Exhibit 99.1 Press Release Regeneron Reports First Quarter 2024 Financial and Operating Results • First quarter 2024 revenues decreased 1% to $3.15 billion versus first quarter 2023; excluding RonapreveTM(a)(b), revenues increased 7% • First quarter 2024 Dupixent® global net sales (recorded by Sanofi) increased 24% to $3.08 billion versus first quarter 2023 • First quarter 2024 U.S. net sales for EYLEA® HD and EYLEA® were $1.40 billion, including $200 million from EYLEA HD • First quarter 2024 Libtayo® glob ...