Supplementary Material for: Neratinib Alone or in Combination with Immune Checkpoint Inhibitors with or without mTOR Inhibitors in Patients with Fibrolamellar Carcinoma

Introduction: Fibrolamellar carcinoma (FLC) displays upregulation of several oncogenes, including HER2, and multiple immune-suppressive mechanisms. We investigated the efficacy and safety of the pan-HER tyrosine kinase inhibitor neratinib as monotherapy (SUMMIT phase 2 basket study) or with immune checkpoint and/or mTOR inhibitors (compassionate-use program) in patients with FLC. Methods: Patients received neratinib 240 mg/day orally in SUMMIT, or as doublet or triplet combinations with pembrolizumab 2 mg/kg intravenously every 3 weeks, nivolumab 240 mg intravenously every 2 weeks, everolimus 7.5 mg/day orally, or sunitinib 37.5 mg/day orally under compassionate use. The primary endpoint in SUMMIT was objective response rate; safety was a secondary endpoint. Results: Fifteen patients with FLC received neratinib monotherapy in SUMMIT. The objective response rate was 5% (95% CI 0–21.8) and the disease control rate was 13.3% (95% CI 1.7–40.5). Upon progression, five had added immune checkpoint inhibitors with or without everolimus or sunitinib. Two additional patients received neratinib-based combinations outside of SUMMIT, for a total of 17 neratinib-treated patients. One patient who received neratinib plus pembrolizumab had a confirmed partial response, one treated with neratinib plus everolimus had stable disease lasting 6 months, and one who received neratinib plus pembrolizumab plus sunitinib had stable disease lasting 16 months. Grade 3/4 adverse events with neratinib monotherapy occurred in 10 (66.7%)/2 (13.3%) patients, respectively. Grade 3 adverse events with neratinib-based combinations were hyperglycemia (n = 1; neratinib plus pembrolizumab), hepatic failure, and anaphylaxis (n = 1 each, neratinib plus pembrolizumab plus everolimus). There were no grade 4 adverse events with combination therapy. Conclusion: In patients with FLC, single-agent neratinib had limited efficacy, but clinical benefit was observed with neratinib in combination with immunotherapy and/or mTOR-targeted agents.