ESSA Pharma Inc. said its product candidate EPI-506 showed an acceptable safety profile in doses up to 2,400 milligrams in a phase 1 trial in men with metastatic castration-resistant prostate cancer, or mCRPC.

The company observed signs of clinical activity at the higher doses in the analysis, in line with its preclinical modeling.

The data is from the phase 1 portion of an ongoing phase 1/2 trial which is evaluating the drug candidate's safety, pharmacokinetics, maximum tolerated dose and anti-tumor activity in patients with end-stage mCRPC who have progressed after prior enzalutamide and/or abiraterone treatment and may have received one prior line of chemotherapy.

Of the 21 patients available for analysis, 17 discontinued treatment, primarily due to progressive disease, while four remained a part of the study. The patients self-administered oral doses of EPI-506 ranging from 80 mg to 2,400 mg under the trial.

EPI-506, or ralaniten acetate, is a novel androgen receptor N-terminal domain inhibitor.