Anthony Joshua's heavyweight title defence against Jarrell Miller is in jeopardy following the revelation his opponent has tested positive for a banned substance.
A drug test taken by the Voluntary Anti-Doping Association (VADA) in March showed than Miller had recorded an adverse finding.
Eddie Hearn and his team are now actively looking for replacements for Miller to headline the card at Madison Square Garden in June in what will be Joshua's US debut.
Miller is highly likely to be refused a licence to box by the New York State Athletic Commission if his B sample comes back positive.
'Big Baby', undefeated in 24 professional bouts, was scheduled to fight for a world title for the first time in his career.
The 30-year-old was previously given a nine-month suspension by the California State Athletic Commission in 2014 after testing positive for banned stimulant methylhexaneamine.
It is another substance however that has raised red flags with boxing’s governing bodies.
What is GW1516?
Also known as cardarine or endurobol, the drug was developed in the 1990s to treat metabolic and cardiovascular diseases.
It was found to improve physical performance but testing showed it caused cancer growth.
Further development was abandoned in 2007.
Who are VADA?
An independent organisation operating within boxing and mixed martial arts, the Voluntary Anti-Doping Association provide counselling for athletes at risk as well as education about health and nutrition.
What happens next?
Jarrell Miller is likely to face a hearing with the New York State Athletic Commission, who will decide whether he will be allowed to fight Anthony Joshua on June 1.
