Fosdenopterin: First Approval.

Fosdenopterin (NulibryTM) is a synthetic cyclic pyranopterin monophosphate that is being developed by Origin Biosciences (a subsidiary of BridgeBio Pharma) for the treatment of molybdenum cofactor deficiency (MoCD) type A. Fosdenopterin was recently approved by the US FDA for use in reducing the risk of mortality in paediatric and adult patients with MoCD type A. This article summarizes the milestones in the development of fosdenopterin leading to this first approval.

Idiopathic copper toxicosis: is abnormal copper metabolism a primary cause of this disease?

Idiopathic copper toxicosis (ICT) is characterized by marked copper deposition, Mallory-Denk body (MDB) formation and severe hepatic injury. Although the characteristics are apparently different from Wilson disease, large amounts of copper accumulate in the liver of the patients. We extensively treated a patient with ICT to reduce the body copper, however, the patient needed liver transplantation. Previous liver biopsy revealed high copper content. But extirpated liver contained an extremely small amount of copper, although MDBs and severe inflammation remained. These phenomena suggest abnormal copper metabolism is not the principle cause of ICT but some other abnormality must exist.

Extensive pyoderma gangrenosum-like lesions revealing a case of hyperzincemia and hypercalprotectinemia: when to suspect it?

Hyperzincemia and hypercalprotectinemia is a rare inflammatory disease caused by a mutation in the PSTPIP1 gene, with a dysregulation of calprotectin metabolism. Calprotectin is a zinc-binding protein with antimicrobial properties and pro-inflammatory action. The authors report the case of a 20 year-old girl with cutaneous ulcers comparable with pyoderma gangrenosum, growth failure and chronic anemia, who was given the diagnosis of hyperzincemia and hypercalprotectinemia. Measurement of serum zinc and calprotectin concentrations are indicated in these cases.

Extensive pyoderma gangrenosum-like lesions revealing a case of hyperzincemia and hypercalprotectinemia: when to suspect it?

Abstract Hyperzincemia and hypercalprotectinemia is a rare inflammatory disease caused by a mutation in the PSTPIP1 gene, with a dysregulation of calprotectin metabolism. Calprotectin is a zinc-binding protein with antimicrobial properties and pro-inflammatory action. The authors report the case of a 20 year-old girl with cutaneous ulcers comparable with pyoderma gangrenosum, growth failure and chronic anemia, who was given the diagnosis of hyperzincemia and hypercalprotectinemia. Measurement of serum zinc and calprotectin concentrations are indicated in these cases.

Novel founder intronic variant in SLC39A14 in two families causing Manganism and potential treatment strategies.

Congenital disorders of manganese metabolism are rare occurrences in children, and medical management of these disorders is complex and challenging. Homozygous exonic mutations in the manganese transporter SLC39A14 have recently been associated with a pediatric-onset neurodegenerative disorder characterized by brain manganese accumulation and clinical signs of manganese neurotoxicity, including parkinsonism-dystonia. We performed whole exome sequencing on DNA samples from two unrelated female children from the United Arab Emirates with progressive movement disorder and brain mineralization, identified a novel homozygous intronic mutation in SLC39A14 in both children, and demonstrated that the mutation leads to aberrant splicing. Both children had consistently elevated serum manganese levels and were diagnosed with SLC39A14-associated manganism. Over a four-year period, we utilized a multidisciplinary management approach for Patient 1 combining decreased manganese dietary intake and chelation with symptomatic management of dystonia. Our treatment strategy appeared to slow disease progression, but did not lead to a cure or reversal of already established deficits. Clinicians should consider testing for noncoding mutations in the diagnosis of congenital disorders of manganese metabolism and utilizing multidisciplinary approaches in the management of these disorders.

S-sulfocysteine/NMDA receptor-dependent signaling underlies neurodegeneration in molybdenum cofactor deficiency.

