Physicochemical Properties of Pharmaceutical Co-Crystals: A Case Study of Ten AMG 517 Co-Crystals

The pharmaceutical co-crystal approach has been introduced recently to address poor physicochemical properties of new chemical entities. In this study we prepared and investigated ten co-crystals of AMG 517. Based on thermal analysis, 1H NMR and pKa values we have prepared co-crystals rather than solvates or salts. We explored co-crystal physicochemical properties such as particle size, solubility, stability, hygroscopicity, and thermal properties as well as hydrogen bonding networks. We found that all co-crystals, for which we obtained single crystal structure, had the same two hydrogen bonds between the compound and the co-crystal former. In addition, we found good correlation between the melting point of the co-crystal former and the co-crystal but less correlation between the melting point and solubility of the co-crystals. In conclusion, within this series of co-crystals some design is possible by considering features of the compound and the co-crystal former.