Perpignan slumped to their seventh consecutive Top 14 defeat on the road to Lyon on Sunday while Biarritz are stone last after losing to Montpellier.
Perpignan's loss sees 2009 champions drop to twelfth in the standings as the crisis at the Catalan club deepens.
Agen, by contrast, climb to fourth with the season's half-way mark approaching after easily beating Bayonne.
Agen 37-18 Bayonne
Lyon 19-12 Perpignan
Biarritz 23-30 Montpellier
Lyon Olympique 19-12 USA Perpignan
Another week, another loss for Perpignan, who are now teetering on the edge of the relegation zone just three points clear of Lyon, who have a game in hand!
LOU winger Romain Grosso score the only try of the game just before half time after collecting Xavier Sadourny's cross-field kick to give the hosts a 13-9 lead at the break.
A drop from Sadourny shortly after the restart and full-back Romain Loursac's third penalty was enough to secure Lyon's second win of the season which lifts them off the foot of the table.
Once again it was left to Jerome Porical's boot to provide Perpignan's only points, with his late penalty saving a losing bonus point for the Catalans.
SU Agen 37-18 Aviron Bayonnais
Stade Armandie, Agen
Agen continue to ignore the preseason prognostics with another super display as they climb into fourth place - one point behind Castres and two points ahead of Toulon - with a game in hand.
The result is Agen's fourth straight victory while big-spending Bayonne slump to eleventh place in the standings after they ran out of steam in the final quarter of their third game in ten days.
Yoann Huget opened the scoring with a try for Bayonne but the hosts led 9-5 at half time thanks to the metronomic boot of Conrad Barnard.
Brice Dulin scored for Agen after the break only for Marc Baget to reply for Bayonne.
It was still anyone's game on the hour mark with Agen leading 20-18. But when Bayonne loose forward Sione Lauaki saw yellow for a shoulder charge, the wheels came off the visitors' bus.
Agen ran away with it in the closing stages with Junior Pelesasa and Saïmoni Vaka scoring tries to secure victory.
Biarritz Olympique 23-30 Montpellier HR
Parc des Sports Aquiléra
A ding-dong battle on the Basque coast went right down to the wire after the teams were separated by just two points with ten minutes to play.
In the end, Montpellier outscored their hosts four tries to one to claim a bonus point and keep in touch with the race for the play-offs.
Biarritz meanwhile needed a 82nd-minute penalty to claim a losing bonus point but nevertheless drop back to last place in the standings.
The Basques led 11-8 at half time thanks to an early try from American flyer Takudzwa Ngwenya.
But lock Mickaël de Marco's try put the visitors in front early in the second half after Fijian wing Timoci Nagusa had opened their account in the 23rd minute.
Montpol took control in the final quarter when Argentina full-back Lucas Amorosino scored a brilliant try from long range.
The Biarritz scrum was destroyed in the dying minutes, allowing François Trinh-Duc to profit from the disorder in the Basque defence to ghost his way over for the bonus-point try.