ASCO 2026 preview – Olema takes its KAT6 into prostate

KAT6 inhibition has been largely focused on breast cancer, but now Olema is taking its candidate, OP-3136, into a dedicated prostate cancer trial. The phase 1/2 study, to start in the second half, will test OP-3136 alongside Bayer’s androgen receptor inhibitor Nubeqa in around 36 patients with metastatic castration-resistant prostate cancer. Nubeqa is only FDA approved in non-metastatic CRPC, as well as hormone-sensitive disease. The trigger appears to be data from a phase 1 solid tumour trial of OP-3136, to be presented in an ASCO poster. The abstract details two unconfirmed responses among 14 monotherapy patients – one with CRPC and one with advanced breast cancer. Olema last week claimed three responses (one unconfirmed) among 19 evaluable patients, but didn’t break this down by tumour type. More details will be awaited, but this already looks more promising than Pfizer’s contender prifetrastat, which produced no responses among eight CRPC patients in its early-stage trial, as reported at ASCO 2023. Pfizer has started a phase 3 trial of prifetrastat, Katsis-1, in second-line ER-positive, HER2-negative breast cancer, but has announced no plans in prostate. Ideaya and Henlius have also included CRPC patients in their early trials of IDE574 and HLX97 respectively.