0001564590-20-047266 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2020	Oct. 14, 2020
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		4,779,584
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
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 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

CONSOLIDATED CONDENSED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 7,626	$ 17,552
Accounts receivable		1,169
Restricted cash		40
Inventories, net	107	107
Other current assets	916	957
Total current assets	8,649	19,825
Property and equipment, net	1,943	2,179
Operating lease right-of-use assets	671	781
Other assets	18	72
Goodwill	372	372
Total assets	11,653	23,229
Current liabilities:
Accounts payable and accrued expenses	2,083	3,279
Operating lease liability	140	147
Term loan obligations, net of discount	6,181	11,060
Total current liabilities	8,404	14,486
Noncurrent operating lease liability	545	646
Warrant liability	83	6,929
Other noncurrent liabilities		8
Total liabilities	9,032	22,069
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 1,954 and 1,959 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively
Common stock, $0.001 par value; 100,000,000 shares authorized; 4,591,415 and 3,880,588 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively	5	4
Additional paid-in capital	432,540	426,426
Accumulated deficit	(429,924)	(425,270)
Total stockholders’ equity	2,621	1,160
Total liabilities and stockholders’ equity	$ 11,653	$ 23,229

CONSOLIDATED CONDENSED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Stockholders’ equity:
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	1,954	1,959
Preferred stock, shares outstanding (in shares)	1,954	1,959
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	4,591,415	3,880,588
Common stock, shares outstanding (in shares)	4,591,415	3,880,588

CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Development revenues:
Government contracts and other		$ 4,771	$ 303	$ 5,810
Operating expenses:
Research and development	$ 336	921	1,604	3,636
Sales and marketing	104	94	319	305
General and administrative	956	1,076	3,788	3,313
Total operating expenses	1,396	2,091	6,492	7,254
Operating income (loss)	(1,396)	2,680	(6,189)	(1,444)
Other income (expense):
Interest income	2	6	47	20
Interest expense	(253)	(366)	(854)	(1,477)
Change in fair value of warrants	(81)	(561)	2,342	(69)
Warrant issuance cost		(1,233)		(1,233)
Total other income (expense)	(332)	(2,154)	1,535	(2,759)
Income (Loss) from continuing operations	(1,728)	526	(4,654)	(4,203)
Loss from discontinued operations				(7,568)
Net income (loss)	(1,728)	526	(4,654)	(11,771)
Income (Loss) from continuing operations	(1,728)	526	(4,654)	(4,203)
Beneficial conversion feature for convertible preferred stock		(554)		(554)
Net loss allocable to common stockholders - continuing operations	$ (1,728)	$ (28)	$ (4,654)	(4,757)
Net loss allocable to common stockholders - discontinued operations				$ (7,568)
Basic and diluted net loss per share attributable to common stockholders - continuing operations	$ (0.39)	$ (0.03)	$ (1.13)	$ (8.78)
Basic and diluted net loss per share attributable to common stockholders - discontinued operations				(13.97)
Net loss per share, basic and diluted	$ (0.39)	$ (0.03)	$ (1.13)	$ (22.75)
Basic and diluted weighted average shares used in calculating net loss per share attributable to common stockholders	4,402,221	826,548	4,113,928	541,777
In Process Research and Development [Member] \| Nano Tx Therapeutics [Member]
Operating expenses:
Research and development			$ 781

CONSOLIDATED CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Nano Tx Therapeutics [Member]	Series C Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member] Series B Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member] Series B and C Convertible Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Nano Tx Therapeutics [Member]	Common Stock [Member] Series B Convertible Preferred Stock [Member]	Common Stock [Member] Series B and C Convertible Preferred Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Nano Tx Therapeutics [Member]	Additional Paid-in Capital [Member] Series C Convertible Preferred Stock [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2018	$ 5,225										$ 418,390			$ 1,218	$ (414,383)
Balance (in shares) at Dec. 31, 2018				4,606,000			296,609,000
Share-based compensation	49										49
Sale of common stock, net	1,873										1,873
Sale of common stock, net (in shares)							139,855,000
Conversion of Convertible Preferred Stock into common stock (share)					(66,000)				1,653,000
Foreign currency translation adjustment and accumulated other comprehensive income	(140)													(140)
Net income (loss)	(3,150)														(3,150)
Balance at Mar. 31, 2019	3,857										420,312			1,078	(417,533)
Balance (in shares) at Mar. 31, 2019				4,540,000			438,117,000
Balance at Dec. 31, 2018	5,225										418,390			1,218	(414,383)
Balance (in shares) at Dec. 31, 2018				4,606,000			296,609,000
Net income (loss)	(11,771)
Balance at Sep. 30, 2019	160						$ 3				426,311				(426,154)
Balance (in shares) at Sep. 30, 2019				1,959,000			2,841,588,000
Balance at Dec. 31, 2018	5,225										418,390			1,218	(414,383)
Balance (in shares) at Dec. 31, 2018				4,606,000			296,609,000
Balance at Dec. 31, 2019	$ 1,160						$ 4				426,426				(425,270)
Balance (in shares) at Dec. 31, 2019	3,880,588			1,959,000			3,880,588,000
Balance at Mar. 31, 2019	$ 3,857										420,312			1,078	(417,533)
Balance (in shares) at Mar. 31, 2019				4,540,000			438,117,000
Share-based compensation	28										28
Sale of common stock, net	64										64
Sale of common stock, net (in shares)							5,000,000
Foreign currency translation adjustment and accumulated other comprehensive income	(1,078)													$ (1,078)
Net income (loss)	(9,147)														(9,147)
Balance at Jun. 30, 2019	(6,276)										420,404				(426,680)
Balance (in shares) at Jun. 30, 2019				4,540,000			443,117,000
Issuance of common stock for exercise of warrants	490										490
Issuance of common stock for exercise of warrants (in shares)							65,415,000
Reclassification of warrant liabilities	794										794
Share-based compensation	29										29
Sale of common stock and pre-funded warrants, net of offering costs	4,597						$ 3				4,594
Sale of common stock and pre-funded warrants, net of offering costs (in shares)							2,000,510,000
Conversion of Convertible Preferred Stock into common stock (share)						(2,581,000)				332,546,000
Exercise of warrants (in shares)							65,415,000
Beneficial conversion feature related to Series C Convertible Preferred Stock			$ 554										$ 554
Accretion of beneficial conversion feature related to Series C Convertible Preferred Stock			$ (554)										$ (554)
Net income (loss)	526														526
Balance at Sep. 30, 2019	160						$ 3				426,311				(426,154)
Balance (in shares) at Sep. 30, 2019				1,959,000			2,841,588,000
Balance at Dec. 31, 2019	$ 1,160						$ 4				426,426				(425,270)
Balance (in shares) at Dec. 31, 2019	3,880,588			1,959,000			3,880,588,000
Share-based compensation	$ 12										12
Net income (loss)	(1,087)														(1,087)
Balance at Mar. 31, 2020	85						$ 4				426,438				(426,357)
Balance (in shares) at Mar. 31, 2020				1,959,000			3,880,588,000
Balance at Dec. 31, 2019	$ 1,160						$ 4				426,426				(425,270)
Balance (in shares) at Dec. 31, 2019	3,880,588			1,959,000			3,880,588,000
Net income (loss)	$ (4,654)
Balance at Sep. 30, 2020	$ 2,621						$ 5				432,540				(429,924)
Balance (in shares) at Sep. 30, 2020	4,591,415			1,954,000			4,591,415,000
Balance at Mar. 31, 2020	$ 85						$ 4				426,438				(426,357)
Balance (in shares) at Mar. 31, 2020				1,959,000			3,880,588,000
Issuance of common stock for exercise of warrants	366										366
Issuance of common stock for exercise of warrants (in shares)							162,500,000
Reclassification of warrant liabilities	4,264										4,264
Issuance of common stock for in process research and development acquired		$ 381										$ 381
Issuance of common stock for in process research and development acquired (in share)								230,769,000
Share-based compensation	43										43
Exercise of warrants (in shares)							162,500,000
Net income (loss)	(1,839)														(1,839)
Balance at Jun. 30, 2020	3,300						$ 4				431,492				(428,196)
Balance (in shares) at Jun. 30, 2020				1,959,000			4,273,857,000
Issuance of common stock for exercise of warrants	715						$ 1				714
Issuance of common stock for exercise of warrants (in shares)							317,521,000
Reclassification of warrant liabilities	240										240
Share-based compensation	94										94
Conversion of Convertible Preferred Stock into common stock (share)					(5,000)				37,000
Exercise of warrants (in shares)							317,521,000
Net income (loss)	(1,728)														(1,728)
Balance at Sep. 30, 2020	$ 2,621						$ 5				$ 432,540				$ (429,924)
Balance (in shares) at Sep. 30, 2020	4,591,415			1,954,000			4,591,415,000

