Company: PSTV
Filing Date: 2025-04-18
Form Type: 424B3
Source: 0000950170-25-055884
Chunk: 0

Company: PLUS THERAPEUTICS, INC.
Filing Date: 2025-04-18
Form: 424B3
Chunk 0
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Filed Pursuant to Rule 424(b)(3)
Registration No. 333-280061

PROSPECTUS SUPPLEMENT NO. 9

(To Prospectus dated June 24, 2024)

<div align='center'>Plus Therapeutics, Inc.</div>

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 filed with the Securities and Exchange Commission on April 18, 2025 (the “Current Report”). Accordingly, we have attached the Form 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 April 17, 2025, the closing price of our Common Stock was $0.66.

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.

<div align='center'>The date of this prospectus supplement is April 18, 2025</div>

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