Khyle C. Richards-Corke

Hyperammonemia is characterized by the accumulation of ammonia within the bloodstream upon liver injury. Left untreated, hyperammonemia contributes to conditions such as hepatic encephalopathy that have high rates of patient morbidity and mortality. Previous studies have identified gut bacterial urease, an enzyme that converts urea into ammonia, as a major contributor to systemic ammonia levels. Here, we demonstrate use of benurestat, a clinical candidate used against ureolytic organisms in encrusted uropathy, to inhibit urease activity in gut bacteria. Benurestat inhibits ammonia production by urease-encoding gut bacteria and is effective against individual microbes and complex gut microbiota. When administered to conventional mice with liver injury induced by thioacetamide exposure, benurestat reduced gut and serum ammonia levels and rescued 100% of mice from lethal acute liver injury. Overall, this study provides an important proof-of-concept for modulating host ammonia levels and microbiota-driven risks for hyperammonemia with gut microbiota-targeted small-molecule inhibitors.

Significance: Oncogenic Ras isoforms are the subject of intense study due to the difficulty in targeting these biomedically important yet “undruggable” proteins. Recent success in covalent targeting of a Ras mutant illustrates avenues for ligand design; however, many mutant Ras forms do not feature appropriately-placed nucleophiles, suggesting that strategies for noncovalent engagement of Ras are required. We report the design of a conformationally-defined proteomimetic that reproduces a key binding surface of Sos, a well-characterized effector of Ras. The proteomimetic binds wild-type and various mutant forms of Ras and modulates downstream signaling. Significantly, the compound shows enhanced internalization and selective toxicity toward cancer cells that up-regulate macropinocytosis. We anticipate these studies will foster new therapeutic modalities to engage mutant Ras.