IDO2 and urea cycle disorder: Additionally, strategies to target altered metabolic characteristics (e.g. the Warburg effect, abnormal glutamine metabolism, and urea cycle deficiency (UCD)) or interfere with the “key point molecules” (e.g. Arginase and indoleamine 2,3-dioxygenase (IDO)) that both influence metabolic reprogramming and T cell exhaustion may be a promising exploration clinically [180].