Top 14 leaders Clermont Auvergne moved eight points clear at the summit by edging out struggling Grenoble 21-20 on Saturday.
In-form Clermont have now won six games in a row, but they had to come from behind after their lowly visitors staged a second-half fightback to lead with just 12 minutes remaining.
Morgan Parra and Otar Giorgadze scored first-half tries to give Clermont a 15-7 lead at the break, but Alexandre Dardet added to a score from Gio Aplon and Jonathan Wisniewski took his tally with the boot to 10 points to give Grenoble a 20-18 lead only for Patricio Fernandez to settle it from the tee for the hosts.
Champions Racing 92 left it late to claim their third consecutive Top 14 victory by seeing off Montpellier 21-9 at Stade Olympique Yves-du-Manoir.
Tries from Henry Chavancy and Xavier Chauveau in the last eight minutes settled what had been a close encounter and moved Racing up to fifth.
Three penalties apiece from Johan Goosen and Ben Botica had the two sides locked at 9-9, but Chavancy crossed to put Racing in front and Chauveau added another as Montpellier missed the chance to go second in the table.
Bordeaux Begles responded to back-to-back defeats by beating Stade Francais 37-19 at Stade Chaban Delmas.
Simon Hickey scored 17 points with the boot, while Hugh Chalmers, Clement Maynadier, Julien Rey and Yann Lesgourgues dotted down in a comfortable victory for Raphael Ibanez's men.
High-flying Toulouse needed a last-gasp Samuel Marques penalty to beat Castres 16-15, while bottom side Bayonne went down 26-9 at Brive.