Moses Itauma's fight with Filip Hrgovic will now be for the vacant IBF heavyweight title.
Brit Itauma (14-0, 12 KOs) is coming off a Round 5 knockout against Jermaine Franklin Jr. in March and will face Hrgovic (20-1, 15 KOs) who will be his toughest opponent to date.
The bout will take place on Aug. 29 at The O2 in London.
Promoter Frank Warren told BBC Sport that Queensberry paid Frank Sanchez, who was the IBF mandatory challenger, to step aside and promised the Cuban a fight against the winner.
The IBF title will now be up for grabs after former undisputed champion Oleksandr Usyk vacated all his belts in June.
While the WBC, WBA and WBO belts were awarded to other fighters, the IBF belt has remained vacant.
Should Itauma, 21, win the strap, he will become the second youngest fighter in history to claim a heavyweight world title, behind only Mike Tyson.
Victory would see him go ahead of Floyd Patterson and Muhammad Ali on the list of youngest heavyweight champions.
However, he faces by far the toughest challenge of his career in Hrgovic, a 2016 Olympic medallist whose only defeat as a professional came against Daniel Dubois in 2024 when the fight was stopped due to a cut.
At a pre-fight news conference, Hrgovic took aim at his opponent, insisting he hasn't been impressed by Itauma's rise.
"I'm not impressed the way the whole world is ... I'm a fighter, I look at [it from a] different angle," Hrgovic said.
"I never see him in trouble. I never see him get punched or dropped. He's definitely got skills and speed but to be a great fighter you must have heart, will, chin, endurance and we didn't see that yet.
"Maybe he's got all of that, but maybe not. I think I will test that. I will test is he a real deal or not. I believe that I will beat this guy and I will become heavyweight champion of the world."
