Janibek Alimkhanuly has tested positive for a banned substance before his scheduled middleweight unification bout against Erislandy Lara on Saturday.

The World Boxing Organisation (WBO) says it has been informed of the Kazakh fighter’s failed test by the Voluntary Anti-Doping Association (Vada) and an internal investigation is under way.

Alimkhanuly, who holds the IBF and WBO titles, has been pulled from the bout against WBA champion Lara and replaced by Venezuela’s Johan Gonzalez, according to American media.

It has been reported the banned substance is meldonium, a performance-enhancing drug which can boost an athlete’s endurance. It has been banned by the World Anti-Doping Agency (Wada) since 2016.

Alimkhanuly’s ‘A’ sample returned an adverse analytical finding, and the fighter has requested that a second ‘B’ sample be tested.

Writing on X, Alimkhanuly said he was “surprised” at Vada’s findings.

“I have always supported clean sport, you know this well. I was surprised when I read the news,” said Alimkhanuly., external

“Vada took the first test and said everything was clean. I have not made any changes to my vitamins. I don’t know what happened with the second test, so I requested a retest.”

Alimkhanuly last fought on 5 April when he retained his WBO and IBF belts against Anauel Ngamissengue via a fifth-round stoppage.

The 32-year-old has won all 17 of his professional bouts since making his debut in 2016.

Cuban-American Lara last fought 14 months ago when he stopped Danny Garcia in the ninth round to retain his WBA title.

The 42-year-old, who is a former champion at light middleweight, has won 31 of 37 fights since debuting in 2008.

Gonzalez, 34, has won 36 of his 40 bouts and last competed in March when he defeated Jarrett Hurd by split decision.