Caster Semenya will not be able to defend her 800 metres title at the World Athletics Championships after a Swiss court reversed prior rulings that allowed her to compete while she appealed against controversial IAAF regulations.
The double Olympic champion was granted permission to race without restriction after lodging an appeal with the Federal Supreme Court of Switzerland (SFT) against the Court of Arbitration for Sport's (CAS) verdict in her case against the IAAF.
CAS ruled the IAAF could implement a regulation that would require Semenya to take medication to lower her testosterone levels to take part in women's track events ranging from 400m to a mile.
A judge has now overturned the SFT's decision to allow Semenya to compete while it assessed the case, and Semenya will consequently be unable to take to the track in Qatar.
A statement issued from the South African's camp on Tuesday read: "Caster remains steadfast in her defiance of the highly controversial IAAF regulations that require female athletes with naturally elevated testosterone levels to undergo hormonal drug intervention in order to compete in international competitions.
"Yesterday, a single judge of the Swiss Federal Supreme Court reversed prior rulings that had temporarily suspended the IAAF regulations pending the outcome of Caster's appeal against the CAS award.
"In this latest decision, the Supreme Court emphasised the strict requirements and high thresholds for the interim suspension of CAS awards and found that these were not fulfilled.
"This ruling will prevent Caster from defending her title at the World Championships in September 2019."
With the Tokyo 2020 Olympics under a year away, Semenya will continue to appeal against the regulations.
"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.