Legal Matters	6 Months Ended
Jun. 30, 2025
Commitments and Contingencies Disclosure [Abstract]
Legal Matters	Legal Matters From time to time, the Company is a party to legal proceedings in the course of the Company's business. The outcome of any such proceedings, regardless of the merits, is inherently uncertain. If the Company is unable to prevail in one or more of such proceedings, its consolidated financial position, results of operations, and future cash flows may be materially adversely impacted. Costs associated with the Company's involvement in legal proceedings are expensed as incurred. The Company recognizes gain contingencies associated with such proceedings when the award or recovery is realized or realizable and loss contingencies when it is probable that a liability will be incurred and the amount of loss can be reasonably estimated. As of June 30, 2025 and December 31, 2024, the Company's accruals for loss contingencies were not material. There are certain loss contingencies that the Company deems reasonably possible for which the possible loss or range of possible loss is not estimable at this time. Proceedings Relating to EYLEA (aflibercept) Injection Certain of the Company's patents pertaining to EYLEA are subject to post-grant proceedings before the United States Patent and Trademark Office ("USPTO"), the European Patent Office (the "EPO"), or other comparable foreign authorities, including those described in greater detail below. In addition, the Company has filed patent infringement lawsuits in several jurisdictions alleging infringement of certain Company patents pertaining to EYLEA, including those described in greater detail below. United States U.S. Patent Litigation On August 2, 2022, the Company filed a patent infringement lawsuit against Mylan Pharmaceuticals Inc. ("Mylan"), a wholly-owned subsidiary of Viatris Inc., in the United States District Court for the Northern District of West Virginia alleging that Mylan's filing for U.S. Food and Drug Administration ("FDA") approval of an aflibercept 2 mg biosimilar infringes certain Company patents. On June 5, 2023, Biocon Biologics Inc. ("Biocon"), as successor-in-interest to the aflibercept 2 mg biosimilar, was joined as a defendant to the lawsuit. A trial was held in June 2023 concerning certain claims of the '601 Patent, the '572 Patent, and the Company's U.S. Patent No. 11,084,865 (the "'865 Patent"). On December 27, 2023, the court issued a decision finding that (i) the asserted claims of the '865 Patent were valid and infringed by Mylan and Biocon and (ii) the asserted claims of the '601 and '572 Patents were infringed by Mylan and Biocon but were invalid as obvious. On June 11, 2024, the court granted the Company's motion for a permanent injunction, enjoining Mylan and Biocon from selling in the United States their aflibercept 2 mg biosimilar until the expiration of the '865 Patent. On June 21, 2024, Mylan and Biocon filed a notice of appeal of the court's December 27, 2023 and June 11, 2024 decisions to the Federal Circuit. An oral hearing concerning Mylan and Biocon's appeal was held on February 7, 2025. On April 14, 2025, the parties entered into a settlement agreement, pursuant to which Mylan and Biocon's appeal to the Federal Circuit and all related litigation have been dismissed and Biocon is precluded from launching its aflibercept 2 mg biosimilar until the second half of 2026. On November 8, November 22, and November 29, 2023, respectively, the Company filed patent infringement lawsuits against Celltrion, Inc. ("Celltrion"), Samsung Bioepis Co., Ltd. ("Samsung Bioepis"), and Formycon AG ("Formycon") in the United States District Court for the Northern District of West Virginia following service on Regeneron of each company's notice of commercial marketing. The lawsuits alleged that each company had infringed certain Company patents, including based on each company's filing for FDA approval of an aflibercept 2 mg biosimilar. On December 27, 2023, the Company filed a second patent infringement lawsuit against Samsung Bioepis. On June 14, June 21, and June 28, 2024, respectively, the court granted the Company's motions for preliminary injunctions against Samsung Bioepis, Formycon, and Celltrion; each of these decisions was appealed to the Federal Circuit. On January 29, 2025, the Federal Circuit affirmed the lower court's preliminary injunction decisions against Samsung Bioepis and Formycon; and on March 5, 2025, the Federal Circuit affirmed the lower court's preliminary injunction decision against Celltrion. On May 23, 2025, Formycon petitioned the lower court to revoke the preliminary injunction. On January 10, 2024, the Company filed a patent infringement lawsuit against Amgen Inc. ("Amgen") in the United States District Court for the Central District of California alleging that Amgen's filing for FDA approval of an aflibercept 2 mg biosimilar infringed certain Company patents. On April 11, 2024, the United States Judicial Panel on Multidistrict Litigation granted the Company's motion to transfer this lawsuit to the United States District Court for the Northern District of West Virginia for coordinated and consolidated pretrial proceedings with the lawsuits described in the preceding paragraph. On September 23, 2024, the court denied the Company's motion for a preliminary injunction; and on September 25, 2024, the Federal Circuit issued an administrative stay pending its review of the Company's temporary injunction motion. On October 22, 2024, the Federal Circuit denied the Company's temporary injunction motion and lifted the administrative stay. On March 14, 2025, the Federal Circuit affirmed the lower court's preliminary injunction decision. On June 17, 2025, the Company filed an additional patent infringement lawsuit against Amgen in the United States District Court for the Central District of California alleging that Amgen's continued commercialization of its aflibercept 2 mg biosimilar infringes the Company's U.S. Patent No. 12,331,099. On August 26, 2024, the Company filed a patent infringement lawsuit against Sandoz Inc. ("Sandoz") in the United States District Court for the District of New Jersey alleging that Sandoz's filing for FDA approval of an aflibercept 2 mg biosimilar infringed certain Company patents. On September 12, 2024, the United States Judicial Panel on Multidistrict Litigation granted the Company's motion to transfer this lawsuit to the United States District Court for the Northern District of West Virginia for coordinated and consolidated pretrial proceedings with the lawsuits described in the preceding paragraphs. On July 11, 2025, the Company filed a motion for a preliminary injunction against Sandoz based on the '865 Patent. Post-Grant Proceedings Before the USPTO On November 20, 2024, November 29, 2024, and January 15, 2025, Samsung Bioepis, Formycon, and Celltrion, respectively, filed inter partes review ("IPR") petitions in the USPTO against the '865 Patent, each seeking a declaration that the '865 Patent is invalid. On June 6, 2025, the USPTO denied institution of Samsung and Formycon's respective IPR petitions, and on June 25, 2025, the USPTO denied institution of Celltrion's IPR petition. On July 14, 2025, Fresenius Kabi SwissBioSim GmbH filed IPR petitions in the USPTO against the '865 Patent and U.S. Patent No. 10,828,345 (the "'345 Patent"), seeking a declaration that the '865 Patent and '345 Patent are invalid. Europe EPO Post-Grant Proceedings Various parties, including Amgen and other, anonymous parties, are seeking revocation of the Company's European Patent Nos. 2,944,306 (the "'306 Patent"), 3,716,992 (the "'992 Patent"), and 3,384,049 (the "'049 Patent") before the Opposition Division ("OD") of the EPO. On November 26, 2024, following an oral hearing, the OD announced its decision to revoke the '306 Patent. On March 11, 2025, the Company appealed the OD's decision. Oral hearings concerning the '992 and '049 Patents have been scheduled for October and December 2025, respectively. Country-Specific Proceedings Various parties, including Samsung Bioepis and Formycon and/or their affiliated entities, are seeking revocation of the '306 Patent, the '992 Patent, and the Company's European Patent No. 2,364,691 (the "'691 Patent") and/or a declaration that its aflibercept 2 mg biosimilar would not infringe these patents in several European national courts (including those in Belgium, France, Germany, Italy, the Netherlands, and the United Kingdom). In the United Kingdom, the Company has filed a preemptive counterclaim against Formycon, Klinge Biopharma GmbH, and Samsung Bioepis UK Limited for infringement of the '306 Patent and the '691 Patent. In April 2025, the Company and Amgen entered into a settlement agreement, pursuant to which Amgen is no longer party to the United Kingdom proceedings. In Germany, following a trial held in June 2025, the German Federal Patent Court upheld the '691 Patent as valid and dismissed the revocation proceeding brought by Samsung Bioepis. In the United Kingdom, trials concerning the '691 and '306 Patents were held in June 2025, and the '992 Patent proceedings are stayed pending resolution of the EPO proceedings concerning this patent. In the Netherlands, a trial concerning the '691 and '306 Patents was held on July 18, 2025. The Company has commenced proceedings in Belgium against various parties, including Amgen, Celltrion, Sterigenics (Petit-Rechain) NV, and Sandoz GmbH, for infringement of the Company's European Patent No. 1,183,353 (as extended by Supplementary Protection Certificate 2013C/029). Canada Proceedings against Amgen Canada On May 9, 2023, Amgen Canada Inc. ("Amgen Canada") filed invalidation proceedings against the Company in the Federal Court of Canada seeking revocation of the Company's Canadian Patent Nos. 2,654,510 (the "'510 Patent") and 3,007,276 (the "'276 Patent"). On September 14, 2023, the Company, Bayer Inc., and Bayer Healthcare LLC filed patent infringement lawsuits against Amgen Canada in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of Bayer Healthcare LLC's Canadian Patent No. 2,970,315 (the "'315 Patent"). On September 14, 2023, the Company and Bayer Inc. filed three separate patent infringement lawsuits against Amgen Canada in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the Company's Canadian Patent Nos. 3,129,193 (the "'193 Patent"), 2,965,495 (the "'495 Patent"), and 2,906,768 (the "'768 Patent"), respectively. On October 11, 2023, the Company, Bayer Inc., and Bayer Healthcare LLC filed two separate patent infringement lawsuits against Amgen Canada in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the Company's '510 Patent and '276 Patent, respectively. On June 28, 2024, Amgen Canada filed a motion to delist the '276 Patent from the Canada Patent Register; and on November 20, 2024, the court granted Amgen Canada's motion. That decision has been appealed by the Company and Bayer. A trial concerning the '510 Patent and the '276 Patent was held in May–June 2025; and a trial concerning the '315 Patent and the '193 Patent has been scheduled for August–September 2025. Proceedings against Sandoz On January 24, 2025, the Company, Bayer Inc., and Bayer Healthcare LLC filed patent infringement lawsuits against Sandoz Canada Inc. in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the '510 Patent, the '276 Patent, the '495 Patent, the '768 Patent, the '193 Patent, the '315 Patent, and Canadian Patent No. 3,137,326 (the "'326 Patent"). A trial concerning the '510 Patent, the '276 Patent, the '315 Patent, and the '326 Patent has been scheduled for October–November 