Mitigating this concern, Luo [37] maintains that PHGDH inhibition remains a viable cancer therapeutic target for two reasons: (1) a PHGDH inhibitor designed not to cross the blood-brain barrier would not interfere with serine homeostasis in the central nervous system, avoiding potential neurological effects reported for known PHGDH mutations in humans, and (2) serine deficiency disorders can be treated by exogenous serine supplement, whereas tumors' addiction to PHGDH might not be associated with serine flux. This evidence concerns the gene PHGDH and cancer.