400P Phase I study of fianlimab, a human lymphocyte activation gene-3 (LAG-3) monoclonal antibody, in combination with cemiplimab in advanced melanoma (mel)

Concurrent blockade of LAG-3 may enhance efficacy anti-programmed cell death-1 (PD-1) therapies. We present updated safety and clinical activity data from patients (pts) with advanced mel treated concurrent anti-LAG-3 (fianlimab) anti-PD-1 (cemiplimab). This Phase 1 study included pts unresectable or metastatic (excluding uveal mel) who were anti–PD-ligand (L)1 treatment naïve (expansion cohort [EC] 6) anti–PD-(L) experienced within 3 months screening (EC7). Pts received fianlimab 1600 mg + cemiplimab 350 intravenously every weeks for 12 (optional extra if clinically indicated). Tumour measurements taken 6 24 weeks, then 9 weeks. As the Feb 2022 cutoff date, 40 EC6 15 EC7 enrolled cemiplimab. For cohorts respectively, median age was 69.5 59.0 years, 62.5% 46.7% male, 90.0% 60.0% White. Median duration 37.1 (EC6) 9.0 Grade ≥3 treatment-emergent adverse events (TEAEs) occurred in 37.5% (EC7) pts; serious TEAEs 32.5% 33.3% 17.5% 13.3% discontinued due to a TEAE. Rate adrenal insufficiency 12.5% 6.7% (EC7); none led discontinuation. Investigator-assessed objective response rate (6 complete responses; 19 partial responses [PRs]) (2 PRs) pts. Kaplan-Meier estimation progression-free survival 14.2 (95% CI: 5.6–not estimated) 1.4 1.3–7.7) had not been reached both cohorts. PD-L1 correlative biomarkers analysis will be presentation. Fianlimab similar profile anti–PD-1 agents; anti-PD-(L)1-naïve appears higher than previously reported monotherapy anti–LAG-3 anti–PD-1. A phase trial (NCT05352672) investigating is ongoing.