Gresini rider Gabriel Rodrigo muscled his Honda into the lead from second on the grid at the start, though he would be usurped by Arenas from seventh on the grid at Turn 3.
A near-highside for Rodrigo at the Turn 7 left-hander broke the pack up from Arena, who managed to open up a lead of eight tenths by the end of the lap and threatened to break away.
Aspar’s Arenas is carrying some nasty bruising on his left leg following his fast crash from the lead at the Andalusian GP last month and admitted he didn’t expect to be able to race at Brno.
His lead was eaten into by the chasing pack by lap three, with poleman Raul Fernandez attempting – but failing to execute – a pass for the lead on his Ajo KTM at Turn 9.
By lap six, Arenas had been relieved of his lead from Foggia, who fended off all attacks on the position through to the final lap.
Honda Team Asia’s Ai Ogura launched a raid on Foggia on the last lap into Turn 3, but the Leopard rider scythed back through at Turn 4.
Foggia’s hopes were dealt a boost when Arenas carved up Ogura at Turn 12 for the run up the hill to the penultimate corner, giving the Leopard rider enough margin to get through the final turns safely to claim his first win.
It comes after the Italian left Valentino Rossi’s VR46 Academy at the end of last year.