MSC-4381 (MCT4-IN-1) is an orally active and selective monocarboxylate transporter 4 (MCT4/SLC16A3) inhibitor with an IC50 of 77 nM and a Ki of 11 nM. MSC-4381 targets to the cytosolic domain of MCT4. MSC-4381 results in lactate efflux inhibition and reduction of cellular viability in MCT4 high expressing cells. MSC-4381 has the potential for MCT4 transporter inhibition research[1]. MSC-4381 is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups.