--- title: "REGN Breaking News: Regeneron Inc. Sued for Securities Fraud after Revealing Failed Phase III Clinical Trial Resulting in 10% Stock Drop – Investors Notified to Contact BFA Law" type: "News" locale: "en" url: "https://longbridge.com/en/news/293381845.md" description: "A securities fraud class action lawsuit has been filed against Regeneron Pharmaceuticals and its executives by Bleichmar Fonti & Auld LLP. The suit alleges the company misled investors regarding the success of its Phase III Fianlimab-Libtayo clinical trial for advanced melanoma, which ultimately failed to achieve statistical significance. This disclosure caused Regeneron's stock to drop 6.2% in late April and nearly 10% in mid-May 2026. Investors are urged to contact the firm by September 14, 2026, to potentially serve as lead plaintiff." datetime: "2026-07-21T20:14:10.000Z" locales: - [zh-CN](https://longbridge.com/zh-CN/news/293381845.md) - [en](https://longbridge.com/en/news/293381845.md) - [zh-HK](https://longbridge.com/zh-HK/news/293381845.md) --- # REGN Breaking News: Regeneron Inc. Sued for Securities Fraud after Revealing Failed Phase III Clinical Trial Resulting in 10% Stock Drop – Investors Notified to Contact BFA Law REGN Breaking News: Regeneron Inc. Sued for Securities Fraud after Revealing Failed Phase III Clinical Trial Resulting in 10% Stock Drop – Investors Notified to Contact BFA Law A securities fraud class action lawsuit has been filed on behalf of Regeneron investors after its stock plummeted almost 10% because Regeneron allegedly misled investors regarding the success of its Phase III Fianlimab-Libtayo clinical trial. Leading securities law firm **Bleichmar Fonti & Auld LLP** announces that a class action lawsuit has been filed against Regeneron Pharmaceuticals, Inc. (NASDAQ:REGN) and certain of the company’s senior executives for securities fraud after significant stock drops resulting from potential violations of the federal securities laws. If you invested in Regeneron, you are encouraged to obtain additional information by visiting: **https://www.bfalaw.com/cases/regeneron-class-action-lawsuit**. **Key Details of the Regeneron ($REGN) Class Action:** - **Lead Plaintiff Deadline:** September 14, 2026 - **Alleged Misconduct:** Securities fraud alleging that Regeneron misled investors regarding the success of its Phase III Fianlimab-Libtayo clinical trial - **Stock Drop:** - April 29, 2026 – 6.2% Stock Drop - May 15, 2026 – 9.8% Stock Drop - **Court:** U.S. District Court for the Southern District of New York - **Action:** Contact BFA Law to discuss your rights Investors have until September 14, 2026, to ask the Court to be appointed to lead the case. The complaint asserts securities fraud claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 on behalf of investors in Regeneron securities. 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. **Why is Regeneron Being Sued for Securities Fraud?** 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. **Click here for more information:** **https://www.bfalaw.com/cases/regeneron-class-action-lawsuit****.** **What Can You Do?** If you invested in Regeneron, you may have legal options and are encouraged to submit your information to the firm. 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 litigation. The firm will seek court approval for any potential fees and expenses. **Submit your information by visiting:** **https://www.bfalaw.com/cases/regeneron-class-action-lawsuit** Or contact: Adam McCall adam@bfalaw.com 212.789.3619 **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_, and its 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.” Among its recent notable successes, BFA recovered over $900 million in value from Tesla, Inc.’s Board of Directors, as well as $420 million from Teva Pharmaceutical Ind. Ltd. For more information about BFA and its attorneys, please visit https://www.bfalaw.com. **https://www.bfalaw.com/cases/regeneron-class-action-lawsuit** _Attorney advertising. Past results do not guarantee future outcomes._ Adam McCall adam@bfalaw.com 212.789.3619 View source version on businesswire.com: https://www.businesswire.com/news/home/20260721415402/en/ ### Related Stocks - [REGN.US](https://longbridge.com/en/quote/REGN.US.md) ## Related News & Research - [Regeneron Pharmaceuticals, Inc. (REGN) Faces Securities Class Action Amid Disclosures About Key Trial's Protocol and Ultimate Failure - HBSS](https://longbridge.com/en/news/294080297.md) - [Regeneron Pharmaceuticals, Inc. 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