Exhibit 99.1 Boundless Bio Reports First Quarter 2024 Financial Results and Corporate Highlights BBI-355 Phase 1/2 POTENTIATE clinical trial ongoing; initiated targeted therapy combinations in patients with tumors with EGFR or FGFR oncogene amplifications First patient dosed in Phase 1/2 STARMAP clinical trial of BBI-825 in patients with tumors with resistance gene amplifications Completed $100 million IPO; pro forma cash position of approximately $200 million supports both BBI-355 and BBI-825 through preli ...

Table of Contents As filed with the Securities and Exchange Commission on March 21, 2024 Registration No. 333-277696 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO. 1 FORM S-1 REGISTRATION STATEMENT Under The Securities Act of 1933 BOUNDLESS BIO, INC. (Exact name of registrant as specified in its charter) Delaware 2834 83-0751369 (State or other jurisdiction of incorporation or organization) (Primary Standard Industrial Classification Code Number) (I.R.S. Employer Ident ...

Table of Contents As filed with the Securities and Exchange Commission on March 6, 2024 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT Under The Securities Act of 1933 BOUNDLESS BIO, INC. (Exact name of registrant as specified in its charter) (State or other jurisdiction of incorporation or organization) (Primary Standard Industrial Classification Code Number) Delaware 2834 83-0751369 (I.R.S. Employer Identification No.) 9880 Cam ...