This timeline-focused notice highlights allegations that Regeneron's Phase III Fianlimab-Libtayo disclosures evolved from delayed event accrual to a protocol amendment and then a failed primary endpoint, with REGN investors allegedly absorbing substantial share-price losses.
NEW YORK, Aug. 13, 2026 /PRNewswire/ -- SueWallSt 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. See if you could be eligible to recover. You may also contact Joseph E. Levi, Esq. at jlevi@SueWallSt.com or (888) SueWallSt.
REGN declined from $731.77 on April 28, 2026 to $629.68 on May 18, 2026, a decline of $102.09 per share, or approximately 13.95%. Investors have until September 14, 2026 to seek lead plaintiff status.
Chronology of Alleged Trial Disclosure Events
The filing states that Regeneron repeatedly framed a slowdown in progression-free survival event accrual as potentially consistent with favorable active-treatment performance. As set forth in the complaint, shareholders later learned that the Phase III Fianlimab-Libtayo Study required an expanded patient population for PFS analysis and then failed to reach statistical significance on its primary endpoint.
Timeline of Alleged Disclosure Failures
- August 1, 2025: Regeneron stated that enrollment for the PFS cohort had completed, but results were delayed because blinded PFS event accrual had slowed.
- November 17, 2025: Company representatives allegedly continued to associate the slower event rate with possible strength in the test arms.
- March 2026: The complaint alleges that public statements continued to suggest confidence in statistical powering and the possibility of durable treatment effect.
- April 29, 2026: Regeneron disclosed that the PFS analysis would include all patients enrolled with at least six months of follow-up, and REGN fell $45.41 per share.
- May 15, 2026: Regeneron announced after market close that the Phase 3 trial did not reach statistical significance for improvement in PFS, followed by a $68.57 per-share decline on May 18, 2026.
Why the Sequence Matters to REGN Shareholders
It is alleged that the timeline reflects a growing disparity between Regeneron's investor-facing statements regarding the Phase III Fianlimab-Libtayo Study and the statistical risks allegedly emerging during the study. The complaint contends that the April protocol change and May trial result corrected earlier alleged impressions about the strength and reliability of the study's path to readout.
Timely disclosure of material clinical trial developments is fundamental to fair and efficient markets, particularly where investors are tracking a pivotal study with delayed event accrual. The complaint alleges that Regeneron's chronology matters because each update affected how shareholders assessed trial risk. -- Joseph E. Levi, Esq.
Calculate your potential recovery or call (888) SueWallSt.
WHY SUEWALLST: SueWallSt is powered by Levi & Korsinsky LLP. Levi & Korsinsky LLP has established itself as a nationally-recognized securities litigation firm that has secured hundreds of millions of dollars for aggrieved shareholders and built a track record of winning high-stakes cases. The firm has extensive expertise representing investors in complex securities litigation and a team of over 70 employees to serve our clients. For seven years in a row, Levi & Korsinsky has ranked in ISS Securities Class Action Services' Top 50 Report as one of the top securities litigation firms in the United States.
Frequently Asked Questions About the REGN Lawsuit
Q: How much did REGN stock drop? A: Shares declined from $731.77 on April 28, 2026 to $629.68 on May 18, 2026, a decline of $102.09 per share, or approximately 13.95%, after disclosures concerning the Phase III Fianlimab-Libtayo Study.
Q: What specific misstatements does the REGN lawsuit allege? A: The complaint alleges Regeneron made materially false or misleading statements regarding the risk of clinical failure in the Phase III Fianlimab-Libtayo Study, including statements that allegedly minimized risks tied to slowed event accrual and statistical validity.
Q: When did Regeneron allegedly mislead investors? A: The Class Period runs from August 1, 2025 to May 15, 2026. The complaint alleges that corrective disclosures concerning the trial protocol and failure to meet the primary endpoint caused significant stock declines.
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 asserts claims under the federal securities laws.
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 class. Lead plaintiffs are typically investors with substantial documented losses and may help oversee the litigation on behalf of the class.
Q: What documents should REGN investors keep? A: Investors should keep 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: What does it cost me to participate? A: There is no upfront cost for an evaluation. Securities class actions are generally handled on a contingency basis, with any attorneys' fees and expenses subject to court approval.
CONTACT:
Levi & Korsinsky, LLP
Joseph E. Levi, Esq.
33 Whitehall Street, 27th Floor
New York, NY 10004
Tel: (888)Â SueWallSt
Fax: (212) 363-7171
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SOURCE SueWallSt.com
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