Plus Therapeutics (PSTV) 10-Q 20 Oct 22 2022 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2022	Oct. 14, 2022
Cover [Abstract]
Entity Registrant Name	PLUS THERAPEUTICS, INC.
Entity Central Index Key	0001095981
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Common Stock, Shares Outstanding		33,601,373
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2022
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Shell Company	false
Trading Symbol	PSTV
Title of 12(b) Security	Common Stock, par value $0.001
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

CONDENSED BALANCE SHEETS (UNAUD

CONDENSED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 20,266	$ 18,400
Grant receivable	73
Other current assets	540	1,324
Total current assets	20,879	19,724
Property and equipment, net	1,453	1,477
Operating lease right-use-of assets	275	341
Goodwill	372	372
Intangible assets, net	113	51
Other assets	12	16
Total assets	23,104	21,981
Current liabilities:
Accounts payable and accrued expenses	5,705	4,151
Operating lease liability	107	111
Term loan obligation, current	1,608	1,608
Total current liabilities	7,420	5,870
Noncurrent operating lease liability	172	269
Term loan obligation	4,108	5,005
Warrant liability		1
Total liabilities	11,700	11,145
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 1,952 shares issued and outstanding at September 30, 2022 and December 31, 2021
Common stock, $0.001 par value; 100,000,000 shares authorized; 32,570,002 and 15,510,025 issued and outstanding at September 30, 2022 and December 31, 2021, respectively	32	16
Additional paid-in capital	472,899	457,730
Accumulated deficit	(461,527)	(446,910)
Total stockholders’ equity	11,404	10,836
Total liabilities and stockholders’ equity	$ 23,104	$ 21,981

CONDENSED BALANCE SHEETS (UNA_2

CONDENSED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Sep. 30, 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)	32,570,002	15,510,025
Common stock, shares outstanding (in shares)	32,570,002	15,510,025

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating expenses:
Research and development	$ 2,945	$ 1,491	$ 7,560	$ 3,724
General and administrative	2,222	1,990	6,653	4,811
Loss on disposal of property and equipment		18		18
Total operating expenses	5,167	3,499	14,213	8,553
Operating loss	(5,094)	(3,499)	(14,140)	(8,553)
Other income (expense):
Interest income	48	5	74	13
Interest expense	(173)	(232)	(552)	(708)
Change in fair value of liability instruments		2	1	4
Total other expense	(125)	(225)	(477)	(691)
Net loss	$ (5,219)	$ (3,724)	$ (14,617)	$ (9,244)
Net loss per share, basic	$ (0.19)	$ (0.28)	$ (0.61)	$ (0.84)
Net loss per share, diluted	$ (0.19)	$ (0.28)	$ (0.61)	$ (0.84)
Basic weighted average shares used in calculating net loss per share attributable to common stockholders	27,441,654	13,264,230	23,789,195	10,961,284
Diluted weighted average shares used in calculating net loss per share attributable to common stockholders	27,441,654	13,264,230	23,789,195	10,961,284
Grant [Member]
Revenue	$ 73		$ 73

