Truveta study finds 16% of adalimumab biosimilar switchers revert

Truveta, a health data company backed by a consortium of US health systems, has published a real-world study showing that while formulary changes drove a significant uptick in adalimumab biosimilar adoption, roughly one in six patients who made the initial switch subsequently returned to the originator product, Humira.

The retrospective cohort study, published in the Journal of Managed Care and Specialty Pharmacy, analysed electronic health record data from 67,594 adults treated with originator adalimumab between February 2023 and August 2025. Of those patients, 17.7% switched to a biosimilar during the observation window, with the transition rate peaking in April 2024 following major formulary updates by US health plans. Among switchers with sufficient follow-up data, 16.0% subsequently reverted to the originator.

Who is switching back and why

The study identified several patient characteristics associated with higher switch-back rates. Older adults, women, and patients with ankylosing spondylitis were significantly more likely to return to Humira, while patients in rural areas tended to revert more quickly after initiating a biosimilar. The release did not specify whether switch-backs were driven by clinical factors such as perceived efficacy or tolerability concerns, administrative barriers, or prescriber preference, though these are the variables that payers and clinicians will want to disentangle in follow-on analysis.

Karen Gilbert Farrar, Senior Research Analyst at Truveta and lead author of the study, said: "Understanding which patients are more likely to switch back and when those switch-backs occur can help clinicians and health plans better support patients during biosimilar transitions and strengthen confidence in these therapies."

Adalimumab is among the highest-volume biologics in the world, indicated across rheumatoid arthritis, Crohn's disease, psoriasis, ulcerative colitis, psoriatic arthritis, and ankylosing spondylitis. Multiple biosimilar versions entered the US market from 2023 onwards, making the adalimumab category one of the most closely watched biosimilar transitions in the history of the American market.

Market and regulatory context

The adalimumab biosimilar landscape is notably crowded. More than ten biosimilar versions have received US approval, from manufacturers including Amgen, Samsung Bioepis, Sandoz and others, competing on price, device format, and formulary position. Payers have used tiering and exclusion strategies to accelerate the shift away from the reference product, whose list price had long made it one of the largest single line items in US drug spend.

Truveta's findings carry relevance beyond adalimumab. Regulators at the FDA and EMA have been keen to build prescriber and patient confidence in interchangeability designations, and real-world switch-back data of this kind feeds directly into that evidence base. The FDA's interchangeability guidance allows pharmacist-level substitution without prescriber intervention, yet the 16% reversion rate suggests that automatic substitution alone does not guarantee sustained uptake. Health plans and integrated care networks will likely use granular sub-group findings to target patient education and monitoring programmes.

Truveta's dataset draws from more than 130 million patients across its member health systems, giving the analysis a scale that positions it as regulatory-grade evidence. Further research disaggregating clinical reasons for reversion from administrative or access-related factors would strengthen the actionability of the results for health plan design.