Publications (2)7.91 Total impact
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Article: Differential Selectivity of JAK2 Inhibitors in Enzymatic and Cellular Settings.
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ABSTRACT: Small molecule inhibitors of Janus kinase (JAK) family members (JAK1, JAK2, JAK3, and Tyk2) are currently being pursued as potential new modes of therapy for a variety of diseases, including the inhibition of JAK2 for the treatment of myeloproliferative disorders. Selective inhibition within the JAK family may be beneficial in avoiding undesirable side effects (e.g. immunosupression) caused by parallel inhibition of other JAK members. In an effort to design an assay paradigm for the development of JAK2 selective inhibitors, we investigated whether compound selectivity differed between cellular and purified enzyme environments. A set of JAK2 inhibitors was tested in a high-throughput JAK family cell assay suite and in corresponding purified enzyme assays. The high-throughput JAK cell assay suite comprises Ba/F3 cells individually expressing translocated ETS leukemia (TEL) fusions of each JAK family member (TEL-JAK Ba/F3) and an AlphaScreen(®) phosphorylated-STAT5 (pSTAT5) immunoassay. Compound potencies from the TEL-JAK Ba/F3 pSTAT5 assays were similar to those determined in downstream cell proliferation measurements and more physiologically relevant cytokine-induced pSTAT5 PBMC assays. However, compound selectivity data between cell and purified enzyme assays were discrepant due to different potency shifts between cell and purified enzyme values for each JAK family member. For any JAK small molecule development program, our results suggest that relying solely on enzyme potency and selectivity data may be misleading. Adopting the high-throughput TEL-JAK Ba/F3 pSTAT5 cell assay suite in lead development paradigms should provide a more meaningful understanding of selectivity and facilitate the development of more selective JAK inhibitors.Experimental hematology 01/2013; · 3.11 Impact Factor -
Article: Discovery of potent and highly selective thienopyridine Janus kinase 2 inhibitors.
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ABSTRACT: Developing Janus kinase 2 (Jak2) inhibitors has become a significant focus for small molecule drug discovery programs in recent years due to the identification of a Jak2 gain-of-function mutation in the majority of patients with myeloproliferative disorders (MPD). Here, we describe the discovery of a thienopyridine series of Jak2 inhibitors that culminates with compounds showing 100- to >500-fold selectivity over the related Jak family kinases in enzyme assays. Selectivity for Jak2 was also observed in TEL-Jak cellular assays, as well as in cytokine-stimulated peripheral blood mononuclear cell (PBMC) and whole blood assays. X-ray cocrystal structures of 8 and 19 bound to the Jak2 kinase domain aided structure-activity relationship efforts and, along with a previously reported small molecule X-ray cocrystal structure of the Jak1 kinase domain, provided structural rationale for the observed high levels of Jak2 selectivity.Journal of Medicinal Chemistry 11/2011; 54(24):8440-50. · 4.80 Impact Factor