CONDENSED STATEMENTS OF STOCKHO

CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) - 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
Stock-based compensation	107			107
Sale of common stock, net	7,078		$ 2	7,076
Sale of common stock, net, shares			2,534,879
Conversion of Series B Convertible Preferred Stock into common stock (share)		(2)	118
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
Net loss	(2,720)				(2,720)
Balance at Mar. 31, 2021	9,513		$ 10	445,734	(436,231)
Balance (in shares) at Mar. 31, 2021		1,952	10,180,525
Balance at Dec. 31, 2020	3,031		$ 7	436,535	(433,511)
Balance (in shares) at Dec. 31, 2020		1,954	6,749,028
Net loss	(9,244)
Balance at Sep. 30, 2021	14,755		$ 15	457,495	(442,755)
Balance (in shares) at Sep. 30, 2021		1,952	15,360,025
Balance at Dec. 31, 2020	3,031		$ 7	436,535	(433,511)
Balance (in shares) at Dec. 31, 2020		1,954	6,749,028
Balance at Dec. 31, 2021	10,836		$ 16	457,730	(446,910)
Balance (in shares) at Dec. 31, 2021		1,952	15,510,025
Balance at Mar. 31, 2021	9,513		$ 10	445,734	(436,231)
Balance (in shares) at Mar. 31, 2021		1,952	10,180,525
Stock-based compensation	138			138
Sale of common stock, net	5,094		$ 2	5,092
Sale of common stock, net, shares			1,907,000
Net loss	(2,800)				(2,800)
Balance at Jun. 30, 2021	11,945		$ 12	450,964	(439,031)
Balance (in shares) at Jun. 30, 2021		1,952	12,087,525
Stock-based compensation	180			180
Sale of common stock, net	6,354		$ 3	6,351
Sale of common stock, net, shares			3,272,500
Net loss	(3,724)				(3,724)
Balance at Sep. 30, 2021	14,755		$ 15	457,495	(442,755)
Balance (in shares) at Sep. 30, 2021		1,952	15,360,025
Balance at Dec. 31, 2021	10,836		$ 16	457,730	(446,910)
Balance (in shares) at Dec. 31, 2021		1,952	15,510,025
Stock-based compensation	180			180
Sale of common stock, net	7,742		$ 6	7,736
Sale of common stock, net, shares			6,687,610
Net loss	(4,116)				(4,116)
Balance at Mar. 31, 2022	14,642		$ 22	465,646	(451,026)
Balance (in shares) at Mar. 31, 2022		1,952	22,197,635
Balance at Dec. 31, 2021	10,836		$ 16	457,730	(446,910)
Balance (in shares) at Dec. 31, 2021		1,952	15,510,025
Net loss	(14,617)
Balance at Sep. 30, 2022	11,404		$ 32	472,899	(461,527)
Balance (in shares) at Sep. 30, 2022		1,952	32,570,002
Balance at Mar. 31, 2022	14,642		$ 22	465,646	(451,026)
Balance (in shares) at Mar. 31, 2022		1,952	22,197,635
Stock-based compensation	167			167
Sale of common stock, net	152			152
Sale of common stock, net, shares			271,047
Net loss	(5,282)				(5,282)
Balance at Jun. 30, 2022	9,679		$ 22	465,965	(456,308)
Balance (in shares) at Jun. 30, 2022		1,952	22,468,682
Stock-based compensation	129			129
Sale of common stock, net	6,815		$ 10	6,805
Sale of common stock, net, shares			10,101,320
Net loss	(5,219)				(5,219)
Balance at Sep. 30, 2022	$ 11,404		$ 32	$ 472,899	$ (461,527)
Balance (in shares) at Sep. 30, 2022		1,952	32,570,002

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Cash flows used in operating activities:
Net loss	$ (5,219)	$ (4,116)	$ (3,724)	$ (2,720)	$ (14,617)	$ (9,244)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization					460	266
Amortization of deferred financing costs and debt discount					309	417
In process research and development acquired					0	18
Change in fair value of liability instruments					(1)	(4)
Stock-based compensation expense					476	425
Non-cash lease expense					(35)	36
Increases (decreases) in cash caused by changes in operating assets and liabilities:
Grant Receivable					73	0
Other current assets					642	12
Accounts payable and accrued expenses					1,955	418
Net cash used in operating activities					(10,738)	(7,656)
Cash flows used in investing activities:
Purchases of property and equipment					(381)	(134)
Purchase of intangible assets					(117)
Proceeds from sale of property and equipment					0	50
In process research and development acquired					(250)	0
Net cash used in investing activities					(748)	(84)
Cash flows from financing activities:
Principal payments of long-term obligations					(1,206)	0
Payment of financing lease liability					0	(8)
Proceeds from exercise of warrants					0	2,017
Proceeds from sale of common stock, net					14,558	18,665
Net cash provided by financing activities					13,352	20,674
Net increase in cash and cash equivalents					1,866	12,934
Cash and cash equivalents at beginning of period		$ 18,400		$ 8,346	18,400	8,346	$ 8,346
Cash and cash equivalents at end of period	$ 20,266		$ 21,280		20,266	21,280	$ 18,400
Cash paid during period for:
Interest					248	292
Supplemental schedule of non-cash investing and financing activities:
Unpaid offering cost					68	139
Right-of-use asset obtained in exchange for lease liabilities					$ 0	$ 81

Basis of Presentation and New A

Basis of Presentation and New Accounting Standards	9 Months Ended
	Sep. 30, 2022
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation and New Accounting Standards	1. Basis of Presentation and New Accounting Standards The accompanying unaudited condensed financial statements as of September 30, 2022 and for the three and nine months ended September 30, 2022 and 2021 have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information. Accordingly, they do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for annual financial statements. The condensed balance sheet at December 31, 2021 has been derived from the audited financial statements at December 31, 2021, but does not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation of the financial position and results of operations of Plus Therapeutics, Inc., and its subsidiaries (collectively, the “Company”) have been included. Operating results for the three and nine months ended September 30, 2022 are not necessarily indicative of the results that may be expected for the year ending December 31, 2022. These financial statements should be read in conjunction with the financial statements and notes therein included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021, filed with the Securities and Exchange Commission on February 24, 2022. 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. 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 beginning in 2019. The Company plans to adopt the new guidance on January 1, 2023, and it does not expect that adoption of this standard will have a material impact on its financial statements and related disclosures.

