PMS78 - CHANGES IN THE PRICES OF INCUMBENT TNF-ALPHA INHIBITORS FOLLOWING THE MARKET ENTRY OF COMPETITORS

Abstract

Before 2009, etanercept, infliximab and adalimumab were the only tumor necrosis factor alpha (TNF-alpha) inhibitors approved by the US Food and Drug Administration for the treatment of rheumatoid arthritis (RA). Since then, three new therapies have been approved for this indication, including: subcutaneous golimumab in April 2009, certolizumab pegol in May 2009, and intravenous golimumab in July 2013. The objective of this study was to assess how prices of incumbent TNF-alpha inhibitors changed in response to the market entry of new agents. We obtained 2005-2017 monthly wholesale acquisition costs for all TNF-alpha inhibitors approved for RA from Analysource. For each month between January 2005 and January 2017, we calculated the annual cost of treating a standard 80kg/1.80m patient with each drug. We constructed an interrupted time-series analysis with a linear model to test how the entry of new agents affected trends in prices of incumbent products. The linear model regressed the annual cost of treatment against a continuous variable for month, two indicator variables for each period after new drug entry (one for April 2009-July 2013, another for July 2013-end of the study period), and the interactions between each indicator variable and the time variable. After the entry of subcutaneous golimumab and certolizumab pegol, the annual cost of treatment increased a 284% faster, from US$69 every month between January 2005 and April 2009 to US$196 every month between April 2009 and July 2013 (p-value for trend change<0.001). After the entry of intravenous golimumab, the annual cost of treatment increased by US$488 every month between July 2013 and January 2017 (p-value for trend change<0.001), a 249% faster than during the previous period. Although increased competition should theoretically drive prices down, we found that prices of incumbent TNF-alpha inhibitors significantly increased following the entry of new competitors.