Garnier served as the Chief Executive Officer of GlaxoSmithKline (GSK) from 2000 to 2008, overseeing the merger of Glaxo Wellcome and SmithKline Beecham. Prior to GSK, Garnier held executive positions at SmithKline Beecham and Schering-Plough.

Garnier has extensive board experience, serving as Chairman of the Board of Actelion (acquired by Johnson & Johnson in 2017 for $30 billion) and as non-executive Chairman at Alzheon (2015-2018), Idorsia (2017-2020), and Carmat (2018-2022). He has also served on the Board of Directors of United Technology (1997-2020), Renault SA (2009-2016), and Radius Health (2015-2022). Garnier is currently Chairman of the Board of Cellectis SA and member of the Board of Directors of Carrier Global Corporation.

He holds a PhD in pharmacology from Louis Pasteur University and an MBA from Stanford University. He is a Knight Commander of the Order of the British Empire and Officier de la Légion d’Honneur of France.