ABSTRACT
Bruton's tyrosine kinase (Btk) is thought to play a pathogenic role in chronic immune diseases such as rheumatoid arthritis and lupus. While covalent, irreversible Btk inhibitors are approved for treatment of hematologic malignancies, they are not approved for autoimmune indications. In efforts to develop additional series of reversible Btk inhibitors for chronic immune diseases, we sought to differentiate from our clinical stage inhibitor fenebrutinib using cyclopropyl amide isosteres of the 2-aminopyridyl group to occupy the flat, lipophilic H2 pocket. While drug-like properties were retained-and in some cases improved-a safety liability in the form of hERG inhibition was observed. When a fluorocyclopropyl amide was incorporated, Btk and off-target activity was found to be stereodependent and a lead compound was identified in the form of the (R,R)- stereoisomer.
ABSTRACT
Mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) is a serine/threonine kinase implicated in the regulation of many biological processes. A fragment-based lead discovery approach was used to generate potent and selective MAP4K4 inhibitors. The fragment hit pursued in this article had excellent ligand efficiency (LE), an important attribute for subsequent successful optimization into drug-like lead compounds. The optimization efforts eventually led us to focus on the pyridopyrimidine series, from which 6-(2-fluoropyridin-4-yl)pyrido[3,2-d]pyrimidin-4-amine (29) was identified. This compound had low nanomolar potency, excellent kinase selectivity, and good in vivo exposure, and demonstrated in vivo pharmacodynamic effects in a human tumor xenograft model.
