Pharmacologic properties, metabolism, and disposition of linaclotide, a novel therapeutic peptide approved for the treatment of irritable bowel syndrome with constipation and chronic idiopathic constipation.

Linaclotide, a potent guanylate cyclase C agonist, is a therapeutic peptide approved in the United States for the treatment of irritable bowel syndrome with constipation and chronic idiopathic constipation. We present for the first time the metabolism, degradation, and disposition of linaclotide in animals and humans. We examined the metabolic stability of linaclotide in conditions that mimic the gastrointestinal tract and characterized the metabolite MM-419447 (CCEYCCNPACTGC), which contributes to the pharmacologic effects of linaclotide. Systemic exposure to these active peptides is low in rats and humans, and the low systemic and portal vein concentrations of linaclotide and MM-419447 observed in the rat confirmed both peptides are minimally absorbed after oral administration. Linaclotide is stable in the acidic environment of the stomach and is converted to MM-419447 in the small intestine. The disulfide bonds of both peptides are reduced in the small intestine, where they are subsequently proteolyzed and degraded. After oral administration of linaclotide, <1% of the dose was excreted as active peptide in rat feces and a mean of 3-5% in human feces; in both cases MM-419447 was the predominant peptide recovered. MM-419447 exhibits high-affinity binding in vitro to T84 cells, resulting in a significant, concentration-dependent accumulation of intracellular cyclic guanosine-3',5'-monophosphate (cGMP). In rat models of gastrointestinal function, orally dosed MM-419447 significantly increased fluid secretion into small intestinal loops, increased intraluminal cGMP, and caused a dose-dependent acceleration in gastrointestinal transit. These results demonstrate the importance of the active metabolite in contributing to linaclotide's pharmacology.

Fatty acid amide hydrolase (FAAH) inhibition reduces L-3,4-dihydroxyphenylalanine-induced hyperactivity in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned non-human primate model of Parkinson's disease.

Dopaminergic therapies remain the most efficacious symptomatic treatments for Parkinson's disease (PD) but are associated with motor complications, including dyskinesia, and nonmotor complications, such as psychosis, impulse control disorders (ICD), and dopamine dysregulation syndrome (DDS). Nondopaminergic neurotransmitter systems, including the endocannabinoid system, are probably critical to the development of these complications. The role of fatty acid amide hydrolase (FAAH) in mediating l-3,4-dihydroxyphenylalanine (L-DOPA)-induced behaviors was explored in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned marmoset model of PD. Pharmacodynamic and locomotor effects of the selective FAAH inhibitor [3-(3-carbamoylphenyl)phenyl] N-cyclohexylcarbamate (URB597) were assessed via bioanalytical (liquid chromatography-tandem mass spectrometry) and behavioral observation approaches. URB597 (3, 10, 30, or 60 mg/kg p.o.) increased plasma levels of the FAAH substrates N-arachidonoyl ethanolamide (anandamide), N-oleoyl ethanolamide, and N-palmitoyl ethanolamide by 10.3 ± 0.3-, 7.8 ± 0.2-, and 1.8 ± 0.1-fold (mean of URB597 groups ± S.E.M.), respectively, compared with vehicle (all p < 0.001) 4 h after administration. Treatment with L-DOPA (20 mg/kg s.c.) alleviated parkinsonism but elicited dyskinesia, psychosis-like-behaviors and hyperactivity, a potential correlate of ICD and DDS. During the 2 to 4 h after L-DOPA, corresponding to 4 to 6 h after URB597 administration, URB597 reduced total L-DOPA-induced activity and the magnitude of hyperactivity by 32 and 52%, respectively, to levels equivalent to those seen in normal animals. Treatment with URB597 (10 mg/kg p.o.) did not modify the antiparkinsonian actions of L-DOPA or L-DOPA-induced dyskinesia and psychosis. URB597 did not alter plasma L-DOPA levels and was without behavioral effects when administered alone. Inhibition of FAAH may represent a novel approach to reducing L-DOPA-induced side effects, such as ICD and DDS, while maintaining the antiparkinsonian benefits of L-DOPA treatment.

