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Loss per Share - Schedule of Computation of Basic and Diluted Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Basic and diluted net loss per common share calculation:
Net loss	$ (2,940)	$ (3,261)	$ (1,482)	$ (4,805)	$ (6,201)	$ (6,287)
Change in fair value of warrants	(4,694)				(4,694)
Net loss attributable to common stockholders - diluted	$ (7,634)		$ (1,482)		$ (10,895)	$ (6,287)
Weighted average number of shares of common stock outstanding - basic	6,500,831		2,509,378		5,411,382	2,415,221
Net loss per share of common stock - basic	$ (0.45)		$ (0.59)		$ (1.15)	$ (2.60)
Weighted average number of shares of common stock outstanding - diluted	10,742,924		2,509,378		7,532,428	2,415,221
Net loss per share of common stock - diluted	$ (0.71)		$ (0.59)		$ (1.45)	$ (2.60)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

+ Details

- Definition

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

+ References

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+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders.

+ References + Details

Stockholders' Deficit	6 Months Ended
Jun. 30, 2024
Stockholders Equity Note [Abstract]
Stockholders' Deficit	12. Stockholders' Deficit Preferred Stock The Company has authorized 5,000,000 shares of preferred stock, par value $0.001 per share. The Company’s Board is authorized to designate the terms and conditions of any preferred stock the Company issues without further action by the common stockholders. Series F Preferred Stock On March 3, 2023, the Company filed a certificate of designation (the “Certificate of Designation”) with the Secretary of State of the State of Delaware, effective as of the time of filing, designating the rights, preferences, privileges and restrictions of the Series F Preferred Stock, with the total authorization of one (1) share of Series F Preferred Stock. The Certificate of Designation provided that the share of Series F Preferred Stock would have 50,000,000 votes per share of Series F Preferred Stock and would vote together with the Company’s common stock, as a single class exclusively with respect to any proposal to amend the Company’s Charter to effect the Reverse Stock Split. On March 3, 2023, the Company entered into a subscription and investment representation agreement with Richard J. Hawkins, chairman of the board of the Company, who is an accredited investor (the “Series F Preferred Stock Purchaser”), pursuant to which the Company agreed to issue and sell one (1) share of the Company’s Series F Preferred Stock, par value $0.001 per share, to the Series F Preferred Stock Purchaser for $1,000 in cash. The sale closed on March 3, 2023. The outstanding share of Series F Preferred Stock was redeemed in whole, automatically effective upon the approval by the Company’s stockholders of the Reverse Stock Split in April 2023. Upon such redemption, the holder of the Series F Preferred Stock received consideration of $1,000 in cash. Series B and C Preferred Stock As of June 30, 2024, there were 938 outstanding shares of Series C Preferred Stock that can be converted into an aggregate of 27,792 shares of common stock, and 1,014 shares of Series B Convertible Preferred Stock that can be converted into an aggregate of 398 shares of common stock. Warrants The Company issued pre-funded warrants and warrants to purchase its common stock in connection with the May 2024 Private Placement. See the section below on Common Stock for additional details. On September 25, 2019, the Company completed an underwritten public offering. The Company issued 19,266 shares of its common stock, along with pre-funded warrants to purchase 180,733 shares of its common stock and Series U Warrants to purchase 230,000 shares of its common stock. 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 5,000 shares of its common stock with a term of five years from the issuance date, in the form of Series U Warrants (the “Representative Warrants”). As of June 30, 2024, there were 142,733 outstanding Series U Warrants and Representative Warrants which can be exercised into an aggregate of 142,733 shares of common stock at a weighted average exercise price of $34.10 per share. Common Stock May 2024 Private Placement On May 5, 2024, the Company entered into a securities purchase agreement (the “Securities Purchase Agreement”) with certain investors, including certain of the Company’s directors and executive officers (“Company Insiders”) (collectively, the “Purchasers”), for the sale and issuance by the Company of its securities (the “Initial Subscription”). On May 8, 2024, the Company entered into a first amendment to the Securities Purchase Agreement (the “Amendment”) for the sale and issuance by the Company of additional securities to two of the Purchasers (the “Additional Subscription”, and together with the Initial Subscription, the “May 2024 Private Placement”). The Securities Purchase Agreement provides for the sale and issuance by the Company of an aggregate of 3,591,532 shares (the “Private Placement Shares”) of the Company’s common stock or, at the election of each Purchaser, pre-funded warrants (the “Pre-Funded Warrants”), exercisable immediately at an exercise price of $0.001 per share, with each Private Placement Share or Pre-Funded Warrant accompanied by (i) a Series A common warrant (“Series A Warrants”) to purchase one share of common stock (the “Series A Warrant Shares”), for an aggregate of 3,591,532 Series A Warrants, and (ii) one Series B common warrant (“Series B Warrants”) to purchase one share of common stock (the “Series B Warrant Shares,” and together with the Series A Warrant Shares, the “Common Warrant Shares”), for an aggregate of 3,591,532 Series B Warrants. The combined purchase price for each Private Placement Share and Pre-Funded Warrant from the Initial Subscription was $2.022, and $2.158 from the Additional Subscription, in each case together with one accompanying Series A Warrant and one accompanying Series B Warrant, provided, that the Company Insiders participated in the Initial Subscription at an offering price of $2.04 per Private Placement Share and accompanying Series A Warrant and Series B Warrant. The exercise price of Series A Warrants and Series B Warrants from the Initial Subscription is $1.772 per share and $1.908 per share in the Additional Subscription, provided that the exercise price for the Series A Warrants and Series B Warrants issued to the Company Insiders is $1.79 per share. Subject to certain ownership limitations, the Series A Warrants will be exercisable until the five-year anniversary of issuance. Subject to certain ownership limitations, the Series B Warrants will be exercisable until June 24, 2025. The Pre-Funded Warrant will not expire until exercised in full. If a holder of a Series A Warrant or a Series B Warrant is unable to exercise the warrant due to the limitation contained in the warrant that restricts the holder from owning above a specified beneficial ownership level (generally 4.99% or 9.99%) as the result of exercise of the warrant, then the holder may elect upon exercise of the warrant to receive a pre-funded warrant for the same number of shares of common stock that would otherwise have been received upon exercise of the warrant. In addition, the Series A Warrants and Series B Warrants provided for a call right starting June 24, 2025 in favor of the Company, if the volume-weighted average price of the common stock exceeds specified prices. The May 2024 Private Offering closed on May 9, 2024 (the “May 2024 Private Placement Closing”). The Company issued 2,151,544 Pre-Funded Warrants, 3,591,532 Series A Warrants and 3,591,532 Series B Warrants to purchase its common stock in connection with the May 2024 Private Placement. The aggregate gross proceeds from the May 2024 Private Placement Closing were approximately $7.3 million, before deducting $0.4 million of offering expenses. The Company reviewed the terms of the Pre-Funded Warrants, Series A Warrants and Series B Warrants under the authoritative accounting guidance. As described above, the Series A Warrants and Series B Warrants are classified as liabilities for the reason that they can be exercised into either common stock or Pre-Funded Warrants at the holder's option and thus fail the indexation guidance under ASC 815, Derivatives and Hedging. The Series A Warrant and Series B Warrant liability were recorded at fair value as of the issuance date and June 30, 2024, and under the terms of the Series A Warrants and Series B Warrants when issued that liability was subject to adjustment to estimated fair value at each balance sheet date until the warrants were settled. Refer to Note 14 for additional information regarding the amendment and restatement of the Series A Warrants and Series B Warrants that eliminated the ability of the Series A Warrants and Series B Warrants to be exercised into the Pre-Funded Warrants. The Pre-Funded Warrants are equity classified because they (1) are freestanding financial instruments that are legally detachable and separately exercisable from the common stock, (2) are immediately exercisable, (3) do not embody an obligation for the Company to repurchase its shares, (4) permit the holder to receive a fixed number of shares of common stock upon exercise, (5) are indexed to the Company's common stock and (6) meet the equity classification criteria. The proceeds from the May 2024 Private Placement must first be allocated to the full fair value of the Series A Warrants and Series B Warrants due to the liability classification. As disclosed in Note 4, the fair value of the Series A Warrants and Series B Warrants at issuance was $10.9 million. Under authoritative guidance, if the fair value of a warrant liability exceeds the proceeds received in an arm’s length transaction with no rights or privileges that require separate accounting recognition as an asset identified, then the warrant liability is recorded at fair value with the excess of fair value over proceeds recognized as a loss in earnings. The Company recognized approximately $3.5 million in financing expense in the condensed consolidated statement of operations during the three and six months ended June 30, 2024, which represents the excess of the fair value of the Series A Warrants and Series B Warrants at issuance over the proceeds. During the three and six months ended June 30, 2024, the Company recognized a fair value gain on warrant liability of $4.7 million. Proceeds from the May 2024 Private Placement are shown as cash from financing transactions and the gain on warrant liability is included as an adjustment to reconcile the net loss to net cash used in operating activities in the statements of cash flows for the six months ended June 30, 2024. In addition, total offering expenses related to the May 2024 Private Placement of $0.4 million were recorded as a component of other expenses as the entire proceeds were allocated to the warrant liability, which can be settled with either the Company’s common stock or Pre-Funded Warrants, which are exercisable into the Company’s common stock at any time at the holders’ option, but not in cash payment to the holders. All of the Pre-Funded Warrants, Series A Warrants, and Series B Warrants issued in connection with the May 2024 Private Placement remained outstanding as of June 30, 2024. Lincoln Park Purchase Agreement On August 2, 2022, the Company entered into a purchase agreement (the “2022 Purchase Agreement”) and registration rights agreement pursuant to which Lincoln Park Capital Fund (“Lincoln Park”) committed to purchase up to $50.0 million of the Company’s common stock. Under the terms and subject to the conditions of the 2022 Purchase Agreement, the Company has the right, but not the obligation, to sell to Lincoln Park, and Lincoln Park is obligated to purchase up to $50.0 million of the Company’s common stock. Such sales of common stock by the Company are subject to certain limitations, and can occur from time to time, at the Company’s sole discretion, over the 36-month period commencing on August 17, 2022, subject to the satisfaction of certain conditions. On May 16, 2022, the Company received stockholder approval for purposes of the Nasdaq listing rules to permit issuances of up to 57.5 million shares of the Company’s common stock (including the issuance of more than 19.99% of the Company’s common stock) to Lincoln Park, and it was pursuant to that approval that the Company entered into the 2022 Purchase Agreement. Upon execution of the 2022 Purchase Agreement, the Company paid $0.1 million in cash as the initial commitment fee, and issued 32,846 shares as the initial commitment shares, to Lincoln Park as consideration for its irrevocable commitment to purchase shares of the Company’s common stock at its direction under the 2022 Purchase Agreement. The Company has agreed to pay an additional commitment fee, which it may elect to pay in cash or shares of its common stock, or a combination of cash and shares of its common stock, upon receipt of $25.0 million aggregate gross proceeds from sales of common stock to Lincoln Park under the 2022 Purchase Agreement. On August 17, 2022, a registration statement (the “First Registration Statement”) was declared effective to cover the resale of up to 633,333 shares of the Company’s common stock comprised of (i) the 32,846 initial commitment shares, and (ii) up to 600,486 that the Company has reserved for issuance and sale to Lincoln Park under the 2022 Purchase Agreement from time to time from and after the date of the prospectus. The Company sold approximately 527,166 shares under the First Registration Statement. On August 18, 2023, a second registration statement (the “Second Registration Statement”) was declared effective to cover the resale of up to an additional 1,500,000 shares of the Company’s common stock that the Company reserved for issuance and sale to Lincoln Park under the 2022 Purchase Agreement from time to time. The Company sold 150,000 shares under the Second Registration Statement. The Company cannot sell more shares than registered under the Second Registration Statement under the 2022 Purchase Agreement without registering additional shares. Actual sales of shares of common stock to Lincoln Park under the 2022 Purchase Agreement depend on a variety of factors to be determined by the Company from time to time, including, among others, market conditions, the trading price of the common stock and determinations by the Company as to the appropriate sources of funding for the Company and its operations. The net proceeds under the 2022 Purchase Agreement to the Company depend on the frequency and prices at which the Company sells shares of its stock to Lincoln Park. During the period from August 17, 2022 to December 31, 2022, the Company issued 266,666 shares under the 2022 Purchase Agreement for net proceeds of approximately $3.2 million. The Company issued 410,500 shares under the 2022 Purchase Agreement for net proceeds of approximately $1.0 million from January 1, 2023 to December 31, 2023. The Company did not issue any common stock under the 2022 Purchase Agreement during the six months ended June 30, 2024. Share Repurchase Program and Treasury Stock On October 31, 2023, the Company announced that its Board has approved a share repurchase program (the “Share Repurchase Program”), with authorization to repurchase up to $500,000 of the outstanding shares of the Company’s common stock. The Company funded repurchases under the Share Repurchase Program with available cash. During the year ended December 31, 2023, the Company purchased 78,559 of its common stock for approximately $0.1 million as treasury stock. The Company purchased 179,866 of its common shares for approximately $0.4 million as treasury stock during the six months ended June 30, 2024. As of June 30, 2024, no amount remained authorized for repurchase.