CONSOLIDATED CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) (Parenthetical) $ in Millions	3 Months Ended
	Sep. 30, 2019 USD ($)
Statement Of Stockholders Equity [Abstract]
Sale of stock for common stock and pre funded warrants, offering costs	$ 0.6

CONSOLIDATED CONDENSED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Cash flows used in operating activities:
Net loss	$ (1,728)	$ (1,087)	$ 526	$ (3,150)	$ (4,654)	$ (11,771)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization					273	778
Amortization of deferred financing costs and debt discount					428	354
In process research and development acquired from NanoTx Therapeutics					781
Noncash lease expenses					2	22
Change in fair value of warrants	81		561		(2,342)	69
Share-based compensation expense					149	106
Loss on sale of business						6,508
Allocation of issuance costs associated with warrants			1,233			1,233
Increases (decreases) in cash caused by changes in operating assets and liabilities:
Accounts receivable					1,169	(4,851)
Inventories						274
Other current assets					516	252
Other assets					54	298
Accounts payable and accrued expenses					(1,586)	(297)
Deferred revenues						29
Other long-term liabilities						54
Net cash used in operating activities					(5,210)	(6,942)
Cash flows provided by (used in) investing activities:
Purchases of property and equipment					(37)	(8)
In process research and development acquired from NanoTx Therapeutics					(400)
Proceeds from sale of business						5,637
Net cash provided by (used in) investing activities					(437)	5,629
Cash flows used in financing activities:
Principal payments of long-term obligations					(5,307)	(3,490)
Payment of financing lease liability	(42)		(1)		(93)	(75)
Proceeds from exercise of warrants					1,081	491
Proceeds from sale of common stock, net						15,964
Net cash provided by (used in) financing activities					(4,319)	12,890
Effect of exchange rate changes on cash and cash equivalents						(4)
Net increase (decrease) in cash and cash equivalents					(9,966)	11,573
Cash, cash equivalents, and restricted cash at beginning of period		$ 17,592		$ 5,301	17,592	5,301	$ 5,301
Cash, cash equivalents, and restricted cash at end of period	$ 7,626		$ 16,874		7,626	16,874	$ 17,592
Cash paid during period for:
Interest					470	1,071
Supplemental schedule of non-cash investing and financing activities:
Issuance costs paid in common stock					463
Common stock issued in payment for in process research and development					381
Offering cost paid in warrants						213
Unpaid offering costs					$ 12	$ 403

Basis of Presentation and New Accounting Standards

9 Months Ended

Sep. 30, 2020

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 consolidated condensed financial statements as of September 30, 2020 and for the three and nine months ended September 30, 2020 and 2019 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 consolidated condensed balance sheet at December 31, 2019 has been derived from the audited financial statements at December 31, 2019 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, 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020. These financial statements should be read in conjunction with the consolidated financial statements and notes therein included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the Securities and Exchange Commission on March 30, 2020.

On March 30, 2019, the Company entered into an Asset and Share Sale and Purchase Agreement (the “Lorem Purchase Agreement”) with Lorem Vascular Pte. Ltd. (“Lorem”), pursuant to which, among other things, Lorem agreed to purchase the Company’s UK subsidiary, Cytori Ltd. (the “UK Subsidiary”), and the Company’s cell therapy assets, excluding such assets used in Japan or relating to the Company’s contract with the U.S. Department of Health and Human Service’s Biomedical Advanced Research and Development Authority (“BARDA”). Both the Company and Lorem made customary representations, warranties and covenants in the Lorem Purchase Agreement. The transaction was completed on April 24, 2019 and the Company received $4.0 million of cash proceeds, of which $1.7 million was used to pay down principal, interest and fees under the Loan and Security Agreement, dated May 29, 2015 (the “Loan and Security Agreement”) (Note 5), with Oxford Finance, LLC (“Oxford”).

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

Amendments to Certificate of Incorporation

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

Recently Issued Accounting Pronouncements

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

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

Recently Adopted Accounting Pronouncements

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

Use of Estimates

9 Months Ended

Sep. 30, 2020

Use Of Estimates [Abstract]

Use of Estimates

2.	Use of Estimates

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

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

Liquidity and Going Concern

9 Months Ended

Sep. 30, 2020

Liquidity [Abstract]

Liquidity and Going Concern

3.	Liquidity and Going Concern

The Company incurred net losses of $1.7 million and $4.7 million for the three and nine months ended September 30, 2020, respectively. The Company had an accumulated deficit of $429.9 million as of September 30, 2020. Additionally, it used net cash of $5.2 million to fund its operating activities for the nine months ended September 30, 2020. These factors raise substantial doubt about the Company’s ability to continue as a going concern.

To date, these operating losses have been funded primarily from outside sources of invested capital, proceeds raised from the Loan and Security Agreement, and gross profits. The Company has had, and will continue to have, an ongoing need to raise additional cash from outside sources to fund its future clinical development programs and other operations. The Company anticipates using its new equity line facility entered into on September 30, 2020 with Lincoln Park Capital Fund, LLC (“Lincoln Park”) (Note 11) to raise additional cash. The Company’s inability to raise additional cash would have a material and adverse impact on its business and operations and would cause it to default on its loan.

The Company continues to seek additional capital through strategic transactions and from other financing alternatives. Without additional capital, the Company’s current working capital will not provide adequate funding to make debt repayments or support its research, sales and marketing efforts and product development activities at their current levels. If sufficient additional 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.

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

Fair Value

9 Months Ended

Sep. 30, 2020

Fair Value Disclosures [Abstract]

Fair Value

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.

Warrants issued by the Company in connection with a rights offering originally filed under a Form S-1 registration statement in April 2018 (“Series T Warrants”) and in an underwritten public offering in September 2019 (“Series U Warrants”) are classified as liability instruments initially upon issuance. 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.

The estimated fair value of the Series T Warrants as of September 30, 2020 and December 31, 2019 was determined by using an option pricing model with the following assumptions. The Series T Warrants will be 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 and comprehensive loss.

	As of September 30, 2020			As of December 31, 2019
Expected term	0.55 years			1.1 years
Common stock market price	$	2.56		$	2.40
Risk-free interest rate		0.11	%		1.59	%
Expected volatility		128	%		168	%
Resulting fair value (per warrant)	$	1.04		$	1.47

The Company estimated the fair value of the Series U Warrants with the Black Scholes model with the following assumptions. The Series U Warrants that have not been amended (Note 11) will be 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 and comprehensive loss.

