Noverre, who won the French 2,000 Guineas, has failed a subsequent drug test and is likely to be disqualified. The colt, owned by Sheikh Mohammed's Godolphin, tested positive for the arthritis medication methylprednisolone.
According to Godolphin, Noverre suffers from arthritis and has been treated for the condition.
"This is a very unfortunate situation," said Simon Crisford, Godolphin's racing manager. "We don't know why traces were found in Noverre's system as the same therapeutic treatment cycle has caused no problems in the past. We accept the French findings and are resigned to Noverre being disqualified from the classic.
"The welfare of our horses is of paramount importance to Godolphin. We have competed for the last eight years in international racing and we are very conscious of the international rules pertaining to pre-race medication. This is a one-off situation which could not have been foreseen because of the stringent guidelines that we follow."
Noverre beat Vahorimix by a head in the French guineas. He also ran at royal Ascot last month and was a close second to Black Minnaloushe in the group one St. James's Palace Stakes.