PKUMDL-WQ-2101 is a potent and selective non-NAD+-competing allosteric inhibitor of phosphoglycerate dehydrogenase (PHGDH) that selectively inhibits serine synthesis in cancer cells. PKUMDL-WQ-2101 binds to allosteric site I, which is located close to active site. PKUMDL-WQ-2101 inhibits tumor growth of MDA-MB-468 xenografts in mice.