Astellas and Pfizer's Xtandi Meets Primary Endpoint in Ph III Trial of Metastatic Prostate Cancer

Astellas Pharma Inc. (TSE: 4503, President and CEO: Kenji Yasukawa, Ph.D., “Astellas”) and Pfizer Inc. (NYSE: PFE) today announced that the Phase 3 ARCHES trial evaluating Xtandi (enzalutamide) plus androgen deprivation therapy (ADT) in men with metastatic hormone-sensitive prostate cancer (mHSPC) met its primary endpoint, significantly improving radiographic progression-free survival (rPFS) versus ADT alone. The preliminary safety analysis of the ARCHES trial appears consistent with the safety profile of XTANDI in previous clinical trials in castration-resistant prostate cancer (CRPC). Detailed results will be submitted for presentation at an upcoming medical congress.

“The results from ARCHES demonstrate a statistically significant improvement in a key marker of disease progression – radiographic progression-free survival,” said Steven Benner, M.D., senior vice president and global therapeutic area head, Oncology Development, Astellas. “Based on the top-line results of ARCHES, we look forward to discussing the data with relevant health authorities to potentially support expanding the indication for Xtandi.”

The Phase 3, randomized, double-blind, placebo-controlled, multi-national trial enrolled 1,150 patients with metastatic hormone-sensitive prostate cancer (mHSPC) at sites in the United States, Canada, Europe, South America and the Asia-Pacific region. Patients in the ARCHES trial were randomized to receive Xtandi 160 mg daily or placebo and continued on a luteinizing hormone-releasing hormone (LHRH) agonist or antagonist or had a history of bilateral orchiectomy. The ARCHES trial included patients with both low- and high- volume disease and both newly diagnosed patients with mHSPC and patients who had prior definitive therapy and subsequently developed metastatic disease. The trial also included some patients who had received recent treatment with docetaxel for mHSPC, but whose disease had not progressed. The primary endpoint of the trial was radiographic progression-free survival (rPFS), defined as the time from randomization to the first objective evidence of radiographic disease progression as assessed by central review, or death, whichever occurs first.

In July of 2018, the FDA approved Xtandi for the treatment of men with non-metastatic castration-resistant prostate cancer (CRPC). This made it the first oral medication approved for both non-metastatic and metastatic CRPC. Xtandi is an androgen receptor inhibitor that acts on multiple steps of the androgen receptor signaling pathway within the tumor cell.

In men with prostate cancer, the disease is considered metastatic once the cancer has spread outside of the prostate gland to other parts of the body, such as the bones, lymph nodes, bladder and rectum.2 Men are considered hormone (or castration) sensitive if their disease still responds to medical or surgical treatment to lower testosterone levels.3Approximately 38,000 men in the U.S. develop metastatic HSPC every year.