Brepocitinib

Brepocitinib (PF-06700841) is a potent dual Janus kinase 1 (JAK1) and TYK2 inhibitor with IC₅₀s of 17 nM and 23 nM, respectively. Brepocitinib also inhibits JAK2 and JAK3 with IC₅₀s of 77 nM and 6.49 μM, respectively^[1]. IC50 & Target: IC50: 17 nM (JAK1), 23 nM (TYK2)^[1] In Vitro: Brepocitinib (PF-06700841; Compound 23) potently inhibits TYK2/JAK2 mediated IL-12/pSTAT4 and IL-23/pSTAT3 (human whole blood (HWB) IC₅₀s of 65 and 120 nM, respectively)^[1].
Brepocitinib has good potency against IL6/pStat1 in the CD3⁺ cellular subset (IC₅₀ of 81 nM), but lower inhibition of IL6/pSTAT3, again in the CD3⁺ cellular subset (IC₅₀ of 641 nM)^[1].
Brepocitinib also inhibits the JAK1/JAK3 driven γ-common chain cytokines, represented by IL-15/pStat5 and IL-21/pSTAT3 with reasonable potency (HWB IC₅₀s of 238 and 204 nM, respectively)^[1].
Brepocitinib inhibits EPO/pSTAT5 (JAK2 homodimer) in HWB spiked with CD34⁺ progenitor cells (IC₅₀ of 577 nM). IL10/pSTAT3 (TYK2/JAK1) and IL27/pSTAT3 (JAK1/JAK2/TYK2) are also inhibited by Brepocitinib with IC₅₀s of 305 nM and 86 nM, respectively^[1].
In Vivo: Brepocitinib (PF-06700841; Compound 23; 3-30 mg/kg; oral administration; for 7 consecutive days; female Lewis rats) treatment significantly reduces paw volume increase in a dose-dependent manner. The plasma concentrations in animals dosed with Brepocitinib at peak (30 min) and trough (24 h) time intervals post final dose respectively are as follows: 3 mg/kg, 3.54 μM, 0.0221 μM; 10 mg/kg, 10.95 μM, 0.06 μM; and 30 mg/kg, 23.89 μM, 0.06 μM^[1].