Stockholders' Deficit

6 Months Ended

Jun. 30, 2024

Stockholders Equity Note [Abstract]

Stockholders' Deficit

12. Stockholders' Deficit

Preferred Stock

The Company has authorized 5,000,000 shares of preferred stock, par value $0.001 per share. The Company’s Board is authorized to designate the terms and conditions of any preferred stock the Company issues without further action by the common stockholders.

Series F Preferred Stock

On March 3, 2023, the Company filed a certificate of designation (the “Certificate of Designation”) with the Secretary of State of the State of Delaware, effective as of the time of filing, designating the rights, preferences, privileges and restrictions of the Series F Preferred Stock, with the total authorization of one (1) share of Series F Preferred Stock. The Certificate of Designation provided that the share of Series F Preferred Stock would have 50,000,000 votes per share of Series F Preferred Stock and would vote together with the Company’s common stock, as a single class exclusively with respect to any proposal to amend the Company’s Charter to effect the Reverse Stock Split. On March 3, 2023, the Company entered into a subscription and investment representation agreement with Richard J. Hawkins, chairman of the board of the Company, who is an accredited investor (the “Series F Preferred Stock Purchaser”), pursuant to which the Company agreed to issue and sell one (1) share of the Company’s Series F Preferred Stock, par value $0.001 per share, to the Series F Preferred Stock Purchaser for $1,000 in cash. The sale closed on March 3, 2023.

The outstanding share of Series F Preferred Stock was redeemed in whole, automatically effective upon the approval by the Company’s stockholders of the Reverse Stock Split in April 2023. Upon such redemption, the holder of the Series F Preferred Stock received consideration of $1,000 in cash.

Series B and C Preferred Stock

As of June 30, 2024, there were 938 outstanding shares of Series C Preferred Stock that can be converted into an aggregate of 27,792 shares of common stock, and 1,014 shares of Series B Convertible Preferred Stock that can be converted into an aggregate of 398 shares of common stock.

Warrants

The Company issued pre-funded warrants and warrants to purchase its common stock in connection with the May 2024 Private Placement. See the section below on Common Stock for additional details.

On September 25, 2019, the Company completed an underwritten public offering. The Company issued 19,266 shares of its common stock, along with pre-funded warrants to purchase 180,733 shares of its common stock and Series U Warrants to purchase 230,000 shares of its common stock. 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 5,000 shares of its common stock with a term of five years from the issuance date, in the form of Series U Warrants (the “Representative Warrants”). As of June 30, 2024, there were 142,733 outstanding Series U Warrants and Representative Warrants which can be exercised into an aggregate of 142,733 shares of common stock at a weighted average exercise price of $34.10 per share.

Common Stock

May 2024 Private Placement

On May 5, 2024, the Company entered into a securities purchase agreement (the “Securities Purchase Agreement”) with certain investors, including certain of the Company’s directors and executive officers (“Company Insiders”) (collectively, the “Purchasers”), for the sale and issuance by the Company of its securities (the “Initial Subscription”). On May 8, 2024, the Company entered into a first amendment to the Securities Purchase Agreement (the “Amendment”) for the sale and issuance by the Company of additional securities to two of the Purchasers (the “Additional Subscription”, and together with the Initial Subscription, the “May 2024 Private Placement”). The Securities Purchase Agreement provides for the sale and issuance by the Company of an aggregate of 3,591,532 shares (the “Private Placement Shares”) of the Company’s common stock or, at the election of each Purchaser, pre-funded warrants (the “Pre-Funded Warrants”), exercisable immediately at an exercise price of $0.001 per share, with each Private Placement Share or Pre-Funded Warrant accompanied by (i) a Series A common warrant (“Series A Warrants”) to purchase one share of common stock (the “Series A Warrant Shares”), for an aggregate of 3,591,532 Series A Warrants, and (ii) one Series B common warrant (“Series B Warrants”) to purchase one share of common stock (the “Series B Warrant Shares,” and together with the Series A Warrant Shares, the “Common Warrant Shares”), for an aggregate of 3,591,532 Series B Warrants.

The combined purchase price for each Private Placement Share and Pre-Funded Warrant from the Initial Subscription was $2.022, and $2.158 from the Additional Subscription, in each case together with one accompanying Series A Warrant and one accompanying Series B Warrant, provided, that the Company Insiders participated in the Initial Subscription at an offering price of $2.04 per Private Placement Share and accompanying Series A Warrant and Series B Warrant.

The exercise price of Series A Warrants and Series B Warrants from the Initial Subscription is $1.772 per share and $1.908 per share in the Additional Subscription, provided that the exercise price for the Series A Warrants and Series B Warrants issued to the Company Insiders is $1.79 per share. Subject to certain ownership limitations, the Series A Warrants will be exercisable until

the five-year anniversary of issuance. Subject to certain ownership limitations, the Series B Warrants will be exercisable until June 24, 2025. The Pre-Funded Warrant will not expire until exercised in full.

If a holder of a Series A Warrant or a Series B Warrant is unable to exercise the warrant due to the limitation contained in the warrant that restricts the holder from owning above a specified beneficial ownership level (generally 4.99% or 9.99%) as the result of exercise of the warrant, then the holder may elect upon exercise of the warrant to receive a pre-funded warrant for the same number of shares of common stock that would otherwise have been received upon exercise of the warrant.

In addition, the Series A Warrants and Series B Warrants provided for a call right starting June 24, 2025 in favor of the Company, if the volume-weighted average price of the common stock exceeds specified prices.

The May 2024 Private Offering closed on May 9, 2024 (the “May 2024 Private Placement Closing”). The Company issued 2,151,544 Pre-Funded Warrants, 3,591,532 Series A Warrants and 3,591,532 Series B Warrants to purchase its common stock in connection with the May 2024 Private Placement. The aggregate gross proceeds from the May 2024 Private Placement Closing were approximately $7.3 million, before deducting $0.4 million of offering expenses.

The Company reviewed the terms of the Pre-Funded Warrants, Series A Warrants and Series B Warrants under the authoritative accounting guidance.

As described above, the Series A Warrants and Series B Warrants are classified as liabilities for the reason that they can be exercised into either common stock or Pre-Funded Warrants at the holder's option and thus fail the indexation guidance under ASC 815, Derivatives and Hedging. The Series A Warrant and Series B Warrant liability were recorded at fair value as of the issuance date and June 30, 2024, and under the terms of the Series A Warrants and Series B Warrants when issued that liability was subject to adjustment to estimated fair value at each balance sheet date until the warrants were settled. Refer to Note 14 for additional information regarding the amendment and restatement of the Series A Warrants and Series B Warrants that eliminated the ability of the Series A Warrants and Series B Warrants to be exercised into the Pre-Funded Warrants.

The Pre-Funded Warrants are equity classified because they (1) are freestanding financial instruments that are legally detachable and separately exercisable from the common stock, (2) are immediately exercisable, (3) do not embody an obligation for the Company to repurchase its shares, (4) permit the holder to receive a fixed number of shares of common stock upon exercise, (5) are indexed to the Company's common stock and (6) meet the equity classification criteria.

The proceeds from the May 2024 Private Placement must first be allocated to the full fair value of the Series A Warrants and Series B Warrants due to the liability classification. As disclosed in Note 4, the fair value of the Series A Warrants and Series B Warrants at issuance was $10.9 million. Under authoritative guidance, if the fair value of a warrant liability exceeds the proceeds received in an arm’s length transaction with no rights or privileges that require separate accounting recognition as an asset identified, then the warrant liability is recorded at fair value with the excess of fair value over proceeds recognized as a loss in earnings. The Company recognized approximately $3.5 million in financing expense in the condensed consolidated statement of operations during the three and six months ended June 30, 2024, which represents the excess of the fair value of the Series A Warrants and Series B Warrants at issuance over the proceeds. During the three and six months ended June 30, 2024, the Company recognized a fair value gain on warrant liability of $4.7 million. Proceeds from the May 2024 Private Placement are shown as cash from financing transactions and the gain on warrant liability is included as an adjustment to reconcile the net loss to net cash used in operating activities in the statements of cash flows for the six months ended June 30, 2024.

In addition, total offering expenses related to the May 2024 Private Placement of $0.4 million were recorded as a component of other expenses as the entire proceeds were allocated to the warrant liability, which can be settled with either the Company’s common stock or Pre-Funded Warrants, which are exercisable into the Company’s common stock at any time at the holders’ option, but not in cash payment to the holders.

All of the Pre-Funded Warrants, Series A Warrants, and Series B Warrants issued in connection with the May 2024 Private Placement remained outstanding as of June 30, 2024.

Lincoln Park Purchase Agreement

On August 2, 2022, the Company entered into a purchase agreement (the “2022 Purchase Agreement”) and registration rights agreement pursuant to which Lincoln Park Capital Fund (“Lincoln Park”) committed to purchase up to $50.0 million of the Company’s common stock. Under the terms and subject to the conditions of the 2022 Purchase Agreement, the Company has the right, but not the obligation, to sell to Lincoln Park, and Lincoln Park is obligated to purchase up to $50.0 million of the Company’s common stock. Such sales of common stock by the Company are subject to certain limitations, and can occur from time to time,

at the Company’s sole discretion, over the 36-month period commencing on August 17, 2022, subject to the satisfaction of certain conditions.

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

Upon execution of the 2022 Purchase Agreement, the Company paid $0.1 million in cash as the initial commitment fee, and issued 32,846 shares as the initial commitment shares, to Lincoln Park as consideration for its irrevocable commitment to purchase shares of the Company’s common stock at its direction under the 2022 Purchase Agreement. The Company has agreed to pay an additional commitment fee, which it may elect to pay in cash or shares of its common stock, or a combination of cash and shares of its common stock, upon receipt of $25.0 million aggregate gross proceeds from sales of common stock to Lincoln Park under the 2022 Purchase Agreement.

On August 17, 2022, a registration statement (the “First Registration Statement”) was declared effective to cover the resale of up to 633,333 shares of the Company’s common stock comprised of (i) the 32,846 initial commitment shares, and (ii) up to 600,486 that the Company has reserved for issuance and sale to Lincoln Park under the 2022 Purchase Agreement from time to time from and after the date of the prospectus. The Company sold approximately 527,166 shares under the First Registration Statement.

On August 18, 2023, a second registration statement (the “Second Registration Statement”) was declared effective to cover the resale of up to an additional 1,500,000 shares of the Company’s common stock that the Company reserved for issuance and sale to Lincoln Park under the 2022 Purchase Agreement from time to time. The Company sold 150,000 shares under the Second Registration Statement. The Company cannot sell more shares than registered under the Second Registration Statement under the 2022 Purchase Agreement without registering additional shares.

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

During the period from August 17, 2022 to December 31, 2022, the Company issued 266,666 shares under the 2022 Purchase Agreement for net proceeds of approximately $3.2 million. The Company issued 410,500 shares under the 2022 Purchase Agreement for net proceeds of approximately $1.0 million from January 1, 2023 to December 31, 2023. The Company did not issue any common stock under the 2022 Purchase Agreement during the six months ended June 30, 2024.

Share Repurchase Program and Treasury Stock

On October 31, 2023, the Company announced that its Board has approved a share repurchase program (the “Share Repurchase Program”), with authorization to repurchase up to $500,000 of the outstanding shares of the Company’s common stock. The Company funded repurchases under the Share Repurchase Program with available cash.

During the year ended December 31, 2023, the Company purchased 78,559 of its common stock for approximately $0.1 million as treasury stock. The Company purchased 179,866 of its common shares for approximately $0.4 million as treasury stock during the six months ended June 30, 2024. As of June 30, 2024, no amount remained authorized for repurchase.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
-Paragraph 13
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 13
-Subparagraph (h)
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
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-Name Accounting Standards Codification
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org/505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 13
-Subparagraph (i)
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Use of Estimates	6 Months Ended
Jun. 30, 2024
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 consolidated 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 reviewing assets for impairment and determining the assumptions used in measuring stock-based compensation expense and warrant liability.

Use of Estimates

6 Months Ended

Jun. 30, 2024

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 consolidated 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 reviewing assets for impairment and determining the assumptions used in measuring stock-based compensation expense and warrant liability.

Loss per Share - Additional Information (Details)	Jun. 30, 2024 shares
May 2024 Private Placement [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Number of securities called by warrant or right	2,151,544

Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2024

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Option Activity

A summary of activity for the six months ended June 30, 2024 is as follows:


	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Balance as of December 31, 2023		140,109		$	37.48		8.07
Granted		196,824		$	2.09
Cancelled/expired		(5	)	$	271,125
Balance as of June 30, 2024		336,928		$	12.78		8.81	$	3,000
Vested and expected to vest at June 30, 2024		310,675		$	13.52		8.75	$	3,000
Exercisable at June 30, 2024		103,834		$	32.39		7.45	$	—

Basis of Presentation and New Accounting Standards - Additional Information (Details) $ / shares in Units, $ in Thousands				3 Months Ended	6 Months Ended
	Apr. 27, 2023	Apr. 21, 2023	Apr. 20, 2023 $ / shares	Jun. 30, 2024 USD ($) $ / shares shares	Jun. 30, 2024 USD ($) Segment $ / shares shares	Dec. 31, 2023 $ / shares shares	May 01, 2023 shares	Apr. 30, 2023 shares
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock, par value (in dollars per share) \| $ / shares			$ 0.001	$ 0.001	$ 0.001	$ 0.001
Stock split conversion ratio		0.06
Reverse stock split effective date	May 01, 2023
Common stock, shares issued (in shares)				5,962,644	5,962,644	4,522,656	2,500,000	37,400,000
Common stock, shares outstanding (in shares)				5,704,219	5,704,219	4,444,097	2,500,000	37,400,000
Preferred stock, shares authorized (in shares)				5,000,000	5,000,000	5,000,000
Common stock, reverse stock split, fractional shares issued					0
Stock issued during period reverse stock splits, shares					1,310
Number of operating segment \| Segment					1
Number of reportable segment \| Segment					1
Equity Incentive Plans [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock capital shares reserved for future issuance							200,000	3,000,000
Outstanding Warrants and Options [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock capital shares reserved for future issuance							100,000	2,000,000
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock split conversion ratio			0.33
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock split conversion ratio			0.06
Unrealized gain on available-for-sale securities \| $				$ 1,000	$ 1,000

Commitments and Contingencies - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023	Jul. 01, 2023	Mar. 31, 2023
Recorded Unconditional Purchase Obligation [Line Items]
Operating leases expiry year	2025
Operating lease right-of-use assets	$ 139,000	$ 202,000
Pre-clinical Research Study Obligations [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Contractual obligation	$ 0
Charlottesville [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Lessee, operating lease, term of contract	12 months
Lessee, operating lease, existence of option to extend [true false]	true
Lessee, operating lease, option to extend	The Charlottesville Lease has a term of 12 months and the Company has the ability to renew for three additional one-year periods.
Lessee, operating lease, renewal term	1 year
Lease liability				$ 80,000
Operating lease discount rate			13.47%	12.76%
Operating lease right-of-use assets			$ 19,000

Stock-based Compensation - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 06, 2024
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares to be issued (in shares)	196,824
Stock option contractual term	10 years
Stock option vesting percentage	25.00%
Total unamortized compensation cost related to outstanding unvested stock options and restricted stock awards	$ 0.7
Weighted average period for recognition of cost	2 years 3 months 18 days
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting period	2 years
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting period	4 years
2015 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Securities remaining and available for future issuances (in shares)	62,908	75,000
2020 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Securities remaining and available for future issuances (in shares)	1,899
Common stock shares to be issued (in shares)	236,667

Basis of Presentation and New Accounting Standards

6 Months Ended

Jun. 30, 2024

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Basis of Presentation and New Accounting Standards

1. Basis of Presentation and New Accounting Standards

The accompanying unaudited condensed consolidated financial statements for the three and six months ended June 30, 2024 and 2023 have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information. Accordingly, they do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for annual financial statements. The condensed balance sheet at December 31, 2023 has been derived from the audited financial statements at December 31, 2023, 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.

On May 17, 2024, Plus Therapeutics, Inc. (the “Company”) established a wholly owned subsidiary, CNSide Diagonistics, LLC (“CNSide LLC”), a Delaware limited liability company. CNSide LLC was set up to implement the Company’s business plan for developing the CNSide diagnostic portfolio alongside its lead radiotherapeutic candidate, rhenium (186Re) obisbemeda, using the intellectual property of Biocept, Inc. (“Biocept”) acquired by the Company in April 2024 (Note 8).

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 the Company and its wholly owned subsidiary have been included. Operating results for the three and six months ended June 30, 2024 are not necessarily indicative of the results that may be expected for the remainder of the year ending December 31, 2024. These condensed consolidated financial statements should be read in conjunction with the financial statements and notes therein included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023, filed with the Securities and Exchange Commission on March 5, 2024.

Amendments to Certificate of Incorporation and Reverse Stock Split

At the Annual Meeting of Stockholders of the Company held on April 20, 2023 (the “2023 Annual Meeting”), the stockholders of the Company approved an amendment to the Company’s Certificate of Incorporation, as amended (the “Charter”) to implement a reverse stock split of the Company’s then issued and outstanding common stock, par value $0.001 per share, with the ratio to be determined by the Board of Directors (the “Board”) of the Company, within a range of not less than 1-for-3 and not greater than 1-for-15. Subsequently, on April 21, 2023, the Board determined to fix the ratio for the reverse stock split at 1-for-15, without any change to its par value (the “Reverse Stock Split”).

On April 27, 2023, following stockholder and Board approval, the Company filed a Certificate of Amendment to its Charter (the “Amendment”), with the Secretary of State of the State of Delaware to effectuate the Reverse Stock Split. The Amendment became effective on May 1, 2023. Upon effectiveness of the Reverse Stock Split, the number of shares of the Company’s common stock (x) issued and outstanding decreased from approximately 37.4 million shares to approximately 2.5 million shares; (y) reserved for issuance upon exercise of outstanding warrants and options decreased from approximately 2.0 million shares to approximately 0.1 million shares, and (z) reserved but unallocated under the Company’s current equity incentive plans decreased from approximately 3.0 million shares of common stock to approximately 0.2 million shares of common stock. The Company’s common stock began trading on the Nasdaq Capital Market (“Nasdaq”) on a post-split basis on May 1, 2023. The Company’s 5,000,000 shares of authorized Preferred Stock were not affected by the Reverse Stock Split. No fractional shares were issued in connection with the Reverse Stock Split, and accordingly, the outstanding number of shares post Reverse Stock Split was adjusted down by approximately 1,310 (post-effect of the Reverse Stock Split) shares. Proportional adjustments for the Reverse Stock Split were made to the Company’s outstanding stock options, warrants and equity incentive plans for the period ended March 31, 2023 as presented in the condensed consolidated financial statements in this quarterly report on Form 10-Q. The Company’s consolidated financial statements, and all references thereto have been retroactively adjusted to reflect the Reverse Stock Split unless specifically stated otherwise.

Grant Revenue Recognition

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

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

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

Warrants

Warrants are accounted for as either derivative liabilities or as equity instruments depending on the specific terms of the agreement in accordance with applicable accounting guidance provided in ASC Topic 815 - Derivatives and Hedging. Equity-classified instruments are recorded in additional paid-in capital at issuance and are not subject to remeasurement. Liability-classified warrants are recorded at fair value at each reporting period with any change in fair value recognized as a component of change in fair value of derivative liabilities in the condensed consolidated statements of operations. The Company periodically evaluates changes in facts and circumstances that could impact the classification of warrants.