Molybdenum cofactor deficiency (MoCD) is an autosomal recessive inborn error of metabolism characterized by neurodegeneration and death in early childhood. The rapid and progressive neurodegeneration in MoCD presents a major clinical challenge and may relate to the poor understanding of the molecular mechanisms involved. Recently, we reported that treating patients with cyclic pyranopterin monophosphate (cPMP) is a successful therapy for a subset of infants with MoCD and prevents irreversible brain damage. Here, we studied S-sulfocysteine (SSC), a structural analog of glutamate that accumulates in the plasma and urine of patients with MoCD, and demonstrated that it acts as an N-methyl D-aspartate receptor (NMDA-R) agonist, leading to calcium influx and downstream cell signaling events and neurotoxicity. SSC treatment activated the protease calpain, and calpain-dependent degradation of the inhibitory synaptic protein gephyrin subsequently exacerbated SSC-mediated excitotoxicity and promoted loss of GABAergic synapses. Pharmacological blockade of NMDA-R, calcium influx, or calpain activity abolished SSC and glutamate neurotoxicity in primary murine neurons. Finally, the NMDA-R antagonist memantine was protective against the manifestation of symptoms in a tungstate-induced MoCD mouse model. These findings demonstrate that SSC drives excitotoxic neurodegeneration in MoCD and introduce NMDA-R antagonists as potential therapeutics for this fatal disease.

Haematological involvement associated with a mild autoinflammatory phenotype, in two patients carrying the E250K mutation of PSTPIP1.

OBJECTIVES: Hyperzincaemia/hypercalprotectinemia (Hz/Hc) syndrome is a recently described condition caused by a specific de novo mutation (E250K) affecting PSTPIP1 gene. It has a phenotype distinct from classical pyogenic arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome that includes severe systemic and cutaneous inflammation, hepatosplenomegaly, arthritis without sequelae, pancytopenia and failure to thrive. METHODS: We describe an 8-year-old boy who presented recurrent right knee swelling mimicking septic arthritis and persistent bone marrow involvement, without cutaneous involvement. RESULTS: Molecular analysis of the PSTPIP1 gene revealed the presence of a heterozygous E250K mutation. No growth failure was detected nor in the patient neither in his mother, carrying the same variant. Blood zinc and calprotectin MRP8/14 concentrations of the patient were found to be markedly increased. Therapy with anakinra was started with rapid disappearance of clinical symptoms and normalization of CRP levels in 24 hours, but persistence of bone marrow involvement. CONCLUSIONS: The patient described has a milder phenotype, with no skin features, minor episodes of arthritis with no sequelae and normal growth. Compared to the patients with de novo mutations described in the literature, familial cases seem to have a milder phenotype. Our case further confirms the lack of efficacy of anakinra on bone marrow involvement.

Efficacy and safety of cyclic pyranopterin monophosphate substitution in severe molybdenum cofactor deficiency type A: a prospective cohort study.

BACKGROUND: Molybdenum cofactor deficiency (MoCD) is characterised by early, rapidly progressive postnatal encephalopathy and intractable seizures, leading to severe disability and early death. Previous treatment attempts have been unsuccessful. After a pioneering single treatment we now report the outcome of the complete first cohort of patients receiving substitution treatment with cyclic pyranopterin monophosphate (cPMP), a biosynthetic precursor of the cofactor. METHODS: In this observational prospective cohort study, newborn babies with clinical and biochemical evidence of MoCD were admitted to a compassionate-use programme at the request of their treating physicians. Intravenous cPMP (80-320 µg/kg per day) was started in neonates diagnosed with MoCD (type A and type B) following a standardised protocol. We prospectively monitored safety and efficacy in all patients exposed to cPMP. FINDINGS: Between June 6, 2008, and Jan 9, 2013, intravenous cPMP was started in 16 neonates diagnosed with MoCD (11 type A and five type B) and continued in eight type A patients for up to 5 years. We observed no drug-related serious adverse events after more than 6000 doses. The disease biomarkers urinary S-sulphocysteine, xanthine, and urate returned to almost normal concentrations in all type A patients within 2 days, and remained normal for up to 5 years on continued cPMP substitution. Eight patients with type A disease rapidly improved under treatment and convulsions were either completely suppressed or substantially reduced. Three patients treated early remain seizure free and show near-normal long-term development. We detected no biochemical or clinical response in patients with type B disease. INTERPRETATION: cPMP substitution is the first effective therapy for patients with MoCD type A and has a favourable safety profile. Restoration of molybdenum cofactor-dependent enzyme activities results in a greatly improved neurodevelopmental outcome when started sufficiently early. The possibility of MoCD type A needs to be urgently explored in every encephalopathic neonate to avoid any delay in appropriate cPMP substitution, and to maximise treatment benefit. FUNDING: German Ministry of Education and Research; Orphatec/Colbourne Pharmaceuticals.

