Whyte's 'adverse' doping test forces cancellation of Joshua bout
The Voluntary Anti-Doping Association said a "random anti-doping protocol" undertaken by Whyte had returned the adverse findings, leading to the all-British grudge match being called off.
Joshua's rematch with Whyte had been due to take place at London's O2 Arena on August 12th.
Fight promoter Matchroom said in a statement: "Today, the Voluntary Anti-Doping Association (VADA) informed Matchroom, the Association of Boxing Commissions and the British Boxing Board of Control that Dillian Whyte had returned adverse analytical findings as part of a random anti-doping protocol.
"In light of this news, the fight will be cancelled and a full investigation will be conducted."
Whyte claimed he had done nothing wrong and deserved a chance to clear his name.
"I am shocked and devastated to learn of a report by VADA of adverse findings relating to me," he wrote on Twitter.
"I only learned of it this morning and am still reacting to it. I have also just seen that the fight is being cancelled without having any chance to demonstrate my innocence before the decision was taken.
"I can confirm without a shadow of doubt that I have not taken the reported substance, in this camp or at any point in my life."
Whyte said he had produced false positive tests in the past and vowed to fight the result.
"I insisted on 24/7 VADA testing for this fight, as I have done voluntarily and at my own expense for all of my fights for many, many years," he said.
"This is not the first time that I have been reported as having an adverse finding for a substance which I have not taken, and as I did last time I will again prove that I am completely innocent.
"In the meantime all I can do is express my extreme disappointment to boxing fans, who will miss out on what was sure to be a great event."
Whyte lost his unbeaten 16-fight record when he was stopped by Joshua at the O2 Arena in 2015 when contesting for the vacant British heavyweight title.
The rematch was announced in July after talks over Joshua taking on Tyson Fury broke down.
Former world champion Joshua had also been linked with a fight against Deontay Wilder in Saudi Arabia.
Joshua's win over Whyte almost eight years ago avenged a defeat to his Jamaica-born rival when they had met as amateurs.
Whyte recovered from his defeat to Joshua by winning his next 11 fights and after losing to Alexander Povetkin in 2020 he gained revenge by stopping the Russian in a rematch.
Defeat to defending WBC champion Tyson Fury at Wembley in 2022 was followed by a points win over Jermaine Franklin the following November.