	As of September 30, 2020			As of December 31, 2019
Expected term	4 years			4.75 years
Common stock market price	$	2.56		$	2.40
Risk-free interest rate		0.22	%		1.68	%
Expected volatility		146	%		135	%
Resulting fair value (per warrant)	$	2.21		$	1.94

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

	Three Months Ended						Nine Months Ended
Warrant liability	September 30, 2020			September 30, 2019			September 30, 2020			September 30, 2019
Beginning balance	$	242		$	424		$	6,929		$	916
Issuance		—			10,215			—			10,215
Exercise/settlement		—			(794	)		—			(794	)
Change in fair value		81			561			(2,342	)		69
Reclassification to equity		(240	)		—			(4,504	)		—
Ending balance	$	83		$	10,406		$	83		$	10,406

Term Loan Obligations

9 Months Ended

Sep. 30, 2020

Debt Disclosure [Abstract]

Term Loan Obligations

5.	Term Loan Obligations

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

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

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

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

The Term Loan, as amended, is collateralized by a security interest in substantially all of the Company’s existing and subsequently acquired assets, including its intellectual property assets, subject to certain exceptions set forth in the Loan and Security Agreement, as amended. The intellectual property asset collateral will be released upon the Company achieving a certain liquidity level when the total principal outstanding under the Loan and Security Agreement is less than $3 million. As of September 30, 2020, there was $4.3 million principal amount outstanding under the Term Loan, 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, 2020 and 2019 was $0.3 million and $0.4 million, respectively. The Company’s interest expense for the nine months ended September 30, 2020 and 2019 was $0.9 million and $1.5 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 and $0.1 million for the three months ended September 30, 2020 and 2019, and $0.4 million and $0.4 million for the nine months ended September 30, 2020 and 2019, respectively, related to the amortization of the debt discount, capitalized loan costs, and accretion of final payment.

The Loan and Security Agreement, as amended, contains customary indemnification obligations and customary events of default, including, among other things, the Company’s failure to fulfill certain obligations under the Term Loan, as amended, and the occurrence of a material adverse change, which is defined as a material adverse change in the Company’s business, operations, or condition (financial or otherwise), a material impairment of the prospect of repayment of any portion of the loan. In the event of default by the Company or a declaration of material adverse change by its lender, under the Term Loan, the lender would be entitled to exercise its remedies thereunder, including the right to accelerate the debt, upon which the Company may be required to repay all amounts then outstanding under the Term Loan, which could materially harm the Company’s financial condition. As of September 30, 2020, the Company has not received any notification or indication from Oxford to invoke the material adverse change clause. However, due to the Company’s current cash flow position and the substantial doubt about its ability to continue as a going concern, the entire principal amount of the Term Loan is presented as short-term. The Company will continue to evaluate the debt classification on a quarterly basis and evaluate for reclassification in the future should its financial condition improve.

Revenue Recognition

9 Months Ended

Sep. 30, 2020

Revenue Recognition [Abstract]

Revenue Recognition

6.	Revenue Recognition

Development Revenue

The Company received revenue for tasks performed under research and development agreements with governmental agencies, like BARDA, which is outside of the scope of the new revenue recognition guidance. Revenues derived from reimbursement of direct out-of-pocket expenses for research costs associated with government contracts are recorded as government contracts and other within development revenues. Government contract revenue is recorded at the gross amount of the reimbursement. The costs associated with these reimbursements are reflected as a component of research and development expense in the Company’s consolidated condensed statements of operations and comprehensive loss.

The BARDA contract was terminated by the U.S. Department of Health and Human Services effective in December 2019 and the contract close out process was completed during the three months ended September 30, 2020. During the three and nine months ended September 30, 2020, the Company recognized $0 and $0.3 million in development revenue and related costs related to unreimbursed costs prior to termination of the contract, respectively.

- 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

+ Details

Discontinued Operations

9 Months Ended

Sep. 30, 2020

Discontinued Operations And Disposal Groups [Abstract]

Discontinued Operations

7.	Discontinued Operations

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


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

There were no assets or liabilities related to discontinued operations as of September 30, 2020 or December 31, 2019.

The following table summarizes the results of discontinued operations for the nine months ended September 30, 2019 (in thousands). Discontinued operations did not have an impact on the Company’s results of operations during the three months ended September 30, 2019, or the three and nine months ended September 30, 2020.



	Nine Months Ended September 30, 2019

Product revenue	$	901
Cost of revenue		857
Gross profit		44
Operating expenses:
Research and development		656
Sales and marketing		411
General and administrative		185
Total operating expenses		1,252
Operating loss		(1,208	)
Other income (expense)		140
Loss from discontinued operations	$	(1,068	)

During the nine months ended September 30, 2019, revenues from discontinued operations were related to the cell therapy business. Because of the sale of the cell therapy business to Lorem and Mr. Shirahama, all product revenue and costs of product revenues for these periods have been recorded in loss from discontinued operations in the consolidated condensed statements of operations and comprehensive loss.

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


	Nine Months Ended September 30,
	2020		2019
Depreciation and amortization	$	—	$	467

Loss per Share

9 Months Ended

Sep. 30, 2020

Earnings Per Share [Abstract]

Loss per Share

8.	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 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:

	Nine Months Ended September 30,
	2020		2019
Outstanding stock options		531,336		254,000
Outstanding warrants		3,121,125		3,637,000
Preferred stocks		422,985		298,000
Total		4,075,446		4,189,000

Commitments and Contingencies

9 Months Ended

Sep. 30, 2020

Commitments [Abstract]

Commitments and Contingencies

9.	Commitments and Contingencies

Leases

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

The Company records lease liabilities within current liabilities or long-term liabilities based upon the length of time associated with the lease payments. The Company records its operating lease right-of-use assets as long-term assets. Right-of-use assets for financing leases are recorded within property and equipment, net in the balance sheet. Leases with an initial term of 12 months or less are not recorded on the balance sheet. Instead, the Company recognizes lease expense for these leases on a straight-line basis over the lease term.

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

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

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

	As of September 30, 2020
Assets
Operating	$	671
Financing	39
Total leased assets	$	710

Liabilities
Current:
Operating	$	140
Financing	39
Noncurrent:
Operating	545
Financing		—
Total lease liabilities	$	724

Weighted-average remaining lease term (years) - operating leases	6.53
Weighted-average remaining lease term (years) - finance leases	0.37
Weighted-average discount rate - operating leases		7.9	%
Weighted-average discount rate - finance leases		5.0	%

The table below summarizes the Company’s lease costs from its consolidated condensed statement of operations and comprehensive loss, and cash payments from its consolidated condensed statement of cash flows during the three and nine months ended September 30, 2020 (in thousands):

	Three Months Ended				Nine Months Ended
	September 30, 2020		September 30, 2019		September 30, 2020		September 30, 2019
Lease expense:
Operating lease expense	$	52	$	56	$	160	$	169
Finance lease expense:
Depreciation of right-of-use assets		32	32		95		85
Interest expense on lease liabilities	1		2		4		7
Total lease expense	$	85	$	90	$	259	$	261

Cash payment information:
Operating cash used for operating leases	$	56	$	38	$	155	$	147
Financing cash used for financing leases	42		1		93		75
Total cash paid for amounts included in the measurement of lease liabilities	$	98	$	39	$	248	$	222

Total rent expense for the three and nine months ended September 30, 2020 was $48,000 and $177,000, 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 and financing leases at September 30, 2020 are as follows in (thousands):


	Financing Leases		Operating Leases

Remaining 2020	$	32	$	49
2021	7		183
2022	—		123
2023	—		100
Thereafter	—		447
Total minimum lease payments	$	39	$	902
Less: amount representing interest		—		(217	)
Present value of obligations under leases		39		685
Less: current portion		39		(140	)
Noncurrent lease obligations	$	—	$	545

Other commitments

The Company has entered into agreements with various research organizations for pre-clinical and clinical development studies, which have provisions for cancellation. Under the terms of these agreements, the vendors provide a variety of services including conducting research, recruiting and enrolling patients, monitoring studies and data analysis. Payments under these agreements typically include fees for services and reimbursement of expenses. The timing of payments due under these agreements is estimated based on current study progress. As of September 30, 2020, the Company did not have obligations related to its clinical research agreements.

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. Management believes that any liability to the Company that may arise as a result of currently pending legal proceedings will not have a material adverse effect on the Company’s financial condition, liquidity, or results of operations as a whole.

NanoTx License Agreement

9 Months Ended

Sep. 30, 2020

License Agreement [Abstract]

NanoTx License Agreement

10.	NanoTx License Agreement

On March 29, 2020, the Company and NanoTx, Corp. (“NanoTx”) entered into a Patent and Know-How License Agreement (the “NanoTx License Agreement”), pursuant to which NanoTx granted the Company an irrevocable, perpetual, exclusive, fully paid-up license, with the right to sublicense and to make, develop, commercialize and otherwise exploit certain patents, know-how and technology related to the development of radiolabeled nanoliposomes.

On May 7, 2020, all closing conditions under the NanoTx License Agreement were satisfied and the Company paid an upfront payment of $400,000 in cash and issued 230,769 shares of its common stock to NanoTx. Cash and the fair value of common stock issued totaled $781,000 and is recorded as in-process research and development expenses in the consolidated condensed statement of operations and comprehensive loss for the three and nine months ended September 30, 2020. Pursuant to the terms of the NanoTx License Agreement, the Company may be required to pay up to $136.5 million in development and sales milestone payments and a tiered single-digit royalty on U.S. and European sales.

Stockholders' Equity

9 Months Ended

Sep. 30, 2020

Stockholders Equity Note [Abstract]

Stockholders' Equity

11.	Stockholders’ Equity

Preferred Stock

The Company has authorized 5,000,000 shares of preferred stock, par value $0.001 per share. The Company’s Board of Directors is authorized to designate the terms and conditions of any preferred stock the Company issues without further action by the common stockholders. There were no shares of Series A 3.6% Convertible Preferred Stock outstanding as of September 30, 2020 or December 31, 2019. There were 1,016 and 1,021 shares of Series B Convertible Preferred Stock outstanding as of each of September 30, 2020 and December 31, 2019, respectively. There were 938 shares of Series C Preferred Stock outstanding as of September 30, 2020 and December 31, 2019.

As of September 30, 2020, there were 938 outstanding shares of Series C Preferred Stock that can be converted into an aggregate of 416,889 shares of common stock, and 1,016 shares of Series B Convertible Preferred Stock that can be converted into an aggregate of 6,096 shares of common stock. In April 2020, in connection with the Warrant Amendments (defined below), the conversion price of the Series C Preferred Stock was reduced from $3.2132 per share to $2.25 per share.

Warrants

Pursuant to a registration statement on Form S-1 originally filed on April 27, 2018, as amended, which became effective on July 17, 2018, and related prospectus (as supplemented), the Company registered and distributed to holders of its common stock and Series B Convertible Preferred Stock, at no charge, non-transferable subscription rights to purchase up to an aggregate of 20,000 units for $1,000 a unit. Each such unit consisted of one share of Series C Preferred Stock and 1,050 warrants (“Series T Warrants”). Pursuant to the 2018 Rights Offering, which closed on July 25, 2018, the Company sold an aggregate of 6,723 units, resulting in total net proceeds to the Company of approximately $5.7 million. In April 2020, in connection with Warrant Amendments (defined below), the exercise price of the Series T Warrants was further adjusted such that every 50 warrants can be exercised into one share of common stock for $2.25.

As of September 30, 2020, there were 3,787,350 outstanding Series T Warrants that can be exercised into an aggregate of 75,747 shares of common stock.

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

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

Between April and September 2020, the Company entered into revised warrant agreements with the holders of 3,447,500 Series U Warrants (“Warrant Amendments”). In return for reducing the strike price of the warrants to $2.25 per share, the warrant holders agreed to amend the settlement provisions upon a fundamental transaction such that the warrants would meet the requirements to be classified within stockholders’ equity. In September 2020, the Company entered into revised warrant agreements for the Representative Warrants that reduced the strike price of the warrants to $2.81 per share, and the warrant holders agreed to amend the settlement provisions upon a fundamental transaction such that the Representative Warrants would meet the requirements to be classified within stockholders’ equity. Accordingly, approximately $4.5 million of warrant liability was reclassified to the stockholders’ equity section of the balance sheet on the respective effective date of the Warrant Amendment. In addition, approximately $0.7 million of other income representing change in the fair value of amended warrants from April 1, 2020 to the respective effective date of the Warrant Amendments is recorded in the consolidated condensed statement of operations and comprehensive loss for the nine months ended September 30, 2020.

As of September 30, 2020, there were 3,045,000 outstanding Series U Warrants which can be exercised into an aggregate of 3,045,000 shares of common stock.

Common Stock

On September 21, 2018, the Company entered into a purchase agreement (the “2018 Purchase Agreement”) with Lincoln Park pursuant to which the Company had the right to sell to Lincoln Park and Lincoln Park was obligated to purchase up to $5.0 million of shares of the Company’s common stock over the 24-month period following October 15, 2018. Through December 31, 2018, the Company sold a total of 12,802 shares for proceeds of approximately $0.3 million through the 2018 Purchase Agreement. During the year ended December 31, 2019, the Company sold a total of 32,170 shares for proceeds of approximately $0.3 million. The Company believes there is no amount remaining available under this financing facility as of September 30, 2020.

On September 30, 2020, the Company entered into a new purchase agreement (the “2020 Purchase Agreement”) and registration rights agreement pursuant to which Lincoln Park has committed to purchase up to $25.0 million of the Company’s common stock. Under the terms and subject to the conditions of the 2020 Purchase Agreement, the Company has the right, but not the obligation, to sell to Lincoln Park, and Lincoln Park is obligated to purchase up to $25.0 million of the Company’s common stock. Such sales of common stock by the Company, if any, will be subject to certain limitations, and may occur from time to time, at the Company’s sole discretion, over the 36-month period commencing on the date that the registration statement covering the resale of shares of common stock that have been and may be issued under the 2020 Purchase Agreement, is declared effective by the SEC and a final prospectus in connection therewith is filed. As of September 30, 2020, the Company has not sold any shares of common stock under the 2020 Purchase Agreement.

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

On June 16, 2020, the Company received stockholder approval pursuant to Nasdaq Listing Rules 5635(a), 5635(b) and 5635(d) to permit issuances of the Company’s common stock (including the issuance of more than 19.99% of the Company’s common stock) to Lincoln Park pursuant to the 2020 Purchase Agreement. Based on the closing price of the Company’s common stock of $1.05 per share on March 16, 2020 (the Company’s lowest closing sale price since January 1, 2020 as reported on Nasdaq.com) the maximum number of shares the Company could issue and sell under the 2020 Purchase Agreement is approximately 23.8 million shares. Accordingly, the Company requested and received stockholder approval for the issuance of up to 23.8 million shares of the Company’s common stock under the 2020 Purchase Agreement. The Company would seek additional stockholder approval before issuing more than 23.8 million shares.

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

Actual sales of shares of common stock to Lincoln Park under the 2020 Purchase Agreement will depend on a variety of factors to be determined by the Company from time to time, including, among others, market conditions, the trading price of the common stock and determinations by the Company as to the appropriate sources of funding for the Company and its operations.

The net proceeds under the 2020 Purchase Agreement to the Company will depend on the frequency and prices at which the Company sells shares of its stock to Lincoln Park. On October 2, 2020, the Company issued 180,701 shares of common stock to Lincoln Park as a commitment fee in connection with entering into the 2020 Purchase Agreement. The $0.5 million fair value of the commitment fee shares was recorded as other current assets as of September 30, 2020, and the Company expects to sell its common stock pursuant to the 2020 Purchase Agreement during the three months ending December 31, 2020.

