Ben Mooge, Sandoz’s creative partner for nine years, will remain as sole executive creative director.
Sandoz joined Havas in 2014 when the French advertising company bought a majority stake in digital agency Work Club, the shop co-founded by Sandoz in 2007. The deal tied the founders, including Sandoz and Mooge, into a six-year, £30m earn-out period.
The creative duo were appointed joint executive creative directors in 2015 of what was then called Havas Creative Group. Earlier this year, Havas Creative Group and Havas Media Group were brought together under a single P&L led by Dominique Delport, the global managing director.
In a statement, Havas said Sandoz was leaving to pursue "personal projects".
Sandoz said: "Alongside Ben, all the wonderful Work Club / Havas crew and our fantastic clients over the years, it's been a great journey so far. Now a crossroads... #NeverForget."