View Filing Data

Print Document View Excel Document

Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2020	Aug. 03, 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		4,273,878
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 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	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 9,266	$ 17,552
Accounts receivable	951	1,169
Restricted cash		40
Inventories, net	107	107
Other current assets	469	957
Total current assets	10,793	19,825
Property and equipment, net	2,014	2,179
Operating lease right-of-use assets	707	781
Other assets	18	72
Goodwill	372	372
Total assets	13,904	23,229
Current liabilities:
Accounts payable and accrued expenses	3,608	3,279
Operating lease liability	139	147
Term loan obligations, net of discount	6,026	11,060
Total current liabilities	9,773	14,486
Noncurrent operating lease liability	589	646
Warrant liability	242	6,929
Other noncurrent liabilities		8
Total liabilities	10,604	22,069
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 1,959 shares issued and outstanding at June 30, 2020 and December 31, 2019
Common stock, $0.001 par value; 100,000,000 shares authorized; 4,273,857 and 3,880,588 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	4	4
Additional paid-in capital	431,492	426,426
Accumulated deficit	(428,196)	(425,270)
Total stockholders’ equity	3,300	1,160
Total liabilities and stockholders’ equity	$ 13,904	$ 23,229

CONSOLIDATED CONDENSED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Jun. 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)	1,959	1,959
Preferred stock, shares outstanding (in shares)	1,959	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)	4,273,857	3,880,588
Common stock, shares outstanding (in shares)	4,273,857	3,880,588

CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Development revenues:
Government contracts and other	$ 185	$ 302	$ 303	$ 1,039
Operating expenses:
Research and development	327	1,289	1,268	2,715
Sales and marketing	105	97	215	211
General and administrative	1,324	875	2,832	2,237
Total operating expenses	2,537	2,261	5,096	5,163
Operating loss	(2,352)	(1,959)	(4,793)	(4,124)
Other income (expense):
Interest income	9	7	45	14
Interest expense	(252)	(597)	(601)	(1,111)
Change in fair value of warrants	756	282	2,423	492
Total other income (expense)	513	(308)	1,867	(605)
Loss from continuing operations	(1,839)	(2,267)	(2,926)	(4,729)
Loss from discontinued operations		(6,880)		(7,568)
Net loss	$ (1,839)	$ (9,147)	$ (2,926)	$ (12,297)
Basic and diluted net loss per share attributable to common stockholders - continuing operations	$ (0.45)	$ (5.12)	$ (0.74)	$ (11.89)
Basic and diluted net loss per share attributable to common stockholders - discontinued operations		(15.55)		(19.02)
Net loss per share, basis and diluted	$ (0.45)	$ (20.67)	$ (0.74)	$ (30.91)
Basic and diluted weighted average shares used in calculating net loss per share attributable to common stockholders	4,053,242	442,512	3,967,392	397,827
In Process Research and Development [Member] \| Nano Tx Therapeutics [Member]
Operating expenses:
Research and development	$ 781		$ 781

CONSOLIDATED CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Nano Tx Therapeutics [Member]	Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member] Series B Convertible Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Nano Tx Therapeutics [Member]	Common Stock [Member] Series B Convertible Preferred Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Nano Tx Therapeutics [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 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 loss	(12,297)
Balance at Jun. 30, 2019	(6,276)							420,404			(426,680)
Balance (in shares) at Jun. 30, 2019			4,540,000		443,117,000
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
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 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
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 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
Sale of common stock, net (in shares)	3,450,000
Net loss	$ (2,926)
Balance at Jun. 30, 2020	$ 3,300				$ 4			431,492			(428,196)
Balance (in shares) at Jun. 30, 2020	4,273,857		1,959,000		4,273,857,000
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
Net loss	(1,839)										(1,839)
Balance at Jun. 30, 2020	$ 3,300				$ 4			$ 431,492			$ (428,196)
Balance (in shares) at Jun. 30, 2020	4,273,857		1,959,000		4,273,857,000