Linaclotide, through activation of guanylate cyclase C, acts locally in the gastrointestinal tract to elicit enhanced intestinal secretion and transit.

Linaclotide is a first-in-class, orally administered 14-amino acid peptide that is in development for the treatment of irritable bowel syndrome with constipation and chronic constipation. We have characterized the solution structure of linaclotide, the in vitro binding and agonist activity to guanylate cyclase C receptors, the stability of linaclotide under conditions mimicking the gastric environment, oral bioavailability, and the pharmacodynamic effects in rat models of gastrointestinal transit and intestinal secretion. Nuclear magnetic resonance spectroscopy analysis determined that the molecular structure of linaclotide is stabilized by three intramolecular disulfide bridges. Linaclotide exhibited high affinity and pH-independent binding (K(i): 1.23-1.64 nM) to guanylate cyclase C receptors on human colon carcinoma T84 cells and concomitantly, linaclotide binding resulted in a significant, concentration-dependent accumulation of intracellular cyclic guanosine-3', 5'-monophosphate (cGMP) (EC50:99 nM). Linaclotide was stable after 3 h incubation in simulated gastric fluid (pH 1) and similarly, was completely resistant to hydrolysis by pepsin. Pharmacokinetic analysis of linaclotide showed very low oral bioavailability (0.1%). Orally administered linaclotide elicited a significant, dose-dependent increase in gastrointestinal transit rates in rats at doses of ≥5 µg/kg. Exposure of surgically ligated small intestinal loops to linaclotide induced a significant increase in fluid secretion, accompanied by a significant increase in intraluminal cGMP levels. These results suggest that the guanylate cyclase C agonist linaclotide elicits potent pharmacological responses locally in the gastrointestinal tract, and that orally administered guanylate cyclase C agonists may be capable of improving bowel habits in patients suffering from irritable bowel syndrome with constipation and chronic constipation.

Linaclotide is a potent and selective guanylate cyclase C agonist that elicits pharmacological effects locally in the gastrointestinal tract.

AIMS: Linaclotide is an orally administered 14-amino acid peptide being developed for the treatment of constipation-predominant irritable bowel syndrome (IBS-C) and chronic constipation. We determined the stability of linaclotide in the intestine, measured the oral bioavailability, and investigated whether the pharmacodynamic effects elicited in rodent models of gastrointestinal function are mechanistically linked to the activation of intestinal guanylate cyclase C (GC-C). MAIN METHODS: Linaclotide binding to intestinal mucosal membranes was assessed in competitive binding assays. Stability and oral bioavailability of linaclotide were measured in small intestinal fluid and serum, respectively, and models of gastrointestinal function were conducted using wild type (wt) and GC-C null mice. KEY FINDINGS: Linaclotide inhibited in vitro [(125)I]-STa binding to intestinal mucosal membranes from wt mice in a concentration-dependent manner. In contrast, [(125)I]-STa binding to these membranes from GC-C null mice was significantly decreased. After incubation in vitro in jejunal fluid for 30 min, linaclotide was completely degraded. Pharmacokinetic analysis showed very low oral bioavailability (0.10%). In intestinal secretion and transit models, linaclotide exhibited significant pharmacological effects in wt, but not in GC-C null mice: induction of increased fluid secretion into surgically ligated jejunal loops was accompanied by the secretion of elevated levels of cyclic guanosine-3',5'-monophosphate and accelerated gastrointestinal transit. SIGNIFICANCE: Linaclotide is a potent and selective GC-C agonist that elicits pharmacological effects locally in the gastrointestinal tract. This pharmacological profile suggests that orally administered linaclotide may be capable of improving the abdominal symptoms and bowel habits of patients suffering from IBS-C and chronic constipation.