Story perspectives

Regeneron Shares Drop 12% as Melanoma Trial Misses Endpoint

5/19/2026

Summary

Regeneron Shares Fall

Regeneron shares fell 12% to $612.06 on Monday, erasing about $9 billion in market value after its late-stage melanoma trial missed the primary endpoint.
The phase III trial of high-dose fianlimab plus cemiplimab in 1,546 patients did not achieve statistically significant progression-free survival versus Merck’s Keytruda (median 11.5 vs 6.4 months; p-value 0.0627).
At least ten brokerages cut their price targets on Regeneron stock following the results.

Summary

Regeneron Trial Miss

Regeneron’s fianlimab failed to meet its trial endpoints, adding to mixed outcomes for LAG-3 inhibitors.
Analysts say the $1.6-$1.8 billion market forecast for a successful LAG-3 melanoma therapy is now uncertain.
Regeneron’s oncology franchise, anchored by Libtayo’s over $1 billion annual sales, now faces pressure to grow without a new LAG-3 partner.
Upcoming Eylea biosimilar launches later this year could further challenge Regeneron’s core revenue streams.

Summary

Regeneron Halts LAG-3

Regeneron has halted development of fianlimab for first-line non-small cell lung cancer after a phase 2 failure.
The stoppage leaves patients reliant on existing PD-1/PD-L1 drugs because no alternative LAG-3 regimen is forthcoming.
Immutep’s eftilagimod alfa and MSD’s favezelimab were discontinued after trials, leaving Bristol Myers Squibb’s Opdualag as the sole approved LAG-3 therapy.
Patient groups warn that the dwindling LAG-3 candidates could delay immunotherapy for melanoma and lung cancer.

History

Historical Context

In September 2014 the U.S. FDA approved Merck’s pembrolizumab (Keytruda) for advanced melanoma, the first PD-1 checkpoint inhibitor and a catalyst for immunotherapy growth, including Bristol-Myers Squibb’s nivolumab. By June 2016 Merck was running about 270 trials in roughly 30 cancers, illustrating rapid expansion of checkpoint-blockade programs. The drug’s sales rose to $29.5 billion in 2024, cementing checkpoint blockade as a dominant cancer-treatment paradigm.

1 of 4

Regeneron Shares Fall

Regeneron shares fell 12% to $612.06 on Monday, erasing about $9 billion in market value after its late-stage melanoma trial missed the primary endpoint.
The phase III trial of high-dose fianlimab plus cemiplimab in 1,546 patients did not achieve statistically significant progression-free survival versus Merck’s Keytruda (median 11.5 vs 6.4 months; p-value 0.0627).
At least ten brokerages cut their price targets on Regeneron stock following the results.

1 / 4