Project Summary/Abstract Kidney stones (KS) are highly prevalent, excruciating, and associated with long term complications of chronic kidney disease (CKD) and end stage renal disease (ESRD). They account for 1.3M ER visits and >$10B of medical costs annually and have a striking recurrence rate of 50% in 5 years and up to 80% in 10 years, reflecting the inadequacies of current interventions. 70-80% of KS are composed of calcium oxalate and small increases in urine oxalate significantly enhance the risk for stone development. Reducing urine oxalate levels results in a lower CaOx supersaturation and decreased KS recurrence. No approved drugs can specifically reduce urine oxalate. The gut bacterium Oxalobacter formigenes (Of) induces colonic oxalate secretion and reduces urinary oxalate excretion via an unknown secretagogue. Use of Of as a therapeutic agent remains problematic given difficulties with recolonization, underscoring the need to identify the factors inducing colonic oxalate secretion. Oxalo Therapeutics has shown that Of-derived factors, by itself, significantly reduced urinary oxalate in hyperoxaluric mice by >32.5% and identified a family of signaling proteins as the major Of-derived factors. These proteins and a series of identified peptides also significantly stimulated oxalate transport by C2 cells. Importantly several peptides also similarly stimulated oxalate transport by human organoids (an ex vivo intestinal epithelium model fully mimicking the gut), underscoring the human relevance. Through this STTR Fast-track proposal, Oxalo Therapeutics aims to develop an oral drug based on these peptides to prevent KS by lowering oxalate in the urine and blood. Specific aims for Phase I: 1. Optimize lead peptides for stability using structural modifications, 2. Evaluate the therapeutic effects of the optimized peptides in primary hyperoxaluria (PH1) mouse model. Optimized peptide(s) that significantly reduce urine & plasma oxalate levels will be taken to Phase II. Specific aims for Phase II, 1. Develop novel peptides (NP) based on modeling of the identified crystal structures, 2. Evaluate the effects of the optimized peptides or NPs in reducing urine & plasma oxalate levels in PH1 mice and enteric (secondary) hyperoxaluria mice, 3. Develop enteric coated capsules containing best performing peptides for oral administration and evaluate effects on the above mice. 4. Perform preclinical toxicology and pharmacokinetics studies in rats and nonhuman primates. Since ~ 50% of urine oxalate is derived from diet and ~50% comes from the liver, the Oxalo product has a mechanistic advantage over competitors by addressing both sources (by extracting oxalate from blood and enhancing its intestinal excretion). Competitors are developing drugs that only target either dietary oxalate or liver oxalate. By lowering plasma oxalate levels, there are also therapeutic implications for hyperoxalemia seen in ESRD, & CKD, and the genetic disease primary hyperoxaluria...