Rene Binder and ex-Formula Renault 3.5 racer Meindert van Buuren will race for the team in Italy, filling the seats previously held by Daniel De Jong and Oliver Rowland at Spa.
De Jong has been ruled out by injury following a crash at Spa, while Rowland returns to FR3.5 duty this weekend at Silverstone where he looks to extend his championship lead.
Team boss Sander Dorsman said: "It's been a tough couple of weeks for the team after Daniel's accident, but he's doing really well and recovering nicely.
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"We're very pleased to welcome both Rene and Meindert to the GP2 team, we're very much looking forward to it."
GP2 veteran Binder, who is filling in for De Jong, returns to the series after starting the season with Trident but missing the last round at Spa "due to an infection".
Van Buuren is returning to the MP fold, having raced for the team in Auto GP in 2013.
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