A multiomics approach reveals evidence for phenylbutyrate as a potential treatment for combined D,L-2- hydroxyglutaric aciduria.

PURPOSE: To identify therapies for combined D, L-2-hydroxyglutaric aciduria (C-2HGA), a rare genetic disorder caused by recessive variants in the SLC25A1 gene. METHODS: Patients C-2HGA were identified and diagnosed by whole exome sequencing and biochemical genetic testing. Patient derived fibroblasts were then treated with phenylbutyrate and the functional effects assessed by metabolomics and RNA-sequencing. RESULTS: In this study, we demonstrated that C-2HGA patient derived fibroblasts exhibited impaired cellular bioenergetics. Moreover, Fibroblasts form one patient exhibited worsened cellular bioenergetics when supplemented with citrate. We hypothesized that treating patient cells with phenylbutyrate (PB), an FDA approved pharmaceutical drug that conjugates glutamine for renal excretion, would reduce mitochondrial 2-ketoglutarate, thereby leading to improved cellular bioenergetics. Metabolomic and RNA-seq analyses of PB-treated fibroblasts demonstrated a significant decrease in intracellular 2-ketoglutarate, 2-hydroxyglutarate, and in levels of mRNA coding for citrate synthase and isocitrate dehydrogenase. Consistent with the known action of PB, an increased level of phenylacetylglutamine in patient cells was consistent with the drug acting as 2-ketoglutarate sink. CONCLUSION: Our pre-clinical studies suggest that citrate supplementation has the possibility exacerbating energy metabolism in this condition. However, improvement in cellular bioenergetics suggests phenylbutyrate might have interventional utility for this rare disease.

New insights into sodium phenylbutyrate as a pharmacotherapeutic option for neurological disorders.

Neurological disorders (NDs) are diseases of the central and peripheral nervous systems that affect more than one billion people worldwide. The risk of developing an ND increases with age due to the vulnerability of the different organs and systems to genetic, environmental, and social changes that consequently cause motor and cognitive deficits that disable the person from their daily activities and individual and social productivity. Intrinsic factors (genetic factors, age, gender) and extrinsic factors (addictions, infections, or lifestyle) favor the persistence of systemic inflammatory processes that contribute to the evolution of NDs. Neuroinflammation is recognized as a common etiopathogenic factor of ND. The study of new pharmacological options for the treatment of ND should focus on improving the characteristic symptoms and attacking specific molecular targets that allow the delay of damage processes such as neuroinflammation, oxidative stress, cellular metabolic dysfunction, and deregulation of transcriptional processes. In this review, we describe the possible role of sodium phenylbutyrate (NaPB) in the pathogenesis of Alzheimer's disease, hepatic encephalopathy, aging, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis; in addition, we describe the mechanism of action of NaPB and its beneficial effects that have been shown in various in vivo and in vitro studies to delay the evolution of any ND.

4-Phenylbutyrate promoted wild-type γ-aminobutyric acid type A receptor trafficking, reduced endoplasmic reticulum stress, and mitigated seizures in Gabrg2+/Q390X mice associated with Dravet syndrome.

OBJECTIVE: γ-Aminobutyric acid type A (GABAA ) receptor subunit gene mutations are major causes of various epilepsy syndromes, including severe kinds such as Dravet syndrome. Although the GABAA receptor is a major target for antiseizure medications, treating GABAA receptor mutations with receptor channel modulators is ineffective. Here, we determined the effect of a novel treatment with 4-phenylbutyrate (PBA) in Gabrg2+/Q390X knockin mice associated with Dravet syndrome. METHODS: We used biochemistry in conjunction with differential tagging of the wild-type and the mutant alleles, live brain slice surface biotinylation, microsome isolation, patch-clamp whole-cell recordings, and video-monitoring synchronized electroencephalographic (EEG) recordings in Gabrg2+/Q390X mice to determine the effect of PBA in vitro with recombinant GABAA receptors and in vivo with knockin mice. RESULTS: We found that PBA reduced the mutant γ2(Q390X) subunit protein aggregates, enhanced the wild-type GABAA receptor subunits' trafficking, and increased the membrane expression of the wild-type receptors. PBA increased the current amplitude of GABA-evoked current in human embryonic kidney 293T cells and the neurons bearing the γ2(Q390X) subunit protein. PBA also proved to reduce endoplasmic reticulum (ER) stress caused by the mutant γ2(Q390X) subunit protein, as well as mitigating seizures and EEG abnormalities in the Gabrg2+/Q390X mice. SIGNIFICANCE: This research has unveiled a promising and innovative approach for treating epilepsy linked to GABAA receptor mutations through an unconventional antiseizure mechanism. Rather than directly modulating the affected mutant channel, PBA facilitates the folding and transportation of wild-type receptor subunits to the cell membrane and synapse. Combining these findings with our previous study, which demonstrated PBA's efficacy in restoring GABA transporter 1 (encoded by SLC6A1) function, we propose that PBA holds significant potential for a wide range of genetic epilepsies. Its ability to target shared molecular pathways involving mutant protein ER retention and impaired protein membrane trafficking suggests broad application in treating such conditions.

