Immunogenicity of sarilumab and impact on safety and efficacy in Japanese patients with rheumatoid arthritis: analysis of two Phase 3 randomised clinical trials

To describe the immunogenicity profile of sarilumab in Japanese patients with rheumatoid arthritis (RA). Patients enrolled in the KAKEHASI and HARUKA studies were included in our analysis. In these studies, patients received sarilumab 150 mg or 200 mg every 2 weeks for 52 or 28 weeks in combination with methotrexate (MTX) (KAKEHASI), or for 52 weeks as monotherapy or in combination with non-MTX conventional synthetic disease-modifying anti-rheumatic drugs (HARUKA). Anti-drug antibodies (ADAs) and neutralising antibodies (NAbs) were assessed in the pooled population. Positive ADA assay responses occurred in 10/149 (7.1%) patients treated with sarilumab 150 mg and 13/185 (7.0%) patients treated with sarilumab 200 mg, with persistent responses in 2 (1.4%) and 4 (2.2%) patients, respectively. Peak ADA titre was 30. No patients treated with the 150 mg dose and one patient (0.5%) treated with the 200 mg dose exhibited NAbs. There was no evidence of an association between ADA formation and hypersensitivity reactions or reduced efficacy. ADAs, which occurred at a low frequency and titre, did not affect the safety or efficacy of sarilumab 150 or 200 mg administered as monotherapy or combination therapy in Japanese patients with RA in the KAKEHASI or HARUKA studies.