Exhibit 99.1 Boundless Bio Provides Business Updates Focused on Key Value Drivers and Reports Second Quarter 2024 Financial Results BBI-355 POTENTIATE clinical trial ongoing with initiatives implemented to expedite enrollment in combination cohorts; initial proof-of-concept data now expected in the second half of 2025 BBI-825 STARMAP clinical trial ongoing with initial proof-of-concept data expected in the second half of 2025 ECHO ecDNA diagnostic analytically validated and IRB-approved for use as a clinica ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 Title of each class Trading Symbol(s) Name of each exchange on which registered Common stock, par value $0.0001 per share BOLD Nasdaq Global Select Market FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from ______ ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 Title of each class Trading Symbol(s) Name of each exchange on which registered Common stock, par value $0.0001 per share BOLD Nasdaq Global Select Market FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from _____ ...

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 ...