Sanofi S.A., FR0000120578

Sanofi stock falls 3.13 percent as four antibodies join alliance

Published on 10/04/2026 at 10:04 | Editorial responsibility: Rafael Müller, Editor-in-Chief AD HOC NEWS

Sanofi stock carries a USD 1 billion upfront payment dated October 1, 2026, for four antibodies with Regeneron. Trading volume reached 3,817,639 shares.

Modern pharmaceutical sterile fill-and-finish manufacturing facility interior with glass vial-filling machines and cleanroom workers in white suits — Sanofi FR0000120578 photorealistic sterile fill-and-finish facility with vial-filling machines and cleanroom workers, Illustration mit AI erstellt.

Sanofi (FR0000120578) stock last traded at EUR 70.810 on Euronext Paris at 5:36 p.m. CET on October 2, 2026, after falling 3.13 percent from the previous close. The move followed a new immunology agreement that commits Sanofi to a USD 1 billion upfront payment.

Four antibodies expand the alliance

According to Sanofi on October 1, 2026, the expanded Regeneron partnership covers four long-acting antibodies targeting interleukin-13, interleukin-4 and related inflammatory pathways. REGN20423 is already in a phase 1 study for atopic dermatitis, while the other three candidates are expected to enter clinical studies in 2027.

The companies will split development and commercialization costs and future profits equally. Regeneron will lead research and development, while Sanofi will lead global commercial activities, leaving Sanofi with commercial control but shared economics on potential products.

Upfront cost meets pipeline need

The agreement gives Regeneron USD 1 billion upfront and allows up to USD 7 billion in additional development, regulatory and commercial milestone payments, according to Reuters on October 1, 2026. Reuters also reported that the companies settled their prior collaboration-related litigation.

The structure offers Sanofi additional immunology assets, but the financial return depends on clinical, regulatory and commercial milestones. Reuters quoted analysts who viewed the agreement as a step toward repairing the partnership while noting that early-stage programs do not remove the longer-term challenge of replacing growth from Dupixent.

Sanofi stock tests its yearly low

On October 2, 2026, Sanofi stock opened at EUR 71.300, reached EUR 72.400 at its session high and touched EUR 69.750 at its session low. The previous close was EUR 73.100, making the last traded price EUR 2.290 lower, while volume reached 3,817,639 shares.

The Paris listing carried a market capitalization of EUR 85.5 billion on October 2, 2026. Sanofi's investor calendar lists third-quarter 2026 results for October 30, 2026, with management scheduled to review the figures during a live webcast.