Transient neonatal zinc deficiency due to a new autosomal dominant mutation in gene SLC30A2 (ZnT-2).

Transient neonatal zinc deficiency (TNZD) has a clinical presentation similar to that of acrodermatitis enteropathica but is caused by a low zinc concentration in maternal breast milk. TNZD becomes clinically evident during breastfeeding and is resolved by weaning and the introduction of complementary nutrition. We present a 4-month-old girl with TNZD due to a new autosomal dominant mutation (663delC) in the maternal SLC30A2 gene not previously described in the literature.

D-penicillamine treatment of copper-associated hepatitis in Labrador retrievers.

d-penicillamine is effectively used in the lifelong treatment of copper toxicosis in Bedlington terriers and Wilson's disease in humans. A complex form of copper-associated hepatitis has recently been characterized in the Labrador retriever. The aims of this study were to evaluate the effectiveness of d-penicillamine treatment for copper-associated hepatitis in this breed, to study the effects on hepatic copper, iron and zinc concentrations, and to evaluate parameters to predict optimal duration of treatment. Forty-three client owned Labrador retrievers that were diagnosed with increased hepatic copper were treated with d-penicillamine and underwent at least one follow-up examination including a liver biopsy for histopathological scoring of inflammatory lesions. Hepatic copper, iron and zinc concentrations were determined in the initial and follow-up biopsies by instrumental neutron activation analysis. The influence of initial hepatic copper concentration, sex, age, d-penicillamine formulation and the occurrence of side effects were investigated for their influence on hepatic copper concentration after a certain period of treatment by generalized mixed modelling. d-penicillamine proved to be effective in reducing hepatic copper concentration and associated inflammatory lesions. Parameters derived from the model can be used to estimate the necessary duration of d-penicillamine treatment for Labrador retrievers with increased hepatic copper concentration. Continuous, lifelong d-penicillamine treatment is not recommended in this breed, as there may be a risk for hepatic copper and zinc deficiency.

MEDNIK syndrome: a novel defect of copper metabolism treatable by zinc acetate therapy.

MEDNIK syndrome-acronym for mental retardation, enteropathy, deafness, neuropathy, ichthyosis, keratodermia-is caused by AP1S1 gene mutations, encoding σ1A, the small subunit of the adaptor protein 1 complex, which plays a crucial role in clathrin coat assembly and mediates trafficking between trans-Golgi network, endosomes and the plasma membrane. MEDNIK syndrome was first reported in a few French-Canadian families sharing common ancestors, presenting a complex neurocutaneous phenotype, but its pathogenesis is not completely understood. A Sephardic-Jewish patient, carrying a new AP1S1 homozygous mutation, showed severe perturbations of copper metabolism with hypocupremia, hypoceruloplasminemia and liver copper accumulation, along with intrahepatic cholestasis. Zinc acetate treatment strikingly improved clinical conditions, as well as liver copper and bile-acid overload. We evaluated copper-related metabolites and liver function retrospectively in the original French-Canadian patient series. Intracellular copper metabolism and subcellular localization and function of copper pump ATP7A were investigated in patient fibroblasts. Copper metabolism perturbation and hepatopathy were confirmed in all patients. Studies in mutant fibroblasts showed abnormal copper incorporation and retention, reduced expression of copper-dependent enzymes cytochrome-c-oxidase and Cu/Zn superoxide dismutase, and aberrant intracellular trafficking of Menkes protein ATP7A, which normalized after rescue experiments expressing wild-type AP1S1 gene. We solved the pathogenetic mechanism of MEDNIK syndrome, demonstrating that AP1S1 regulates intracellular copper machinery mediated by copper-pump proteins. This multisystem disease is characterized by a unique picture, combining clinical and biochemical signs of both Menkes and Wilson's diseases, in which liver copper overload is treatable by zinc acetate therapy, and can now be listed as a copper metabolism defect in humans. Our results may also contribute to understand the mechanism(s) of intracellular trafficking of copper pumps.

