Discovery of Potent and Selective Pyrazolopyrimidine Janus Kinase 2 Inhibitors

The discovery of somatic Jak2 mutations in patients with chronic myeloproliferative neoplasms has led to significant interest in discovering selective Jak2 inhibitors for use in treating these disorders. A high-throughput screening effort identified the pyrazolo­[1,5-<i>a</i>]­pyrimidine scaffold as a potent inhibitor of Jak2. Optimization of lead compounds <b>7a</b>–<b>b</b> and <b>8</b> in this chemical series for activity against Jak2, selectivity against other Jak family kinases, and good in vivo pharmacokinetic properties led to the discovery of <b>7j</b>. In a SET2 xenograft model that is dependent on Jak2 for growth, <b>7j</b> demonstrated a time-dependent knock-down of pSTAT5, a downstream target of Jak2

Discovery and Biological Profiling of Potent and Selective mTOR Inhibitor GDC-0349

Aberrant activation of the PI3K-Akt-mTOR signaling pathway has been observed in human tumors and tumor cell lines, indicating that these protein kinases may be attractive therapeutic targets for treating cancer. Optimization of advanced lead <b>1</b> culminated in the discovery of clinical development candidate <b>8h</b>, GDC-0349, a potent and selective ATP-competitive inhibitor of mTOR. GDC-0349 demonstrates pathway modulation and dose-dependent efficacy in mouse xenograft cancer models

Discovery of Novel PI3-Kinase δ Specific Inhibitors for the Treatment of Rheumatoid Arthritis: Taming CYP3A4 Time-Dependent Inhibition

PI3Kδ is a lipid kinase and a member of a larger family of enzymes, PI3K class IA­(α, β, δ) and IB (γ), which catalyze the phosphorylation of PIP2 to PIP3. PI3Kδ is mainly expressed in leukocytes, where it plays a critical, nonredundant role in B cell receptor mediated signaling and provides an attractive opportunity to treat diseases where B cell activity is essential, e.g., rheumatoid arthritis. We report the discovery of novel, potent, and selective PI3Kδ inhibitors and describe a structural hypothesis for isoform (α, β, γ) selectivity gained from interactions in the affinity pocket. The critical component of our initial pharmacophore for isoform selectivity was strongly associated with CYP3A4 time-dependent inhibition (TDI). We describe a variety of strategies and methods for monitoring and attenuating TDI. Ultimately, a structure-based design approach was employed to identify a suitable structural replacement for further optimization