10 research outputs found
Safety, tolerability, and pharmacokinetics of l‐ornithine phenylacetate in patients with acute liver injury/failure and hyperammonemia
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142428/1/hep29621.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142428/2/hep29621-sup-0001-suppinfo1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142428/3/hep29621_am.pd
OCE-205 in rats and non-human primates: Pharmacokinetic and pharmacodynamic analysis
Treatment for complications associated with the hemodynamic consequences of decompensated cirrhosis remains suboptimal. Terlipressin, the latest pharmacological management of hepatorenal syndrome–acute kidney injury (HRS-AKI), targets the vasopressin system but has serious side effects. OCE-205 is a novel peptide designed to target the vasopressin receptor system as a mixed V1a agonist/antagonist, resulting in effective partial agonism without V2 agonism. We examined the in vivo pharmacokinetic/pharmacodynamic properties of OCE-205 in healthy rats and cynomolgus monkeys. OCE-205 was administered by IV or SC bolus injection; arginine vasopressin (AVP) or terlipressin were comparators. After IV OCE-205 administration in rats, mean plasma concentration decreased in a mostly linear manner to 2 mg/mL after 120 min, and for SC administration, slowly decreased to ∼50 ng/mL after 300 min. Compared with pre-test values, arterial blood pressure values significantly increased after all OCE-205 doses tested. For monkeys, the concentration after IV OCE-205 administration was mostly linear to 5 ng/mL after 180 min, and for SC administration, ∼3 ng/mL after 480 min. Subcutaneous OCE-205 administration increased mean arterial pressure (MAP) versus baseline, with ΔMAP in OCE-205–treated animals marked and long-lasting while terlipressin induced an increase from baseline in MAP, with negligible ΔMAP, on average, by 150 min after administration in all groups. AVP, but not OCE-205, significantly increased blood lactate concentrations. OCE-205 was well tolerated in adult male rats and cynomolgus monkeys following single-dose bolus administration. The preclinical results of OCE-205, with its demonstrated V1a selective partial agonist activity and potentially tolerable safety profile, suggest its potential utility for treatment of the cardiovascular complications of cirrhosis. Institutional protocol number: Procedures were approved by the Ferring Research Institute (FRI) Institutional Animal Care and Use Committee (IACUC) on November 27, 2006 under protocol FRI 06-011, and by the Sinclair Research Center IACUC under protocol S11177
A randomized, double-blind, placebo-controlled study assessing the safety and tolerability of regadenoson in subjects with asthma or chronic obstructive pulmonary disease
BACKGROUND: Adenosine receptor stress agents for myocardial perfusion imaging (MPI) may cause A(2B) and/or A(3) receptor-mediated bronchoconstriction, of particular concern to physicians testing patients with asthma or chronic obstructive pulmonary disease (COPD). METHODS: A Phase 4, randomized, double-blind study (NCT00862641) assessed the safety of the selective A(2A) receptor agonist, regadenoson, compared with placebo in subjects with asthma or COPD who represented likely candidates for MPI. RESULTS: Overall, 356 and 176 subjects with asthma and 316 and 151 subjects with COPD received regadenoson and placebo, respectively. The percentage of subjects experiencing a >15% decrease in FEV(1) from baseline to any assessment up to 24 hours post-baseline was not statistically significantly different between the regadenoson and the placebo groups in the asthma or COPD stratum. Dyspnea, the most frequent respiratory adverse event, occurred with higher incidence (P < .0001) in the regadenoson group than the placebo group in the asthma (10.7% vs 1.1%) and COPD (18.0% vs 2.6%) strata. No subjects experienced severe bronchoconstriction, although the occurrence of such reactions with adenosine receptor agonists cannot be ruled out, such that caution is advised. CONCLUSIONS: This information may be helpful to physicians selecting a pharmacologic stress agent for MPI in patients with asthma or COPD
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Efficacy and Safety of Ornithine Phenylacetate for Treating Overt Hepatic Encephalopathy in a Randomized Trial
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.
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Pharmacokinetics/pharmacodynamics of L-ornithine phenylacetate in overt hepatic encephalopathy and the effect of plasma ammonia concentration reduction on clinical outcomes
Hepatic encephalopathy (HE) is a serious neurocognitive complication of liver dysfunction, often associated with elevated plasma ammonia. Ornithine phenylacetate (OP), a potent ammonia scavenger, is being evaluated for the treatment of acute/overt HE. The pharmacokinetics and pharmacodynamics of OP in patients with HE were characterized in this phase IIb study (NCT01966419). Adult patients hospitalized with an overt HE episode, cirrhosis, and plasma ammonia above the upper limit of normal (ULN) who failed to improve after 48 hours' standard care were randomly assigned to continuous intravenous OP (10, 15, or 20 g/day, based on Child-Turcotte-Pugh score) or matching placebo for 5 days. Plasma levels of ornithine and phenylacetic acid (PAA) and plasma/urinary levels of phenylacetylglutamine (PAGN) (primary metabolite of PAA) were regularly assessed; plasma ammonia level was the primary pharmacodynamic variable. PAA demonstrated dose-dependent pharmacokinetics; ornithine and PAGN levels increased with dose. PAGN urinary excretion represented similar to 50%-60% of administered PAA across all doses. Mean reduction in plasma ammonia with OP at 3 hours postinfusion was significantly greater versus placebo (p = 0.014); and time to achieve plasma ammonia less than or equal to the ULN was significantly reduced (p = 0.028). Achievement of clinical response based on HE stage was associated with a greater reduction in mean plasma ammonia level (p = 0.009). OP effects on plasma ammonia were consistent with its proposed mechanism of action as a primary ammonia scavenger, with a significant association between reduced plasma ammonia and improvement in HE stage. OP should be further evaluated as a promising treatment for hyperammonemia in patients with overt HE.
Study Highlights
WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC?
Overt hepatic encephalopathy (OHE) is characterized by severe liver impairment and signs of neurocognitive dysfunction commonly associated with hyperammonemia. Ornithine phenylacetate (OP), a potent ammonia scavenger, has an acceptable safety profile in patients with decompensated cirrhosis and gastrointestinal bleeding, and lowers plasma ammonia levels.
WHAT QUESTION DID THIS STUDY ADDRESS?
What are the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of OP and its metabolites in patients hospitalized due to OHE with cirrhosis and hyperammonemia?
WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE?
PK/PD analysis results are consistent with the putative mechanism of action of OP. Mean plasma levels of OP analytes reach steady state in approximately 48-72 hours, regardless of dose, and appear to increase as liver function declines. OP treatment significantly reduces plasma ammonia and improves clinical OHE stage, supporting the proposed central role of ammonia in HE.
HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE?
OP treatment may be beneficial as a first-line treatment for patients with OHE; however, additional studies are warranted