NextCure, Inc.

Osimertinib has exhibited impressive efficacy in advanced EGFR-mutated NSCLC; however, resistance is inevitable. We hypothesized that local ablative therapy (LAT) for oligoprogressive disease (up to five sites), followed by osimertinib rechallenge, would be safe and provide additional second progression-free survival (PFS2) benefit.

This prospective phase 2 trial enrolled EGFR-mutated NSCLC patients in three cohorts: tyrosine kinase inhibitor (TKI)-naive (cohort 1), previously treated with TKI and developed acquired T790M resistance mutation (cohort 2), or previously treated with osimertinib and developed resistance (cohort 3). Patients in cohorts 1 and 2 received upfront osimertinib followed by LAT on oligoprogression, followed by osimertinib rechallenge. Cohort 3 patients underwent LAT on enrollment, followed by osimertinib rechallenge. The primary end points were safety, tolerability, and PFS2 among the patients who underwent LAT across all three cohorts combined. Secondary end points were PFS1 and overall response rates.

A total of 37 patients with EGFR-mutated NSCLC were enrolled; 25 in cohort 1, nine in cohort 2, and three in cohort 3. A total of 21 patients received LAT across all three cohorts combined, yielding a median PFS2 of 3.7 months (95% confidence interval: 1.9-4.6 mo) for this population. A subgroup with exceptionally long PFS2 was identified that achieved lower tumor burden and circulating tumor DNA-negative minimal residual disease of the EGFR clone with osimertinib before undergoing LAT. Most adverse events related to LAT were grades 1 and 2.

This is the first prospective trial exploring local therapy and osimertinib rechallenge on oligoprogression on osimertinib. Interim analysis revealed that PFS2 in the intention-to-treat patients did not meet its primary goal when compared with historical data on continuation of first-generation EGFR TKIs after LAT. However, definite LAT can be carefully considered in patients using circulating tumor DNA-negative minimal residual disease status as a biomarker for predicting who will benefit from continuation of osimertinib post-LAT.

T cells are often absent from human cancer tissues during both spontaneously induced immunity and therapeutic immunotherapy, even in the presence of a functional T cell–recruiting chemokine system, suggesting the existence of T cell exclusion mechanisms that impair infiltration. Using a genome-wide in vitro screening platform, we identified a role for phospholipase A2 group 10 (PLA2G10) protein in T cell exclusion. PLA2G10 up-regulation is widespread in human cancers and is associated with poor T cell infiltration in tumor tissues. PLA2G10 overexpression in immunogenic mouse tumors excluded T cells from infiltration, resulting in resistance to anti–PD-1 immunotherapy. PLA2G10 can hydrolyze phospholipids into small lipid metabolites, thus inhibiting chemokine-mediated T cell mobility. Ablation of PLA2G10’s enzymatic activity enhanced T cell infiltration and sensitized PLA2G10-overexpressing tumors to immunotherapies. Our study implicates a role for PLA2G10 in T cell exclusion from tumors and suggests a potential target for cancer immunotherapy.

MET pathway activation is one of the most common mechanisms of resistance to osimertinib in EGFR-mutant non–small cell lung cancer (NSCLC). We previously demonstrated spatial and temporal heterogeneity in MET pathway activation upon osimertinib resistance in EGFR-mutant NSCLC; however, the functional relevance of these findings is unclear. Here, we generated 19 patient-derived xenografts (PDX) from 9 patients with multi-region and temporal sampling of osimertinib-resistant tumor tissue from patients with EGFR-mutant NSCLC. MET pathway activation was a putative mechanism of osimertinib resistance in 66% (n = 6/9) patients from whom PDXs were generated. Significant spatial and temporal heterogeneity in MET pathway activation was evident. Osimertinib-resistant PDXs with MET amplification by FISH (defined as MET/CEP7 ratio ≥2.0 or mean MET ≥ 6.0 copies/cell) and high-level phospho-MET, but not c-MET expression, had better responses to osimertinib and savolitinib combination than to osimertinib alone. MET polysomy tumors by FISH from both PDXs and patients had evidence of subclonal phospho-MET expression. Select MET polysomy PDX tumors with phospho-MET expression responded better to osimertinib and savolitinib combination than MET polysomy PDX tumors without phospho-MET expression. Our results suggest osimertinib and savolitinib combination is most effective for osimertinib-resistant EGFR-mutant tumors with MET pathway activation as evidenced by phospho-MET. As subclonal MET amplification may be evident in MET polysomy tumor progression, MET polysomy warrants close clinical follow-up with phospho-MET IHC in parallel with FISH diagnostic.

Using a novel cohort of in vivo PDX models of MET pathway activation with acquired resistance to osimertinib in EGFR-mutant lung cancer, we demonstrate that phospho-MET may be a clinically relevant assay to guide treatment selection with osimertinib and savolitinib combination. In addition, our work shows that patients with MET polysomy tumors may have subclonal MET amplification and therefore require close follow up for the use of osimertinib and savolitinib combination.