Valeant Pharmaceuticals’ chairman and chief executive officer J. Michael Pearson will be on a medical leave of absence, effective immediately. Mr. Pearson was recently hospitalized and treated for a severe case of pneumonia. Robert Chai-Onn, executive vice president and general counsel, Dr. Ari Kellen, executive vice president and group chairman, and Robert Rosiello, executive vice president and chief financial officer, will fill the role during his absence.  The board of directors has als...