Segment Information

Prior to the establishment of CNSide LLC, the Company operated its business in one operating and reportable segment, which includes all activities related to the research and development of the Company’s research programs. From inception of CNSide LLC through June 30, 2024, the Company commenced certain set up and compliance activities of CNSide LLC with immaterial financial statement impact. The Company expects CNSide LLC to initiate commercial operations starting in the fourth quarter of 2024 related to laboratory testing, and that CNSide LLC will become a separate operating segment starting in the quarter ending December 31, 2024.

The Company’s chief operating decision-maker (“CODM”), the Chief Executive Officer, reviews the operating results including revenue and direct expenses of the Company’s operating segments for resource allocation and other management decisions.

Available-for-Sale Securities

The Company’s available-for-sale securities consist of U.S. government and agency securities. Securities with maturities from the date of purchase of less than three months are included in cash equivalents. The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the condensed consolidated balance sheets, with unrealized gains and losses, if any, reported as a component of other comprehensive income (loss) within the condensed consolidated statements of operations and comprehensive income/loss and as a separate component of stockholders’ equity. Realized gains and losses are calculated on the specific identification method and recorded as interest income (loss). At each balance sheet date, the Company assesses available-for-sale securities in an unrealized loss position to determine whether the decline in fair value below amortized cost is a result of credit losses or other factors, whether the Company expects to recover the amortized cost of the security, the Company’s intent to sell and if it is more likely than not that the Company will be required to sell the securities before the recovery of amortized cost. The Company records changes in allowance for expected credit loss in other income (expense). There has been no allowance for expected credit losses recorded during any of the periods presented.

Any premium arising at purchase is amortized to the earliest call date and any discount arising at purchase is accreted to maturity. Accretion of discounts are recorded in interest income in the condensed consolidated statements of operations and comprehensive income/loss.

During the three and six months ended June 30, 2024, the unrealized gain on the Company’s available-for-sale securities was less than $1,000, and not presented separately in the condensed consolidated statement of operations.

Recently Issued Accounting Pronouncements

In December 2023, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (ASU) No. 2023-09 Income Taxes (Topic 740): Improvements to Income Tax Disclosure. This ASU includes amendments that further enhance income tax disclosures, primarily through standardization and disaggregation of rate reconciliation categories and income taxes paid by jurisdiction. The ASU is effective for years beginning after December 15, 2024, but early adoption is permitted. This ASU should be applied on a prospective basis, although retrospective application is permitted. Management is currently evaluating the impact of the changes required by the new standard on the Company’s consolidated financial statements and related disclosures.

In November 2023, the FASB issued Accounting Standard Update (ASU) No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. The new standard is intended to improve annual and interim reportable segment disclosure requirements regardless of number of reporting units, primarily through enhanced disclosures of significant expenses. The amendment requires public entities to disclose significant segment expenses that are regularly provided

to the CODM and included within each reported measure of segment profit and loss. This update is effective for fiscal years beginning after December 15, 2023, and interim periods within those fiscal years starting after December 15, 2024. This ASU must be applied retrospectively to all prior periods presented. Management is currently evaluating the impact of the changes required by the new standard on the Company’s consolidated financial statements and related disclosures.

Term Loan Obligations - Additional Information (Details) - Term Loan [Member] - USD ($) $ in Millions		6 Months Ended
	May 29, 2015	Jun. 30, 2024	Jun. 03, 2024
Debt Instrument [Line Items]
Origination date		May 29, 2015
Original loan amount	$ 17.7
Maturity date	May 01, 2021
Fees amount associated with loan			$ 3.3

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 21: http://www.xbrl.org/2003/role/disclosureRef
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Reference 22: http://www.xbrl.org/2003/role/disclosureRef
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Reference 25: http://www.xbrl.org/2003/role/disclosureRef
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Reference 26: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 27: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details

Stockholders' Deficit - Preferred Stock (Details)		6 Months Ended
Stockholders' Deficit - Preferred Stock (Details)	Mar. 03, 2023 USD ($) Votes $ / shares shares	Jun. 30, 2024 $ / shares shares	Dec. 31, 2023 $ / shares shares	Apr. 20, 2023 $ / shares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)		5,000,000	5,000,000
Preferred stock, par value (in dollars per share) \| $ / shares		$ 0.001	$ 0.001
Preferred stock, shares outstanding (in shares)		1,952	1,952
Common stock, par value (in dollars per share) \| $ / shares		$ 0.001	$ 0.001	$ 0.001
Series B Convertible Preferred Stock [Member] \| 2018 Rights Offering [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)		1,014
Number of preferred stock, shares converted		398
Series C Convertible Preferred Stock [Member] \| 2018 Rights Offering [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (in shares)		938
Number of preferred stock, shares converted		27,792
Series F Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	1
Number Of Votes Per Share \| Votes	50,000,000
Consideration paid to preferred stock holders \| $	$ 1,000
Series F Convertible Preferred Stock [Member] \| Subscription Agreement [Member]
Class of Stock [Line Items]
Common stock, par value (in dollars per share) \| $ / shares	$ 0.001
Consideration to purchaser in cash \| $	$ 1,000
Issue and sale of share	1
Sale closed date	Mar. 03, 2023

Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2024	Aug. 09, 2024
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		5,896,333
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2024
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Shell Company	false
Trading Symbol	PSTV
Title of 12(b) Security	Common Stock, par value $0.001
Security Exchange Name	NASDAQ
Entity File Number	001-34375
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0827593
Entity Address, Address Line One	4200 MARATHON BLVD
Entity Address, Address Line Two	SUITE 200
Entity Address, City or Town	AUSTIN
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	78756
City Area Code	737
Local Phone Number	255-7194

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Operating expenses:
Research and development	$ 2,773	$ 1,420	$ 5,536	$ 4,403
General and administrative	2,203	1,924	4,416	4,169
Total operating expenses	4,976	3,344	9,952	8,572
Loss from operations	(3,697)	(1,490)	(6,996)	(6,212)
Other income (expense):
Financing expense	(3,545)		(3,545)
Change in fair value of warrants	4,694		4,694
Warrant issuance costs	(432)		(432)
Interest income	67	120	139	171
Interest expense	(27)	(112)	(61)	(246)
Total other income (expense)	757	8	795	(75)
Net loss	$ (2,940)	$ (1,482)	$ (6,201)	$ (6,287)
Per share information:
Net loss per share of common stock - basic	$ (0.45)	$ (0.59)	$ (1.15)	$ (2.60)
Weighted average number of shares of common stock outstanding - basic	6,500,831	2,509,378	5,411,382	2,415,221
Net loss per share of common stock - diluted	$ (0.71)	$ (0.59)	$ (1.45)	$ (2.60)
Weighted average number of shares of common stock outstanding - diluted	10,742,924	2,509,378	7,532,428	2,415,221
Grant [Member]
Revenue	$ 1,279	$ 1,854	$ 2,956	$ 2,360

Fair Value Measurements

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

Fair value measurements are market-based measurements, not entity-specific measurements. Therefore, fair value measurements are determined based on the assumptions that market participants would use in pricing the asset or liability. The Company follows

a three-level hierarchy to prioritize the inputs used in the valuation techniques to derive fair values. The basis for fair value measurements for each level within the hierarchy is described below:

•

Level 1: Quoted prices in active markets for identical assets or liabilities.

•

Level 2: Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets.

•

Level 3: Valuations derived from valuation techniques in which one or more significant inputs are unobservable in active markets.

Money market funds are valued at the closing price reported by the fund sponsor from an actively traded exchange. Money market funds and U.S. Treasury bills were included in cash equivalents in the consolidated balance sheets for the periods presented. The Company obtains the fair value of its Level 2 cash equivalents from third-party pricing services. The pricing services utilize industry standard valuation models whereby all significant inputs, including benchmark yields, reported trades, broker/dealer quotes, issuer spreads, bids, offers, or other market-related data, are observable.

The following table summarizes the Company’s fair value hierarchy for its financial assets measured at fair value on a recurring basis as of June 30, 2024 and December 31, 2023, respectively (in thousands).


	Fair Value Measurements Using
June 30, 2024	Fair Value		Level 1		Level 2		Level 3
Money market	$	2,415	$	2,415	$	—	$	—
Treasury bills and government agency bonds		3,523		—		3,523		—
	$	5,938	$	2,415	$	3,523	$	—

	Fair Value Measurements Using
December 31, 2023	Fair Value		Level 1		Level 2		Level 3
Money market	$	5,449	$	5,449	$	—	$	—

During the six months ended June 30, 2024, the Company issued common stock warrants which are classified as liabilities under authoritative accounting standards (Note 12). Those common stock warrants are valued using the Black Scholes model, with level 3 inputs such as expected volatility, risk-free interest rate, and expected term that are not observable in active markets.

The table below summarizes key inputs used in the valuation of the liability classified warrants as of the issuance date and as of June 30, 2024:


	As of issuance date	As of June 30, 2024
Expected term	1.1 - 5.0 years	1.0 to 4.8 years
Common stock market price	$2.01 - $2.27	$	1.47
Risk-free interest rate	4.5% - 5.1%	4.3% - 5.1%
Expected volatility	117.0% - 127.2%	105.6% - 121.0%

The table below provides a summary of the fair value of the Company's warrant liability during the six months ended June 30, 2024 (in thousands). As of June 30, 2023, the fair value of liability classified warrants was immaterial, and the change in the fair value of liability classified warrants during the three and six months ended June 30, 2023 was immaterial.


