OB-001 functions by inhibiting P-gp and BCRP, two primary efflux pumps located on the blood-brain barrier and the surface of tumor cells. By blocking these transporters, the once-daily tablet aims to restore the efficacy of standard oncology treatments that are otherwise limited by poor brain penetration or cellular resistance. Preclinical data presented at AACR 2026 underscored its potential to enhance therapeutic concentration without altering systemic plasma exposure.

Beyond brain metastases in NSCLC and breast cancer, the drug addresses a critical failure point in antibody-drug conjugates. Over-expression of these same efflux pumps often prevents necessary payload concentrations from accumulating within tumors. OncoBayes reported that OB-001 successfully reduced efflux for payloads including SN-38, DM4, and DXd. CEO Jim Millen characterized the asset as a first-in-class adjunct, with upcoming trials set to generate proof-of-concept data for both osimertinib combinations and T-DXd re-sensitization.