Regeneron Fianlimab Trial Misses PFS Goal

Regeneron Pharmaceuticals Inc. said in a May 15, 2026 press release that its Phase 3 fianlimab trial failed to achieve statistical significance for progression-free survival (PFS), a key pipeline setback that prompted analysts to revise models and price targets.

Phase 3 Trial Results and Design

Regeneron reported that its randomized, double-blind Phase 3 trial tested fianlimab, a LAG-3 inhibitor, combined with cemiplimab, a PD-1 inhibitor, at two dose levels against pembrolizumab (Keytruda) monotherapy in 1,546 previously untreated patients aged 12 and older with unresectable locally advanced or metastatic melanoma. The trial also included a cemiplimab monotherapy arm as a noncomparative reference.

The trial did not reach statistical significance on its primary endpoint of improved PFS compared with pembrolizumab. Median PFS was 11.5 months for the high-dose fianlimab plus cemiplimab combination, 9.6 months for the low-dose combination, 6.4 months for pembrolizumab, and 6.3 months for the cemiplimab reference arm. Hazard ratios versus pembrolizumab were 0.845 (95% confidence interval 0.709–1.008; nominal p = 0.0627) for the high-dose arm and 0.931 (p = 0.4661) for the low-dose arm, indicating a numerical but not statistically significant advantage for the higher dose.

No new safety signals emerged with the fianlimab combination. Regeneron also noted that a separate ongoing Phase 3 head-to-head trial is comparing the high-dose fianlimab plus cemiplimab regimen against Bristol Myers Squibb’s Opdualag (nivolumab plus relatlimab).

Analyst Reaction and Pipeline Outlook

Analysts described the trial outcome as a significant setback for Regeneron’s pipeline, part of a series of late-stage challenges. BMO Capital Markets and Evercore removed fianlimab melanoma revenue assumptions from their models, which had previously implied risk-adjusted peak sales of about $1.8 billion and $900 million, respectively. At least ten brokerages cut price targets following the data. Bank of America maintained a Buy rating with an $860 target, emphasizing the broader value of Regeneron’s pipeline beyond melanoma.

Analysts highlighted other late-stage assets as increasingly central to Regeneron’s investment case, including two Factor XI antibodies, the cemdisiran-pozelimab program, and ophthalmology candidates. BMO noted an initial pivotal Factor XI data readout expected in 2027, with additional milestones anticipated in coming years.

Regeneron described the fianlimab and cemiplimab combination as investigational, with regulatory approval and commercial launch uncertain. The company did not provide fianlimab-specific revenue guidance and referred to its most recent Form 10-K and Form 10-Q filings for corporate guidance and risk factors, including potential changes to drug-pricing rules and ongoing legal proceedings.

“The trial did not reach statistical significance for the primary endpoint of improvement in progression-free survival (PFS) compared to pembrolizumab (PD-1 inhibitor) monotherapy,” Regeneron said in the May 15 press release. “No new safety signals were identified with the fianlimab combination.”