Double Olympic champion Caster Semenya will not defend her 800-metres title at the World Championships in September after the Swiss Federal Tribunal reversed a ruling that temporarily lifted the IAAF's testosterone regulations imposed on her, a spokesman for the athlete said.
Semenya is appealing the Court of Arbitration for Sport's (CAS) ruling that supported regulations introduced by the sport's governing body, the International Association of Athletics Federations (IAAF).
These say that XY chromosome athletes with differences in sexual development (DSDs) can race in distances from 400m to a mile only if they take medication to reach a reduced testosterone level.
"I am very disappointed to be kept from defending my hard-earned title, but this will not deter me from continuing my fight for the human rights of all of the female athletes concerned," Semenya said in a statement from her representative.
The IAAF has yet to respond to a request for comment from Reuters.
The South African had been given a reprieve last month by the Swiss Federal Tribunal, which temporarily lifted the IAAF's regulations from her until the final outcome of her appeal.
"The Supreme Court emphasised the strict requirements and high thresholds for the interim suspension of CAS awards and found that these were not fulfilled," the statement said.
Dorothee Schramm, the lawyer leading Semenya's appeal, says they are still hopeful of a permanent lifting of the regulations.
"The judge's procedural decision has no impact on the appeal itself. We will continue to pursue Caster's appeal and fight for her fundamental human rights. A race is always decided at the finish line," Schramm said.
Semenya ran the quickest ever 800-metres on United States soil at the Prefontaine Classic Diamond League meeting on 30 June in a time of 1:55.70.
She told reporters afterwards that she would not compete at the World Championships in Doha if barred from running her preferred distance, having earlier hinted she could enter longer races in the future that are not covered by the regulations.