A multi-center phase II study of toripalimab with chemotherapy in patients with EGFR mutant advanced NSCLC patients resistant to EGFR TKIs: Efficacy and biomarker analysis.

Abstract

e21618 Background: Immune checkpoint blocker (ICB) monotherapy showed a lack of response in advanced NSCLC patients with EGFR mutations. This Phase II study aimed to evaluate the efficacy and safety of toripalimab, a humanized PD-1 mAb plus platinum doublets chemotherapy in EGFR mutant advanced NSCLC patients, who developed resistance to 1st/2nd generation of EGFR TKIs and without T790M mutation. Methods: Patients received toripalimab (240 or 360 mg) intravenously combined with carboplatin (AUC = 5) and pemetrexed (500mg/m2) on day 1, Q3W, for up to 6 cycles, followed by toripalimab and pemetrexed maintenance until disease progression or unacceptable toxicity. Efficacy was evaluated every six weeks according to RECIST v1.1. PD-L1 expression (JS311 assay) and co-mutation status by whole exome sequencing were further analyzed. Results: From Apr 2018 to March 2019, 40 patients were enrolled from 8 centers in China. The median age was 57 years with 53% female, 57.5% EGFR exon19 deletion and 42.5% L858R mutation. By the cutoff date of Jan 2, 2020, 20 partial response and 15 stable disease were observed (ORR 50% and DCR 87.5%) with a median DOR of 7.0 months. The median PFS was 7.0 months and the median OS was still not reached. 52.6% (20/38) patients were PD-L1+ (TPS≥1%) and had numerically higher ORR (60% vs 39%, p= 0.33) and longer PFS (median 8.3 vs 5.7 months, p= 0.61) than PD-L1- patients. Co-mutations analysis revealed common genetic alternations including TP53 (79%), RB1 (18%), ERBB2 (15%), PIK2CA (12%), CDKN2A (12%), HDAC9 (12%) and MET (9%). Patients with TP53 co-mutation responded significantly better in ORR than TP53 wild type patients (62% vs 14%, p= 0.04) . Most frequent TRAE included leukopenia (78%), neutropenia (70%), anemia (70%), ALT elevation (48%), AST elevation (48%) and nausea (48%). Grade 3+ TRAE occurred in 55% patients, including neutropenia (43%), leukopenia (20%) and anemia (13%). Dose delay due to TRAE occurred in 40% patients while 10% patients discontinued treatment due to TRAE. Conclusions: Toripalimab in combination with chemotherapy showed promising anti-tumor activity with a manageable safety profile for advanced NSCLC patients with EGFR mutations refractory to TKI therapies. Patients with PD-L1+ tumor biopsy or TP53 co-mutation preferentially responded to the combination. A randomized phase III trial is ongoing to further validate the finding in this study (NCT03924050). Clinical trial information: NCT03513666.