Atezolizumab, bevacizumab, pemetrexed and platinum for EGFR-mutant NSCLC patients after EGFR TKI failure: A phase II study with immune cell profile analysis

Background: Acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) remains a significant hurdle for patients with EGFR-mutated non-small cell lung cancer (NSCLC), particularly those lacking the EGFR^T790M. IMpower 150 study demonstrated promising efficacy for a combination of immune-chemotherapy and bevacizumab in patients with EGFR-mutated NSCLC.

Methods: This open-label, single-arm, phase II trial evaluated the efficacy and immune cell profile of the modified regimen combining atezolizumab, bevacizumab (7.5 mg/kg) and chemotherapy in patients with EGFR-mutated NSCLC following TKI failure. The primary endpoint was objective response rate (ORR). The re-biopsy tissue specimens and serial peripheral blood samples were collected to analyse the immune cell profile and tumour microenvironments.

Rresults: 22 EGFR-mutant NSCLC patients participated in this study. The ORR was 42.9%, with a disease control rate (DCR) of 100%. Median progression-free survival (PFS) was 6.3 months. Patients with programmed death-ligand 1 (PD-L1) expression ≥1% exhibited significantly higher ORR (75 vs. 23.1%; p = .032) and longer PFS (14.0 vs. 6.1 months; p = .022) compared with those with PD-L1 expression < 1%. Grade ≥ 3 adverse events occurred in 40.9% of patients. Higher peritumour nature killer (NK) cell infiltration and lower peripheral helper T cell counts before treatment were associated with favourable ORR and longer PFS, respectively. After disease progression, the proportion of S100A9⁺ myelod-derived suppressor cells (MDSCs) increased, while regulatory T cells decreased.

Conclusion: This modified combination regimen may be a promising therapeutic option for EGFR-mutant NSCLC patients with TKI resistance, especially those with PD-L1-positive tumours. Furthermore, immune cell profiling may aid in identifying patients who may benefit from this approach.

Key points: The combination regimen yielded promising efficacy in NSCLC patients after EGFR-TKI resistance, particularly those with PD-L1-positive tumours. Higher peritumour NK cell and lower peripheral helper T cell were associated with favourable ORR and longer PFS, respectively. After disease progression, the proportion of S100A9⁺ MDSC increased, but Treg cells decreased.