Phase III ARCHES trial of Xtandi meets primary endpoint in metastatic prostate cancer.- Pfizer Inc. and Astellas

Pfizer Inc. and Astellas Pharma announced results from the Phase III ARCHES trial of Xtandi (enzalutamide) in men with metastatic hormone-sensitive prostate cancer (mHSPC). The results show that enzalutamide plus androgen deprivation therapy (ADT) met the primary endpoint by significantly reducing the risk of radiographic progression or death by 61% versus ADT alone. Median time to a radiographic progression-free survival (rPFS) event was not reached in the Xtandi plus ADT arm, while median time to an rPFS event in the ADT alone arm was 19.4 months. Significant improvements in rPFS were also observed in all prespecified subgroups including disease volume, pattern of disease localization at baseline, geographic region, and prior docetaxel use (HRs=0.24-0.53).

Secondary endpoints reported in the abstract showed that Xtandi plus ADT reduced the risk of PSA progression (HR=0.19 [95% CI: 0.13-0.26]; p<0.0001) and reduced the risk of starting a new antineoplastic therapy hr="0.28" 95 ci: 0.20-0.40 p><0.0001) compared to adt alone. undetectable psa and objective response rates were also higher in men treated with xtandi plus adt versus adt alone 68.1 versus 17.6 p><0.0001 and 83.1 versus 63.7 p><0.0001, respectively. treatment with xtandi plus adt did not significantly reduce the risk of deterioration in urinary symptoms compared to adt alone. at the time of the analysis overall survival os data were not mature. adverse events aes in the arches clinical trial were generally consistent with those reported in enzalutamide clinical trials in patients with castration-resistant prostate cancer crpc. these data will be presented in an oral session at the 2019 genitourinary cancers symposium.>

Comment: Based on the ARCHES results, the companies intend to discuss these data with global health authorities to potentially support a new indication for Xtandi in men with mHSPC. Xtandi is currently approved in the U.S. and Japan for the treatment of CRPC and in the EU for the treatment of metastatic and high-risk non-metastatic CRPC.