Regeneron faces securities class action over melanoma trial disclosures
Hagens Berman says investors can join a proposed class action tied to Regeneron’s fianlimab and Libtayo melanoma trial after the study missed its main goal.
A PR Newswire release from Hagens Berman says a securities class action has been filed against Regeneron Pharmaceuticals over disclosures tied to a Phase 3 melanoma trial of fianlimab in combination with Libtayo.
The release says the suit involves investors who bought Regeneron common stock between Aug. 1, 2025, and May 15, 2026. It says the trial later missed its primary endpoint, progression-free survival, after the company disclosed a protocol change and later said the study did not reach statistical significance.
According to the release, the case centers on a first-line treatment study for metastatic or locally advanced melanoma. The suit alleges Regeneron made false and misleading statements and failed to disclose that the study’s preliminary statistical assumptions were flawed, that the active treatment arm was not meaningfully outperforming standard therapies, and that success on the primary endpoint was unlikely.
The release says Regeneron first said on April 29, 2026, that it would alter the trial protocol so the main progression-free survival analysis would include all enrolled patients with at least six months of follow-up. It says the company later stated on May 12, 2026, that the protocol change reflected slow event rates and had been submitted to global regulators in the November/December timeframe about six months earlier.
On May 15, 2026, Regeneron said the trial did not reach statistical significance on the primary endpoint of improvement in progression-free survival, according to the release. The release also says the news sent Regeneron shares lower and erased about $11 billion in market value.
Hagens Berman partner Reed Kathrein is quoted in the release as saying the firm is focused on whether Regeneron altered the trial protocol without timely telling investors. The release does not include a response from Regeneron.
The legal notice says the lead plaintiff deadline is Sept. 14, 2026. It also says the proposed class period runs from Aug. 1, 2025, through May 15, 2026.
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