Identification of Potential Non-Systemic Therapeutics for Hyperammonemia

Abstract

A non-absorbable therapeutic candidate for the treatment of hyperammonemia has been identified and characterized. Conventional approaches to reducing ammonia concentration in the blood and colon include acidifying the colon, inhibiting the bacterial production of ammonia, and activation of the urea cycle. Addressing gaps in the literature around therapeutic ammonia adsorption, this study established assays for ammonia uptake from both NH4OH and NH4Cl solutions as well as interference and selectivity for potassium absorption. Performance was characterized for a large number and variety of materials, spanning zeolites, ion-exchange resins, metallopolymers, metal–organic frameworks (MOFs), and polymeric carboxylic acids. The latter class showed low potassium capacity (poly(acrylic acid): 10 mg/g, poly(maleic-co-acrylic acid): 4 mg/g) and a therapeutically relevant depression of pH in buffered simulated intestinal fluid (SIF) (poly(acrylic acid): −2.01 and poly(maleic-co-acrylic acid): −3.23) compared to lactulose (−3.46), an approved therapeutic for hyperammonemia that works by acidifying the colon. In the polymeric organic acids evaluated, pH depression correlated well with pKa and acid site density. Additionally, this class of candidates should avoid the undesirable side effects of lactulose, such as the potential for hyperglycemia in diabetic patients and incompatible use with galactosemic patients.

Keywords

• hyperammonemia
• zeolites
• ion-exchange resins
• polymeric organic acids
• metallopolymers
• metal–organic frameworks (MOFs)