87	$	75
General and administrative		519		531
Total share-based compensation	$	606	$	606

Organization and Operations - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	May 04, 2022	Dec. 31, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss		$ (20,275)	$ (13,399)
Accumulated deficit		(467,185)	(446,910)
Cash and cash equivalents		18,120	18,400
Net cash used in operating activities		$ (12,972)	$ (10,280)
Closing bid price for common stock had fallen below	$ 1.00
Consecutive business days	30 days
Period for regain compliance		180 days

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) Segment ReportableUnit	Dec. 31, 2021 USD ($) 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
Interest or penalties related to income tax matters	$ 0	$ 0
Number of operating segment \| Segment	1	1
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)	12 Months Ended
	Dec. 31, 2022
Series U Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants issued, underwritten public offering, period	2019-09

Loss per Share - Schedule of Antidilutive Securities Excluded from Diluted Income (Loss) per Share (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
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)	3,739,261	3,735,135
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)	1,175,016	1,170,890
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	422,867
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	2,141,378

Composition of Certain Financial Statement Captions - Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Other Current Assets [Abstract]
Prepaid services	$ 2,999	$ 622
Prepaid insurance	698	695
Other		7
Total other current assets	$ 3,697	$ 1,324

Composition of Certain Financial Statement Captions - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property and Equipment, net [Abstract]
Office and computer equipment	$ 1,474	$ 1,231
Leasehold improvements	1,810	1,661
Property and equipment, gross	3,284	2,892
Less accumulated depreciation	(1,960)	(1,415)
Property and equipment, net	$ 1,324	$ 1,477

Composition of Certain Financial Statement Captions - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Composition Of Certain Financial Statement Captions [Abstract]
Depreciation expense	$ 500	$ 400
Amortization	$ 100	$ 32

Composition of Certain Financial Statement Captions - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accounts Payable and Accrued Expenses [Abstract]
Accounts payable	$ 8,364	$ 2,611
Accrued payroll and bonus	989	781
Accrued professional fees	147	189
Accrued vacation and compensation	325	252
Accrued R&D studies	309	196
Other current liabilities		122
Accounts payable and accrued expenses, Total	$ 10,134	$ 4,151

Commitments and Contingencies - Additional Information (Details) - USD ($)				12 Months Ended
	Mar. 31, 2022	Jun. 22, 2021	Jan. 08, 2021	Dec. 31, 2022	Dec. 31, 2021
Recorded Unconditional Purchase Obligation [Line Items]
Operating leases expiry year				2025
Operating lease, weighted average discount rate				9.00%
Operating lease, weighted average remaining term				2 years 10 days
Minimum lease payment				$ 268,000
Rent expense				200,000	$ 200,000
Contractual obligation				5,604,000
Lorem Vascular Pte Ltd [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Compensatory damages and operational		$ 6,000,000
Litigation settlement, expense				1,400,000
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, term of contract				12 months
Lessee, operating lease, existence of option to extend [true false]				true
Lessee, operating lease, option to extend				The Charlottesville Lease has a term of 12 months and the Company has the ability to renew for three additional one-year periods
Lessee, operating lease, renewal term				1 year
Lease commencement date				Apr. 01, 2021
Operating leases, expiration date				Mar. 31, 2023
Medidata Solutions, Inc. [Member] \| Services Agreement [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Sales order term	6 months
Sales order cost				$ 1,500,000
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.

Commitments and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Lease expense:
Operating lease expense	$ 159	$ 211
Finance lease expense:
Depreciation of right-of-use assets		7
Total lease expense	159	218
Cash payment information:
Operating cash used for operating leases	159	206
Financing cash used for financing leases	0	8
Total cash paid for amounts included in the measurement of lease liabilities	$ 159	$ 214

Commitments and Contingencies - Summary of Future Minimum Annual Lease Payments under Operating and Financing Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Operating Leases
2023	$ 137
2024	113
2025	18
Total minimum lease payments	268
Less: amount representing interest	(17)
Present value of obligations under leases	251
Less: current portion	(110)	$ (111)
Noncurrent operating lease liability	$ 141	$ 269

License Agreements - Additional Information (Details) - USD ($) $ in Thousands		1 Months Ended
	Mar. 29, 2020	Jan. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
Voting stock, value			$ 34	$ 16
UTHSA License Agreement [Member]
License fee payment in cash		$ 300
Nano Tx Licenses Agreement [Member]
License fee payment in cash	$ 400
Voting stock, value	$ 300
Percentage of non-dilutive monetary awards required to pay	15.00%
Accrued payments due to NanoTx			$ 300

