Long-term comparative effectiveness of pegvaliase versus medical nutrition therapy with and without sapropterin in adults with phenylketonuria.

Phenylketonuria is characterized by intellectual disability and behavioral, psychiatric, and movement disorders resulting from phenylalanine (Phe) accumulation. Standard-of-care treatment involves a Phe-restricted diet plus medical nutrition therapy (MNT), with or without sapropterin dihydrochloride, to reduce blood Phe levels. Pegvaliase is an injectable enzyme substitution treatment approved for adult patients with blood Phe >600 µmol/L despite ongoing management. A previous comparative effectiveness analysis using data from the Phase 3 PRISM trials of pegvaliase (NCT01819727 and NCT01889862) and the Phenylketonuria Demographics, Outcomes and Safety Registry (PKUDOS; NCT00778206) suggested that pegvaliase was more effective at lowering mean blood Phe levels than sapropterin + MNT or MNT alone at 1 and 2 years of treatment. The current work augments and complements the previous analysis by including additional follow-up from the completed studies, robust methods reflecting careful consideration of issues with the distribution of Phe, and alternative methods for adjustment that are important for control of potential confounding in comparative effectiveness. Median blood Phe levels were lower, and median intact protein intakes were higher, in the pegvaliase group (n = 183) than in the sapropterin + MNT (n = 82) and MNT (n = 67) groups at Years 1, 2, and 3. In the pegvaliase group, median blood Phe levels decreased from baseline (1244 µmol/L) to Year 1 (535 µmol/L), Year 2 (142 µmol/L), and Year 3 (167 µmol/L). In the sapropterin + MNT group, median blood Phe levels decreased from baseline (900 µmol/L) to Year 1 (588 µmol/L) and Year 2 (592 µmol/L), and increased at Year 3 (660 µmol/L). In the MNT group, median blood Phe levels decreased slightly from baseline (984 µmol/L) to Year 1 (939 µmol/L) and Year 2 (941 µmol/L), and exceeded baseline levels at Year 3 (1157 µmol/L). The model-estimated proportions of participants achieving blood Phe ≤600 µmol/L were 41%, 100%, and 100% in the pegvaliase group at Years 1, 2, and 3, respectively, compared with 55%, 58%, and 38% in the sapropterin + MNT group and 5%, 16%, and 0% in the MNT group. The estimated proportions of participants achieving more stringent blood Phe targets of ≤360 µmol/L and ≤120 µmol/L were also higher in the pegvaliase group than in the other groups at Years 2 and 3. Overall, our results indicate that, compared with standard therapy, pegvaliase induces a substantial, progressive, and sustained decrease in blood Phe levels - to a much greater extent than sapropterin + MNT or MNT alone - which is expected to improve long-term outcomes in patients with phenylketonuria.

Challenges and strategies for clinical trials in propionic and methylmalonic acidemias.

Clinical trial development in rare diseases poses significant study design and methodology challenges, such as disease heterogeneity and appropriate patient selection, identification and selection of key endpoints, decisions on study duration, choice of control groups, selection of appropriate statistical analyses, and patient recruitment. Therapeutic development in organic acidemias (OAs) shares many challenges with other inborn errors of metabolism, such as incomplete understanding of natural history, heterogenous disease presentations, requirement for sensitive outcome measures and difficulties recruiting a small sample of participants. Here, we review strategies for the successful development of a clinical trial to evaluate treatment response in propionic and methylmalonic acidemias. Specifically, we discuss crucial decisions that may significantly impact success of the study, including patient selection, identification and selection of endpoints, determination of the study duration, consideration of control groups including natural history controls, and selection of appropriate statistical analyses. The significant challenges associated with designing a clinical trial in rare disease can sometimes be successfully met through strategic engagement with experts in the rare disease, seeking regulatory and biostatistical guidance, and early involvement of patients and families.

Distinct effects on mRNA export factor GANP underlie neurological disease phenotypes and alter gene expression depending on intron content.