Transient symptomatic zinc deficiency resembling acrodermatitis enteropathica in a breast-fed premature infant: case report and brief review of the literature.

Transient symptomatic zinc deficiency is a rare disorder clinically indistinguishable from acrodermatitis enteropathica characterized by periorificial and acral dermatitis that usually occurs in exclusively breast-fed infant especially if preterm. We describe a three-month-old breast-fed preterm boy who developed the typical skin lesions. Maternal breast milk zinc was lower than the levels from other 2 mothers of infants at the same gestational age. The disease improved and serum zinc level became normal with oral supplementation of zinc. No recurrence of the dermatosis was observed when the treatment was stopped after weaning.

Pyridoxine-dependent epilepsy with elevated urinary α-amino adipic semialdehyde in molybdenum cofactor deficiency.

α-Amino adipic semialdehyde (α-AASA) accumulates in body fluids from patients with pyridoxine-dependent epilepsy because of mutations in antiquitin (ALDH7A1) and serves as the biomarker for this condition. We have recently found that the urinary excretion of α-AASA was also increased in molybdenum cofactor and sulfite oxidase deficiencies. The seizures in pyridoxine-dependent epilepsy are caused by lowered cerebral levels of pyridoxal-5-phosphate (PLP), the bioactive form of pyridoxine (vitamin B(6)), which can be corrected by the supplementation of pyridoxine. The nonenzymatic trapping of PLP by the cyclic form of α-AASA is causative for the lowered cerebral PLP levels. We describe 2 siblings with clinically evident pyridoxine-responsive seizures associated with increased urinary excretion of α-AASA. Subsequent metabolic investigations revealed several metabolic abnormities, all indicative for molybdenum cofactor deficiency. Molecular investigations indeed revealed a known homozygous mutation in the MOCS2 gene. Based upon the clinically evident pyridoxine-responsive seizures in these 2 siblings, we recommend considering pyridoxine supplementation to patients affected with molybdenum cofactor or sulfite oxidase deficiencies.

Favorable outcome in a newborn with molybdenum cofactor type A deficiency treated with cPMP.

Molybdenum cofactor deficiency (MoCD) is a lethal autosomal recessive inborn error of metabolism with devastating neurologic manifestations. Currently, experimental treatment with cyclic pyranopterin monophosphate (cPMP) is available for patients with MoCD type A caused by a mutation in the MOCS-1 gene. Here we report the first case of an infant, prenatally diagnosed with MoCD type A, whom we started on treatment with cPMP 4 hours after birth. The most reliable method to evaluate neurologic functioning in early infancy is to assess the quality of general movements (GMs) and fidgety movements (FMs). After a brief period of seizures and cramped-synchronized GMs on the first day, our patient showed no further clinical signs of neurologic deterioration. Her quality of GMs was normal by the end of the first week. Rapid improvement of GM quality together with normal FMs at 3 months is highly predictive of normal neurologic outcome. We demonstrated that a daily cPMP dose of even 80 µg/kg in the first 12 days reduced the effects of neurodegenerative damage even when seizures and cramped-synchronized GMs were already present. We strongly recommend starting cPMP treatment as soon as possible after birth in infants diagnosed with MoCD type A.

The HAG mechanism: a molecular rationale for the therapeutic application of iron chelators in human diseases involving the 2-oxoacid utilizing dioxygenases.

