Player provisionally suspended by ITIA for clostebol, the same substance involved in Sinner case

During the ITF World Tennis Tour M15 tournament held in Kayseri, Turkey, on October 2, 2025, an in-competition anti-doping control returned a positive result for clostebol, a prohibited substance classified as an Anabolic Androgenic Steroid. The International Tennis Integrity Agency (ITIA) later confirmed that the samples belonged to Juan Sebastián Domínguez Collado, a 23-year-old player from Guatemala who had recently reached a career-high ATP ranking of World No. 1660.

The initial analysis of the A sample detected the presence of the banned metabolite, automatically triggering the next step in the anti-doping procedure. The subsequent analysis of the B sample confirmed the finding, formally establishing the presence of clostebol in the player’s system.

Under the World Anti-Doping Agency (WADA) Prohibited List, clostebol is categorized as a non-Specified substance, meaning violations involving it are treated with particular severity. In addition, Domínguez Collado did not possess a valid Therapeutic Use Exemption (TUE), which led to the mandatory imposition of a provisional suspension.

Clostebol is the exact same substance that Jannik Sinner tested positive for during Indian Wells in 2024. The Italian tested positive twice, though in trace amounts that were deemed unintentional according to the ITIA's ruling. However, after initially being cleared of fault or negligence, WADA announced an appeal that reopened the case, threatening Sinner with a potential suspension of one to two years. The Clostebol controversy ultimately concluded with the Italian accepting a three-month suspension to avoid the appeal, effectively closing his case.

The provisional suspension came into effect on November 19, 2025, the same day the ITIA issued a pre-charge notice alleging violations of Articles 2.1 and 2.2 of the Tennis Anti-Doping Programme (TADP). These articles relate to the presence of a prohibited substance in a player’s sample and the use or attempted use of a prohibited substance or method. Although Domínguez Collado retains the right to challenge the provisional suspension before an independent tribunal chair, he has not exercised this option as of now.

As a result of the suspension, Domínguez Collado is currently barred from all professional tennis activities. He is prohibited from competing in tournaments, coaching, training, or attending events sanctioned by the ITIA’s member organizations, which include the ATP, WTA, ITF, the four Grand Slam tournaments, and all affiliated national tennis associations. These restrictions will remain in place until the disciplinary process is fully resolved.

The agency emphasized that the proceedings are part of its broader mandate to uphold fairness, transparency, and integrity within professional tennis, ensuring that all players are held to the same standards under the sport’s anti-doping framework.