The legal action, filed by Pomerantz LLP, targets Regeneron’s conduct during a period when the company faced significant scrutiny over trial efficacy. On April 29, 2026, Regeneron revealed during an earnings call that the parameters of its Phase III study had been altered to expand the pool for progression-free survival analysis. The stock responded with a 6.21% decline, dropping $45.41 per share.

The situation intensified on May 15, 2026, when the company confirmed that the trial failed to reach statistical significance for its primary endpoint. This disclosure triggered a further 9.82% slide in share price, closing at $629.68 on May 16. Investors who acquired securities during the relevant period are directed to contact Danielle Peyton at Pomerantz LLP to participate in the proceedings.