Synthesis and In Vitro Evaluation of a Set of 6-Deoxy-6-thio-carboranyl d-Glucoconjugates Shed Light on the Substrate Specificity of the GLUT1 Transporter

[Image: see text] Glucose- and sodium-dependent glucose transporters (GLUTs and SGLTs) play vital roles in human biology. Of the 14 GLUTs and 12 SGLTs, the GLUT1 transporter has gained the most widespread recognition because GLUT1 is overexpressed in several cancers and is a clinically valid therapeutic target. We have been pursuing a GLUT1-targeting approach in boron neutron capture therapy (BNCT). Here, we report on surprising findings encountered with a set of 6-deoxy-6-thio-carboranyl d-glucoconjugates. In more detail, we show that even subtle structural changes in the carborane cluster, and the linker, may significantly reduce the delivery capacity of GLUT1-based boron carriers. In addition to providing new insights on the substrate specificity of this important transporter, we reach a fresh perspective on the boundaries within which a GLUT1-targeting approach in BNCT can be further refined.