CONSOLIDATED CONDENSED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash flows used in operating activities:
Net loss	$ (1,839)	$ (1,087)	$ (9,147)	$ (3,150)	$ (2,926)	$ (12,297)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization					188	617
Amortization of deferred financing costs and debt discount					275	257
In process research and development acquired from NanoTx Therapeutics					781	0
Noncash lease expenses					9	39
Change in fair value of warrants	(756)		(282)		(2,423)	(492)
Share-based compensation expense					55	77
Loss on sale of business					0	6,508
Increases (decreases) in cash caused by changes in operating assets and liabilities:
Accounts receivable					218	(28)
Inventories					0	235
Other current assets					487	216
Other assets					54	257
Accounts payable and accrued expenses					371	108
Deferred revenues					0	29
Other long-term liabilities					0	54
Net cash used in operating activities					(2,911)	(4,420)
Cash flows provided by (used in) investing activities:
Purchases of property and equipment					(23)	(6)
In process research and development acquired from NanoTx Therapeutics					(400)	0
Proceeds from sale of business					0	5,637
Net cash provided by (used in) investing activities					(423)	5,631
Cash flows used in financing activities:
Principal payments of long-term obligations					(5,307)	(3,490)
Payment of financing lease liability	(33)		(20)		(51)	(28)
Proceeds from exercise of warrants					366	0
Proceeds from sale of common stock, net					0	1,984
Net cash used in financing activities					(4,992)	(1,534)
Effect of exchange rate changes on cash and cash equivalents					0	(4)
Net decrease in cash and cash equivalents					(8,326)	(327)
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	$ 9,266		$ 4,974		9,266	4,974	$ 17,592
Cash paid during period for:
Interest					372	826
Supplemental schedule of non-cash investing and financing activities:
Common stock issued in payment for in process research and development					$ 381	$ 0

Basis of Presentation and New Accounting Standards

6 Months Ended

Jun. 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 June 30, 2020 and for the three and six months ended June 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 six months ended June 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 and Reverse Stock Split

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

On August 5, 2019, following stockholder and Board approval, the Company filed a Certificate of Amendment (the “August 2019 Amendment”) to its Amended and Restated Certificate of Incorporation (the Amendment), as amended, with the Secretary of State of the State of Delaware to effectuate a one-for-fifty (1:50) reverse stock split (the “August 2019 Reverse Stock Split”) of its common stock, par value $0.001 per share, without any change to its par value. The August 2019 Amendment became effective on the filing date. The August 2019 Reverse Stock Split became effective for trading purposes as of the commencement of trading on the Nasdaq Capital Market on August 6, 2019. There was no change in the Company’s Nasdaq ticker symbol, “PSTV,” as a result of the August 2019 Reverse Stock Split. Upon effectiveness, each 50 shares of issued and outstanding common stock were converted into one newly issued and outstanding share of common stock. The Company’s 5,000,000 shares of authorized Preferred Stock were not affected by the August 2019 Reverse Stock Split. No fractional shares were issued in connection with the August 2019 Reverse Stock Split. Any fractional shares of common Stock that would have otherwise resulted from the August 2019 Reverse Stock Split were rounded up to the nearest whole share. Outstanding equity awards and the shares available for future grant under the Company’s Amended and Restated 2004 Equity Incentive Plan, 2011 Employee Stock Purchase Plan, 2014 Amended and Restated Equity Incentive Plan and 2015 New Employee Incentive Plan were proportionately reduced (rounded down to the nearest whole share), and the exercise prices of outstanding equity awards were proportionately increased (rounded up to the nearest whole cent) to give effect to the August 2019 Reverse Stock Split.

Recently Issued Accounting Pronouncements

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

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 has not had a material impact on the Company's financial statements.

