Pfizer and Astellas announced amendments to the protocols for the late-stage ARCHES and EMBARK trials, which are designed to evaluate the safety and efficacy of Xtandi (enzalutamide) in men with hormone-sensitive prostate cancer (HSPC). "These amendments accelerate timelines for the anticipated primary completion dates of both trials," the companies said.
The ARCHES  study is assessing Xtandi plus androgen deprivation therapy (ADT) versus ADT alone in patients with metastatic HSPC, with the primary endpoint being radiographic progression-free survival. Protocol changes include revision of planned analyses of the primary and secondary endpoints. The drugmakers noted that based on the amendments, the anticipated primary completion date for the trial has changed from April 2020 to late 2018.
The EMBARK study, whose main goal is metastasis-free survival, is evaluating Xtandi plus leuprolide versus monotherapy with either Xtandi or leuprolide in men with high-risk non-metastatic HSPC. Pfizer and Astellas indicated that the purpose of the protocol amendment is to revise the planned analyses of the primary and several secondary endpoints, resulting in a smaller sample size. Following the changes, the estimated primary completion date of the study was shifted to mid-2020 from March 2021.
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The companies had previously amended  the Phase III PROSPER study of Xtandi to accelerate top-line data by two years. Based on the results , the FDA expanded approval  for the drug last month to include non-metastatic castration-resistant prostate cancer (CRPC).
Xtandi was initially approved in the US in 2012 for patients with previously treated metastatic CRPC, and was later expanded to include metastatic CRPC in chemotherapy-naïve men . Pfizer recorded sales of $171 million for the therapy in the quarter ended June 30.
For related analysis, see ViewPoints: Pfizer, Astellas go for the gusto again with Xtandi . See also, ViewPoints: The race is on for Xtandi in non-metastatic setting .