Astellas Pharma Inc. and Pfizer Inc. announced the US Food and Drug Administration (FDA) approved a supplemental New Drug Application (sNDA) to update the US product labeling for Xtandi (enzalutamide) capsules to include new clinical data versus bicalutamide from the TERRAIN study. The data demonstrate improvement in radiographic progression-free survival (rPFS) in patients with metastatic castration-resistant prostate cancer (CRPC) who were treated with enzalutamide compared to patients who were treated with bicalutamide.
The TERRAIN study evaluated men with metastatic CRPC and the results from this study were published in the Lancet Oncology. The updated label includes data that enzalutamide reduces the risk of radiographic progression or death by 40% compared with bicalutamide, showing a median rPFS of 19.5 months for the enzalutamide group versus a median of 13.4 months for the bicalutamide group (hazard ratio = 0.60 [0.43, 0.83]; 95% confidence interval) based on an analysis recommended by the FDA. The safety profile of enzalutamide was consistent with results of earlier enzalutamide trials.
"The addition of data from the TERRAIN trial continues to build the body of evidence that demonstrates the clinical impact XTANDI can have for patients living with metastatic CRPC," said Steven Benner, M.D., senior vice president, therapeutic area head for oncology development, Astellas. "Advances in scientific knowledge as seen through clinical trials like TERRAIN would not be possible without the participation of hundreds of patients, family members and clinical investigators, and we thank them for their valuable contributions."
According to the American Cancer Society, each year approximately 181,000 new cases of prostate cancer will be diagnosed and an estimated 26,000 men will die of the disease in 2016. Up to 40 percent of men diagnosed with prostate cancer who undergo therapy develop metastatic, or advanced, prostate cancer. In the US, the five-year relative survival rate for prostate cancer patients with metastatic disease is 28 percent, compared with 100 percent for prostate cancer patients with non-metastatic disease.
"We are pleased with the FDA's decision to update the Xtandi label with these data from the first and largest comparative trial that demonstrated safety and efficacy of enzalutamide compared to bicalutamide," said Mohammad Hirmand, M.D., interim chief medical officer at Medivation, Inc., which is now part of Pfizer. "We believe these data will help physicians better understand the differences between enzalutamide and bicalutamide for their patients living with metastatic CRPC."
The Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) issued a positive opinion on April 1, 2016 recommending approval of a type II variation to include data from the TERRAIN trials in the European label for Xtandi.
The phase II TERRAIN trial enrolled 375 chemotherapy-naïve patients with metastatic CRPC in North America and Europe. Radiographic progression-free survival was defined as the time from randomization to the first objective evidence of radiographic progression as assessed by Independent Central Review or death, whichever occurred first. The trial was designed to evaluate patients who were randomized 1:1 to receive enzalutamide at a dose of 160 mg taken orally once daily versus bicalutamide at a dose of 50 mg taken once daily.
Grade 3-4 adverse reactions were reported in 38.8% of enzalutamide-treated patients and 37.6% of bicalutamide-treated patients. Individual Grade 3 or higher adverse events largely occurred at a similar rate (<1% difference) between the enzalutamide vs. bicalutamide treatment groups, with the exception of hypertension (7.1% vs. 4.4%), diarrhea (0% vs. 1.1%) and back pain (2.7% vs. 1.6%). Two seizures were reported in the enzalutamide group and one in the bicalutamide group. The most common Grade 1-4 adverse reactions (incidence =10%) occurring during treatment and more common in the enzalutamide-treated versus bicalutamide-treated patients included asthenic conditions, back pain, musculoskeletal pain, hot flush, hypertension, diarrhea, upper respiratory tract infection, and weight loss.
Xtandi (enzalutamide) capsules is an androgen receptor inhibitor that blocks multiple steps in the androgen receptor signaling pathway within the tumor cell. In preclinical studies, enzalutamide has been shown to competitively inhibit androgen binding to androgen receptors, and inhibit androgen receptor nuclear translocation and interaction with DNA. The clinical significance of this mechanism of action (MOA) is unknown.
Xtandi is approved by the US Food and Drug Administration for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC).