CME Group Inc Chief Executive Officer Craig Donohue, who has led the exchange operator since 2004, will leave the company, probably before its annual meeting next month, he said on Thursday.

Donohue, who was to hand the reins to current President Phuphinder Gill at the end of the year, said the transition process was going exceptionally well and would be completed "very soon."

The CME's annual meeting will be held May 23.