Halted Study
Biological: Pembrolizumab
Drug: Enzalutamide
Procedure:  Androgen Deprivation Therapy (ADT)

Merck
"....The safety profile of KEYTRUDA in this trial was consistent with that observed in previously reported studies. No new safety signals were identified; however, the combination was associated with a higher incidence of Grade 3-5 adverse events and serious adverse events compared to the control arm...."

ZEN-3694 Study
Drug: BET Bromodomain Inhibitor ZEN-3694
Drug: Enzalutamide
Biological: Pembrolizumab

Given that the ZEN study also includes both Enzalutamide and Pembrolizumab, why are similar side effects not a possible concern in the ZEN study?