Constellation Pharmaceuticals Inc (NASDAQ: CNST ) said it has begun dosing in a randomized Phase 1b/2 study dubbed ProSTAR, of CPI-1205/enzalutamide combo versus enzalutamide monotherapy for treating metastatic castration-resistant prostate cancer. The company said preliminary Phase 1b results show that CPI-1205 was well tolerated, with a robust pharmacokinetic/pharmacodynamic profile and clinical activity in both arms.