Stable Cocrystals and Salts of the Antineoplastic Drug Apatinib with Improved Solubility in Aqueous Solution

Apatinib (APA) belongs to the targeted antineoplastic family of drugs by inhibiting the vascular endothelial cell growth factor receptor (VEGFR-2) of tyrosine kinase. APA encounters poor aqueous solubility problems, and its therapeutic dosage form, apatinib mesylate (ATM), is unstable and dissociates completely to APA in aqueous solution. Here, we synthesized and evaluated three new cocrystals of APA with adipic acid (APA + ADA), sebacic acid (APA + SEA), and D/L-mandelic acid (APA + D/L-MA), and four new salts with succinic acid (APA + SUA-H2O), salicylic acid (APA + SA), 1-hydroxy-2-naphthoic acid (APA + HNA), and saccharin (APA + SAC). All the solid forms were characterized by powder X-ray diffraction, infrared spectroscopy, differential scanning calorimetry, and dynamic vapor sorption. The molecular components and structures were confirmed by single crystal X-ray diffraction. APA + SEA is able to overcome the instability problem and has improved solubility compared with ATM. Hence, APA + SEA has the potential to be a superior candidate for this important drug.