Background Multiple switches (transitions) between biosimilars of the same reference biologic are now a reality, and they are expected to become more common in the future as more biosimilars enter the market. Switching between two biosimilars of the same reference biologic is generally driven by affordability, formulary requirements, or the relocation/travel of the patient. Evidence of whether switching between biosimilars of the same reference biologic provides similar safety and efficacy profiles is reviewed here. Methods A systematic search was undertaken using electronic databases (to December 2021): Biosis, Embase, MEDLINE, and EBM Reviews/Cochrane Database of Systematic Reviews via Ovid. Publications were evaluated for effectiveness and/ or safety data linked to switching from one biosimilar to another. ResultsThe systematic search yielded 982 citations. After eliminating duplicates, 626 citations remained for the initial title/ abstract screening phase. Following the initial screening, 240 records were chosen; more thorough examination yielded 35 citations. After comprehensive screening and expert advice, 23 studies were selected, of which 13 were published in peerreviewed journals; the remainder have been published as abstracts. Overall, 3657 patients were included in these studies. All studies were observational in nature; no randomized clinical trials were identified. The studies were heterogeneous in size, design, and endpoints. Across the studies, data are provided on safety, effectiveness, immunogenicity, pharmacokinetics, patient retention, patient and physician perceptions, and drug-use patterns. The majority of studies examined switches between biosimilar infliximabs, although switches between biosimilar adalimumabs, etanercepts, and rituximabs were also identified. Two use-pattern studies and one case report were also detected and are discussed. Conclusion Within the limitations of this systematic review, available data suggests that biosimilar-to-biosimilar switching is a safe and effective clinical practice, although it is not covered by current health authority regulations or guidance. No reduction in effectiveness or increase in adverse events was detected in biosimilar-to-biosimilar switching studies conducted to date.

IV and SC bortezomib respectively. ConClusions: SC bortezomib resulted in a significant savings in drug delivery resources. However, drug wastage remained an important factor, regardless of the route of administration.