Pfizer goes early with mevrometostat

With its EZH2 inhibitor mevrometostat Pfizer isn't stopping at castration-resistant prostate cancer. A just published clinicaltrials.gov listing has revealed details of the phase 3 Mevpro-3 trial in the hormone-sensitive setting, where mevrometostat is to be combined with Xtandi and compared against Xtandi alone on the primary metric of radiographic progression-free survival. Pfizer had in February signalled plans to test mevrometostat in Mevpro-3, so the new trial's start, planned for August, will deliver on this promise. Pfizer's Xtandi was approved for metastatic hormone-sensitive prostate cancer back in 2019, on the basis of an rPFS benefit in the pivotal Arches trial amounting to a 0.39 hazard ratio versus placebo. An update from Arches, published in the Journal of Clinical Oncology in 2022, revealed a median for rPFS of 49.8 months, so this appears to be the bar for Mevpro-3. Interestingly, there appear to be no human data for mevrometostat specifically in hormone-sensitive prostate cancer, so in starting Mevpro-3 Pfizer is being even bolder than it was when it fast-tracked the project into its first pivotal study, Mevpro-1, in post-Zytiga castration-resistant disease; that move was backed only by phase 1 data.

Mevrometostat's phase 3 trials

Note: ARPI=androgen receptor pathway inhibitor. Source: OncologyPipeline.