Sanofi → Aventis
Sanofi-Synthélabo's takeover of Aventis, a company twice its size by sales, began as a hostile bid in January 2004 and ended that April as an agreed offer of €54.5bn, about $65.5bn, creating the world's third-largest drugmaker after the French government steered Aventis away from Novartis.
Began as a hostile bid and settled at €54.5bn after the French government opposed a rival approach by Novartis.
- Value
- $65B
- Announced
- January 2004
- Completed
- August 2004
- Sector
- Pharma
- Deal type
- acquisition
- Acquirer
- Sanofi (France)
- Target
- Aventis (France)
Why it mattered
Aventis was itself the product of the 1999 merger of France's Rhône-Poulenc and Germany's Hoechst Marion Roussel, based near Strasbourg; in 2003 it had sales of €17.8bn against Sanofi-Synthélabo's €8.0bn. Sanofi-Synthélabo, whose main shareholders were Total and L'Oréal, depended heavily on the blood thinner Plavix, whose patents were one of the deal's biggest risks.
The hostile cash-and-share bid of 26 January 2004 valued Aventis at €47.8bn. Aventis rejected it, adopted poison-pill measures, sued Sanofi in France and the United States, warned that a US patent challenge to Plavix was a time bomb and invited Novartis to talk as a white knight. The government wanted what it called a "local solution": the prime minister, Jean-Pierre Raffarin, said a Sanofi–Aventis tie-up was in the "national interest", the finance minister, Nicolas Sarkozy, pressed Sanofi's chief executive, Jean-François Dehecq, to raise his offer, and the government rejected the poison pill. Novartis withdrew, citing "the strong intervention of the French government".
The agreed offer of 25 April 2004 came with a board split eight–eight between the two sides under Dehecq as chairman and chief executive. To meet competition concerns it sold Arixtra and Fraxiparine to GlaxoSmithKline and Campto to Pfizer, and the European Commission asked for further disposals or licences. The offers settled on 20 August 2004 with 95.47% of Aventis tendered, Sanofi-Synthélabo became Sanofi-Aventis, and the cash portion was financed with new debt.
What it left behind
The Plavix risk was contained: Apotex's US patent challenge failed on its third appeal in 2011, leaving it to pay about $442m in damages. The group dropped "-Aventis" from its name in May 2011, the year it bought Genzyme for about $20.1bn, and in April 2025 sold control of its consumer health arm, Opella, to Clayton, Dubilier & Rice for about €10bn of net cash. Dupixent, which alone accounted for €15.7bn of Sanofi's €43.6bn of sales in 2025, was co-developed with Regeneron, a partner Aventis first signed in 2003. A government that picks a winner can remove a rival bidder faster than any poison pill: once Paris backed a "local solution", Aventis's defence had no one to turn to.