Use of QSPR Modeling to Characterize In Vitro Binding of Drugs to a Gut-Restricted Polymer

Purpose Polymeric drugs, including patiromer (Veltassa®), bind target molecules or ions in the gut, allowing fecal elimination. Non-absorbed insoluble polymers, like patiromer, avoid common systemic drug-drug interactions (DDIs). However, the potential for DDI via polymer binding to orally administered drugs during transit of the gastrointestinal tract remains. Here we elucidate the properties correlated with drug-patiromer binding using quantitative structure-property relationship (QSPR) models. Methods We selected 28 drugs to evaluate for binding to patiromer in vitro over a range of pH and ionic conditions intended to mimic the gut environment. Using this in vitro data, we developed QSPR models using step-wise linear regression and analyzed over 100 physiochemical drug descriptors. Results Four descriptors emerged that account for ~70% of patiromer-drug binding in vitro : the computed surface area of hydrogen bond accepting atoms, ionization potential, electron affinity, and lipophilicity ( R 2 = 0.7, Q 2 = 0.6). Further, certain molecular properties are shared by nonbinding, weak, or strong binding compounds. Conclusions These findings offer insight into drivers of in vitro binding to patiromer and describe a useful approach for assessing potential drug-binding risk of investigational polymeric drugs.