Use of Estimates

Use of Estimates	9 Months Ended
	Sep. 30, 2022
Use Of Estimates [Abstract]
Use of Estimates	2. 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 Company’s most significant estimates and critical accounting policies involve grant revenue recognition, reviewing assets for impairment, and determining the assumptions used in measuring stock-based compensation expense. As discussed in more detail in Note 7, on September 19, 2022, the Company entered into a Cancer Research Grant Contract (the “CPRIT Contract”), effective as of August 31, 2022 , with the Cancer Prevention and Research Institute of Texas (“CPRIT”), pursuant to which the Company will receive up to $ 17.6 million to fund a portion of the clinical trials. The Company estimates the amount of clinical trial costs that should be borne by CPRIT in accordance with the CPRIT Contract, based on the actual costs incurred and progress of the trial. 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.

Liquidity

Liquidity	9 Months Ended
	Sep. 30, 2022
Liquidity [Abstract]
Liquidity	3. Liquidity The Company incurred net losses of $ 14.6 million for the nine months ended September 30, 2022. The Company had an accumulated deficit of $ 461.5 million as of September 30, 2022. Additionally, the Company used net cash of $ 10.7 million to fund its operating activities for the nine months ended September 30, 2022. As disclosed in more detail in Note 9, 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, the Company will at a minimum need to significantly reduce or curtail its research and development and other operations, and this would negatively affect its ability to achieve corporate growth goals. 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 has no immediate effect on the listing or trading of the Company’s common stock. Pursuant to Nasdaq Listing Rule 5810(c)(3)(A), the Company was provided an initial compliance period of 180 calendar days, or until November 21, 2022, to regain compliance with the Minimum Bid Requirement. To regain compliance, the closing bid price of the Company’s common stock must meet or exceed $ 1.00 per share for a minimum of 10 consecutive business days prior to November 21, 2022. If the Company does not achieve compliance with the Minimum Bid Requirement by November 21, 2022, the Company may be eligible for an additional 180 calendar days to regain compliance. To qualify, the Company would be required to meet the continued listing requirement for market value of publicly held shares and all other Nasdaq initial listing standards, with the exception of the Minimum Bid Requirement, and provide written notice of its intention to cure the minimum bid price deficiency during the second compliance period by effecting a reverse stock split if necessary. If the Nasdaq staff determines that the Company will not be able to cure the deficiency, or if the Company is otherwise not eligible for such additional compliance period, Nasdaq will provide notice that the Company’s common stock will be subject to delisting. In the event the Company receives notice that its common stock is being delisted, Nasdaq rules permit the Company to appeal any delisting determination by the Nasdaq staff. There can be no assurance that the Company will be able to regain compliance with the Minimum Bid Requirement or maintain compliance with the other listing requirements.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. 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 September 30, 2022, the fair value of the Series U Warrants was immaterial, and the change in the fair value of liability classified Series U Warrants during the three and nine months ended September 30, 2022 and 2021 was immaterial.