Term Loan Obligations - Additional Information (Details) - USD ($)		12 Months Ended
	May 29, 2015	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Interest expense		$ 711,000	$ 932,000
Non-cash amortization		$ 400,000	$ 500,000
LIBOR [Member] \| Interest Rate Floor [Member]
Debt Instrument [Line Items]
Basis variable rate	1.00%
Term Loan [Member]
Debt Instrument [Line Items]
Origination date		May 29, 2015	May 29, 2015
Original loan amount	$ 17,700,000	$ 17,700,000	$ 17,700,000
Basis variable rate	7.95%
Maturity date	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
Debt instrument, covenant compliance		the Company was in compliance with all of the debt covenants under the Loan and Security Agreement.
Term Loan [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Interest rate	8.95%
Term Loan [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Original loan amount		$ 3,000,000
Long term debt outstanding threshold amount		$ 2,400,000

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

12 Months Ended

Dec. 31, 2022

Dec. 31, 2021

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

^[2]

$ 134

Amended expiration date

Jun. 01, 2024

Remaining Principal (Face Value)

$ 2,412

$ 4,021

[1]	Three month LIBOR rate with a floor of 1% plus 7.95%
[2]	Monthly payment reflects principal and interest

Term Loan Obligations - Future Payments under Obligation (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Future contractual principal and final fee payments on all debt [Abstract]
2023	$ 1,608
2024	3,996
Total	$ 5,604

Term Loan Obligations - Face Value to Book Value Reconciliation (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Face Value to Book Value [Abstract]
Total debt obligations, including final payment fee (Face Value)	$ 5,604
Less: Debt discount	(210)
Total obligation	5,394
Term loan obligation, current	(1,608)	$ (1,608)
Term loan obligation	$ 3,786	$ 5,005

Grant Revenue - Additional Information (Details) - USD ($)		12 Months Ended
	Sep. 19, 2022	Dec. 31, 2022
Grant [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized		$ 224,000
CPRIT Contract [Member]
Disaggregation of Revenue [Line Items]
Maximum grant amount to be received as per grant contract	$ 17,600,000
Grant funding term	3 years
CPRIT grant funding term, description		The CPRIT Grant is subject to customary CPRIT funding conditions, including, but not limited to, a matching fund requirement (one dollar for every two dollars awarded by CPRIT), revenue sharing obligations upon commercialization of rhenium (186Re) obisbemeda based on specific dollar thresholds and tiered low single digit royalty rates until CPRIT receives the aggregate amount of 400% of the proceeds awarded under the CPRIT Grant, and certain reporting requirements.
Contract effective date	Aug. 31, 2022
Contract termination date	Aug. 30, 2025
Percentage of aggregate amount of proceeds awarded under CPRIT grant	400.00%
Percentage of grant proceeds with interest not exceed annually	5.00%
CPRIT Contract [Member] \| Grant [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized		$ 200,000

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Line Items]
Provision or benefit for income taxes	$ 0	$ 0
Income Tax Contingency [Abstract]
Valuation allowance	16,100,000
Increase (decrease) in valuation allowance	$ 4,600,000
Net operating loss carryforwards, Expire date	begin to expire in 2037
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
Deferred tax assets related to NOL carryforwards	12,605,000	10,404,000
Internal Revenue Service (IRS) [Member]
Income Tax Contingency [Abstract]
Federal tax carry forward		346,800,000
State tax credit carryforwards		173,000,000.0
Deferred tax assets related to NOL carryforwards		84,900,000
Overstatement of deferred tax assets		8,400,000
Federal [Member]
Income Tax Contingency [Abstract]
Tax loss carryforwards	59,600,000
Federal tax carry forward	$ 1,200,000
Federal tax credit carryforward, Expiration date	begin to expire in 2039
Net operating losses	$ 56,200,000
Federal [Member] \| Internal Revenue Service (IRS) [Member]
Income Tax Contingency [Abstract]
Research and development credits, overstated		6,000,000.0
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	$ 1,800,000
State [Member] \| Internal Revenue Service (IRS) [Member]
Income Tax Contingency [Abstract]
Research and development credits, overstated		$ 5,500,000

