Allopregnanolone and its antagonist modulate neuroinflammation and neurological impairment.

Neuroinflammation accompanies several brain disorders, either as a secondary consequence or as a primary cause and may contribute importantly to disease pathogenesis. Neurosteroids which act as Positive Steroid Allosteric GABA-A receptor Modulators (Steroid-PAM) appear to modulate neuroinflammation and their levels in the brain may vary because of increased or decreased local production or import from the systemic circulation. The increased synthesis of steroid-PAMs is possibly due to increased expression of the mitochondrial cholesterol transporting protein (TSPO) in neuroinflammatory tissue, and reduced production may be due to changes in the enzymatic activity. Microglia and astrocytes play an important role in neuroinflammation, and their production of inflammatory mediators can be both activated and inhibited by steroid-PAMs and GABA. What is surprising is the finding that both allopregnanolone, a steroid-PAM, and golexanolone, a novel GABA-A receptor modulating steroid antagonist (GAMSA), can inhibit microglia and astrocyte activation and normalize their function. This review focuses on the role of steroid-PAMs in neuroinflammation and their importance in new therapeutic approaches to CNS and liver disease.

A pilot study of golexanolone, a new GABA-A receptor-modulating steroid antagonist, in patients with covert hepatic encephalopathy.

BACKGROUND & AIMS: Golexanolone is a novel small molecule GABA-A receptor-modulating steroid antagonist under development for the treatment of cognitive and vigilance disorders caused by allosteric over-activation of GABA-A receptors by neurosteroids. It restored spatial learning and motor coordination in animal models of hepatic encephalopathy (HE) and mitigated the effects of intravenous allopregnanolone in healthy adults in a dose-dependent fashion. Herein, we report data on the safety, pharmacokinetics (PK) and efficacy of golexanolone in adult patients with cirrhosis. METHODS: Following single/multiple ascending dose studies, adults with Child-Pugh A/B cirrhosis and abnormal continuous reaction time (CRT) on screening were randomized to 3 weeks' dosing with golexanolone (10, 40 or 80 mg BID) or placebo. CRT, psychometric hepatic encephalopathy score (PHES), animal naming test (ANT), Epworth sleepiness scale (ESS) and electroencephalogram (mean dominant frequency [MDF]; delta+theta/alpha+beta ratio [DT/AB]) were obtained at baseline, 10, and 21 days. RESULTS: Golexanolone exhibited satisfactory safety and PK. Baseline characteristics were similar between the 12 and 33 patients randomized to placebo or golexanolone, respectively. By prespecified analyses, golexanolone was associated with directionally favourable changes vs. placebo in ESS (p = 0.047), MDF (p = 0.142) and DT/AB (p = 0.021). All patients also showed directionally favourable changes in CRT, PHES and ANT, but with no statistical difference between golexanolone and placebo. Post hoc analyses taking into account the variability and improvement in CRT, PHES and ANT observed between screening and baseline suggested an efficacy signal by cognitive measures as well. CONCLUSION: Golexanolone was well tolerated and associated with improvement in cognitive performance. These results implicate GABA-A receptor-modulating neurosteroids in the pathogenesis of HE and support the therapeutic potential of golexanolone. LAY SUMMARY: Many patients with cirrhosis experience subtle but disabling cognitive problems, including sleepiness and poor attention span, that impair their ability to be gainfully employed or carry out activities of daily living. This pilot study tested the hypothesis that these problems with cognition, for which there is no approved treatment, might be improved by an experimental drug, golexanolone, designed to normalize the function of receptors which inhibit brain function. The results of this study suggest that golexanolone is well tolerated and may improve cognition, as reflected by measures of sleepiness, attention span and brain wave activity, paving the way for future larger studies of this promising experimental drug. CLINICAL TRIAL REGISTRATION NUMBER: EudraCT 2016-003651-30.

Validation of PAS Kinase, a Regulator of Hepatic Fatty Acid and Triglyceride Synthesis, as a Therapeutic Target for Nonalcoholic Steatohepatitis.

