ALT, AST ,GGT elevated to 1500,400, 700

[Annluu]

My 15 years old boy had liver transplant two years ago, month ago was hospitalized for rejection, after anti rejection, his three enzymes keep elevating day by day, did two more additional biopsy after treatment, didn't see any rejection and viral infection, now Dr s lost direction, give antibody treat for rejection, gave ganciclvir for antivirus, but non of these working, three of these enzyme elevated from 400u to 1500 day by day,feel very frustrated and hopeless, any one can give any suggestion?