Use of Estimates

6 Months Ended

Jun. 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

6 Months Ended

Jun. 30, 2020

Liquidity [Abstract]

Liquidity and Going Concern

3.	Liquidity and Going Concern

The Company incurred net losses of $1.8 million and $2.9 million for the three and six months ended June 30, 2020, respectively. The Company had an accumulated deficit of 428.2 million as of June 30, 2020. Additionally, it used net cash of $2.9 million to fund its operating activities for the six months ended June 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’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.

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

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

6 Months Ended

Jun. 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 June 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 June 30, 2020			As of December 31, 2019
Expected term	0.8 years			1.1 years
Common stock market price	$	2.12		$	2.40
Risk-free interest rate		0.17	%		1.59	%
Expected volatility		119	%		168	%
Resulting fair value (per warrant)	$	0.82		$	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 June 30, 2020			As of December 31, 2019
Expected term	4.2 years			4.75 years
Common stock market price	$	2.12		$	2.40
Risk-free interest rate		0.25	%		1.68	%
Expected volatility		142	%		135	%
Resulting fair value (per warrant)	$	1.64		$	1.94

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

	Three Months Ended						Six Months Ended
Warrant liability	June 30, 2020			June 30, 2019			June 30, 2020			June 30, 2019
Beginning balance	$	5,262		$	706		$	6,929		$	916
Change in fair value		(756	)		(282	)		(2,423	)		(492	)
Reclass to equity		(4,264	)		—			(4,264	)		—
Ending balance	$	242		$	424		$	242		$	424

Term Loan Obligations

6 Months Ended

Jun. 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 June 1, 2024, the maturity date. At maturity of the Term Loan, or earlier repayment in full following voluntary prepayment or upon acceleration, the Company is required to make a final payment in an aggregate amount equal to approximately $.3.2 million. In connection with the Term Loan, on May 29, 2015, the Company issued to Oxford warrants to purchase an aggregate of 188 shares of the Company’s common stock at an exercise price of $5,175 per share. These warrants became exercisable as of November 30, 2015 and will expire on May 29, 2025 and, following the authoritative accounting guidance, are equity classified and its respective fair value was recorded as a discount to the debt.

From September 2017 to March 2019, the Company entered into a total 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 June 1, 2021 to June 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 certain liquidity level when the total principal outstanding under the Loan and Security Agreement is less than $3 million. As of June 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 June 30, 2020 and 2019 was $0.3 million and $0.6 million, respectively. The Company’s interest expense for the six months ended June 30, 2020 and 2019 was $0.6 million and $1.1 million, respectively. Interest expense is calculated using the effective interest method, therefore it is inclusive of non-cash amortization in the amount of $0.2 million and $0.1 million for the three months ended June 30, 2020 and 2019, and $0.3 million and $0.3 million for the six months ended June 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 June 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

6 Months Ended

Jun. 30, 2020

Revenue Recognition [Abstract]

Revenue Recognition

6.	Revenue Recognition

Development Revenue

The Company receives 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 effectively in December 2019. During the three and six months ended June 30, 2020, the Company recognized $0.2 million and $0.3 million in development revenue and related costs related to unreimbursed costs prior to termination of the contract, respectively.

Discontinued Operations

6 Months Ended

Jun. 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 June 30, 2020 or December 31, 2019.

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



	Three Months Ended June 30, 2019			Six Months Ended June 30, 2019

Product revenue	$	197		$	901
Cost of revenue		199			857
Gross profit		(2	)		44
Operating expenses:
Research and development		237			656
Sales and marketing		97			411
General and administrative		39			185
Total operating expenses		373			1,252
Operating loss		(375	)		(1,208	)
Other income (expense)		(5)			142
Loss from discontinued operations	$	(380	)	$	(1,066	)

During the three and six months ended June 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):


	Six Months Ended June 30,
	2020		2019
Depreciation and amortization	$	—	$	467
Provision for excess inventory	$	—	$	—
Loss on asset disposal	$	—	$	—

Loss per Share

6 Months Ended

Jun. 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:

