Hagens Berman says investors filed suit over Regeneron melanoma trial disclosures
The firm says the lawsuit concerns Regeneron’s Phase 3 melanoma trial, which it says failed to hit its main goal after protocol changes and slower event rates.
Hagens Berman said on Sept. 1, 2026, that a securities class action has been filed against Regeneron Pharmaceuticals, Inc. over disclosures tied to its Phase 3 trial of Fianlimab in combination with Libtayo for first-line treatment of metastatic or locally advanced melanoma.
The firm says the case centers on alleged false and misleading statements and failures to disclose information about the study before Regeneron said on May 15, 2026, that the trial did not reach statistical significance on its primary endpoint of progression-free survival, or PFS.
According to the press release, the class period runs from Aug. 1, 2025, through May 15, 2026, and investors seeking to serve as lead plaintiff have until Sept. 14, 2026.
The announcement says the trial news sent Regeneron shares sharply lower and wiped about $11 billion from market value.
The study’s main endpoint was PFS, a measure of how long patients live without their cancer getting worse, according to the press release. The source says the event criteria were disease progression or death.
The announcement says Regeneron had described the combination as a “potential blockbuster.” It also says the company repeatedly sounded upbeat about the trial even as event rates slowed.
Hagens Berman’s account says Regeneron first disclosed on April 29, 2026, that it had decided to alter the trial protocol so the primary PFS analysis would include all enrolled patients with at least six months of follow-up. On May 12, 2026, the company said the change was made in response to “slow event rates” and had been submitted to global regulators in the November/December timeframe, according to the press release.
The firm’s press release says the complaint alleges Regeneron made misleading statements and failed to disclose critical information. It also says the complaint alleges the company’s preliminary statistical assumptions were flawed, that the active-treatment arm was not showing meaningful separation from standard therapies and that success on the primary endpoint had become unlikely.
Hagens Berman partner Reed Kathrein was quoted as saying the firm is focused on whether Regeneron altered the protocol without telling investors in time because management knew the combination’s blockbuster potential was not really there.
The press release also says the SEC whistleblower program may award original information up to 30% of a successful SEC recovery.
Investors who held Regeneron shares during the class period have until Sept. 14, 2026, to seek appointment as lead plaintiff.
Sources
Editorial note: This article was prepared with AI assistance and includes source attribution for reader review.
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