Caster Semenya will not defend her 800m world title in Doha this September after a setback in her challenge to the restricting of testosterone levels in female runners.
But the South African athlete said she would “continue her fight for human rights” despite her “disappointment”.
Caster Semenya has twice appealed against IAAF rules preventing her from running without medication.
But a ruling allowing her to compete has now been overturned.
Semenya is challenging world governing body the IAAF’s new rules that she and other athletes with differences of sexual development (DSD) must either take testosterone-reducing medication in order to compete in track events from 400m to the mile or change to another distance.
Semenya had been able to race while awaiting the decision of a Swiss court, having previously lost an appeal to the Court of Arbitration for Sport (Cas) in May.
The latest ruling by the Swiss Federal Supreme Court means she will not be allowed to compete at the World Championships in Doha.