Regeneron’s Phase 3 HARMONY Melanoma trial missed its primary PFS endpoint, but high-dose fianlimab plus cemiplimab showed a numerical 5.1-month median PFS improvement over pembrolizumab in advanced melanoma.
Written By: Farha Farheen, PharmD
Reviewed By: Pharmacally Editorial Team
Regeneron announced updated findings from its Phase 3 clinical trial (NCT05352672) evaluating fianlimab, an investigational LAG-3 inhibitor, in combination with cemiplimab as a first-line treatment for patients with unresectable locally advanced or metastatic melanoma.
Although the study did not achieve statistical significance for its primary endpoint of progression-free survival (PFS), the high-dose regimen demonstrated a numerical 5.1-month improvement in median PFS compared with pembrolizumab monotherapy. The findings support continued evaluation of dual LAG-3 and PD-1 inhibition strategies in advanced melanoma.
Phase 3 Trial Overview
The randomized, double-blind, multicenter Phase 3 study enrolled 1546 patients aged 12 years and older with unresectable locally advanced or metastatic melanoma who had not received prior systemic treatment for advanced disease.
Participants were randomized into four treatment groups. One group received high-dose fianlimab (1600 mg) plus cemiplimab (350 mg) every 3 weeks, while another group received low-dose fianlimab (400 mg) in combination with cemiplimab (350 mg) every 3 weeks. Additional participants received pembrolizumab monotherapy (200 mg) every 3 weeks or cemiplimab monotherapy (350 mg) every 3 weeks.
The primary efficacy comparison evaluated fianlimab plus cemiplimab against pembrolizumab monotherapy. Regeneron stated that the cemiplimab monotherapy arm was included to evaluate the contribution of individual treatment components and was not part of the primary statistical comparison.
Key Efficacy Findings
Patients treated with high-dose fianlimab plus cemiplimab achieved a median PFS of 11.5 months, compared with 6.4 months for pembrolizumab monotherapy, representing a numerical improvement of 5.1 months. The regimen demonstrated a hazard ratio (HR) of 0.845 (95% CI: 0.709–1.008; p=0.0627), approaching but not reaching the predefined threshold for statistical significance.
The low-dose fianlimab plus cemiplimab regimen demonstrated a median PFS of 9.6 months, with an HR of 0.931 (95% CI: 0.773–1.122; p=0.4661). Patients receiving cemiplimab monotherapy achieved a median PFS of 6.3 months.
While the study did not meet its predefined statistical threshold, the numerical PFS improvement observed with the high-dose regimen highlights the continued therapeutic potential of dual immune checkpoint inhibition strategies in melanoma.
The melanoma treatment landscape already includes the approved LAG-3 and PD-1 combination Opdualag, increasing interest in next-generation dual checkpoint inhibitor approaches targeting both pathways.
Overall survival and additional secondary endpoint analyses remain ongoing. Detailed efficacy and safety data from the trial are expected to be presented at an upcoming medical meeting.
Safety Findings
No new safety signals were identified during the study. According to Regeneron, the safety profile of the fianlimab and cemiplimab combination was consistent with the known safety characteristics of immune checkpoint inhibitor therapies.
Ongoing Head-to-Head Phase 3 Trial
Regeneron also confirmed that an ongoing Phase 3 head-to-head study (NCT06246916) is evaluating the high-dose fianlimab plus cemiplimab regimen against Opdualag in patients with first-line unresectable or metastatic melanoma. The comparative study is expected to provide additional insight into the regimen’s efficacy, safety, and potential clinical positioning within the evolving melanoma treatment landscape.
About Fianlimab
Fianlimab is an investigational lymphocyte-activation gene 3 (LAG-3) inhibitor designed to enhance T-cell activity and anti-tumor immune responses when combined with cemiplimab, a PD-1 inhibitor. The combination remains investigational, and neither fianlimab nor the combination regimen has been approved by regulatory authorities for the treatment of melanoma.
Reference
About the Writer
Farha Farheen, PharmD (LinkedIn) is a pharmacy professional with a strong interest in pharmacovigilance and clinical research. She has completed her Doctor of Pharmacy (Pharm.D) along with her internship as a Clinical Pharmacist. She has hands-on experience in adverse drug reaction (ADR) reporting, safety data documentation, and pharmacovigilance workflows, and is proficient in using VigiFlow. She is also a patent holder for an antibacterial formulation enriched with bioactive substances, granted by the German Patent and Trademark Office.