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Very few patients switch off a biosimilar due to adverse effects, according to a new study.
Switching back from a biosimilar to its reference biologic product was not only rare among a cohort of Veterans Affairs patients, but investigators observed that there were no distinct trends of rationale as to why a patient would switch back.
In new data from an abstract presented at the International Conference on Pharmacoepidemiology and Therapeutic Risk Management (ICPE) Annual Meeting this year, a team of US-based investigators reported data inconclusive to the notion that Veteran patients would primarily switch from a biosimilar product back to its reference biologic product due to a lack of efficacy or safety with the cost-efficient option.
Led by Kelly M. Bryan, of the Veterans Affairs (VA) Center for Medication Center, investigators conducted their pilot study to define and quantify the rationale for switchback to a reference biologic product from a biosimilar among a VA patient cohort. Their research considered the real-world application and outcomes of the nonmedical switching practices, wherein patients stable on reference biologic products are given the opportunity to save on treatment costs with proven biosimilar options that help maintain disease management.
“Switchback to the originator-biologic following nonmedical switching commonly occurs and is often viewed as a signal of biosimilar failure,” they wrote. “However, reason and rate for switchback has not been fully investigated and use of switchback as an effectiveness endpoint in real-world studies may be incorrect. “
Bryan and colleagues observed a cohort of patients in VA who were prescribed ≥1 of 4 reference biologic products between 2019 – 2021: bevacizumab; pegfilgrastim; rituximab; or trastuzumab. The team categorized switching patterns between the reference biologic and biosimilars for each patients, as well as the charting of switchback patterns—which were additionally reviewed to help identify reasoning for switching back to a reference biologic product from its biosimilar.
Patient reasoning for switchbacks were stratified into 5 categories and computed into each of crude, drug-specific and reason-specific rates of switchback.
The final assessment included 18,443 Veteran patients prescribed ≥1 of the 4 identified reference biologic products or 1 of its biosimilars. Among this cohort, 2137 (11.6%) switched to a biosimilar product; of those, just 49 (2.3%) were switched back to a reference biologic—a mean switchback rate of 4.1 per person-year. The drug-specific switchback rate ranged from 3.4 – 9.6 per person-year.
Among the 5 categories of patient- and physician-reported rationale for switchback, “no documented reason” (n = 26) was the leading factor, followed by “erroneous documentation of the switch” (n = 8); adverse drug reaction (n = 5); out of stock of the biosimilar at the VA facility (n = 7); and provider preference for the reference biologic (n = 3).
“Switchback to the originator-biologic was rare among veterans switched to the biosimilar,” investigators wrote. “Lack of a documented reason for the switchback was common, and switchback due to adverse drug reaction was uncommon.”
The team concluded it is difficult to assume that switchback is emblematic of biosimilar treatment failure based on these findings. They noted that future assessments that which include patterns of additional switches between biologics and biosimilars may help better distinguish patient rationale for the strategy.
A pilot evaluation of switchback from biosimilars to originator-biologics in the veterans affairs population: A signal of biosimilar failure? Bryan KM, Her QL, Dong D, Jiang R, et al. Presented at: nternational Conference on Pharmacoepidemiology and Therapeutic Risk Management (ICPE) 2023 Annual Meeting. Halifax, Canada. August 25 – 27, 2023.