Challenges in the Solid State Characterization of a Non-Conventional Pharmaceutical Hydrate

A hydrate, its dehydrated species, and mixtures of both were identified as the optimal forms for development of an API candidate. Characterization of these forms proved challenging during form selection activities due to their non-conventional solid state behavior. A variety of closely-related PXRD patterns was observed for different powder samples isolated from the same solvent/anti-solvent combination. An analogous behavior was observed for XRD patterns of slurry samples. It was determined that the differences in XRD patterns of the API, both in slurry and as bulk powder, were a reflection of water content and ambient relative humidity, respectively. This submission will describe how crystallization and drying studies were conducted, together with single crystal structure elucidation, solid state NMR, and rotating capillary XRD to understand the solid state behavior of this API candidate.