2026. South Korea On December 13, 2022, Samsung Bioepis initiated invalidation proceedings before the Intellectual Property Trial and Appeal Board of the Korean Intellectual Property Office ("KIPO") against the Company's Korean Patent No. 1406811 (the "'811 Patent"), seeking revocation of the '811 Patent in its entirety. On October 23, 2024, the KIPO maintained the '811 Patent as valid; Samsung Bioepis has appealed that decision. The Company and, as applicable, Bayer Consumer Care AG, have also filed patent infringement lawsuits in the Seoul Central District Court against various parties including Samsung Bioepis and its parent company Samsung Biologics Co., Ltd. (collectively, "Samsung"), Sam Chun Dang Pharm. Co., Ltd. and OPTUS Pharmaceutical Co., Ltd., and Celltrion. These lawsuits seek damages and/or injunctive relief and allege that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar by the relevant defendant(s) would infringe one or more claims of the '811 Patent and/or the Company's Korean Patent Nos. 659477 (the "'477 Patent") and 2519234 (the "'234 Patent"). On February 7, 2025, the Seoul Central District Court granted the Company's preliminary injunction request against Samsung on the basis of the '811 Patent; Samsung has appealed that decision. The preliminary injunction against Samsung prohibits Samsung from manufacturing and selling its aflibercept 2 mg biosimilar in South Korea. Also on February 7, 2025, the Seoul Central District Court denied Regeneron's preliminary injunction request against Celltrion; Regeneron has appealed that decision. Australia On June 4, 2025, the Company, Bayer Consumer Care AG, and Bayer Australia filed a patent infringement lawsuit against Sandoz Pty Ltd. and a request for a preliminary injunction in the Federal Court of Australia alleging that the importing, selling, supplying, or otherwise disposing of an aflibercept 2 mg biosimilar would infringe one or more claims of the Company's Australian Patent No. 2012205599. An oral hearing to consider the preliminary injunction request has been scheduled for August 14, 2025. Proceedings Relating to EYLEA (aflibercept) Injection Pre-filled Syringe On July 17, 2020, the Company filed an antitrust lawsuit (as amended on January 25, 2021) against Novartis Pharma AG, Novartis Pharmaceuticals Corporation, and Novartis Technology LLC (collectively, "Novartis") and Vetter Pharma International Gmbh in the United States District Court for the Southern District of New York seeking a judgment that the defendants' conduct relating to Novartis's attempt to assert its U.S. Patent No. 9,220,631 against Regeneron in 2020 violated Sections 1 and 2 of the Sherman Antitrust Act of 1890, as amended (the "Sherman Antitrust Act"), and constituted tortious interference with contract. The Company is also seeking injunctive relief and treble damages. On September 21, 2021, this lawsuit was transferred to the Northern District of New York. On June 10, 2022, the Company filed an appeal of the District Court's decision to dismiss the amended complaint with the U.S. Court of Appeals for the Second Circuit (the "Second Circuit"). On March 18, 2024, the Second Circuit reversed the District Court's decision to dismiss the amended complaint and remanded the lawsuit to the District Court for further proceedings consistent with the Second Circuit's opinion. On November 19, 2024, the Company moved to transfer the lawsuit back to the Southern District of New York, which motion was granted on December 5, 2024. Proceedings Relating to Praluent (alirocumab) Injection United States On May 27, 2022, the Company filed a lawsuit against Amgen in the United States District Court for the District of Delaware, alleging that, beginning in 2020, Amgen engaged in an anticompetitive bundling scheme which was designed to exclude Praluent from the market in violation of federal and state laws. The lawsuit seeks damages for harm caused by the alleged scheme, as well as injunctive relief restraining Amgen from continuing its alleged anticompetitive conduct. On February 10, 2023, the court denied Amgen's motion to stay these proceedings; and on March 21, 2023, the court denied Amgen's motion to dismiss the complaint. On August 28, 2023, the Company filed an amended complaint in this matter; and, as part of its response, on September 20, 2023, Amgen filed a counterclaim alleging that the Company engaged in unfair business practices in violation of state law. On April 10, 2025, the court denied Amgen's motion for summary judgment. A trial was held in May 2025. On May 15, 2025, the jury reached a verdict in Regeneron's favor on nine of the ten counts submitted to it and awarded Regeneron $135.6 million in compensatory damages and $271.2 million in punitive damages. On June 20, 2025, Amgen filed a post-trial motion for judgment as a matter of law or, in the alternative, for a new trial. Also on June 20, 2025, the Company filed a post-trial motion for (i) permanent injunctive relief, (ii) a constructive trust, and (iii) prejudgment interest. An oral hearing on Amgen's and Regeneron's respective post-trial motions has been scheduled for August 27, 2025. Europe On June 1, 2023, Sanofi filed an action in the Munich Central Division of the Unified Patent Court (the "UPC") seeking revocation of Amgen's European Patent No. 3,666,797 (the "'797 Patent"). The '797 Patent is a divisional patent of European Patent No. 2,215,124 (the "'124 Patent") (i.e., a patent that shares the same priority date, disclosure, and patent term of the parent '124 Patent), which was previously invalidated by the Technical Board of Appeal of the EPO. On July 16, 2024, following a trial, the Munich Central Division of the UPC issued a decision revoking the '797 Patent in its entirety. On September 16, 2024, Amgen appealed the decision of the Munich Central Division of the UPC to the Court of Appeal of the UPC. An oral hearing before the Court of Appeal of the UPC has been scheduled for August 2025. Also on June 1, 2023, Amgen filed a lawsuit against the Company and certain of Sanofi's affiliated entities in the Munich Local Division of the UPC alleging infringement of the '797 Patent. The lawsuit seeks, among other things, a permanent injunction in several countries in Europe and monetary damages. On July 29, 2024, the Munich Local Division of the UPC ordered a stay of the infringement lawsuit in light of the decision of the Munich Central Division of the UPC to revoke the '797 Patent in its entirety (discussed above). The Company and Sanofi are also seeking revocation of the '797 Patent at the EPO. On April 3, 2025, the OD upheld the '797 Patent as valid. The Company and Sanofi have appealed this decision to the Technical Board of Appeal of the EPO. An oral hearing before the Technical Board of Appeal of the EPO has been scheduled for April 2026. Department of Justice Matters In January 2017, the Company received a subpoena from the U.S. Attorney's Office for the District of Massachusetts requesting documents relating to its support of 501(c)(3) organizations that provide financial assistance to patients; documents concerning its provision of financial assistance to patients with respect to products sold or developed by Regeneron (including EYLEA, Praluent, ARCALYST®, and ZALTRAP®); and certain other related documents and communications. On June 24, 2020, the U.S. Attorney's Office for the District of Massachusetts filed a civil complaint in the U.S. District Court for the District of Massachusetts alleging violations of the federal Anti-Kickback Statute, and asserting causes of action under the federal False Claims Act and state law (the "June 2020 Civil Complaint"). On September 27, 2023, the court (i) denied in part and granted in part the Company's motion for summary judgment and (ii) denied in its entirety the motion for partial summary judgment filed by the U.S. Attorney's Office for the District of Massachusetts. On October 25, 2023, the court certified for interlocutory appeal a portion of the court's September 27, 2023 order that addressed the causation standard applicable to the alleged violations of the federal Anti-Kickback Statute and federal False Claims Act. On February 18, 2025, the U.S. Court of Appeals for the First Circuit affirmed the portion of the court's September 27, 2023 order that had been certified for interlocutory appeal. In September 2019, the Company and Regeneron Healthcare Solutions, Inc., a wholly-owned subsidiary of the Company, each received a civil investigative demand ("CID") from the U.S. Department of Justice pursuant to the federal False Claims Act relating to remuneration paid to physicians in the form of consulting fees, advisory boards, speaker fees, and payment or reimbursement for travel and entertainment allegedly in violation of the federal Anti-Kickback Statute. The CIDs relate to EYLEA, Praluent, Dupixent, ZALTRAP, ARCALYST, and Kevzara and cover the period from January 2015 to the present. On June 3, 2021, the United States District Court for the Central District of California unsealed a qui tam complaint filed against the Company, Regeneron Healthcare Solutions, Inc., and Sanofi-Aventis U.S. LLC by two qui tam plaintiffs (known as relators) purportedly on behalf of the United States and various states (the "State Plaintiffs"), asserting causes of action under the federal False Claims Act and state law. Also on June 3, 2021, the United States and the State Plaintiffs notified the court of their decision to decline to intervene in the case. On October 29, 2021, the qui tam plaintiffs filed an amended complaint in this matter. On January 14, 2022, the Company filed a motion to dismiss the amended complaint in its entirety. On July 25, 2023, the court granted in part and denied in part the Company's motion to dismiss. On September 1, 2023, the Company filed a second motion to dismiss the amended complaint or, in the alternative, a motion for judgment on the pleadings. On July 31, 2024 and August 15, 2024, respectively, the District Court granted the Company's second motion to dismiss the amended complaint with respect to the remaining causes of action under federal law and declined to exercise supplemental jurisdiction over the remaining causes of action under state law. On August 26, 2024, the qui tam plaintiffs filed a notice of appeal. In June 2021, the Company received a CID from the U.S. Department of Justice pursuant to the federal False Claims Act. The CID states that the investigation concerns allegations that the Company (i) violated the False Claims Act by paying kickbacks to distributors and ophthalmology practices to induce purchase of EYLEA, including through discounts, rebates, credit card fees, free units of EYLEA, and inventory management systems; and (ii) inflated reimbursement rates for EYLEA by excluding applicable discounts, rebates, and benefits from the average sales price reported to the Centers for Medicare & Medicaid Services. The CID covers the period from January 2011 through June 2021. On November 29, 2023, the U.S. Department of Justice informed the Company that it had filed a notice of partial intervention in this matter. On March 28, 2024, the Department of Justice and the U.S. Attorney's Office for the District of Massachusetts filed a civil complaint intervention (the "March 2024 Civil Complaint") in the U.S. District Court for the District of Massachusetts asserting causes of action under the federal False Claims Act and a claim for unjust enrichment. Also on March 28, 2024, the U.S. District Court of the District of Massachusetts unsealed a qui tam complaint against the