	Six Months Ended June 30,
	2020		2019
Outstanding stock options		531,741		2,000
Outstanding warrants		3,474,500		178,000
Preferred stocks		298,000		92,000
Total		4,304,241		272,000

Commitments and Contingencies

6 Months Ended

Jun. 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 June 30, 2020
Assets
Operating	$	707
Financing	71
Total leased assets	$	778

Liabilities
Current:
Operating	$	139
Financing	79
Noncurrent:
Operating	589
Financing	—
Total lease liabilities	$	807

Weighted-average remaining lease term (years) - operating leases	6.61
Weighted-average remaining lease term (years) - finance leases	0.6
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 six months ended June 30, 2020 (in thousands):

	Three Months Ended				Six Months Ended
	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
Lease expense:
Operating lease expense	$	53	$	55	$	108	$	109
Finance lease expense:
Depreciation of right-of-use assets	31		28		63		56
Interest expense on lease liabilities	1		6		3		12
Total lease expense	$	85	$	89	$	174	$	177

Cash payment information:
Operating cash used for operating leases	$	48	$	55	$	99	$	109
Financing cash used for financing leases	33		20		51		28
Total cash paid for amounts included in the measurement of lease liabilities	$	81	$	75	$	150	$	137

Total rent expense for the three and six months ended June 30, 2020 was $34,000 and $129,000, 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 June 30, 2020 are as follows in (thousands):


	Financing Leases			Operating Leases

Remaining 2020	$	72		$	106
2021	7			183
2022		—		123
2023		—		100
Thereafter		—		448
Total minimum lease payments	$	79		$	960
Less: amount representing interest		—			(232	)
Present value of obligations under leases	79				728
Less: current portion		(79	)		(139	)
Noncurrent lease obligations	$	—		$	589

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 June 30, 2020, the Company had clinical research study obligations of $34 thousand, all of which is expected to be paid within a year. Should the timing of the clinical trials change, the timing of the payment of these obligations would also change.

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

6 Months Ended

Jun. 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 six months ended June 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

6 Months Ended

Jun. 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 June 30, 2020 or December 31, 2019. There were 1,021 shares of Series B Convertible Preferred Stock outstanding as of each of June 30, 2020 and December 31, 2019. There were 938 shares of Series C Preferred Stock outstanding as of June 30, 2020 and December 31, 2019.

As of June 30, 2020, there were 938 outstanding shares of Series C Preferred Stock that can be converted into an aggregate of 291,920 shares of common stock, and 1,021 shares of Series B Convertible Preferred Stock that can be converted into an aggregate of 6,133 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 June 30, 2020, there were 3,788,400 outstanding Series T Warrants that can be exercised into an aggregate of 75,768 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 5.0 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 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 June 2020, the Company entered into revised warrant agreements with the holders of 3,415,000 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 fundamental transactions such that the warrants would meet the requirements to be classified within stockholders’ equity. Accordingly, approximately $4.3 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 $0.8 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 three months ended June 30, 2020.

As of June 30, 2020, there were 3,362,500 outstanding Series U Warrants which can be exercised into an aggregate of 3,362,500 shares of common stock.

Common Stock

On September 21, 2018, the Company entered into the Lincoln Park Purchase Agreement with Lincoln Park pursuant to which the Company has the right to sell to Lincoln Park and Lincoln Park is 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 Lincoln Park 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 June 30, 2020.

Stock-based Compensation

6 Months Ended

Jun. 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 June 30, 2020 there were 210,030 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 replaces 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 June 30, 2020, there were 106,000 shares of common stock remaining and available for future issuances under the 2020 Plan.

A summary of activity for the six months ended June 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		(124	)	$	9,905.00
Outstanding as of June 30, 2020		531,741		$	10.24	$	—
Vested as of June 30, 2020		1,143		$	3,663.00	$	—
Vested and expected to be vested as of June 30, 2020		531,741		$	10.24	$	8,480

As of June 30, 2020, the total compensation cost related to non-vested stock options not yet recognized for the Company’s plans is approximately $1,073,000, which is expected to be recognized as a result of vesting under service conditions over a weighted average period of 3.10 years.