'Iron chelation' is widely understood as synonymous with non-specificity and viewed as a purely physicochemical mode of action, without any defined biomolecular target, broadly interfering with metalloenzymes. The 2-oxoacid-utilizing dioxygenases challenge this preconception. A family of non-heme iron enzymes that rely on chelation-dependent catalysis, they employ common molecules like Krebs cycle intermediates as endogenous iron chelators and consume atmospheric oxygen, inserting one of its atoms into cellular components. These enzymes control the adaptation of cells to hypoxia; the reversal of mutagenic DNA alkylations, the initiation of DNA replication, the translation of mRNAs; the production of extracellular matrix proteins like collagens and fibrillins; and numerous metabolic pathways: from the synthesis of the gibberellin growth hormones of plants, and the formation of carnitine, atropine, endotoxins, and cephalosporin antibiotics, to the breakdown of amino acids. Their pivotal roles in human pathology encompass oncogenesis and cancer angiogenesis, scarring and organ fibrosis, inherited diseases, and retroviral infections. Their unique catalysis, termed earlier the 'HAG mechanism' and known in subatomic detail, requires at least three different substrates to form three different products, and proceeds as a ligand reaction at the non-heme iron atom inside the active site pocket, without any direct involvement of apoenzyme residues. The apoenzyme sterically controls ligand access to the metal. The HAG mechanism-based concept of catalytic chelation directed by an apoenzyme, not merely by complexation parameters, has enabled knowledge-guided design of systemic and tissue-selective inhibitors, and of clinical trials. The HAG mechanism also lends itself to the development of novel, man-made biocatalysts.

Iatrogenic copper deficiency associated with long-term copper chelation for treatment of copper storage disease in a Bedlington Terrier.

A 9-year-old Bedlington Terrier was evaluated because of weight loss, inappetence, and hematemesis. Copper storage disease had been diagnosed previously on the basis of high hepatic copper concentration. Treatment had included dietary copper restriction and administration of trientine for chelation of copper. A CBC revealed microcytic hypochromic anemia. High serum activities of liver enzymes, high bile acid concentrations, and low BUN and albumin concentrations were detected. Vomiting resolved temporarily with treatment, but the clinicopathologic abnormalities persisted. Results of transcolonic portal scintigraphy suggested an abnormal shunt fraction. Results of liver biopsy and copper quantification revealed glycogen accumulation and extremely low hepatic copper concentration. Serum and hair copper concentrations were also low. Chelation and dietary copper restriction were tapered and discontinued. Clinical signs and all clinicopathologic abnormalities improved during a period of several months.

Use of 2,3,2-tetramine as a hepatic copper chelating agent for treatment of copper hepatotoxicosis in Bedlington terriers.

Five Bedlington Terriers with inherited copper (Cu) hepatotoxicosis and with hepatic Cu concentrations ranging from 3,000 to 11,000 micrograms/g of dry weight (normal, less than 350 micrograms/g of dry weight) were treated daily for up to 200 days with 2,3,2-tetramine tetrahydrochloride. During treatment, no change was made in the dietary Cu intake, which ranged from 12 to 16 micrograms/g of dry diet. Concentrations of hepatic and serum Cu, iron, and zinc were determined before and at the conclusion of the treatment period. In one dog, 24-hour urinary Cu concentration was measured before and during treatment. A liver biopsy specimen obtained after treatment had significantly (P less than 0.05) reduced hepatic Cu concentration (3,282 micrograms/g of dry weight; a 54.9% reduction), compared with the pretreatment value (7,281 micrograms/g of dry weight). After treatment, there was an overall general lessening of the extent of hepatic morphologic damage. Cytochemical examination for Cu in rhodanine-stained biopsy specimens revealed decreased numbers of Cu-laden hepatic lysosomes. The mean daily urinary Cu concentration increased as much as 25-fold during 2,3,2-tetramine treatment. Hepatic iron and zinc concentrations and serum Cu concentrations remained within normal ranges after treatment. Clinical or laboratory evidence of 2,3,2-tetramine toxicosis was not detected during treatment. These findings indicated that in affected Bedlington Terriers, 2,3,2-tetramine was a safe and rapid chelating agent of hepatic Cu.

Congenital copper deficiency: copper therapy and dopamine-beta-hydroxylase activity in the mottled (brindled) mouse.

The mottled (Mo) mouse is an animal model of the human congenital copper (Cu) deficiency disorder, Menkes' kinky hair syndrome. Intraperitoneal Cu chloride injections have been shown to produce clinical and morphological improvements in this mutant mouse. Cu injections (10 micrograms/g) on postnatal days 7 and 10 are shown to increase endogenous activity of the Cu-dependent enzyme dopamine-beta-hydroxylase in the brains of Mo mice. The present study provides insight into the long-term neurochemical changes resulting from a possible treatment regimen for Menkes' kinky hair syndrome.