Veterans’ Experience With Infliximab Biosimilars for IBD Treatment

A study of the Veterans Health Administration (VHA) detailed their experience with infliximab biosimilars in a population of patients with inflammatory bowel disease (IBD) who were naive to infliximab.

It took approximately 6 months for the biosimilar infliximab-dyyb (Inflectra) to become the predominant infliximab product for the IBD population after it was added to the Veterans Affairs National Formulary (VANF) in May 2017. In September 2018, infliximab-abda (Renflexis) became the VANF infliximab product, and was rapidly adopted. According to the authors, the rapid adoption of infliximab-abda “may represent increased comfort due to experience with [infliximab biosimilars] among gastroenterologists, accumulating evidence in support of biosimilars, and swift and systematic action by the VHA pharmacy benefit manager to deploy and enforce a VANF compliance initiative.”

Infliximab was the first tumor necrosis factor (TNF)-α inhibitor approved in the US for IBD. The authors noted that although infliximab induces mucosal healing and improves quality of life in patients with IBD, it is expensive, and the introduction of infliximab biosimilars is predicted to reduce costs for the VHA and other health systems. Infliximab-dyyb (Inflectra) was approved by the FDA in April 2016 and infliximab-abda (Renflexis) in April 2017 for all indications of the reference product, and the approval for IBD (Crohn disease and ulcerative colitis) was via extrapolation. Although gastroenterologists were “initially cautious” about biosimilars approved through extrapolation, accumulating research “continues to provide reassuring data that biosimilars are effective, safe, and comparable to reference biologics,” the authors wrote However, they added that most studies have focused on infliximab-dyyb, not infliximab-abda, and few studies have examined real-world utilization of infliximab biosimilars in the VHA.

The descriptive cohort study investigated infliximab utilization patterns in infliximab-naive patients with IBD during their first 365 days of treatment. Using the VHA Corporate Data Warehouse, 1763 patients receiving care in the VHA initiated on an infliximab product between September 2016 and December 2019 were identified and included in the study, 785 receiving the reference product, 441 receiving infliximab-dyyb, and 537 receiving infliximab-adba.

In baseline criteria, there were differences between groups in missing ethnicity data, and in the proportion of former smokers. Among patients initiating infliximab-abda, 42% were former smokers, compared to 33% initiating infliximab-dyyb and 32% initiating the reference product.

Adoption of Infliximab-dyyb Was Slower Than That of Infliximab-abda

Infliximab-dyyb was used for at least half of new infliximab prescriptions by 183 days after addition to the VANF and took 335 days to become the predominant product in the VHA, whereas infliximab-abda became the predominant infliximab product within 90 days.

Differences in product dosing were found between groups, specifically in average accumulative dose (reference product, 3232 mg; infliximab-dyyb, 3204 mg; and infliximab-abda, 3641 mg) and maximum dose (reference product, 576 mg; infliximab-dyyb, 613 mg; and infliximab-abda, 622 mg).

The authors observed differences in measures of adherence and persistence on the index treatment. However, the greater adherence and persistence observed for infliximab-abda compared to infliximab-dyyb and the reference product “appeared to be a result of formulary pressure to switch patients to the current VANF product.” For example, 40% of patients who were not persistent on the reference product and 42% who were not persistent on infliximab-dyyb switched to infliximab-abda. They said that after accounting for switching between infliximab products, “a high proportion” of patients (approximately 60%) who initiated therapy with the reference product or infliximab-dyyb remained on infliximab therapy at the end of the 365-day follow-up period.

No differences in emergency department or inpatient visits were observed between groups, however, there were differences in baseline and follow-up gastroenterologist visits infliximab-abda (3.88; 95% CI, 3.65-4.11), infliximab-dyyb (3.74; 95% CI, 3.50-3.98), and reference infliximab (3.37; 95% CI, 3.19-3.49). These health care utilization measures, including gastroenterologist visits, emergency department visits, and inpatient visits, did not indicate any differences in surveillance patterns, safety, or effectiveness among the groups of infliximab products, the authors said.

There were no differences between groups in IBD-related laboratory measures, including liver function measures, C-reactive protein, fecal calprotectin, lactoferrin, infliximab trough levels, and anti-drug antibodies. However, the authors did note that only 27% to 41% of patients were tested for antidrug antibodies.

The authors concluded that infliximab utilization and laboratory measures were similar between infliximab-abda, infliximab-dyyb, and the reference product in patients receiving care from the VHA for IBD.

Reference

Patel S, Walsh J, Pinnell D, et al. Real-world experience with biosimilar infliximab-adba and infliximab-dyyb among infliximab-naïve patients with inflammatory bowel disease in the Veterans Health Administration. Medicine (Baltimore). 2024;103(37):e39476. doi:10.1097/MD.0000000000039476