PSTV Plus Therapeutics Inc

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrant  ☒                             Filed by a Party other than the Registrant  ☐

Check the appropriate box:

PLUS THERAPEUTICS, INC.

(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

VOTE BY INTERNET—www.proxyvote.com Use the Internet to transmit your voting instructions and for electronic delivery of information up until 11:59 P.M. ET on 05/16/2021. Have your proxy card in hand when you access the web site and follow the instructions to obtain your records and to create an electronic voting instruction form. During The Meeting—Go to www.virtualshareholdermeeting.com/PSTV2021 PLUS THERAPEUTICS, INC. C/O Broadridge You may attend the meeting via the Internet and vote during the meeting. Have the P.O. Box 1342 information that is printed in the box marked by the arrow available and follow the Brentwood, NY 11717 instructions. VOTE BY PHONE—1-800-690-6903 1 Use any touch-tone telephone to transmit your voting instructions up until 11:59 P.M. ET Investor Address Line 1 on 05/16/2021. Have your proxy card in hand when you call and then follow the Investor Address Line 2 instructions. Investor Address Line 3 1 1 OF Investor Address Line 4 VOTE BY MAIL Investor Address Line 5 Mark, sign and date your proxy card and return it in the postage-paid envelope we have John Sample provided or return it to Vote Processing, c/o Broadridge, 51 Mercedes Way, Edgewood, NY 11717. 1234 ANYWHERE STREET 2 ANY CITY, ON A1A 1A1 CONTROL # → NAME THE COMPANY NAME INC.—COMMON SHARES 123,456,789,012.12345 THE COMPANY NAME INC.—CLASS A 123,456,789,012.12345 THE COMPANY NAME INC.—CLASS B 123,456,789,012.12345 THE COMPANY NAME INC.—CLASS C 123,456,789,012.12345 THE COMPANY NAME INC.—CLASS D 123,456,789,012.12345 THE COMPANY NAME INC.—CLASS E 123,456,789,012.12345 THE COMPANY NAME INC.—CLASS F 123,456,789,012.12345 THE COMPANY NAME INC.—401 K 123,456,789,012.12345 PAGE 1 OF 2 TO VOTE, MARK BLOCKS BELOW IN BLUE OR BLACK INK AS FOLLOWS: x KEEP THIS PORTION FOR YOUR RECORDS THIS PROXY CARD IS VALID ONLY WHEN SIGNED AND DATED. DETACH AND RETURN THIS PORTION ONLY For Withhold For All To withhold authority to vote for any All All Except individual nominee(s), mark “For All Except” and write the number(s) of the The Board of Directors recommends you vote FOR 0 nominee(s) on the line below. 2 the following: 0 0 0 1. Election of Directors Nominees 0000000000 01) Richard J. Hawkins 02) Marc H. Hedrick, M.D. 03) An Van Es-Johansson 04) Greg Petersen 05) Howard Clowes 06) Robert Lenk The Board of Directors recommends you vote FOR proposals 2, 3 and 4. For Against Abstain 2. Ratification of the appointment of BDO USA, LLP as our independent registered public accounting firm for the 0 0 0 2021 fiscal year. 3. Approval of the amendment and restatement of the Plus Therapeutics, Inc. 2020 Stock Incentive Plan. 0 0 0 4. Non-binding advisory vote on compensation of our named executive officers. 0 0 0 NOTE: Transact such other business as may be properly brought before the meeting or any adjournment or postponement thereof. Investor Address Line 1 Investor Address Line 2 Investor Address Line 3 Investor Address Line 4 Investor Address Line 5 Please sign exactly as your name(s) appear(s) hereon. When signing as John Sample attorney, executor, administrator, or other fiduciary, please give full title as such. Joint owners should each sign personally. All holders must 1234 ANYWHERE STREET sign. If a corporation or partnership, please sign in full corporate or ANY CITY, ON A1A 1A1 partnership name by authorized officer. SHARES CUSIP # JOB # SEQUENCE # Signature [PLEASE SIGN WITHIN BOX] Date Signature (Joint Owners) Date 0000504378_1 R1.0.0.177

Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting: The Combined Document is available at www.proxyvote.com . PLUS THERAPEUTICS, INC. PROXY SOLICITED BY THE BOARD OF DIRECTORS FOR THE ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON MAY 17, 2021 The undersigned hereby appoints each of Marc H. Hedrick, M.D. and Andrew Sims, or either of them, as proxy holders each with full power of substitution, to appear on behalf and to vote all shares of common stock of Plus Therapeutics, Inc. (the “Company”) that the undersigned is entitled to vote at the Annual Meeting of Stockholders of the Company to be held virtually via live webcast at www.virtualshareholdermeeting.com/PSTV2021 on May 17, 2021, and at any postponement thereof. When properly executed, this proxy will be voted as directed. If properly executed and no instructions are specified, this proxy will be voted FOR the election of the listed Nominees as Directors under Proposal 1, FOR Proposals 2, 3 and 4, and at the discretion of the proxies with respect to such other business as may properly come before the meeting. The proxies, in their discretion, are further authorized to vote (a) for the election of a person to the Board of Directors if any nominee named herein becomes unable to serve or for good cause will not serve, (b) on any matter which the Board of Directors did not know would be presented at the Annual Meeting of Stockholders by a reasonable time before the proxy solicitation was made, and (c) on other matters which may properly come before the Annual Meeting of Stockholders and any adjournments or postponements thereof. This proxy, when properly executed, will be voted in the manner directed herein. If no such direction is made, this proxy will be voted in accordance with the Board of Director’s recommendations. PLEASE COMPLETE, DATE AND SIGN THIS PROXY AND RETURN IT IN THE ACCOMPANYING ENVELOPE. Continued and to be signed on reverse side 0000504378_2 R1.0.0.177