Importance: Market exclusivity for daily injections of glatiramer acetate, a disease-modifying therapy for multiple sclerosis, expired in 2015. In 2014, the manufacturer launched an alternate 3-times-weekly version that was widely adopted, sustaining market dominance of brand-name glatiramer until late 2017.
Objective: To estimate excess US spending associated with the transition from daily to 3-times-weekly glatiramer.
Design, setting, and participants: This economic evaluation estimated total US glatiramer spending from January 1, 2011, to June 30, 2019, using a national cohort from 3 data sources that collectively represent approximately 40% of the US glatiramer market: Medicare Part D, Medicaid, and a claims database of commercially insured and Medicare Advantage patients.
Exposures: Calendar quarter.
Main outcomes and measures: Outcomes were quarterly US glatiramer spending, estimated as price × use. Manufacturer list prices for generic products and estimates of net (postrebate) prices for brand-name products were used. Linear regression and interrupted time series models were used to compare spending trends in 3 periods: before generic competition (2011-2015), during generic competition for daily glatiramer (2015-2017), and during generic competition for daily and 3-times-weekly glatiramer (2017-2019).
Results: From 2011 to 2015, US glatiramer spending increased to $962 million per quarter and did not decrease with generic competition of only daily glatiramer (2015-2017). After generic competition began for 3-times-weekly glatiramer in 2017, prices decreased by 47% to 64%, and spending decreased to $508 million per quarter in 2019 (P < .001 for slope). The delay in decreased spending from 2015 to 2017 was associated with excess spending of $4.3 billion to $6.5 billion.
Conclusions and relevance: These findings suggest that 2.5 years of delayed generic competition related to introduction of a new version of branded glatiramer acetate was associated with $4.3 billion to $6.5 billion in excess spending. Extended market exclusivity from introducing a new version of an existing brand-name drug can yield manufacturer returns out of proportion to the level of investment or risk involved; more limited incentives could encourage incremental innovations to existing drugs at a lower societal cost.