Method for determining the amount of taxane conjugate PGA-taxane conjugates acid.

Method for determining the relative amount of a taxane and of each impurity contained in a taxane conjugate PGA-taxane acid, wherein one or more taxane molecules are linked through the 2'-position hydroxyl group γ-carboxyl of α-poly-L-glutamic acid, said method comprising the steps of: a) reacting the polyglutamic-taxane conjugate acid with a compound of formula (I): R1 R2 N-NH2 (I) wherein R 1 and R 2 are independently C1-C10, C1-C10 hydroxyalkyl, C3-C10, C3-C10 hydroxyalkyl, C3-C10 alkynyl, C3-C10 hydroxyalkynyl, aryl, heteroaryl; or R 1 and R 2 taken together with the nitrogen atom to which they are attached form a heterocyclic ring of 3- 8-membered optionally containing up to three heteroatoms selected from O, S and N and optionally substituted with up to two hydroxyl groups; to provide a mixture containing conjugate PGA-taxane unreacted acid, unbound taxanes and polyglutamic acid hydrazide; b) removing the conjugated taxane poliglutamico- unreacted acid from the mixture obtained in a) to provide a solution comprising unbound taxanes; c) injecting the solution obtained in b) on a liquid chromatography HPLC and determining the percent area of ​​said taxane and of each taxane impurity; d) transforming percentage areas obtained in c) in the relative amounts of taxane and of each taxane impurity.