Use of acetylated tubulin as a biomarker for predicting the response to a compound, wherein the compound is a compound of general formula I wherein R represents phenyl, thienyl or pyridinyl wherein phenyl is optionally substituted by one or two substituents independently selected from alkyl, halo-lower alkyl, hydroxy-lower alkyl, lower alkoxy-lower alkyl, acyloxy-lower alkyl, phenyl, hydroxy, lower alkoxy, hydroxy-lower alkoxy, lower alkoxy-lower alkoxy, phenyl-lower alkoxy, lower alkylcarbonyloxy, amino, monoalkylamino, dialkylamino, lower alkoxycarbonylamino, lower alkylcarbonylamino, substituted amino wherein the two substituents on nitrogen form together with the nitrogen heterocyclyl, lower alkylcarbonyl, carboxy, lower alkoxycarbonyl, cyano, halogen, and nitro; and wherein two adjacent substituents are methylenedioxy; and wherein pyridinyl is optionally substituted by lower alkoxy, amino or halogen; X represents a group C=Y, wherein Y stands for oxygen or nitrogen substituted by hydroxy or lower alkoxy; R 1 represents hydrogen, lower alkylcarbonyl, hydroxy-lower alkyl or cyano-lower alkyl; R 2, R 3 and R 6 represent hydrogen; R 4 and R 5, independently of each other, represent hydrogen, lower alkyl or lower alkoxy; or R 4 and R 5 together represent methylenedioxy; and pharmaceutically acceptable derivatives thereof, wherein the pharmaceutically acceptable derivative is selected from the group consisting of a salt, solvate, in vivo hydrolysable ester or amide of the said compound, salt of such in vivo hydrolysable ester or amide, and polymorph of the said compound; or wherein R represents phenyl or pyridinyl wherein phenyl is optionally substituted by one or two substituents independently selected from alkyl, halo-lower alkyl, hydroxy-lower alkyl, lower alkoxy-lower alkyl, acyloxy-lower alkyl, phenyl, hydroxy, lower alkoxy, hydroxy-lower alkoxy, lower alkoxy-lower alkoxy, phenyl-lower alkoxy, lower alkylcarbonyloxy, amino, monoalkylamino, dialkylamino, lower alkoxycarbonylamino, lower alkylcarbonylamino, substituted amino wherein the two substituents on nitrogen form together with the nitrogen heterocyclyl, lower alkylcarbonyl, carboxy, lower alkoxycarbonyl, formyl, cyano, halogen, and nitro; and wherein two adjacent substituents are methylenedioxy; and wherein pyridinyl is optionally substituted by lower alkoxy, amino or halogen; X represents oxygen; R 1 represents hydrogen, lower alkylcarbonyl, hydroxy-lower alkyl or cyano-lower alkyl; R 2, R 3 and R 6 represent hydrogen; R 4 and R 5, independently of each other, represent hydrogen, lower alkyl or lower alkoxy; or R 4 and R 5 together represent methylenedioxy; and pharmaceutically acceptable derivatives thereof, wherein the pharmaceutically acceptable derivative is selected from the group consisting of a salt, solvate, in vivo hydrolysable ester or amide of the said compound, salt of such in vivo hydrolysable ester or amide, and polymorph of the said compound, and wherein the prefix lower denotes a radical having up to and including a maximum of 7, especially up to and including a maximum of 4 carbon atoms; and wherein the response is of a disease in a subject and the biomarker acetylated tubulin is measured ex vivo in a sample or samples taken from the human or animal body, preferably taken from the human body. R represents phenyl, thienyl or pyridinyl wherein phenyl is optionally substituted by one or two substituents independently selected from alkyl, halo-lower alkyl, hydroxy-lower alkyl, lower alkoxy-lower alkyl, acyloxy-lower alkyl, phenyl, hydroxy, lower alkoxy, hydroxy-lower alkoxy, lower alkoxy-lower alkoxy, phenyl-lower alkoxy, lower alkylcarbonyloxy, amino, monoalkylamino, dialkylamino, lower alkoxycarbonylamino, lower alkylcarbonylamino, substituted amino wherein the two substituents on nitrogen form together with the nitrogen heterocyclyl, lower alkylcarbonyl, carboxy, lower alkoxycarbonyl, cyano, halogen, and nitro; and wherein two adjacent substituents are methylenedioxy; and wherein pyridinyl is optionally substituted by lower alkoxy, amino or halogen; X represents a group C=Y, wherein Y stands for oxygen or nitrogen substituted by hydroxy or lower alkoxy; R 1 represents hydrogen, lower alkylcarbonyl, hydroxy-lower alkyl or cyano-lower alkyl; R 2, R 3 and R 6 represent hydrogen; R 4 and R 5, independently of each other, represent hydrogen, lower alkyl or lower alkoxy; or R 4 and R 5 together represent methylenedioxy;