Defects in the mRNA export scaffold protein GANP, encoded by the MCM3AP gene, cause autosomal recessive early-onset peripheral neuropathy with or without intellectual disability. We extend here the phenotypic range associated with MCM3AP variants, by describing a severely hypotonic child and a sibling pair with a progressive encephalopathic syndrome. In addition, our analysis of skin fibroblasts from affected individuals from seven unrelated families indicates that disease variants result in depletion of GANP except when they alter critical residues in the Sac3 mRNA binding domain. GANP depletion was associated with more severe phenotypes compared with the Sac3 variants. Patient fibroblasts showed transcriptome alterations that suggested intron content-dependent regulation of gene expression. For example, all differentially expressed intronless genes were downregulated, including ATXN7L3B, which couples mRNA export to transcription activation by association with the TREX-2 and SAGA complexes. Our results provide insight into the molecular basis behind genotype-phenotype correlations in MCM3AP-associated disease and suggest mechanisms by which GANP defects might alter RNA metabolism.

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.

Clinical effect and safety profile of pegzilarginase in patients with arginase 1 deficiency.

Hyperargininemia in patients with arginase 1 deficiency (ARG1-D) is considered a key driver of disease manifestations, including spasticity, developmental delay, and seizures. Pegzilarginase (AEB1102) is an investigational enzyme therapy which is being developed as a novel arginine lowering approach. We report the safety and efficacy of intravenously (IV) administered pegzilarginase in pediatric and adult ARG1-D patients (n = 16) from a Phase 1/2 study (101A) and the first 12 weeks of an open-label extension study (102A). Substantial disease burden at baseline included lower-limb spasticity, developmental delay, and previous hyperammonemic episodes in 75%, 56%, and 44% of patients, respectively. Baseline plasma arginine (pArg) was elevated (median 389 µM, range 238-566) on standard disease management. Once weekly repeat dosing resulted in a median decrease of pArg of 277 µM after 20 cumulative doses (n = 14) with pArg in the normal range (40 to 115 µM) in 50% of patients at 168 hours post dose (mean pegzilarginase dose 0.10 mg/kg). Lowering pArg was accompanied by improvements in one or more key mobility assessments (6MWT, GMFM-D & E) in 79% of patients. In 101A, seven hypersensitivity reactions occurred in four patients (out of 162 infusions administered). Other common treatment-related adverse events (AEs) included vomiting, hyperammonemia, pruritus, and abdominal pain. Treatment-related serious AEs that occurred in five patients were all observed in 101A. Pegzilarginase was effective in lowering pArg levels with an accompanying clinical response in patients with ARG1-D. The improvements with pegzilarginase occurred in patients receiving standard treatment approaches, which suggests that pegzilarginase could offer benefit over existing disease management.

Evidence- and consensus-based recommendations for the use of pegvaliase in adults with phenylketonuria.

PURPOSE: Phenylketonuria (PKU) is a rare metabolic disorder that requires life-long management to reduce phenylalanine (Phe) concentrations within the recommended range. The availability of pegvaliase (PALYNZIQ™, an enzyme that can metabolize Phe) as a new therapy necessitates the provision of guidance for its use. METHODS: A Steering Committee comprising 17 health-care professionals with experience in using pegvaliase through the clinical development program drafted guidance statements during a series of face-to-face meetings. A modified Delphi methodology was used to demonstrate consensus among a wider group of health-care professionals with experience in using pegvaliase. RESULTS: Guidance statements were developed for four categories: (1) treatment goals and considerations prior to initiating therapy, (2) dosing considerations, (3) considerations for dietary management, and (4) best approaches to optimize medical management. A total of 34 guidance statements were included in the modified Delphi voting and consensus was reached on all after two rounds of voting. CONCLUSION: Here we describe evidence- and consensus-based recommendations for the use of pegvaliase in adults with PKU. The manuscript was evaluated against the Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument and is intended for use by health-care professionals who will prescribe pegvaliase and those who will treat patients receiving pegvaliase.

