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 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 2 years of completing adjuvant trastuzumab were randomized to neratinib (<i>n</i> = 1,420) or placebo (<i>n</i> = 1,420) for 1 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), distant recurrence, or death from any cause, with 2 years and 28 days of follow-up. The trial showed a statistically significant treatment effect favoring neratinib with a stratified HR of 0.66 [95% confidence interval (CI), 0.49-0.90, <i>P</i> = 0.008]. The estimated iDFS rate at 2 years was 94.2% (95% CI, 92.6%-95.4%) in patients treated with neratinib versus 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. <i>Clin Cancer Res; 24(15); 3486-91. ©2018 AACR</i><i>See related commentary by Unni et al., p. 3483</i>.