Although most activating mutations of epidermal growth factor receptor (EGFR)-mutant non–small cell lung cancers (NSCLCs) are sensitive to available EGFR tyrosine kinase inhibitors (TKIs), a subset with alterations in exon 20 of EGFR and HER2 are intrinsically resistant and lack an effective therapy. We used in silico, in vitro, and in vivo testing to model structural alterations induced by exon 20 mutations and to identify effective inhibitors. 3D modeling indicated alterations restricted the size of the drug-binding pocket, limiting the binding of large, rigid inhibitors. We found that poziotinib, owing to its small size and flexibility, can circumvent these steric changes and is a potent inhibitor of the most common EGFR and HER2 exon 20 mutants. Poziotinib demonstrated greater activity than approved EGFR TKIs in vitro and in patient-derived xenograft models of EGFR or HER2 exon 20 mutant NSCLC and in genetically engineered mouse models of NSCLC. In a phase 2 trial, the first 11 patients with NSCLC with EGFR exon 20 mutations receiving poziotinib had a confirmed objective response rate of 64%. These data identify poziotinib as a potent, clinically active inhibitor of EGFR and HER2 exon 20 mutations and illuminate the molecular features of TKIs that may circumvent steric changes induced by these mutations.

Purpose Although programmed death (PD)-1 pathway inhibitors are now used in nearly all patients with advanced non-small-cell lung cancer (NSCLC), the large number of patients with NSCLC and concurrent autoimmune disease (AID) have been universally excluded from immunotherapy clinical trials. Therefore, the safety of PD-1 and PD-ligand 1 (PD-L1) inhibitors in patients with NSCLC and underlying AID is currently unknown. Methods As part of a multi-institutional effort, we retrospectively collected clinicopathologic data from patients with NSCLC and a history of AID who received monotherapy with either a PD-1 or a PD-L1 (herein referred to as PD-[L]1) inhibitor. Qualifying AIDs included but were not limited to: rheumatologic, neurologic, endocrine, GI, and dermatologic conditions. Results We identified 56 patients with NSCLC and an AID who received a PD-(L)1 inhibitor. At the time of treatment initiation, 18% of patients had active AID symptoms and 20% were receiving immunomodulatory agents for their AID. A total of 55% of patients developed an AID flare and/or an immune-related adverse event (irAE). Exacerbation of the AID occurred in 13 patients (23% of the whole cohort), four of whom required systemic corticosteroids. Immune-related adverse events occurred in 21 patients (38%). Among irAEs, 74% were grade 1 or 2 and 26% were grade 3 or 4; eight patients required corticosteroids for irAE management. PD-(L)1 therapy was permanently discontinued in eight patients (14%) because of irAEs. The overall response rate to immunotherapy in this population was 22%. Conclusion In patients with NSCLC with AID treated with a PD-(L)1 inhibitor, exacerbation of AID occurred in a minority of patients. The incidence of irAEs was similar to reported rates in clinical trials where patients with AID were excluded. Adverse events were generally manageable and infrequently led to permanent discontinuation of immunotherapy.