Company, AmerisourceBergen, and Besse Medical by two qui tam plaintiffs (known as relators) purportedly on behalf of the United States and various states and municipalities, asserting causes of action under the federal False Claims Act and state and local laws, and alleging violations of the federal Anti-Kickback statute. On June 25, 2024, the States of Colorado, Georgia, Michigan, North Carolina, Texas, and Washington filed a civil complaint in partial intervention (the "June 2024 Civil Complaint") in the U.S. District Court for the District of Massachusetts asserting causes of action under various state laws. On July 18, 2024, the Company filed a motion to dismiss the March 2024 Civil Complaint and the June 2024 Civil Complaint. An oral hearing on the Company's motion to dismiss was held on December 16, 2024. On April 29, 2025, the court denied the Company's motion to dismiss. On May 27, 2025, the Company filed its answers to the March 2024 Civil Complaint and the June 2024 Civil Complaint. On June 17, 2025, the court granted a motion by the States of Maine, Nebraska, Ohio, Oregon, and Wyoming to intervene in the action. On June 18, 2025, those states filed a consolidated complaint asserting causes of action under their respective state laws (the "June 2025 Civil Complaint"). On July 23, 2025, the Company filed its answer and counterclaims to the June 2025 Civil Complaint. Proceedings Initiated by Other Payors The Company is party to several lawsuits relating to the conduct alleged in the June 2020 Civil Complaint discussed under "Department of Justice Matters" above. These lawsuits were filed by UnitedHealthcare Insurance Company and United Healthcare Services, Inc. (collectively, "UHC") and Humana Inc. ("Humana") in the United States District Court for the Southern District of New York on December 17, 2020 and July 22, 2021, respectively; and by Blue Cross and Blue Shield of Massachusetts, Inc. and Blue Cross and Blue Shield of Massachusetts HMO Blue, Inc. (collectively, "BCBS"), Medical Mutual of Ohio ("MMO"), Horizon Healthcare Services, Inc. d/b/a Horizon Blue Cross Blue Shield of New Jersey ("Horizon"), and Local 464A United Food and Commercial Workers Union Welfare Service Benefit Fund ("Local 464A") in the U.S. District Court for the District of Massachusetts on December 20, 2021, February 23, 2022, April 4, 2022, and June 17, 2022, respectively. These lawsuits allege causes of action under state law and the federal Racketeer Influenced and Corrupt Organizations Act ("RICO") and seek monetary damages and equitable relief. The MMO and Local 464A lawsuits are putative class action lawsuits. On December 29, 2021, the lawsuits filed by UHC and Humana were stayed by the United States District Court for the Southern District of New York pending resolution of the proceedings before the U.S. District Court for the District of Massachusetts concerning the allegations in the June 2020 Civil Complaint. On September 27, 2022, the lawsuits filed by BCBS, MMO, and Horizon were stayed by the U.S. District Court for the District of Massachusetts pending resolution of the proceedings before the same court concerning the allegations in the June 2020 Civil Complaint; and, in light of these stays, the parties to the Local 464A action have also agreed to stay that matter. On June 24, 2024, a group of plaintiffs purporting to be assignees of claims by various Medicare Advantage plans and related entities filed a putative class action complaint in the U.S. District Court for the District of Columbia on behalf of Medicare Advantage plans and other payors. The lawsuit relates to the conduct alleged in the June 2020 Civil Complaint, March 2024 Civil Complaint, and June 2024 Civil Complaint discussed under "Department of Justice Matters" above. The lawsuit alleges causes of action under state law and RICO and seeks monetary damages and equitable relief. On October 22, 2024, the Company filed a motion to transfer the proceedings to the U.S. District Court for the District of Massachusetts or, in the alternative, to stay the proceedings or dismiss the proceedings. On January 28, 2025, pursuant to a stipulation among the parties, the proceedings were transferred to the U.S. District Court for the District of Massachusetts. On February 1, 2025, the parties jointly filed a stipulation to stay the action pending resolution of the proceedings before the same court concerning the allegations in the June 2020 Civil Complaint. Shareholder Derivative Complaint – Department of Justice June 2020 Civil Complaint Matters On June 29, 2021, an alleged shareholder filed a shareholder derivative complaint in the New York Supreme Court, naming the then-current and certain former members of the Company's board of directors and certain then-current and former executive officers of the Company as defendants and Regeneron as a nominal defendant. The complaint asserts that the individual defendants breached their fiduciary duties in relation to the allegations in the June 2020 Civil Complaint discussed under "Department of Justice Matters" above. The complaint seeks an award of damages allegedly sustained by the Company; an order requiring Regeneron to take all necessary actions to reform and improve its corporate governance and internal procedures; disgorgement from the individual defendants of all profits and benefits obtained by them resulting from their sales of Regeneron stock; and costs and disbursements of the action, including attorneys' fees. On July 28, 2021, the defendants filed a notice of removal, removing the case from the New York Supreme Court to the U.S. District Court for the Southern District of New York. On September 23, 2021, the plaintiff moved to remand the case to the New York Supreme Court. Also on September 23, 2021, the individual defendants moved to dismiss the complaint in its entirety. On December 19, 2022, the U.S. District Court for the Southern District of New York denied the plaintiff's motion to remand the case and granted a motion to stay the case pending resolution of the proceedings before the U.S. District Court for the District of Massachusetts concerning the allegations in the June 2020 Civil Complaint. As a result of the stay, the court also terminated the Company's motion to dismiss the complaint without prejudice. The Company can therefore renew the motion to dismiss upon conclusion of the stay. Shareholder Derivative Complaints – Department of Justice March 2024 Civil Complaint Matters On January 16 and January 22, 2025, purported shareholders filed two separate shareholder derivative complaints in the U.S. District Court for the Southern District of New York against members of the Company's board of directors and certain current and former executive officers of the Company as defendants and Regeneron as a nominal defendant. The complaints each allege that the individual defendants, among other things, breached their fiduciary duties to the Company by failing to properly manage and oversee the Company in connection with the conduct alleged in the March 2024 Civil Complaint discussed under "Department of Justice Matters" above. The complaints also each allege that the individual defendants breached the federal securities laws, wasted corporate assets, and unjustly enriched themselves at the expense of the Company. The complaints each seek, among other things, an award of damages allegedly sustained by the Company as a result of the alleged misconduct of the individual defendants; an order requiring the individual defendants to take all necessary actions to reform and improve the Company's corporate governance and internal procedures; and costs and disbursements of the applicable action, including attorneys' fees. On June 3, 2025, the court consolidated the two separate shareholder derivative complaints pursuant to a joint stipulation by the parties. On June 5, 2025, two purported shareholders filed separate shareholder derivative complaints in the New York Supreme Court against members of the Company's board of directors and certain current and former executive officers of the Company as defendants and Regeneron as a nominal defendant. These actions make similar allegations to the ones filed on January 16 and January 22, 2025. On June 16, 2025, the Company filed notices of removal, removing both of the newly filed actions from the New York Supreme Court to the U.S. District Court of the Southern District of New York. On July 16, 2025, the purported shareholders each filed a motion to remand their respective actions back to the New York Supreme Court. On July 30, 2025, a purported shareholder filed another shareholder derivative complaint in the U.S. District Court for the Southern District of New York against members of the Company's board of directors and certain current and former executive officers of the Company as defendants and Regeneron as a nominal defendant. This complaint makes similar allegations to the ones filed on January 16, 2025, January 22, 2025, and June 5, 2025. Shareholder Derivative Complaint – Director Compensation On July 22, 2025, an alleged shareholder filed a shareholder derivative complaint in the New York Supreme Court, naming the current non-employee members of our board of directors, and the co-Chairs of our board of directors (who also serve as our President and Chief Executive Officer and our President and Chief Scientific Officer, respectively) as defendants and Regeneron as a nominal defendant. The complaint asserts that the individual defendants breached their fiduciary duties and/or were unjustly enriched when they approved and/or received allegedly excessive non-employee director compensation in 2024 and 2025, and that this allegedly excessive compensation was a waste of corporate assets. The complaint seeks damages in favor of Regeneron for the alleged breaches of fiduciary duties, unjust enrichment, and waste of corporate assets; improvements to Regeneron's corporate governance and internal procedures; equitable relief, including restitution from the individual defendants; and award of the costs of the action, including attorneys' fees. Class Action Civil Complaint On January 7, 2025, a purported shareholder filed a putative class action civil complaint, on behalf of himself and all others similarly situated, in the U.S. District Court for the Southern District of New York against the Company and certain current and former executive officers of the Company. The complaint asserts violations of federal securities laws in connection with statements or disclosures purportedly related to the conduct alleged in the March 2024 Civil Complaint discussed under "Department of Justice Matters" above. On July 10, 2025, the court appointed a lead plaintiff and lead counsel for the action. Sanofi Litigation On November 18, 2024, the Company filed a lawsuit (as amended on December 20, 2024) in the United States District Court for the Southern District of New York against Sanofi and certain of its affiliated entities. The lawsuit alleges that the defendants breached certain provisions of the parties' Amended and Restated License and Collaboration Agreement, dated as of November 10, 2009 (as amended, the "Collaboration Agreement"), concerning Sanofi's obligation to provide Regeneron with full access to material information relating to the commercialization of Dupixent or other products commercialized pursuant to the Collaboration Agreement and Regeneron's audit rights under the Collaboration Agreement. The lawsuit seeks a declaratory judgment, injunctive relief, damages, and other relief. On July 3, 2025, Sanofi filed a motion to dismiss the complaint.

