Sun was banned for eight years by CAS in February after it accepted an appeal from WADA against a decision by swimming body FINA to clear Sun of wrongdoing for his conduct during a 2018 test.
Sun appealed against that decision and WADA has issued a statement sayng they have been informed the Swiss Federal Tribunal had upheld a challenge but not made any comment on the substance of the case.
"WADA will take steps to present its case robustly again when the matter returns to the CAS Panel, which will be chaired by a different president," the statement said.
