The effect of patent expiration on sales of branded competitor drugs in a therapeutic class

Abstract

Background Generic entry can lower pharmaceutical prices and yield significant cost savings for both patients and health systems. The effect of generic entry has often been measured by sales of the branded drug whose patent has expired, but what is less clear is how branded competitors within the same therapeutic class respond. Methods We analyzed the effect of patent expiration of the first innovative drug in a therapeutic class on competitor sales within the same therapeutic class for five major therapeutic classes using data obtained from IMS Health. Results Composite quantity sales decreased by 49%, 65%, and 67% in the first three years, respectively, following patent expiration. However, the effect of patent expiration was not uniformly negative; competitors were often able to obtain dominant market share. Additionally, factors beyond patent expiration may affect the rate and timing of branded market contraction which holds significant implications for drug pricing and sales. Conclusion Patent expiration is a consequential event for not only the drug undergoing patent expiration, but also the therapeutic class in which the drug is contained. Market dynamics change significantly for competitor-branded products which warrant further research.