Afatinib in patients with advanced non-small cell lung cancer harboring HER2 mutations, previously treated with chemotherapy: A phase II trial

•Phase II analysis of the efficacy and safety of afatinib therapy for HER2m + NSCLC.•No patient achieved an overall response, and no clinical benefit was demonstrated.•The trial was prematurely discontinued due to poor efficacy and slow recruitment. Despite 1–4 % of NSCLC tumors harboring mutations in the HER2 gene, there are no approved HER2-pathway-targeted treatments available. We report an open-label, single-arm, multicenter phase II study investigating the efficacy and safety of afatinib in Asian patients with HER2-mutation positive (HER2m+) NSCLC. Eligible patients for Part A had confirmed stage IIIb/IV HER2m + NSCLC, had failed one or two prior lines of chemotherapy, and were EGFR/HER2-inhibitor naïve. Patients received oral afatinib 40 mg/day in continuous 28-day cycles, until disease progression or intolerable adverse events (AEs). Patients qualified for Part B if they had > 12 weeks’ clinical benefit and Eastern Cooperative Oncology Group performance status ≤ 2. In Part B, patients were to receive afatinib at the last received dose, plus paclitaxel 80 mg/m2 weekly, until disease progression or intolerable AEs. The primary endpoint in Part A was objective response (OR); secondary endpoints included disease control (DC), progression-free survival (PFS), and overall survival (OS). Further exploratory endpoints were OR, DC, and PFS in Part B. Eighteen patients received afatinib in Part A. No patient achieved an OR; 11 patients (61.1 %) achieved stable disease, and six patients (33.3 %) had progressive disease. DC rate was therefore 61.1 % (95 % confidence interval [CI]: 35.7, 82.7). A decrease in tumor size from baseline of > 0 to < 30 % was observed in eight patients. At the time of analysis, 16 patients (88.9 %) had progressed or died. Median PFS was 2.76 months (95 % CI: 1.87, 4.60) and median OS was 10.02 months (95 % CI: 8.47, 10.08). All patients experienced ≥ 1 AE, most commonly diarrhea (66.7 %) and rash (33.3 %). No patients met the inclusion criteria for Part B, and recruitment was slow; therefore, the study was terminated. This study found no clinical benefit of afatinib for EGFR TKI-naïve patients with HER2m + NSCLC.