Table of Contents As filed with the Securities and Exchange Commission on December 19, 2025. Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Aktis Oncology, Inc. (Exact name of registrant as specified in its charter) (State or other jurisdiction of Incorporation or organization Delaware 2834 85-2584233 (Primary Standard Industrial Classification Code Number) (I.R.S. Employer Identification No.) 17 ...