Changes Made to Phase 3 Xtandi Trial in Men with Non–Metastatic Castration–Resistant Prostate Cancer

Changes Made to Phase 3 Xtandi Trial in Men with Non–Metastatic Castration–Resistant Prostate Cancer

Astellas Pharma and Pfizer amended the protocol of the international Phase 3 PROSPER trial evaluating Xtandi (enzalutamide) in men with non–metastatic castration–resistant prostate cancer (CRPC).

PROSPER is a randomized, double–blind, placebo–controlled trial (NCT02003924) that is evaluating the safety and effectiveness of Xtandi in these patients. Study participants are randomized to 160 mg of Xtandi orally once daily or a placebo.

The primary goal of the study, which remains the same, is to assess the effectiveness of the compound by measuring the metastasis–free survival (MFS) of patients after a treatment period of more than 16 weeks.

Secondary objectives of the study include the time to prostate–specific antigen (PSA) progression, patients’ overall survival (OS), time to pain progression, time to chemotherapy–free survival, patients’ quality of life, and other efficacy and safety measures.

The amendment revises the plan for the analyses of the primary and several secondary endpoints, which allows for a reduction of 120 participants in the target sample size, from 1,560 men to 1,440.

Another change to the PROSPER trial is in the timeline of top–line results. Previously, the expected primary completion date was June 2019. Astellas and Pfizer now expect to release top–line results later this year, with a primary completion date — when final data collection is due — of June 2017.

The trial was initiated in December 2013 and involves more than 200 study locations in the U.S., Canada, Europe, South America, and the Asia Pacific region.

Xtandi is a hormone therapy approved by the U.S. Food and Drug Administration (FDA) in 2012 for the treatment of patients with metastatic castration–resistant prostate cancer who have previously received treatment with docetaxel.

The hormones in the body are the trigger for the growth of cancer, particularly androgens. Xtandi is an androgen receptor antagonist, which means that it works by blocking the male hormones from signaling the cancer cell to grow. The treatment is expected to stop the growth of the tumor, and in some cases it might even shrink it.

“Xtandi is already a standard of care for men worldwide fighting metastatic castration-resistant prostate cancer, but we are continually looking to evaluate this medicine for men facing earlier stage disease,” Steven Benner, MD, senior vice president and global therapeutic area head of oncology at Astellas, said in a press release. “By amending the protocol for PROSPER, we hope to be able to accelerate the evaluation of the data in this area of medical need.”

Mace Rothenberg, MD, chief development officer of oncology at Pfizer, said PROSPER is one of the large, randomized trials in the company’s development program evaluating Xtandi in different prostate cancer stages, including men with earlier stages.

“We look forward to building upon the extensive body of clinical evidence that has been generated over the past five years and established Xtandi as a standard of care for men with metastatic CRPC,” he said.

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