Safety and efficacy of neratinib in combination with weekly paclitaxel and trastuzumab in women with metastatic HER2-positive breast cancer: an NSABP Foundation Research Program phase I study

Purpose Neratinib is an oral, small-molecule inhibitor that irreversibly binds to pan-HER (ErbB) receptor tyrosine kinases. Studies suggest that dual anti-HER therapies utilized in breast cancer patients are more efficacious than single agents in both the metastatic and neoadjuvant settings. In this phase I study, neratinib was combined with trastuzumab and paclitaxel in metastatic HER2-positive patients. Methods Twenty-one patients entered this dose-escalation study to determine the maximum-tolerated dose, safety, and efficacy of neratinib (120 up to 240 mg/day) with trastuzumab (4 mg/kg IV loading dose, then 2 mg/kg IV weekly), and paclitaxel (80 mg/m 2 IV days 1, 8, and 15 of a 28-day cycle) in women with HER2-positive metastatic breast cancer previously treated with anti-HER agent(s) and a taxane. Results The recommended phase II dose of neratinib with trastuzumab and paclitaxel was 200 mg/day. Common grade 3/4 adverse events were diarrhea (38 %), dehydration (14 %), electrolyte imbalance (19 %), and fatigue (19 %). With mandated primary diarrheal prophylaxis, ≥grade 3 diarrhea was not observed. Objective responses, complete (CR) and partial (PR), occurred in eight patients (38 %), with a clinical benefit of CR + PR+ stable disease (SD) ≥24 weeks in 11 patients (52 %). Median time-to-disease progression was 3.7 months. Conclusions Dual anti-HER blockade with neratinib and trastuzumab resulted in significant clinical benefit despite prior exposure to trastuzumab, lapatinib, T-DM1, a taxane, and multiple lines of chemotherapy. In selected populations, inhibiting multiple ErbB-family receptors may be more advantageous than single-agent inhibition. Based on favorable tolerance and efficacy, this three-drug combination will be further assessed in a randomized phase II neoadjuvant trial (NSABP FB-7:NCT01008150).