Long-term comparative effectiveness of pegvaliase versus standard of care comparators in adults with phenylketonuria.

Phenylketonuria (PKU) is caused by phenylalanine hydroxylase (PAH) deficiency, resulting in high blood and brain Phenylalanine (Phe) concentrations that can lead to impaired brain development and function. Standard treatment involves a Phe-restricted diet alone or in conjunction with sapropterin dihydrochloride in responsive patients. The Food and Drug Administration approved pegvaliase enzyme substitution therapy for adults with blood Phe >600 µmol/L in the US. Recently, the European Commission also approved pegvaliase for treatment of PKU patients aged 16 years or older with blood Phe >600 µmol/L. The analyses presented below were conducted to provide comparative evidence on long-term treatment effectiveness of pegvaliase versus standard of care in adults with PKU. Adult patients (≥18 years) with baseline blood Phe >600 µmol/L who had enrolled in the pegvaliase phase 2 and phase 3 clinical trials were propensity score-matched to historical cohorts of patients treated with "sapropterin + diet" or with "diet alone". These cohorts were derived from the PKU Demographics, Outcome and Safety (PKUDOS) registry and compared for clinical outcomes including blood Phe concentration and natural intact protein intake after 1 and 2 years. Propensity scores were estimated using logistic regression with probability of treatment as outcome (i.e. pegvaliase, "sapropterin + diet", or "diet alone") and patient demographic and disease severity covariates as predictors. An additional analysis in adult PKU patients with baseline blood Phe ≤600 µmol/L comparing non-matched patient groups "sapropterin + diet" to "diet alone" using PKUDOS registry data only was also conducted. The analyses in patients with baseline blood Phe >600 µmol comparing pegvaliase with "sapropterin + diet" (N = 64 matched pairs) showed lower mean blood Phe concentrations after 1 and 2 years with pegvaliase (505 and 427 µmol/L) versus "sapropterin + diet" (807 and 891 µmol/L); mean natural intact protein intake after 1 and 2 years was 49 and 57 g/day respectively with pegvaliase versus 23 and 28 g/day with "sapropterin + diet". The analysis comparing pegvaliase with "diet alone" (N = 120 matched pairs) showed lower mean blood Phe at 1 and 2 years with pegvaliase (473 and 302 µmol/L) versus "diet alone" (1022 and 965 µmol/L); mean natural intact protein intake after 1 and 2 years was 47 and 57 g/day with pegvaliase and 27 and 22 g/day with "diet alone". Considerably more patients achieved blood Phe ≤600, ≤360, and ≤120 µmol/L and reductions from baseline of ≥20%, ≥30%, and ≥50% in blood Phe after 1 and 2 years of pegvaliase versus standard treatments. The analysis in patients with baseline blood Phe ≤600 µmol/L showed lower blood Phe after 1 and 2 years with "sapropterin + diet" (240 and 324 µmol/L) versus "diet alone" (580 and 549 µmol/L) and greater percentages of patients achieving blood Phe targets ≤600, ≤360, and ≤120 µmol/L and reductions from baseline of ≥20%, ≥30%, and ≥50% in blood Phe. These results support pegvaliase as the more effective treatment option to lower Phe levels in adults with PKU who have difficulty keeping blood Phe ≤600 µmol/L with "diet alone". For patients with blood Phe ≤600 µmol/L, adding sapropterin to dietary management is an appropriate treatment option, for those responsive to the treatment.

Long-term safety and efficacy of glycerol phenylbutyrate for the management of urea cycle disorder patients.