From time to time, the Company is a party to legal proceedings in the course of the Company's business. The outcome of any such proceedings, regardless of the merits, is inherently uncertain. If the Company is unable to prevail in one or more of such proceedings, its consolidated financial position, results of operations, and future cash flows may be materially adversely impacted. Costs associated with the Company's involvement in legal proceedings are expensed as incurred. The Company recognizes gain contingencies associated with such proceedings when the award or recovery is realized or realizable and loss contingencies when it is probable that a liability will be incurred and the amount of loss can be reasonably estimated. As of June 30, 2025 and December 31, 2024, the Company's accruals for loss contingencies were not material. There are certain loss contingencies that the Company deems reasonably possible for which the possible loss or range of possible loss is not estimable at this time.

On August 2, 2022, the Company filed a patent infringement lawsuit against Mylan Pharmaceuticals Inc. ("Mylan"), a wholly-owned subsidiary of Viatris Inc., in the United States District Court for the Northern District of West Virginia alleging that Mylan's filing for U.S. Food and Drug Administration ("FDA") approval of an aflibercept 2 mg biosimilar infringes certain Company patents. On June 5, 2023, Biocon Biologics Inc. ("Biocon"), as successor-in-interest to the aflibercept 2 mg biosimilar, was joined as a defendant to the lawsuit. A trial was held in June 2023 concerning certain claims of the '601 Patent, the '572 Patent, and the Company's U.S. Patent No. 11,084,865 (the "'865 Patent"). On December 27, 2023, the court issued a decision finding that (i) the asserted claims of the '865 Patent were valid and infringed by Mylan and Biocon and (ii) the asserted claims of the '601 and '572 Patents were infringed by Mylan and Biocon but were invalid as obvious. On June 11, 2024, the court granted the Company's motion for a permanent injunction, enjoining Mylan and Biocon from selling in the United States their aflibercept 2 mg biosimilar until the expiration of the '865 Patent. On June 21, 2024, Mylan and Biocon filed a notice of appeal of the court's December 27, 2023 and June 11, 2024 decisions to the Federal Circuit. An oral hearing concerning Mylan and Biocon's appeal was held on February 7, 2025. On April 14, 2025, the parties entered into a settlement agreement, pursuant to which Mylan and Biocon's appeal to the Federal Circuit and all related litigation have been dismissed and Biocon is precluded from launching its aflibercept 2 mg biosimilar until the second half of 2026.

