Regeneron Pharmaceuticals has reported that its Phase III trial assessing fianlimab (a LAG-3 inhibitor) and cemiplimab (a PD-1 inhibitor) for metastatic melanoma failed to reach statistical significance for the primary endpoint.

This combination is evaluated as a first-line treatment for patients with unresectable locally advanced or metastatic melanoma.

The double-blind, randomised trial tested two dosing regimens against pembrolizumab (another PD-1 inhibitor) monotherapy, focusing on the primary endpoint of progression-free survival (PFS).

It did not achieve statistical significance in PFS improvement when compared to pembrolizumab monotherapy.

Regeneron confirmed that no new safety signals were observed with the fianlimab combination in this clinical setting.

A separate, ongoing head-to-head Phase III trial is evaluating the high-dose fianlimab combination against Opdualag (nivolumab and relatlimab-rmbw) in first-line unresectable or metastatic melanoma.

The company noted that the potential uses of fianlimab and cemiplimab remain investigational, and neither the safety nor the efficacy of this combination has been assessed by regulatory authorities.

The trial enrolled 1,546 patients aged 12 years or above with previously untreated, unresectable locally advanced or metastatic melanoma.

Patients received one of four regimens: 1,600mg fianlimab plus 350mg cemiplimab (high-dose), 400mg fianlimab plus 350mg cemiplimab (low-dose), every three weeks.

The other regimens were placebo with 200mg pembrolizumab or a placebo with 350mg cemiplimab, for the same duration.

Cemiplimab served as a reference in certain components but was not used in direct statistical comparisons.

Further information will be provided when the data is released at an upcoming medical event.

In September 2025, Regeneron’s first-in-class investigational allergen-blocking monoclonal antibodies (mAbs) met their primary endpoints in two Phase III trials involving adults with moderate-to-severe cat or birch allergies.