Sodium phenylbutyrate-taurursodiol access, adherence and adverse event in patients with amyotrophic lateral sclerosis: Experience at one center in the United States.

INTRODUCTION/AIMS: Sodium phenylbutyrate-taurursodiol (PB-TURSO) was recently approved for treating amyotrophic lateral sclerosis (ALS). Third-party payors' coverage policies are evolving, and adverse events are just being fully assessed. The goals of this study were to evaluate patients' experiences in obtaining and continuing PB-TURSO and assess adverse events and medication adherence. METHODS: Medical records of 109 ALS patients who were considered PB-TURSO candidates by the treating physician at a tertiary ALS clinic from October 2022 to May 2023 were reviewed. Data was recorded for demographics, clinical, and insurance information. A survey was e-mailed to patients asking about out-of-pocket expenses for PB-TURSO, financial assistance, medication start and (if applicable) stop dates, and reasons for discontinuation. RESULTS: Insurance information was available for 91 patients [57 males (62%); mean age 64.8 years (range 25.7-88)]. Of 79 who applied for insurance approval, 71 (90%) were approved; however, 19 required 1-3 appeals. Among 73 patients with available data about medication status, 54 started PB-TURSO and 19 did not, most commonly due to personal choice or out-of-pocket expenses. About 44% of patients (24/54) stopped taking PB-TURSO, primarily due to adverse events. Monthly out-of-pocket expenses varied from $0 to $3500 and 36 patients qualified for financial assistance. Administrative and nursing staff devoted 7.2 hours/week to the insurance authorization process. DISCUSSION: Most patients received insurance approval for PB-TURSO, but one-fourth required appeals. Some out-of-pocket costs were very high. Investment of staff time was substantial. These findings have implications for insurance coverage of, and adherence to, future ALS treatments.

Sodium Phenylbutyrate and Taurursodiol: A New Therapeutic Option for the Treatment of Amyotrophic Lateral Sclerosis.

OBJECTIVE: To review the safety and efficacy of sodium phenylbutyrate and taurursodiol (SP + T) in slowing progression of amyotrophic lateral sclerosis (ALS) compared with pre-existing therapies. DATA SOURCES: A PubMed (from January 1, 2009, to April 13, 2023) and ClinicalTrials.gov search conducted using sodium phenylbutyrate, taurursodiol, AMX0035, riluzole, and edaravone. Additional articles were identified by hand from references. DATA SELECTION AND DATA EXTRACTION: This included English-language articles evaluating SP + T efficacy or safety in humans for decreasing neuronal death and slowing the progression of ALS. DATA SYNTHESIS: In one phase II clinical trial that encompassed an open-label extension phase, disease severity, assessed by the rate of decline in overall score on the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised with higher scores indicating more functional ability, was -1.24 points per month with active drug and -1.66 points per month with placebo (difference, 0.42 points per month; 95% CI, 0.03-0.81; P = 0.03). Post hoc analysis found survival benefit of median 4.8 months with active medication compared with placebo. RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE IN COMPARISON WITH EXISTING DRUGS: SP + T is a new US Food and Drug Administration-approved oral suspension for the treatment of ALS. Patients who received active medication through the phase II trial showed decreased rates of disease progression. Overall, SP + T could be considered a potential agent for the treatment of ALS which has a high unmet need. CONCLUSION: SP + T is an option for the treatment of ALS; however, additional data regarding efficacy in phase III trials with long-term safety profile considerations, as well as trials to compare current therapy with SP + T, are needed.

4-Phenylbutyric Acid Treatment Reduces Low-Molecular-Weight Proteinuria in a Clcn5 Knock-in Mouse Model for Dent Disease-1.

Dent disease-1 (DD-1) is a rare X-linked tubular disorder characterized by low-molecular-weight proteinuria (LMWP), hypercalciuria, nephrolithiasis and nephrocalcinosis. This disease is caused by inactivating mutations in the CLCN5 gene which encodes the voltage-gated ClC-5 chloride/proton antiporter. Currently, the treatment of DD-1 is only supportive and focused on delaying the progression of the disease. Here, we generated and characterized a Clcn5 knock-in mouse model that carries a pathogenic CLCN5 variant, c. 1566_1568delTGT; p.Val523del, which has been previously detected in several DD-1 unrelated patients, and presents the main clinical manifestations of DD-1 such as high levels of urinary b2-microglobulin, phosphate and calcium. Mutation p.Val523del causes partial ClC-5 retention in the endoplasmic reticulum. Additionally, we assessed the ability of sodium 4-phenylbutyrate, a small chemical chaperone, to ameliorate DD-1 symptoms in this mouse model. The proposed model would be of significant value in the investigation of the fundamental pathological processes underlying DD-1 and in the development of effective therapeutic strategies for this rare condition.

[Treatment of ornithine transcarbamylase deficiency in a child with glyceryl phenylbutyrate]. / è‹¯ä¸é ¸ç”˜æ²¹é ¯æ²»ç–—å„¿ç«¥é¸Ÿæ°¨é ¸æ°¨ç”²é °åŸºè½¬ç§»é ¶ç¼ºä¹ç—‡1例.

Glyceryl phenylbutyrate (GPB) serves as a long-term management medication for Ornithine transcarbamylase deficiency (OTCD), effectively controlling hyperammonemia, but there is a lack of experience in using this medicine in China. This article retrospectively analyzes the case of a child diagnosed with OTCD at Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, including a review of related literature. After diagnosis, the patient was treated with GPB, followed by efficacy follow-up and pharmacological monitoring. The 6-year and 6-month-old male patient exhibited poor speech development, disobedience, temper tantrums, and aggressive behavior. Blood ammonia levels peaked at 327 µmol/L; urine organic acid analysis indicated elevated uracil levels; cranial MRI showed extensive abnormal signals in both cerebral hemispheres. Genetic testing revealed de novo mutation in the OTC gene (c.241T>C, p.S81P). Blood ammonia levels were approximately 43, 80, and 56 µmol/L at 1, 2, and 3 months after starting GPB treatment, respectively. During treatment, blood ammonia was well-controlled without drug-related adverse effects. The patient showed improvement in developmental delays, obedience, temperament, and absence of aggressive behavior.

Clearance and production of ammonia quantified in humans by constant ammonia infusion - the effects of cirrhosis and ammonia-targeting treatments.