On November 8, November 22, and November 29, 2023, respectively, the Company filed patent infringement lawsuits against Celltrion, Inc. ("Celltrion"), Samsung Bioepis Co., Ltd. ("Samsung Bioepis"), and Formycon AG ("Formycon") in the United States District Court for the Northern District of West Virginia following service on Regeneron of each company's notice of commercial marketing. The lawsuits alleged that each company had infringed certain Company patents, including based on each company's filing for FDA approval of an aflibercept 2 mg biosimilar. On December 27, 2023, the Company filed a second patent infringement lawsuit against Samsung Bioepis. On June 14, June 21, and June 28, 2024, respectively, the court granted the Company's motions for preliminary injunctions against Samsung Bioepis, Formycon, and Celltrion; each of these decisions was appealed to the Federal Circuit. On January 29, 2025, the Federal Circuit affirmed the lower court's preliminary injunction decisions against Samsung Bioepis and Formycon; and on March 5, 2025, the Federal Circuit affirmed the lower court's preliminary injunction decision against Celltrion. On May 23, 2025, Formycon petitioned the lower court to revoke the preliminary injunction.

On January 10, 2024, the Company filed a patent infringement lawsuit against Amgen Inc. ("Amgen") in the United States District Court for the Central District of California alleging that Amgen's filing for FDA approval of an aflibercept 2 mg biosimilar infringed certain Company patents. On April 11, 2024, the United States Judicial Panel on Multidistrict Litigation granted the Company's motion to transfer this lawsuit to the United States District Court for the Northern District of West Virginia for coordinated and consolidated pretrial proceedings with the lawsuits described in the preceding paragraph. On September 23, 2024, the court denied the Company's motion for a preliminary injunction; and on September 25, 2024, the Federal Circuit issued an administrative stay pending its review of the Company's temporary injunction motion. On October 22, 2024, the Federal Circuit denied the Company's temporary injunction motion and lifted the administrative stay. On March 14, 2025, the Federal Circuit affirmed the lower court's preliminary injunction decision. On June 17, 2025, the Company filed an additional patent infringement lawsuit against Amgen in the United States District Court for the Central District of California

On August 26, 2024, the Company filed a patent infringement lawsuit against Sandoz Inc. ("Sandoz") in the United States District Court for the District of New Jersey alleging that Sandoz's filing for FDA approval of an aflibercept 2 mg biosimilar infringed certain Company patents. On September 12, 2024, the United States Judicial Panel on Multidistrict Litigation granted the Company's motion to transfer this lawsuit to the United States District Court for the Northern District of West Virginia for coordinated and consolidated pretrial proceedings with the lawsuits described in the preceding paragraphs. On July 11, 2025, the Company filed a motion for a preliminary injunction against Sandoz based on the '865 Patent.

