RESILIENT part 1: a phase 2 dose-exploration and dose-expansion study of second-line liposomal irinotecan in adults with small cell lung cancer

Background: RESILIENT (NCT03088813) is a phase 2/3 study assessing the safety, tolerability, and efficacy of liposomal irinotecan monotherapy in patients with small cell lung cancer and disease progression on/after first-line platinum-based therapy. Here, we present results from RESILIENT part 1. Methods: This open-label, single-arm, safety run-in evaluation with dose-exploration and dose-expansion phases included patients ≥18 years old with Eastern Cooperative Oncology Group performance status of 0/1; those with asymptomatic central nervous system metastases were eligible. The primary objectives were to evaluate safety and tolerability and recommend a dose for further development. Efficacy end points were objective response rate (ORR), progression-free survival (PFS), and overall survival (OS). Results: During dose exploration, 5 patients received intravenous liposomal irinotecan at 85 mg/m² (deemed not tolerable; dose-limiting toxicity) and 12 patients received 70 mg/m² (deemed tolerable). During dose expansion, 13 additional patients received intravenous liposomal irinotecan at 70 mg/m². Of these 25 patients (median age [range], 59.0 [48.0-73.0] years, 92.0% with metastatic disease), 10 experienced grade ≥3 treatment-related treatment-emergent adverse events (TEAEs), most commonly diarrhea (20.0%) and neutropenia (16.0%), and 3 had serious treatment-related TEAEs, of whom 2 died. ORR was 44.0% (95% confidence interval [CI]: 24.40-65.07; 1 complete response, 10 partial responses) and median (95% CI) PFS and OS were 3.98 (1.45-4.24) months and 8.08 (5.16-9.82) months, respectively. Conclusion: Overall, no new safety signals were identified with liposomal irinotecan, and antitumor activity was promising. RESILIENT part 2, a randomized, controlled, phase 3 study of liposomal irinotecan versus topotecan, is ongoing. Lay Summary: Small cell lung cancer (SCLC) is an aggressive disease with few treatment options after platinum-based therapy. Administering 1 option, irinotecan, as a “liposomal” formulation, may extend drug exposure and improve outcomes. The RESILIENT part 1 trial assessed the safety and efficacy of liposomal irinotecan in 25 adults with SCLC after disease progression despite platinum-based therapy. No new safety concerns were reported. The most common moderate-to-severe side effects were diarrhea (20% of patients) and neutropenia (16%). Tumors responded to treatment in 44% of patients. Average survival was 8.08 months, and time to disease progression was 3.98 months. Liposomal irinotecan trials are ongoing.