According to the Associated Press, Pfizer Inc., confirmed that one patient who was taking its drug candidate tofacitinib, a pill designed to treat rheumatoid arthritis, died during a recent clinical trial and said the death was connected to the drug. The world''s largest drugmaker said the patient died of respiratory failure. Three other patients who were treated with tofacitinib during the study died as well, but those deaths were not determined to be drug-related. Two of those deaths occurred several weeks after the patients stopped taking tofacitinib. Tofacitinib, formerly called tasocitinib, is being tested as a treatment for moderate to severe rheumatoid arthritis, a chronic autoimmune disease that causes inflammation, usually of the hands and feet. More than 1,000 patients have taken tofacitinib during clinical trials.