OP-3136 + fulvestrant

OP-3136 + fulvestrant is a combination regimen under clinical investigation for the treatment of cancers, primarily **estrogen receptor positive, HER2 negative (ER+ HER2-) breast cancer**. OP-3136 is a selective, orally available small molecule inhibitor of **lysine acetyltransferases 6A and 6B (KAT6A/B)**, enzymes involved in epigenetic regulation and oncogenesis. Fulvestrant is a well-established **estrogen receptor antagonist** (selective estrogen receptor degrader). The combination is designed to synergistically inhibit tumor growth by targeting both epigenetic modification (KAT6A/B inhibition) and hormonal signaling (estrogen receptor blockade). Preclinical data indicate that OP-3136 exhibits robust anti-proliferative activity in solid tumor models and shows enhanced anti-tumor activity when combined with fulvestrant. This combination is currently being assessed in a phase 1 clinical trial for patients with advanced or metastatic ER+ HER2- breast cancer who have progressed after prior endocrine and CDK4/6 inhibitor therapies[4][7][8].