Income Taxes - Reconciliation of Total Income Tax Provision (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
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	22.50%	(699.50%)
Income tax expense (benefit) at state statutory rate	(0.20%)	(0.60%)
Share based compensation	0.90%	0.70%
NOLs expiring and adjustments to NOL	0.50%	720.70%
Research credit	(2.50%)	(0.80%)
Return to provision	(0.10%)	0.50%
Change in state rate	(0.10%)
Total income tax provision	0.00%	(0.00%)

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets [Abstract]
Accrued expenses	$ 262	$ 41
Share based compensation	107	164
Net operating loss carryforwards	12,605	10,404
Income tax credit carryforwards	956	447
Property and equipment, principally due to differences in depreciation	89	19
Intangible assets	2,073	451
Other, net	53	82
Deferred tax assets (Total)	16,145	11,608
Valuation allowance	(16,092)	(11,534)
Total deferred tax assets, net of allowance	53	74
Deferred tax liabilities [Abstract]
Other	(53)	(74)
Total deferred tax liability	(53)	(74)
Net deferred tax assets (liability)	$ 0	$ 0

Income Taxes - Unrecognized Tax Benefits Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Schedule of reconciliation of unrecognized tax benefits activity [Roll Forward]
Unrecognized Tax Benefits – Beginning	$ 81	$ 2,223
Gross decreases – tax positions in prior period	(1)	(2,211)
Gross increase – current-period tax positions	129	69
Unrecognized Tax Benefits – Ending	$ 209	$ 81

Employee Benefit Plan - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Defined Contribution Plan Disclosure [Line Items]
Discretionary or matching contributions	$ 100,000	$ 40,000
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of matching contribution for employee contributions	4.00%

Stockholders' Equity - Preferred Stock (Details) - $ / shares			12 Months Ended
	Sep. 21, 2021	Sep. 20, 2021	Dec. 31, 2022	Dec. 31, 2021
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	1,952
Series A Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)		0
Convertible preferred stock		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	1,014
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) - $ / shares	12 Months Ended
Stockholders' Equity - Warrants (Details) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
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
Common Stock [Member]
Class of Stock [Line Items]
Common stock issued (in shares)	18,091,348	7,864,379
Warrants expected term	5 years
Outstanding Warrants [Member] \| Series U Warrants [Member]
Class of Stock [Line Items]
Class of warrant outstanding	2,141,000
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 ($)						2 Months Ended	4 Months Ended		9 Months Ended	12 Months Ended
Stockholders' Equity - Common stock (Details) - USD ($)	Sep. 09, 2022	Aug. 02, 2022	May 16, 2022	Jan. 14, 2022	Jun. 16, 2020	Feb. 23, 2023	Dec. 31, 2022	Dec. 31, 2022	Sep. 30, 2020	Dec. 31, 2022	Dec. 31, 2021	Aug. 17, 2022	Aug. 15, 2022	Jul. 14, 2022
Class of Stock [Line Items]
Sale of common stock, net										$ 15,278,000	$ 18,581,000
Common stock, shares authorized (in shares)							100,000,000	100,000,000		100,000,000	100,000,000
Proceeds from sale of common stock, net										$ 15,059,000	$ 18,675,000
Common Stock [Member]
Class of Stock [Line Items]
Common stock issued (in shares)										18,091,348	7,864,379
Sale of common stock, net										$ 18,000	$ 8,000
Number of stock repurchased										0
Common Stock [Member] \| Maximum [Member]
Class of Stock [Line Items]
Authorized amount of repurchase of stock													$ 2,000,000.0
2022 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Maximum [Member]
Class of Stock [Line Items]
Common stock, shares authorized (in shares)			57,500,000
2022 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Maximum value of shares to be issued under agreement		$ 50,000,000.0
Common stock issued (in shares)								4,000,000
Period exercisable from the date of issuance										36 months
Number of maximum common shares can be resale												9,500,000
Initial commitment shares		492,698												492,698
Initial commitment fee paid in cash		$ 100,000
Aggregate gross proceeds from sales of common stock		$ 25,000,000.0
Proceeds from sale of common stock, net								$ 3,200,000
2022 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member] \| Subsequent Event [Member]
Class of Stock [Line Items]
Common stock issued (in shares)						0
2022 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member] \| Minimum [Member]
Class of Stock [Line Items]
Percentage issuance of common stock			19.99%
2022 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member] \| Maximum [Member]
Class of Stock [Line Items]
Number of shares reserved for issuance and sale												9,007,302
2020 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Maximum value of shares to be issued under agreement									$ 25,000,000.0
Common stock issued (in shares)										5,665,000
Sale of common stock, net											5,685,186
Period exercisable from the date of issuance									36 months
Proceeds from sale of common stock, net										$ 7,000,000.0	$ 12,500,000
Remaining common stock issued and sold (in shares)							0	0		0
2020 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member] \| Minimum [Member]
Class of Stock [Line Items]
Percentage issuance of common stock					19.99%
2020 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member] \| Maximum [Member]
Class of Stock [Line Items]
Common stock issued (in shares)					23,800,000
September 2022 Distribution Agreement [Member] \| Canaccord Genuity LLC [Member] \| At The Market Offering Program [Member]
Class of Stock [Line Items]
Reimburse of fee and disbursements expenses	$ 50,000
September 2022 Distribution Agreement [Member] \| Canaccord Genuity LLC [Member] \| Common Stock [Member] \| At The Market Offering Program [Member]
Class of Stock [Line Items]
Common stock issued (in shares)							1,031,371
Proceeds from sale of common stock, net							$ 600,000
September 2022 Distribution Agreement [Member] \| Canaccord Genuity LLC [Member] \| Common Stock [Member] \| Subsequent Event [Member] \| At The Market Offering Program [Member]
Class of Stock [Line Items]
Common stock issued (in shares)						1,812,785
Proceeds from sale of common stock, net						$ 700,000
September 2022 Distribution Agreement [Member] \| Canaccord Genuity LLC [Member] \| Common Stock [Member] \| Maximum [Member] \| At The Market Offering Program [Member]
Class of Stock [Line Items]
Proceeds from sale of common stock, net	$ 5,000,000
Percentage of commission on gross proceeds from sale of common stock	3.00%
January 2022 Distribution Agreement [Member] \| Canaccord Genuity LLC [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Common stock issued (in shares)										6,902,279
Proceeds from sale of common stock, net										$ 4,800,000
January 2022 Distribution Agreement [Member] \| Canaccord Genuity LLC [Member] \| Common Stock [Member] \| At The Market Offering Program [Member]
Class of Stock [Line Items]
Remaining availability under financing facility				$ 0
January 2022 Distribution Agreement [Member] \| Canaccord Genuity LLC [Member] \| Common Stock [Member] \| Maximum [Member] \| At The Market Offering Program [Member]
Class of Stock [Line Items]
Proceeds from sale of common stock, net				$ 5,000,000

