Lyon's stay in the Top 14 could be coming to an end after they suffered a 22-9 defeat to fellow strugglers at Stade Matmut.
An ill-tempered encounter, with five yellow cards and two reds dished out, saw Brive move eight points clear of the relegation zone and leave Lyon rooted to the bottom.
Lyon's Antonio Testa and Brive's Pablo Henn sent off early in the second half following a mass brawl - however the visitors kept their cool to hold on.
South African wing Ronnie Cooke scored the only try of the game, while Mathieu Belie added 14 points from the boot and Julien Caminati tagged on a late penalty.
Former Sale ace Lee Thomas scored the only points for Lyon, with three penalties.
Agen kept their slim play-off hopes alive with a surprise 23-12 victory over fourth-placed Castres.
Despite having two players sin-binned, Agen are now just two points short of the play-offs with Gert Muller and Saimoni Vaka having crossed for tries.
Conrad Barnard also added 13 points, with four penalties from Romain Teulet all that Castres could muster.