Term Loan Obligations

Term Loan Obligations	9 Months Ended
	Sep. 30, 2022
Debt Disclosure [Abstract]
Term Loan Obligations	5. 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 made interest only payments through May 1, 2021 and thereafter 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 authoritative accounting guidance, are equity classified and its respective fair value was recorded as a discount to the debt. From September 2017 to July 2019, the Company entered into a total of eight amendments to the Term Loan which, amongst other things, extended the interest only period, required repayment of $ 3.1 million using the proceeds received from sale of the Company’s former UK and Japan subsidiaries in April 2019, increased the final payment, increased the final payment fee upon maturity or early repayment of the Term Loan, and increased the minimum liquidity covenant level to $ 2.0 million. On March 29, 2020, the Company entered into the Ninth Amendment of the Loan and Security Agreement (the “Ninth Amendment”), pursuant to which Oxford agreed to defer the start date of principal repayment from May 1, 2020 to May 1, 2021 and extended the term of the Term Loan from September 1, 2021 to June 1, 2024 . Under authoritative guidance, the Ninth Amendment did not meet the criteria to be accounted for as a troubled debt restructuring. In addition, the Company performed a quantitative analysis and determined that the terms of the new debt and original debt instrument are not substantially different. Accordingly, the Ninth Amendment is accounted for as a debt modification. A new effective interest rate that equates the revised cash flows to the carrying amount of the original debt is computed and applied prospectively. The Term Loan, as amended, is collateralized by a security interest in substantially all of the Company’s existing and subsequently acquired assets, including its intellectual property assets, subject to certain exceptions set forth in the Loan and Security Agreement, as amended. The intellectual property asset collateral will be released upon the Company achieving a certain liquidity level when the total principal outstanding under the Loan and Security Agreement is less than $ 3.0 million. As of September 30, 2022, there was $ 2.8 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 three months ended September 30, 2022 and 2021 was $ 0.2 million. The Company’s interest expense for the nine months ended September 30, 2022 and 2021 was $ 0.6 million and $ 0.7 million, respectively. Interest expense is calculated using the effective interest method; therefore it is inclusive of non-cash amortization in the amount of $ 0.1 million for each of the three months ended September 30, 2022 and 2021, and $ 0.3 million and $ 0.4 million for the nine months ended September 30, 2022 and 2021, respectively, related to the amortization of the debt discount, capitalized loan costs, and accretion of final payment. The Loan and Security Agreement, as amended, contains customary indemnification obligations and customary events of default, including, among other things, the Company’s failure to fulfill certain obligations under the Term Loan, as amended, and the occurrence of a material adverse change, which is defined as a material adverse change in the Company’s business, operations, or condition (financial or otherwise), a material impairment of the prospect of repayment of any portion of the loan. In the event of default by the Company or a declaration of material adverse change by its lender, under the Term Loan, the lender would be entitled to exercise its remedies thereunder, including the right to accelerate the debt, upon which the Company may be required to repay all amounts then outstanding under the Term Loan, which could materially harm the Company’s financial condition. As of September 30, 2022, the Company has not received any notification or indication from Oxford that it intends to invoke the material adverse change clause.

Loss per Share

Loss per Share	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Loss per Share	6 . 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 to outstanding but unexercised options, multiple series of convertible preferred stock, and warrants for all periods presented. The following were excluded from the diluted loss per share calculation for the periods presented because their effect would be anti-dilutive: September 30, 2022 2021 Outstanding stock options 1,175,016 1,050,890 Preferred stock 422,867 422,985 Outstanding warrants 2,141,189 2,141,378 Total 3,739,072 3,615,253

Grant Revenue

Grant Revenue	9 Months Ended
	Sep. 30, 2022
Revenue from Contract with Customer [Abstract]
Grant Revenue	7. 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-186 NanoLiposome ( 186 RNL) 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 186 RNL 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 $ 73,000 in grant revenue from the CPRIT Contract during the three and nine months ended September 30, 2022.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2022
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. 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 condensed balance sheets. Leases with an initial term of 12 months or less are not recorded on the condensed balance sheets. Instead, the Company recognizes lease expense for these leases on a straight-line basis over the lease term in the condensed 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 September 30, 2022. 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 condensed balance sheets. As of September 30, 2022, weighted average discount rate used to measure operating lease liabilities and the operating leases remaining term were 9 % and 2.27 years, respectively. The table below summarizes the Company’s lease costs from its unaudited condensed statement of operations, and cash payments from its unaudited condensed statement of cash flows during the three and nine months ended September 30, 2022 and 2021 (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2022 2021 2022 2021 Lease expense: Operating lease expense $ 34 $ 58 $ 126 $ 166 Finance lease expense: Depreciation of right-of-use assets - - - 7 Total lease expense $ 34 $ 58 $ 126 $ 173 Cash payment information: Operating cash used for operating leases $ 34 $ 56 $ 125 $ 162 Financing cash used for financing leases - - - 8 Total cash paid for amounts included in the measurement of lease liabilities $ 34 $ 56 $ 125 $ 170 Total rent expenses for the nine months ended September 30, 2022 and 2021 were $ 163,000 and $ 170,000 , respectively, which includes leases in the table above, month-to-month operating leases, and common area maintenance charges. The Company’s future minimum annual lease payments under operating leases at September 30, 2022 are as follows (in thousands): Operating Leases Remainder of 2022 $ 34 2023 137 2024 113 2025 18 Total minimum lease payments $ 302 Less: amount representing interest ( 23 ) Present value of obligations under leases 279 Less: current portion ( 107 ) Noncurrent lease obligations $ 172 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 186 RNL 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 has a term of six ( 6 ) months. The Sales Order may only be terminated for a material breach by either party, if the clinical study is terminated or if the clinical study’s authorization or approval is withdrawn by a regulatory agency. 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 RNL-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 September 30, 2022, the Company did no t have any clinical research study obligations. Legal proceedings On June 22, 2021, the Company was named as a defendant in an action brought by Lorem Vascular, Pte. Ltd. (“Lorem”) in the District Court for the District of Delaware. The complaint alleges false representations were made to Lorem regarding the manufacturing facility in the United Kingdom (the “UK Facility”) that Lorem purchased from the Company under the Asset and Equity Purchase Agreement, dated March 29, 2019, between the Company and Lorem (the “Lorem Agreement”). Lorem also claims that false representations were made regarding the UK Facility’s certification to sell and distribute devices in the European Union and export such devices to China. In connection with these allegations, Lorem claims entitlement to at least $ 6,000,000 in compensatory damages and operational costs and expenses (collectively, the “Lorem Claim”). The Company believes that the Lorem Claim is without merit and is vigorously defending the case. No liability was accrued as of September 30, 2022. 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

