MRK-B

MRK-B is a small molecule research compound developed by Merck & Co. (Merck Sharp & Dohme) as a structural control for its YAP1/TAZ-TEAD inhibitor program. While structurally similar to the active lead compound MRK-A, MRK-B lacks significant inhibitory activity against the TEAD-mediated transcriptional complex, demonstrating an IC50 greater than 10,000 nM in TEAD reporter assays. It is used in preclinical research to validate the specificity of active YAP/TEAD inhibitors in models of Hippo pathway-driven cancers, such as NF2-deficient mesothelioma. In experimental assays, MRK-B did not impact the clonogenic growth or viability of H226 mesothelioma cells, serving as a negative control to confirm that the anti-tumor effects of active analogs are due to specific target engagement.