COVID-19 Pandemic and CARES Act

6 Months Ended

Jun. 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 are taking 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 has 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. 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 June 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 six months ended June 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)	6 Months Ended
	Jun. 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 June 30, 2020 and for the three and six months ended June 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 six months ended June 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 June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. The standard amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. For available-for-sale debt securities, entities will be required to recognize an allowance for credit losses rather than a reduction in carrying value of the asset. Entities will no longer be permitted to consider the length of time that fair value has been less than amortized cost when evaluating when credit losses should be recognized. This new guidance is effective in the first quarter of 2023 for calendar-year SEC filers that are smaller reporting companies as of the one-time determination date. Early adoption is permitted beginning in 2019. The Company plans to adopt the new guidance on January 1, 2023, and it does not expect that adoption of this standard will have an impact on its consolidated financial statements and related disclosures.
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 has not had 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)

6 Months Ended

Jun. 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						Six Months Ended
Warrant liability	June 30, 2020			June 30, 2019			June 30, 2020			June 30, 2019
Beginning balance	$	5,262		$	706		$	6,929		$	916
Change in fair value		(756	)		(282	)		(2,423	)		(492	)
Reclass to equity		(4,264	)		—			(4,264	)		—
Ending balance	$	242		$	424		$	242		$	424

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 June 30, 2020			As of December 31, 2019
Expected term	0.8 years			1.1 years
Common stock market price	$	2.12		$	2.40
Risk-free interest rate		0.17	%		1.59	%
Expected volatility		119	%		168	%
Resulting fair value (per warrant)	$	0.82		$	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 June 30, 2020			As of December 31, 2019
Expected term	4.2 years			4.75 years
Common stock market price	$	2.12		$	2.40
Risk-free interest rate		0.25	%		1.68	%
Expected volatility		142	%		135	%
Resulting fair value (per warrant)	$	1.64		$	1.94

Discontinued Operations (Tables)

6 Months Ended

Jun. 30, 2020

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



	Three Months Ended June 30, 2019			Six Months Ended June 30, 2019

Product revenue	$	197		$	901
Cost of revenue		199			857
Gross profit		(2	)		44
Operating expenses:
Research and development		237			656
Sales and marketing		97			411
General and administrative		39			185
Total operating expenses		373			1,252
Operating loss		(375	)		(1,208	)
Other income (expense)		(5)			142
Loss from discontinued operations	$	(380	)	$	(1,066	)

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


	Six Months Ended June 30,
	2020		2019
Depreciation and amortization	$	—	$	467
Provision for excess inventory	$	—	$	—
Loss on asset disposal	$	—	$	—

Discontinued Operations Disposed of By Sale [Member]

Summary of Business Consideration to Calculation of the Loss on Sale

The following table summarizes the calculation of the loss on 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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=109226691&loc=SL51724579-110230

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109222650&loc=d3e1474-107760

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5D
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721677-107760

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109222160&loc=SL51721533-107759

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3A
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721659-107760

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721665-107760

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2941-110230

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5C
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721675-107760

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109222650&loc=d3e1361-107760

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5A
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721671-107760

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5B
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721673-107760

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 4A
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721663-107760

+ Details

Loss per Share (Tables)

6 Months Ended

Jun. 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:

	Six Months Ended June 30,
	2020		2019
Outstanding stock options		531,741		2,000
Outstanding warrants		3,474,500		178,000
Preferred stocks		298,000		92,000
Total		4,304,241		272,000

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 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 June 30, 2020
Assets
Operating	$	707
Financing	71
Total leased assets	$	778

Liabilities
Current:
Operating	$	139
Financing	79
Noncurrent:
Operating	589
Financing	—
Total lease liabilities	$	807

