ornithine-phenylacetate and Liver-Cirrhosis

Hepatic encephalopathy is one of the most debilitating clinical manifestations of cirrhosis and associated with increased morbidity and mortality. Treatment modalities available include the nonabsorbable disaccharides (lactulose) and the nonabsorbable antibiotics (rifaximin).. Newer therapeutic targets under evaluation include ammonia scavengers (ornithine phenylacetate) and modulation of gut microbiota (fecal microbiota transplantation).. This review will focus on the pathophysiology of hepatic encephalopathy along with an update on therapeutic targets under investigation.

Topics: Amino Acids, Aromatic; Amino Acids, Branched-Chain; Ammonia; Dipeptides; Fecal Microbiota Transplantation; Frailty; Gastrointestinal Agents; Gastrointestinal Microbiome; Glycerol; Hepatic Encephalopathy; Humans; Hypertension, Portal; Lactulose; Liver Cirrhosis; Ornithine; Phenylbutyrates; Polyethylene Glycols; Probiotics; Rifaximin; Trace Elements; Zinc

Hepatic encephalopathy (HE) is a serious neuropsychiatric complication of cirrhosis and/or porto-systemic shunting. The clinical symptoms are widely variable, extending from subtle impairment in mental state to coma. The utility of categorizing the severity of HE accurately and efficiently serves not only to provide practical functional information about the current clinical status of the patient but also gives valuable prognostic information. In the past 20-30 years, there has been rapid progress in understanding the pathophysiological basis of HE; however, the lack of direct correlation between pathogenic factors and the severity of HE make it difficult to select appropriate therapy for HE patients. In this review, we will discuss the classification system and its limitations, the neuropsychometric assessments and their challenges, as well as the present knowledge on the pathophysiological mechanisms. Despite the many prevalent hypotheses around the pathogenesis of the disease, most treatments focus on targeting and lowering the accumulation of ammonia as well as inflammation. However, treatment of minimal HE remains a huge unmet need and a big concerted effort is needed to better define this condition to allow the development of new therapies. We review the currently available therapies and future approaches to treat HE as well as the scientific and clinical data that support their effectiveness.

Topics: Albumins; Ammonia; Anti-Bacterial Agents; Bile Acids and Salts; Brain; Brain Edema; Cognitive Dysfunction; Dipeptides; Energy Metabolism; Gastrointestinal Agents; Hepatic Encephalopathy; Humans; Lactulose; Liver Cirrhosis; Ornithine; Portasystemic Shunt, Surgical; Prognosis; Psychometrics; Severity of Illness Index; Synaptic Transmission

Topics: Albumins; Amino Acids; Diagnosis, Differential; Diet; Disaccharides; Drug Resistance; Electroencephalography; Glycerol; Hepatic Encephalopathy; Humans; Liver Cirrhosis; Magnetic Resonance Imaging; Neomycin; Neurologic Examination; Nucleic Acid Synthesis Inhibitors; Ornithine; Phenylbutyrates; Probiotics; Protein Synthesis Inhibitors; Rifamycins; Rifaximin; Terminal Care; Tomography, X-Ray Computed

In patients with liver failure hyperammonemia is associated with the development of hepatic encephalopathy (HE) and immune impairment. Treatment of hyperammonemia is an unmet clinical need. Ornithine phenylacetate (OP) is a novel drug that is targeted at reducing ammonia concentration in patients with liver disease and therefore a potential treatment for HE. This review describes the mechanism of action of OP and its effect on plasma ammonia levels, brain function and inflammation of OP in both acute and chronic liver failure. Ammonia levels could shown to be reduced for up to 24 h in animal models until 120 h in patients with repeated dosing of the drug. Reduction of plasma ammonia levels is due to the stimulation of ammonia removal in the form of glutamine (through glutamine synthetase), the direct excretion of ammonia in the form phenylacetylglutamine and to a normalisation of glutaminase activity in the gut. Administration of OP is associated with a reduction of brain oedema in rats with chronic bile duct ligation and diminution of intracranial hypertension in a pig model of ALF. Studies to date have indicated that it is safe in humans and trials in overt HE are underway to establish OP as a treatment for this major complication of liver disease.

