AbbVie Inc's arthritis drug Humira and Roche Holding AG's cancer drug Rituxan topped a list of seven treatments whose combined 2017 and 2018 price hikes accounted for a $5.1 billion increase in U.S. spending, a report released on Tuesday showed. The price hikes were more than twice the rate of medical inflation and were not supported by any new clinical evidence, the Institute for Clinical and Economic Review (ICER) said in the analysis. It was the first such annual report by the Boston-based research group, which assesses the cost-effectiveness of drugs. Other top treatments by spending that were called out included Pfizer Inc's pain drug Lyrica, Gilead Sciences Inc's HIV drug Truvada, Amgen Inc's cancer drug Neulasta, Eli Lilly & Co's erectile dysfunction drug Cialis and Biogen Inc's multiple sclerosis treatment Tecfidera. U.S. drug prices are tough to pin down. Companies may provide list prices, but they also negotiate discounts and after-market rebates with purchasers and their representatives such as pharmacy benefit managers, health insurers, employers, and government and state health coverage programs. ICER evaluated the pricing in partnerships with SSR Health Inc, a research firm, which calculated the increases excluding discounts and after-market rebates.