BACKGROUND & AIMS: Hyperammonaemia is a key pathological feature of liver disease and the primary driver of hepatic encephalopathy (HE). However, the relative roles of increased ammonia production and reduced clearance are poorly understood as is the action of ammonia-targeting drugs for HE. We aimed to quantify whole-body ammonia metabolism in healthy persons and patients with cirrhosis and to validate our method by examining the effects of glycerol phenylbutyrate and lactulose + rifaximin treatment. METHODS: Ten healthy men and ten male patients with cirrhosis were investigated by 90-minute constant ammonia infusion to achieve steady-state plasma ammonia. Whole-body ammonia clearance was calculated as infusion rate divided by steady-state concentration increase and ammonia production was calculated as clearance multiplied by baseline ammonia concentration. Participants were re-investigated after the ammonia-targeting interventions. RESULTS: In healthy persons, ammonia clearance was 3.5 (3.1-3.9) L/min and ammonia production was 49 (35-63) µmol/min. Phenylbutyrate increased clearance by 11% (4-19%, p = 0.009). In patients with cirrhosis, ammonia clearance was 20% lower at 2.7 (2.1-3.3) L/min (p = 0.02) and production was nearly threefold higher at 131 (102-159) µmol/min (p <0.0001). Lactulose + rifaximin reduced production by 20% (2-37%, p = 0.03). The infusion was generally well-tolerated apart from in one hyperammonaemic patient, with cirrhosis and possible bleeding unrelated to the infusion, who developed clinical HE that reverted when infusion was discontinued. CONCLUSIONS: Whole-body ammonia clearance and production may be measured separately using the described technique. This technique identified a lower clearance and a higher production of ammonia in patients with cirrhosis, and showed that phenylbutyrate increases clearance, whereas lactulose + rifaximin reduces production. IMPACT AND IMPLICATIONS: High blood ammonia plays a key role in cirrhosis-related brain dysfunction. However, the relative roles of reduced ammonia clearance and increased ammonia production are poorly understood as is the action of ammonia-targeting treatments. This study presents a relatively simple test to measure ammonia metabolism. By using this test, it was possible to show that patients with cirrhosis exhibit decreased ammonia clearance and increased ammonia production compared to healthy persons, and to quantify the unique effects of different ammonia-targeting treatments. The test described herein may be used to examine a range of questions related to normal physiology, pathophysiology and the mechanisms of action of ammonia-targeting treatments. CLINICAL TRIAL NUMBER: ClinicalTrials.gov (1-16-02-297-20).

Monitoring the treatment of urea cycle disorders using phenylbutyrate metabolite analyses: Still many lessons to learn.

Medications that elicit an alternate pathway for nitrogen excretion such as oral sodium phenylbutyrate (NaPBA) and glycerol phenylbutyrate (GPB) and intravenous sodium phenylacetate (NaPAA) are important for the management of urea cycle disorders (UCDs). Plasma concentrations of their primary metabolite, phenylacetate (PAA), as well as the ratio of PAA to phenylacetylglutamine (PAGN) are useful for guiding dosing and detecting toxicity. However, the frequency of toxic elevations of metabolites and associated clinical covariates is relatively unknown. A retrospective analysis was conducted on 1255 plasma phenylbutyrate metabolite measurements from 387 individuals. An additional analysis was also conducted on a subset of 68 individuals in whom detailed clinical information was available. In the course of these analyses, abnormally elevated plasma PAA and PAA:PAGN were identified in 39 individuals (4.15% of samples) and 42 individuals (4.30% of samples), respectively. Abnormally elevated PAA and PAA:PAGN values were more likely to occur in younger individuals and associate positively with dose of NAPBA and negatively with plasma glutamine and glycine levels. These results demonstrate that during routine clinical management, the majority of patients have PAA levels that are deemed safe. As age is negatively associated with PAA levels however, children undergoing treatment with NaPBA may need close monitoring of their phenylbutyrate metabolite levels.

Taste-masked formulation of sodium phenylbutyrate (ACER-001) for the treatment of urea cycle disorders.

Urea cycle disorders (UCDs) are a group of rare inherited metabolic diseases caused by a deficiency of one of the enzymes or transporters that constitute the urea cycle. Defects in these enzymes lead to acute accumulation (hyperammonemic crises, HAC) or chronically elevated levels (hyperammonemia) of ammonia in the blood and/or various tissues including the brain, which can cause persistent neurological deficits, irreversible brain damage, coma, and death. Ongoing treatment of UCDs include the use of nitrogen-scavenging agents, such as sodium phenylbutyrate (salt of 4-phenylbutyric acid; NaPBA) or glycerol phenylbutyrate (GPB). These treatments provide an alternative pathway for nitrogen disposal through the urinary excretion of phenylacetylglutamine. ACER-001 is a novel formulation of NaPBA with polymer coated pellets in suspension, which is designed to briefly mask the unpleasant bitter taste of NaPBA and is being developed as a treatment option for patients with UCDs. Four Phase 1 studies were conducted to characterize the bioavailability (BA) and/or bioequivalence (BE) of ACER-001 (in healthy volunteers) and taste assessment relative to NaPBA powder (in taste panelists). ACER-001 was shown to be bioequivalent to NaPBA powder under both fed and fasting conditions. Lower systemic exposure of phenylacetate (PAA) and phenylbutyrate (PBA) was observed when ACER-001 was administered with a high-fat meal relative to a fasting state suggesting that the lower doses of PBA administered under fasting conditions may yield similar efficacy with potentially fewer dose dependent adverse effects relative to higher doses with a meal. ACER-001 appeared to be adequately taste-masked, staying below the aversive taste threshold for the first 3 min after the formulation was prepared and remaining palatable when taken within 5 min.

