OBJECTIVES: Value of being first to market has been demonstrated for generic drugs. However, the evidence for first-to-market advantage among biosimilars has been mixed. This study aims to determine whether such an advantage exists for biosimilar markets and its magnitude.

METHODS: We used IQVIA NSP data on monthly U.S. sales of 21 biosimilars and 7 reference biologics from Q3 2015 through Q1 2023 that comprised seven markets: bevacizumab, epoetin alfa, filgrastim, infliximab, pegfilgrastim, rituximab, and trastuzumab. To account for rebates/off-invoice discounts, we used SSR Health and CMS ASP data. We modeled the market share erosion of a typical first biosimilar entrant competing with later market entrants using a modified exponential function. Because of product heterogeneities, we used the median market share at each point in time to fit a trend. For comparison, the market uptakes of later entrants were modeled by pooling the parameters from logistic growth functions.

RESULTS: First entrants achieve a long-run share of 55.1% (p<0.001) of total biosimilar sales in a given market. By comparison, long-run market share is 43.4% for second, 25.1% for third, and 16.9% for fourth or fifth entrants. This differs from generic markets, where the first generic entrant has a market share advantage of 86% over the second generic entrant, according to literature.

CONCLUSIONS: Being the first biosimilar to market has an enduring advantage. Of the total biosimilar sales for a given market, the first entrant’s share is 27.0% higher than the second entrant’s. While the advantage is less by percentage than generic drugs, it may be larger by revenues given the size of biologics markets. This advantage may partially explain the behavior of several biosimilar developers (e.g., Sandoz, Biocon) that have launched at risk before clearing the reference listed drug’s patents.