About one in 19 generic drugs sold in the U.S. during the past three years have undergone major price hikes that may be consistent with collusion, according to a wide-ranging study that comes in the middle of a sprawling Justice Department investigation into pharmaceutical price-fixing. Fideres Partners LLP, a London-based consultancy that works with law firms to bring litigation against companies, reported “anomalous pricing patterns” in scores of generic drugs sold in the U.S. from 2013 to 2016.