The Factors Leading to Multiple Crystal Forms of Drug Compounds

Dear Colleagues,

The vast majority of drug compounds show a propensity for forming multiple crystal forms, each of which may show different physico-chemical characteristics due to variations in crystal lattice energies, leading to challenges in further development and formulation. Especially, the change in solubility between crystal forms can render the final medicine ineffective or even toxic, jeopardising the patient’s safety. The most prominent case highlighting these issues is undeniably Abbot’s ritonavir, but problems connected to crystal form issues have been reported for carbamazepine, mebendazole and rotigotine, to name but a few. Ab initio prediction of multiple crystal forms is possible but still time and cost intensive without giving detailed information about how to generate the predicted modifications. In addition, novel methods to sample non-ambient experimental spaces, e.g. high pressure and low temperature, open further dimensions to probe for new crystal forms and altered aggregation behaviour. Even though the problem of multiple crystal forms in drug compounds is widely known and tackled utilising a plethora of techniques by the community, ranging from experimental crystal form screening to in silico crystal form prediction, the factors leading to their formation are manifold, highly convoluted and not at all well understood.

The Special Issue on “The Factors Leading to Multiple Crystal Forms of Drug Compounds” is intended to provide a forum for novel research and discussion of the causes leading to this well-known and widely spread phenomenon. Scientists working in a wide range of disciplines are invited to contribute to this collection.

The topics presented in the keywords cover broadly the focus of this Special Issue. This issue is in particular inviting innovative contributions applying novel techniques to the long-standing problem of multiple crystal forms in the pharmaceutical sector.

Dr Katharina Edkins
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• Crystal polymorphism and solvent inclusion
• Molecular aggregation
• Amorphous structure
• Phase transition