Poseltinib

Poseltinib is an irreversible inhibitor of Bruton's tyrosine kinase (BTK; IC₅₀ = 1.95 nM).¹ It is selective for BTK over a panel of 85 additional kinases at 2 µM but does inhibit the other Tec family kinases bone marrow tyrosine kinase on chromosome X (BMX), Tec, and TXK (IC₅₀s = 0.64, 4.57, and 4.62 nM, respectively), as well as EGFR, Blk, and JAK3 (IC₅₀s = 4.96, 13.5, and 14.6 nM, respectively). Poseltinib decreases the levels of CD40, CD69, or CD86 on primary human B cells activated with anti-IgM F(ab’)₂ (IC₅₀s = 4.2, 4.2, and 7.7 nM, respectively). It reduces the differentiation of isolated human CD14⁺ monocytes into osteoclasts when used at a concentration of 1 µM. Poseltinib (10 and 30 mg/kg) decreases disease severity and bone erosion in a mouse model of collagen-induced arthritis.

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1. Park, J.K., Byun, J.-Y., Park, J.A., et al. HM71224, a novel Bruton’s tyrosine kinase inhibitor, suppresses B cell and monocyte activation and ameliorates arthritis in a mouse model: A potential drug for rheumatoid arthritis. Arthritis Res. Ther. 18:91, 1-9 (2016).