Constellation Pharmaceuticals has initiated the Phase 2 portion of its ProSTAR clinical trial in patients with metastatic castration-resistant prostate cancer (mCRPC).
The study is evaluating CPI-1205, Constellation’s potent and highly selective small-molecule EZH2 inhibitor, in combination with either enzalutamide or abiraterone / prednisone (abiraterone), in mCRPC patients who experienced disease progression while receiving the other ARS inhibitor.
Based on encouraging results from the Phase 1b portion of ProSTAR, the Company has initiated dosing in the randomised Phase 2 portion studying CPI-1205 in combination with enzalutamide versus enzalutamide alone.
Constellation has also decided to expand the Phase 2 portion of the study by adding an arm evaluating CPI-1205 in combination with abiraterone in the second-line setting.
“We are pleased that CPI-1205 achieved its Phase 1b endpoints in ProSTAR, demonstrating an encouraging safety profile and evidence of clinical activity in both arms,” said Adrian Senderowicz, Chief Medical Officer of Constellation Pharmaceuticals.
“As we advance into the Phase 2 portion of the study, we believe combination therapy with CPI-1205 may provide a meaningful second-line treatment option to patients with metastatic castration-resistant prostate cancer, an area of significant unmet medical need.”
Constellation has already begun dosing patients in the Phase 2 portion of the study, evaluating CPI-1205 in combination with enzalutamide versus enzalutamide alone.
The Company continues to expect enrolment of up to 35 patients in both the treatment and the control arms.
Additionally, Constellation is expanding the trial to include a separate Phase 2 arm evaluating CPI-1205 in combination with abiraterone in up to 30 mCRPC patients who progressed on prior enzalutamide therapy.
This arm, which will soon begin dosing patients, will not be randomised against a control arm due to the low response rate and lack of durability seen with abiraterone in the second-line setting.
Constellation continues to expect to determine proof of concept for CPI-1205 in mid-2019.