Co-Amorphous Solid Dispersion System for Improvement in Dissolution Profile of N-(((1r,4r)-4-((6-fluorobenzo[d]oxazol-2-yl)amino)cyclohexyl)methyl)-2-methylpropane-2-sulfonamide as a Neuropeptide Y5 Receptor Antagonist

<b>Background/Objectives:</b> Brick dust molecules exhibit high melting points and ultralow solubility. Overcoming this solubility issue is challenging. Previously, we formulated a co-amorphous system for a neuropeptide Y5 receptor antagonist (NP) as a brick dust drug using sodium taurocholate (ST) to improve its dissolution profile. In this study, we have designed a ternary amorphous system involving polymer addition to further improve a co-amorphous system. <b>Methods:</b> The amorphous samples were prepared by the ball milling. The thermal and spectroscopic analyses were performed, and the isothermal crystallization and dissolution profiles were evaluated. <b>Results:</b> The ball milling of NPs, ST, and each of the three types of polymers successfully converted crystalline NPs to amorphous NPs. Thermal analysis confirmed the formation of a single amorphous phase. The infrared spectra revealed a specific interaction between an NP and ST in the co-amorphous system. Moreover, the intermolecular interactions of NP-ST were maintained in the ternary amorphous systems, suggesting the miscible dispersion of the co-amorphous system into the polymer via weak interactions as co-amorphous solid dispersions. The dissolution profile of co-amorphous NP-ST was 4.1- and 6.7-fold higher than that of crystalline NPs in pH 1.2 and 6.8 buffers, respectively. The drug concentration in the ternary amorphous system in pH 1.2 and 6.8 buffers became 1.1-1.2- and 1.4-2.7-fold higher than that seen in the co-amorphous system, respectively. <b>Conclusions:</b> Co-amorphous solid dispersion is a promising method for enhancing the solubility of brick dust molecules.