Cassang double sinks Saints
Lopez was stretchered off with a suspected broken leg. The 28-year-old Lopez was writhing in agony after a clash with Northampton's Nick Groom in the 23rd minute.
Fritz Lee and Etienne Falgoux grabbed the other tries to leave Saints without a win in their two matches.
Clermont took just seven minutes to open the scoring after a solid scrum created the chance for Lee to dot down. Parra added the extras to ensure a 7-0 lead.
The hosts lost Lopez soon after.
Saints seemed to be building up a head of steam in the 28th minute, however, Foden was stopped just short. Bad boy Dylan Hartley took centre stage once again as he was shown a yellow card for catching Rabah Slimani in the face.
Clermont made the most of the extra man as Cassang scored his first on the stroke of half-time to hand his side a 14-0 lead.
Cassang secured his brace soon after the restart as he raced away but Saints hit back seven minutes later when Christian Day benefitted from a driving maul to get his side on the board. Saints trailed 7-19.
The home side then found themselves down to 14 after Slimani was shown yellow in the 60th minute for a shoulder charge. Saints could not turn their advantage into points though and it would be Clermont who put the result to bed five minutes later when Falgoux secured the bonus point.
Scorers:
For Clermont:
Tries: Lee, Cassang 2, Falgoux
Cons: Parra 2
For Northampton Saints:
Try: Day
Con: Mallinder
Yellow cards: Dylan Hartley (Northampton Saints, 29), Rabah Slimani (Clermont, 60)
Teams:
Clermont: 15 Isaia Toeava, 14 David Strettle, 13 Damian Penaud, 12 Remi Lamerat, 11 Alivereti Raka, 10 Camille Lopez, 9 Morgan Parra, 8 Fritz Lee, 7 Alexandre Lapandry, 6 Judicaël Cancoriet, 5 Sitaleki Timani, 4 Flip Van Der Merwe, 3 Rabah Slimani, 2 Benjamin Kayser, 1 Raphael Chaume.
Replacements: 16 John Ulugia, 17 Etienne Falgoux, 18 Aaron Jarvis, 19 Paul Jedrasiak, 20 Camille Gerondeau, 21 Charlie Cassang, 22 Peter Betham, 23 Nick Abendanon.
Northampton Saints: 15 Harry Mallinder, 14 Ben Foden, 13 Nafi Tuitavake, 12 Luther Burrell, 11 Tom Collins, 10 Piers Francis, 9 Nic Groom, 8 Teimana Harrison, 7 Tom Wood, 6 Courtney Lawes, 5 Christian Day, 4 Api Ratuniyarawa, 3 Jamal Ford-Robinson, 2 Dylan Hartley (captain), 1 Alex Waller.
Replacements: 16 Mikey Haywood, 17 Francois van Wyk, 18 Kieran Brookes, 19 Michael Paterson, 20 Jamie Gibson, 21 Cobus Reinach, 22 Tom Stephenson, 23 Ken Pisi.
Referee: Ben Whitehouse (Wales)
Assistant referees: Gwyn Morris (Wales), Wayne Davies (Wales)
TMO: Jon Mason (Wales)
