Phase 3 trial in prostate cancer subset discontinued due to lack of survival benefit

Pharmaceutical company Merck has announced that it will discontinue a phase 3 study in patients with hormone-sensitive metastatic prostate cancer due to lack of positive effect with Keytruda (pembrolizumab) with Xtandi (enzalutamide) and androgen deprivation therapy.

The suggestion to stop the KEYNOTE-991 trial came from the independent data monitoring committee (an impartial group that oversees a clinical trial and its results to see if they are acceptable), according to a press release from Merck, maker of Keytruda.

In particular, the committee determined that Keytruda with Xtandi and androgen deprivation therapy did not improve progression-free survival (the time after treatment when a patient lives with the cancer without getting worse) or overall survival (the time from treatment when a patient cancer patient is still alive) compared to placebo, Xtandi, and androgen deprivation therapy.

“There is a significant unmet need for patients with advanced prostate cancer, and the result of this study is an important reminder that this disease remains very difficult to treat,” said Dr. Scot Ebbinghaus, vice president of clinical research at Merck Research Laboratories, at the launch. “We are grateful to patients and researchers for their participation in this trial and will continue to advance our clinical development program to evaluate Keytruda-based combinations and new candidates for patients with prostate cancer.”

Hormone-sensitive prostate cancer is a disease that requires androgens (or male hormones, including testosterone) to grow. Treatment with hormone therapy – androgen deprivation therapy – can block or stop androgens, potentially slowing the cancer’s growth.

Although patients may initially respond to androgen deprivation therapy alone, most patients progress to castration-resistant prostate cancer (when the cancer grows even with testosterone reductions) and no longer responds to hormone therapy within three years.

The researchers who conducted the KEYNOTE-991 study enrolled 1251 patients with hormone-sensitive metastatic prostate cancer. Patients received Xtandi and androgen deprivation therapy with Keytruda or placebo.

In addition to progression-free survival and overall survival, other factors to be evaluated included duration of response (the time from a patient receiving the designated treatment until disease progression or death in those who had a complete or partial response to therapy). , objective response rate (the percentage of patients with a partial or complete response to treatment in a given time period), and safety, according to the release.

In the study, Keytruda demonstrated a safety profile consistent with that of previous studies, according to the release. Although no new side effects were seen with Keytruda, the combination of Keytruda, Xtandi, and androgen deprivation therapy was associated with a higher incidence of serious, fatal, or life-threatening side effects compared with the placebo group.

Results from the KEYNOTE-991 study up to the time the study was stopped will be presented at an upcoming medical meeting, according to the release.

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Phase 3 trial in prostate cancer subset discontinued due to lack of survival benefit

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