In the US, a legal framework for approving biosimilars was established in 2009, via the Biologics Price Competition and Innovation Act of 2009 (BPCI Act). The US Food and Drug Administration (FDA) approved its first biosimilar, Zarxio (filgrastim-sndz), in 2015 [3]. To date, FDA has approved 30 biosimilars [4]. However, only nine of these approved biosimilars are on the market.

Biosimilars for rheumatic conditions are relatively new to the US market: Inflectra (infliximab-dyyb) was launched in the US in November 2016 and Renflexis (infliximab‐abda) was launched in July 2017.

The study by Dr Bansback and colleagues evaluates the utilization of anti-TNF biosimilars across rheumatology practices in the US and compares whether patients initiating biosimilars remain on these treatments at least as long as new initiators of originator biologicals.

The authors identified a cohort of patients initiating an anti-TNF biosimilar between January 2017 and September 2018 from an electronic health record registry, the RISE registry, which contained data from 218 rheumatology practices and over one million rheumatology patients in the US. They also identified a cohort of patients who initiated the originator biological anti-TNF during the same period.

The authors calculated the proportion of biosimilar prescriptions compared with other TNF inhibitors and compared persistence on these therapies, adjusting for age, sex, diagnoses codes and insurance type. All subjects were followed until they were either prescribed another biological disease‐modifying anti-rheumatic drug (DMARD) or to their last follow‐up date in the database, whichever came first.

A total of 909 patients were prescribed the biosimilar infliximab-dyyb, Inflectra, the only biosimilar prescribed, and 4,413 patients with a new prescription for the originator infliximab (Johnson & Johnson and Merck’s Remicade).

Patients prescribed a biosimilar tended to be older, have a diagnosis code for rheumatoid arthritis, and be covered by Medicare# insurance. Over the study period, biosimilar prescriptions reached a maximum of 3.5% of all anti-TNF prescriptions, making up 17% of new infliximab‐based prescriptions. Patients persisted on the biosimilar at least as long as the originator infliximab (hazard ratio [HR] 0.83, p = 0.07).

The authors concluded that ‘despite the promise of lower prices and increasing data on the equivalent safety and efficacy from clinical trials the uptake of biosimilars in the United States remains low; nearly 2 years after market entry, only 3.5% among rheumatology practices have participated in the RISE registry’. This is also ‘despite persistence on infliximab-dyyb being similar to the infliximab originator’. They added that ‘these results add to clinical studies’ and that they should further allay ‘concerns over the use of biosimilars’ and ‘provide greater confidence to patients and physicians regarding biosimilar use’.

#Medicare is a national social insurance programme, administered by the US federal government since 1966. It provides health insurance for Americans aged 65 and older who have worked and paid into the system, as well as to younger people with disabilities.

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References
1. GaBI Online - Generics and Biosimilars Initiative. The sluggish US biosimilars market [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2020 Apr 3]. Available from: www.gabionline.net/Reports/The-sluggish-US-biosimilars-market
2. Bansback N, Curtis JR, Huang J, et al. Patterns of tumor necrosis factor inhibitor (TNFi) biosimilar use across United States rheumatology practices. ACR Open Rheumatol. 2020;2(2):79-83. doi:10.1002/acr2.11106
3. GaBI Online - Generics and Biosimilars Initiative. FDA approves its first biosimilar [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2020 Apr 3]. Available from: www.gabionline.net/Biosimilars/News/FDA-approves-its-first-biosimilar
4. GaBI Online - Generics and Biosimilars Initiative. Biosimilars approved in the US [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International [cited 2020 Apr 3]. Available from: www.gabionline.net/Biosimilars/General/Biosimilars-approved-in-the-US

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