Antiparasitic agents

1. A compound of the formula

or a pharmaceutically acceptable salt of said compound, wherein:

R 1 , R 2 , R 3 , R 4 and R 5 are each independently selected from H, halo, CN, CF 3 and CONH 2 .

2. A compound according to claim 1 wherein R 1 , R 2 , R 3 , R 4 and R 5 are each independently selected from H, F, Cl, Br, CN and CF 3 .

3. A compound according to claim 2 wherein at least one of R 1 , R 2 , R 3 , R 4 and R 5 is CN and at least two of R 1 , R 2 , R 3 , R 4 and R 5 are H.

4. A compound according to claim 2 wherein R 1 and R 4 are H, one of R 2 and R 3 is H and the other is CN, and R 5 is selected from F, Cl, Br and CF 3 .

5. A compound according to claim 4 wherein R 3 is CN and R 5 is CF 3 .

6. A compound according to claim 1 selected from:

N-{1-cyano-2-[5-cyano-2-(trifluoromethyl)phenoxy]-1-methylethyl}-4-pentafluorothiobenzamide,

N-{(1R)-1-cyano-2-[5-cyano-2-(trifluoromethyl)phenoxy]-1-methylethyl}-4-pentafluorothiobenzamide,

N-{(1S)-cyano-2-[5-cyano-2-(trifluoromethyl)phenoxy]-1-methylethyl}-4-pentafluorothiobenzamide,

N-[2-(2-chloro-5-cyanophenoxy)-1-cyano-1-methylethyl]-4-pentafluorothiobenzamide,

N-[2-(2-chloro-5-cyanophenoxy)-(1R)-1-cyano-1-methylethyl]-4-pentafiuorothiobenzamide,

N-[2-(2-chloro-5-cyanophenoxy)-(1S)-1-cyano-1-methylethyl]-4-penrafluorothiobenzamide,

N-{1-cyano-2-[4-cyano-2-(trifluoromethyl)phenoxy]-1-methyl ethyl}-4-pentafluorothiobenzamide,

N-{(1R)1-cyano-2-[4-cyano-2-(trifluoromethyl)phenoxy]-1-methylethyl}-4-pentafluorothiobenzamide,

N-{(1S)1-cyano-2-[4-cyano-2-(trifluoromethyl)phenoxy]-1-methylethyl}-4-pentafluorothiobenzamide,

N-{2-[2-chloro-5-cyano-3-(trifluoromethyl)phenoxy]-1-cyano-1-methylethyl}-4-pentafluorothiobenzamide,

N-{2-[2-chloro-5-cyano-3-(trifluoromethyl)phenoxy]-(1R)-1-cyano-1-methylethyl}-4-pentafluorothiobenzamide,

N-{2-[2-chloro-5-cyano-3-(trifluoromethyl)phenoxy]-(1S)-1-cyano-1-methylethyl}-4-pentafluorothiobenzamide,

N-[2-(2-chloro-4,5-dicyanophenoxy)-1-cyano-1-methylethyl]-4-pentafluorothiobenzamide,

N-[2-(2-chloro-4,5-dicyanophenoxy)-(1R)-1-cyano-1-methylethyl]-4-pentafluorothiobenzamide,

N-[2-(2-chloro-4,5-dicyanophenoxy)-(1S)-1-cyano-1-methylethyl]-4-pentafluorothiobenzamide,

N-{(1-cyano-2-[4-cyano-2-(trifluoromethyl)phenoxy]-1-methylethyl }-4-pentafluorothiobenzamide,

N-{(1R)-1-cyano-2-[4-cyano-2-(trifluoromethyl)phenoxy]-1-methylethyl}-4-pentafluorothiobenzamide, and

N-{(1S)-1-cyano-2-[4-cyano-2-(trifluoromethyl)phenoxy]-1-methylethyl}-4-pentafluorothiobenzamide,

or a pharmaceutically acceptable salt thereof

7. A pharmaceutical composition comprising a compound of formula (I) of claim 1 , or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

8. The pharmaceutical composition according to claim 7 further comprising a second therapeutic agent.

9. The pharmaceutical composition according to claim 8 wherein the second therapeutic agent is selected from ivermectin, avermectin, abamectin, emamectin, eprinomectin, doramectin, selamectin, moxidectin, nemadectin, milbemycin oxime, albendazole, cambendazole, fenbendazole, flubendazole, mebendazole, oxfendazole, oxibendazole, parbendazole, tetramisole, levamisole, pyrantel pamoate, oxantel, morantel, closantel, triclabendazole, clorsulon, rafoxanide, niclosamide, praziquantel, epsiprantel, 2-desoxoparaherquamide, tipronil, pyriprole, pyrafluprole, lufenuron, spiromesifen, tebufenozide, spinosad, spinetoram, imidacloprid, dinotefuran, metaflumizone, thibendiamide, chlorantraniliprole, indoxacarb, pyridalyl, pyrimidifen and pyrifluquinazon.

10. A method of treatment of a parasitic infestation in a host animal, comprising treating said host animal with an effective amount of a compound of formula (I), or with a pharmaceutically acceptable salt or composition thereof, as defined in claim 1 .

11. The method according to claim 10 wherein the host animal is a non-human animal.

12. The method according to claim 10 wherein the parasite is a nematode.