Experimental and Bioinformatic Insights into the Effects of Epileptogenic Variants on the Function and Trafficking of the GABA Transporter GAT-1.

In this article, we identified a novel epileptogenic variant (G307R) of the gene SLC6A1, which encodes the GABA transporter GAT-1. Our main goal was to investigate the pathogenic mechanisms of this variant, located near the neurotransmitter permeation pathway, and compare it with other variants located either in the permeation pathway or close to the lipid bilayer. The mutants G307R and A334P, close to the gates of the transporter, could be glycosylated with variable efficiency and reached the membrane, albeit inactive. Mutants located in the center of the permeation pathway (G297R) or close to the lipid bilayer (A128V, G550R) were retained in the endoplasmic reticulum. Applying an Elastic Network Model, to these and to other previously characterized variants, we found that G307R and A334P significantly perturb the structure and dynamics of the intracellular gate, which can explain their reduced activity, while for A228V and G362R, the reduced translocation to the membrane quantitatively accounts for the reduced activity. The addition of a chemical chaperone (4-phenylbutyric acid, PBA), which improves protein folding, increased the activity of GAT-1WT, as well as most of the assayed variants, including G307R, suggesting that PBA might also assist the conformational changes occurring during the alternative access transport cycle.

Study of the Structural Chemistry of the Inclusion Complexation of 4-Phenylbutyrate and Related Compounds with Cyclodextrins in Solution: Differences in Inclusion Mode with Cavity Size Dependency.

4-phenylbutyrate (PB) and structurally related compounds hold promise for treating many diseases, including cancers. However, pharmaceutical limitations, such as an unpleasant taste or poor aqueous solubility, impede their evaluation and clinical use. This study explores cyclodextrin (CD) complexation as a strategy to address these limitations. The structural chemistry of the CD complexes of these compounds was analyzed using phase solubility, nuclear magnetic resonance (NMR) spectroscopic techniques, and molecular modeling to inform the choice of CD for such application. The study revealed that PB and its shorter-chain derivative form 1:1 αCD complexes, while the longer-chain derivatives form 1:2 (guest:host) complexes. αCD includes the alkyl chain of the shorter-chain compounds, depositing the phenyl ring around its secondary rim, whereas two αCD molecules sandwich the phenyl ring in a secondary-to-secondary rim orientation for the longer-chain derivatives. ßCD includes each compound to form 1:1 complexes, with their alkyl chains bent to varying degrees within the CD cavity. γCD includes two molecules of each compound to form 2:1 complexes, with both parallel and antiparallel orientations plausible. The study found that αCD is more suitable for overcoming the pharmaceutical drawbacks of PB and its shorter-chain derivative, while ßCD is better for the longer-chain derivatives.

Misfolding, altered membrane distributions, and the unfolded protein response contribute to pathogenicity differences in Na,K-ATPase ATP1A3 mutations.

Missense mutations in ATP1A3, the α3 isoform of Na,K-ATPase, cause neurological phenotypes that differ greatly in symptoms and severity. A mechanistic basis for differences is lacking, but reduction of activity alone cannot explain them. Isogenic cell lines with endogenous α1 and inducible exogenous α3 were constructed to compare mutation properties. Na,K-ATPase is made in the endoplasmic reticulum (ER), but the glycan-free catalytic α subunit complexes with glycosylated ß subunit in the ER to proceed through Golgi and post-Golgi trafficking. We previously observed classic evidence of protein misfolding in mutations with severe phenotypes: differences in ER retention of endogenous ß1 subunit, impaired trafficking of α3, and cytopathology, suggesting that they misfold during biosynthesis. Here we tested two mutations associated with different phenotypes: D923N, which has a median age of onset of hypotonia or dystonia at 3 years, and L924P, with severe infantile epilepsy and profound impairment. Misfolding during biosynthesis in the ER activates the unfolded protein response, a multiarmed program that enhances protein folding capacity, and if that fails, triggers apoptosis. L924P showed more nascent protein retention in ER than D923N; more ER-associated degradation of α3 (ERAD); larger differences in Na,K-ATPase subunit distributions among subcellular fractions; and greater inactivation of eIF2α, a major defensive step of the unfolded protein response. In L924P there was also altered subcellular distribution of endogenous α1 subunit, analogous to a dominant negative effect. Both mutations showed pro-apoptotic sensitization by reduced phosphorylation of BAD. Encouragingly, however, 4-phenylbutyrate, a pharmacological corrector, reduced L924P ER retention, increased α3 expression, and restored morphology.

