A compound represented by formula: a pharmaceutically acceptable salt or a solvate thereof, wherein R 1 is optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted cycloalkyl, optionally substituted cycloalkenyl, optionally substituted aryl, optionally substituted heteroaryl or optionally substituted heterocycle, one of R 2 and R 4 is a group of formula: -Y-R 5, wherein Y is -O-or -S -, and R 5 is substituted straight alkyl wherein the substituent of said substituted straight alkyl is cycloalkyl or cycloalkenyl, branched alkyl optionally substituted with hydroxy, carboxy or halogen, alkenyl optionally substituted with hydroxy, carboxy or halogen, alkynyl optionally substituted with hydroxy, carboxy or halogen, cycloalkyl optionally substituted with hydroxy, carboxy or halogen, cycloalkenyl optionally substituted with hydroxy, carboxy or halogen, aryl optionally substituted with hydroxy, carboxy or halogen, heteroaryl optionally substituted with hydroxy, carboxy or halogen or heterocycle optionally substituted with hydroxy, carboxy or halogen, the other of R 2 and R 4 is hydrogen, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted cycloalkyl, optionally substituted cycloalkenyl, optionally substituted aryl, optionally substituted heteroaryl or optionally substituted heterocycle, R 3 is a group of formula: -C(=O)-Z-R 6, wherein Z is -NR 7 - or -NR 7 -W-, and R 6 is cycloalkyl optionally substituted with hydroxy, carboxy, halogen, cyano, -CH 3, - CH 2 OH, -CH 2 OCONH 2, -CH 2 NH 2, -OCONH 2, -NHCOCH 3, -OCH 3, -NH 2, - NHSO 2 CH 3, -CONHCH 3, -OSO 2 NH 2, -NHSO 2 NH 2, -NHCOOCH 3, -CONH 2, -COOCH 3 or -CONHSO 2 CH 3, said cycloalkyl is selected from R 7 is hydrogen or optionally substituted alkyl, W is optionally substituted alkylene, X is =N- or =CR 8 -, and R 8 is hydrogen or optionally substituted alkyl, wherein "alkyl" means a C1 to C10 straight or branched alkyl group; "alkenyl" means a C2 to C8 straight or branched alkenyl group; "alkynyl" means a C2 to C8 straight or branched alkynyl group; "cycloalkyl" means a C3 to C15 saturated cyclic hydrocarbon group; "cycloalkenyl" means a C3 to C7 unsaturated aliphatic hydrocarbon group; "aryl" means phenyl or naphthyl; "heteroaryl" means furyl, thienyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetraz olyl, oxazolyl, isoxazolyl, thiazolyl, thiadiazolyl, isothiazolyl, pyridyl, pyridazinyl, pyrimidinyl, furazanyl, pyrazinyl, oxadiazolyl, benzofuryl, benzothienyl, benzimi dazolyl, dibenzofuryl, benzoxazolyl, quinoxalyl, cinnolyl, quinazolyl, quinolyl, pht halazinyl, isoquinolyl, puryl, pteridinyl, carbazolyl, phenanthridinyl, acridinyl, in dolyl, isoindolyl, phenazinyl or phenothiazinyl; "heterocycle" means 1-pyrrolinyl, 2-pyrrolinyl, 3-pyrrolinyl, 1-pyrrolidinyl, 2-pyrr olidinyl, 3-pyrrolidinyl, 1-imidazolinyl, 2-imidazolinyl, 4-imidazolinyl, 1-imidazoli dinyl, 2-imidazolidinyl, 4-imidazolidinyl, 1-pyrazolinyl, 3-pyrazolinyl, 4-pyrazoliny 1,1-pyrazolidinyl, 3-pyrazolidinyl, 4-pyrazolidinyl, piperidino, 2-piperidinyl, 3-pip eridinyl, 4-piperidinyl, 1-piperazinyl, 2-piperazinyl, 2-morpholinyl, 3-morpholinyl, morpholino, tetrahydropyranyl or the following groups