according to a new analysis of Medicare claims data and wholesale acquisition costs published online in JAMA Internal Medicine.
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A research team led by Alvaro San-Juan-Rodriguez, PharmD, of the University of Pittsburgh said their analysis illustrates “a market failure contributing to the rising costs of prescription drugs.”
Before 2009, etanercept (Enbrel), infliximab (Remicade), and adalimumab (Humira) were the only tumor necrosis factor (TNF) inhibitors approved by the Food and Drug Administration for treating rheumatoid arthritis; infliximab and adalimumab are also approved to treat inflammatory bowel disease. In 2009, subcutaneous golimumab (Simponi) and certolizumab pegol (Cimzia) entered the market, followed by intravenous golimumab (Simponi ARIA) in 2013.
The researchers used an interrupted time series analysis with a linear model that “regressed the annual cost of existing TNF inhibitors against a continuous variable for month, two indicator variables for each period after market entry of new drugs, and the interactions between them.”
Using estimates from this model, the researchers calculated the trends in costs that would have been expected if new anti-TNFs had not entered the market. They examined costs for TNF inhibitors typically reimbursed under Medicare Part D (Enbrel, Humira, Simponi, and Cimzia) and adjusted the data for increases in manufacturer rebates, but “owing to lack of data,” they could not “assess how purchasing prices for drugs typically reimbursed under Medicare Part B [Remicade and Simponi ARIA] changed over time.” All estimates for annual costs of treatment were based on dosing recommendations for a standard 80-kg patient with rheumatoid arthritis.
The annual treatment costs with existing TNF inhibitors increased after the three new agents entered the market. For example, when wholesale acquisition cost data was applied, annual treatment costs with existing TNF inhibitors increased by 144% from April 2009 to December 2016 after new drug entry (from $15.809 to $38,574). However, in the absence of new drugs’ entry, the researchers estimated that annual treatment costs would have increased by 34% (from $15,809 to $21,184).
Medicare annual treatment costs increased by 139% (from $14,901 to $35,613), compared with a 43% increase expected in the absence of new drugs’ entry (from $14,901 to $21,308). Medicare spending increased in parallel with increases in annual treatment costs, but out-of-pocket costs and manufacturer coverage gap discounts remained relatively constant over time.
The research team noted that if cost trends had not changed after the entry of new products, the costs of Enbrel, Remicade, and Humira in December 2016 would have been 40%-45% lower.
“These increases were born solely by Medicare, while patient out-of-pocket spending remained flat. In addition, these increases were not offset by manufacturer discounts in the Medicare Part D coverage gap. The rising costs of existing products may reflect manufacturers’ opportunism in response to payers’ increased willingness to pay for TNF inhibitors after market entry of new, more expensive agents,” the research team noted.
The study was funded in part by the Myers Family Foundation and one author reported funding from the National Heart, Lung, and Blood Institute.
SOURCE: San-Juan-Rodriguez A et al. JAMA Intern Med. 2019 Feb 18. doi: 10.1001/jamainternmed.2018.7656