Sanofi-Aventis SA, the world’s third-largest pharmaceuticals company, said Monday it bought a 25 percent stake in Czech drugmaker Zentiva for 430 million euros, or about $515 million.

Sanofi bought the stake from investment firm Warburg Pincus and Zentiva employees, becoming the largest shareholder in the Prague-based company, which develops, manufactures and markets low-cost pharmaceutical products.