Phase I/II trial of plinabulin in combination with nivolumab and ipilimumab in patients with recurrent small cell lung cancer (SCLC): Big ten cancer research consortium (BTCRC-LUN17-127) study

Background: Plinabulin is a GEF-H1 releasing agent with an immune-enhancing function. We report results from a multicenter Phase I/II study (NCT03575793) assessing plinabulin in combination with nivolumab and ipilimumab for the treatment of recurrent SCLC. Methods: In Phase I, patients were enrolled using a 3 + 3 design to determine dose-limiting toxicities (DLTs) and recommended Phase 2 dose (RP2D). Patients received nivolumab (1 mg/kg), ipilimumab (3 mg/kg), and plinabulin (in escalating doses) on day 1 of each 21-day cycle for 4 cycles followed by maintenance with plinabulin and nivolumab. In phase II, patients with recurrent PD(L)1 inhibitor resistant SCLC were enrolled. The primary objective was median progression-free survival (PFS). Results: Between 9/2018 and 2/2023, 39 patients were enrolled, and 36 patients received study treatment and were evaluable for safety (16 in Phase I; 20 in Phase II). In the phase I dose-escalation, there were 2 DLTs; grade 3 altered mental status lasting <24 h and grade 3 infusion reaction. The Plinabulin RP2D was determined to be 30 mg/m². Common TRAEs were vomiting (44 %), nausea (42 %), and infusion reaction (36 %); 6 % of patients had a ≥grade 3 TRAE. Five patients (14 %) had ≥grade 3 irAEs; there were no cases of immune-related pneumonitis. In the efficacy analysis in 27 patients, the median PFS was 1.6 months (95 % CI 1.2 to 2.7) and the trial did not meet the pre-specified target median PFS of 3.5 months. Four patients treated at 30 mg/m² had PR (confirmed 1, unconfirmed 3); 5 patients had SD with a CBR of 33 %. Two of 8 patients treated in phase I at the lower 20 mg/m² dose had confirmed PR, with 1 patient on the drug regimen for >90 cycles. The median OS and follow-up time were 5.5 months and 2.5 months respectively. Conclusions: Plinabulin in combination with nivolumab and ipilimumab was tolerable at the dose of 30 mg/m². While the clinical responses in PD-1 resistant SCLC were limited, some patients had a long duration of response. The number of ≥grade 3 irAE with the combination were lower than expected.