Market impact notice: REGN shares allegedly lost $102.09 from the Class Period high after disclosures about a Phase III Fianlimab-Libtayo protocol change and failed primary endpoint challenged earlier positive trial-risk messaging.
NEW YORK, Aug. 19, 2026 /PRNewswire/ -- Levi & Korsinsky, LLP notifies investors in Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) that a class action has been filed on behalf of shareholders who purchased securities between August 1, 2025 and May 15, 2026. Find out if you may qualify to recover losses. You may also contact Joseph E. Levi, Esq. at jlevi@levikorsinsky.com or (212) 363-7500.
REGN declined from $731.77 on April 28, 2026 to $629.68 after the May 15, 2026 after-market disclosure was reflected in trading, a $102.09 per-share drop, or approximately 13.95%. Investors seeking appointment as lead plaintiff must move the Court by September 14, 2026.
Market Impact From the Alleged Fianlimab-Libtayo Disclosure Shift
The securities action alleges that Regeneron and certain executives gave investors an overly positive view of the Phase III Fianlimab-Libtayo Study while minimizing the risk that slowing progression-free survival event accrual signaled statistical and clinical trial problems. The complaint contends that the market began repricing REGN shares after Regeneron disclosed on April 29, 2026 that the trial protocol had been altered to expand the patient population eligible for PFS analysis.
A second market reaction followed Regeneron's May 15, 2026 announcement that the Phase 3 trial did not reach statistical significance for the primary endpoint of improvement in PFS. The lawsuit asserts that these disclosures corrected earlier alleged misstatements and caused investors who purchased during the Class Period to suffer damages.
REGN Stock Movement and Trial-Readout Impact
- REGN closed at $731.77 on April 28, 2026 before the protocol-change disclosure.
- Shares fell to $686.36 on April 29, 2026, a one-day decline of about 6.2%.
- Regeneron later announced after market close on May 15, 2026 that the Fianlimab Phase 3 trial did not reach statistical significance on PFS.
- On May 18, 2026, the first trading day after that announcement, REGN closed at $629.68.
- The total decline from the April 28 price to the May 18 close was $102.09 per share.
Why the Market Reaction Matters for REGN Investors
The filing states that investors allegedly were not given adequate information about the risk that the prolonged event-accrual slowdown reflected flawed statistical assumptions and insufficient clinical differentiation from standard therapies. Analysts cited in the complaint reportedly connected the April 29 protocol amendment to concerns that the underlying PFS benefit may have been insufficient to show statistical significance.
"Market reactions of this magnitude can be significant evidence of investor harm when a complaint alleges that earlier statements failed to disclose material clinical-trial risks. Here, the alleged disconnect between optimistic trial-related statements and the Phase III study's subsequent failure to meet its primary PFS endpoint is central to the market-impact theory."Â -- Joseph E. Levi, Esq.
Submit your information here or call (212) 363-7500.
Levi & Korsinsky, LLPÂ is a nationally recognized shareholder rights firm. Over the past 20 years, the firm has secured hundreds of millions of dollars for aggrieved shareholders. Ranked in ISS Top 50 for seven consecutive years.
Frequently Asked Questions About the REGN Lawsuit
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 and is governed by the Private Securities Litigation Reform Act of 1995.
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% after the Company disclosed a Phase III Fianlimab-Libtayo protocol change and later announced that the trial did not reach statistical significance for improvement in progression-free survival. Investors who purchased shares during the Class Period and suffered losses may be eligible to seek compensation.
Q: How much did REGN stock drop? A: Shares declined approximately 13.95%, or $102.09 per share, from the April 28, 2026 closing price of $731.77 to the May 18, 2026 closing price of $629.68 following the alleged corrective disclosures. Investors who purchased shares during the Class Period at allegedly artificially inflated prices and suffered losses may be eligible to seek compensation.
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 documents do I need to submit my information? A: Brokerage statements or trade confirmations showing purchase dates, share quantities, prices paid, and any subsequent sale dates and prices.
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: Do I need to go to court or give testimony? A: No. The overwhelming majority of class members never appear in court or give depositions. If there is a settlement or recovery, eligible class members generally submit a claim form to seek their portion.
Q: What if I live outside the United States? A: U.S. securities class actions generally cover purchases on U.S. exchanges regardless of the investor's country of residence.
CONTACT:\
Levi & Korsinsky, LLP\
Joseph E. Levi, Esq.\
Ed Korsinsky, Esq.\
33 Whitehall Street, 27th Floor\
New York, NY 10004\
Tel: (212) 363-7500\
Fax: (212) 363-7171
Attorney Advertising. Prior results do not guarantee similar outcomes.
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SOURCE Levi & Korsinsky, LLP
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