Using Acetone/Water Binary Solvent to Enhance the Stability and Bioavailability of Spray Dried Enzalutamide/HPMC-AS Solid Dispersions.

We demonstrated a facile approach, by adjusting the solvent ratio of water/acetone binary mixture, to alter the intermolecular interactions between Enzalutamide (ENZ) and hydroxypropyl methylcellulose acetate succinate (HPMC-AS) for spray drying process, which can be readily implemented to produce spray-dried dispersions (SDD) with enhanced stability and bioavailability. The prepared SDD of ENZ/HPMC-AS were examined systematically in terms of particle size, morphology, dissolution, solubility, stability, and bioavailability. Our results show that the introduction of water (up to 30% volume fraction) can effectively reduce the hydrodynamic diameter of HPMC-AS from approximately 220 nm to 160 nm (a reduction of c.a. 20%), which increases the miscibility of the drug and polymer, delaying or inhibiting the crystallization of ENZ during the spray drying process, resulting in a homogeneous amorphous phase. The benefits of using acetone/water binary mixture were subsequently evidenced by an increased specific surface area, improved dissolution profile and relative bioavailability, enhanced stability, and elevated drug release rate. This fundamental finding underpins the great potential of using binary mixture for spray drying process to process active pharmaceutical ingredients (APIs) that are otherwise challenging to handle.