	Six Months Ended June 30,
Warrant liability	2024
Beginning balance	$	—
Issuance of warrants		10,854
Change in fair value of warrants		(4,694	)
Ending balance	$	6,160

Loss per Share (Tables)

6 Months Ended

Jun. 30, 2024

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss Per Common Share

The following table sets forth the computation of basic and diluted net loss per common share for the periods indicated, in thousands except share and per share data:


	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
Basic and diluted net loss per common share calculation:
Net loss	$	(2,940	)	$	(1,482	)	$	(6,201	)	$	(6,287	)
Change in fair value of warrants		(4,694	)		—			(4,694	)		—
Net loss attributable to common stockholders - diluted	$	(7,634	)	$	(1,482	)	$	(10,895	)	$	(6,287	)
Weighted average common shares outstanding - basic		6,500,831			2,509,378			5,411,382			2,415,221
Net loss per share of common stock - basic	$	(0.45	)	$	(0.59	)	$	(1.15	)	$	(2.60	)
Weighted average common shares outstanding - diluted		10,742,924			2,509,378			7,532,428			2,415,221
Net loss per share of common stock - diluted	$	(0.71	)	$	(0.59	)	$	(1.45	)	$	(2.60	)

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:


	As of June 30,
	2024		2023
Outstanding stock options		336,928		128,582
Preferred stock		28,190		28,190
Outstanding warrants		142,733		142,733
Total		507,851		299,505

Fair Value Measurements - Schedule of Changes in Fair Value of Warrant Liabilities (Details) - Warrant Liability [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2024 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 0
Issuance of warrants	10,854
Change in fair value of warrants	(4,694)
Ending Balance	$ 6,160

Subsequent Events - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
	Aug. 09, 2024	Jun. 30, 2024	Jun. 30, 2024
Subsequent Event [Line Items]
Gain on change in fair value of warrant liabilities		$ (4,694)	$ (4,694)
Series A Warrant [Member] \| Amendment and Restatements May 2024 Private Placement [Member] \| Common Stock [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Restricted Beneficial Ownership Level Result of Exercise of Warrant To Receive Pre-funded Warrant	4.99%
Series B Warrant [Member] \| Amendment and Restatements May 2024 Private Placement [Member] \| Common Stock [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Restricted Beneficial Ownership Level Result of Exercise of Warrant To Receive Pre-funded Warrant	9.99%

Loss per Share - Schedule of Antidilutive Securities Excluded from Diluted Income (Loss) per Share (Details) - shares	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
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)	507,851	299,505
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)	336,928	128,582
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)	28,190	28,190
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)	142,733	142,733

License Agreements - Additional Information (Details) - USD ($)		3 Months Ended		6 Months Ended
	Mar. 29, 2020	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Sep. 07, 2023
Research and development expense		$ 2,773,000	$ 1,420,000	$ 5,536,000	$ 4,403,000
Voting stock, value		6,000		6,000		$ 5,000
Biocept Agreement [Member]
Shares issued							53,381
Research and development expense				75,000
Nano Tx Licenses Agreement [Member]
License fee payment in cash	$ 400,000
Voting stock, value	$ 300,000
Percentage of non-dilutive monetary awards required to pay	15.00%
Accrued payments due to NanoTx		$ 500,000		$ 500,000

Biocept Asset Acquisitions

6 Months Ended

Jun. 30, 2024

Asset Acquisition [Abstract]

Biocept Asset Acquisitions

8. Biocept Asset Acquisitions

On April 26, 2024, the Company acquired from Biocept, for a total cash payment of $400,000, substantially all of the right, title and interest in CNSide intellectual property (“CNSide IP”), including (i) intellectual property, (ii) inventory and raw materials, and (iii) data, information, results and reports pertaining to the completed and on-going clinical studies involving the use of the CNSide IP (including, but not limited to, the FOERSEE clinical study that was being conducted by Biocept), related to the development, making, selling, and exporting or importing of the CNSideTM (as defined below), after having its bid accepted by the United States Bankruptcy Court for the District of Delaware.

The Company concluded that the acquisition of Biocept assets was not a business combination, as Biocept did not meet the definition of a business in ASC 805, Business Combination. The Company accounted for the asset purchase transaction under the authoritative guidance for asset acquisitions, and allocated the costs of acquisitions of approximately $45,000 among the assets acquired based on the relative fair value of such assets, which is predominately concentrated in the intellectual property acquired including patents and trademarks. The intangible assets acquired from Biocept are capitalized and amortized over a useful life of four years.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Cash flows used in operating activities:
Net loss	$ (2,940)	$ (3,261)	$ (1,482)	$ (4,805)	$ (6,201)	$ (6,287)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization					325	318
Amortization of deferred financing costs and debt discount					20	119
Share-based compensation expense					297	280
Accretion of discount on short-term investments					(23)
Non-cash financing expense					3,545
Change in fair value of warrants	(4,694)				(4,694)
Loss on disposal of property and equipment						2
Amortization of operating lease right-of-use assets					63	57
Increases (decreases) in cash caused by changes in operating assets and liabilities:
Grant receivable						718
Other current assets					335	1,510
Accounts payable and accrued expenses					360	(3,589)
Change in operating lease liabilities					(63)	(56)
Deferred grant liability					373	(1,643)
Net cash used in operating activities					(5,663)	(8,571)
Cash flows used in investing activities:
Purchases of property and equipment					(121)	(108)
Purchase of short-term investments					(3,500)
Purchase of intangible assets					(545)
Net cash used in investing activities					(4,166)	(108)
Cash flows provided by financing activities:
Principal payments of term loan obligation					(3,996)	(804)
Proceeds from credit facility					3,292
Purchase of treasury stock					(374)
Proceeds from sale of common stock, warrants and pre-funded warrants, net					7,265	2,258
Net cash provided by financing activities					6,187	1,454
Net decrease in cash and cash equivalents					(3,642)	(7,225)
Cash and cash equivalents at beginning of period		$ 8,554		$ 18,120	8,554	18,120	$ 18,120
Cash and cash equivalents at end of period	$ 4,912		$ 10,895		4,912	10,895	$ 8,554
Cash paid during period for:
Interest					32	135
Supplemental schedule of non-cash investing and financing activities:
Unpaid offering cost					$ 375	$ 35

Biocept Asset Acquisitions - Additional Information (Details) - Biocept Asset Acquisitions [Member]	Apr. 26, 2024 USD ($)
Asset Acquisition [Line Items]
Total cash payment	$ 400,000
Costs of acquisitions	$ 45,000

Liquidity and Going Concern - Additional Information (Details) - USD ($)			3 Months Ended				6 Months Ended
	May 09, 2024	Mar. 08, 2024	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net loss			$ (2,940,000)	$ (3,261,000)	$ (1,482,000)	$ (4,805,000)	$ (6,201,000)	$ (6,287,000)
Accumulated deficit			(486,702,000)				(486,702,000)		$ (480,501,000)
Aggregate upfront gross proceeds from private placement	$ 7,300,000
Net cash used in operating activities							$ (5,663,000)	$ (8,571,000)
Stockholders' equity requirement		$ 2,500,000	$ 1,000		$ 1,328,000	$ 895,000
Net income from continuing operations		500,000
Maintain minimum market value of listed securities		$ 35,000,000

- Definition

Amount after tax of income (loss) from continuing operations attributable to the parent.

+ References

+ Details

- Definition

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

+ References

+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

+ References + Details

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value on Recurring Basis


	Fair Value Measurements Using
June 30, 2024	Fair Value		Level 1		Level 2		Level 3
Money market	$	2,415	$	2,415	$	—	$	—
Treasury bills and government agency bonds		3,523		—		3,523		—
	$	5,938	$	2,415	$	3,523	$	—

	Fair Value Measurements Using
December 31, 2023	Fair Value		Level 1		Level 2		Level 3
Money market	$	5,449	$	5,449	$	—	$	—

Summary of Key Inputs Used in Valuation of Liability Classified Warrants

The table below summarizes key inputs used in the valuation of the liability classified warrants as of the issuance date and as of June 30, 2024:


	As of issuance date	As of June 30, 2024
Expected term	1.1 - 5.0 years	1.0 to 4.8 years
Common stock market price	$2.01 - $2.27	$	1.47
Risk-free interest rate	4.5% - 5.1%	4.3% - 5.1%
Expected volatility	117.0% - 127.2%	105.6% - 121.0%

Schedule of Changes in Fair Value of Warrant Liabilities


	Six Months Ended June 30,
Warrant liability	2024
Beginning balance	$	—
Issuance of warrants		10,854
Change in fair value of warrants		(4,694	)
Ending balance	$	6,160

Stock-based Compensation

6 Months Ended

Jun. 30, 2024

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

13. Stock-based Compensation

Under the Company’s 2015 New Employee Incentive Plan, as amended (the “2015 Plan”), awards may only be granted to employees who were not previously an employee or director of the Company, or following a bona fide period of non-employment, as a material inducement to entering into employment with the Company. On June 6, 2024, the Company’s Board increased the number of shares for future issuances under the 2015 Plan by 75,000 shares of common stock. As of June 30, 2024, there were 62,908 shares of common stock remaining and available for future issuances under the 2015 Plan.

The Company’s 2020 Stock Incentive Plan, as amended (the “2020 Plan”), which replaced the Company’s 2014 Equity Incentive Plan, provides for the award or sale of shares of common stock (including restricted stock), the award of stock units and stock appreciation rights, and the grant of both incentive stock options to purchase common stock to directors, officers, employees and consultants of the Company. The 2020 Plan provides for the issuance of up to 236,667 shares of common stock, plus the number of shares available for issuance is increased to the extent that awards granted under the 2020 Plan and the Company’s 2014 Equity

Incentive Plan are forfeited or expire (except as otherwise provided in the 2020 Plan). As of June 30, 2024, there were 1,899 shares remaining and available for future issuances under the 2020 Plan.

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

A summary of activity for the six months ended June 30, 2024 is as follows:


	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Balance as of December 31, 2023		140,109		$	37.48		8.07
Granted		196,824		$	2.09
Cancelled/expired		(5	)	$	271,125
Balance as of June 30, 2024		336,928		$	12.78		8.81	$	3,000
Vested and expected to vest at June 30, 2024		310,675		$	13.52		8.75	$	3,000
Exercisable at June 30, 2024		103,834		$	32.39		7.45	$	—

As of June 30, 2024, the total compensation cost related to non-vested stock options not yet recognized for all the Company’s plans is approximately $0.7 million, which is expected to be recognized as a result of vesting under service conditions over a weighted average period of 2.3 years.

Term Loan Obligations

6 Months Ended

Jun. 30, 2024

Debt Disclosure [Abstract]

Term Loan Obligations

5. Term Loan Obligations

On May 29, 2015, the Company entered into the Loan and Security Agreement (the “Loan and Security Agreement”), pursuant to which Oxford Finance, LLC (“Oxford”) funded an aggregate principal amount of $17.7 million (the “Term Loan”), subject to the terms and conditions set forth in the Loan and Security Agreement.

