Peficitinib hydrochloride, also known as ASP015K, is an orally active JAK inhibitor compound. It exhibits inhibitory activity against JAK1, JAK2, JAK3, and Tyk2, with IC 50 values of 3.9, 5.0, 0.7, and 4.8 nM, respectively.

Peficitinib hydrobromide (0-100 nM; 3 days) inhibits IL-2-induced T cell proliferation in a concentration-dependent manner [1]. Peficitinib hydrobromide (10-1000 nM) inhibits IL-2-induced STAT5 phosphorylation in a concentration-dependent manner with a mean IC 50 of 124 nM in rat whole blood, and inhibits STAT5 phosphorylation with a mean IC 50 of 127 nM in human lymphocytes [1]. Cell Proliferation Assay [1] Cell Line: Splenocytes from male Lewis rats Concentration: 0-100 nM Incubation Time: 3 days Result: Inhibited IL-2-induced T cell proliferation in a concentration-dependent manner with an IC 50 of 10 nM.

Peficitinib hydrobromide (1-30 mg/kg; p.o.; once daily for 24 days) shows dose-dependent efficacy both in prophylactic and therapeutic dosing regimens in an adjuvant-induced arthritis rat model [1]. Animal Model: Seven-weeks-old female Lewis rats, adjuvant-induced arthritis (AIA) model [1] Dosage: 1, 3, 10, and 30 mg/kg Administration: Oral administration, once daily for 24 days Result: Significantly inhibited the increase in paw volume at doses of 1 mg/kg or greater with an ED 50 value of 2.7 mg/kg (95% confidence interval: 1.5–4.2 mg/kg). Significantly reduced the bone destruction score at 10 mg/kg or greater and almost fully ameliorated both paw swelling and bone destruction scores at 30 mg/kg.