Background/Purpose: Biosimilars of originator biologic therapeutics are entering the market, and health care professionals and patients need a clear understanding of these new treatments. The advantage of biosimilars is the greater patient access which will follow the probable lower costs, although financial savings will vary between regions. With lower costs, switching from originators to biosimilars will probably be considered. However, clinical and real-word data on the effects of switching are currently limited to transition studies of approved biosimilars. This constitutes a gap in our understanding of the switching process (both originator→biosimilar and between different biosimilars). This study was carried out to summarize the current literature on switching.

Methods: A MEDLINE/Web of Science search identified studies where healthy volunteers or patients receiving infliximab (INF), etanercept (ETN), adalimumab (ADA), or rituximab (RTX) switched between originator biologics and biosimilars.

Results: Switching data was available for 12 studies in rheumatic diseases (Table): INF/CT-P13 (4^1-4), INF/SB2 (1⁵), INF/unidentified biosimilar (2^6,7), ETN/SB4 (2^8,9), ETN/GP2015 (1¹⁰), ADA/SB5 (1¹¹), and RTX/CT-P10 (1¹²). The INF/CT-P13 studies showed efficacy and safety of INF and CT-P13 to be similar in switch and maintenance groups, and similar pre- and post-switch. Immunogenicity was assessed in 3 studies and did not change post-switch. In the INF/SB2 study, switch and maintenance groups had similar safety, efficacy, and immunogenicity profiles; comparisons pre- and post-switch were not made. The other 2 INF/biosimilar switch studies showed no difference in efficacy or safety 6 months post-switch. The ETN/SB4 and ETN/GP2015 Phase 1 studies showed similar PK parameters for ETN and the 2 biosimilars. In patients with RA, similar safety, efficacy, and immunogenicity profiles were seen between ETN/SB4 (switch) and SB4/SB4 (maintenance) groups. The ADA/SB5 study showed clinical measures of efficacy, safety, and immunogenicity to be similar in the switch and maintenance groups; comparisons pre- and post-switch were not made. The RTX/CT-P10 study showed clinical measures of efficacy and safety to be similar in the switch and maintenance groups. Efficacy pre- and post-switch could not be compared.  

Conclusion: Switching data is starting to become available; mostly with INF but also emerging for other drugs. The one-way switch (originator→biosimilar) with observations ranging from 24 to 56 weeks seems to be the typical design. While initial transition data confirm maintenance of efficacy and safety, additional data from clinical and real-world switching studies, especially of switching between biosimilars, are required, as is continuing pharmacovigilance. Any switching should remain a clinical decision made jointly by the treating physician and patient on an individual patient basis supported by scientific evidence.