Sanofi's origins trace to December 20, 1973, when the company was founded as a subsidiary of Elf Aquitaine, a French state-owned oil company seeking to diversify into recession-resistant industries. Jean-François Dehecq and René Sautier, two Elf executives, established Sanofi with a clear mandate: acquire fragmented pharmaceutical laboratories across France and build a consolidated European pharmaceutical group. The name 'Sanofi' derived from an anagram of the company's original research subsidiary, reflecting its scientific aspirations. The early business model was straightforward—a 'buy and build' investment vehicle financed entirely by Elf's capital reserves, without external seed funding. The first major acquisition was Labaz, which provided initial product lines and R&D capabilities. Within two years, Sanofi had integrated over ten small laboratories, overcoming skepticism from the medical establishment and establishing a culture of growth through acquisition. In 1980, Sanofi acquired the Clin-Midy group, significantly expanding its R&D capabilities and therapeutic breadth. The 1994 acquisition of Sterling Winthrop's prescription drug business provided critical US market access, establishing the transatlantic footprint that would prove essential for future growth. A pivotal moment came in 1999 when Sanofi merged with Synthélabo—another French pharmaceutical company with roots dating to 1970 and majority-owned by L'Oréal—to form Sanofi-Synthélabo. This merger consolidated French pharmaceutical research and commercial strengths, creating a company with the scale to compete globally. Elf Aquitaine and L'Oréal retained significant stakes, providing financial stability while the new entity focused on pharmaceutical R&D and marketing. The profitable cosmetics business, including luxury brands such as Yves Saint Laurent, was sold to concentrate purely on pharmaceuticals. The defining transaction in Sanofi's history occurred in 2004 when Sanofi-Synthélabo launched a hostile takeover of Aventis, its larger domestic rival. The bid was prompted by a proposed offer for Aventis by Swiss firm Novartis, which threatened to remove a major French pharmaceutical company from national control. The French government actively supported Sanofi's bid, seeking to maintain a pharmaceutical industry leader within France. After months of negotiations, Sanofi-Synthélabo acquired Aventis for approximately $59.4 billion, creating Sanofi-Aventis and instantly becoming one of Europe's largest pharmaceutical companies. The merger integrated Aventis's strong presence in diabetes (Lantus), oncology (Taxotere), and vaccines (Aventis Pasteur), creating a diversified healthcare giant. In 2011, Sanofi-Aventis acquired Genzyme Corporation for approximately $20.1 billion, a transformative transaction that pivoted the company toward rare diseases and biotechnology. Genzyme's enzyme replacement therapies for lysosomal storage diseases—Fabrazyme for Fabry, Cerezyme for Gaucher, and Myozyme for Pompe—became cornerstone products, while the acquisition established Sanofi as a global leader in rare diseases. The Genzyme integration also brought manufacturing expertise in complex biologics that would prove critical for future pipeline assets. In 2017, Sanofi acquired Bioverativ for approximately $11.6 billion and Ablynx for approximately $4.8 billion, further strengthening its hematology and rare blood disorder franchises. Bioverativ added hemophilia therapies Eloctate and Alprolix, while Ablynx brought Nanobody technology and caplacizumab for acquired thrombotic thrombocytopenic purpura. The 2019 appointment of Paul Hudson as CEO marked a strategic inflection point. Hudson, previously at AstraZeneca, launched the 'Play to Win' strategy that prioritized immunology, rare diseases, and vaccines while planning the separation of non-core businesses. The 2024 announcement of Opella's separation and the 2025 acceleration of business development activity represent the culmination of this multi-year transformation.