Sec Form 4 Filing - Foley Todd @ Aktis Oncology, Inc. - 2026-01-12

FORM 4 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 Foley Todd 2. Issuer Name and Ticker or Trading Symbol Aktis Oncology, Inc. [ AKTS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O MPM BIOIMPACT LLC, 399 BOYLSTON STREET, SUITE 1100 3. Date of Earliest Transaction (MM/DD/YY) 01/12/2026 (Street) BOSTON, MA02116 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 Common Stock 01/12/2026 C 597,391 ( 1 ) A 597,391 I See Footnote ( 3 ) ( 4 ) Common Stock 01/12/2026 C 2,688,270 ( 5 ) A 3,285,661 I See Footnote ( 3 ) ( 6 ) Common Stock 01/12/2026 C 716,872 ( 7 ) A 4,002,533 I See Footnote ( 3 ) ( 8 ) Common Stock 01/12/2026 P 232,870 ( 9 ) A $ 18 4,235,403 I See Footnote ( 3 ) ( 10 )

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 Series Seed Redeemable Convertible Preferred Stock ( 2 ) 01/12/2026 C 2,272,727 ( 2 ) ( 2 ) Common Stock 597,391 $ 0 ( 2 ) 0 I See Footnote ( 1 ) ( 3 ) Series A Redeemable Convertible Preferred Stock ( 2 ) 01/12/2026 C 10,227,273 ( 2 ) ( 2 ) Common Stock 2,688,270 $ 0 ( 2 ) 0 I See Footnote ( 3 ) ( 5 ) Series B Redeemable Convertible Preferred Stock ( 2 ) 01/12/2026 C 2,727,273 ( 2 ) ( 2 ) Common Stock 716,872 $ 0 ( 2 ) 0 I See Footnote ( 3 ) ( 7 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Foley Todd C/O MPM BIOIMPACT LLC 399 BOYLSTON STREET, SUITE 1100 BOSTON, MA02116 X X Signatures /sTodd Foley 01/14/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares of common stock were issued upon conversion as follows: 556,810 by MPM BioVentures 2018, L.P. ("BV 2018"), 29,593 by MPM BioVentures 2018 (B), L.P. ("BV 2018(B)") and 10,988 by MPM Asset Management Investors BV2018 LLC ("AM BV2018"). MPM BioVentures 2018 GP LLC and MPM BioVentures 2018 LLC ("BV2018 LLC") are the direct and indirect general partners of BV 2018 and BV 2018(B). BV 2018 LLC is the manager of AM BV2018. The Reporting Person is a managing director of BV 2018 LLC. ( 2 )Each share of Series Seed Redeemable Convertible Preferred Stock, Series A Redeemable Convertible Preferred Stock and Series B Redeemable Convertible Preferred Stock automatically converted into shares of the Issuer's Common Stock on a 3.8044-for-1 basis into the number of shares of Common Stock shown in Column 7 without payment of further consideration upon the closing of the initial public offering of the Issuer's Common Stock. The Series Seed Redeemable Convertible Preferred Stock, Series A Redeemable Convertible Preferred Stock and Series B Redeemable Convertible Preferred Stock had no expiration date. ( 3 )The Reporting Persons disclaim beneficial ownership of the securities except to the extent of his or its pecuniary interest therein. ( 4 )The shares are held as follows: 556,810 by BV 2018, 29,593 by BV 2018(B) and 10,988 by AM BV2018. ( 5 )The shares of common stock were issued upon conversion as follows: 2,505,648 by BV 2018, 133,170 by BV 2018(B) and 49,452 by AM BV2018. ( 6 )The shares are held as follows: 3,062,458 by BV 2018, 162,763 by BV 2018(B) and 60,440 by AM BV2018. ( 7 )The shares of common stock were issued upon conversion as follows: 668,173 by BV 2018, 35,512 by BV 2018(B) and 13,187 by AM BV2018. ( 8 )The shares are held as follows: 3,730,631 by BV 2018, 198,275 by BV 2018(B) and 73,627 by AM BV2018. ( 9 )The shares were purchased as follows: 219,897 by BV 2018, 8,689 by BV 2018(B) and 4,284 by AM BV2018. ( 10 )The shares are held as follows: 3,950,528 by BV 2018, 206,964 by BV 2018(B) and 77,911 by AM BV2018.

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

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