Goals from Kaku and Rafael Rodrigues in the first half put the 2024 champions on the path to a win that moves them onto 12 points at the halfway stage of the opening round.
Marwan Al-Sahafi gave Al Ittihad hope eight minutes after the interval, but Jan-Carlo Simic deflected Houssine Rahimi's strike into his own goal five minutes later and Matias Palacios' last-minute penalty completed the rout.
Meanwhile, Joao Felix scored twice as Al Nassr trounced Pakhtakor 6-2 in Tashkent to ensure Ange Postecoglou's side picked up their second win in three matches after their previous fixture in the competition was postponed last week.
"We did a great job," said Felix. "The game was not easy but we did it easily. The mentality was perfect so we are happy with the win."
The victory moves the Saudi Pro League champions on to six points from three matches. Their meeting with Al-Wasl from the United Arab Emirates has yet to be rescheduled.
Defending champions Al Ahli were held to a 0-0 draw by Al Sadd in Qatar while 10-man Tractor FC of Iran twice came from behind to draw 2-2 with Neftchi from Uzbekistan after Masoud Kazemayni equalised in the 99th minute.
Brendan Rodgers' Al Qadsiah eased to a 5-0 win in Doha over an Al Gharafa side that remain without a point from their four matches.
Julian Quinones scored twice for the Saudi club as they moved onto eight points from four matches.
Al Wasl secured their first win of the campaign with a 4-3 victory over Iraq's Air Force Club despite Murad Mohammed's 81st-minute goal giving the visitors late hope.
"It was a great game for us, we did an amazing job," said Mehdi Taremi, who opened the scoring for Al-Wasl in the sixth minute. "We suffered three goals but we were a little bit unlucky not to score more."
The first eight finishers in the 16-team groups in both East and West Asia will advance to the knockout rounds.
The quarter-finals, semi-finals and final will be played in Saudi Arabia in April and May.