Boundless Bio (BOLD) Status Update summary

Portfolio prioritization and clinical strategy

• Discontinued all current arms of the BBI-355 POTENTIATE trial, including monotherapy and combinations with EGFR, FGFR, and CDK4/6 inhibitors, due to clinical and market considerations.

• Initiating a new POTENTIATE trial arm to evaluate BBI-355 in combination with BBI-825 for oncogene-amplified tumors, leveraging preclinical synergy and improved safety profile.

• Declared BBI-940, a novel kinesin oral degrader, as a development candidate with IND filing targeted for the first half of 2026.

• Portfolio focus narrowed to two main clinical opportunities: the BBI-355/BBI-825 combination and BBI-940.

Clinical learnings and rationale for new combinations

• BBI-355 showed potent CHK1 inhibition but was limited by a narrow therapeutic index and hematologic toxicity at effective doses.

• BBI-825, a selective RNR inhibitor, faced CYP induction and reduced exposure with daily BID dosing, limiting its efficacy as a single agent.

• Preclinical studies demonstrated strong synergy and tolerability for the BBI-355/BBI-825 combination, with weekly dosing mitigating prior PK and toxicity issues.

• The combination is expected to provide synergistic anti-tumor activity at tolerated doses, with clinical development planned for 2025.

Kinesin degrader program update

• BBI-940 targets a novel kinesin essential for ecDNA segregation in oncogene-amplified cancers, with no known competitors in the field.

• Demonstrated potent anti-tumor activity and favorable safety in preclinical models, supporting its advancement as a development candidate.

• IND-enabling work has begun, with an IND submission planned for the first half of 2026.