A generic drug is the same as a brand name small molecule drug in dosage, safety, strength, how it is taken, quality, performance, and intended use [2]. The study outlines that, in general, generic drugs can receive a period of market exclusivity, and thus the order of market entry impacts market share, with the first product usually having higher uptake than subsequent products. A biosimilar is a biological product (and is therefore larger and undergoes more complex manufacturing processes than a generic) that is highly similar to a US-licensed reference biological product notwithstanding minor differences in clinically inactive components [2]. However, the study highlights that, for non-interchangeable biosimilars, there is no comparable market exclusivity. As such, they investigated other factors that could influence biosimilar uptake, including market order entry, clinical setting, and early publicized pricing discounts.

The team evaluated the uptake of 13 biosimilar products from 3 June 2015 to 1 July 2021, in the US Medicare Fee-for-Service population. They included all first and second marketed biosimilars with at least 12 months of available claims data plus three additional months for reporting lag. This did not include any biosimilars with the interchangeable designation [3]. They determined biosimilar uptake as both an ongoing monthly metric and a cumulative metric for the first year of marketing of each product.

Overall, the team found that biosimilar uptake was widely varied. Of the products marketed longest, filgrastim-sndz accounted for over 50% of monthly filgrastim administrations, whereas infliximab-dyyb accounted for just ~10% of monthly infliximab administrations. Infliximab and epoetin alfa biosimilars both had market shares of under 1% after 12 months of marketing. In addition, the first filgrastim, trastuzumab and bevacizumab biosimilars had higher uptake than the second, conversely the second pegfilgrastim and rituximab biosimilars had higher uptake than the first. For the latter two examples here, when it came to initial pricing discounts, that for the second pegfilgrastim biosimilar was the same as for the first; while for rituximab, the discount of the second rituximab was higher than the first.

In terms of care setting, there were fewer outpatient hospital administrations of the first pegfilgrastim, trastuzumab and bevacizumab biosimilars compared to the second. However, for filgrastim and rituximab biosimilars there were more for the first than for the second.

Overall, the study found that biosimilar uptake was generally lower than that reported for generic drugs. Between 2013 and 2014, generics that entered the market took 88% of it within the first year, this compares to just 33% for biosimilars. There were also no clear patterns affecting biosimilar uptake levels. The team conclude by suggesting that further study is needed to understand the factors affecting biosimilar uptake to increase access to these lifesaving biological products.

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References
1. Kozlowski S, Flowers N, Kwist A, et al. Uptake and competition among biosimilar biological products in the us medicare fee-for-service population. J Gen Intern Med. https://link.springer.com/content/pdf/10.1007/s11606-022-07670-7.pdf
2. GaBI Online - Generics and Biosimilars Initiative. FDA definitions of generics and biosimilars [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2022 Jun 24]. Available from: www.gabionline.net/biosimilars/general/FDA-definitions-of-generics-and-biosimilars
3. GaBI Online - Generics and Biosimilars Initiative. FDA approves first interchangeable insulin glargine biosimilar [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2022 Jun 24]. Available from: www.gabionline.net/es/biosimilares/novedades/fda-approves-first-interchangeable-insulin-glargine-biosimilar

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