Hyperactivation of sterol regulatory element binding protein 1c (SREBP-1c), which transcriptionally induces expression of enzymes responsible for de novo lipogenesis and triglyceride (TG) formation, is implicated in nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH) pathogenesis. Posttranslational SREBP-1c maturation and activation is stimulated by the protein per-arnt-sim kinase (PASK). PASK-knockout mice are phenotypically normal on a conventional diet but exhibit decreased hypertriglyceridemia, insulin resistance, and hepatic steatosis on a high-fat diet. We investigated the effects of pharmacologic PASK inhibition using BioE-1115, a selective and potent oral PASK inhibitor, in Zucker fatty (fa)/fa) rats, a genetic model of obesity, dyslipidemia, and insulin resistance, and in a dietary murine model of NAFLD/NASH. Female Zucker (fa/fa) rats and lean littermate (fa/+) controls received BioE-1115 (3-100 mg/kg/day) and/or omega-3 fatty acids, and blood glucose, hemoglobin A1c, glucose tolerance, insulin, and serum TG were measured. C57BL/6J mice fed a high-fat/high-fructose diet (HF-HFrD) were treated with BioE-1115 (100 mg/kg/day) or vehicle. Body weight and fasting glucose were measured regularly; serum TG, body and organ weights, and liver TG and histology were assessed at sacrifice. Messenger RNA (mRNA) abundance of SREBP-1c target genes was measured in both models. In Zucker rats, BioE-1115 treatment produced significant dose-dependent reductions in blood glucose, insulin, and TG (all greater than omega-3 fatty acids) and dose dependently restored insulin sensitivity assessed by glucose tolerance testing. In HF-HFrD mice, BioE-1115 reduced body weight, liver weight, fasting blood glucose, serum TGs, hepatic TG, hepatic fibrosis, hepatocyte vacuolization, and bile duct hyperplasia. BioE-1115 reduced SREBP-1c target mRNA transcripts in both models. Conclusion: PASK inhibition mitigates many adverse metabolic consequences associated with an HF-HFrD and reduces hepatic fat content and fibrosis. This suggests that inhibition of PASK is an attractive therapeutic strategy for NAFLD/NASH treatment.

Barriers to drug adherence in the treatment of urea cycle disorders: Assessment of patient, caregiver and provider perspectives.

UNLABELLED: Patients and families living with metabolic disorders face challenging dietary and drug treatment regimens. On the hypothesis that poor palatability, volume and frequency of drug/formula administration contribute to treatment non-adherence and hyperammonemic episodes, a survey was conducted of patient, caregiver (CG) and physician perspectives on treatments used in urea cycle disorders (UCD). METHODS: A paper and online survey assessed experience with UCD medications, medical foods and dietary supplements. RESULTS: 25 physicians, 52 adult patients and 114 CG responded. In 2009, the most common UCD-specific intervention reported by patients included sodium phenylbutyrate (60%), followed by l-citrulline (46%), amino acid medical foods (15%), l-arginine preparations (18%), and sodium benzoate (8%). Only 36% of patients reported experiencing no hyperammonemic episodes in the last 2 years. The most commonly reported cause of hyperammonemic episodes was infection or other acute illnesses, followed by dietary indiscretion, side effects of medications, and drug non-adherence. Most patients, caregivers and physicians (> 75%) ranked nitrogen-scavenging medications, l-citrulline, l-arginine, and medical foods as "effective" or "very effective." Non-adherence was common (e.g. 18% of patients admitted to missing sodium phenylbutyrate "at least once a week" and "at least one a day"). Barriers to adherence included taste of medications, frequency of drug administration, number of pills, difficulty swallowing pills, side effects, forgetting to take medications, and high cost. Strategies to mitigate the gastrointestinal side effects of medications included the use of gastric tubes and acid reflux medications. Physicians indicated that 25% and 33% of pediatric and adult patients, respectively, were given less than the recommended dose of sodium phenylbutyrate due to concerns of tolerance, administration, and cost. CONCLUSIONS: Despite positive views of their effectiveness, respondents found medications, medical foods and dietary supplements difficult to take and viewed adherence as inadequate, thus contributing to hyperammonemic episodes.

