Sanofi has abruptly replaced CEO Paul Hudson following disappointing returns from a massive R&D investment push. The French pharmaceutical giant appointed Merck KGaA's Belén Garijo to succeed him, signaling a major leadership shift after years of costly research initiatives failed to deliver expected breakthroughs.

Hudson, who led Sanofi since 2019, had championed aggressive spending on drug development to transform the company's pipeline. Despite billions invested in research, the company struggled to bring new products to market quickly enough to satisfy investors. The move comes amid pressure from shareholders frustrated with Sanofi's performance relative to competitors.

Garijo, currently CEO of Merck KGaA, brings extensive pharmaceutical experience to the role. Her appointment suggests Sanofi aims to accelerate innovation and improve execution in its research operations. The leadership change reflects growing impatience in the pharmaceutical industry with lengthy development cycles and high R&D costs that don't translate into commercial success.