CEO Michael Pearson is back at the helm of embattled Canadian pharmaceutical giant Valeant but will no longer chair the board, following his lengthy absence on sick leave, the company said Sunday.The company has endured months of criticism and hits to its share price over drug-pricing and distribution policies. Pearson's return follows his recovery from "severe pneumonia and other complications."The Valeant chief, who was hospitalized in late December, was replaced in the interim by former CFO Howard Schiller, who will remain on the company's board.