198P - Adebrelimab with concurrent chemoradiation (cCRT) for limited-stage small cell lung cancer (LS-SCLC): Safety run-in results of a phase III trial

Background

cCRT is the standard of care in LS-SCLC, but LS-SCLC still represents a significant unmet medical need with a median survival of 25 to 30 mo. Addition of the anti-PD-L1 antibody adebrelimab to carboplatin and etoposide has demonstrated survival benefits in extensive-stage SCLC in the phase 3 CAPSTONE-1 trial. This ongoing, 2-stage, phase 3 study aims to evaluate cCRT with adebrelimab in LS-SCLC.

Methods

In the safety run-in stage, patients with pathologically confirmed, unresectable LS-SCLC were enrolled. Treatment consisted of four 3-week cycles of adebrelimab (20 mg/kg, iv, d1, Q3W) plus carboplatin (AUC 5, iv, d1, Q3W) and etoposide (100 mg/m², iv, d1, 2, 3, Q3W), with thoracic radiotherapy started on cycle 3 (60 Gy/2 Gy, QD, 6 weeks). Following cCRT, patients received maintenance adebrelimab (20 mg/kg, iv, Q3W) until disease progression or unacceptable toxicities. The primary endpoint was safety.

Results

In the safety run-in stage, 28 patients were enrolled and all received adebrelimab with cCRT. As of Oct. 31, 2023, median follow-up was 29.4 mo (range 6.5-33.3). Grade ≥3 TRAEs occurred in 27 (96.4%) patients; all events with an incidence of ≥10% were hematological toxicities. Four (14.3%) patients had treatment-related pneumonitis and one (3.6%) had treatment-related immune-mediated lung disease (all grade 2). TRAEs led to treatment discontinuation in one (3.6%; infusion-related reactions) patient. There were no deaths due to TRAEs. Confirmed ORR was 92.9% (26/28; 95% CI 76.5-99.1) and DCR was 100% (28/28; 95% CI 87.7-100). Among responders, median DoR was 20.1 mo (95% CI 7.7-not reached [NR]; 11/26 responses ongoing). Median PFS was 17.9 mo (95% CI 8.8-NR). Median OS was NR and the OS rate at 2 years was 64.3% (95% CI 43.8-78.9).

Conclusions

In the safety run-in stage, adebrelimab with cCRT showed acceptable tolerability and favorable efficacy outcomes in LS-SCLC. The randomized, double-blind, placebo-controlled stage of the trial is ongoing to further assess the regimen.

Clinical trial identification

NCT04691063.

Legal entity responsible for the study

Jiangsu Hengrui Pharmaceuticals Co., Ltd.

Funding

Jiangsu Hengrui Pharmaceuticals Co., Ltd.

Disclosure

J. Zhang, K. Ma, L. Yang: Financial Interests, Personal, Full or part-time Employment: Hengrui. All other authors have declared no conflicts of interest.