U.S. Food and Drug Administration Approval: Neratinib for the Extended Adjuvant Treatment of Early Stage HER2-Positive Breast Cancer

On July 17, 2017, the Food and Drug Administration (FDA) approved neratinib (NERLYNX, Puma Biotechnology, Inc) for the extended adjuvant treatment of adult patients with early-stage HER2-overexpressed/amplified breast cancer, to follow adjuvant trastuzumab-based therapy. Approval was based on data from ExteNET, a randomized, double-blind, placebo-controlled multicenter trial. Women with early-stage HER2-positive breast cancer and within two years of completing adjuvant trastuzumab were randomized to neratinib (n=1420) or placebo (n=1420) for one year. The primary endpoint was invasive disease-free survival (iDFS) defined as the time between randomization date to first occurrence of invasive recurrence (local/regional, ipsilateral or contralateral breast cancer), distance recurrence, or death from any cause, with two years and 28 days of follow up. The trial showed a statistically significant treatment effect favoring neratinib with a stratified hazard ratio of 0.66 (95% CI: 0.49, 0.90, p=0.008). Estimated iDFS rate at 2-years was 94.2% (95% CI: 92.6%, 95.4%) in patients treated with neratinib vs. 91.9% (95% CI: 90.2%, 93.2%) in those receiving placebo. Diarrhea was the most common adverse event (AE) with a 40% incidence of Grade 3 or 4 diarrhea and represents the most common AE leading to treatment discontinuation. Other frequent AEs (>10% incidence) were nausea, abdominal pain, fatigue, vomiting, rash, stomatitis, decreased appetite, and muscle spasms. Other than diarrhea, neratinib is associated with a low incidence of severe AEs; toxicities are generally reversible and manageable with dose interruptions, dose reductions, and/or standard medical care. This article summarizes FDA decision-making and data supporting the neratinib approval.

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