Solubility and Crystal Shape of Vonoprazan Fumarate in Monosolvents and Cosolvent Mixtures

Vonoprazan fumarate (VPF) is a novel potassium-competitive acid blocker that exhibits superior acid suppression compared to proton pump inhibitors. The solubility of VPF in water, methanol, ethanol, dimethylformamide, and mixed solvents of water + acetonitrile, water + acetone, methanol + acetone, and ethanol + acetonitrile was determined by a gravimetric method within the temperature range of 283.15–333.15 K under atmospheric pressure. The solubility data of VPF are positively related to the temperature in all selected solvents. In pure solvents, the solubility of VPF follows the order of DMF > methanol > ethanol > water. In the four cosolvent mixtures, the maximum solubility effect occurred as the solvent composition changed. The maximum values can be observed at x20 = 0.6 for water + acetonitrile and water + acetone mixtures, x20 = 0.8 for ethanol + acetonitrile, and x20 = 0.9 for methanol + acetone. The solubility data were fitted by the modified Apelblat model, van’t Hoff model, and modified Jouyban–Acree model. The modified Apelblat model had the best-fitting performance. The thermodynamic properties of the dissolution process were also calculated to interpret the solubility results. In addition, crystallization experiments were designed based on the solubility data. Single crystals of VPF were obtained, and the crystal structure was analyzed. Meanwhile, the crystal shape of VPF was also investigated, and the results show that the shape depends on both solvent type and solvent composition.