Weighted-average remaining lease term (years) - operating leases	6.61
Weighted-average remaining lease term (years) - finance leases	0.6
Weighted-average discount rate - operating leases		7.9	%
Weighted-average discount rate - finance leases		5.0	%

Summary of Lease Costs

	Three Months Ended				Six Months Ended
	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
Lease expense:
Operating lease expense	$	53	$	55	$	108	$	109
Finance lease expense:
Depreciation of right-of-use assets	31		28		63		56
Interest expense on lease liabilities	1		6		3		12
Total lease expense	$	85	$	89	$	174	$	177

Cash payment information:
Operating cash used for operating leases	$	48	$	55	$	99	$	109
Financing cash used for financing leases	33		20		51		28
Total cash paid for amounts included in the measurement of lease liabilities	$	81	$	75	$	150	$	137

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 June 30, 2020 are as follows in (thousands):


	Financing Leases			Operating Leases

Remaining 2020	$	72		$	106
2021	7			183
2022		—		123
2023		—		100
Thereafter		—		448
Total minimum lease payments	$	79		$	960
Less: amount representing interest		—			(232	)
Present value of obligations under leases	79				728
Less: current portion		(79	)		(139	)
Noncurrent lease obligations	$	—		$	589

Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Option Activity

A summary of activity for the six months ended June 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		(124	)	$	9,905.00
Outstanding as of June 30, 2020		531,741		$	10.24	$	—
Vested as of June 30, 2020		1,143		$	3,663.00	$	—
Vested and expected to be vested as of June 30, 2020		531,741		$	10.24	$	8,480

Basis of Presentation and New Accounting Standards (Details) $ / shares in Units, $ in Thousands					6 Months Ended
	Aug. 06, 2019 shares	Aug. 05, 2019 $ / shares shares	Apr. 25, 2019 USD ($)	Apr. 24, 2019 USD ($)	Jun. 30, 2020 USD ($) $ / shares shares	Jun. 30, 2019 USD ($)	Dec. 31, 2019 $ / shares shares
Basis Of Presentation And New Accounting Standards [Line Items]
Proceeds from sale of business					$ 0	$ 5,637
Reverse stock split effective date for trading purposes		Aug. 06, 2019
Reverse stock split of common stock		0.02
Reverse stock split of common stock description		Upon effectiveness, each 50 shares of issued and outstanding common stock were converted into one newly issued and outstanding share of common stock
Common stock, par value (in dollars per share) \| $ / shares		$ 0.001			$ 0.001		$ 0.001
Common stock, shares issued (in shares) \| shares	50,000,000	50,000,000			4,273,857		3,880,588
Common stock, shares outstanding (in shares) \| shares	50,000,000	50,000,000			4,273,857		3,880,588
Preferred stock, shares authorized (in shares) \| shares	5,000,000	5,000,000			5,000,000		5,000,000
Common stock, reverse stock split, fractional shares issued \| shares	0	0
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				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Liquidity [Abstract]
Net loss	$ 1,839	$ 1,087	$ 9,147	$ 3,150	$ 2,926	$ 12,297
Accumulated deficit	$ (428,196)				(428,196)		$ (425,270)
Net cash used in operating activities					$ (2,911)	$ (4,420)
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.

+ References + Details

Fair Value - Schedule of Estimated Fair Value Determined Using Option Pricing Model Assumptions (Details) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
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	9 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 2 months 12 days	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	2.12	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	2.12	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	0.17	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	0.25	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	119	168
Level 3 [Member] \| Expected Volatility [Member] \| Series U Warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants measurement input	142	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	0.82	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	1.64	1.94

Fair Value - Summary of Change in Level 3 Warrant Liability Value (Details) - Warrant Liability [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Warrant liability
Beginning balance	$ 5,262	$ 706	$ 6,929	$ 916
Change in fair value	(756)	(282)	(2,423)	(492)
Reclass to equity	(4,264)		(4,264)
Ending balance	$ 242	$ 424	$ 242	$ 424

