A phase 1/2 study of REGN7075 (EGFRxCD28 costimulatory bispecific antibody) in combination with cemiplimab (anti-PD-1) in patients with advanced solid tumors: Trial-inprogress update.

TPS277 Background: There is a need to develop novel immunotherapeutic approaches to enhance responses to immune checkpoint blockade. REGN7075 is a human costimulatory bispecific antibody designed to bridge epidermal growth factor receptor (EGFR)-expressing tumor cells with CD28-positive T cells to support further T-cell activation by endogenous tumor antigens. Methods: This is an open-label, Phase 1/2, first-in-human study evaluating the safety, tolerability, pharmacokinetics, and preliminary anti-tumor activity of REGN7075 (EGFRxCD28) alone and in combination with cemiplimab (anti-programmed cell death [PD]-1) in patients with advanced solid tumors (NCT04626635). This study includes a dose-escalation (Bayesian optimal interval design; Part 1) and a dose-expansion phase (Part 2). Patients must have a protocol-defined advanced solid tumor, have an Eastern Cooperative Oncology Group performance status of 0 or 1, and be naive to anti–PD-1/anti–PD-ligand(L)1 therapy in the dose-expansion phase. In Part 1, heavily pre-treated patients with advanced solid tumors receive a lead-in of REGN7075 monotherapy every week for 3 weeks followed by combination therapy with cemiplimab 350 mg every 3 weeks. Planned dose levels (DLs) of REGN7075 are 0.03, 0.1, 0.3, 1, 3, 10, 30, 100, 300, and 900mg. Once the recommended Phase 2 dose is determined in Part 1, five tumor-specific expansion cohorts will be opened in Part 2: colorectal cancer (microsatellite stable [MSS-CRC]), non-small cell lung cancer (NSCLC, PD-L1 ≥50%), triple-negative breast cancer, cutaneous squamous cell carcinoma, and head and neck squamous cell carcinoma (PD-L1 combined positive score ≥1). Patients with MSS-CRC with RAS or BRAF wild type mutations must have received anti-EGFR therapy or anti-vascular endothelial growth factor (VEGF therapy). Primary endpoints are safety and tolerability of REGN7075 alone or in combination with cemiplimab for Part 1, and objective response rate per Response Evaluation Criteria in Solid Tumors version 1.1 for Part 2. For Part 2, a secondary objective is to assess the effect of REGN7075 on patient-reported outcomes as measured by several validated instruments including the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30), and EORTC QLQ-CR29 (CRC patients only). Approximately 400 patients will be enrolled in this phase 1/2 study, including ~80 patients in Part 1 and ~320 patients in Part 2 (including ~70 in the CRC cohort). As of September 13, 2022, 30 patients were treated in the dose-escalation phase, up to the 300 mg DL for REGN7075 in combination with cemiplimab. This study is ongoing and currently open to enrollment. Clinical trial information: NCT04626635 .