Various parties, including Amgen and other, anonymous parties, are seeking revocation of the Company's European Patent Nos. 2,944,306 (the "'306 Patent"), 3,716,992 (the "'992 Patent"), and 3,384,049 (the "'049 Patent") before the Opposition Division ("OD") of the EPO. On November 26, 2024, following an oral hearing, the OD announced its decision to revoke the '306 Patent. On March 11, 2025, the Company appealed the OD's decision. Oral hearings concerning the '992 and '049 Patents have been scheduled for October and December 2025, respectively.

Various parties, including Samsung Bioepis and Formycon and/or their affiliated entities, are seeking revocation of the '306 Patent, the '992 Patent, and the Company's European Patent No. 2,364,691 (the "'691 Patent") and/or a declaration that its aflibercept 2 mg biosimilar would not infringe these patents in several European national courts (including those in Belgium, France, Germany, Italy, the Netherlands, and the United Kingdom). In the United Kingdom, the Company has filed a preemptive counterclaim against Formycon, Klinge Biopharma GmbH, and Samsung Bioepis UK Limited for infringement of the '306 Patent and the '691 Patent. In April 2025, the Company and Amgen entered into a settlement agreement, pursuant to which Amgen is no longer party to the United Kingdom proceedings. In Germany, following a trial held in June 2025, the German Federal Patent Court upheld the '691 Patent as valid and dismissed the revocation proceeding brought by Samsung Bioepis. In the United Kingdom, trials concerning the '691 and '306 Patents were held in June 2025, and the '992 Patent proceedings are stayed pending resolution of the EPO proceedings concerning this patent. In the Netherlands, a trial concerning the '691 and '306 Patents was held on July 18, 2025.

On May 9, 2023, Amgen Canada Inc. ("Amgen Canada") filed invalidation proceedings against the Company in the Federal Court of Canada seeking revocation of the Company's Canadian Patent Nos. 2,654,510 (the "'510 Patent") and 3,007,276 (the "'276 Patent"). On September 14, 2023, the Company, Bayer Inc., and Bayer Healthcare LLC filed patent infringement lawsuits against Amgen Canada in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of Bayer Healthcare LLC's Canadian Patent No. 2,970,315 (the "'315 Patent"). On September 14, 2023, the Company and Bayer Inc. filed three separate patent infringement lawsuits against Amgen Canada in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the Company's Canadian Patent Nos. 3,129,193 (the "'193 Patent"), 2,965,495 (the "'495 Patent"), and 2,906,768 (the "'768 Patent"), respectively. On October 11, 2023, the Company, Bayer Inc., and Bayer Healthcare LLC filed two separate patent infringement lawsuits against Amgen Canada in the Federal Court of Canada seeking a declaration that the making,

constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the Company's '510 Patent and '276 Patent, respectively. On June 28, 2024, Amgen Canada filed a motion to delist the '276 Patent from the Canada Patent Register; and on November 20, 2024, the court granted Amgen Canada's motion. That decision has been appealed by the Company and Bayer. A trial concerning the '510 Patent and the '276 Patent was held in May–June 2025; and a trial concerning the '315 Patent and the '193 Patent has been scheduled for August–September 2025.

On January 24, 2025, the Company, Bayer Inc., and Bayer Healthcare LLC filed patent infringement lawsuits against Sandoz Canada Inc. in the Federal Court of Canada seeking a declaration that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar would directly or indirectly infringe one or more claims of the '510 Patent, the '276 Patent, the '495 Patent, the '768 Patent, the '193 Patent, the '315 Patent, and Canadian Patent No. 3,137,326 (the "'326 Patent"). A trial concerning the '510 Patent, the '276 Patent, the '315 Patent, and the '326 Patent has been scheduled for October–November 2026.

The Company and, as applicable, Bayer Consumer Care AG, have also filed patent infringement lawsuits in the Seoul Central District Court against various parties including Samsung Bioepis and its parent company Samsung Biologics Co., Ltd. (collectively, "Samsung"), Sam Chun Dang Pharm. Co., Ltd. and OPTUS Pharmaceutical Co., Ltd., and Celltrion. These lawsuits seek damages and/or injunctive relief and allege that the making, constructing, using, or selling of an aflibercept 2 mg biosimilar by the relevant defendant(s) would infringe one or more claims of the '811 Patent and/or the Company's Korean Patent Nos. 659477 (the "'477 Patent") and 2519234 (the "'234 Patent"). On February 7, 2025, the Seoul Central District Court granted the Company's preliminary injunction request against Samsung on the basis of the '811 Patent; Samsung has appealed that decision. The preliminary injunction against Samsung prohibits Samsung from manufacturing and selling its aflibercept 2 mg biosimilar in South Korea. Also on February 7, 2025, the Seoul Central District Court denied Regeneron's preliminary injunction request against Celltrion; Regeneron has appealed that decision.

On July 17, 2020, the Company filed an antitrust lawsuit (as amended on January 25, 2021) against Novartis Pharma AG, Novartis Pharmaceuticals Corporation, and Novartis Technology LLC (collectively, "Novartis") and Vetter Pharma International Gmbh in the United States District Court for the Southern District of New York seeking a judgment that the defendants' conduct relating to Novartis's attempt to assert its U.S. Patent No. 9,220,631 against Regeneron in 2020 violated Sections 1 and 2 of the Sherman Antitrust Act of 1890, as amended (the "Sherman Antitrust Act"), and constituted tortious interference with contract. The Company is also seeking injunctive relief and treble damages. On September 21, 2021, this lawsuit was transferred to the Northern District of New York. On June 10, 2022, the Company filed an appeal of the District Court's decision to dismiss the amended complaint with the U.S. Court of Appeals for the Second Circuit (the "Second Circuit"). On March 18, 2024, the Second Circuit reversed the District Court's decision to dismiss the amended complaint and remanded the lawsuit to the District Court for further proceedings consistent with the Second Circuit's opinion. On November 19, 2024, the Company moved to transfer the lawsuit back to the Southern District of New York, which motion was granted on December 5, 2024.

On May 27, 2022, the Company filed a lawsuit against Amgen in the United States District Court for the District of Delaware, alleging that, beginning in 2020, Amgen engaged in an anticompetitive bundling scheme which was designed to exclude Praluent from the market in violation of federal and state laws. The lawsuit seeks damages for harm caused by the alleged scheme, as well as injunctive relief restraining Amgen from continuing its alleged anticompetitive conduct. On February 10, 2023, the court denied Amgen's motion to stay these proceedings; and on March 21, 2023, the court denied Amgen's motion to dismiss the complaint. On August 28, 2023, the Company filed an amended complaint in this matter; and, as part of its response, on September 20, 2023, Amgen filed a counterclaim alleging that the Company engaged in unfair business practices in violation of state law. On April 10, 2025, the court denied Amgen's motion for summary judgment. A trial was held in May 2025. On May 15, 2025, the jury reached a verdict in Regeneron's favor on nine of the ten counts submitted to it and awarded Regeneron $135.6 million in compensatory damages and $271.2 million in punitive damages. On June 20, 2025, Amgen filed a post-trial motion for judgment as a matter of law or, in the alternative, for a new trial. Also on June 20, 2025, the Company filed a post-trial motion for (i) permanent injunctive relief, (ii) a constructive trust, and (iii) prejudgment interest. An oral hearing on Amgen's and Regeneron's respective post-trial motions has been scheduled for August 27, 2025.