Protein and calorie intakes in adult and pediatric subjects with urea cycle disorders participating in clinical trials of glycerol phenylbutyrate.

BACKGROUND: Little prospectively collected data are available comparing the dietary intake of urea cycle disorder (UCD) patients to UCD treatment guidelines or to healthy individuals. OBJECTIVE: To examine the protein and calorie intakes of UCD subjects who participated in clinical trials of glycerol phenylbutyrate (GPB) and compare these data to published UCD dietary guidelines and nutritional surveys. DESIGN: Dietary data were recorded for 45 adult and 49 pediatric UCD subjects in metabolic control during participation in clinical trials of GPB. Protein and calorie intakes were compared to UCD treatment guidelines, average nutrient intakes of a healthy US population based on the National Health and Nutrition Examination Survey (NHANES) and Recommended Daily Allowances (RDA). RESULTS: In adults, mean protein intake was higher than UCD recommendations but lower than RDA and NHANES values, while calorie intake was lower than UCD recommendations, RDA and NHANES. In pediatric subjects, prescribed protein intake was higher than UCD guidelines, similar to RDA, and lower than NHANES data for all age groups, while calorie intake was at the lower end of the recommended UCD range and close to RDA and NHANES data. In pediatric subjects height, weight, and body mass index (BMI) Z-scores were within normal range (- 2 to 2). CONCLUSIONS: Pediatric patients treated with phenylbutyrate derivatives exhibited normal height and weight. Protein and calorie intakes in adult and pediatric UCD subjects differed from UCD dietary guidelines, suggesting that these guidelines may need to be reconsidered.

Fasting Blood Ammonia Predicts Risk and Frequency of Hepatic Encephalopathy Episodes in Patients With Cirrhosis.

BACKGROUND & AIMS: There is controversy over the use of measuring blood levels of ammonia (NH3) in the management of patients with overt hepatic encephalopathy (HE). METHODS: We performed a retrospective analysis of data from a randomized, double-blind study of 178 patients with cirrhosis given glycerol phenylbutyrate (an NH3-lowering agent) or placebo for 16 weeks. Blood samples were collected at baseline and on study days 7 and 14 and NH3 levels were measured. The probabilities of having an HE episode, based on ammonia values, were modeled using binary logistic regression. A Cox proportional model was used to determine the risk of HE episodes in patients with baseline fasting NH3 levels ≤1.5-fold the upper limit of normal (ULN) versus patients with fasting NH3 levels >1.5-fold the ULN. RESULTS: The risk and frequency of HE episodes and HE-related hospitalizations correlated with baseline (mean, 51 ± 6 µmol/L; ULN, 35 µmol/L) and on-study fasting levels of NH3, and increased sharply at levels >1.5-fold the ULN. Regardless of baseline level, NH3 exposure and the relative risk of HE episodes were decreased by glycerol phenylbutyrate. CONCLUSIONS: In analysis of data from a phase 2 study of the effects of glycerol phenylbutyrate in patients with cirrhosis, we found that fasting levels of NH3 in blood can identify patients at risk for HE-related morbidity. Patients with HE might benefit from NH3-lowering therapy. ClinicalTrials.gov no: NCT 00999167.

Self-reported treatment-associated symptoms among patients with urea cycle disorders participating in glycerol phenylbutyrate clinical trials.

