First-in-human study of REGN3767 (R3767), a human LAG-3 monoclonal antibody (mAb), ± cemiplimab in patients (pts) with advanced malignancies
Papadopoulos KP, Lakhani NJ, Johnson ML, Park H, Wang D, Yap TA, Dowlati A, Maki RG, Lynce F, Ulahannan SV, Kelly K, Sims TN, Bredlau AL, Bramble D, Ortiz AG, Zhu M, Chen H, Karasarides M, and Kroog G. First-in-human study of REGN3767 (R3767), a human LAG-3 monoclonal antibody (mAb), ± cemiplimab in patients (pts) with advanced malignancies. J Clin Oncol 2019; 37.
J Clin Oncol
Background: We present initial safety, pharmacokinetics (PK), and efficacy from the dose escalation study of R3767, alone (mono) or in combination with cemiplimab (REGN2810), a PD-1 mAb (combo), in pts with advanced malignancies (NCT03005782). Methods: Pts who had progressed on prior therapy(ies) and/or for whom no therapy with clinical benefit was available were enrolled; most pts had received no prior anti-PD-1/PD-L1. Pts received R3767 1, 3, 10, or 20 mg/kg every 3 weeks (Q3W) ± cemiplimab 3 mg/kg or 350 mg Q3W IV for ≤51 weeks. Crossover from mono to combo was allowed at progression. R3767 PK were evaluated. Tumor measurements were performed Q6W for the first 24 weeks and subsequently Q9W. Data cut-off date was Aug 25, 2018. Results: Mono: 27 pts (median age: 66 yr; ECOG PS: 0 [n=4], 1 [n=23]) were treated. There were no dose-limiting toxicities (DLTs). The most common treatment-emergent adverse event (TEAE) was nausea (22.2%). Grade ≥3 immune-related adverse events (irAEs) of increased alanine and aspartate aminotransferases (each 3.7%) were reported. By investigator-assessment (per RECIST 1.1; INV), best response was stable disease in 11 pts. Combo: 42 pts (median age: 60 yr; ECOG PS: 0 [n=15], 1 [n=27]) were treated. One pt treated with R3767 3 mg/kg Q3W + cemiplimab 3 mg/kg Q3W experienced DLT of grade 4 elevated blood creatine phosphokinase, associated with grade 3 myasthenia syndrome and grade 1 elevated troponin. The most common TEAEs were fatigue (33.3%) and nausea (21.4%). Grade 3 irAE of hypothyroidism (2.4%) was also reported. By INV, 2 (both small cell lung cancer) combo pts and 2 (endometrial cancer and cutaneous squamous cell carcinoma) of 12 additional pts who crossed over from mono to combo had partial responses. PK: R3767 concentrations in serum increased in a dose-dependent manner and were unaffected by combo. Conclusions: The safety profile of R3767 ± cemiplimab was generally tolerable; PK was linear. Early efficacy signals were detected despite the difficult-to-treat pt population. Biomarker studies are ongoing. R3767 20 mg/kg or 1600 mg fixed dose equivalent Q3W as mono and combo were selected for further evaluation.