License Agreements	9 Months Ended
	Sep. 30, 2022
License Agreement [Abstract]
License Agreements	9. 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 condensed statement of operations for the year ended December 31, 2021. The upfront payment of $ 250,000 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.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2022
Stockholders Equity Note [Abstract]
Stockholders' Equity	10. Stockholders’ Equity Preferred Stock The Company has authorized 5,000,000 shares of preferred stock, par value $ 0.001 per share. The Company’s Board of Directors is authorized to designate the terms and conditions of any preferred stock the Company issues without further action by the common stockholders. On September 21, 2021 , Series A 3.6% Convertible Preferred Stock was eliminated. There were no shares of Series A 3.6 % Convertible Preferred Stock immediately prior to September 21, 2021, or December 31, 2020. There were 1,014 shares of Series B Convertible Preferred Stock outstanding as of September 30, 2022 and December 31, 2021. There were 938 shares of Series C Preferred Stock outstanding as of September 30, 2022 and December 31, 2021. As of September 30, 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 5 years from the issuance date, in the form of Series U Warrants (the “Representative Warrants”). In accordance with authoritative guidance, the pre-funded warrants are classified as equity. The Series U Warrants and the Representative Warrants were initially classified at issuance as liabilities due to a contingent obligation for the Company to settle the Series U Warrants with cash upon certain change in control events. In 2020, all but 2,500 Series U Warrants were amended and met the requirements to be classified within stockholder’s equity. As of September 30, 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 $ 125,000 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 September 30, 2022, the Company issued 4,000,000 shares under the 2022 Purchase Agreement for net proceeds of approximately $ 3.2 million. From October 1, 2022 to the date of filing of this Form 10-Q, the Company did no t 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 nine months ended September 30, 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 September 30, 2022, the Company did no t issue any shares of its common stock under the September 2022 Distribution Agreement. From October 1, 2022 to the date of filing of this Form 10-Q, the Company issued 1,000,000 shares under the September 2022 Distribution Agreement for net proceeds of approximately $ 0.6 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 nine months ended September 30, 2022, the Company issued 6,902,279 shares under the January 2022 Distribution Agreement for net proceeds of approximately $ 4.5 million. The January 2022 Distribution Agreement has been terminated after all available registered shares were fully utilized. On October 23, 2020, the Company entered into an Equity Distribution Agreement (the “2020 Distribution Agreement”) with Canaccord. 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 the Company designated from time to time and the Company could at any time suspend sales pursuant to the 2020 Distribution Agreement. During the year ended December 31, 2021, the Company issued 2,179,193 shares under the 2020 Distribution Agreement for net proceeds of $ 6.3 million. The 2020 Distribution Agreement has been terminated after all available registered shares were fully utilized. Stock 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-Q, the Company has no t repurchased any of its common stock under this share repurchase program.

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2022
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based Compensation	11. Stock-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 September 30, 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 3,500,000 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 September 30, 2022, there were 627,212 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 nine months ended September 30, 2022 is as follows: Options Weighted Weighted Aggregate 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 September 30, 2022 1,175,016 $ 4.54 8.27 $ - Vested and expected to vest at September 30, 2022 1,126,448 $ 4.59 8.25 $ - Exercisable at September 30, 2022 585,710 $ 6.69 8.02 $ - As of September 30, 2022, the total compensation cost related to non-vested stock options not yet recognized for all the Company’s plans is approximately $ 1.1 million, which is expected to be recognized as a result of vesting under service conditions over a weighted average period of 2.40 years.

