Tofacitinib is a JAK3/2/1 inhibitor with IC50s of 1, 20, and 112 nM, respectively.
Description :
Tofacitinib (CP-690550) is a potent, specific, orally active inhibitor of JAK3 with IC50 of 1 nM in cell-free assays; displays 20- to 100-fold less potency for JAK2 and JAK1 (IC50=20 nM and 112 nM, respectively), and shows no potent activity against 30 other kinases at >3 uM (CaMK1, ROCK2, Lck, MST2, etc.); effectively inhibits a murine mixed lymphocyte reaction (MLR) with IC50 of 91 nM, significantly prolonges survival in a murine model of heart transplantation and in cynomolgus monkeys receiving kidney transplants.
Rheumatoid Arthritis
Tofacitinib citrate inhibits IL-2-mediated human T cell blast proliferation and IL-15-induced CD69 expression with IC50 of 11 nM and 48 nM, respectively. Tofacitinib citrate prevents mixed lymphocyte reaction with IC50 of 87 nM. Tofacitinib citrate treatment of murine factor-dependent cell Patersen–erythropoietin receptor (FDCP-EpoR) cells harboring human wild-type or V617F JAK2 leads to prevention of cell proliferation with IC50 of 2.1 µM and 0.25 µM, respectively. Tofacitinib citrate inhibits interleukin-6-induced phosphorylation of STAT1 and STAT3 with IC50 of 23 nM and 77 nM, respectively. Moreover, Tofacitinib citrate generates a significant pro-apoptotic effect on murine FDCP-EpoR cells carrying JAK2VV617F, whereas a lesser effect is observed for cells carrying wild-type JAK2. This activity is coupled with the inhibition of phosphorylation of the key JAK2V617F-dependent downstream signaling effectors signal transducer and activator of transcription (STAT)3, STAT5, and v-akt murine thymoma viral oncogene homolog (AKT). [2] Additionally, Tofacitinib citrate prevents IL-15-induced CD69 expression in human and cynomolgus monkey NK and CD8+ T cells in vitro. [3]
Animals that are treated with Tofacitinib show a significantly lower production of anti-drug antibodies (ADAs) compare with PEG-treated control mice (for five weeks after initial immunization, p<0.01, n=8). Moreover ADAs become detectable earliest on day 28. A difference of 1000- to 200-fold in titers to SS1P is apparent from days 21 through 35, respectively. Compare to SS1P, mice injected with keyhole limpet hemocyanin (KLH) generate a more rapid antibody response. Yet, the administration of Tofacitinib reduces anti-KLH titers compare to controls (p<0.05 on day 21, p<0.01 on day 28, respectively, n=5). Reductions in titers ranged from 5000- to 250-fold from days 21 through 28, respectively[2]. Based on previous dose-response studies, a daily dose of Tofacitinib of 6.2 mg/kg is selected to provide 80% inhibition of hind paw volume and plasma exposure capable of suppressing the JAK1 and JAK3 signaling pathways for >4 hours[3].