Crystal Structure Prediction in the Context of Pharmaceutical Polymorph Screening and Putative Polymorphs of Ciprofloxacin

Abstract

Molecular simulation is increasingly used by medicinal chemists in the process and product development. Reliable computational predictions are of great value not only for the design of an active pharmaceutical ingredient with novel properties but also for the avoidance of an undesirable change of form in the late stages of development of an industrially important molecule. In the pharmaceutical industry, drug polymorphism can be a critical problem and is the subject of various regulatory considerations. This contribution tried to review the fuzzy frontiers between the chemical structure of the molecule and its crystal energy landscape with a particular focus on the crystal structure prediction (CSP) methodology to complement polymorph screening. A detailed application of CSP in the pharmaceutical industry is illustrated on ciprofloxacin; describing its putative polymorphs. This approach successfully identifies the known crystal form within this class, as well as a large number of other low-energy structures. The performance of the approach is discussed in terms of both the quality of the results and computational aspects. CSP methods are now being used as part of the interdisciplinary range of studies to establish the range of solid forms of a molecule. Moreover, further methodological improvements aimed at increasing the accuracy of the predictions and at broadening the range of molecules i.e. co-crystals, salts and solvates.

Chemistry for Space Group Symmetry beyond Crystals

“…They discuss crystallization, diastereomers, chiral crystals of achiral compounds, etc., which are also related to classical natural crystallization. Focusing on conformational changes and polymorphisms of organic compounds (of pharmaceutical importance), Singh et al [12] reported in 2017 on space group frequency as information necessary for crystal structure prediction.…”