The latest bad news concerns one more of the ill-fated thiazolidinediones (TZDs). This class of drugs was introduced in the late 1990s, and includes Avandia, Actos, and Rezulin. TZDs are PPAR-gamma agonists, meaning that they activate peroxisome proliferator-activated receptors, especially the “gamma” receptor. Such activation affects certain metabolic processes, and among other things, insulin resistance is reduced. Rezulin—notoriously fast-tracked by FDA—was withdrawn from the market in 2000, in the wake of scores of liver failures and deaths. Pfizer, the manufacturer, was on the hook for upwards of $750 million in damages. At the time, Dr. Janet Woodcock, director of FDA’s...