The discovery of 2,5-isomers of triazole-pyrrolopyrimidine as selective Janus kinase 2 (JAK2) inhibitors versus JAK1 and JAK3.
Lee SM, Yoon KB, Lee HJ, Kim J, Chung YK, Cho WJ, Mukai C, Choi S, Kang KW, Han SY, Ko H, Kim YC.
Members of the Janus kinase (JAK) family are potential therapeutic targets. Abnormal signaling by mutant JAK2 is related to hematological malignancy, such as myeloproliferative neoplasms (MPNs), and tyrosine kinase inhibitor (TKI)-resistance in non-small cell lung cancer (NSCLC). We discovered a potent and highly selective inhibitor of JAK2 over JAK1 and -3 based on the structure of 4-(2,5-triazole)-pyrrolopyrimidine. Among all triazole compounds tested, 2,5-triazole regioisomers more effectively inhibited JAK2 kinase activity than isomers with substitutions of various alkyl groups at the R<sub>2</sub> position, except for methyl-substituted 1,5-triazole, which was more potent than the corresponding 1,4- and 2,5-triazoles. None of the synthesized 1,4-isomers inhibited all three JAK family members. Compounds with phenyl or tolyl group substituents at the R<sub>1</sub> position were completely inactive compared with the corresponding analogues with a methyl substituted at the R<sub>1</sub> position. As a result of this structure-activity relationship, 54, which is substituted with a cyclopropylmethyl moiety, exhibited significant inhibitory activity and selectivity (IC<sub>50</sub>=41.9nM, fold selectivity JAK1/2 10.6 and JAK3/2 58.1). Compound 54 also exhibited an equivalent inhibition of wild type JAK2 and the V617F mutant. Moreover, 54 inhibited the proliferation of HEL 92.1.7 cells, which carry JAK2 V617F, and gefitinib-resistant HCC827 cells. Compound 54 also suppressed STAT3 phosphorylation at Y705.