Basis of Presentation and New_2

Basis of Presentation and New Accounting Standards (Policies)	9 Months Ended
	Sep. 30, 2022
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation and New Accounting Standards	The accompanying unaudited condensed financial statements as of September 30, 2022 and for the three and nine months ended September 30, 2022 and 2021 have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information. Accordingly, they do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for annual financial statements. The condensed balance sheet at December 31, 2021 has been derived from the audited financial statements at December 31, 2021, but does not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation of the financial position and results of operations of Plus Therapeutics, Inc., and its subsidiaries (collectively, the “Company”) have been included. Operating results for the three and nine months ended September 30, 2022 are not necessarily indicative of the results that may be expected for the year ending December 31, 2022. These financial statements should be read in conjunction with the financial statements and notes therein included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021, filed with the Securities and Exchange Commission on February 24, 2022.
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.
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 beginning in 2019. The Company plans to adopt the new guidance on January 1, 2023, and it does not expect that adoption of this standard will have a material impact on its financial statements and related disclosures.
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 Company’s most significant estimates and critical accounting policies involve grant revenue recognition, reviewing assets for impairment, and determining the assumptions used in measuring stock-based compensation expense. As discussed in more detail in Note 7, on September 19, 2022, the Company entered into a Cancer Research Grant Contract (the “CPRIT Contract”), effective as of August 31, 2022 , with the Cancer Prevention and Research Institute of Texas (“CPRIT”), pursuant to which the Company will receive up to $ 17.6 million to fund a portion of the clinical trials. The Company estimates the amount of clinical trial costs that should be borne by CPRIT in accordance with the CPRIT Contract, based on the actual costs incurred and progress of the trial. 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.

Loss per Share (Tables)

Loss per Share (Tables)	9 Months Ended
	Sep. 30, 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: September 30, 2022 2021 Outstanding stock options 1,175,016 1,050,890 Preferred stock 422,867 422,985 Outstanding warrants 2,141,189 2,141,378 Total 3,739,072 3,615,253

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2022
Commitments And Contingencies Disclosure [Abstract]
Summary of Lease Costs	The table below summarizes the Company’s lease costs from its unaudited condensed statement of operations, and cash payments from its unaudited condensed statement of cash flows during the three and nine months ended September 30, 2022 and 2021 (in thousands): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2022 2021 2022 2021 Lease expense: Operating lease expense $ 34 $ 58 $ 126 $ 166 Finance lease expense: Depreciation of right-of-use assets - - - 7 Total lease expense $ 34 $ 58 $ 126 $ 173 Cash payment information: Operating cash used for operating leases $ 34 $ 56 $ 125 $ 162 Financing cash used for financing leases - - - 8 Total cash paid for amounts included in the measurement of lease liabilities $ 34 $ 56 $ 125 $ 170
Summary of Future Minimum Annual Lease Payments under Operating Leases	The Company’s future minimum annual lease payments under operating leases at September 30, 2022 are as follows (in thousands): Operating Leases Remainder of 2022 $ 34 2023 137 2024 113 2025 18 Total minimum lease payments $ 302 Less: amount representing interest ( 23 ) Present value of obligations under leases 279 Less: current portion ( 107 ) Noncurrent lease obligations $ 172

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2022
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Option Activity	A summary of activity for the nine months ended September 30, 2022 is as follows: Options Weighted Weighted Aggregate 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 September 30, 2022 1,175,016 $ 4.54 8.27 $ - Vested and expected to vest at September 30, 2022 1,126,448 $ 4.59 8.25 $ - Exercisable at September 30, 2022 585,710 $ 6.69 8.02 $ -

Use of Estimates - Additional I

Use of Estimates - Additional Information (Details) - CPRIT Contract [Member]	Sep. 19, 2022 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum grant amount to be received as per grant contract	$ 17,600,000
Contract effective date	Aug. 31, 2022

Liquidity - Additional Informat

Liquidity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended						9 Months Ended
	May 24, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Liquidity [Abstract]
Net loss		$ (5,219)	$ (5,282)	$ (4,116)	$ (3,724)	$ (2,800)	$ (2,720)	$ (14,617)	$ (9,244)
Accumulated deficit		$ (461,527)						(461,527)		$ (446,910)
Net cash used in operating activities								$ (10,738)	$ (7,656)
Closing bid price for common stock had fallen below	$ 1
Consecutive business days	30 days							10 days
Closing bid price		$ 1						$ 1
Period for regain compliance								180 days

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	9 Months Ended
	Sep. 30, 2022
Series U Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants issued, underwritten public offering, period	2019-09