Stock-based Compensation

9 Months Ended

Sep. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

12.	Stock-based Compensation

On February 6, 2020, the Company amended the Company’s 2015 New Employee Incentive Plan (the “2015 Plan”) to increase the total number of shares of common stock reserved for issuance under the plan by 250,000 shares. Awards may only be granted under the 2015 Plan to employees who were not previously an employee or director of the Company, or following a bona fide period of non-employment, as a material inducement to entering into employment with the Company. As of September 30, 2020 there were 210,389 shares of common stock remaining and available for future issuances under the 2015 Plan.

On June 16, 2020, the stockholders of the Company approved the Company’s 2020 Stock Incentive Plan (“2020 Plan”), which replaced the Company’s 2014 Equity Incentive Plan. The 2020 Plan provides for the award or sale of shares of common stock (including restricted stock), the award of stock units and stock appreciation rights, and the grant of both incentive stock options to purchase common stock. The 2020 Plan provides for the issuance of up to 550,000 shares of common stock, and the number of shares available for issuance will be increased to the extent that awards granted under the 2020 Plan and the Company’s 2014 Equity Incentive Plan are forfeited or expire (except as otherwise provided in the 2020 Plan). As of September 30, 2020, there were 159,939 shares of common stock remaining and available for future issuances under the 2020 Plan.

A summary of activity for the nine months ended September 30, 2020 is as follows:

	Options			Weighted Average Exercise Price		Aggregate Intrinsic Value
Outstanding as of December 31, 2019		1,865		$	2,968.22
Granted		530,000		$	2.12
Cancelled/forfeited		(529	)	$	2,486.82
Outstanding as of September 30, 2020		531,336		$	10.01	$	233,000
Vested as of September 30, 2020		39,114		$	106.86	$	17,500
Vested and expected to be vested as of September 30, 2020		482,121		$	10.66	$	211,500

As of September 30, 2020, the total compensation cost related to non-vested stock options not yet recognized for the Company’s plans is approximately $786,000, which is expected to be recognized as a result of vesting under service conditions over a weighted average period of 2.99 years.

COVID-19 Pandemic and CARES Act

9 Months Ended

Sep. 30, 2020

Risks And Uncertainties [Abstract]

COVID-19 Pandemic and CARES Act

13.	COVID-19 Pandemic and CARES Act

A novel strain of coronavirus (COVID-19) was declared a global pandemic by the World Health Organization in March 2020. COVID-19 has presented substantial public health and economic challenges and is affecting economies, financial markets and business operations around the world. International and U.S. governmental authorities in impacted regions have taken action in an effort to slow the spread of COVID-19, including issuing varying forms of “stay-at-home” orders, and restricting business functions outside of one’s home. In response, the Company put restrictions on employee travel and working from its executive offices with many employees continuing their work remotely. While the Company has implemented additional health and safety precautions and protocols in response to the pandemic and government guidelines, the Company has not yet experienced a significant impact on its business and operations. However, the Company may experience disruptions that could adversely impact its business operations as well as its preclinical studies and clinical trials. The Company is currently continuing the clinical trials it has underway in sites across the U.S., and, although there has been no significant impact to date, the Company expects that COVID-19 precautions may directly or indirectly impact the timeline for some of its clinical trials. Some of the Company’s clinical trial sites, including those located in areas severely impacted by the pandemic, have placed new patient enrollment into clinical trials on hold or, for patients traveling from out-of-state, have implemented a 14-day self-quarantine before appointments. In addition, some clinical trial sites have imposed limited accessibility to conduct clinical monitoring and training on-site. The Company considered the impacts of COVID-19 on the assumptions and estimates used to prepare its consolidated condensed financial statements and determined that there were no material adverse impacts on the Company’s results of operations and financial position at September 30, 2020. The full extent to which the COVID-19 pandemic will directly or indirectly impact its business, results of operations and financial condition, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat it, as well as the economic impact on local, regional, national and international markets.

In response to the COVID-19 pandemic, the Coronavirus Aid, Relief and Economic Security Act (“CARES Act”) was signed into law on March 27, 2020. The CARES Act, among other things, includes tax provisions relating to refundable payroll tax credits, deferment of employer’s social security payments, net operating loss utilization and carryback periods, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property (QIP). The CARES Act had no material impact on the Company’s income tax provision for the three and nine months ended September 30, 2020. The Company continues to evaluate the impact of the CARES Act on its financial position, results of operations and cash flows.

Basis of Presentation and New Accounting Standards (Policies)	9 Months Ended
	Sep. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation and New Accounting Standards	The accompanying consolidated condensed financial statements as of September 30, 2020 and for the three and nine months ended September 30, 2020 and 2019 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 consolidated condensed balance sheet at December 31, 2019 has been derived from the audited financial statements at December 31, 2019 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, 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020. These financial statements should be read in conjunction with the consolidated financial statements and notes therein included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the Securities and Exchange Commission on March 30, 2020. On March 30, 2019, the Company entered into an Asset and Share Sale and Purchase Agreement (the “Lorem Purchase Agreement”) with Lorem Vascular Pte. Ltd. (“Lorem”), pursuant to which, among other things, Lorem agreed to purchase the Company’s UK subsidiary, Cytori Ltd. (the “UK Subsidiary”), and the Company’s cell therapy assets, excluding such assets used in Japan or relating to the Company’s contract with the U.S. Department of Health and Human Service’s Biomedical Advanced Research and Development Authority (“BARDA”). Both the Company and Lorem made customary representations, warranties and covenants in the Lorem Purchase Agreement. The transaction was completed on April 24, 2019 and the Company received $4.0 million of cash proceeds, of which $1.7 million was used to pay down principal, interest and fees under the Loan and Security Agreement, dated May 29, 2015 (the “Loan and Security Agreement”) (Note 5), with Oxford Finance, LLC (“Oxford”). On April 19, 2019, the Company entered into an Asset and Share Sale and Purchase Agreement (the “Shirahama Purchase Agreement”) with Seijirō Shirahama, pursuant to which, among other things, Mr. Shirahama agreed to purchase the Company’s Japanese subsidiary, Cytori Therapeutics, K.K. (the “Japanese Subsidiary”), and substantially all of the Company’s cell therapy assets used in Japan. Both the Company and Mr. Shirahama made customary representations, warranties and covenants in the Shirahama Purchase Agreement. The transaction was completed on April 25, 2019 and the Company received $3.0 million of cash proceeds, of which $1.4 million was used to pay down principal, interest and fees under the Loan and Security Agreement.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In September 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. The standard amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. For available-for-sale debt securities, entities will be required to recognize an allowance for credit losses rather than a reduction in carrying value of the asset. Entities will no longer be permitted to consider the length of time that fair value has been less than amortized cost when evaluating when credit losses should be recognized. This new guidance is effective in the first quarter of 2023 for calendar-year SEC filers that are smaller reporting companies as of the one-time determination date. Early adoption is permitted beginning in 2019. The Company plans to adopt the new guidance on January 1, 2023, and it does not expect that adoption of this standard will have a material impact on its consolidated financial statements and related disclosures. In August 2020, the FASB issued ASU No. 2020-06, Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”). ASU 2020-06 eliminates the beneficial conversion and cash conversion accounting models for convertible instruments. It also amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions. In addition, ASU 2020-06 modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted EPS computation. The amendments in ASU 2020-06 are effective for smaller reporting companies as defined by the SEC for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020. The Company is currently evaluating the impact of ASU 2020-06 on its financial statements.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-13 (ASU 2018-13), Changes to the Disclosure Requirements for Fair Value Measurement. This ASU eliminates, adds and modifies certain disclosure requirements for fair value measurements as part of its disclosure framework project. The standard is effective for all entities for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. The Company adopted ASU 2018-13 as of January 1, 2020, which did not have a material impact on the Company's financial statements.
Use of Estimates	The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions affecting the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the reporting period. The Company’s most significant estimates and critical accounting policies involve recognizing revenue, reviewing assets for impairment, determining the assumptions used in measuring share-based compensation expense, valuing warrants, and valuing allowances for doubtful accounts. Actual results could differ from these estimates. Management’s estimates and assumptions are reviewed regularly, and the effects of revisions are reflected in the consolidated financial statements in the periods they are determined to be necessary.

