Nanomolar Potency Pyrimido-pyrrolo-quinoxalinedione CFTR Inhibitor Reduces Cyst Size in a Polycystic Kidney Disease Model

Abstract

Inhibitors of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel are predicted to slow cyst enlargement in polycystic kidney disease and reduce intestinal fluid loss in secretory diarrheas. Screening of ~110000 small synthetic and natural compounds for inhibition of halide influx in CFTR-expressing epithelial cells yielded a new class of pyrimido-pyrrolo-quinoxalinedione (PPQ) CFTR inhibitors. Testing of 347 analogues established structure–activity relationships. The most potent compound, 7,9-dimethyl-11-phenyl-6-(5-methylfuran-2-yl)-5,6-dihydro-pyrimido-[4′,5′-3,4]pyrrolo[1,2-a]quinoxaline-8,10-(7H,9H)-dione, PPQ-102, completely inhibited CFTR chloride current with IC50 ~90 nM. The PPQs, unlike prior CFTR inhibitors, are uncharged at physiological pH, and therefore not subject to membrane potential-dependent cellular partitioning or block efficiency. Patch-clamp analysis confirmed voltage-independent CFTR inhibition by PPQ-102 and showed stabilization of the channel closed state. PPQ-102 prevented cyst expansion and reduced the size of preformed cysts in a neonatal kidney organ culture model of polycystic kidney disease. PPQ-102 is the most potent CFTR inhibitor identified to date.

SLC26 anion exchangers of guinea pig pancreatic duct: molecular cloning and functional characterization

“…CFTR inhibitors Inh-172 (10 M) and GlyH101 (10 M) each inhibited both gpSlc26a3 and gpSlc26a6-mediated Cl Ϫ uptake (Table 2), and gpSlc26a6 inhibition by GlyH101 exhibited concentration dependence. However, gpSlc26a3 and gpSlc26a6 were insensitive to 10 M of the novel CFTR inhibitor PPQ-102 (55). In contrast, gpSlc26a11-mediated Cl Ϫ uptake was inhibited ϳ80% by GlyH101 (10 M) or PPQ-102 (10 M).…”

“…gpSlc26a11 shared H 2 -DIDS sensitivity with human SLC26A11 (57) and exhibited, in addition, strong inhibition by niflumic acid ( Table 2). gpSlc26a3 and gpSlc26a6 were sensitive to CFTR inhibitors Inh-172 and GlyH101 but insensitive to PPQ-102 (55). However, gpSlc26a11 was distinguished from gpSlc26a3 and gpSlc26a6 by its sensitivity to PPQ-102 (Table 2).…”

Strategies Targeting cAMP Signaling in the Treatment of Polycystic Kidney Disease

“…85 PKA-induced phosphorylation of the cystic fibrosis transmembrane conductance regulator (CFTR) in the apical membrane opens the channel and allows the flow of chloride ions down an electrochemical gradient into the cyst, generating increased transepithelial electron activity that, in turn, drives sodium ions through paracellular pathways. The role of CFTR in PKD is supported by whole-cell patch-clamp studies of cyst-derived epithelial cells, inhibition of fluid secretion by CFTR antisense oligonucleotides, inhibition of cyst growth in in vitro and in vivo models of cystogenesis, [86][87][88][89][90] and the milder cystic phenotype in patients affected by both ADPKD and cystic fibrosis. [91][92][93][94] However, an additional patient with coexisting ADPKD and cystic fibrosis progressed to ESRD after a lung transplant, possibly because of cyclosporin toxicity, and the disease severity of bpk CFTR double mutant mice was not less than the disease severity of bpk mice, a rapidly progressive model of PKD.…”

Novel Therapies for Polycystic Kidney Disease

“…CFTR inhibition is another recent focus of research for agents that inhibit renal cystic disease. Small molecule inhibitors of CFTR inhibited the development of PKD in a rodent model [65,66]. PPAR-gamma activators have been shown to inhibit vasopressin mediated chloride transport via CFTR [67] and have been shown to inhibit renal cystic disease in rat models of PKD [68][69][70].…”