Topics: Animals; Brain; Hepatic Encephalopathy; Humans; Hyperammonemia; Liver Cirrhosis; Liver Diseases; Liver Failure; Ornithine; Rats

Hepatic encephalopathy (HE) is associated with increased morbidity, mortality, and health care resource use. In this phase 2b study, we evaluated the efficacy and safety of ornithine phenylacetate (OP), an ammonia scavenger, in hospitalized patients with cirrhosis, increased levels of ammonia at screening, and acute or overt HE.. We conducted a double-blind study of 231 patients with cirrhosis and HE at multiple sites in North America, Europe, Israel, and Australia from January 7, 2014, through December 29, 2016. Patients were assigned randomly to groups that received placebo or OP (10, 15, or 20 g/d, based on the severity of liver disease), plus each institution's standard of care (eg, lactulose to achieve 2-3 bowel movements with or without rifaximin, in accordance with guidelines). The primary end point was time to confirmed clinical response, defined as reduction to HE staging tool (HEST) stage 2 from baseline HEST stages 3/4 or improvement to HEST stages 0/1 from baseline stage 2, in the intent-to-treat population (all patients with increased levels of ammonia at screening, determined by a local laboratory).. Median times to clinical improvement, based on ammonia measurements at local laboratories, did not differ significantly between the groups given OP vs the placebo group (P = .129). Analyses of central laboratory-confirmed increases in levels of ammonia at baseline (n = 201) showed clinical improvement in HE at a median of 21 hours sooner in groups given OP vs placebo. The percentages of patients with any specific adverse event did not differ significantly between groups. Serious adverse events occurred in 25% of patients in the OP group and in 29% in the placebo group (P = .552).. In a randomized controlled trial of patients with cirrhosis and HE, we found no significant difference in time to clinical improvement between patients given OP vs placebo. However, OP appears to be safe and should undergo further testing for treatment of hyperammonemia in hospitalized patients receiving treatment for the underlying precipitant of acute or overt HE. ClinicalTrials.gov no: NCT01966419.

Topics: Hepatic Encephalopathy; Humans; Lactulose; Liver Cirrhosis; Ornithine; Treatment Outcome

In liver failure, inflammation synergistically exacerbates the deleterious cerebral effects of ammonia. The aims were to test whether treatment with the ammonia-lowering agent ornithine phenylacetate (OP) and/or anti-TNF-α (infliximab) prevent the deleterious brain consequences of lipopolysaccharide (LPS) in cirrhotic rats.. Rats 4 weeks following bile duct-ligation (BDL), sham-operation (sham) and/or 7 days hyperammonemic feed (HD), were randomized to receive LPS (1 mg/kg) or saline, and treatment with either 3 days intraperitoneal injections of OP (0.6 g/kg) and/or infliximab, 10 mg/kg. Animals were sacrificed at coma stages or at 3 h.. In sham rats, both HD and LPS increased brain water, with an increase in ammonia in the former and brain cytokines in the latter but with no effect on consciousness. BDL + HD rats caused significantly higher plasma ammonia, TNF-α and IL-6 levels compared to sham. LPS significantly worsened coma stage, increased brain water and plasma and brain TNF-α. OP significantly delayed LPS-induced progression to coma stages (P < 0.009), reduced arterial ammonia and brain water (P < 0.001 and P < 0.01 respectively), which was associated with a significant reduction in cytokines. Infliximab significantly reduced plasma and brain cytokines, but not brain water. OP + infliximab attenuated increase in brain water and delayed occurrence of coma, which was not different to OP alone. In BDL rats, OP reduced the expression of brain iNOS and NFκB.. Reduction in ammonia with OP in cirrhotic rats prevents LPS-induced brain edema and delays coma, suggesting that ammonia may prime the brain to the deleterious effect of LPS, possibly through effects on iNOS and NFκB related mechanisms.

Topics: Animals; Antibodies, Monoclonal; Bile Ducts; Blotting, Western; Body Water; Brain; Brain Edema; Cytokines; Hyperammonemia; Infliximab; Injections, Intraperitoneal; Interleukin-6; Ligation; Lipopolysaccharides; Liver Cirrhosis; Ornithine; Rats; Tumor Necrosis Factor-alpha