Synthesis and evaluation of hydrazinyl-containing pyrrolo[2,3-d]pyrimidine series as potent, selective and oral JAK1 inhibitors for the treatment of rheumatoid arthritis

Selective inhibition of JAK kinases within the JAK family has been a desired goal of research in order to maximize efficacy while reducing undesired off target effect. Aiming to minimize adverse effects such as anemia, a promising new class of pyrrolo[2,3-d]pyrimidine series containing a hydrazinyl moiety were synthesized and profiled. Among them compound 8m and 8o showed the best enzymatic activity against JAK1 with IC50 value of 0.16 nM and 0.3 nM respectively, and with selectivity over JAK2 by 40.6 and 10 folds respectively. In addition, 8o had an improved PK profile and demonstrated better in vivo efficacy than Tofacitinib in CIA model.