I've seen some posts elsewhere where some have taken Leucovorin for fatigue.
Leucovorin is Folate, a B vitamin. It is prescribed with mtx to help prevent side effects of mtx. Folic acid is cheaper and usually enough for most people to prevent the side effects of mtx. Some people continue to battle mouth sores, fatigue, etc caused by mtx. I do not think it would help the fatigue caused by psa or any of the biologics though it is more likely fatigue comes from psa and not the biologics.