Pursuant to the Loan and Security Agreement, as amended, the Company made interest only payments through May 1, 2021, and thereafter was 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. On June 3, 2024, the Company paid off the Term Loan by making a final payment in an aggregate amount equal to approximately $3.3 million, which included both the balance of outstanding principal and interest and the final payment fee due. The repayment in full of the Term Loan terminated Oxford’s security interest in the Company’s existing and after-acquired assets, as well as all other certain restrictions and covenants under the Term Loan.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/470/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Details) - Recurring Basis [Member] - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 5,938
Money Market [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,415	$ 5,449
Treasury Bills and Government Agency Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,523
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,415
Level 1 [Member] \| Money Market [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,415	$ 5,449
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,523
Level 2 [Member] \| Treasury Bills and Government Agency Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 3,523

Fair Value Measurements - Summary of Key Inputs Used in Valuation of Liability Classified Warrants (Details) - Warrant Liability [Member]	Jun. 30, 2024	May 05, 2024
Expected Term [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, Expected term	1 year	1 year 1 month 6 days
Expected Term [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, Expected term	4 years 9 months 18 days	5 years
Common Stock Market Price [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, Measurement input	1.47
Common Stock Market Price [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, Measurement input		2.01
Common Stock Market Price [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, Measurement input		2.27
Risk-free Interest Rate [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, Measurement input	4.3	4.5
Risk-free Interest Rate [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, Measurement input	5.1	5.1
Expected Volatility [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, Measurement input	105.6	117
Expected Volatility [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, Measurement input	121	127.2

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Jun. 30, 2024	Dec. 31, 2023
Stockholders' deficit:
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	1,952	1,952
Preferred stock, shares outstanding (in shares)	1,952	1,952
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	5,962,644	4,522,656
Common stock, shares outstanding (in shares)	5,704,219	4,444,097
Treasury stock, shares	258,425	78,559

Stockholders' Deficit - Common stock (Details) - USD ($)					3 Months Ended			4 Months Ended	6 Months Ended	10 Months Ended	12 Months Ended	22 Months Ended
	May 09, 2024	May 05, 2024	Aug. 02, 2022	May 16, 2022	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2024	Oct. 31, 2023	Aug. 18, 2023	Aug. 17, 2022	Jul. 14, 2022
Class of Stock [Line Items]
Financing expense					$ 3,545,000				$ 3,545,000
Common stock, shares authorized (in shares)					100,000,000				100,000,000	100,000,000	100,000,000	100,000,000
Proceeds from private placement	$ 7,300,000
Fair value loss on warrant liability					$ (4,694,000)				$ (4,694,000)
Remained authorized amount for repurchase					$ 0				$ 0	$ 0		$ 0
Common Stock [Member]
Class of Stock [Line Items]
Issue and sale of share					1,439,988	472,674	168,164
Number of stock repurchased									179,866		78,559
Treasury stock					$ 400,000				$ 400,000	$ 400,000	$ 100,000	$ 400,000
Common Stock [Member] \| Maximum [Member]
Class of Stock [Line Items]
Authorized amount of repurchase of stock													$ 500,000
2022 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Maximum [Member]
Class of Stock [Line Items]
Common stock, shares authorized (in shares)				57,500,000
2022 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Maximum value of shares to be issued under agreement			$ 50,000,000
Issue and sale of share								266,666	0	150,000	410,500
Period exercisable from the date of issuance									36 months
Number of maximum common shares can be resale															633,333
Initial commitment shares			32,846													32,846
Initial commitment fee paid in cash			$ 100,000
Aggregate gross proceeds from sales of common stock			$ 25,000,000
Proceeds from sale of common stock, net								$ 3,200,000			$ 1,000,000
2022 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member] \| Minimum [Member]
Class of Stock [Line Items]
Percentage issuance of common stock				19.99%
2022 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member] \| Maximum [Member]
Class of Stock [Line Items]
Number of maximum common shares can be resale														1,500,000
Number of shares reserved for issuance and sale															600,486
2020 Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Issue and sale of share												527,166
May 2024 Private Placement [Member]
Class of Stock [Line Items]
Financing expense		$ 3,500,000
Fair value loss on warrant liability					$ 4,700,000				$ 4,700,000
May 2024 Private Placement [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Proceeds from issuance of warrants		$ 10,900,000
Proceeds from private placement	7,300,000
Offering expenses	$ 400,000
May 2024 Private Placement [Member] \| Common Stock [Member] \| Series A Warrant [Member]
Class of Stock [Line Items]
Number of shares issued	3,591,532	3,591,532
Restricted beneficial ownership level result of exercise of warrant to receive pre-funded warrant		4.99%
May 2024 Private Placement [Member] \| Common Stock [Member] \| Series A Warrant [Member] \| Initial Subscription [Member]
Class of Stock [Line Items]
Warrant exercise price (in dollars per share)		$ 1.772
May 2024 Private Placement [Member] \| Common Stock [Member] \| Series B Warrant [Member]
Class of Stock [Line Items]
Number of shares issued	3,591,532	3,591,532
Restricted beneficial ownership level result of exercise of warrant to receive pre-funded warrant		9.99%
May 2024 Private Placement [Member] \| Common Stock [Member] \| Series B Warrant [Member] \| Additional Subscription [Member]
Class of Stock [Line Items]
Warrant exercise price (in dollars per share)		$ 1.908
May 2024 Private Placement [Member] \| Common Stock [Member] \| Series A Warrant and Series B Warrant [Member]
Class of Stock [Line Items]
Warrant exercise price (in dollars per share)		1.79
May 2024 Private Placement [Member] \| Common Stock [Member] \| Series A Warrant and Series B Warrant [Member] \| Initial Subscription [Member]
Class of Stock [Line Items]
Offering price		2.04
May 2024 Private Placement [Member] \| Common Stock [Member] \| Pre-Funded Warrants [Member]
Class of Stock [Line Items]
Number of shares issued	2,151,544
May 2024 Private Placement [Member] \| Common Stock [Member] \| Securities Purchase Agreement [Member]
Class of Stock [Line Items]
Warrant exercise price (in dollars per share)		$ 0.001
Issue and sale of share		3,591,532
May 2024 Private Placement [Member] \| Common Stock [Member] \| Private Placement and Pre-Funded Warrant [Member] \| Initial Subscription [Member]
Class of Stock [Line Items]
Purchase price of share		$ 2.022
May 2024 Private Placement [Member] \| Common Stock [Member] \| Private Placement and Pre-Funded Warrant [Member] \| Additional Subscription [Member]
Class of Stock [Line Items]
Purchase price of share		$ 2.158

Line of Credit Facility - Additional Information (Details) - Pershing Credit Facility [Member] $ in Millions	May 31, 2024 USD ($)
Line of Credit Facility [Line Items]
Line of credit	$ 3.3
Percentage of credit facility cannot exceed collateralized marketable securities	91.50%
Debt instrument floor rate	5.50%
Basis variable rate	1.75%
Applicable fees	0.50%
Prime Rate [Member]
Line of Credit Facility [Line Items]
Basis variable rate	3.00%

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References + Details

Grant Revenue - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Sep. 19, 2022	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Grant [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized		$ 1,279	$ 1,854	$ 2,956	$ 2,360
CPRIT Contract [Member]
Disaggregation of Revenue [Line Items]
Grant funding term	3 years
CPRIT grant funding term, description				The CPRIT Grant is subject to customary CPRIT funding conditions, including, but not limited to, a matching fund requirement (one dollar for every two dollars awarded by CPRIT), revenue sharing obligations upon commercialization of rhenium (186Re) obisbemeda based on specific dollar thresholds and tiered low single digit royalty rates until CPRIT receives the aggregate amount of 400% of the proceeds awarded under the CPRIT Grant, and certain reporting requirements.
Contract effective date	Aug. 31, 2022
Contract termination date	Aug. 30, 2025
Percentage of aggregate amount of proceeds awarded under CPRIT grant	400.00%
Percentage of grant proceeds with interest not exceed annually	5.00%
CPRIT Contract [Member] \| Grant [Member]
Disaggregation of Revenue [Line Items]
Revenue recognized		$ 1,300	$ 1,900	$ 3,000	$ 2,400

Liquidity and Going Concern

6 Months Ended

Jun. 30, 2024

Liquidity [Abstract]

Liquidity and Going Concern

3. Liquidity and Going Concern

The Company incurred a net loss of $6.2 million for the six months ended June 30, 2024. The Company had an accumulated deficit of $486.7 million as of June 30, 2024. Additionally, the Company used net cash of $5.7 million to fund its operating activities for the six months ended June 30, 2024.

To date, the Company’s operating losses have been funded primarily from outside sources of invested capital from issuance of its common and preferred stocks, proceeds from its term loan, line of credit facility and grant funding. However, 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. There can be no assurance that the Company will be able to continue to raise additional capital in the future. The Company’s inability to raise additional cash would have a material and adverse impact on its operations and could cause the Company to default on its term loan. These factors raise substantial doubt about the Company’s ability to continue as a going concern.

At the closing of the May 2024 Private Placement, the Company received aggregate upfront gross proceeds of approximately $7.3 million, before deducting fees and other expenses associated with the closing of the May 2024 Private Placement. None of the Warrants issued in the May 2024 Private Placement have been exercised as of the filing of this quarterly report on Form 10-Q. See Note 12 to the unaudited condensed consolidated financial statements, Stockholders' Deficit - May 2024 Private Placement, for further information regarding the May 2024 Private Placement.

Nasdaq Listing Compliance

On March 8, 2024, the Company received a letter (the “Notice”) from the Listing Qualifications staff of Nasdaq, notifying the Company that it no longer complied with the requirement under Nasdaq Listing Rule 5550(b)(1) to maintain a minimum of $2.5 million in stockholders’ equity for continued listing on Nasdaq or the alternative requirements of having a market value of listed securities of $35 million or net income from continuing operations of $500,000 in the most recently completed fiscal year or two of the last three most recently completed fiscal years (the “Alternative Standards”). The Notice stated that as of March 8, 2024, the Company did not meet the Alternative Standards.

On April 22, 2024, the Company provided Nasdaq with its plan to achieve and sustain compliance with the stockholders’ equity requirement and requested that Nasdaq grant the Company an extension of time until September 4, 2024, to provide evidence of compliance with the stockholders’ equity requirement. Nasdaq has not yet responded to the Company’s plan, and there can be no assurance that Nasdaq will grant an extension or that the Company will be able to comply with the applicable listing standards of Nasdaq.

The Company continues to seek additional capital from financing alternatives and other sources in order to ensure adequate funding is available to allow the Company to continue research and product development and other operating activities at their current levels. If sufficient capital is not raised, the Company will at a minimum need to significantly reduce or curtail its research and development and other operations, and this would negatively affect its ability to achieve corporate growth goals.

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

The accompanying condensed consolidated 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.

Subsequent Events

6 Months Ended

Jun. 30, 2024

Subsequent Events [Abstract]

Subsequent Events

Amendment and Restatement of Series A Warrants and Series B Warrants

On August 9, 2024, the Company amended and restated the Series A Warrants and Series B Warrants (the “Amendment and Restatements”) issued in the May 2024 Private Placement. As described in Note 12 above, when originally issued, if a holder of a Series A Warrant or a Series B Warrant was unable to exercise the warrant due to the limitation contained in the Series A Warrants and Series B Warrants that restricted the holder from owning above a specified beneficial ownership level (generally 4.99% or 9.99%) as the result of exercise of the Series A Warrants and Series B Warrants, then the Series A Warrants and Series B Warrants holder could elect upon exercise of the Series A Warrants and Series B Warrants to receive a pre-funded warrant for the same number of shares of common stock that would otherwise have been received upon exercise of the Series A Warrants and Series B Warrants. The Series A Warrants and Series B Warrants Amendment and Restatements eliminated the ability of the holder to elect to purchase pre-funded warrants in lieu of the Series A Warrants and Series B Warrants.