INTRODUCTION: Glycerol phenylbutyrate (GPB) is currently approved for use in the US and Europe for patients of all ages with urea cycle disorders (UCD) who cannot be managed with protein restriction and/or amino acid supplementation alone. Currently available data on GPB is limited to 12 months exposure. Here, we present long-term experience with GPB. METHODS: This was an open-label, long-term safety study of GPB conducted in the US (17 sites) and Canada (1 site) monitoring the use of GPB in UCD patients who had previously completed 12 months of treatment in the previous safety extension studies. Ninety patients completed the previous studies with 88 of these continuing into the long-term evaluation. The duration of therapy was open ended until GPB was commercially available. The primary endpoint was the rate of adverse events (AEs). Secondary endpoints were venous ammonia levels, number and causes of hyperammonemic crises (HACs) and neuropsychological testing. RESULTS: A total of 45 pediatric patients between the ages of 1 to 17 years (median 7 years) and 43 adult patients between the ages of 19 and 61 years (median 30 years) were enrolled. The treatment emergent adverse events (TEAE) reported in ≥10% of adult or pediatric patients were consistent with the TEAEs reported in the previous safety extension studies with no increase in the overall incidence of TEAEs and no new TEAEs that indicated a new safety signal. Mean ammonia levels remained stable and below the adult upper limit of normal (<35 µmol/L) through 24 months of treatment in both the pediatric and adult population. Over time, glutamine levels decreased in the overall population. The mean annualized rate of HACs (0.29) established in the previously reported 12-month follow-up study was maintained with continued GPB exposure. CONCLUSION: Following the completion of 12-month follow-up studies with GPB treatment, UCD patients were followed for an additional median of 1.85 (range 0 to 5.86) years in the present study with continued maintenance of ammonia control, similar rates of adverse events, and no new adverse events identified.

Induction, titration, and maintenance dosing regimen in a phase 2 study of pegvaliase for control of blood phenylalanine in adults with phenylketonuria.

BACKGROUND: Phenylketonuria (PKU) is caused by a deficiency in phenylalanine hydroxylase enzyme activity that leads to phenylalanine (Phe) accumulation in the blood and brain. Elevated blood Phe levels are associated with complications in adults, including neurological, psychiatric, and cognitive issues. Even with nutrition and pharmacological management, the majority of adults with PKU do not maintain blood Phe levels at or below guideline recommended levels. Pegvaliase, PEGylated recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL), converts Phe to trans-cinnamic acid and ammonia, and is an investigational enzyme substitution therapy to lower blood Phe in adults with PKU. METHODS: Pegvaliase was administered using an induction, titration, and maintenance dosing regimen in adults with PKU naïve to pegvaliase treatment. Doses were gradually increased until blood Phe ≤ 600 µmol/L was achieved. The maintenance dose was the dose at which participants achieved and sustained blood Phe ≤ 600 µmol/L for at least 4 weeks without dose modification. Analyses were performed for participants who achieved (Group A, n = 11) and did not achieve (Group B, n = 13) maintenance dose during the first 24 weeks of study treatment. RESULTS: Baseline mean blood Phe for Group A and Group B were 1135 µmol/L and 1198 µmol/L, respectively. Mean blood Phe ≤ 600 µmol/L was achieved for Group A by Week 11 (mean blood Phe of 508 ±â€¯483 µmol/L) and for Group B by Week 48 (mean blood Phe of 557 ±â€¯389 µmol/L). The most common adverse events involved hypersensitivity reactions, which were mostly mild to moderate in severity and decreased over time. One participant in Group B had four acute systemic hypersensitivity events of anaphylaxis consistent with clinical National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network criteria; all events were non-IgE mediated and resolved without sequelae, with pegvaliase dosing discontinued after the fourth event. The incidence and titers of anti-drug antibodies were generally lower in Group A compared to Group B. CONCLUSIONS: Pegvaliase administered with an induction, titration, and maintenance dosing regimen demonstrated substantial efficacy at reducing blood Phe in both Group A and Group B by Week 48, with a manageable safety profile in most participants. Blood Phe reduction due to pegvaliase appears to be related to dose, treatment duration, and individual immune response; given additional time on treatment and dose titration, later Phe responders (Group B) achieved benefit similar to early Phe responders (Group A), with similar long-term safety profiles.

