Sec Form 3 Filing - Larkin Hester Denise @ Radiopharm Theranostics Ltd - 2026-03-18

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Larkin Hester Denise 2. Issuer Name and Ticker or Trading Symbol Radiopharm Theranostics Ltd [ RADX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) SUITE 1 LEVEL 3, 62 LYGON STREET 3. Date of Earliest Transaction (MM/DD/YY) 03/18/2026 (Street) CARLTON SOUTH, VICTORIA3053 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Ordinary Shares 644,247 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Option (right to buy) $ 0.06 09/12/2024 08/24/2026 Ordinary Shares 275,000 D Option (right to buy) $ 0.06 09/30/2025 09/30/2029 Ordinary Shares 2,666,667 D Option (right to buy) $ 0.06 ( 1 ) 09/30/2029 Ordinary Shares 5,333,333 D Option (right to buy) $ 0.6 12/02/2022 12/01/2026 Ordinary Shares 627,001 D Option (right to buy) $ 0.6 11/16/2023 12/01/2026 Ordinary Shares 627,001 D Option (right to buy) $ 0.6 11/16/2024 12/01/2026 Ordinary Shares 627,000 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Larkin Hester Denise SUITE 1 LEVEL 3, 62 LYGON STREET CARLTON SOUTH, VICTORIA3053 X Signatures /s/ Hester Larkin 03/31/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Granted on December 16, 2024. 2,666,667 options will vest on September 30, 2026 and 2,666,666 options will vest on September 30, 2027 provided Ms. Larkin is still a Director on such dates.

Remarks: All exercise prices are in Australian dollars.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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