Time-Sensitive: Allegations focus on Regeneron's statements about clinical differentiation in the Phase III Fianlimab-Libtayo Study and the last-minute protocol amendment used to force a trial readout.
NEW YORK, July 29, 2026 /PRNewswire/ -- Levi & Korsinsky, LLP alerts investors in Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) of a pending securities class action. Class Period: August 1, 2025 through May 15, 2026. Check if you might be eligible to recover your investment losses. You may also contact Joseph E. Levi, Esq. at jlevi@levikorsinsky.com or (212) 363-7500.
REGN shares declined from $731.77 on April 28, 2026 to $629.68 after the May 15, 2026 after-market disclosure, a $102.09 per-share decrease, or approximately 13.95%. The Court has set September 14, 2026 as the deadline to apply for lead plaintiff appointment.
"Investors deserve transparency about material risks that could affect their investments, especially where a pivotal oncology trial is approaching a readout after a protocol change. The allegations here focus on whether shareholders received sufficient information regarding clinical differentiation risk before REGN shares declined." -- Joseph E. Levi, Esq.
Alleged Melanoma Trial Clinical Differentiation Representations
The lawsuit asserts that Regeneron and management presented the prolonged event accrual slowdown as consistent with favorable active-arm performance in the Phase III Fianlimab-Libtayo Study. As alleged, those statements allegedly minimized the risk that the active treatment arm was not separating meaningfully from standard therapies.
The action claims that investors were not adequately informed that the study's ability to reach statistical significance was under pressure and that a last-minute protocol amendment would expand the patient pool for progression-free survival analysis.
Clinical Differentiation Biotechnology Securities Issues
- Management allegedly suggested that delayed event accrual could reflect durable responses in the active treatment arms.
- The complaint alleges the active treatment arm failed to achieve meaningful clinical differentiation over standard therapies.
- Regeneron later disclosed that the PFS analysis would consider all enrolled patients with at least six months of follow-up.
- The May 15, 2026 announcement stated that the Phase 3 Trial of Fianlimab did not reach statistical significance for improvement in PFS.
- Plaintiffs contend the protocol amendment and failed primary endpoint undermined prior positive representations about the study's risk profile.
Why Differentiation Adequacy Allegedly Mattered to Investors
Fianlimab-Libtayo was positioned as a potentially important first-line advanced melanoma program. As alleged, investors relied on Regeneron's representations concerning the potential for the Fianlimab-Libtayo combination to demonstrate clinically meaningful improvement over pembrolizumab and other standards of care.
The action claims the market reacted sharply when information concerning the Phase III study's protocol changes and subsequent failure to meet the primary PFS endpoint.
Learn more about the case or call (212) 363-7500.
WHY LEVI & KORSINSKY — Ranked in ISS Securities Class Action Services' Top 50 Report for seven consecutive years, Levi & Korsinsky, LLP is a nationally recognized leader in shareholder rights litigation. With a team of over 70 professionals, the firm has recovered hundreds of millions of dollars for investors. Investors who suffered losses have until September 14, 2026 to seek appointment as lead plaintiff.
Frequently Asked Questions About the REGN Lawsuit
Q: What specific misstatements does the REGN lawsuit allege? A: The complaint alleges Regeneron Pharmaceuticals, Inc. made materially false or misleading statements regarding the Phase III Fianlimab-Libtayo Study, including statements that allegedly suggested slowing event accrual reflected active-arm performance while omitting clinical differentiation risks and the need for a protocol amendment.
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 on April 29, 2026 and May 15, 2026 revealed information that 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 is 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: 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 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.
CONTACT:\
Levi & Korsinsky, LLP\
Joseph E. Levi, Esq.\
Ed Korsinsky, Esq.\
33 Whitehall Street, 27th Floor\
New York, NY 10004\
jlevi@levikorsinsky.com\
Tel: (212) 363-7500\
Fax: (212) 363-7171
Attorney Advertising. Prior results do not guarantee similar outcomes.
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