EPI-7386 in combination with enzalutamide was safe and well-tolerated at the doses tested with clinically relevant drug exposures and deep and durable prostate specific antigen ("PSA") reductions observed in five of six patients
ESSA Pharma Inc. ("ESSA", or the "Company") (NASDAQ: EPIX), a clinical-stage pharmaceutical company focused on developing novel therapies for the treatment of prostate cancer, today announced the presentation of updated clinical data from the first two cohorts of the Phase 1/2 study of ESSA's lead candidate EPI-7386 in combination with enzalutamide in patients with metastatic castration-resistant prostate cancer ("mCRPC"). Data will be presented in a poster format at the 2022 Prostate Cancer Foundation ("PCF") Scientific Retreat, taking place October 27-29, 2022 in Carlsbad, CA.
In the multicenter, open-label Phase 1/2 dose escalation study, seven mCRPC patients naïve to second generation antiandrogens were enrolled in the first two cohorts, with escalating doses of EPI-7386 and a fixed 120mg once a day (QD) dose of enzalutamide. The study permitted one prior line of chemotherapy. Pharmacokinetic results from these first two cohorts demonstrated that enzalutamide exposure was minimally impacted by EPI-7386 while exposures of EPI-7386 were reduced by coadministration with enzalutamide, but remained in the clinically relevant range as suggested by preclinical xenograft studies. The safety of the combination was favorable with a safety profile consistent with second-generation antiandrogens and no dose limiting toxicities observed. One of the patients in the first cohort discontinued after one cycle of dosing due to a strong CYP3A inducer concomitant medication which lowered exposures to both EPI-7386 and enzalutamide and was therefore not evaluable for efficacy. Anti-tumor activity in the remaining six patients enrolled demonstrated that four of six of these patients achieved a PSA90 by 12 weeks of dosing and five of six patients to date have achieved a PSA90.