BACKGROUND: Health care outcomes have been increasingly assessed through health-related quality of life (HRQoL) measures. While the introduction of nitrogen-scavenging medications has improved survival in patients with urea cycle disorders (UCDs), they are often associated with side effects that may affect patient compliance and outcomes. METHODS: Symptoms commonly associated with nitrogen-scavenging medications were evaluated in 100 adult and pediatric participants using a non-validated UCD-specific questionnaire. Patients or their caregivers responded to a pre-defined list of symptoms known to be associated with the use of these medications. Responses were collected at baseline (while patients were receiving sodium phenylbutyrate [NaPBA]) and during treatment with glycerol phenylbutyrate (GPB). RESULTS: After 3 months of GPB dosing, there were significant reductions in the proportion of patients with treatment-associated symptoms (69% vs. 46%; p<0.0001), the number of symptoms per patient (2.5 vs. 1.1; p<0.0001), and frequency of the more commonly reported individual symptoms such as body odor, abdominal pain, nausea, burning sensation in mouth, vomiting, and heartburn (p<0.05). The reduction in symptoms was observed in both pediatric and adult patients. The presence or absence of symptoms or change in severity did not correlate with plasma ammonia levels or NaPBA dose. CONCLUSIONS: The reduction in symptoms following 3 months of open-label GPB dosing was similar in pediatric and adult patients and may be related to chemical structure and intrinsic characteristics of the product rather than its effect on ammonia control.

Blood ammonia and glutamine as predictors of hyperammonemic crises in patients with urea cycle disorder.

PURPOSE: The aim of this study was to examine predictors of ammonia exposure and hyperammonemic crises in patients with urea cycle disorders. METHODS: The relationships between fasting ammonia, daily ammonia exposure, and hyperammonemic crises were analyzed in >100 patients with urea cycle disorders. RESULTS: Fasting ammonia correlated strongly with daily ammonia exposure (r = 0.764; P < 0.001). For patients with fasting ammonia concentrations <0.5 upper limit of normal (ULN), 0.5 to <1.0 ULN, and ≥1.0 ULN, the probability of a normal average daily ammonia value was 87, 60, and 39%, respectively, and 10.3, 14.1, and 37.0% of these patients, respectively, experienced ≥1 hyperammonemic crisis over 12 months. Time to first hyperammonemic crisis was shorter (P = 0.008) and relative risk (4.5×; P = 0.011) and rate (~5×, P = 0.006) of hyperammonemic crises were higher in patients with fasting ammonia ≥1.0 ULN vs. <0.5ULN; relative risk was even greater (20×; P = 0.009) in patients ≥6 years old. A 10- or 25-µmol/l increase in ammonia exposure increased the relative risk of a hyperammonemic crisis by 50 and >200% (P < 0.0001), respectively. The relationship between ammonia and hyperammonemic crisis risk seemed to be independent of treatment, age, urea cycle disorder subtype, dietary protein intake, or blood urea nitrogen. Fasting glutamine correlated weakly with daily ammonia exposure assessed as 24-hour area under the curve and was not a significant predictor of hyperammonemic crisis. CONCLUSION: Fasting ammonia correlates strongly and positively with daily ammonia exposure and with the risk and rate of hyperammonemic crises, suggesting that patients with urea cycle disorder may benefit from tight ammonia control.

Glycerol phenylbutyrate treatment in children with urea cycle disorders: pooled analysis of short and long-term ammonia control and outcomes.

OBJECTIVE: To evaluate glycerol phenylbutyrate (GPB) in the treatment of pediatric patients with urea cycle disorders (UCDs). STUDY DESIGN: UCD patients (n=26) ages 2months through 17years were treated with GPB and sodium phenylbutyrate (NaPBA) in two short-term, open-label crossover studies, which compared 24-hour ammonia exposure (AUC0-24) and glutamine levels during equivalent steady-state dosing of GPB and sodium phenylbutyrate (NaPBA). These 26 patients plus an additional 23 patients also received GPB in one of three 12-month, open label extension studies, which assessed long-term ammonia control, hyperammonemic (HA) crises, amino acid levels, and patient growth. RESULTS: Mean ammonia exposure on GPB was non-inferior to NaPBA in each of the individual crossover studies. In the pooled analyses, it was significantly lower on GPB vs. NaPBA (mean [SD] AUC0-24: 627 [302] vs. 872 [516] µmol/L; p=0.008) with significantly fewer abnormal values (15% on GPB vs. 35% on NaPBA; p=0.02). Mean ammonia levels remained within the normal range during 12months of GPB dosing and, when compared with the 12months preceding enrollment, a smaller percentage of patients (24.5% vs. 42.9%) experienced fewer (17 vs. 38) HA crises. Glutamine levels tended to be lower with GPB than with NaPBA during short-term dosing (mean [SD]: 660.8 [164.4] vs. 710.0 [158.7] µmol/L; p=0.114) and mean glutamine and branched chain amino acid levels, as well as other essential amino acids, remained within the normal range during 12months of GPB dosing. Mean height and weight Z-scores were within normal range at baseline and did not change significantly during 12months of GPB treatment. CONCLUSIONS: Dosing with GPB was associated with 24-hour ammonia exposure that was non-inferior to that during dosing with NaPBA in individual studies and significantly lower in the pooled analysis. Long-term GPB dosing was associated with normal levels of glutamine and essential amino acids, including branched chain amino acids, age-appropriate growth and fewer HA crises as compared with the 12month period preceding enrollment.

