#San Francisco #Securities Fraud #Regeneron Pharmaceuticals #Hagens Berman

Regeneron Pharmaceuticals' Legal Troubles: A Class Action Overview

Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) has found itself in hot water after revelations regarding a critical Phase 3 clinical trial intended to treat melanoma patients. In the wake of these disclosures, Hagens Berman Sobol Shapiro LLP announced that it is leading a securities class action lawsuit aimed at representing investors who purchased shares of the company from August 1, 2025, to May 15, 2026.

The lawsuit was prompted by the startling failure of Regeneron's clinical trial, which was anticipated to yield promising results and potentially revolutionize treatment options for melanoma. Following the trial's failure, Regeneron saw a dramatic decrease in stock price, wiping out an astonishing $11 billion from its market cap. This led investors to file a class action, accusing the company of securities fraud due to misleading statements and failure to disclose significant issues associated with the trial.

Background of the Case

The litigation centers on what is referred to as the 'Study' – a trial assessing the combination of Fianlimab with Libtayo as a first-line treatment approach for advanced melanoma. Regeneron had touted the therapy as a potential blockbuster, with the primary endpoint being progression-free survival (PFS). However, the lawsuit claims that the company made false statements, indicating that the trial was progressing well, despite evidence suggesting otherwise.

Throughout the class period, Regeneron appeared optimistic about the outcome of the trial, assuring investors that the therapy would yield significant benefits. However, as clinical trial events slowed, management's confidence seemed misplaced. In a notable moment, Regeneron management communicated that the lesser-than-expected progression meant their trial arms were performing better than anticipated.

Key Events Leading Up to the Lawsuit

The truth regarding the trial's performance began to surface on April 29, 2026, when Regeneron announced adjustments to the trial protocol. This change involved considering all patients enrolled with a minimum six-month follow-up for the primary analysis, which raised eyebrows among analysts questioning if the original assumptions were flawed. The alterations indicated possible shortcomings in the trial’s effectiveness that Regeneron had been previously underreporting.

Then, on May 12, 2026, the company confessed to adjusting the protocol due to