Term Loan Obligations (Details) - USD ($) $ / shares in Units, $ in Thousands						3 Months Ended		6 Months Ended
	Mar. 29, 2020	Mar. 28, 2020	Apr. 29, 2019	Apr. 25, 2019	May 29, 2015	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Warrant exercise price (in dollars per share)						$ 2.25		$ 2.25
Interest expense						$ 252	$ 597	$ 601	$ 1,111
Non-cash amortization						$ 200	$ 100	$ 300	$ 300
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	Jun. 01, 2024	Jun. 01, 2021			Jun. 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	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Revenue Recognition [Abstract]
Development revenue and related costs	$ 0.2	$ 0.3

Discontinued Operations - Summary of Business Consideration to Calculation of the Loss on Sale (Details) - USD ($) $ in Thousands		6 Months Ended
	Apr. 25, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net cash proceeds		$ 0	$ 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	Jun. 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) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Discontinued Operations And Disposal Groups [Abstract]
Product revenue	$ 197	$ 901
Cost of revenue	199	857
Gross profit	(2)	44
Operating expenses:
Research and development	237	656
Sales and marketing	97	411
General and administrative	39	185
Total operating expenses	373	1,252
Operating loss	(375)	(1,208)
Other income (expense)	(5)	142
Loss from discontinued operations	$ (380)	$ (1,066)

Discontinued Operations - Summary of Non-Cash Adjustments Related to Discontinued Operations (Details) $ in Thousands	6 Months Ended
	Jun. 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	6 Months Ended
	Jun. 30, 2020	Jun. 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)	4,304,241	272,000
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)	531,741	2,000
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)	3,474,500	178,000
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)	298,000	92,000

Commitments and Contingencies - Additional Information (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)
Recorded Unconditional Purchase Obligation [Line Items]
Rent expense	$ 34,000	$ 129,000
Pre-clinical Research Study Obligations [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Contractual obligation	$ 34,000	$ 34,000
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	Jun. 30, 2020	Dec. 31, 2019
Assets
Operating	$ 707	$ 781
Financing	71
Total leased assets	778
Liabilities
Operating lease liabilities, current	139	147
Financing lease liabilities, current	79
Operating lease liabilities. noncurrent	589	$ 646
Total lease liabilities	$ 807
Weighted-average remaining lease term (years) - operating leases	6 years 7 months 9 days
Weighted-average remaining lease term (years) - finance leases	7 months 6 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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Lease expense:
Operating lease expense	$ 53	$ 55	$ 108	$ 109
Finance lease expense:
Depreciation of right-of-use assets	31	28	63	56
Interest expense on lease liabilities	1	6	3	12
Total lease expense	85	89	174	177
Cash payment information:
Operating cash used for operating leases	48	55	99	109
Financing cash used for financing leases	33	20	51	28
Total cash paid for amounts included in the measurement of lease liabilities	$ 81	$ 75	$ 150	$ 137

Commitments and Contingencies - Summary of Future Minimum Annual Lease Payments under Operating and Financing Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Leases
Remaining 2020	$ 72
2021	7
Total minimum lease payments	79
Present value of obligations under leases	79
Total minimum lease payments	79
Less: current portion	(79)
Operating Leases
Remaining 2020	106
2021	183
2022	123
2023	100
Thereafter	448
Total minimum lease payments	960
Less: amount representing interest	(232)
Present value of obligations under leases	728
Less: current portion	(139)	$ (147)
Noncurrent operating lease liability	$ 589	$ 646