COL4A1 Mutations Cause Neuromuscular Disease with Tissue-Specific Mechanistic Heterogeneity.

Collagen type IV alpha 1 and alpha 2 chains form heterotrimers ([α1(IV)]2α2(IV)) that represent a fundamental basement membrane constituent. Dominant COL4A1 and COL4A2 mutations cause a multisystem disorder that is marked by clinical heterogeneity and variable expressivity and that is generally characterized by the presence of cerebrovascular disease with ocular, renal, and muscular involvement. Despite the fact that muscle pathology is reported in up to one-third of individuals with COL4A1 and COL4A2 mutations and in animal models with mutations in COL4A1 and COL4A2 orthologs, the pathophysiological mechanisms underlying COL4A1-related myopathy are unknown. In general, mutations are thought to impair [α1(IV)]2α2(IV) secretion. Whether pathogenesis results from intracellular retention, extracellular deficiency, or the presence of mutant proteins in basement membranes represents an important gap in knowledge and a major obstacle for developing targeted interventions. We report that Col4a1 mutant mice develop progressive neuromuscular pathology that models human disease. We demonstrate that independent muscular, neural, and vascular insults contribute to neuromyopathy and that there is mechanistic heterogeneity among tissues. Importantly, we provide evidence of a COL4A1 functional subdomain with disproportionate significance for tissue-specific pathology and demonstrate that a potential therapeutic strategy aimed at promoting [α1(IV)]2α2(IV) secretion can ameliorate or exacerbate myopathy in a mutation-dependent manner. These data have important translational implications for prediction of clinical outcomes based on genotype, development of mechanism-based interventions, and genetic stratification for clinical trials. Collectively, our data underscore the importance of the [α1(IV)]2α2(IV) network as a multifunctional signaling platform and show that allelic and tissue-specific mechanistic heterogeneities contribute to the variable expressivity of COL4A1 and COL4A2 mutations.

Perceptions and use of phenylbutyrate metabolite testing in urea cycle disorders: Results of a clinician survey and analysis of a centralized testing database.

The nitrogen scavengers sodium and glycerol phenylbutyrate (PB), approved for chronic treatment of urea cycle disorders (UCDs), undergo hepatic conversion to phenylacetate (PAA), which conjugates glutamine to form phenylacetylglutamine for urinary nitrogen excretion. Elevated PAA has been associated with reversible neurological toxicity, with symptoms similar to hyperammonemia. Plasma PB metabolite analysis can assess for toxicity and therapeutic drug levels. An online survey was undertaken to assess US clinician perceptions and use of the test in addition to an analysis of centralized US laboratory records. Survey responses from 52 clinicians were analyzed, including 58% who reported using plasma PB metabolite testing. Test users reported managing more UCD patients than nonusers. Users rated the test as "often helpful" for ruling out PAA toxicity (44%), informing PB dosing decisions (42%), and assessing adherence (28%). Test results were reported as most often unremarkable (61%) or suggestive of poor adherence (13%); 46% of users had never encountered results indicative of PAA toxicity. Analyses of laboratory records for 1668 plasma metabolite tests determined that only 5% of samples had plasma PAA-to-phenylacetylglutamine ratios associated with increased risk of PAA toxicity. Nearly half of surveyed clinicians were unsure of metabolite targets; those conducting ad hoc (versus regular) testing were significantly more likely to be unsure of targets. One-fifth of test users identified uncertainties, including questions about test validation, timing, and interpretation. Increased awareness of published PB metabolite data and further clinician education on test interpretation may help to inform the use of metabolite testing to optimize UCD care.

