Uric Acid Crystallization Interrupted with Competing Binding Agents

Uric acid crystallization in humans is associated with undesirable medical conditions including the formation of gout deposits and kidney stones. A major contributing factor to uric acid biomineralization, most often as either monosodium urate (MSU) or anhydrous uric acid (UA), is its relatively low solubility in physiologic solutions. Using bidentate and tridentate binding patterns designed to disrupt the binding motifs observed in the major physiologic forms, several heterocycles were identified which (1) significantly delay the time required for visible uric acid crystals to appear and/or (2) yield new 1:1 uric acid cocrystal phases. All five of the new phases obtained exhibited a multidentate hydrogen bonding motif between components. Fluorescence assays showed that three of the cocrystals were 3–6× more soluble than the natural forms. The same competitive-binding approach was then extended to trimethoprim, an FDA-approved drug with the same substructure as the most effective binding agents. Addition of trimethoprim to uric acid solutions significantly delayed the crystallization times and also yielded a new cocrystal form with a solubility greater than MSU. These results serve to illustrate the potential benefits of repurposing existing pharmaceuticals to treat uric acid diseases.