Comprehensive experimental characterisation of solid-state properties and phenomena provides the basis for innovative optimisation strategies and new insights that are critical to the entire drug development process. This requires extensive systematic investigations and appropriate analytical methodology. The focus is on crystallisation experiments from solvent, melt or gas phase, where new polymorphic forms with the same composition but different crystal structures or solvent adducts are discovered for almost all active ingredients. The selection of the most suitable solid form for further development or the design of strategies to improve solubility and stability as well as processing properties is based on experimental data supplemented by computational methods. One successful strategy is the production of cocrystals, in which the active ingredient is combined with a biologically inactive excipient to form a new crystal form with, for example, improved solubility properties.