Randomized, double-blind, controlled study of glycerol phenylbutyrate in hepatic encephalopathy.

UNLABELLED: Glycerol phenylbutyrate (GPB) lowers ammonia by providing an alternate pathway to urea for waste nitrogen excretion in the form of phenylacetyl glutamine, which is excreted in urine. This randomized, double-blind, placebo-controlled phase II trial enrolled 178 patients with cirrhosis, including 59 already taking rifaximin, who had experienced two or more hepatic encephalopathy (HE) events in the previous 6 months. The primary endpoint was the proportion of patients with HE events. Other endpoints included the time to first event, total number of events, HE hospitalizations, symptomatic days, and safety. GPB, at 6 mL orally twice-daily, significantly reduced the proportion of patients who experienced an HE event (21% versus 36%; P=0.02), time to first event (hazard ratio [HR]=0.56; P<0.05), as well as total events (35 versus 57; P=0.04), and was associated with fewer HE hospitalizations (13 versus 25; P=0.06). Among patients not on rifaximin at enrollment, GPB reduced the proportion of patients with an HE event (10% versus 32%; P<0.01), time to first event (HR=0.29; P<0.01), and total events (7 versus 31; P<0.01). Plasma ammonia was significantly lower in patients on GPB and correlated with HE events when measured either at baseline or during the study. A similar proportion of patients in the GPB (79%) and placebo groups (76%) experienced adverse events. CONCLUSION: GPB reduced HE events as well as ammonia in patients with cirrhosis and HE and its safety profile was similar to placebo. The findings implicate ammonia in the pathogenesis of HE and suggest that GPB has therapeutic potential in this population. (Clinicaltrials.gov, NCT00999167).

Ammonia control in children ages 2 months through 5 years with urea cycle disorders: comparison of sodium phenylbutyrate and glycerol phenylbutyrate.

OBJECTIVES: To examine ammonia levels, pharmacokinetics, and safety of glycerol phenylbutyrate (GPB; also referred to as HPN-100) and sodium phenylbutyrate (NaPBA) in young children with urea cycle disorders (UCDs). STUDY DESIGN: This open label switch-over study enrolled patients ages 29 days to under 6 years taking NaPBA. Patients underwent 24-hour blood and urine sampling on NaPBA and again on a phenylbutyric acid-equimolar dose of GPB and completed questionnaires regarding signs and symptoms associated with NaPBA and/or their UCD. RESULTS: Fifteen patients (8 argininosuccinate lyase deficiency, 3 argininosuccinic acid synthetase deficiency, 3 ornithine transcarbamylase deficiency, 1 arginase deficiency) ages 2 months through 5 years enrolled in and completed the study. Daily ammonia exposure (24-hour area under the curve) was lower on GPB and met predefined noninferiority criteria (ratio of means 0.79; 95% CI 0.593-1.055; P=.03 Wilcoxon; 0.07 t test). Six patients experienced mild adverse events on GPB; there were no serious adverse events or significant laboratory changes. Liver tests and argininosuccinic acid levels among patients with argininosuccinate lyase deficiency were unchanged or improved on GPB. Eleven of 15 patients reported 35 symptoms on day 1; 23 of these 35 symptoms improved or resolved on GPB. Mean systemic exposure to phenylbutyric acid, phenylacetic acid, and phenylacetylglutamine (PAGN) were similar and phenylacetic acid exposure tended to be higher in the youngest children on both drugs. Urinary PAGN concentration was greater on morning voids and varied less over 24 hours on GPB versus NaPBA. CONCLUSIONS: GPB results in more evenly distributed urinary output of PAGN over 24 hours were associated with fewer symptoms and offers ammonia control comparable with that observed with NaPBA in young children with UCDs.

