Anti-LAG-3 antibody LBL-007 in combination with toripalimab in patients with unresectable or metastatic melanoma: A phase., open-label, multicenter, dose escalation/expansion study.

9538 Background: LBL007 is a novel, fully human IgG4 monoclonal antibody targeting human Lymphocyte-activation gene3 (LAG-3). Dual inhibition of anti-programmed cell death protein 1 (PD-1) and LAG-3 is anticipated to synergistically increase immune response against tumor growth. Here we report the preliminary safety and efficacy of LBL-007 in combination with Toripalimab (an anti-PD-1 antibody has approved for treatment of melanoma in China) in patients (pts) with unresectable or metastatic melanoma. Methods: Pts with unresectable or metastatic melanoma with or without prior anti-PD-(L)1 therapy were enrolled. This trial comprised 2 parts, namely part 1 (dose escalation), pts received LBL-007 (0.25/1/3/6 mg/kg) /Toripalimab (3 mg/kg) both i.v., Q2W; and part 2 (expansion), pts received LBL-007 (3/6 mg/kg)/Toripalimab (3 mg/kg) both i.v., Q2W. The primary objective was safety, the second objectives included pharmacokinetics, pharmacodynamics and efficacy (per RECIST 1.1). Results: By Jan 2022, 37 pts (15 [40.5%] male, median age 59 [range 31-74] years, 9 pts [24.3%] with baseline LDH elevation, 18 [48.6%] with acral, 12 [32.4%] mucosal, 5 [13.5%] nonacral cutaneous, 2 [5.4%] primary site unknown) were enrolled, with 17 in part 1 and 20 in part 2. No dose-limiting toxicity was observed in part 1, and the MTD was not reached. Of all 37 pts, the most common treatment-emergent adverse events (TEAEs) included anemia (24.3%), creatine phosphokinase elevation (24.3%), hypothyroidism (21.6%), and aspartate aminotransferase elevation (21.6%). For 32 radiologically evaluable pts, ORR was 12.5%, DCR was 53.1%. In a preplanned subtype-specific analysis in anti-PD-(L)1 treatment-naïve pts, ORR was 27.3 % vs. 0%, and DCR was 81.8% vs. 50.0% in acral and mucosal melanoma subtypes, respectively. For anti-PD-(L)1-resistant pts (n = 11), DCR was 18.2%. Conclusions: LBL007/Toripalimab combination is well tolerated and promising efficacy in pts with unresectable or metastatic melanoma, especially in the acral type without prior anti-PD-(L)1 therapy. Clinical trial information: NCT04640545.