A week after announcing that he plans to step down as head of Cambridge-based Sanofi Genzyme, David Meeker has been named chairman of the board at a smaller rare disease biotech.

Boston-based Rhythm Pharmaceuticals, a privately-held company that is developing a drug that targets rare genetic disorders linked to obesity, announced Tuesday that Meeker — who has served on the company’s board since 2015 — will now become chairman.

Meeker is set to leave his post at Sanofi Genzyme, a unit of Sanofi…