Leiter was outrighted to Triple-A Iowa on Thursday, Andy Martinez of Marquee Sports Network reports.
Leiter was designated for assignment by the Cubs last week but will remain with the organization after going unclaimed on waivers. The right-hander made 35 appearances (four starts) in the majors last year and posted a 3.99 ERA, 73:25 K:BB and 1.14 WHIP in 67.2 innings.