With just three laps remaining, Biaggi and Melandri ramped up the intensity by exchanging passes through the opening turns, the BMW rider nosing ahead only to be passed again by Biaggi with just over a lap remaining.
Setting up an exciting final lap prospect, Biaggi would nonetheless keep his lines clean to ensure Melandri couldn't have a run on him into the slow speed hairpin.
Completing his third consecutive victory – his fourth of the season –, Biaggi has multiplied his advantage in the overall standings at the expense of non-scorers Rea and Sykes.
Sykes had looked on course for a podium finish, despite the persistent attentions of Ayrton Badovini, Carlos Checa
and Chaz Davies, but the scrap would come to an unsatisfying conclusion when Badovini made contact with Sykes at turn four on the final lap.
Sending Badovini, who was set to at least equal his best finish at WSBK level, down immediately, Sykes tried in vain to keep the squirreling Kawasaki upright, but would come crashing down, denying him a crucial 16 points.
Their misfortune elevated a delighted Checa into a fortuitous podium around his home circuit, while ParkinGO Aprilia's Davies found himself less than a second from a maiden rostrum finish in a fine fourth place.
With the remaining field being bumped up two positions at the chequered flag, Laverty finished fifth, though the Irishman won't be so enamoured with his substantial drop in pace during the second half of the race having run third for a time.
Michel Fabrizio spared some blushes at BMW Italia to claim sixth, the Italian putting in a stealthily impressive ride up the order from the back of the field having been delayed by the first corner incident.
His efforts were enough to demote Leon Haslam to seventh, the BMW rider struggling for speed as he spent much of his race dicing with Davide Giugliano in eighth.
Leon Camier found late pace to secure a welcome top ten finish in ninth on the FIXI Crescent Suzuki, while Maxime Berger brought scant joy to Effenbert Liberty Ducati in tenth following the first corner clash that eliminated Smrz and heavily delayed eventual 12th place finisher Sylvain Guintoli.