REGN Shareholder Alert: Regeneron Pharmaceuticals, Inc. Securities Class Action Lawsuit - Investors With Losses May Contact Levi & Korsinsky

This promise-vs-reality notice focuses on allegations that Regeneron promoted Phase I Fianlimab-Libtayo results and practice-changing expectations while the Phase III study allegedly faced heightened statistical and clinical failure risk.

NEW YORK--(BUSINESS WIRE)--Levi & Korsinsky, LLP alerts investors in Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) that a securities class action has been filed on behalf of shareholders who purchased securities between August 1, 2025 and May 15, 2026. Find out if you might be eligible to recover losses. You may also contact Joseph E. Levi, Esq. at [e-mail] or [phone].

REGN traded as high as $731.77 on April 28, 2026 and closed at $629.68 after the Company announced that the Phase III Fianlimab-Libtayo Study did not reach statistical significance for its primary progression-free survival endpoint, a decline of $102.09 per share, or 13.95%. The lead plaintiff deadline is September 14, 2026.

The Alleged Promise: Phase I Data Set Investor Expectations

The lawsuit asserts that Regeneron and certain executives pointed investors to earlier Fianlimab-Libtayo data showing a 57% objective response rate and a pooled median progression-free survival of 24 months. Management allegedly framed those results as supporting a potential differentiated first-line melanoma therapy if Phase III performance could approach that earlier profile.

The action claims that investors were also told that median PFS in the low-to-mid teens could be practice changing, particularly when compared with pembrolizumab historical median PFS of approximately 4 to 5 months.

The Alleged Reality: Phase III Results Did Not Match the Narrative

As alleged, the Phase III study’s prolonged slowdown in PFS event accrual did not support the optimistic interpretation presented to investors. The complaint contends that preliminary statistical assumptions were flawed, the active treatment arm was failing to achieve meaningful clinical differentiation over standard therapies, and the study ultimately did not reach statistical significance.

"Companies that make specific promises to investors about future performance have an obligation to disclose known risks to those projections, especially when the alleged gap involves a clinical trial endpoint central to investor valuation," said Joseph E. Levi, Esq., managing partner of Levi & Korsinsky, LLP.

Promise vs. Actual: By the Numbers

• Phase I pooled cohorts allegedly showed a 57% objective response rate.
• Phase I pooled median PFS was cited as approximately 24 months.
• Management allegedly suggested low-to-mid-teens median PFS could be practice changing.
• The complaint alleges the trial later required expanded patient criteria for PFS analysis.
• On May 15, 2026, Regeneron announced the Phase III trial did not reach statistical significance for improvement in PFS.
• REGN allegedly lost $102.09 per share from the Class Period high to the post-disclosure close.

What the Lawsuit Alleges About the Gap

Plaintiffs contend that the contrast between earlier expectations and the failed primary endpoint supports allegations that investors purchased REGN shares at artificially inflated prices. The case is pending in the United States District Court for the Southern District of New York and asserts claims under Sections 10(b) and 20(a) of the Exchange Act and Rule 10b-5.

Click here to submit your information and learn more about the case or call [phone].

Levi & Korsinsky, LLP — Top 50 securities litigation firm (ISS, seven consecutive years). Over 70 professionals. Hundreds of millions recovered.

Frequently Asked Questions About the REGN Lawsuit

Q: What is the REGN class action lawsuit about? A: A securities class action has been filed against Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) alleging materially false and misleading statements between August 1, 2025 and May 15, 2026. Shares fell approximately 13.95% from the Class Period high after the Company disclosed that the Phase III Fianlimab-Libtayo Study did not reach statistical significance for its primary PFS endpoint. Investors who purchased shares during the Class Period and suffered losses may be eligible to seek compensation.

Q: Who is eligible to join the REGN investor lawsuit? A: Investors who purchased REGN stock or securities between August 1, 2025 and May 15, 2026 and suffered financial losses may be eligible. Eligibility is based on purchase date and documented losses, not on whether you still hold the shares.

Q: What court was the REGN class action filed in? A: The case was filed in the United States District Court for the Southern District of New York, governed by the Private Securities Litigation Reform Act of 1995.

Q: What is a lead plaintiff and why does it matter? A: A lead plaintiff is the investor appointed by the court to represent the entire class. Lead plaintiffs are typically investors with the largest documented losses. Being appointed does not increase individual recovery but gives direct oversight of how the case is run.

Q: What happens after I contact Levi & Korsinsky? A: An attorney will review your trading history at no cost and provide an initial assessment of your potential eligibility.

Q: What if I already sold my REGN shares, can I still recover losses? A: Yes. Eligibility is based on when you purchased, not whether you still hold the shares. Investors who bought during the Class Period and sold at a loss may still be eligible to participate.

Q: What does it cost me to participate? A: There is no upfront cost to contact the firm. Securities class actions are generally handled on a pure contingency basis. No upfront fees, no retainer, and no out-of-pocket costs. Any attorneys' fees and expenses awarded to class counsel are subject to court approval.

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