Prediction of Successful Amorphous Solid Dispersion Pairs through Liquid State Nuclear Magnetic Resonance

Amorphous solid dispersions (ASDs) function in part via a “parachute effect”, i.e., polymer-enabled prolonged drug supersaturation, presumably through drug–polymer interactions in the liquid state. We aim to expand the utility of liquid state nuclear magnetic resonance (¹HNMR) to streamline polymer selection for ASDs. Our hypothesis is that strong molecular interactions between polymer and drug in ¹HNMR anticipate reduced precipitation kinetics in supersaturation studies. For three drug–polymer pairs (i.e., etravirine with each HPMC, HPMCAS-M, and PVP-VA), ¹HNMR findings were compared to more common supersaturation studies. Drug–polymer interactions were assessed by saturation transfer difference NMR (STD-NMR) and T₁ relaxation time. 2D-¹H NOESY experiments were also performed. Supersaturation studies involved precipitation inhibition using the solvent-shift methodology. The results from STD-NMR and T₁ relaxation time indicate etravirine bound preferably to HPMCAS-M > HPMC ≫ PVP-VA. STD-NMR and T₁ relaxation time yielded insight into which fragments of etravirine structure bind with HPMCAS-M and HPMC. The strong interactions from STD-NMR and T₁ relaxation time changes indicated that HPMCAS-M and HPMC, but not PVP-VA, are suitable polymers to maintain etravirine supersaturation and inhibit drug precipitation. 2D-¹H NOESY results corroborate the findings of STD-NMR and T₁ relaxation time, showing that etravirine interacts preferably to HPMCAS-M than to PVP-VA. Supersaturation studies using solvent-shift technique corroborated our hypothesis as predissolved HPMCAS-M and HPMC, but to a less extent PVP-VA, markedly promoted etravirine supersaturation and inhibited drug precipitation. Supersaturation studies agreed with STD-NMR and T₁ relaxation time predictions, as HPMC and HPMCAS-M maintained etravirine in solution for longer time than PVP-VA. The results show promise of ¹HNMR to streamline polymer selection in a nondestructive and resource sparing fashion for subsequent ASD development.