In addition, the Amendment and Restatements eliminated the Company’s call right under the terms of the Series A Warrants to call the Series A Warrants after June 24, 2025, if the volume-weighted average price of the common stock exceeded specified prices. There were no other changes in the terms of the Series A Warrants and Series B Warrants.

As a result of the Amendment and Restatements, the Series A Warrants and Series B Warrants, as amended, will no longer fail the indexation guidance under ASC 815, Derivatives and Hedging, and the balance of the warrant liability at the amendment date will be reclassified to equity.

Basis of Presentation and New Accounting Standards (Policies)	6 Months Ended
	Jun. 30, 2024
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation and New Accounting Standards	The accompanying unaudited condensed consolidated financial statements for the three and six months ended June 30, 2024 and 2023 have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information. Accordingly, they do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for annual financial statements. The condensed balance sheet at December 31, 2023 has been derived from the audited financial statements at December 31, 2023, 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. On May 17, 2024, Plus Therapeutics, Inc. (the “Company”) established a wholly owned subsidiary, CNSide Diagonistics, LLC (“CNSide LLC”), a Delaware limited liability company. CNSide LLC was set up to implement the Company’s business plan for developing the CNSide diagnostic portfolio alongside its lead radiotherapeutic candidate, rhenium (186Re) obisbemeda, using the intellectual property of Biocept, Inc. (“Biocept”) acquired by the Company in April 2024 (Note 8). 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 the Company and its wholly owned subsidiary have been included. Operating results for the three and six months ended June 30, 2024 are not necessarily indicative of the results that may be expected for the remainder of the year ending December 31, 2024. These condensed consolidated financial statements should be read in conjunction with the financial statements and notes therein included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023, filed with the Securities and Exchange Commission on March 5, 2024.
Grant Revenue Recognition	Grant Revenue Recognition In applying the provisions of Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC 606”), the Company has determined that government grants are out of the scope of ASC 606 because the funding entities do not meet the definition of a “customer”, as defined by ASC 606, as the Company does not consider there to be a transfer of control of goods or services. With respect to each grant, the Company determines if it has a collaboration in accordance with ASC Topic 808, Collaborative Arrangements (“ASC 808”). For grants outside the scope of ASC 808, the Company applies International Accounting Standards No. 20 (“IAS 20”), Accounting for Government Grants and Disclosure of Government Assistance, by analogy, and revenue is recognized when the Company incurs expenses related to the grant for the amount the Company is entitled to under the provisions of the contract. The Company also considers the guidance in ASC Topic 730, Research and Development, which requires an assessment, at the inception of each grant, of whether each grant agreement is a liability. If the Company is obligated to repay funds received regardless of the outcome of the related research and development activities, then the Company is required to estimate and recognize that liability. Alternatively, if the Company is not required to repay the funds, then payments received are recorded as revenue or contra-expense as the expenses are incurred. Deferred grant liability represents grant funds received or receivable for which the allowable expenses have not yet been incurred as of the balance sheet date.
Warrants	Warrants Warrants are accounted for as either derivative liabilities or as equity instruments depending on the specific terms of the agreement in accordance with applicable accounting guidance provided in ASC Topic 815 - Derivatives and Hedging. Equity-classified instruments are recorded in additional paid-in capital at issuance and are not subject to remeasurement. Liability-classified warrants are recorded at fair value at each reporting period with any change in fair value recognized as a component of change in fair value of derivative liabilities in the condensed consolidated statements of operations. The Company periodically evaluates changes in facts and circumstances that could impact the classification of warrants.
Segment Information	Segment Information Prior to the establishment of CNSide LLC, the Company operated its business in one operating and reportable segment, which includes all activities related to the research and development of the Company’s research programs. From inception of CNSide LLC through June 30, 2024, the Company commenced certain set up and compliance activities of CNSide LLC with immaterial financial statement impact. The Company expects CNSide LLC to initiate commercial operations starting in the fourth quarter of 2024 related to laboratory testing, and that CNSide LLC will become a separate operating segment starting in the quarter ending December 31, 2024. The Company’s chief operating decision-maker (“CODM”), the Chief Executive Officer, reviews the operating results including revenue and direct expenses of the Company’s operating segments for resource allocation and other management decisions.
Available-for-Sale Securities	Available-for-Sale Securities The Company’s available-for-sale securities consist of U.S. government and agency securities. Securities with maturities from the date of purchase of less than three months are included in cash equivalents. The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the condensed consolidated balance sheets, with unrealized gains and losses, if any, reported as a component of other comprehensive income (loss) within the condensed consolidated statements of operations and comprehensive income/loss and as a separate component of stockholders’ equity. Realized gains and losses are calculated on the specific identification method and recorded as interest income (loss). At each balance sheet date, the Company assesses available-for-sale securities in an unrealized loss position to determine whether the decline in fair value below amortized cost is a result of credit losses or other factors, whether the Company expects to recover the amortized cost of the security, the Company’s intent to sell and if it is more likely than not that the Company will be required to sell the securities before the recovery of amortized cost. The Company records changes in allowance for expected credit loss in other income (expense). There has been no allowance for expected credit losses recorded during any of the periods presented. Any premium arising at purchase is amortized to the earliest call date and any discount arising at purchase is accreted to maturity. Accretion of discounts are recorded in interest income in the condensed consolidated statements of operations and comprehensive income/loss. During the three and six months ended June 30, 2024, the unrealized gain on the Company’s available-for-sale securities was less than $1,000, and not presented separately in the condensed consolidated statement of operations.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In December 2023, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (ASU) No. 2023-09 Income Taxes (Topic 740): Improvements to Income Tax Disclosure. This ASU includes amendments that further enhance income tax disclosures, primarily through standardization and disaggregation of rate reconciliation categories and income taxes paid by jurisdiction. The ASU is effective for years beginning after December 15, 2024, but early adoption is permitted. This ASU should be applied on a prospective basis, although retrospective application is permitted. Management is currently evaluating the impact of the changes required by the new standard on the Company’s consolidated financial statements and related disclosures. In November 2023, the FASB issued Accounting Standard Update (ASU) No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. The new standard is intended to improve annual and interim reportable segment disclosure requirements regardless of number of reporting units, primarily through enhanced disclosures of significant expenses. The amendment requires public entities to disclose significant segment expenses that are regularly provided to the CODM and included within each reported measure of segment profit and loss. This update is effective for fiscal years beginning after December 15, 2023, and interim periods within those fiscal years starting after December 15, 2024. This ASU must be applied retrospectively to all prior periods presented. Management is currently evaluating the impact of the changes required by the new standard on the Company’s consolidated financial statements and related disclosures.
Use of Estimates	Use of EstimatesThe 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 consolidated 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 reviewing assets for impairment and determining the assumptions used in measuring stock-based compensation expense and warrant liability.

- Definition

Disclosure of accounting policy for revenue from contract with customer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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-Name Accounting Standards Codification
-Section 50
-Paragraph 17
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+ Details

- Definition

Disclosure of accounting policy for segment reporting.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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+ Details

Commitments and Contingencies

6 Months Ended

Jun. 30, 2024

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

10. Commitments and Contingencies

Leases

The Company leases laboratory, office and storage facilities in San Antonio, Texas, under operating lease agreements that expire in 2025. The Company also leases certain office space in Austin, Texas under a month-to-month operating lease agreement and certain office space in Charlottesville, Virginia (the “Charlottesville Lease”). The Charlottesville Lease has a term of 12 months and the Company has the ability to renew for three additional one-year periods. On March 31, 2023, Company believed that it

was reasonably certain that the Charlottesville Lease will be renewed through March 31, 2026, and as a result, it remeasured the related lease liability as of March 31, 2023 to be $80,000 using the then-in-effect discount rate of 12.76%. Effective July 1, 2023, the Company added additional office lease premises in Charlottesville, which was accounted for as a separate operating lease contract with a lease liability and corresponding right-of-use asset of $19,000, as a discount rate of 13.47%.

Other commitments and contingencies

The Company has entered into agreements with various research organizations for pre-clinical and clinical development studies, which have provisions for cancellation. Under the terms of these agreements, the vendors provide a variety of services including conducting research, recruiting and enrolling patients, monitoring studies and data analysis. Payments under these agreements typically include fees for services and reimbursement of expenses. The timing of payments due under these agreements is estimated based on current study progress. As of June 30, 2024, the Company did not have any clinical research study obligations.

Legal proceedings

From time to time, the Company is subject to legal proceedings and claims, whether asserted or unasserted, that arise in the ordinary course of business. 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.

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' DEFICIT (UNAUDITED) - USD ($) $ in Thousands	Total	Series F Preferred Stock [Member]	Convertible Preferred Stock [Member]	Preferred Stock [Member]	Preferred Stock [Member] Series F Preferred Stock [Member]	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series F Preferred Stock [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2022	$ 6,445					$ 2		$ 473,628		$ (467,185)
Balance (in shares) at Dec. 31, 2022			1,952			2,240,092
Stock-based compensation	140							140
Sale and issuance of common stock, net	895	$ 1						895	$ 1
Sale and issuance of common stock, net (in shares)					1	168,164
Net loss	(4,805)									(4,805)
Balance at Mar. 31, 2023	2,676					$ 2		474,664		(471,990)
Balance (in shares) at Mar. 31, 2023			1,952	1		2,408,256
Balance at Dec. 31, 2022	6,445					$ 2		473,628		(467,185)
Balance (in shares) at Dec. 31, 2022			1,952			2,240,092
Net loss	(6,287)
Balance at Jun. 30, 2023	2,662					$ 3		476,131		(473,472)
Balance (in shares) at Jun. 30, 2023			1,952			2,879,620
Balance at Dec. 31, 2022	6,445					$ 2		473,628		(467,185)
Balance (in shares) at Dec. 31, 2022			1,952			2,240,092
Balance at Dec. 31, 2023	(1,348)					$ 5	$ (126)	479,274		(480,501)
Balance (in shares) at Dec. 31, 2023			1,952			4,522,656	(78,559)
Balance at Mar. 31, 2023	2,676					$ 2		474,664		(471,990)
Balance (in shares) at Mar. 31, 2023			1,952	1		2,408,256
Redemption of Series F preferred stock (in shares)					(1)
Stock-based compensation	140							140
Sale and issuance of common stock, net	1,328					$ 1		1,327
Sale and issuance of common stock, net (in shares)						472,674
Fractional adjustment						(1,310)
Net loss	(1,482)									(1,482)
Balance at Jun. 30, 2023	2,662					$ 3		476,131		(473,472)
Balance (in shares) at Jun. 30, 2023			1,952			2,879,620
Balance at Dec. 31, 2023	(1,348)					$ 5	$ (126)	479,274		(480,501)
Balance (in shares) at Dec. 31, 2023			1,952			4,522,656	(78,559)
Stock-based compensation	146							146
Purchase of treasury stock	(374)						$ (374)
Purchase of treasury stock (in Shares)							(179,866)
Net loss	(3,261)									(3,261)
Balance at Mar. 31, 2024	(4,837)					$ 5	$ (500)	479,420		(483,762)
Balance (in shares) at Mar. 31, 2024			1,952			4,522,656	(258,425)
Balance at Dec. 31, 2023	(1,348)					$ 5	$ (126)	479,274		(480,501)
Balance (in shares) at Dec. 31, 2023			1,952			4,522,656	(78,559)
Net loss	(6,201)
Balance at Jun. 30, 2024	(7,625)					$ 6	$ (500)	479,571		(486,702)
Balance (in shares) at Jun. 30, 2024			1,952			5,962,644	(258,425)
Balance at Mar. 31, 2024	(4,837)					$ 5	$ (500)	479,420		(483,762)
Balance (in shares) at Mar. 31, 2024			1,952			4,522,656	(258,425)
Stock-based compensation	151							151
Sale and issuance of common stock, net	1					$ 1
Sale and issuance of common stock, net (in shares)						1,439,988
Net loss	(2,940)									(2,940)
Balance at Jun. 30, 2024	$ (7,625)					$ 6	$ (500)	$ 479,571		$ (486,702)
Balance (in shares) at Jun. 30, 2024			1,952			5,962,644	(258,425)

