Synthesis and Structure–Activity Relationships of DCLK1 Kinase Inhibitors Based on a 5,11-Dihydro‑6<i>H</i>‑benzo[<i>e</i>]pyrimido[5,4‑<i>b</i>][1,4]diazepin-6-one Scaffold

Doublecortin-like kinase 1 (DCLK1) is a serine/threonine kinase that is overexpressed in gastrointestinal cancers, including esophageal, gastric, colorectal, and pancreatic cancers. DCLK1 is also used as a marker of tuft cells, which regulate type II immunity in the gut. However, the substrates and functions of DCLK1 are understudied. We recently described the first selective DCLK1/2 inhibitor, DCLK1-IN-1, developed to aid the functional characterization of this important kinase. Here we describe the synthesis and structure–activity relationships of 5,11-dihydro-6H-benzo­[e]­pyrimido­[5,4-b]­[1,4]­diazepin-6-one DCLK1 inhibitors, resulting in the identification of DCLK1-IN-1.