Bradley Sheares, a former high-ranking executive at Merck ( MRK), has been named CEO of Reliant Pharmaceuticals, a privately held drug company in Liberty Corner, N.J.

Sheares, 49, succeeds Ernest Mario, who has been chairman and CEO since 2003. Mario remains chairman, and Sheares also will become a director.

Reliant sells several heart-disease related drugs, including treatments for high blood pressure and irregular heartbeat, as well as an ulcer medication.

Sheares had been president of Merck's human health business, and analysts had speculated that he was on a short list of potential successors to former Merck CEO Raymond Gilmartin, who was approaching retirement in early 2006.

But when Gilmartin was eased out in May 2005, Merck's directors chose Richard Clark instead . Clark, a long-time Merck employee, had been president of the drug giant's manufacturing division.

Sheares left Merck in July 2006. He joined Merck in 1987 as a research fellow in the Merck Research Laboratories.