Term Loan Obligations - Additio

Term Loan Obligations - Additional Information (Details) - USD ($)				3 Months Ended		9 Months Ended
	Mar. 29, 2020	Mar. 28, 2020	May 29, 2015	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Debt Instrument [Line Items]
Interest expense				$ 173,000	$ 232,000	$ 552,000	$ 708,000
Non-cash amortization				100,000	$ 100,000	$ 300,000	$ 400,000
LIBOR [Member] | Interest Rate Floor [Member]
Debt Instrument [Line Items]
Basis variable rate			1%
Term Loan [Member]
Debt Instrument [Line Items]
Origination date						May 29, 2015
Original loan amount			$ 17,700,000
Basis variable rate			7.95%
Maturity date	Jun. 01, 2024	Sep. 01, 2021	May 01, 2021
Fees amount associated with loan			$ 3,200,000	3,200,000		$ 3,200,000
Number of shares callable by warrants (in shares)			188
Warrant exercise price (in dollars per share)			$ 5,175
Date from which warrants are exercisable						Nov. 30, 2015
Warrant expiration date						May 29, 2025
Minimum liquidity covenant				2,000,000		$ 2,000,000
Debt principal repayment start date	May 01, 2021	May 01, 2020
Debt instrument, covenant compliance						the Company was in compliance with all of the debt covenants under the Loan and Security Agreement.
Term Loan [Member] | Loan and Security Agreement [Member] | Sale of the Japanese Subsidiary and Certain Assets [Member]
Debt Instrument [Line Items]
Payments for principal, interest and fees			$ 3,100,000
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		$ 3,000,000
Long term debt outstanding threshold amount						$ 2,800,000

Loss per Share - Schedule of An

Loss per Share - Schedule of Antidilutive Securities Excluded from Diluted Income (Loss) per Share (Details) - shares	9 Months Ended
	Sep. 30, 2022	Sep. 30, 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)	3,739,072	3,615,253
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	1,050,890
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	422,985
Outstanding Warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive common shares excluded from the calculations of diluted loss per share (in shares)	2,141,189	2,141,378

Grant Revenue - Additional Info

Grant Revenue - Additional Information (Details) - USD ($)		3 Months Ended	9 Months Ended
	Sep. 19, 2022	Sep. 30, 2022	Sep. 30, 2022
Grant [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized		$ 73,000	$ 73,000
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 186RNL 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%
Percentage of grant proceeds with interest not exceed annually	5%
CPRIT Contract [Member] | Grant [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized		$ 73,000	$ 73,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)				9 Months Ended
	Mar. 31, 2022	Jun. 22, 2021	Jan. 08, 2021	Sep. 30, 2022	Sep. 30, 2021
Recorded Unconditional Purchase Obligation [Line Items]
Operating leases expiry year				2025
Operating lease, weighted average discount rate				9%
Operating lease, weighted average remaining term				2 years 3 months 7 days
Rent expense				$ 163,000	$ 170,000
Lorem Vascular Pte Ltd [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Compensatory damages and operational		$ 6,000,000
Pre-clinical Research Study Obligations [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Contractual obligation				0
Pre-clinical Research Study Obligations [Member] | Lorem Vascular Pte Ltd [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Litigation settlement, expense				$ 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
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_2

Commitments and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Lease expense:
Operating lease expense	$ 34	$ 58	$ 126	$ 166
Finance lease expense:
Depreciation of right-of-use assets				7
Total lease expense	34	58	126	173
Cash payment information:
Operating cash used for operating leases	34	56	125	162
Financing cash used for financing leases			0	8
Total cash paid for amounts included in the measurement of lease liabilities	$ 34	$ 56	$ 125	$ 170

Commitments and Contingencies_3

Commitments and Contingencies - Summary of Future Minimum Annual Lease Payments under Operating Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Operating Leases
Remainder of 2022	$ 34
2023	137
2024	113
2025	18
Total minimum lease payments	302
Less: amount representing interest	(23)
Present value of obligations under leases	279
Less: current portion	(107)	$ (111)
Noncurrent operating lease liability	$ 172	$ 269

License Agreements - Additional

License Agreements - Additional Information (Details)	1 Months Ended
	Jan. 31, 2022 USD ($)
UTHSA License Agreement [Member]
License fee payment in cash	$ 250,000

Stockholders' Equity - Preferre

Stockholders' Equity - Preferred Stock (Details) - $ / shares			9 Months Ended	12 Months Ended
	Sep. 21, 2021	Sep. 20, 2021	Sep. 30, 2022	Dec. 31, 2020	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		0
Convertible preferred stock		3.60%		3.60%
Series A 3.6% Convertible preferred stock eliminated date	Sep. 21, 2021
Series B Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)			1,014		1,014
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