On June 1, 2023, Sanofi filed an action in the Munich Central Division of the Unified Patent Court (the "UPC") seeking revocation of Amgen's European Patent No. 3,666,797 (the "'797 Patent"). The '797 Patent is a divisional patent of European Patent No. 2,215,124 (the "'124 Patent") (i.e., a patent that shares the same priority date, disclosure, and patent term of the parent '124 Patent), which was previously invalidated by the Technical Board of Appeal of the EPO. On July 16, 2024, following a trial, the Munich Central Division of the UPC issued a decision revoking the '797 Patent in its entirety. On September 16, 2024, Amgen appealed the decision of the Munich Central Division of the UPC to the Court of Appeal of the UPC. An oral hearing before the Court of Appeal of the UPC has been scheduled for August 2025.

In January 2017, the Company received a subpoena from the U.S. Attorney's Office for the District of Massachusetts requesting documents relating to its support of 501(c)(3) organizations that provide financial assistance to patients; documents concerning its provision of financial assistance to patients with respect to products sold or developed by Regeneron (including EYLEA, Praluent, ARCALYST®, and ZALTRAP®); and certain other related documents and communications. On June 24, 2020, the U.S. Attorney's Office for the District of Massachusetts filed a civil complaint in the U.S. District Court for the District of Massachusetts alleging violations of the federal Anti-Kickback Statute, and asserting causes of action under the federal False Claims Act and state law (the "June 2020 Civil Complaint"). On September 27, 2023, the court (i) denied in part and granted in part the Company's motion for summary judgment and (ii) denied in its entirety the motion for partial summary judgment filed by the U.S. Attorney's Office for the District of Massachusetts. On October 25, 2023, the court certified for interlocutory appeal a portion of the court's September 27, 2023 order that addressed the causation standard applicable to the alleged violations of the federal Anti-Kickback Statute and federal False Claims Act. On February 18, 2025, the U.S. Court of Appeals for the First Circuit affirmed the portion of the court's September 27, 2023 order that had been certified for interlocutory appeal.

In September 2019, the Company and Regeneron Healthcare Solutions, Inc., a wholly-owned subsidiary of the Company, each received a civil investigative demand ("CID") from the U.S. Department of Justice pursuant to the federal False Claims Act relating to remuneration paid to physicians in the form of consulting fees, advisory boards, speaker fees, and payment or reimbursement for travel and entertainment allegedly in violation of the federal Anti-Kickback Statute. The CIDs relate to EYLEA, Praluent, Dupixent, ZALTRAP, ARCALYST, and Kevzara and cover the period from January 2015 to the present. On June 3, 2021, the United States District Court for the Central District of California unsealed a qui tam complaint filed against the Company, Regeneron Healthcare Solutions, Inc., and Sanofi-Aventis U.S. LLC by two qui tam plaintiffs (known as relators) purportedly on behalf of the United States and various states (the "State Plaintiffs"), asserting causes of action under

the federal False Claims Act and state law. Also on June 3, 2021, the United States and the State Plaintiffs notified the court of their decision to decline to intervene in the case. On October 29, 2021, the qui tam plaintiffs filed an amended complaint in this matter. On January 14, 2022, the Company filed a motion to dismiss the amended complaint in its entirety. On July 25, 2023, the court granted in part and denied in part the Company's motion to dismiss. On September 1, 2023, the Company filed a second motion to dismiss the amended complaint or, in the alternative, a motion for judgment on the pleadings. On July 31, 2024 and August 15, 2024, respectively, the District Court granted the Company's second motion to dismiss the amended complaint with respect to the remaining causes of action under federal law and declined to exercise supplemental jurisdiction over the remaining causes of action under state law. On August 26, 2024, the qui tam plaintiffs filed a notice of appeal.

In June 2021, the Company received a CID from the U.S. Department of Justice pursuant to the federal False Claims Act. The CID states that the investigation concerns allegations that the Company (i) violated the False Claims Act by paying kickbacks to distributors and ophthalmology practices to induce purchase of EYLEA, including through discounts, rebates, credit card fees, free units of EYLEA, and inventory management systems; and (ii) inflated reimbursement rates for EYLEA by excluding applicable discounts, rebates, and benefits from the average sales price reported to the Centers for Medicare & Medicaid Services. The CID covers the period from January 2011 through June 2021. On November 29, 2023, the U.S. Department of Justice informed the Company that it had filed a notice of partial intervention in this matter. On March 28, 2024, the Department of Justice and the U.S. Attorney's Office for the District of Massachusetts filed a civil complaint intervention (the "March 2024 Civil Complaint") in the U.S. District Court for the District of Massachusetts asserting causes of action under the federal False Claims Act and a claim for unjust enrichment. Also on March 28, 2024, the U.S. District Court of the District of Massachusetts unsealed a qui tam complaint against the Company, AmerisourceBergen, and Besse Medical by two qui tam plaintiffs (known as relators) purportedly on behalf of the United States and various states and municipalities, asserting causes of action under the federal False Claims Act and state and local laws, and alleging violations of the federal Anti-Kickback statute. On June 25, 2024, the States of Colorado, Georgia, Michigan, North Carolina, Texas, and Washington filed a civil complaint in partial intervention (the "June 2024 Civil Complaint") in the U.S. District Court for the District of Massachusetts asserting causes of action under various state laws. On July 18, 2024, the Company filed a motion to dismiss the March 2024 Civil Complaint and the June 2024 Civil Complaint. An oral hearing on the Company's motion to dismiss was held on December 16, 2024. On April 29, 2025, the court denied the Company's motion to dismiss. On May 27, 2025, the Company filed its answers to the March 2024 Civil Complaint and the June 2024 Civil Complaint. On June 17, 2025, the court granted a motion by the States of Maine, Nebraska, Ohio, Oregon, and Wyoming to intervene in the action. On June 18, 2025, those states filed a consolidated complaint asserting causes of action under their respective state laws (the "June 2025 Civil Complaint"). On July 23, 2025, the Company filed its answer and counterclaims to the June 2025 Civil Complaint.

