NCT-503 is primarily used as a selective inhibitor of the enzyme PHGDH (phosphoglycerate dehydrogenase), which plays a key role in the serine biosynthesis pathway. This compound is widely applied in cancer research, especially in studies involving tumors that overexpress PHGDH, such as melanoma, breast cancer, and certain types of leukemia. By inhibiting PHGDH, NCT-503 disrupts the production of serine in cancer cells, leading to reduced cell proliferation and, in some cases, cell death. It is also used as a tool compound to study metabolic dependencies in tumor cells and to validate PHGDH as a therapeutic target. Its application extends to preclinical models where modulation of serine metabolism is required to understand tumor growth, survival, and response to therapy.