Lack of Penetration of Infliximab Biosimilars: Is This News?

The journal Arthritis & Rheumatism published an article in January explaining that the use of infliximab biosimilars for the treatment of rheumatoid arthritis is “flatlining.” It probably didn’t take a pharmacoeconomist and rheumatologist to understand why this has happened.

Those familiar with the biosimilar environment know well that infliximab biosimilar utilization has been stagnant since the introduction of Inflectra® in 2016. The reasons were quickly apparent: (1) Celltrion and marketing partner Pfizer (and subsequently Samsung Bioepis and marketing partner Merck, with Renflexis®) was undercut by Janssen Biotech’s contracting efforts and (2) the biosimilar manufacturers didn’t keep pace with price cuts attractive enough to sway payers and health system purchasers to move away from the use of Remicade®.

Although this news isn’t really new, the infliximab prescription figures reported by the authors from Brigham and Women’s Hospital in Boston pose an additional interesting viewpoint. Infliximab is still the only anti-TNF agent that is available as a biosimilar, and in their article, they specify that biosimilar infliximab claims made up only 0.9% of all anti-TNF prescription claims in the first quarter of 2019. As reported earlier, IQVIA noted that Inflectra and Renflexis combined attained only an 11% marketshare of US infliximab prescriptions. Pfizer reported about $300 million in 2019 US Inflectra sales, which further supports these figures. It points to the limited inroads made by biosimilars into this autoimmune category.

The authors also state that the overall use of infliximab is stable, based on their database analysis of 1.1 million claims for anti-TNFs associated with 95,906 patients from 2016 to 2019. This doesn’t sound reasonable, as the overall use of infliximab as an infusion faces competition from other anti-TNFs that are available as self-administered injectables and several newer immunologic agents over this period. For example, Cosentyx® utilization has been growing over time, and its share would most likely be at the expense of older drugs like infliximab and etanercept. However, IQVIA data reveal that in RA, anyway, infliximab utilization is not shrinking, but it is only a minor competitor, especially compared with AbbVie’s Humira® and Amgen’s Enbrel®, neither of which are sold in the US as biosimilars (but both of which are in Europe).

Celltrion’s efforts to produce a subcutaneous version of Inflectra may eventually result in greater marketshare, but the utilization of more efficacious interleukin inhibitors and oral JAK inhibitors should erode infliximab utilization overall.

The authors’ study is limited to rheumatoid arthritis. Yet, infliximab’s primary indication is likely still Crohn’s disease. One suspects that this is responsible for much of infliximab’s utilization.

While we await the outcome of Pfizer’s anticompetitive suit against Janssen and its parent Johnson & Johnson, Janssen does report declining infliximab revenues. As pointed out previously, this is due almost exclusively to lower prices demanded by payers for continuing to prefer the agent.

Is it reasonable to say that biosimilar prescriptions are “flatlining”? No, but in the context of this single disease state, they’re not making a lot of progress.

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