Fair Value (Tables)

9 Months Ended

Sep. 30, 2020

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

Summary of Change in Level 3 Warrant Liability Value

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

	Three Months Ended						Nine Months Ended
Warrant liability	September 30, 2020			September 30, 2019			September 30, 2020			September 30, 2019
Beginning balance	$	242		$	424		$	6,929		$	916
Issuance		—			10,215			—			10,215
Exercise/settlement		—			(794	)		—			(794	)
Change in fair value		81			561			(2,342	)		69
Reclassification to equity		(240	)		—			(4,504	)		—
Ending balance	$	83		$	10,406		$	83		$	10,406

Series T Warrants [Member]

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

Schedule of Estimated Fair Value Determined Using Option Pricing Model Assumptions

	As of September 30, 2020			As of December 31, 2019
Expected term	0.55 years			1.1 years
Common stock market price	$	2.56		$	2.40
Risk-free interest rate		0.11	%		1.59	%
Expected volatility		128	%		168	%
Resulting fair value (per warrant)	$	1.04		$	1.47

Series U Warrants [Member]

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

Schedule of Estimated Fair Value Determined Using Option Pricing Model Assumptions

	As of September 30, 2020			As of December 31, 2019
Expected term	4 years			4.75 years
Common stock market price	$	2.56		$	2.40
Risk-free interest rate		0.22	%		1.68	%
Expected volatility		146	%		135	%
Resulting fair value (per warrant)	$	2.21		$	1.94

Discontinued Operations (Tables)

9 Months Ended

Sep. 30, 2020

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



	Nine Months Ended September 30, 2019

Product revenue	$	901
Cost of revenue		857
Gross profit		44
Operating expenses:
Research and development		656
Sales and marketing		411
General and administrative		185
Total operating expenses		1,252
Operating loss		(1,208	)
Other income (expense)		140
Loss from discontinued operations	$	(1,068	)

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


	Nine Months Ended September 30,
	2020		2019
Depreciation and amortization	$	—	$	467

Discontinued Operations Disposed of By Sale [Member]

Summary of Business Consideration to Calculation of the Loss on Sale

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


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

- Definition

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

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+ Details

Loss per Share (Tables)

9 Months Ended

Sep. 30, 2020

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:

	Nine Months Ended September 30,
	2020		2019
Outstanding stock options		531,336		254,000
Outstanding warrants		3,121,125		3,637,000
Preferred stocks		422,985		298,000
Total		4,075,446		4,189,000

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2020

Commitments [Abstract]

Summary of Lease Liabilities and Right-of-Use Assets

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

	As of September 30, 2020
Assets
Operating	$	671
Financing	39
Total leased assets	$	710

Liabilities
Current:
Operating	$	140
Financing	39
Noncurrent:
Operating	545
Financing		—
Total lease liabilities	$	724

Weighted-average remaining lease term (years) - operating leases	6.53
Weighted-average remaining lease term (years) - finance leases	0.37
Weighted-average discount rate - operating leases		7.9	%
Weighted-average discount rate - finance leases		5.0	%

Summary of Lease Costs

	Three Months Ended				Nine Months Ended
	September 30, 2020		September 30, 2019		September 30, 2020		September 30, 2019
Lease expense:
Operating lease expense	$	52	$	56	$	160	$	169
Finance lease expense:
Depreciation of right-of-use assets		32	32		95		85
Interest expense on lease liabilities	1		2		4		7
Total lease expense	$	85	$	90	$	259	$	261

Cash payment information:
Operating cash used for operating leases	$	56	$	38	$	155	$	147
Financing cash used for financing leases	42		1		93		75
Total cash paid for amounts included in the measurement of lease liabilities	$	98	$	39	$	248	$	222

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

The Company’s future minimum annual lease payments under operating and financing leases at September 30, 2020 are as follows in (thousands):


	Financing Leases		Operating Leases

Remaining 2020	$	32	$	49
2021	7		183
2022	—		123
2023	—		100
Thereafter	—		447
Total minimum lease payments	$	39	$	902
Less: amount representing interest		—		(217	)
Present value of obligations under leases		39		685
Less: current portion		39		(140	)
Noncurrent lease obligations	$	—	$	545

Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Option Activity

A summary of activity for the nine months ended September 30, 2020 is as follows:

	Options			Weighted Average Exercise Price		Aggregate Intrinsic Value
Outstanding as of December 31, 2019		1,865		$	2,968.22
Granted		530,000		$	2.12
Cancelled/forfeited		(529	)	$	2,486.82
Outstanding as of September 30, 2020		531,336		$	10.01	$	233,000
Vested as of September 30, 2020		39,114		$	106.86	$	17,500
Vested and expected to be vested as of September 30, 2020		482,121		$	10.66	$	211,500

Basis of Presentation and New Accounting Standards (Details) - USD ($) $ in Thousands			9 Months Ended
	Apr. 25, 2019	Apr. 24, 2019	Sep. 30, 2019
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of business			$ 5,637
Sale of UK Subsidiary and Certain Assets [Member] \| Loan and Security Agreement [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of business		$ 4,000
Payments for principal, interest and fees		$ 1,700
Sale of the Japanese Subsidiary and Certain Assets [Member] \| Loan and Security Agreement [Member]
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of business	$ 3,000
Payments for principal, interest and fees	$ 1,400

Liquidity and Going Concern - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Liquidity [Abstract]
Net loss	$ 1,728	$ 1,839	$ 1,087	$ (526)	$ 9,147	$ 3,150	$ 4,654	$ 11,771
Accumulated deficit	$ (429,924)						(429,924)		$ (425,270)
Net cash used in operating activities							$ (5,210)	$ (6,942)
Substantial doubt about going concern, description							These factors raise substantial doubt about the Company’s ability to continue as a going concern

- Definition

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

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-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22658-107794

+ Details

Fair Value - Schedule of Estimated Fair Value Determined Using Option Pricing Model Assumptions (Details) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Series U Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants expected term	5 years
Level 3 [Member] \| Expected Term [Member] \| Series T Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants expected term	6 months 18 days	1 year 1 month 6 days
Level 3 [Member] \| Expected Term [Member] \| Series U Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants expected term	4 years	4 years 9 months
Level 3 [Member] \| Common Stock Market Price [Member] \| Series T Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	2.56	2.40
Level 3 [Member] \| Common Stock Market Price [Member] \| Series U Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	2.56	2.40
Level 3 [Member] \| Risk-free Interest Rate [Member] \| Series T Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	0.11	1.59
Level 3 [Member] \| Risk-free Interest Rate [Member] \| Series U Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	0.22	1.68
Level 3 [Member] \| Expected Volatility [Member] \| Series T Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	128	168
Level 3 [Member] \| Expected Volatility [Member] \| Series U Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	146	135
Level 3 [Member] \| Resulting Fair Value (Per Warrant) [Member] \| Series T Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	1.04	1.47
Level 3 [Member] \| Resulting Fair Value (Per Warrant) [Member] \| Series U Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	2.21	1.94

