Filed Pursuant to Rule 424(b)(3)

Registration No. 333-280061

PROSPECTUS SUPPLEMENT NO.3

(To Prospectus dated June 24, 2024)

Plus Therapeutics Inc.

This prospectus supplement updates and supplements the prospectus, dated June 24, 2024 (as supplemented to date, the “Prospectus”), which forms a part of our registration statement on Form S-1 (No. 333-280061). This prospectus supplement is being filed to update and supplement the information in the Prospectus with the information contained in our Current Report on Form 8-K filed with the Securities and Exchange Commission on September 6, 2024 (the “Current Report”). Accordingly, we have attached the Form 8-K to this prospectus supplement.

This prospectus supplement should be read in conjunction with the Prospectus, which is to be delivered with this prospectus supplement, and is qualified by reference thereto, except to the extent that the information in this prospectus supplement updates or supersedes the information contained in the Prospectus. Please keep this prospectus supplement with your Prospectus for future reference.

Our common stock, par value $0.001 per share (“Common Stock”), is listed on The Nasdaq Capital Market LLC under the symbol “PSTV”. On September 5, 2024, the closing price of our Common Stock was $1.375.

We are a “smaller reporting company” for purposes of federal securities laws and are subject to reduced public company reporting requirements. Accordingly, the information in the Prospectus and this prospectus supplement may not be comparable to information provided by companies that are not smaller reporting companies.

Our business and investment in our Common Stock involve significant risks. These risks are described in the section titled “Risk Factors” beginning on page 13 of the Prospectus, and under similar headings in any amendments or supplements to the Prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of the Prospectus or this prospectus supplement. Any representation to the contrary is a criminal offense.

The date of this prospectus supplement is September 6, 2024.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 8-K

Current Report

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 5, 2024

PLUS THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

4200 Marathon Blvd., Suite 200, Austin, Texas 78756

(Address of principal executive offices, with zip code)

(737) 255-7194

(Registrant’s telephone number, including area code)

N/A

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instructions A.2. below):

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

As previously disclosed, on March 8, 2024, Plus Therapeutics, Inc. (the “Company”) received a written notice (the “Notice”) from the Listing Qualifications staff of The Nasdaq Stock Market (“Nasdaq”) notifying the Company that it no longer complies with the requirement under Nasdaq Listing Rule 5550(b)(1) to maintain a minimum of $2.5 million in stockholders’ equity (the “Minimum Stockholders’ Equity Requirement”) for continued listing on The Nasdaq Capital Market 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 the Company’s Form 10-K for the year ended December 31, 2023, disclosed stockholders’ equity of ($1,348,000) as of December 31, 2023, and that, as of March 8, 2024, the Company did not meet the Alternative Standards. As required by Nasdaq, the Company submitted its plan to regain compliance with the Minimum Stockholders’ Equity Requirement on April 22, 2024.

On September 5, 2024, the Company received a letter from Nasdaq (the “Letter”) notifying the Company that it had not regained compliance with Nasdaq Listing Rule 5550(b)(1) and that, as a result, unless the Company timely requests an appeal of this determination to a Nasdaq Hearings Panel, Nasdaq would move to suspend trading of the Company’s common stock and to have the Company’s shares of common stock, par value $0.001 per share, delisted from The Nasdaq Capital Market. Accordingly, the Company intends to timely appeal the determination, which will automatically stay any suspension or delisting action pending the Hearings Panel’s decision and the expiration of any additional extension period granted by the Hearings Panel following the hearing. As a result, the Company’s shares of common stock is expected to remain listed on The Nasdaq Capital Market through at least that time. There can be no assurance, however, that the Hearings Panel will grant the Company’s request for continued listing or that the Company will be able to demonstrate compliance with Nasdaq Listing Rule 5550(b)(1) within any additional compliance period that may be granted by the Hearings Panel.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: September 6, 2024