Antitarget Selectivity and Tolerability of Novel Pyrrolo[2,3-]pyrimidine RET Inhibitors.

The selective inhibition of RET kinase as a treatment for relevant cancer types including lung adenocarcinoma has garnered considerable interest in recent years and prompted a variety of efforts toward the discovery of small-molecule therapeutics. Hits uncovered via the analysis of archival kinase data ultimately led to the identification of a promising pyrrolo[2,3-]pyrimidine scaffold. The optimization of this pyrrolo[2,3-]pyrimidine core resulted in compound , which demonstrated potent RET kinase inhibition and robust efficacy in RET-driven tumor xenografts upon multiday dosing in mice. The administration of was well-tolerated at established efficacious doses (10 and 30 mg/kg, po, qd), and plasma exposure levels indicated a minimal risk of KDR or hERG inhibition , as evaluated by Miles assay and free plasma concentrations, respectively.