Fair Value - Summary of Change in Level 3 Warrant Liability Value (Details) - Warrant Liability [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Warrant liability
Beginning balance	$ 242	$ 424	$ 6,929	$ 916
Issuance		10,215		10,215
Exercise/settlement		(794)		(794)
Change in fair value	81	561	(2,342)	69
Reclassification to equity	(240)		(4,504)
Ending balance	$ 83	$ 10,406	$ 83	$ 10,406

Term Loan Obligations (Details) - USD ($) $ / shares in Units, $ in Thousands						3 Months Ended		9 Months Ended
	Mar. 29, 2020	Mar. 28, 2020	Apr. 29, 2019	Apr. 25, 2019	May 29, 2015	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Warrant exercise price (in dollars per share)						$ 2.25		$ 2.25
Interest expense						$ 253	$ 366	$ 854	$ 1,477
Non-cash amortization						$ 100	$ 100	$ 400	$ 400
Loan and Security Agreement [Member] \| Sale of the Japanese Subsidiary and Certain Assets [Member]
Debt Instrument [Line Items]
Payments for principal, interest and fees				$ 1,400
Term Loan [Member]
Debt Instrument [Line Items]
Origination Date					May 29, 2015
Original Loan Amount					$ 17,700
Basis variable rate					7.95%
Maturity date	Sep. 01, 2024	Sep. 01, 2021			Sep. 01, 2024
Fees amount associated with loan					$ 3,200
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
Debt principal repayment start date	May 01, 2021		May 01, 2020
Prepayments of term loan	$ 5,000
Related final payment	300
Term loan, remaining amount	4,300
Amendment fee	$ 1,000
Debt instrument, covenant compliance								the Company was in compliance with all of the debt covenants under the Loan and Security Agreement.
Term Loan [Member] \| Loan and Security Agreement [Member] \| Sale of the Japanese Subsidiary and Certain Assets [Member]
Debt Instrument [Line Items]
Payments for principal, interest and fees				$ 3,100
Term Loan [Member] \| LIBOR [Member] \| Interest Rate Floor [Member]
Debt Instrument [Line Items]
Basis variable rate					1.00%
Term Loan [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Interest rate					8.95%
Term Loan [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Amount of loan outstanding threshold in order to release intellectual property asset collateral								$ 4,300

Revenue Recognition - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Revenue Recognition [Abstract]
Development revenue and related costs	$ 0.0	$ 0.3

Discontinued Operations - Summary of Business Consideration to Calculation of the Loss on Sale (Details) - USD ($) $ in Thousands		9 Months Ended
	Apr. 25, 2019	Sep. 30, 2019
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net cash proceeds		$ 5,637
Discontinued Operations Disposed of By Sale [Member] \| Cell Therapy Business [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Consideration received	$ 7,000
Transaction costs	(1,363)
Net cash proceeds	5,637
Carrying value of business and assets sold	12,145
Net loss on sale of business	$ (6,508)

Discontinued Operations - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Discontinued Operations And Disposal Groups [Abstract]
Assets Related to Discontinued Operation	$ 0	$ 0
Liabilities Related to Discontinued Operation	$ 0	$ 0

Discontinued Operations - Summary of Operating Results Related to Discontinued Operations (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Discontinued Operations And Disposal Groups [Abstract]
Product revenue	$ 901
Cost of revenue	857
Gross profit	44
Operating expenses:
Research and development	656
Sales and marketing	411
General and administrative	185
Total operating expenses	1,252
Operating loss	(1,208)
Other income (expense)	140
Loss from discontinued operations	$ (1,068)

Discontinued Operations - Summary of Non-Cash Adjustments Related to Discontinued Operations (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Noncash Investing and Financing Items [Abstract]
Depreciation and amortization	$ 467

Loss per Share - Schedule of Antidilutive Securities Excluded from Diluted Income (Loss) per Share (Details) - shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive common shares excluded from the calculations of diluted loss per share (in shares)	4,075,446	4,189,000
Outstanding Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive common shares excluded from the calculations of diluted loss per share (in shares)	531,336	254,000
Outstanding Warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive common shares excluded from the calculations of diluted loss per share (in shares)	3,121,125	3,637,000
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive common shares excluded from the calculations of diluted loss per share (in shares)	422,985	298,000

Commitments and Contingencies - Additional Information (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)
Recorded Unconditional Purchase Obligation [Line Items]
Rent expense	$ 48,000	$ 177,000
Pre-clinical Research Study Obligations [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Contractual obligation	$ 0	$ 0
San Antonio, Texas [Member] \| Office Laboratory and Storage Space [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Operating leases expiry year		2028

Commitments and Contingencies - Summary of Lease Liabilities and Right-of-Use Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets
Operating	$ 671	$ 781
Financing	39
Total leased assets	710
Liabilities
Operating lease liabilities, current	140	147
Financing lease liabilities, current	39
Operating lease liabilities. noncurrent	545	$ 646
Total lease liabilities	$ 724
Weighted-average remaining lease term (years) - operating leases	6 years 6 months 10 days
Weighted-average remaining lease term (years) - finance leases	4 months 13 days
Weighted-average discount rate - operating leases	7.90%
Weighted-average discount rate - finance leases	5.00%

Commitments and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Lease expense:
Operating lease expense	$ 52	$ 56	$ 160	$ 169
Finance lease expense:
Depreciation of right-of-use assets	32	32	95	85
Interest expense on lease liabilities	1	2	4	7
Total lease expense	85	90	259	261
Cash payment information:
Operating cash used for operating leases	56	38	155	147
Financing cash used for financing leases	42	1	93	75
Total cash paid for amounts included in the measurement of lease liabilities	$ 98	$ 39	$ 248	$ 222

Commitments and Contingencies - Summary of Future Minimum Annual Lease Payments under Operating and Financing Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Leases
Remaining 2020	$ 32
2021	7
Total minimum lease payments	39
Present value of obligations under leases	39
Total minimum lease payments	39
Less: current portion	39
Operating Leases
Remaining 2020	49
2021	183
2022	123
2023	100
Thereafter	447
Total minimum lease payments	902
Less: amount representing interest	(217)
Present value of obligations under leases	685
Less: current portion	(140)	$ (147)
Noncurrent operating lease liability	$ 545	$ 646

NanoTx License Agreement - Additional Information (Details) - USD ($)	May 07, 2020	Sep. 30, 2020	Dec. 31, 2019
Common stock, shares issued (in shares)		4,591,415	3,880,588
Common stock, $0.001 par value; 100,000,000 shares authorized; 4,591,415 and 3,880,588 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively		$ 5,000	$ 4,000
NanoTx License Agreement [Member]
License fee payment in cash	$ 400,000
Common stock, shares issued (in shares)	230,769
Common stock, $0.001 par value; 100,000,000 shares authorized; 4,591,415 and 3,880,588 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively	$ 781,000
NanoTx License Agreement [Member] \| Development and Sales Milestone [Member]
Milestone payments	$ 136,500,000

Stockholders' Equity - Preferred Stock (Details) - $ / shares	1 Months Ended	9 Months Ended	12 Months Ended
	Apr. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Preferred Stock [Abstract]
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)		1,954	1,959
Series A Convertible Preferred Stock [Member]
Preferred Stock [Abstract]
Preferred stock, shares outstanding (in shares)		0	0
Convertible preferred stock		3.60%	3.60%
Series B Convertible Preferred Stock [Member]
Preferred Stock [Abstract]
Preferred stock, shares outstanding (in shares)		1,016	1,021
Series B Convertible Preferred Stock [Member] \| 2018 Rights Offering [Member]
Preferred Stock [Abstract]
Preferred stock, shares outstanding (in shares)		1,016
Number of preferred stock, shares converted		6,096
Series C Convertible Preferred Stock [Member]
Preferred Stock [Abstract]
Preferred stock, shares outstanding (in shares)		938	938
Conversion Price Per Share	$ 3.2132
Preferred stock conversion price reduced (in dollars per share)	$ 2.25
Series C Convertible Preferred Stock [Member] \| 2018 Rights Offering [Member]
Preferred Stock [Abstract]
Preferred stock, shares outstanding (in shares)		938
Number of preferred stock, shares converted		416,889