Stock-based Compensation - Stock Option Activity (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Options [Roll Forward]
Balance as of December 31, 2023 (in shares)	140,109
Granted (in shares)	196,824
Cancelled/expired (in shares)	(5)
Balance as of June 30, 2024 (in shares)	336,928	140,109
Vested and expected to vest at June 30, 2024 (in shares)	310,675
Exercisable at June 30, 2024 (in shares)	103,834
Weighted Average Exercise Price [Roll Forward]
Balance as of December 31, 2023 (in dollars per share)	$ 37.48
Granted (in dollars per share)	2.09
Cancelled/expired (in dollars per share)	271,125
Balance as of June 30, 2024 (in dollars per share)	12.78	$ 37.48
Vested and expected to vest at June 30, 2024 (in dollars per share)	13.52
Exercisable at June 30, 2024 (in dollars per share)	$ 32.39
Weighted Average Remaining Contractual Life (years) [Roll Forward]
Balance as of June 30, 2024	8 years 9 months 21 days	8 years 25 days
Vested and expected to vest at June 30, 2024	8 years 9 months
Exercisable at June 30, 2024	7 years 5 months 12 days
Aggregated Intrinsic Value [Roll Forward]
Balance as of June 30, 2024	$ 3,000
Vested and expected to vest as of June 30, 2024	$ 3,000

Stockholders' Deficit - Warrants (Details) - $ / shares	3 Months Ended			6 Months Ended
Stockholders' Deficit - Warrants (Details) - $ / shares	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024
Series U Warrants [Member]
Class of Stock [Line Items]
Issue and sale of share				230,000
Warrants expected term	5 years			5 years
Representative Warrants [Member]
Class of Stock [Line Items]
Number of securities called by warrant or right	5,000			5,000
Common Stock [Member]
Class of Stock [Line Items]
Issue and sale of share	1,439,988	472,674	168,164
Warrants expected term	5 years			5 years
Outstanding Warrants [Member] \| Series U Warrants [Member]
Class of Stock [Line Items]
Warrant exercise price (in dollars per share)	$ 34.10			$ 34.10
Class of warrant outstanding	142,733			142,733
Number of warrants exercised				142,733
Common Class A [Member]
Class of Stock [Line Items]
Issue and sale of share				19,266
Common Class B [Member]
Class of Stock [Line Items]
Number of securities called by warrant or right	180,733			180,733

Loss per Share

6 Months Ended

Jun. 30, 2024

Earnings Per Share [Abstract]

Loss per Share

7. Loss per Share

Basic per share data is computed by dividing net income or loss applicable to common stockholders by the weighted average number of common shares outstanding during the period. Diluted per share data is computed by dividing net income or loss applicable to common stockholders by the weighted average number of common shares outstanding during the period increased to include, if dilutive, the number of additional common shares that would have been outstanding as calculated using the treasury stock method. Potential common shares were related to outstanding but unexercised options, multiple series of convertible preferred stock, and warrants for all periods presented.

The Company considers Series A Warrants and Series B Warrants issued in connection with the private placement completed in May 2024 (Note 12) to be participating securities because holders of such instruments participate in the event a dividend is paid on common stock. The holders of the Series A Warrants and Series B Warrants do not have a contractual obligation to share in the Company's losses. As such, losses are attributed entirely to common stockholders and for periods in which the Company has reported a net loss.

As of June 30, 2024, 2,151,544 Pre-Funded Warrants to purchase common stock, issued in connection with the May 2024 Private Placement (Note 12), were included in the basic and diluted net loss per share calculation.

The following table sets forth the computation of basic and diluted net loss per common share for the periods indicated, in thousands except share and per share data:


	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
Basic and diluted net loss per common share calculation:
Net loss	$	(2,940	)	$	(1,482	)	$	(6,201	)	$	(6,287	)
Change in fair value of warrants		(4,694	)		—			(4,694	)		—
Net loss attributable to common stockholders - diluted	$	(7,634	)	$	(1,482	)	$	(10,895	)	$	(6,287	)
Weighted average common shares outstanding - basic		6,500,831			2,509,378			5,411,382			2,415,221
Net loss per share of common stock - basic	$	(0.45	)	$	(0.59	)	$	(1.15	)	$	(2.60	)
Weighted average common shares outstanding - diluted		10,742,924			2,509,378			7,532,428			2,415,221
Net loss per share of common stock - diluted	$	(0.71	)	$	(0.59	)	$	(1.45	)	$	(2.60	)

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


	As of June 30,
	2024		2023
Outstanding stock options		336,928		128,582
Preferred stock		28,190		28,190
Outstanding warrants		142,733		142,733
Total		507,851		299,505

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 4,912	$ 8,554
Investments	3,523
Other current assets	945	1,280
Total current assets	9,380	9,834
Property and equipment, net	732	906
Operating lease right-of-use assets	139	202
Goodwill	372	372
Intangible assets, net	557	42
Other assets	32	32
Total assets	11,212	11,388
Current liabilities:
Accounts payable and accrued expenses	6,946	6,631
Operating lease liability	92	120
Warrant liability	6,160
Deferred grant liability	2,297
Line of credit	3,292
Term loan obligation, current		3,976
Total current liabilities	18,787	10,727
Noncurrent operating lease liability	50	85
Deferred grant liability		1,924
Total liabilities	18,837	12,736
Commitments and contingencies (Note 10)
Stockholders' deficit:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 1,952 shares issued and outstanding at June 30, 2024 and December 31, 2023, respectively
Common stock, $0.001 par value; 100,000,000 shares authorized; 5,962,644 and 5,704,219 issued and outstanding at June 30, 2024, and 4,522,656 issued and 4,444,097 outstanding as of December 31, 2023, respectively	6	5
Treasury stock (at cost, 258,425 and 78,559 shares as of June 30, 2024 and December 31, 2023, respectively)	(500)	(126)
Additional paid-in capital	479,571	479,274
Accumulated deficit	(486,702)	(480,501)
Total stockholders' deficit	(7,625)	(1,348)
Total liabilities and stockholders' deficit	$ 11,212	$ 11,388

Grant Revenue

6 Months Ended

Jun. 30, 2024

Revenue from Contract with Customer [Abstract]

Grant Revenue

9. Grant Revenue

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

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

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

The Company recognized $1.3 million and $1.9 million, and $3.0 million and $2.4 million in grant revenue from the CPRIT Contract during the three and six months ended June 30, 2024 and 2023, 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
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-9

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-10

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-15

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-12

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-13

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org/606/tableOfContent

+ Details

Line of Credit Facility

6 Months Ended

Jun. 30, 2024

Line of Credit Facility [Abstract]

Line of Credit Facility

6. Line of Credit Facility

On May 31, 2024, the Company drew down $3.3 million on its new margin loan facility under a line of credit (the “Pershing Credit Facility”) with Pershing LLC (“Pershing”), an affiliate of The Bank of New York Mellon Corporation. The available credit line limit under the Pershing Credit Facility fluctuates based on the Company’s request for extensions from time to time, subject to the value of the collateralized marketable securities the Company holds with Pershing, provided that the amount available to draw under the Pershing Credit Facility cannot exceed 91.5% of the value of the collateralized marketable securities deposited with Pershing. Depending on the value of the marketable securities the Company holds with Pershing, Pershing may require the Company from time-to-time to deposit additional funds or marketable securities in order to restore the level of collateral to an acceptable level. The amounts borrowed under the Pershing Credit Facility are due on demand.

Borrowings under the Pershing Credit Facility bear interest at the target interest rate set by the Federal Open Market Committee, subject to a floor of 5.5%, plus a spread of 1.75% and applicable fees of 0.5%, subject to a maximum interest rate of the then applicable Prime Rate as published in The Wall Street Journal plus 3.0%. Interest payments thereunder are calculated on a monthly basis and, unless paid, are added to the outstanding balance under the Pershing Credit Facility. The proceeds under the Pershing Credit Facility are available for working capital needs and other general corporate purposes. Volatility in the global markets could cause the interest rate to fluctuate from time to time increasing the Company’s costs, or could cause Pershing to terminate the Company’s ability to borrow funds. In addition, borrowings under the Pershing Credit Facility have the effect of limiting the Company’s use of cash and marketable securities.

License Agreements

6 Months Ended

Jun. 30, 2024

License Agreement [Abstract]

License Agreements

11. License Agreements

Biocept License Agreement

On September 7, 2023, the Company entered into a Non-Exclusive License and Services Agreement with Biocept, pursuant to which Biocept granted the Company a non-exclusive license to use the Biocept proprietary cell enumeration test, CNSideTM (“CNSideTM”). In exchange for the license, the Company issued to Biocept 53,381 unregistered shares, the fair value of which was $75,000.

On October 16, 2023, Biocept filed a voluntary petition for relief under the provisions of Chapter 7 of Title 11 of the United States Bankruptcy Code. See Note 8 for further information regarding the Company’s acquisition of substantially all right, title and interest in the CNSide IP.

University of Texas Health Science Center at San Antonio (“UTHSCSA”) License Agreement

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

NanoTx License Agreement

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

The transaction terms included an upfront payment of $0.4 million in cash and $0.3 million in the Company’s voting stock. The transaction terms also included success-based milestone and royalty payments contingent on key clinical, regulatory and sales milestones, as well as the requirement to pay 15% of any non-dilutive monetary awards or grants received from external agencies to support product development of the nanoliposome encapsulated BMEDA-chelated radioisotope, which includes grants from CPRIT. As of June 30, 2024, the Company accrued $0.5 million of payments due to NanoTx as a result of the CPRIT grant received (see Note 9, Grant Revenue of the condensed consolidated financial statements for additional information).