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  = 0.7, Q  = 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.