Ryan Moore steered the colt to a length success in the six-furlong event and O'Brien suggested a step up in trip could be a possibility.
"We always liked him at home," said O'Brien. "He travelled well today and it looks like he'll get further."
The €150,000 yearling purchase from the Goffs Sale, he impressed the Racing Post's form analysts, who noted that Istan "managed to get into all sorts of trouble but displayed his class as he was still able to win it….When he got into the clear he quickened well and won with a bit in hand."
Istan is from stakes-winning Halling mare Something Exceiting, who was second in an Epsom Oaks.
The first Australian runners by Excelebration will be seen in action next season, his yearlings selling for up to $175,000 this year.