Switching from Originator Tocilizumab to Biosimilar in Giant Cell Arteritis: Evaluation of Effectiveness and Safety in a Multicenter Cohort of 38 Patients.

Tocilizumab (TCZ) is an interleukin-6 receptor inhibitor approved for the treatment of giant cell arteritis (GCA). Biosimilars of TCZ, such as TYENNE™, are biologic agents which are similar to the originator (RoACTEMRA™) in structure, efficacy, and safety. Many indications, including GCA, are extrapolated from pivotal trials in rheumatoid arthritis (RA), supported by pharmacological similarity and immunogenicity data. The objective was to evaluate the effectiveness and safety of switching from originator TCZ (RoACTEMRA™) to biosimilar TCZ (TYENNE™) in patients with GCA managed in routine clinical practice. This observational, retrospective, multicenter, real-world study included patients with GCA who switched from RoACTEMRA™ to TYENNE™. Outcomes assessed included clinical and laboratory parameters of disease activity, complete remission, glucocorticoid burden, and safety profile. Comparisons were performed at baseline, 3 months, and 6 months. Linear mixed models and mixed-effects logistic regression were used to assess differences across follow-up visits. A total of 38 patients (68.4% female; mean age 74.1 years) were included. GCA phenotypes comprised cranial (n = 14; 36.8%), extracranial (n = 14; 36.8%), and mixed presentation (n = 10; 26.3%). Prior exposure to RoACTEMRA™ averaged 36.3 ± 28.4 months. Subcutaneous TCZ was administered in 32 patients (84.2%), while 6 received intravenous therapy. At the time of switch, 92.1% were clinically asymptomatic and 81.6% met criteria for complete remission. TYENNE™ was used as monotherapy in 34 patients (89.5%) and in combination with methotrexate in 4 patients (10.5%). Treatment regimens were preserved in all but one patient who was receiving originator TCZ at a dose of 4 mg/kg every 6 weeks, in whom the dosing interval was spaced from 6 to 8 weeks. After a mean follow-up of 8.2 ± 3.1 months, no significant differences were found in complete remission rates, daily prednisone dose, or inflammatory markers respect to baseline. Retention of biosimilar TCZ was 94.7%. TCZ dosing intervals were extended in four patients (10.5%), and treatment was discontinued in one patient owing to sustained remission. No disease relapses occurred. One patient developed herpes zoster, and another discontinued biosimilar TCZ following diagnosis of diverticulosis. Switching from originator TCZ (RoACTEMRA™) to biosimilar TCZ (TYENNE™) appears to be safe and effective in patients with GCA in routine clinical practice.