Safety and effectiveness of intravenous abatacept for polyarticular-course juvenile idiopathic arthritis: An all-case postmarketing surveillance study.

Background: In 2018, intravenous abatacept was approved for the treatment of refractory polyarticular-course juvenile idiopathic arthritis (JIA) in Japan. However, reports describing the effectiveness and safety of abatacept in clinical practice in Japanese patients with refractory polyarticular-course JIA are limited. Therefore, this postmarketing surveillance study aimed to evaluate the real-world safety and effectiveness of abatacept in Japanese pediatric patients with refractory polyarticular-course JIA.

Methods: This study evaluated patients included in an all-case postmarketing surveillance study between February 2018 and August 2020 who were treated with intravenous abatacept. Data on the safety and effectiveness of the registered patients were collected during the 52-week follow-up period. Disease activities were evaluated using Juvenile Arthritis Disease Activity Score 27 (JADAS-27). The effect of abatacept on a child's growth was assessed using the height and weight standard deviation scores (SDS).

Results: A total of 82 patients were registered in this study, of whom 14.6% and 85.4% were males and females, respectively. The proportion of patients with oligoarticular, rheumatoid factor (RF)-negative polyarticular, and RF-positive polyarticular JIA was 12.2, 28.0, and 54.9%, respectively. The incidence of adverse drug reactions (ADRs) and serious ADRs was 22.0% and 2.4%, respectively. During the study period, 64.7% of the patients achieved JADAS-27 low disease activity or less. A significant difference in JADAS-27 scores in patients with RF-positive polyarticular JIA was observed between baseline and 24 or 52 weeks after abatacept administration. The height and weight SDS tended to improve during abatacept treatment.

Conclusions: Abatacept is effective in polyarticular-course JIA, particularly in RF-positive patients, and in restoring a child's growth. Additionally, the incidence of ADRs is similar to that observed in the clinical trial. The results of the study suggest that abatacept is a useful therapeutic option for treating refractory polyarticular-course JIA in real-world settings in Japan.