Docetaxel (Taxotere^® Trihydrate) Forms: Crystal Structure Determination from XRPD & XRSCD Data

Docetaxel (form A), a stoichiometric hydrate containing three water molecules per molecule of drug substance (Taxotere^®), is thermodynamically stable under ambient conditions of pressure, temperature and relative humidity. In order to gain a better understanding of docetaxel system at the atomic scale a structural study was performed. Due to strong anisotropy of crystals (thin plates), the crystal structure of docetaxel (29 degrees of freedom) was solved and refined using high resolution XRPD data applying an ab initio direct space method. In parallel, an in-depth crystal growth study was carried out until single crystals suitable for XRSCD structural resolution were obtained: surprisingly, a new polymorph of docetaxel, called form B, was isolated.