Two-time Olympic gold medalist Caster Semenya is taking her fight to the European Court of Human Rights.
Semenya is seeking to appeal a 2020 decision by the Switzerland Supreme Court that ruled women with naturally elevated testosterone levels could not take part in events without medical interventions to lower their testosterone.
Rules introduced by World Athletics in 2018 prevent some female athletes with naturally high testosterone levels from participating in competitions.
Semenya is not allowed to compete in events between 400m and a mile without taking testosterone-reducing drugs, following a 2019 rule change by governing body World Athletics.
The 30-year-old South African lost an appeal to Switzerland's Federal Supreme Court in September but still harbours hopes of defending her Olympic title in Tokyo this year.