Share-based Compensation - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares to be issued (in shares)	13,000
Stock option contractual term	10 years
Stock option vesting percentage	25.00%
Stock options exercised	$ 0	$ 0
Dividend yield assumed	$ 0
Total unamortized compensation cost related to outstanding unvested stock options and restricted stock awards		$ 900,000
Weighted average period for recognition of cost		2 years 2 months 12 days
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting period	2 years
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting period	4 years
2015 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
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]
Securities remaining and available for future issuances (in shares)	2,635,717
Common stock shares to be issued (in shares)	3,550,000

Share-based Compensation - Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Options [Roll Forward]
Balance as of December 31, 2021 (in shares)	1,170,890
Granted (in shares)	13,000
Cancelled/forfeited (in shares)	(8,874)
Balance as of December 31, 2022 (in shares)	1,175,016	1,170,890
Vested and expected to vest at December 31, 2021 (in shares)	1,135,664
Exercisable at December 31, 2021	671,892
Weighted Average Exercise Price [Roll Forward]
Balance as of December 31, 2021 (in dollars per share)	$ 5.01
Granted (in dollars per share)	0.53
Cancelled/forfeited (in dollars per share)	60.08
Balance as of December 31, 2022 (in dollars per share)	4.54	$ 5.01
Vested and expected to vest at December 31, 2021 (in dollars per share)	4.57
Exercisable at December 31, 2021 (in dollars per share)	$ 6.11
Weighted Average Remaining Contractual Life (years) [Roll Forward]
Balance as of December 31, 2022	8 years	9 years
Vested and expected to vest at December 31, 2022	8 years
Exercisable at December 31, 2022	7 years 10 months 2 days

Share-based Compensation - Weighted-average Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Black-Scholes-Merton option valuation model based on weighted-average assumptions [Abstract]
Expected term	6 years	6 years
Risk-free interest rate	2.83%	1.00%
Expected volatility	123.40%	127.00%
Dividends	0.00%	0.00%
Resulting fair value	$ 0.47	$ 2.23

Share-based Compensation - Summary of Share-Based Compensation Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 606	$ 606
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	87	75
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 519	$ 531