Gennady Golovkin was left disappointed after the IBF stripped him of his middleweight world title.

Undefeated champion Golovkin lost his IBF belt on Wednesday for his failure to fight mandatory challenger Sergiy Derevyanchenko.

Golovkin – who boasts a 38-0 record with 34 knockouts – had a hearing late last month over not agreeing to the mandatory fight. He would have had until August 3 to prepare for the fight, but the Uzbek star never agreed. 

The IBF said in a statement that Golovkin fighting "an unsanctioned contest" against Vanes Martirosyan on May 5 was the primary driving force in the decision to vacate the title.

Golovkin fought Martirosyan last month and won with a second-round knockout.

"It comes as a complete shock that the IBF would make a ruling far beyond what the Derevyanchenko side was asking for," Golovkin promoter Tom Loeffler told ESPN.

"They weren't asking for him to be stripped. They were asking to have their shot at the IBF title next, but they never asked for him to be stripped. In light of this ruling, I think the IBF has completely mistreated GGG. It is the worst treatment they have ever shown any unified champion in their history.

"Gennady is disappointed in the ruling."

One of the main reasons Golovkin fought Martirosyan in the first place was because Saul 'Canelo' Alvarez tested positive for a banned substance and was suspended for six months. 

Alvarez and Golovkin were set for a May 5 rematch after they previously fought to a draw, but the rematch was cancelled, which led to the latter fighting Martirosyan.

Mexican Alvarez will return from suspension in September and talks over a rematch have taken place, though terms have proved difficult to nail down.

Golden Boy Promotions CEO Oscar De La Hoya said negotiations for a September 15 bout were ending on Tuesday, however, Loeffler said Golovkin is willing to drop his demands for an even split of the money.

"Gennady has agreed to come off his 50-50 demand," Loeffler added to ESPN. "Gennady wants the rematch with Canelo regardless of what Oscar says. He always wanted the fight with Canelo.

"He will come down to 55-45, which makes Canelo the A side. It will be Canelo making 55 per cent in a rematch against GGG, which will be much bigger than the first fight was for sure. The rematch with GGG is his biggest fight by far and Gennady's biggest fight. That's the fight we want."