FIELD: chemistry.SUBSTANCE: invention relates to field of organic chemistry, namely to novel heterocyclic compounds of general formula (I) or to their pharmaceutically acceptable salts, where X1 stands for N and X2, X3 and X4 stand for CR5； or X1 and X2 stand for N and X3 and X4 stand for CR5； or X1, X2 and X4 stand for CR5, and X3 stands for N； or X1, X2, X3 and X4 stand for CR5； R1 stands for (a) heteroaryl radical, selected from the group, including pyridinyl, 2-oxo-1,2-dihydropyridin-3-yl, 2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl, said heteroaryl optionally contains as substituents halogen, C1-C6-alkyl, C1-C6-hydroxyalkyl, C1-C3-alkoxy-C1-C3-alkyl, C1-C6-alkoxygroup, or (b) heterocyclic radical, selected from the group, including 2-oxotetrahydropyrimidin-1-yl, 2,6-dioxotetrahydropyrimidin-1-yl, 2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-yl and 2,4-dioxotetrahydropyrimidin-1-yl； R2 stands for hydrogen or C1-C6-alkoxygroup； R3 stands for (a) phenyl, (b) pyridine, where said phenyl or said pyridine independently optionally contain 1-3 substituents, selected from the group, including halogen, (CH2)nNRcRd, or (c) NRaRb, (d) hydrogen, (e) halogen； Ra and Rb together with nitrogen atom, which they are bound to, form cyclic amine, containing from 3 to 5 carbon atoms, independently substituted with group (CH2)nNReRf； Rc and Rd independently stand for hydrogen, SO2R8, where R8 stands for C1-C6-alkyl； Re and Rf independently stand for hydrogen, SO2R8, where R8 stands for C1-C6-alkyl； R4 stands for CF3, CH2CF3 or CR4aR4bR4c, where (i) R4a, R4b and R4c are independently selected from the group, including C1-C3-alkyl, CD3； or (ii) taken together R4a and R4b form C2-C4-alkylene and R4c stands for cyanogroup or C1-C2-fluoroalkyl； R5 in each case independently stands for hydrogen, halogen, C1-C6-alkoxygroup or C1-C6-alkyl； n in each case independently equals 0-3. Invention also related to method of treating infection with hepatitis C virus, method of inhibiting HCV replication, app
