Ivarmacitinib sulfate (ivarmacitinib; ®), a selective Janus kinase 1 (JAK1) inhibitor, is being developed by Jiangsu Hengrui Pharmaceuticals Co, Ltd Co, Ltd for the treatment of immune-mediated inflammatory diseases. In March 2025, ivarmacitinib was approved for use in adult patients with active ankylosing spondylitis (AS) who have responded poorly to or are intolerant to ≥ 1 tumour necrosis factor (TNF) inhibitors in China. In March 2025, ivarmacitinib was also approved in China for use in adult patients with moderate to severe active rheumatoid arthritis (RA) who have responded poorly to or are intolerant to ≥ 1 TNF inhibitors. In April 2025, ivarmacitinib was approved in China for use in adult patients with moderate to severe atopic dermatitis (AD) who have had an inadequate response or intolerance to topical or other systemic treatments. This article summarizes the milestones in the development of ivarmacitinib leading to this first approval for the treatment of adult patients with active AS.
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