Here's an excerpt from last year's issue of Blood, titled "JAK Blockade and HTLV", describing the effectiveness of JAK inhibition (Tofacitinib / CP690550) not only HTLV infection, but also on rheumatoid arthritis, psoriasis, and prevention of renal transplant
rejection:
Alternatively, paracrine stimulation of IL-9 by HTLV-1 Tax could also promote activation of the IL-9 receptor on monocytes, which in turn stimulates proliferation of HTLV-1infected lymphocytes.6 The current article by Ju and colleagues demonstrates that inhibition of all
3 receptor-mediated pathways prevents proliferation
of HTLV-1infected lymphocytes more effectively than inhibition of any one of the pathways.1 Moreover, because the IL-2, IL-9, and IL-15 receptors all share the use of the common chain (c), inhibition of associated Jak3 proved to be as effective as combined inhibition of all 3 pathways. CP690 550 is a selective Jak3 inhibitor, plus it also inhibits mutant forms of Jak2. Clinical studies are under way in patients with rheumatoid arthritis and psoriasis; other studies will also examine the prevention of renal transplant
rejection. The Jak-Stat pathway may also be constitutively activated in transformed cells due to
gain-of-function mutations. Although Jak2 mutations are common in myeloproliferative disorders, Jak3 mutations have been reported in only a few patients with solid tumors, and have not been identified in ATLL.2,7 Alternatively, the Jak-Stat pathway may be activated
by loss of suppressor of cytokine signaling (SOCS) proteins, E3 ubiquitin ligases that promote the degradation of Jak proteins. HTLV-1 infection overcomes the effects of interferon-induced Jak-Stat activation by
up-regulation of SOCS1. In light of the limited efficacy of current therapies for ATLL and HAM/TSP, the current preclinical results with Jak3targeted
therapy offer a potential new avenue of treatment
for these disorders.