Russian racer Matevos Isaakyan will make his first foray into the GP3 series in the upcoming round at Bahrain, joining Koiranen.
The Formula Renault 2.0 frontrunner, backed by SMP Racing, finished third behind Nyck de Vries and Charles Leclerc in the FR2.0 Alps series in 2014.
Isaakyan, 17, then went on to take fourth in Alps in his sophomore season and was 10th in the Eurocup.
He has recently tested in Formula 3.5 with Pons and even topped one of the days in the run at Motorland Aragon.
While the Russian has raced for JD Motorsport for the last two seasons, his Koiranen move is unsurprising given the Finnish squad's ties to his backers at SMP - with Koiranen running SMP's F4 championship and taking on a number of Russian juniors in FR2.0 over the recent years.
Hong Kong driver Adderly Fong, a Lotus F1 development driver, will be the one making way for Isaakyan in Koiranen's GP3 line-up.