The FDA expanded the approval of enzalutamide to include the treatment of nonmetastatic castration-resistant prostate cancer.
Enzalutamide (Xtandi; Astellas, Pfizer) — an androgen receptor inhibitor — received FDA approval in 2012 for the treatment of men with metastatic castration-resistant prostate cancer who previously received docetaxel. In 2014, the FDA approved enzalutamide for chemotherapy-naive men with metastatic castration-resistant prostate cancer.
With the newest approval, enzalutamide becomes the only oral treatment to receive FDA approval for both nonmetastatic and metastatic prostate cancer.
“With [this] approval, there is now a new option for men with nonmetastatic castration-resistant prostate cancer, who are in between the failure of androgen deprivation therapy resulting in castration-resistant prostate cancer and the onset of metastatic disease,” Jonathan Simons, MD, president and CEO of Prostate Cancer Foundation, said in a press release. “As a foundation that drives research aimed at improving patient outcomes, it is exciting to see approvals like this, which are vital to help address unmet patient needs.”
The FDA based the expanded approval on results of the phase 3 PROSPER trial, which included 1,401 men with nonmetastatic castration-resistant prostate cancer.
Researchers randomly assigned men 2:1 to androgen deprivation therapy plus either enzalutamide or placebo.
As HemOnc Today previously reported, the results — presented at this year’s Genitourinary Cancers Symposium and published simultaneously in The New England Journal of Medicine — showed men assigned enzalutamide achieved significantly longer median metastasis-free survival (36.6 months vs. 14.7 months; HR = 0.29; 95% CI, 0.24-0.35).
Researchers also reported significantly longer median time to first use of new antineoplastic therapy in the enzalutamide group (39.6 months vs. 17.7 months; HR = 0.21; 95% CI, 0.17-0.26).
“Reducing the risk of disease progression is an important treatment goal in castration-resistant prostate cancer, [because] the disease becomes harder to treat as it advances,” Andy Schmeltz, global president of oncology for Pfizer, said in the release. “With Xtandi, men with castration-resistant prostate cancer now have a clinically proven treatment option that reduces the risk of metastasis.”
The most common adverse reactions reported among enzalutamide-treated patients included asthenic conditions (40% for enzalutamide-ADT vs. 20% for placebo-ADT), hot flushes (13% vs 7.7%), hypertension (12% vs 5.2%), dizziness (12% vs 5.2%), nausea (11% vs 8.6%) and falls (11% vs 4.1%).
Grade 3 or higher adverse reactions occurred among 31% of men assigned enzalutamide and 23% of men assigned placebo. A higher percentage of enzalutamide-treated patients died due to adverse events (3.4% vs. 0.6%) or discontinued treatment due to adverse events (9.4% vs. 6%).
“This approval is important progress for men with castration-resistant prostate cancer, who now have Xtandi as a treatment option regardless of whether ... they have detectable metastatic disease,” Steven Benner, MD, senior vice president and global therapeutic area head for oncology development at Astellas, said in the release.