Pfizer: Astellas’ and Pfizer’s XTANDI® (enzalutamide) Reduced Risk of Death by 34% in Men with Metastatic Hormone-Sensitive Prostate Cancer in Phase 3 ARCHES Study

Astellas Pharma Inc. (TSE: 4503, President and CEO: Kenji Yasukawa, Ph.D., “Astellas”) and Pfizer Inc. (NYSE: PFE) announced today ahead of the European Society for Medical Oncology (ESMO) Congress 2021 that XTANDI® (enzalutamide) improved overall survival (OS) in the ARCHES study in men with metastatic hormone-sensitive prostate cancer (mHSPC, also known as metastatic castration-sensitive prostate cancer). The Phase 3, randomized, double-blind, placebo-controlled trial compared XTANDI plus androgen deprivation therapy (ADT) versus placebo plus ADT in men with mHSPC and OS was a key secondary endpoint.

In the study, XTANDI plus ADT reduced the risk of death by 34% (n=1,150; hazard ratio [HR]=0.66; [95% confidence interval [CI]: 0.53-0.81]; p<0.0001) compared to placebo plus ADT. Median OS, which represents the time from randomization to death due to any cause, was not reached in either treatment group. The safety profile in both study arms was consistent with findings from the primary analysis.

Results from the final analysis of the ARCHES trial will be presented virtually at ESMO by Andrew Armstrong, M.D., Professor of Medicine, Surgery, Pharmacology and Cancer Biology, and Director of Research in the Duke Cancer Institute’s Center for Prostate and Urologic Cancers in Durham, North Carolina, U.S. (Abstract LBA25; September 18, 14:20 CEST).

“Overall survival benefit has been observed in patients treated with enzalutamide in three stages of advanced prostate cancer – metastatic castration-resistant prostate cancer, non-metastatic castration-resistant prostate cancer, and now in metastatic hormone-sensitive prostate cancer,” said Dr. Armstrong. “The results from ARCHES provide valuable data on the clinical profile of enzalutamide in this earlier disease setting.”

The primary results from the ARCHES trial were published in the Journal of Clinical Oncology in 2019. The study met its primary endpoint of radiographic progression-free survival (rPFS) as assessed by independent central review, finding that treatment with XTANDI plus ADT demonstrated a 61% reduction in the risk of radiographic disease progression or death compared with ADT alone in men with mHSPC (HR=0.39; [95% CI: 0.30-0.50]; p<0.001).1 The median follow-up time was 14.4 months. Median rPFS was not reached (NR) with XTANDI plus ADT (95% CI: NR to NR) versus 19.0 months (95% CI: 16.6-22.2 months) with placebo plus ADT. At the time of the primary analysis, OS data were not mature.

In the ARCHES primary analysis, Grade 3 or greater adverse events (AEs; defined as severe/disabling or life-threatening) were similar for patients receiving both XTANDI plus ADT and those who received placebo plus ADT (24.3% vs. 25.6%). Common AEs (occurring in at least 5% of patients) that were reported more often in patients treated with XTANDI plus ADT versus those treated with ADT alone included hot flush, fatigue, arthralgia, hypertension, nausea, musculoskeletal pain, diarrhea, asthenia and dizziness.