NanoTx License Agreement - Additional Information (Details) - USD ($)	May 07, 2020	Jun. 30, 2020	Dec. 31, 2019	Aug. 06, 2019	Aug. 05, 2019
Common stock, shares issued (in shares)		4,273,857	3,880,588	50,000,000	50,000,000
Common stock, $0.001 par value; 100,000,000 shares authorized; 4,273,857 and 3,880,588 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively		$ 4,000	$ 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; 4,273,857 and 3,880,588 shares issued and outstanding at June 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	6 Months Ended		12 Months Ended
	Apr. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Aug. 06, 2019	Aug. 05, 2019
Preferred Stock [Abstract]
Preferred stock, shares authorized (in shares)		5,000,000		5,000,000	5,000,000	5,000,000
Preferred stock, par value (in dollars per share)		$ 0.001		$ 0.001
Preferred stock, shares outstanding (in shares)		1,959		1,959
Preferred stock, shares outstanding (in shares)		1,959		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%
Preferred stock, shares outstanding (in shares)		0		0
Series B Convertible Preferred Stock [Member]
Preferred Stock [Abstract]
Preferred stock, shares outstanding (in shares)		1,021		1,021
Preferred stock, shares outstanding (in shares)		1,021		1,021
Series B Convertible Preferred Stock [Member] \| 2018 Rights Offering [Member]
Preferred Stock [Abstract]
Preferred stock, shares outstanding (in shares)		1,021
Preferred stock, shares outstanding (in shares)		1,021
Number of preferred stock, shares converted			6,133
Series C Convertible Preferred Stock [Member]
Preferred Stock [Abstract]
Preferred stock, shares outstanding (in shares)		938		938
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
Preferred stock, shares outstanding (in shares)		938
Number of preferred stock, shares converted			291,920

Stockholders' Equity - Warrants (Details) - USD ($)			1 Months Ended	3 Months Ended			6 Months Ended
Stockholders' Equity - Warrants (Details) - USD ($)	Jul. 25, 2018	Jul. 17, 2018	Apr. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Class Of Stock [Line Items]
Warrant exercise price (in dollars per share)				$ 2.25			$ 2.25
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
Warrant liability				$ 242,000			$ 242,000		$ 6,929,000
Change in fair value of warrants				$ (756,000)	$ (282,000)		$ (2,423,000)	$ (492,000)
Outstanding Warrants [Member]
Class Of Stock [Line Items]
Class of warrant outstanding				3,362,500			3,362,500
Number of warrants exercised							3,362,500
Warrant liability				$ 4,300,000			$ 4,300,000
Change in fair value of warrants				$ 800,000
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
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				3,788,400			3,788,400
Number of warrants exercised							75,768
Series U Warrants [Member] \| Outstanding Warrants [Member]
Class Of Stock [Line Items]
Number of shares callable by warrants (in shares)				3,415,000			3,415,000

Stockholders' Equity - Common stock (Details) - USD ($)		3 Months Ended			6 Months Ended		12 Months Ended
Stockholders' Equity - Common stock (Details) - USD ($)	Sep. 21, 2018	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Class Of Stock [Line Items]
Sale of common stock, net		$ 64,000	$ 1,873,000
Common stock issued (in shares)					3,450,000
Proceeds from sale of common stock, net					$ 0	$ 1,984,000
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

Stock-based Compensation - Additional Information (Details) - USD ($) $ in Thousands		6 Months Ended
	Jun. 16, 2020	Jun. 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		$ 1,073,000
Weighted average period for recognition of cost		3 years 1 month 6 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)		210,030
2020 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Securities remaining and available for future issuances (in shares)		106,000
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)	6 Months Ended
	Jun. 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	(124)
Balance as of June 30, 2020 (in share) \| shares	531,741
Vested as of June 30, 2020 \| shares	1,143
Vested and expected to be vested as of June 30, 2020 \| shares	531,741
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	9,905.00
Balance as of June 30, 2020 (in dollars per share) \| $ / shares	10.24
Vested as of June 30, 2020 \| $ / shares	3,663.00
Vested and expected to be vested as of June 30, 2020 \| $ / shares	$ 10.24
Aggregate Intrinsic Value [Roll Forward]
Vested and expected to be vested as of June 30, 2020 \| $	$ 8,480