CBR-5884 is an active, selective inhibitor of phosphoglycerate dehydrogenase (PHGDH) with an IC50 of 33 μM. CBR-5884 inhibits de novo serine synthesis in cancer cells and is selectively toxic to cancer cell lines with high serine biosynthetic activity. CBR-5884 selectively inhibits the proliferation of melanoma and breast cancer lines that have a high propensity for serine synthesis[1].