Ammonia control and neurocognitive outcome among urea cycle disorder patients treated with glycerol phenylbutyrate.

UNLABELLED: Glycerol phenylbutyrate is under development for treatment of urea cycle disorders (UCDs), rare inherited metabolic disorders manifested by hyperammonemia and neurological impairment. We report the results of a pivotal Phase 3, randomized, double-blind, crossover trial comparing ammonia control, assessed as 24-hour area under the curve (NH3 -AUC0-24hr ), and pharmacokinetics during treatment with glycerol phenylbutyrate versus sodium phenylbutyrate (NaPBA) in adult UCD patients and the combined results of four studies involving short- and long-term glycerol phenylbutyrate treatment of UCD patients ages 6 and above. Glycerol phenylbutyrate was noninferior to NaPBA with respect to ammonia control in the pivotal study, with mean (standard deviation, SD) NH3 -AUC0-24hr of 866 (661) versus 977 (865) µmol·h/L for glycerol phenylbutyrate and NaPBA, respectively. Among 65 adult and pediatric patients completing three similarly designed short-term comparisons of glycerol phenylbutyrate versus NaPBA, NH3 -AUC0-24hr was directionally lower on glycerol phenylbutyrate in each study, similar among all subgroups, and significantly lower (P < 0.05) in the pooled analysis, as was plasma glutamine. The 24-hour ammonia profiles were consistent with the slow-release behavior of glycerol phenylbutyrate and better overnight ammonia control. During 12 months of open-label glycerol phenylbutyrate treatment, average ammonia was normal in adult and pediatric patients and executive function among pediatric patients, including behavioral regulation, goal setting, planning, and self-monitoring, was significantly improved. CONCLUSION: Glycerol phenylbutyrate exhibits favorable pharmacokinetics and ammonia control relative to NaPBA in UCD patients, and long-term glycerol phenylbutyrate treatment in pediatric UCD patients was associated with improved executive function (ClinicalTrials.gov NCT00551200, NCT00947544, NCT00992459, NCT00947297). (HEPATOLOGY 2012).

Glycerol Phenylbutyrate in Patients With Cirrhosis and Episodic Hepatic Encephalopathy: A Pilot Study of Safety and Effect on Venous Ammonia Concentration.

Glycerol tri-(4-phenylbutyrate) (glycerol phenylbutyrate, GPB, HPN-100) mediates waste nitrogen excretion through conjugation with glutamine to form phenylacetylglutamine which is excreted in urine. This pilot study was performed to assess tolerability and effect on venous ammonia concentration in patients with cirrhosis and hepatic encephalopathy (HE). Patients underwent one week of 6 mL (6.6 g) twice daily (BID). GPB dosing followed by 3 weeks of 9 mL (9.9 g) BID dosing and underwent repeated blood sampling for ammonia concentration and pharmacokinetics. Fifteen patients were enrolled. Ammonia concentrations were lowest after overnight fast and increased post-prandially. Fasting ammonia concentrations were lower on GPB compared to baseline, with a decrease on the eighth day of 6 mL BID dosing to 45.4 (27.9) µmol/L (ULN ∼48 µmol/L) (P < .05). Nine milliliters BID yielded similar lowering but was associated with more adverse events and higher phenylacetate (PAA) plasma concentrations (PAA Cmax of 144 [125] vs. 292 [224] µg/mL on 6 and 9 mL, respectively). GPB dosed at 6 mL BID lowered fasting ammonia levels in cirrhotic patients with HE as compared with baseline, was better tolerated than 9 mL BID, and is appropriate for further evaluation in patients with cirrhosis and episodic HE.

