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SEC Form 3

FORM 3

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

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1. Name and Address of Reporting Person* GADICKE ANSBERT (Last) (First) (Middle) C/O MPM BIOIMPACT LLC 399 BOYLSTON STREET, SUITE 1100 (Street) BOSTON MA 02116 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 01/08/2026	3. Issuer Name and Ticker or Trading Symbol Aktis Oncology, Inc. [ AKTS ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	341,709	I	See Footnote(1)(2)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series Seed Redeemable Convertible Preferred Stock	(3)	(3)	Common Stock	1,314,262	$0(3)	I	See Footnote(1)(4)
Series A Redeemable Convertible Preferred Stock	(3)	(3)	Common Stock	5,914,197	$0(3)	I	See Footnote(1)(5)
Series B Redeemable Convertible Preferred Stock	(3)	(3)	Common Stock	1,577,119	$0(3)	I	See Footnote(1)(6)

1. Name and Address of Reporting Person* GADICKE ANSBERT (Last) (First) (Middle) C/O MPM BIOIMPACT LLC 399 BOYLSTON STREET, SUITE 1100 (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* MPM ASSET MANAGEMENT LLC (Last) (First) (Middle) C/O MPM BIOIMPACT LLC 399 BOYLSTON STREET, SUITE 1100 (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Oncology Impact Private Investment Fund 2, L.P. (Last) (First) (Middle) C/O MPM BIOIMPACT LLC 399 BOYLSTON STREET, SUITE 1100 (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. The Reporting Persons disclaim beneficial ownership of the securities except to the extent of his or its pecuniary interest therein.

2. The shares are held by MPM Asset Management LLC, of which Dr. Gadicke is the manager.

3. Each share of Series Seed Redeemable Convertible Preferred Stock, Series A Redeemable Convertible Preferred Stock and Series B Redeemable Convertible Preferred Stock is convertible into shares of the Issuer's Common Stock on a 3.8044-for-1 basis. Upon the closing of the Issuer's initial public offering, all shares of Series Seed Redeemable Convertible Preferred Stock, Series A Redeemable Convertible Preferred Stock and Series B Redeemable Convertible Preferred Stock will convert into shares of Common Stock of the Issuer. The Series Seed Redeemable Convertible Preferred Stock, Series A Redeemable Convertible Preferred Stock and Series B Redeemable Convertible Preferred Stock have no expiration date.

4. The shares are held as follows: 556,810 by MPM BioVentures 2018, L.P. ("BV 2018"), 29,593 by MPM BioVentures 2018 (B), L.P. ("BV 2018(B)"), 10,988 by MPM Asset Management Investors BV2018 LLC ("AM BV2018"), 119,478 by MPM Oncology Innovations Fund, L.P. ("MPM Oncology") and 597,393 by Oncology Impact Private Investment Fund 2, L.P. ("MPM Oncology Impact"). 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. Drs. Evnin and Gadicke are managing directors of BV 2018 LLC and managers of MPM Oncology Innovations Fund GP LLC, which is the general partner of MPM Oncology. Dr. Gadicke is the managing member of MPM Oncology Investments 2 LLC, which is the general partner of MPM Oncology Impact.

5. The shares are held as follows: 2,505,648 by BV 2018, 133,170 by BV 2018(B), 49,452 by AM BV2018, 537,654 by MPM Oncology and 2,688,273 by MPM Oncology Impact.

6. The shares are held as follows: 668,173 by BV 2018, 35,512 by BV 2018(B), 13,187 by AM BV2018, 143,374 by MPM Oncology and 716,873 by MPM Oncology Impact.

Remarks:

This filing is 1 of 2 identical filings due to limitations on number of Reporting Persons. See Form 3 filed by MPM BioVentures 2018, L.P.

	/s/ Ansbert Gadicke	01/08/2026
	/s/ Ansbert Gadicke, manager of MPM Asset Management LLC	01/08/2026
	/s/ Ansbert Gadicke, managing member of MPM Oncology Investments 2 LLC	01/08/2026
	/s/ Ansbert Gadicke, managing member of MPM Oncology Investments 2 LLC, the general partner of Oncology Impact Private Investment Fund 2, L.P.	01/08/2026
	** Signature of Reporting Person	Date
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