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Isolation, identification and characterization of potential impurities in cabazitaxel and their formation

Taxanes, such as paclitaxel, docetaxel and cabazitaxel, were well known for their remarkable anti-tumor activities. They were presently applied and evaluated for ovarian, lung, breast and other gynecological cancers. According to International Conference on Harmonization (ICH) guidelines, the origin of all impurities (process and degradation) in drug substances should be understood completely and the level of the impurities should be controlled strictly for quality and safety considerations. The process impurities of taxanes were different because of the different manufacturing processes. However, the degradation impurities of taxanes had their regular patterns as all taxanes were the semisynthetic derivatives of 10-deacetylbaccatin III (10-DAB). Most degradation impurities formed at positon C-7, C-10, C-13, C-3 and C-11 of 10-DAB. β-OH at C-7 of taxanes can be easily epimerized into α-OH as result of retro-aldol process. β-OH at C-10 of taxanes can be oxygenated. The side chain at C-13 of taxanes can be lost. Furthermore, C-3 and C-11 of taxanes can be connected under photolytic condition via intramolecular hydrogen transfer from C-3 to C-12. Cabazitaxel (Jevtana@; Sanofi-Aventis) was a novel semisynthetic taxane drug. In June 2010, it was approved by the US Food and Drug Administration (FDA) for the treatment of patients with hormone-refractory metastatic prostate cancer that had been previously treated with docetaxel. Previous reports have shown the synthesis routes of cabazitaxel. However, no systematic impurity studies had been reported in the literature. The present study described the isolation and identification of the impurities of cabazitaxel. The formation mechanisms of these impurities were also investigated (Figures 1 and 2).