Survival analyses from the CENTAUR trial in amyotrophic lateral sclerosis: Evaluating the impact of treatment crossover on outcomes.

INTRODUCTION/AIMS: Trials incorporating placebo-to-active treatment crossover are encouraged in fatal conditions like amyotrophic lateral sclerosis (ALS) but may underestimate active treatment survival benefit. Here, we apply methods for modeling survival without crossover, including the rank-preserving structural failure time model (RPSFTM), to data from the CENTAUR trial of sodium phenylbutyrate and taurursodiol (PB and TURSO) in ALS incorporating both randomized placebo-controlled and open-label extension (OLE) phases. METHODS: Intent-to-treat (ITT) and RPSFTM survival analyses were performed with final data at a July 2020 cutoff date. Analyses of subgroups based on randomized treatment and OLE phase participation were also performed. RESULTS: Hazard ratios (95% confidence intervals) of death for PB and TURSO versus participants initially on placebo were 0.57 (0.35-0.92) on ITT analysis and 0.39 (0.17-0.88) in the primary on-treatment RPSFTM analysis (p = .023). Median ITT survival duration for PB and TURSO (25.8 mo) was 6.9 mo longer than placebo (18.9 mo) on ITT analysis and 10.6 mo longer than the median RPSFTM-adjusted survival duration for placebo (15.2 mo). Median survival duration was 18.8 mo longer in the PB and TURSO-randomized subgroup who continued into the OLE phase versus the placebo-randomized subgroup who did not continue into the OLE phase (p < .0001), although OLE phase selection bias may have potentially confounded these results. DISCUSSION: Similar to the prespecified ITT analysis, post hoc analyses adjusting for treatment crossover in CENTAUR showed a significant survival benefit for PB and TURSO. Such methods may provide clinical context for observed survival outcomes in future ALS crossover trials.

Effects of MgSO4 Alone or Associated with 4-PBA on Behavior and White Matter Integrity in a Mouse Model of Cerebral Palsy: A Sex- and Time-Dependent Study.

Cerebral palsy (CP) is defined as permanent disorders of movement and posture. Prematurity and hypoxia-ischemia (HI) are risk factors of CP, and boys display a greater vulnerability to develop CP. Magnesium sulfate (MgSO4) is administered to mothers at risk of preterm delivery as a neuroprotective agent. However, its effectiveness is only partial at long term. To prolong MgSO4 effects, it was combined with 4-phenylbutyrate (4-PBA). A mouse model of neonatal HI, generating lesions similar to those reported in preterms, was realized. At short term, at the behavioral and cellular levels, and in both sexes, the MgSO4/4-PBA association did not alter the total prevention induced by MgSO4 alone. At long term, the association extended the MgSO4 preventive effects on HI-induced motor and cognitive deficits. This might be sustained by the promotion of oligodendrocyte precursor differentiation after HI at short term, which led to improvement of white matter integrity at long term. Interestingly, at long term, at a behavioral level, sex-dependent responses to HI were observed. This might partly be explained by early sex-dependent pathological processes that occur after HI. Indeed, at short term, apoptosis through mitochondrial pathways seemed to be activated in females but not in males, and only the MgSO4/4-PBA association seemed to counter this apoptotic process.

Immunomodulatory Agents Combat Multidrug-Resistant Tuberculosis by Improving Antimicrobial Immunity.

