Material Event (Form 8-K)

On August 22, 2025, Plus Therapeutics, Inc. (the "Company") received a letter (the "Letter") from The Nasdaq Stock Market LLC ("Nasdaq") confirming its compliance with Nasdaq Listing Rule 5550(b). Specifically, the Letter confirms that the Company is in compliance with both (1) the Market Value of Listing Securities ("MVLS") standard under 5550(b)(2), which requires certain companies to maintain a market value of listed securities of at least $35 million (the "MVLS Standard"), as well as compliance with (2) the alternative stockholders' equity threshold under 5550(b)(1), which requires certain companies to maintain stockholders' equity of at least $2.5 million (the "Equity Standard"). Accordingly, the Company now satisfies two alternative criteria under Nasdaq Listing Rule 5550.

As a result of such compliance, Nasdaq has permitted the Company the remainder of the previously announced grace period to regain compliance with the $1.00 bid price rule under Nasdaq Listing Rule 5550(a)(2) (the "Bid Price Rule"), through November 12, 2025. Nasdaq previously required that the Company remedy the bid price deficiency by September 8, 2025, a deadline that no longer applies.

The Letter also provides that, solely with respect to the Equity Standard, the Company remains subject to a one-yearpanel monitoring period, through August 22, 2026. If, within that one-yearmonitoring period, Nasdaq's Listing Qualifications Staff (the "Staff") determines that the Company no longer satisfies the Equity Standard (and the Company is not then in compliance with one of the alternative standards under Rule 5550(b), such as the MVLS Standard), the Company will not be permitted to provide the Staff with a plan of compliance and the Staff is not permitted to grant additional time to regain compliance with the Equity Standard nor will the Company be afforded an applicable cure or compliance period. Instead, the Staff will issue a delist determination letter, and the Company will have an opportunity to request a new hearing before the Nasdaq Hearings Panel, which request would stay any further action by the Staff pending the ultimate outcome of the hearing.