Pharmacokinetics of glycerol phenylbutyrate in pediatric patients 2 months to 2 years of age with urea cycle disorders.

INTRODUCTION: Glycerol phenylbutyrate (GPB) is approved in the US and EU for the chronic management of patients ≥2 months of age with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. GPB is a pre-prodrug, hydrolyzed by lipases to phenylbutyric acid (PBA) that upon absorption is beta-oxidized to the active nitrogen scavenger phenylacetic acid (PAA), which is conjugated to glutamine (PAGN) and excreted as urinary PAGN (UPAGN). Pharmacokinetics (PK) of GPB were examined to see if hydrolysis is impaired in very young patients who may lack lipase activity. METHODS: Patients 2 months to <2 years of age with UCDs from two open label studies (n = 17, median age 10 months) predominantly on stable doses of nitrogen scavengers (n = 14) were switched to GPB. Primary assessments included traditional plasma PK analyses of PBA, PAA, and PAGN, using noncompartmental methods with WinNonlin™. UPAGN was collected periodically throughout the study up to 12 months. RESULTS: PBA, PAA and PAGN rapidly appeared in plasma after GPB dosing, demonstrating evidence of GPB cleavage with subsequent PBA absorption. Median concentrations of PBA, PAA and PAGN did not increase over time and were similar to or lower than the values observed in older UCD patients. The median PAA/PAGN ratio was well below one over time, demonstrating that conjugation of PAA with glutamine to form PAGN did not reach saturation. Covariate analyses indicated that age did not influence the PK parameters, with body surface area (BSA) being the most significant covariate, reinforcing current BSA based dosing recommendations as seen in older patients. CONCLUSION: These observations demonstrate that UCD patients aged 2 months to <2 years have sufficient lipase activity to adequately convert the pre-prodrug GPB to PBA. PBA is then converted to its active moiety (PAA) providing successful nitrogen scavenging even in very young children.

Pegvaliase for the treatment of phenylketonuria: Results of a long-term phase 3 clinical trial program (PRISM).

BACKGROUND: Phenylketonuria (PKU) is caused by phenylalanine hydroxylase (PAH) deficiency that results in phenylalanine (Phe) accumulation. Pegvaliase, PEGylated recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL), converts Phe to trans-cinnamic acid and ammonia, and is a potential enzyme substitution therapy to lower blood Phe in adults with PKU. METHODS: Two Phase 3 studies, PRISM-1 and PRISM-2, evaluated the efficacy and safety of pegvaliase treatment using an induction, titration, and maintenance dosing regimen in adults with PKU. In PRISM-1, pegvaliase-naïve participants with blood Phe >600 µmol/L were randomized 1:1 to a maintenance dose of 20 mg/day or 40 mg/day of pegvaliase. Participants in PRISM-1 continued pegvaliase treatment in PRISM-2, a 4-part clinical trial that includes an ongoing, open-label, long-term extension study of pegvaliase doses of 5 mg/day to 60 mg/day. RESULTS: Of 261 participants who received pegvaliase treatment, 72.0% and 32.6% reached ≥12 months and ≥ 24 months of study treatment, respectively, and 65% are still actively receiving treatment. Mean (SD) blood Phe was 1232.7 (386.4) µmol/L at baseline, 564.5 (531.2) µmol/L at 12 months, and 311.4 (427) µmol/L at 24 months, a decrease from baseline of 51.1% and 68.7%, respectively. Within 24 months, 68.4% of participants achieved blood Phe ≤600 µmol/L, 60.7% of participants achieved blood Phe ≤360 µmol/L, below the upper limit recommended in the American College of Medical Genetics and Genomics PKU management guidelines, and 51.2% achieved blood Phe ≤120 µmol/L, below the upper limit of normal in the unaffected population. Improvements in neuropsychiatric outcomes were associated with reductions in blood Phe and were sustained with long-term pegvaliase treatment. Adverse events (AEs) were more frequent in the first 6 months of exposure (early treatment phase) than after 6 months of exposure (late treatment phase); 99% of AEs were mild or moderate in severity and 96% resolved without dose interruption or reduction. The most common AEs were arthralgia (70.5%), injection-site reaction (62.1%), injection-site erythema (47.9%), and headache (47.1%). Acute systemic hypersensitivity events consistent with clinical National Institute of Allergy and Infectious Diseases and the Food Allergy and Anaphylaxis Network anaphylaxis criteria were observed in 12 participants (17 events); of these, 6 participants remained on treatment. Acute systemic hypersensitivity events including potential events of anaphylaxis were not associated with immunoglobulin E, and all events resolved without sequelae. CONCLUSION: Results from the PRISM Phase 3 program support the efficacy of pegvaliase for the treatment of adults with PKU, with a manageable safety profile in most participants. The PRISM-2 extension study will continue to assess the long-term effects of pegvaliase treatment.