Pharmacology and safety of glycerol phenylbutyrate in healthy adults and adults with cirrhosis.

UNLABELLED: Phenylbutyric acid (PBA), which is approved for treatment of urea cycle disorders (UCDs) as sodium phenylbutyrate (NaPBA), mediates waste nitrogen excretion via combination of PBA-derived phenylacetic acid with glutamine to form phenylactylglutamine (PAGN) that is excreted in urine. Glycerol phenylbutyrate (GPB), a liquid triglyceride pro-drug of PBA, containing no sodium and having favorable palatability, is being studied for treatment of hepatic encephalopathy (HE). In vitro and clinical studies have been performed to assess GPB digestion, safety, and pharmacology in healthy adults and individuals with cirrhosis. GPB hydrolysis was measured in vitro by way of pH titration. Twenty-four healthy adults underwent single-dose administration of GPB and NaPBA and eight healthy adults and 24 cirrhotic subjects underwent single-day and multiple-day dosing of GPB, with metabolites measured in blood and urine. Simulations were performed to assess GPB dosing at higher levels. GPB was hydrolyzed by human pancreatic triglyceride lipase, pancreatic lipase-related protein 2, and carboxyl-ester lipase. Clinical safety was satisfactory. Compared with NaPBA, peak metabolite blood levels with GPB occurred later and were lower; urinary PAGN excretion was similar but took longer. Steady state was achieved within 4 days for both NaPBA and GPB; intact GPB was not detected in blood or urine. Cirrhotic subjects converted GPB to PAGN similarly to healthy adults. Simulations suggest that GPB can be administered safely to cirrhotic subjects at levels equivalent to the highest approved NaPBA dose for UCDs. CONCLUSION: GPB exhibits delayed release characteristics, presumably reflecting gradual PBA release by pancreatic lipases, and is well tolerated in adults with cirrhosis, suggesting that further clinical testing for HE is warranted.

Phase 2 comparison of a novel ammonia scavenging agent with sodium phenylbutyrate in patients with urea cycle disorders: safety, pharmacokinetics and ammonia control.

UNLABELLED: Glycerol phenylbutyrate (glyceryl tri (4-phenylbutyrate)) (GPB) is being studied as an alternative to sodium phenylbutyrate (NaPBA) for the treatment of urea cycle disorders (UCDs). This phase 2 study explored the hypothesis that GPB offers similar safety and ammonia control as NaPBA, which is currently approved as adjunctive therapy in the chronic management of UCDs, and examined correlates of 24-h blood ammonia. METHODS: An open-label, fixed sequence switch-over study was conducted in adult UCD patients taking maintenance NaPBA. Blood ammonia and blood and urine metabolites were compared after 7 days (steady state) of TID dosing on either drug, both dosed to deliver the same amount of phenylbutyric acid (PBA). RESULTS: Ten subjects completed the study. Adverse events were comparable for the two drugs; 2 subjects experienced hyperammonemic events on NaPBA while none occurred on GPB. Ammonia values on GPB were approximately 30% lower than on NaPBA (time-normalized AUC=26.2 vs. 38.4 micromol/L; Cmax=56.3 vs. 79.1 micromol/L; not statistically significant), and GPB achieved non-inferiority to NaPBA with respect to ammonia (time-normalized AUC) by post hoc analysis. Systemic exposure (AUC(0-24)) to PBA on GPB was 27% lower than on NaPBA (540 vs. 739 microgh/mL), whereas exposure to phenylacetic acid (PAA) (575 vs. 596 microg h/mL) and phenylacetylglutamine (PAGN) (1098 vs. 1133 microg h/mL) were similar. Urinary PAGN excretion accounted for approximately 54% of PBA administered for both NaPBA and GPB; other metabolites accounted for <1%. Intact GPB was generally undetectable in blood and urine. Blood ammonia correlated strongly and inversely with urinary PAGN (r=-0.82; p<0.0001) but weakly or not at all with blood metabolite levels. CONCLUSIONS: Safety and ammonia control with GPB appear at least equal to NaPBA. Urinary PAGN, which is stoichiometrically related to nitrogen scavenging, may be a useful biomarker for both dose selection and adjustment for optimal control of venous ammonia.

