P3.02c-046 Safety, Clinical Activity and Biomarker Results from a Phase Ib Study of Erlotinib plus Atezolizumab in Advanced NSCLC: Topic: IT

Abstract

Targeted therapy with erlotinib is effective in reducing tumor burden in EGFR-mutant non-small cell lung cancer (NSCLC). However, resistance to therapy develops almost universally. Atezolizumab, an engineered mAb that inhibits binding of PD-L1 to its receptors, PD-1 and B7.1, has demonstrated promising monotherapy activity in NSCLC. Given that atezolizumab may enhance and perpetuate anti-tumor immunity, we hypothesized that combining atezolizumab with erlotinib may improve both clinical response and durability in EGFR-mutant NSCLC. This Phase Ib study consisted of a safety-evaluation stage in patients with NSCLC regardless of EGFR status followed by an expansion stage in TKI-naïve patients with tumors harboring activating EGFR mutations. Patients were enrolled regardless of PD-L1 status. After a 7-day run-in with 150mg erlotinib PO QD alone, patients received 150mg erlotinib PO QD and 1200mg atezolizumab IV q3w. To evaluate immune biology, biopsies were obtained in expansion-stage patients pre-treatment, after erlotinib run-in, at weeks 4-6, and at progression. The primary objective was to evaluate the safety and tolerability of the combination. Secondary objectives included evaluation of the clinical activity per RECIST v1.1. Data cutoff, 11 April 2016. Twenty-eight patients (safety stage, n = 8; expansion stage, n = 20) who received ≥ 1 dose of erlotinib or atezolizumab were considered safety evaluable. Median age was 61y (range, 47-84); median survival follow-up was 11.2mo (range, 0.8-24.2). The incidence of either treatment-related G3-4 AEs was 39% and for serious AEs, 50%. The most common atezolizumab-related G3-4 AEs were pyrexia and increased ALT. No pneumonitis was reported. No treatment-related G5 AEs occurred. Five patients discontinued atezolizumab due to treatment-emergent AEs. No DLTs were observed. In the expansion-stage population, ORR was 75% (95% CI, 51-91). Disease control rate (CR + PR + SD ≥ 24 weeks) was 90% (95% CI, 68-99), median PFS was 11.3mo (95% CI, 8.4-NE) and median DOR was 9.7mo (range, 4.2-11.7). Increases in intratumoral CD8+ T cells post-erlotinib run-in were observed in 8/13 evaluable paired biopsies. Higher intratumoral CD8+ T-cell prevalence and immune gene expression signatures at baseline were associated with improved PFS. The combination of full dose erlotinib plus atezolizumab demonstrated a manageable safety profile. While response rates and median PFS for combination treatment appear similar to those observed with erlotinib monotherapy, the addition of atezolizumab to erlotinib may lead to more durable clinical responses in some patients. Additional follow-up is required to evaluate the full potential of this combination treatment. NCT02013219.