Transitioning patients from an originator to a corresponding biosimilar has been extensively studied in both randomized controlled trials and observational studies. Although transitioning is considered well-tolerated, with no negative impacts on efficacy and/or safety, 2.6-25.8% of patients restart treatment with the originator (retransitioning). Retransitioning to the originator can be considered an indication of biosimilar treatment failure or dissatisfaction with biosimilar treatment. Increasing our knowledge of patients who retransition might help to reduce the number of patients retransitioning.
Our objective was to estimate the cumulative incidence of patients who retransitioned from a tumor necrosis factor (TNF)-α inhibitor biosimilar to originator and to explore potential patient, disease, and treatment and implementation strategy factors associated with retransitioning.
We conducted a systematic literature search in the PubMed, EMBASE, and Cochrane Central Register of controlled trials databases until March 2021. Studies on TNFα inhibitors, biosimilar transitioning, and retransitioning were included. Transitioning was defined as switching from an originator to a biosimilar, and retransitioning was defined as switching from an originator to a biosimilar and back to the originator. Characteristics of the studies were descriptively analyzed. Studies were weighted by the number of patients transitioning, and the primary outcome was the median cumulative incidence of retransitioning. For each of the factors related to patient, disease, and treatment and implementation strategy, studies were stratified according to the categories of that factor. The weighted medians and interquartile ranges (IQRs) of the cumulative incidence of retransitioning in these studies were calculated and compared to explore whether a potential association existed between these factors and the cumulative incidence of retransitioning.
Of 994 screened publications, 37 were included. The weighted median cumulative incidence of retransitioning was 7.6% (IQR 6.8-17.2). Studies that included only patients with inflammatory bowel disease (6.6 vs. 15.1-17.7% for other indications), included only patients with stable disease (7.0 vs. 13.7% for including all patients), and did not offer retransitioning at the introduction of the biosimilar (7.0 vs. 11.1% for studies that offered retransitioning) reported less retransitioning. In addition, the incidence of retransitioning was lower when extra laboratory monitoring was part of the implementation strategy (1.6 vs. 6.1%) and when gainsharing (patients' healthcare directly benefits from financial savings from transitioning) (1.4 vs. 7.2% for studies without gainsharing) was applied.
In studies on transitioning patients from TNFα originator to biosimilar, 8% of patients retransitioned. Retransitioning appeared to be lower in studies that included only patients with stable disease and in studies that did not offer patients the option of retransitioning at the introduction of the biosimilar. In addition, retransitioning appeared to be lower in studies that implemented extra laboratory monitoring as part of the biosimilar implementation strategy. Clinicians should consider implementing these suggestions as they might reduce retransitioning rates and improve the introduction of biosimilars in clinical practice. PROSPERO registration ID: CRD42021226381.