Press Release

Regeneron is resuming enrollment of patients with follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) in its monotherapy trials of odronextamab, a CD20xCD3 bispecific antibody, following agreement with the U.S. Food and Drug

Administration to lift the partial clinical trial hold for those patient cohorts. Trial protocols have been amended to further reduce the incidence of ≥Grade 3 cytokine release syndrome during step-up dosing. Regeneron will recommence enrollment in these patient cohorts effective immediately (trials NCT02290951 and NCT03888105).

Forward-Looking Statements and Use of Digital Media

This statement includes forward-looking statements that involve risks and uncertainties relating to future events and the future performance of Regeneron Pharmaceuticals, Inc. ("Regeneron" or the "Company"), and actual events or results may differ materially from these forward-looking statements. Words such as "anticipate," "expect," "intend," "plan," "believe," "seek," "estimate," variations of such words, and similar expressions are intended to identify such forward-looking statements, although not all forward-looking statements contain these identifying words. These statements concern, and these risks and uncertainties include, among others, the nature, timing, and possible success and therapeutic applications of Regeneron's product candidates and research and clinical programs now underway or planned, including without limitation odronextamab (a CD20xCD3 bispecific antibody); the likelihood, timing, and scope of possible regulatory approval and commercial launch of Regeneron's product candidates, such as odronextamab in follicular lymphoma and/or diffuse large B-cell lymphoma; safety issues resulting from the administration of Regeneron's product candidates (such as odronextamab) in patients, including serious complications or side effects in connection with the use of Regeneron’s product candidates in clinical trials (including the odronextamab trials referenced in this statement); and determinations by regulatory and administrative governmental authorities which may delay or restrict Regeneron's ability to continue to develop or commercialize Regeneron's product candidates (such as odronextamab), such as those relating to the imposition of clinical holds and similar regulatory measures (including whether the U.S. Food and Drug Administration or another regulatory authority may impose a clinical hold or similar regulatory measure with respect to odronextamab in the future). A more complete description of these and other material risks can be found in Regeneron's filings with the U.S. Securities and Exchange Commission, including its Form 10-K for the year ended December 31, 2020 and its Form 10-Q for the quarterly period ended March 31, 2021. Any forward-looking statements are made based on management's current beliefs and judgment, and the reader is cautioned not to rely on any forward-looking statements made by Regeneron. Regeneron does not undertake any obligation to update (publicly or otherwise) any forward-looking statement, whether as a result of new information, future events, or otherwise.

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