Slow growth of use of biosimilar infliximab in a Medicare fee-for-service population suggests lingering hesitancy on the part of gastroenterologists and patients, particularly when it comes to extrapolation to off-label uses, according to a new study.
A recent study comparing usage of the infliximab biosimilar Inflectra (infliximab-dyyb; CT-P13) with that of the originator biologic (Remicade) among Medicare beneficiaries found that use of the biosimilar is increasing even though it accounted for less than 10% of total monthly administrations.
Study data also suggest some beneficiaries are switching from the reference product to the biosimilar. However, analyses by indication and prescribing clinician suggest that patients and physicians may still have concerns about extrapolation to gastrointestinal indications, according to the authors.
The study, published in the Journal of General Internal Medicine, examined the demographics, usage, and uptake patterns of Remicade and Inflectra in the infliximab-eligible Medicare fee-for-service population in the United States from July 2016 to December 2018. “The overall uptake of biosimilar infliximab has been much slower than that of the biosimilar filgrastim, the first biosimilar product to enter the US market,” the authors noted.
The demographics for the populations treated with the reference product and biosimilar were “broadly similar,” with differences by geographical region. Greater percentages of biosimilar-treated patients were found in the Midwest and West, as opposed to greater percentages for the originator in the Northeast and South.
A breakdown of the biosimilar and originator-treated populations by indication determined the biosimilar was administered somewhat less for inflammatory bowel disease (IBD), which encompasses ulcerative colitis (UC) and Crohn disease (CD). Gastrointestinal indications accounted for 22.5% and 25.9% of treatments with the biosimilar and originator, respectively.
The authors said 17.4% and 15.3% of patients treated for CD received the reference drug and biosimilar, respectively. UC accounted for 8.5% and 7.2% of patients on the originator versus the biosimilar.
Analyzing by prescribing clinician, the authors found that gastroenterologists prescribed the biosimilar less often (14%) compared with the reference product (17%), whereas oncologists prescribed the biosimilar more commonly (10.5%) than the reference product (5.5%). Rheumatologists prescribed the biosimilar and reference product in the same proportions (58.2% and 59.9%, respectively).
The authors observed a relative reluctance to prescribe biosimilars for gastrointestinal indications. “There may still be some reservations among certain patients or providers regarding usage of the product for indications extrapolated from the overall conclusion of biosimilarity” between the reference and biosimilar agents, they wrote.
The use of the infliximab biosimilar in CD and UC was originally extrapolated from the demonstration of similarity to the reference product in clinical studies on patients with rheumatoid arthritis (RA). Notably, 55.02% of patients being treated for RA received the biosimilar. The percentage receiving the reference product was 52.24%.
Patients taking the reference product and those taking the biosimilar were more likely to have prior use of the reference product,“which indicates that some beneficiaries are switching from the reference product to the biosimilar,” according to the authors.
The dose patterns across different indications were similar for those using the originator versus the biosimilar. This was notable in CD, where “the label for each product specifies that increasing the dose to 10 mg/kg may benefit patients who have lost their response.” The authors said the similar dose distributions in CD suggest that the “biosimilar has not required more dose escalation than the reference product.”
The authors recommended further study of infliximab biosimilars in IBD, attention to clinicians’ rationale for their prescribing choices, and more effort to educate patients and physicians about biosimilars.
Kozlowski S, Flowers N, Birger N, et al. Uptake and usage patterns of biosimilar infliximab in the Medicare population. J Gen Intern Med. Published online June 23, 2020. doi:10.1007/s11606-020-05957-1