BACKGROUND: Multidrug-resistant (MDR) tuberculosis has low treatment success rates, and new treatment strategies are needed. We explored whether treatment with active vitamin D3 (vitD) and phenylbutyrate (PBA) could improve conventional chemotherapy by enhancing immune-mediated eradication of Mycobacterium tuberculosis. METHODS: A clinically relevant model was used consisting of human macrophages infected with M. tuberculosis isolates (n = 15) with different antibiotic resistance profiles. The antimicrobial effect of vitD+PBA, was tested together with rifampicin or isoniazid. Methods included colony-forming units (intracellular bacterial growth), messenger RNA expression analyses (LL-37, ß-defensin, nitric oxide synthase, and dual oxidase 2), RNA interference (LL-37-silencing in primary macrophages), and Western blot analysis and confocal microscopy (LL-37 and LC3 protein expression). RESULTS: VitD+PBA inhibited growth of clinical MDR tuberculosis strains in human macrophages and strengthened intracellular growth inhibition of rifampicin and isoniazid via induction of the antimicrobial peptide LL-37 and LC3-dependent autophagy. Gene silencing of LL-37 expression enhanced MDR tuberculosis growth in vitD+PBA-treated macrophages. The combination of vitD+PBA and isoniazid were as effective in reducing intracellular MDR tuberculosis growth as a >125-fold higher dose of isoniazid alone, suggesting potent additive effects of vitD+PBA with isoniazid. CONCLUSIONS: Immunomodulatory agents that trigger multiple immune pathways can strengthen standard MDR tuberculosis treatment and contribute to next-generation individualized treatment options for patients with difficult-to-treat pulmonary tuberculosis.

Small molecules restore the function of mutant CLC5 associated with Dent disease.

Dent disease type 1 is caused by mutations in the CLCN5 gene that encodes CLC5, a 2Cl- /H+ exchanger. The CLC5 mutants that have been functionally analysed constitute three major classes based on protein expression, cellular localization and channel function. We tested two small molecules, 4-phenylbutyrate (4PBA) and its analogue 2-naphthoxyacetic acid (2-NOAA), for their effect on mutant CLC5 function and expression by whole-cell patch-clamp and Western blot, respectively. The expression and function of non-Class I CLC5 mutants that have reduced function could be restored by either treatment. Cell viability was reduced in cells treated with 2-NOAA. 4PBA is a FDA-approved drug for the treatment of urea cycle disorders and offers a potential therapy for Dent disease.

Glycerol phenylbutyrate efficacy and safety from an open label study in pediatric patients under 2 months of age with urea cycle disorders.

BACKGROUND/AIMS: Neonatal onset Urea cycle disorders (UCDs) can be life threatening with severe hyperammonemia and poor neurological outcomes. Glycerol phenylbutyrate (GPB) is safe and effective in reducing ammonia levels in patients with UCD above 2 months of age. This study assesses safety, ammonia control and pharmacokinetics (PK) of GPB in UCD patients below 2 months of age. METHODS: This was an open-label study in UCD patients aged 0 - 2 months, consisting of an initiation/transition period (1 - 4 days) to GPB, followed by a safety extension period (6 months to 2 years). Patients presenting with a hyperammonemic crisis (HAC) did not initiate GPB until blood ammonia levels decreased to below 100 µmol/L while receiving sodium phenylacetate/sodium benzoate and/or hemodialysis. Ammonia levels, PK analytes and safety were evaluated during transition and monthly during the safety extension for 6 months and every 3 months thereafter. RESULTS: All 16 patients with UCD (median age 0.48 months, range 0.1 to 2.0 months) successfully transitioned to GPB within 3 days. Average plasma ammonia level excluding HAC was 94.3 µmol/L at baseline and 50.4 µmol/L at the end of the transition period (p = 0.21). No patient had a HAC during the transition period. During the safety extension, the majority of patients had controlled ammonia levels, with mean plasma ammonia levels lower during GPB treatment than baseline. Mean glutamine levels remained within normal limits throughout the study. PK analyses indicate that UCD patients <2 months are able to hydrolyze GPB with subsequent absorption of phenylbutyric acid (PBA), metabolism to phenylacetic acid (PAA) and conjugation with glutamine. Plasma concentrations of PBA, PAA, and phenylacetylglutamine (PAGN) were stable during the safety extension phase and mean plasma phenylacetic acid: phenylacetylglutamine ratio remained below 2.5 suggesting no accumulation of GPB. All patients reported at least 1 treatment emergent adverse event with gastroesophageal reflux disease, vomiting, hyperammonemia, diaper dermatitis (37.5% each), diarrhea, upper respiratory tract infection and rash (31.3% each) being the most frequently reported. CONCLUSIONS: This study supports safety and efficacy of GPB in UCD patients aged 0 -2 months who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. GPB undergoes intestinal hydrolysis with no accumulation in this population.