Three novel GJB2 (connexin 26) variants associated with autosomal dominant syndromic and nonsyndromic hearing loss.

Connexin 26 (Cx26), encoded by the GJB2 gene, is a key protein involved in the formation of gap junctions in epithelial organs including the inner ear and palmoplantar epidermis. Pathogenic variants in GJB2 are responsible for approximately 50% of inherited sensorineural deafness. The majority of these variants are associated with autosomal recessive inheritance; however, rare reports of dominantly co-segregating variants have been published. Since we began offering GJB2 testing in 2003, only about 2% of detected GJB2 variants from our laboratory have been classified as dominant. Here we report three novel dominant GJB2 variants (p.Thr55Ala, p.Gln57_Pro58delinsHisSer, and p.Trp44Gly); two associated with syndromic sensorineural hearing loss and one with nonsyndromic hearing loss. In the kindred with the p.Thr55Ala variant, the proband and his father present with only leukonychia as a cutaneous finding of their syndromic hearing loss. This phenotype has been previously documented in conjunction with palmoplantar hyperkeratosis, but isolated leukonychia is a novel finding likely associated with the unique threonine to alanine change at codon 55 (other variants at this codon have been reported in cases of nonsyndromic hearing loss). This report contributes to the short list of GJB2 variants associated with autosomal dominant hearing loss, highlights the variability of skin and nail findings associated with such cases, and illustrates the occurrence of both syndromic and nonsyndromic presentations with changes in the same gene.

Maternal phenylketonuria syndrome: studies in mice suggest a potential approach to a continuing problem.

BackgroundUntreated phenylketonuria (PKU), one of the most common human genetic disorders, usually results in mental retardation. Although a protein-restricted artificial diet can prevent retardation, dietary compliance in adults is often poor. In pregnant PKU women, noncompliance can result in maternal PKU syndrome, where high phenylalanine (Phe) levels cause severe fetal complications. Enzyme substitution therapy using Phe ammonia lyase (PAL) corrects PKU in BTBR Phe hydroxylase (Pahenu2) mutant mice, suggesting a potential for maternal PKU syndrome treatment in humans.MethodsWe reviewed clinical data to assess maternal PKU syndrome incidence in pregnant PKU women. We treated female PKU mice (on normal diet) with PAL, stabilizing Phe at physiological levels, and mated them to assess pregnancy outcomes.ResultsPatient records show that, unfortunately, the efficacy of diet to prevent maternal PKU syndrome has not significantly improved since the problem was first noted 40 years ago. PAL treatment of pregnant PKU mice shows that offspring of PAL-treated dams survive to adulthood, in contrast to the complete lethality seen in untreated mice, or limited survival seen in mice on a PKU diet.ConclusionPAL treatment reduced maternal PKU syndrome severity in mice and may have potential for human PKU therapy.

Safety and efficacy of glycerol phenylbutyrate for management of urea cycle disorders in patients aged 2months to 2years.

