Sergey Kovalev's bout against Bektemir Melikuziev has been cancelled after the former three-time light-heavyweight world champion failed a drugs test.
Kovalev returned a positive for synthetic testosterone via a test carried out by the Voluntary Anti-Doping Association (VADA).
The scheduled fight card at Fantasy Springs Resort Casino in Indo, California has been pulled by Golden Boy Promotions as a result.
A statement released by Golden Boy read: "The Kovalev vs Melikuziev boxing event scheduled for January 30 has been cancelled following a positive test for a banned substance (synthetic testosterone) on behalf of Sergey Kovalev through the Voluntary Anti-Doping Association (VADA).
"Upon learning of Kovalev's adverse finding, the California State Athletic Commission (CSAC) determined that they must cancel the event."
Kovalev has not fought since losing his WBO light-heavyweight title in an 11th-round knockout defeat to Canelo Alvarez in November 2019, a setback that dropped the 37-year-old's professional record to 34 victories (29 knockouts), four defeats and a solitary draw.
Counting from his first career loss, when Andre Ward edged a close points verdict against Kovalev in 2016, the Russian has won four and lost four of his past eight fights, with the three subsequent losses all coming by stoppage.
He was scheduled to box former world title challenger Sullivan Barrera on April 25 last year but the coronavirus pandemic put paid to that, as it did the original plans for the meeting against Uzbekistan's 2016 Olympic bronze medallist Melikuziev (6-0, 5 KOs) to take place in Moscow.