Safety and immunogenicity of an intramuscular Helicobacter pylori vaccine in noninfected volunteers: a phase I study.

INTRODUCTION: Helicobacter pylori infection is among the most common human infections and the major risk factor for peptic disease and gastric cancer. Immunization with vaccines containing the H pylori vacuolating cytotoxin A (VacA), cytotoxin-associated antigen (CagA), and neutrophil-activating protein (NAP), alone or in combination, have been shown to prevent experimental infection in animals. AIM: We sought to study the safety and immunogenicity of a vaccine consisting of recombinant VacA, CagA, and NAP given intramuscularly with aluminium hydroxide as an adjuvant to noninfected healthy subjects. METHODS: This controlled, single-blind Phase I study randomized 57 H pylori-negative volunteers into 7 study arms exploring 2 dosages (10 and 25 microg) of each antigen and 3 schedules (0, 1, 2 weeks; 0, 1, 2 months; and 0, 1, 4 months) versus alum controls. All participants were followed for 5 months. Thirty-six subjects received a booster vaccination 18-24 months after the completion of the primary vaccination. RESULTS: Local and systemic adverse reactions were mild and similar in placebo and vaccine recipients on the monthly schedules. All subjects responded to 1 or 2 of the antigens and 86% of all vaccines mounted immunoglobulin G antibody responses to all 3 antigens. Vaccinees exhibited an antigen-specific cellular response. Vaccination 18-24 months later elicited anamnestic antibody and cellular responses. CONCLUSIONS: This intramuscular H pylori vaccine demonstrated satisfactory safety and immunogenicity, produced antigen-specific T-cell memory, and, therefore, warrants further clinical study.

Blasts from the past.

With this issue of the JCI, we celebrate the 80th anniversary of the Journal. While 80 years is not a century, we still feel it is important to honor what the JCI has meant to the biomedical research community for 8 decades. To illustrate why the JCI is the leading general-interest translational research journal edited by and for biomedical researchers, we have asked former JCI editors-in-chief to reflect on some of the major scientific advances reported in the pages of the Journal during their tenures.

Thyroid hormone export varies among primary cells and appears to differ from hormone uptake.

We characterized T3 efflux in primary cultures of cells derived from human placenta, neonatal rat cardiac myocytes, and rat inner medullary collecting ducts (IMCD). The T3 efflux rate was highest in placenta cells, followed by ventriculocytes, atriocytes, and IMCD cells. Verapamil reversibly blocked [125I]T3 efflux in these cells in a manner that correlated with their T3 efflux rate. Thus, verapamil inhibition of [125I]T3 efflux in placenta cells led to a 432% increase in the [125I]T3 content compared with 33% increase in IMCD cells. Several unlabeled iodothyronines, but not TRIAC, differentially blocked [125I]T3 efflux such as (T4 > T3 > rT3 = D-T3 > D-T4) in placenta cells and (T4 > rT3 = D-T4 = T3 > D-T3) in ventriculocytes, suggesting tissue-specific differences in the carriers/transporters responsible for T3 efflux. This hypothesis draws further support from the fact that D-T3 inhibited [125I]T3 efflux in placenta cells, but not in ventriculocytes. TRIAC did not affect T3 efflux in ventriculocytes or placenta cells, but it greatly inhibited [125I]T3 uptake in these cells, suggesting that [125I]T3 uptake and efflux mechanisms are distinct and appear to be mediated by distinct carrier/transporter proteins. Collectively, these data suggest that differences in thyroid hormone transport in target cells may provide an important mechanism for regulating hormone action in a tissue-specific fashion.