Pfizer, Astellas announce data from Phase 3 EMBARK trial

Astellas Pharma and Pfizer announced that XTANDI, or enzalutamide, plus leuprolide significantly reduced the risk of metastasis or death by 58% versus placebo plus leuprolide, as assessed by the primary endpoint of metastasis-free survival, in men with non-metastatic hormone-sensitive prostate cancer with high-risk biochemical recurrence. These data from the Phase 3 EMBARK trial, which evaluated patients across three study arms, were presented as a plenary session during the 2023 American Urological Association Annual Meeting. The overall safety profile was consistent with the known safety profile of each of the medicines. The most common adverse events in those treated with XTANDI plus leuprolide were fatigue, hot flush, and arthralgia and in those treated with XTANDI monotherapy were fatigue, gynecomastia, and arthralgia. Consistent with the study’s primary endpoint, statistically significant and clinically meaningful improvements were also observed in the trial’s key secondary endpoints in both the XTANDI combination and monotherapy arms. Specifically, the XTANDI monotherapy arm demonstrated that treatment with XTANDI reduced the risk of metastasis or death by 37% versus leuprolide plus placebo, meeting its MFS endpoint. Treatment with XTANDI plus leuprolide and XTANDI monotherapy reduced the risk of PSA progression by 93% and 67%, respectively, versus placebo plus leuprolide. The progression risk in starting a new antineoplastic therapy was reduced by 64% in those treated with XTANDI plus leuprolide and 46% in those treated with XTANDI monotherapy versus placebo plus leuprolide. A positive trend in the key secondary endpoint of overall survival was also observed in the XTANDI combination arm at the time of the analysis, but these data were not yet mature. Patients in the trial will be followed for a subsequent final OS analysis. Detailed results from the trial will be submitted for peer-reviewed publication. Additionally, the EMBARK data will be discussed with regulatory authorities, including the U.S. Food and Drug Administration, to support a potential regulatory submission for XTANDI in this indication in 2023.