Phase I/II data for Regeneron Pharmaceuticals’ costimulatory bispecific antibody were disappointing, with only one complete response when used as a combination treatment with Libtayo for solid tumors.
Regeneron Pharmaceuticals on Thursday released early data from the ongoing Phase I/II study of its investigational bispecific antibody REGN7075, demonstrating underwhelming treatment response results in patients with advanced solid tumors.
As of the data cut-off in October 13, 2023, only one patient out of 94 achieved complete response while two showed partial response, according to an abstract published ahead of the American Society of Clinical Oncology annual meeting next week. One additional patient, who had liver metastasis, reached partial response after the cut-off. Nine patients had stable disease.
The resulting overall response rate was 20% while the disease control rate was 80%. Israel Lowy, senior vice president of translational and clinical oncology at Regeneron, in a statement struck an optimistic tote noting that the findings “speak to the potential” of REGN7075 as a treatment for solid tumors.
The early data also “add to a growing body of evidence supporting novel costimulatory bispecifics that are in clinical trials for a range of solid tumors and blood cancers,” Lowy added.
REGN7075 is a first-in-class costimulatory bispecific antibody that works by bridging CD28-positive T cells with tumor cells expressing the EGFR protein. This mechanism of action allows REGN7075 to restore the immune sensitivity of tumor cells and activate the anti-cancer functions of T-cells.
Regeneron’s Phase I/II study is a first-in-human open-label trial testing the investigational antibody, in combination with the company’s PD-1 blocker Libtayo (cemiplimab-rwlc), as a treatment for patients with metastatic and locally advanced solid tumors who have exhausted standard treatment options.
The study has two parts: a Phase I dose-escalation portion, which includes a lead-in period with REGN7075 monotherapy, and a Phase II dose-expansion portion. Beyond efficacy, the primary goal of the early-stage study is to assess the safety and tolerability of the REGN7075 regimen. The candidate’s overall profile was “acceptable,” according to Regeneron.
Almost all patients developed treatment-emergent adverse events (TEAE), though only 35% of participants saw grade 3 or 4 TEAEs. Toxicities deemed related to the study drug arose in 90% of patients, but only 7% of these side effects were grade 3 or 4. In addition, 5% of patients dropped out of the study due to side effects. There have been no treatment-related deaths so far.
Thursday’s readout continues Regeneron’s rough patch in cancer. In March 2024, the pharma failed to secure the FDA’s approval for another bispecific antibody, odronextamab, for the treatment of relapsed or refractory follicular lymphoma and diffuse large B-cell lymphoma. The rejection came despite promising Phase II data for the candidate published in December 2023.
Another Regeneron bispecific, linvoseltamab, returned mixed data in December 2023. In patients with relapsed or refractory multiple myeloma, the candidate elicited a 71% objective response rate but showed high rates of adverse events, with 85% of treated patients experiencing side effects at least grade 3 in severity.
Tristan Manalac is an independent science writer based in Metro Manila, Philippines. Reach out to him on LinkedIn or email him at tristan@tristanmanalac.com or tristan.manalac@biospace.com.