Stockholders' Equity - Warrants (Details) - USD ($)			1 Months Ended	3 Months Ended				9 Months Ended
Stockholders' Equity - Warrants (Details) - USD ($)	Jul. 25, 2018	Jul. 17, 2018	Apr. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Class Of Stock [Line Items]
Warrant exercise price (in dollars per share)				$ 2.25				$ 2.25
Warrant liability				$ 83,000				$ 83,000		$ 6,929,000
Change in fair value of warrants				81,000	$ 561,000			(2,342,000)	$ 69,000
Outstanding Warrants [Member]
Class Of Stock [Line Items]
Warrant liability				$ 4,500,000				4,500,000
Change in fair value of warrants								$ 700,000
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				$ 5.00
Warrants expected term				5 years				5 years
Representative Warrants [Member]
Class Of Stock [Line Items]
Number of shares callable by warrants (in shares)				75,000				75,000
Warrant exercise price (in dollars per share)				$ 6.25				$ 6.25
Warrant exercise price decrease								$ 2.81
Common Stock [Member]
Class Of Stock [Line Items]
Common stock issued (in shares)						5,000,000	139,855,000
Warrants expected term				5 years				5 years
Series C Convertible Preferred Stock [Member]
Class Of Stock [Line Items]
Conversion Price Per Share			$ 3.2132
Preferred stock conversion price reduced (in dollars per share)			$ 2.25
Common Class A
Class Of Stock [Line Items]
Common stock issued (in shares)								289,000
Common Class B
Class Of Stock [Line Items]
Number of shares callable by warrants (in shares)				2,711,000				2,711,000
2018 Rights Offering [Member]
Class Of Stock [Line Items]
Number of shares callable by warrants (in shares)		1
Common stock issued (in shares)	6,723
Gross proceeds from private placement of stock	$ 5,700,000
2018 Rights Offering [Member] \| Outstanding Warrants [Member]
Class Of Stock [Line Items]
Number of shares callable by warrants (in shares)		1,050
2018 Rights Offering [Member] \| Common Stock and Series B Convertible Preferred Stock [Member]
Class Of Stock [Line Items]
Charge on Non Transferable Subscription Rights		$ 0
2018 Rights Offering [Member] \| Series C Convertible Preferred Stock [Member]
Class Of Stock [Line Items]
Number of shares callable by warrants (in shares)		20,000
2018 Rights Offering [Member] \| Series C Convertible Preferred Stock [Member] \| Outstanding Warrants [Member]
Class Of Stock [Line Items]
Warrant exercise price (in dollars per share)		$ 1,000
2018 Rights Offering [Member] \| Common Stock [Member]
Class Of Stock [Line Items]
Number of shares callable by warrants (in shares)			1
2018 Rights Offering [Member] \| Common Stock [Member] \| Outstanding Warrants [Member]
Class Of Stock [Line Items]
Number of shares callable by warrants (in shares)			50
Series T Warrants [Member] \| 2018 Rights Offering [Member] \| Outstanding Warrants [Member]
Class Of Stock [Line Items]
Class of warrant outstanding				3,787,350				3,787,350
Number of warrants exercised								75,747
Series U Warrants [Member] \| Outstanding Warrants [Member]
Class Of Stock [Line Items]
Number of shares callable by warrants (in shares)				3,447,500				3,447,500
Class of warrant outstanding				3,045,000				3,045,000
Number of warrants exercised								3,045,000

Stockholders' Equity - Common stock (Details) - USD ($)					3 Months Ended			9 Months Ended	12 Months Ended
Stockholders' Equity - Common stock (Details) - USD ($)	Oct. 02, 2020	Sep. 30, 2020	Jun. 16, 2020	Sep. 21, 2018	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Dec. 31, 2019	Mar. 16, 2020
Class Of Stock [Line Items]
Sale of common stock, net					$ 64,000	$ 1,873,000
Proceeds from sale of common stock, net								$ 15,964,000
Common Stock [Member]
Class Of Stock [Line Items]
Common stock issued (in shares)					5,000,000	139,855,000
Common Stock [Member] \| Lincoln Park Capital Fund, LLC [Member]
Class Of Stock [Line Items]
Sale of common stock, net				$ 5,000,000
Common stock issued (in shares)									32,170
Proceeds from sale of common stock, net									$ 300,000
Period exercisable from the date of issuance				24 months
Remaining availability under financing facility		$ 0
Common Stock [Member] \| Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member]
Class Of Stock [Line Items]
Common stock issued (in shares)							12,802
Proceeds from sale of common stock, net							$ 300,000
Common Stock [Member] \| 2020 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member]
Class Of Stock [Line Items]
Sale of common stock, net		$ 25,000,000
Common stock issued (in shares)		0
Period exercisable from the date of issuance		36 months
Closing price per share										$ 1.05
Common Stock [Member] \| 2020 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Subsequent Event [Member]
Class Of Stock [Line Items]
Common stock issued (in shares)	180,701
Fair value of commitment fee	$ 500,000
Common Stock [Member] \| 2020 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Minimum [Member] \| Single Regular Purchase [Member]
Class Of Stock [Line Items]
Sale of common stock, net		$ 500,000
Common stock issued (in shares)		50,000
Common Stock [Member] \| 2020 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Maximum [Member]
Class Of Stock [Line Items]
Common stock issued (in shares)			23,800,000
Percentage issuance of common stock			19.99%
Common Stock [Member] \| 2020 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Maximum [Member] \| Single Regular Purchase [Member]
Class Of Stock [Line Items]
Common stock issued (in shares)		100,000
Closing price per share		$ 0.25

Stock-based Compensation - Additional Information (Details) - USD ($) $ in Thousands		9 Months Ended
	Jun. 16, 2020	Sep. 30, 2020	Feb. 06, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares to be issued (in shares)		530,000
Total unamortized compensation cost related to outstanding unvested stock options and restricted stock awards		$ 786,000
Weighted average period for recognition of cost		2 years 11 months 26 days
2015 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increased in the total number of shares of common stock reserved for issuance			250,000
Securities remaining and available for future issuances (in shares)		210,389
2020 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Securities remaining and available for future issuances (in shares)		159,939
2020 Plan [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares to be issued (in shares)	550,000

Stock-based Compensation - Stock Option Activity (Details)	9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares
Options [Roll Forward]
Balance as of December 31, 2019 (in share) \| shares	1,865
Common stock shares to be issued (in shares) \| shares	530,000
Cancelled/forfeited (in share) \| shares	(529)
Balance as of September 30, 2020 (in share) \| shares	531,336
Vested as of September 30, 2020 \| shares	39,114
Vested and expected to be vested as of September 30, 2020 \| shares	482,121
Weighted Average Exercise Price [Roll Forward]
Balance as of December 31, 2019 (in dollars per share) \| $ / shares	$ 2,968.22
Granted (in dollars per share) \| $ / shares	2.12
Cancelled/forfeited (in dollars per share) \| $ / shares	2,486.82
Balance as of September 30, 2020 (in dollars per share) \| $ / shares	10.01
Vested as of September 30, 2020 \| $ / shares	106.86
Vested and expected to be vested as of September 30, 2020 \| $ / shares	$ 10.66
Aggregate Intrinsic Value [Roll Forward]
Balance as of September 30, 2020 \| $	$ 233,000
Vested as of September 30, 2020 \| $	17,500
Vested and expected to be vested as of September 30, 2020 \| $	$ 211,500