INTRODUCTION: Glycerol phenylbutyrate (GPB) is approved in the US for the management of patients 2months of age and older with urea cycle disorders (UCDs) that cannot be managed with protein restriction and/or amino acid supplementation alone. Limited data exist on the use of nitrogen conjugation agents in very young patients. METHODS: Seventeen patients (15 previously on other nitrogen scavengers) with all types of UCDs aged 2months to 2years were switched to, or started, GPB. Retrospective data up to 12months pre-switch and prospective data during initiation of therapy were used as baseline measures. The primary efficacy endpoint of the integrated analysis was the successful transition to GPB with controlled ammonia (<100µmol/L and no clinical symptoms). Secondary endpoints included glutamine and levels of other amino acids. Safety endpoints included adverse events, hyperammonemic crises (HACs), and growth and development. RESULTS: 82% and 53% of patients completed 3 and 6months of therapy, respectively (mean 8.85months, range 6days-18.4months). Patients transitioned to GPB maintained excellent control of ammonia and glutamine levels. There were 36 HACs in 11 patients before GPB and 11 in 7 patients while on GPB, with a reduction from 2.98 to 0.88 episodes per year. Adverse events occurring in at least 10% of patients while on GPB were neutropenia, vomiting, diarrhea, pyrexia, hypophagia, cough, nasal congestion, rhinorrhea, rash/papule. CONCLUSION: GPB was safe and effective in UCD patients aged 2months to 2years. GPB use was associated with good short- and long-term control of ammonia and glutamine levels, and the annualized frequency of hyperammonemic crises was lower during the study than before the study. There was no evidence for any previously unknown toxicity of GPB.

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.

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).

Pegvaliase for the treatment of phenylketonuria: Final results of a long-term phase 3 clinical trial program.

Phenylketonuria (PKU) is a genetic disorder caused by deficiency of the enzyme phenylalanine hydroxylase (PAH), which results in phenylalanine (Phe) accumulation in the blood and brain, and requires lifelong treatment to keep blood Phe in a safe range. Pegvaliase is an enzyme-substitution therapy approved for individuals with PKU and uncontrolled blood Phe concentrations (>600 µmol/L) despite prior management. Aggregated results from the PRISM clinical trials demonstrated substantial and sustained reductions in blood Phe with a manageable safety profile, but also noted individual variation in time to and dose needed for a first response. This analysis reports longer-term aggregate findings and characterizes individual participant responses to pegvaliase using final data from the randomized trials PRISM-1 (NCT01819727) and PRISM-2 (NCT01889862), and the open-label extension study 165-304 (NCT03694353). In 261 adult participants with a mean of 36.6 months of pegvaliase treatment, 71.3%, 65.1%, and 59.4% achieved clinically significant blood Phe levels of ≤600, ≤360, and ≤ 120 µmol/L, respectively. Some participants achieved blood Phe reductions with <20 mg/day pegvaliase, although most required higher doses. Based on Kaplan-Meier analysis, median (minimum, maximum) time to first achievement of a blood Phe threshold of ≤600, ≤360, or ≤ 120 µmol/L was 4.4 (0.0, 54.0), 8.0 (0.0, 57.0), and 11.6 (0.0, 66.0) months, respectively. Once achieved, blood Phe levels remained below clinical threshold in most participants. Sustained Phe response (SPR), a new method described within for measuring durability of blood Phe response, was achieved by 85.5%, 84.7%, and 78.1% of blood Phe responders at blood Phe thresholds of ≤600, ≤360, or ≤ 120 µmol/L, respectively. Longer-term safety data were consistent with previous reports, with the most common adverse events (AEs) being arthralgia, injection site reactions, headache, and injection site erythema. The incidence of most AEs, including hypersensitivity AEs, was higher during the early treatment phase (≤6 months) than later during treatment. In conclusion, using data from three key pegvaliase clinical trials, participants treated with pegvaliase were able to reach clinically significant blood Phe reductions to clinical thresholds of ≤600, ≤360, or ≤ 120 µmol/L during early treatment, with safety profiles improving from early to sustained treatment. This study also supports the use of participant-level data and new ways of looking at durable blood Phe responses to better characterize patients' individual PKU treatment journeys.