Stockholders' Equity - Warrants (Details) - $ / shares	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Dec. 31, 2020
Series U Warrants [Member]
Class of Stock [Line Items]
Common stock issued (in shares)							3,450,000
Sale of Stock, Price Per Share	$ 5						$ 5
Warrants expected term	5 years						5 years
Representative Warrants [Member]
Class of Stock [Line Items]
Number of securities called by warrant or right	75,000						75,000
Warrant exercise price (in dollars per share)	$ 6.25						$ 6.25
Common Stock [Member]
Class of Stock [Line Items]
Common stock issued (in shares)	10,101,320	271,047	6,687,610	3,272,500	1,907,000	2,534,879
Warrants expected term	5 years						5 years
Outstanding Warrants [Member] | Series U Warrants [Member]
Class of Stock [Line Items]
Number of securities called by warrant or right								2,500
Class of warrant outstanding	2,141,000						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						2,711,000

Stockholders' Equity - Common s

Stockholders' Equity - Common stock (Details) - USD ($)

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

Sep. 09, 2022

Aug. 02, 2022

May 16, 2022

Jan. 14, 2022

Jun. 16, 2020

Oct. 20, 2022

Sep. 30, 2022

Sep. 30, 2022

Sep. 30, 2022

Jun. 30, 2022

Mar. 31, 2022

Sep. 30, 2021

Jun. 30, 2021

Mar. 31, 2021

Sep. 30, 2022

Sep. 30, 2021

Sep. 30, 2020

Dec. 31, 2021

Aug. 17, 2022

Aug. 15, 2022

Jul. 14, 2022

Oct. 23, 2020

Class of Stock [Line Items]

Sale of common stock, net

$ 6,815,000

$ 152,000

$ 7,742,000

$ 6,354,000

$ 5,094,000

$ 7,078,000

Common stock, shares authorized (in shares)

100,000,000

100,000,000

100,000,000

100,000,000

100,000,000

Proceeds from sale of common stock, net

$ 14,558,000

$ 18,665,000

Common Stock [Member]

Class of Stock [Line Items]

Sale of common stock, net

$ 10,000

$ 6,000

$ 3,000

$ 2,000

$ 2,000

Common stock issued (in shares)

10,101,320

271,047

6,687,610

3,272,500

1,907,000

2,534,879

Number of stock repurchased

0

Common Stock [Member] | Maximum [Member]

Class of Stock [Line Items]

Authorized amount of repurchase of stock

$ 2,000,000

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

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

$ 125,000

Aggregate gross proceeds from sales of common stock

$ 25,000,000

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

Common stock issued (in shares)

5,665,000

5,685,186

Period exercisable from the date of issuance

36 months

Proceeds from sale of common stock, net

$ 7,000,000

$ 12,500,000

Remaining common stock issued and sold (in shares)

0

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

Sales 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

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)

0

September 2022 Distribution Agreement [Member] | Canaccord Genuity LLC [Member] | Common Stock [Member] | At The Market Offering Program [Member] | Subsequent Event [Member]

Class of Stock [Line Items]

Common stock issued (in shares)

1,000,000

Proceeds from sale of common stock, net

$ 600,000

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%

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

$ 4,500,000

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

2020 Distribution Agreement [Member] | Canaccord Genuity LLC [Member] | Common Stock [Member]

Class of Stock [Line Items]

Common stock issued (in shares)

2,179,193

Proceeds from sale of common stock, net

$ 6,300,000

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($) shares
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%
Total unamortized compensation cost related to outstanding unvested stock options and restricted stock awards | $	$ 1.1
Weighted average period for recognition of cost	2 years 4 months 24 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)	627,212
Common stock shares to be issued (in shares)	3,500,000

Stock-based Compensation - Stoc

Stock-based Compensation - Stock Option Activity (Details) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 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 September 30, 2022 (in shares)	1,175,016	1,170,890
Vested and expected to vest at September 30, 2022 (in shares)	1,126,448
Exercisable at September 30, 2022 (in shares)	585,710
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 September 30, 2022 (in dollars per share)	4.54	$ 5.01
Vested and expected to vest at September 30, 2022 (in dollars per share)	4.59
Exercisable at September 30, 2022 (in dollars per share)	$ 6.69
Weighted Average Remaining Contractual Life (years) [Roll Forward]
Balance as of December 31, 2021	8 years 3 months 7 days	9 years
Vested and expected to vest at September 30, 2022	8 years 3 months
Exercisable at September 30, 2022	8 years 7 days