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Sanofi pays Regeneron $1 billion upfront to expand Dupixent alliance

Sanofi pays Regeneron $1 billion upfront to expand Dupixent alliance

Money Moves

Four next-generation antibody programs target the same inflammation pathways as Dupixent, which faces a key US patent expiry in 2031

3 days ago: Sanofi and Regeneron expand alliance, settle lawsuit

Overview

Updated Yesterday

Sanofi's biggest product is running out of room. Dupixent, the anti-inflammation antibody it co-developed with Regeneron, brought in $17.8 billion in 2025—roughly 36% of the French company's sales—and a key US patent expires in 2031.

On October 1, Sanofi went back to its original partner. The two companies expanded their alliance with $1 billion upfront and up to $7 billion in milestones for four next-generation, Regeneron-invented antibodies targeting the same type 2 inflammation pathways as Dupixent. The deal also settles a 2024 lawsuit between the partners, and analysts read it as new chief executive Belén Garijo's first major move since taking over in May.

Why it matters

Dupixent supplies 36% of Sanofi's revenue; its key patent expires in 2031, and this $8 billion bet is the race to build its successor.

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Key Indicators

$1 billion
Upfront payment
Sanofi pays Regeneron for the four new antibody programs.
$8 billion
Total deal value
$1 billion upfront plus up to $7 billion in development and sales milestones.
4
New antibody programs
One in Phase 1, three preclinical, targeting IL-13, IL-4 and related inflammatory pathways.
$17.8 billion
Dupixent 2025 sales
The blockbuster's worldwide revenue last year, up 26%.
36%
Share of Sanofi sales
Dupixent's share of Sanofi's roughly €44 billion in 2025 revenue.

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People Involved

Organizations Involved

Timeline

2024 October 2026

3 events Latest: 3 days ago
  1. Sanofi and Regeneron expand alliance, settle lawsuit

    Latest Corporate

    Sanofi pays $1 billion upfront and up to $7 billion in milestones for four Regeneron-invented long-acting antibodies. Profits split 50:50.

  2. Sanofi ends development of two Dupixent successors

    Corporate

    Sanofi halts amlitelimab in atopic dermatitis and itepekimab in COPD after disappointing trial data, leaving no internal successor to Dupixent.

Scenarios

1

REGN20423 reaches late-stage testing, unlocking a $1 billion milestone

Possible Resolves by End of 2027

Discussed by: Reuters, Barclays analysts

REGN20423, the IL-13 antibody in Phase 1 for atopic dermatitis, is the most advanced of the four programs. Regeneron becomes eligible for the first $1 billion milestone when it enters late-stage trials. Positive early data would validate the long-acting approach and point to a viable Dupixent successor.

2

Sanofi's new Dupixent successors fail in trials

Possible Resolves by End of 2029

Discussed by: Guggenheim analysts, Fierce Biotech

The assets are early-stage: REGN20423 is only in Phase 1 and the other three are preclinical, so none has yet shown safety or efficacy in patients. Amlitelimab and itepekimab failed the same way. If these programs stall, Sanofi approaches the 2031 patent cliff without a replacement.

3

Dupixent's patent web holds, softening the 2031 cliff

Uncertain Resolves by End of 2031

Discussed by: Roy Papatheodorou (Sanofi general counsel)

Sanofi argues the 2031 expiry covers only one key patent and that a web of others extends to 2045. If that web holds up to legal challenge, biosimilar competition arrives later and the pressure to replace Dupixent eases. Broader protection would reduce the urgency of the new antibody programs.

Historical Context

2 moments from history that rhyme with this story — and how they unfolded.

January 2023

AbbVie's Humira patent cliff (2023)

AbbVie's Humira, long the world's top-selling drug with peak annual sales near $21 billion, lost US exclusivity in January 2023 as the first biosimilars launched following years of patent settlements. AbbVie had spent years building successors Rinvoq and Skyrizi.

Then

Biosimilars quickly took share, but Rinvoq and Skyrizi grew fast, reaching combined annual sales above $10 billion by 2024.

Now

Demonstrated that a successor strategy can work if replacements are ready years before the cliff.

Why this matters now

Shows the playbook Sanofi is attempting: build next-generation replacements for the same diseases before the patent expires.

2015–2016

Sanofi's Lantus patent loss (2015–2016)

Lantus, Sanofi's insulin blockbuster that peaked around $8 billion in annual sales, lost European exclusivity in 2015 and faced US biosimilar competition from Basaglar in 2016. Sanofi launched follow-on Toujeo, which never matched Lantus's peak.

Then

Lantus sales fell steadily as biosimilars took share, and Toujeo captured only a fraction of the lost revenue.

Now

Left a cautionary example inside Sanofi of what a patent cliff without a successor looks like.

Why this matters now

This is Sanofi's own history with a failed handoff—the risk it is now trying to avoid with Dupixent.

Sources

(10)