Regeneron Lawsuit Summary
The Regeneron class action lawsuit asserts securities fraud claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 on behalf of investors in Regeneron common stock. The class action is pending in the U.S. District Court for the Southern District of New York. It is captioned Cheathem v. Regeneron Pharm., Inc., et al., No. 26-cv-6026.
If you lost money on your Regeneron investment, you are encouraged to submit your information using the form on this page. You may also email adam@bfalaw.com or call 212.789.3619.
Why is Regeneron Being Sued for Securities Fraud?
Regeneron has been sued for securities fraud following significant stock drops resulting from potential violations of the federal securities laws. The decline in Regeneron’s stock price caused significant losses to investors.
Regeneron is a pharmaceutical company that discovers, invents, develops, manufactures, tests, and commercializes medicines to treat various disorders.
During the relevant period, Regeneron was investigating Fianlimab, a human monoclonal antibody targeting the LAG-3 immune checkpoint receptor on T-cells. Specifically, Regeneron was testing Fianlimab in combination with Libtayo in a Phase III study to determine whether the drug combination could serve as a first-line treatment for advanced melanoma.
Regeneron told investors that it had “a lot of hope and confidence” that the Phase III trial “can generate a meaningful differentiation against current standards of care.” Further, despite acknowledging that study results had slowed, Regeneron told investors that this was likely because “there was a high level of response and those response[s] are very durable” and that the combination drug was a “potential blockbuster.”
In truth, as alleged, the Phase III Fianlimab-Libtayo study did not achieve statistically significant results.
Why did Regeneron’s Stock Drop?
On April 29, 2026, before market hours, Regeneron announced the Phase III Fianlimab-Libtayo study “will now consider all patients enrolled in the study with a minimum follow-up of 6 months.” This expansion of the study parameters indicated the study did not have enough positive results to achieve statistical significance.
This news caused the price of Regeneron stock to decline $45.41 per share, or 6.2%, from a closing price of $731.77 per share on April 28, 2026, to $686.36 per share on April 29, 2026.
Then, on May 15, 2026, after market hours, Regeneron published a press release stating that the Phase III Fianlimab-Libtayo “did not reach statistical significance for the primary endpoint” tested.
This news caused the price of Regeneron stock to decline $68.57 per share, or 9.8%, from a closing price of $698.25 per share on May 15, 2026, to $629.68 per share on May 18, 2026.
Regeneron (REGN) Stock Chart
Image Caption: NASDAQ online chart showing the Regeneron (REGN) stock drop following the April and May 2026 announcements.
What is the Regeneron Leadership Deadline?
You may ask the Court no later than September 14, 2026, to appoint you as Lead Plaintiff through counsel of your choice.
To be a member of the Class, you need not take any action at this time. The ability to share in any potential future recovery is not dependent on serving as Lead Plaintiff.
How Do I Submit My Information?
If you lost money when Regeneron securities dropped in price, you are encouraged to submit your information using the form on this page to speak with an attorney about your rights.
You can also contact:
Adam McCall
amccall@bfalaw.com
212.789.3619
All representation is on a contingency fee basis; there is no cost to you. Shareholders are not responsible for any court costs or expenses of any class action lawsuit. The firm will seek court approval for any potential fees and expenses.
Why Bleichmar Fonti & Auld LLP?
BFA is a leading international law firm representing plaintiffs in securities class actions and shareholder litigation. It has been named a top plaintiff law firm by Chambers USA, The Legal 500, and ISS SCAS.
BFA attorneys have been named “Elite Trial Lawyers” by the National Law Journal, “Litigation Stars” by Benchmark Litigation, among the top “500 Leading Plaintiff Financial Lawyers” by Lawdragon, “Titans of the Plaintiffs’ Bar” by Law360, and “SuperLawyers” by Thomson Reuters.
Most recently, The Legal 500 awarded BFA the most client satisfaction accolades of any plaintiff’s securities litigation law firm, with clients noting: “[t]here is no better service provider in the practice area,” “[t]he interest of the client is always front and center,” and “[t]here isn’t a better firm in this space.” One testimonial described the firm as “nimble and entrepreneurial,” with a “relentless focus on adding value for clients.”
BFA’s notable successes include a recovery of over $900 million in value from Tesla, Inc.'s Board of Directors, as well as $420 million from Teva Pharmaceutical Ind. Ltd.
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