Efficacy and safety of a synthetic biotic for treatment of phenylketonuria: a phase 2 clinical trial.

Despite available treatment options, many patients with phenylketonuria (PKU) cannot achieve target plasma phenylalanine (Phe) levels1. We previously modified Escherichia coli Nissle 1917 to metabolize Phe in the gut after oral administration (SYNB1618) and designed a second strain (SYNB1934) with enhanced activity of phenylalanine ammonia lyase2,3. In a 14-day open-label dose-escalation study (Synpheny-1, NCT04534842 ), we test a primary endpoint of change from baseline in labeled Phe (D5-Phe AUC0-24; D5-Phe area under the curve (AUC) over 24 hours after D5-Phe administration) in plasma after D5-Phe challenge in adult participants with screening Phe of greater than 600 µM. Secondary endpoints were the change from baseline in fasting plasma Phe and the incidence of treatment-emergent adverse events. A total of 20 participants (ten male and ten female) were enrolled and 15 completed the study treatment. Here, we show that both strains lower Phe levels in participants with PKU: D5-Phe AUC0-24 was reduced by 43% from baseline with SYNB1934 and by 34% from baseline with SYNB1618. SYNB1934 led to a decrease in fasting plasma Phe of 40% (95% CI, -52, -24). There were no serious adverse events or infections. Four participants discontinued because of adverse events, and one withdrew during the baseline period. We show that synthetic biotics can metabolize Phe in the gut, lower post-prandial plasma Phe levels and lower fasting plasma Phe in patients with PKU.

Enhanced interpretation of newborn screening results without analyte cutoff values.

PURPOSE: To improve quality of newborn screening by tandem mass spectrometry with a novel approach made possible by the collaboration of 154 laboratories in 49 countries. METHODS: A database of 767,464 results from 12,721 cases affected with 60 conditions was used to build multivariate pattern recognition software that generates tools integrating multiple clinically significant results into a single score. This score is determined by the overlap between normal and disease ranges, penetration within the disease range, differences between conditions, and weighted correction factors. RESULTS: Ninety tools target either a single condition or the differential diagnosis between multiple conditions. Scores are expressed as the percentile rank among all cases with the same condition and are compared to interpretation guidelines. Retrospective evaluation of past cases suggests that these tools could have avoided at least half of 279 false-positive outcomes caused by carrier status for fatty-acid oxidation disorders and could have prevented 88% of known false-negative events. CONCLUSION: Application of this computational approach to raw data is independent from single analyte cutoff values. In Minnesota, the tools have been a major contributing factor to the sustained achievement of a false-positive rate below 0.1% and a positive predictive value above 60%.

TFAP2A mutations result in branchio-oculo-facial syndrome.

Branchio-oculo-facial syndrome (BOFS) is a rare autosomal-dominant cleft palate-craniofacial disorder with variable expressivity. The major features include cutaneous anomalies (cervical, infra- and/or supra-auricular defects, often with dermal thymus), ocular anomalies, characteristic facial appearance (malformed pinnae, oral clefts), and, less commonly, renal and ectodermal (dental and hair) anomalies. The molecular basis for this disorder is heretofore unknown. We detected a 3.2 Mb deletion by 500K SNP microarray in an affected mother and son with BOFS at chromosome 6p24.3. Candidate genes in this region were selected for sequencing on the basis of their expression patterns and involvement in developmental pathways associated with the clinical findings of BOFS. Four additional BOFS patients were found to have de novo missense mutations in the highly conserved exons 4 and 5 (basic region of the DNA binding domain) of the TFAP2A gene in the candidate deleted region. We conclude BOFS is caused by mutations involving TFAP2A. More patients need to be studied to determine possible genetic heterogeneity and to establish whether there are genotype-phenotype correlations.