A compound of formula (I): ** Formula ** where R 1 is hydrogen, methyl, phenyl, pyrazolyl or hydroxyl； R2 is hydrogen, alkyl, alkenyl,>； = CH2 or>； = CHRc where the alkyl group and the alkenyl group are substituted with 0, 1, 2 or 3 substituents independently selected from the group consisting of alkoxycarbonyl, alkylcarbonyloxy, aryl, aryloxy , arylalkoxy, carboxy, cyano, cycloalkyl, haloalkoxy, heteroaryl, heterocycle, hydroxyl, nitro and RdReN-, where a group represented by R2 may be further substituted with 0, 1 or 2 groups chosen from halo and alkoxy； Rc is alkyl or halo； Rd and Re are each independently hydrogen, alkyl, alkoxyalkyl, aryl, arylalkyl, cyanoalkyl, heteroaryl, heteroarylalkyl, heterocycle or heterocycloalkyl； R3 is -G1-L-G2； G1 is aryl or heteroaryl； G2 is aryl, cycloalkyl, heteaoaryl, or heterocycle； L is a bond, O, alkylene, or -O-alkylene-； R4 is optionally substituted alkyl, cycloalkyl, heteroaryl, heterocycle or NR5R6； where, R5 and R6 are independently hydrogen, alkyl, (NRiRj) alkyl, alkynyl, aryl, heterocycloalkyl, cycloalkylalkyl, cyanoalkyl, cycloalkyl, alkoxyalkyl, arylalkyl, or heteroarylalkyl； and a is a single bond or a double bond； with the proviso that when R1 is hydroxyl or when R2 is a radical attached to the thiazole ring through an exocyclic double bond, then a is a single bond； and with the proviso that when a is a double bond, R1 is hydrogen, R2 is methyl, R3 is phenyl substituted with 3-haloalkyl, 3-halo, 3-haloalkoxy, 2,5-dihalo, 2,3-dihalo, 3,4-dihalo or 3,5-dihalo, then R4 is heterocycle； or a pharmaceutically acceptable salt, ester or amide thereof.Un compuesto de fórmula (I):**Fórmula** donde R1 es hidrógeno, metilo, fenilo, pirazolilo o hidroxilo； R2 es hidrógeno, alquilo, alquenilo, >；=CH2 o >；=CHRc donde el grupo alquilo y el grupo alquenilo están sustituidos con 0, 1, 2 ó 3 sustituyentes elegidos independientemente de entre el grupo que consiste en alcoxicarbonilo, alquilcarboniloxi, arilo, ariloxi, arilalcox
