VVD-118313 (compound 5a) is a potent, selective JAK1 inhibitor. VVD-118313 targets an isoform-restricted allosteric cysteine to block JAK1-dependent trans-phosphorylation and cytokine signaling. VVD-118313 can be used for research of cancer. VVD-118313 is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups.