Abstract: FR-PO234
Discovery of Small Molecule Drugs with Therapeutic Potential for Hyperoxalemia, Hyperoxaluria, and Related Kidney Stones
Session Information
- Mineral Bone Disease: Transplant and Kidney Stones
October 25, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Bone and Mineral Metabolism
- 501 Bone and Mineral Metabolism: Basic
Authors
- Hassan, Hatim A., Mayo Foundation for Medical Education and Research, Rochester, Minnesota, United States
- Subramaniam, Marina, Mayo Foundation for Medical Education and Research, Rochester, Minnesota, United States
- Dunne, Sara Fernandez, Northwestern University, Evanston, Illinois, United States
Background
Kidney stones (KS) are very common, excruciating, and account for >1.3M ER visits. ~80% of KS are composed of calcium oxalate and very small increases in urine oxalate significantly enhance the stone risk. Oxalate also potentially contributes to CKD and its progression, emphasizing the urgent need for plasma and urinary oxalate lowering therapies, which can be achieved by enhancing enteric oxalate secretion. We previously identified Oxalobacter-derived peptides stimulating oxalate transport by human intestinal Caco2-BBE (C2) cells via the oxalate transporters SLC26A6 [A6] & SLC26A2 [A2] and PKA activation. A main limitation of therapeutic peptides is their short half-life due to degradation by proteolytic enzymes. Many attempts to optimize our peptides decreased their functions by 45-100%. Small molecule (SM) therapeutics are superior to peptide-based drugs given their overall favorable drug profile.
Methods
To develop a cell-based high throughput screening (HTS) assay to identify SM activators for A6 and/or A2, Fischer rat thyroid (FRT) cells were engineered to stably co-express human A6 or A2 and a Cl-sensitive yellow fluorescent protein (YFP).
Results
A suitable HTS assay was successfully developed, in which extracellular addition of oxalate (Ox)-containing buffer drives A6/A2-mediated Cl/Ox exchange, leading to increased (dequenched) YFP fluorescence measured by a high content imager. The assay conditions were validated using the anion exchange inhibitors niflumic acid and DIDS, which inhibited the oxalate exchange. Addition of Ox did not change YFP fluorescence in control FRT cells (has YFP but no A6/A2). FDA-approved library was screened, and 24 drugs (22 in human clinical use; including 4 tyrosine kinase inhibitors and 7 drugs interacting with GPCRs) were identified as likely true positive hits, many of which serve as antagonists for pathways that we previously showed to inhibit A6-mediated intestinal oxalate transport. Interestingly, 22 drugs significantly stimulated (~17-107%) apical oxalate transport in C2 cells, with one drug had no effect and another significantly inhibited (~20.5%) oxalate transport.
Conclusion
Several SM drugs were discovered, which greatly stimulated oxalate transport by C2 cells and have significant potential to serve as novel therapeutics for hyperoxalemia, hyperoxaluria, and related KS.
Funding
- NIDDK Support