The Company is party to several lawsuits relating to the conduct alleged in the June 2020 Civil Complaint discussed under "Department of Justice Matters" above. These lawsuits were filed by UnitedHealthcare Insurance Company and United Healthcare Services, Inc. (collectively, "UHC") and Humana Inc. ("Humana") in the United States District Court for the Southern District of New York on December 17, 2020 and July 22, 2021, respectively; and by Blue Cross and Blue Shield of Massachusetts, Inc. and Blue Cross and Blue Shield of Massachusetts HMO Blue, Inc. (collectively, "BCBS"), Medical Mutual of Ohio ("MMO"), Horizon Healthcare Services, Inc. d/b/a Horizon Blue Cross Blue Shield of New Jersey ("Horizon"), and Local 464A United Food and Commercial Workers Union Welfare Service Benefit Fund ("Local 464A") in the U.S. District Court for the District of Massachusetts on December 20, 2021, February 23, 2022, April 4, 2022, and June 17, 2022, respectively. These lawsuits allege causes of action under state law and the federal Racketeer Influenced and Corrupt Organizations Act ("RICO") and seek monetary damages and equitable relief. The MMO and Local 464A lawsuits are putative class action lawsuits. On December 29, 2021, the lawsuits filed by UHC and Humana were stayed by the United States District Court for the Southern District of New York pending resolution of the proceedings before the U.S. District Court for the District of Massachusetts concerning the allegations in the June 2020 Civil Complaint. On September 27, 2022, the lawsuits filed by BCBS, MMO, and Horizon were stayed by the U.S. District Court for the District of Massachusetts pending resolution of the proceedings before the same court concerning the allegations in the June 2020 Civil Complaint; and, in light of these stays, the parties to the Local 464A action have also agreed to stay that matter.

On June 24, 2024, a group of plaintiffs purporting to be assignees of claims by various Medicare Advantage plans and related entities filed a putative class action complaint in the U.S. District Court for the District of Columbia on behalf of Medicare Advantage plans and other payors. The lawsuit relates to the conduct alleged in the June 2020 Civil Complaint, March 2024 Civil Complaint, and June 2024 Civil Complaint discussed under "Department of Justice Matters" above. The lawsuit alleges causes of action under state law and RICO and seeks monetary damages and equitable relief. On October 22, 2024, the Company filed a motion to transfer the proceedings to the U.S. District Court for the District of Massachusetts or, in the alternative, to stay the proceedings or dismiss the proceedings. On January 28, 2025, pursuant to a stipulation among the parties, the proceedings were transferred to the U.S. District Court for the District of Massachusetts. On February 1, 2025, the

On June 29, 2021, an alleged shareholder filed a shareholder derivative complaint in the New York Supreme Court, naming the then-current and certain former members of the Company's board of directors and certain then-current and former executive officers of the Company as defendants and Regeneron as a nominal defendant. The complaint asserts that the individual defendants breached their fiduciary duties in relation to the allegations in the June 2020 Civil Complaint discussed under "Department of Justice Matters" above. The complaint seeks an award of damages allegedly sustained by the Company; an order requiring Regeneron to take all necessary actions to reform and improve its corporate governance and internal procedures; disgorgement from the individual defendants of all profits and benefits obtained by them resulting from their sales of Regeneron stock; and costs and disbursements of the action, including attorneys' fees. On July 28, 2021, the defendants filed a notice of removal, removing the case from the New York Supreme Court to the U.S. District Court for the Southern District of New York. On September 23, 2021, the plaintiff moved to remand the case to the New York Supreme Court. Also on September 23, 2021, the individual defendants moved to dismiss the complaint in its entirety. On December 19, 2022, the U.S. District Court for the Southern District of New York denied the plaintiff's motion to remand the case and granted a motion to stay the case pending resolution of the proceedings before the U.S. District Court for the District of Massachusetts concerning the allegations in the June 2020 Civil Complaint. As a result of the stay, the court also terminated the Company's motion to dismiss the complaint without prejudice. The Company can therefore renew the motion to dismiss upon conclusion of the stay.

On January 16 and January 22, 2025, purported shareholders filed two separate shareholder derivative complaints in the U.S. District Court for the Southern District of New York against members of the Company's board of directors and certain current and former executive officers of the Company as defendants and Regeneron as a nominal defendant. The complaints each allege that the individual defendants, among other things, breached their fiduciary duties to the Company by failing to properly manage and oversee the Company in connection with the conduct alleged in the March 2024 Civil Complaint discussed under "Department of Justice Matters" above. The complaints also each allege that the individual defendants breached the federal securities laws, wasted corporate assets, and unjustly enriched themselves at the expense of the Company. The complaints each seek, among other things, an award of damages allegedly sustained by the Company as a result of the alleged misconduct of the individual defendants; an order requiring the individual defendants to take all necessary actions to reform and improve the Company's corporate governance and internal procedures; and costs and disbursements of the applicable action, including attorneys' fees. On June 3, 2025, the court consolidated the two separate shareholder derivative complaints pursuant to a joint stipulation by the parties.

On June 5, 2025, two purported shareholders filed separate shareholder derivative complaints in the New York Supreme Court against members of the Company's board of directors and certain current and former executive officers of the Company as defendants and Regeneron as a nominal defendant. These actions make similar allegations to the ones filed on January 16 and January 22, 2025. On June 16, 2025, the Company filed notices of removal, removing both of the newly filed actions from the New York Supreme Court to the U.S. District Court of the Southern District of New York. On July 16, 2025, the purported shareholders each filed a motion to remand their respective actions back to the New York Supreme Court.

On July 22, 2025, an alleged shareholder filed a shareholder derivative complaint in the New York Supreme Court, naming the current non-employee members of our board of directors, and the co-Chairs of our board of directors (who also serve as our President and Chief Executive Officer and our President and Chief Scientific Officer, respectively) as defendants and Regeneron as a nominal defendant. The complaint asserts that the individual defendants breached their fiduciary duties and/or were unjustly enriched when they approved and/or received allegedly excessive non-employee director compensation in 2024 and 2025, and that this allegedly excessive compensation was a waste of corporate assets. The complaint seeks damages in favor of Regeneron for the alleged breaches of fiduciary duties, unjust enrichment, and waste of corporate assets; improvements to Regeneron's corporate governance and internal procedures; equitable relief, including restitution from the individual defendants; and award of the costs of the action, including attorneys' fees.

On January 7, 2025, a purported shareholder filed a putative class action civil complaint, on behalf of himself and all others similarly situated, in the U.S. District Court for the Southern District of New York against the Company and certain current and former executive officers of the Company. The complaint asserts violations of federal securities laws in connection with statements or disclosures purportedly related to the conduct alleged in the March 2024 Civil Complaint discussed under "Department of Justice Matters" above. On July 10, 2025, the court appointed a lead plaintiff and lead counsel for the action.

On November 18, 2024, the Company filed a lawsuit (as amended on December 20, 2024) in the United States District Court for the Southern District of New York against Sanofi and certain of its affiliated entities. The lawsuit alleges that the defendants breached certain provisions of the parties' Amended and Restated License and Collaboration Agreement, dated as of November 10, 2009 (as amended, the "Collaboration Agreement"), concerning Sanofi's obligation to provide Regeneron with full access to material information relating to the commercialization of Dupixent or other products commercialized pursuant to the Collaboration Agreement and Regeneron's audit rights under the Collaboration Agreement. The lawsuit seeks a declaratory judgment, injunctive relief, damages, and other relief. On July 3, 2025, Sanofi filed a motion to dismiss the complaint.