UCSF

Background & aims

Constipation is a common clinical problem that negatively impacts quality of life and is associated with significant health care costs. Activation of the cystic fibrosis transmembrane regulator (CFTR) chloride channel is the primary pathway that drives fluid secretion in the intestine, which maintains lubrication of luminal contents. We hypothesized that direct activation of CFTR would cause fluid secretion and reverse the excessive dehydration of stool found in constipation.

Methods

A cell-based high-throughput screen was done for 120,000 drug-like, synthetic small molecules. Active compounds were characterized for mechanism of action and one lead compound was tested in a loperamide-induced constipation model in mice.

Results

Several classes of novel CFTR activators were identified, one of which, the phenylquinoxalinone CFTR_act-J027, fully activated CFTR chloride conductance with EC₅₀ ~ 200 nM, without causing elevation of cytoplasmic cAMP. Orally administered CFTR_act-J027 normalized stool output and water content in a loperamide-induced mouse model of constipation with ED₅₀ ~0.5 mg/kg; CFTR_act-J027 was without effect in cystic fibrosis mice lacking functional CFTR. Short-circuit current, fluid secretion and motility measurements in mouse intestine indicated a pro-secretory action of CFTR_act-J027 without direct stimulation of intestinal motility. Oral administration of 10 mg/kg CFTR_act-J027 showed minimal bioavailability, rapid hepatic metabolism and blood levels <200 nM, and without apparent toxicity after chronic administration.

Conclusions

CFTR_act-J027 or alternative small-molecule CFTR-targeted activators may be efficacious for the treatment of constipation.