RARE DISEASE
Sulfite oxidase deficiency due to molybdenum cofactor deficiency type A
Sulfite oxidase deficiency due to molybdenum cofactor deficiency type A
Sulfite oxidase deficiency due to molybdenum cofactor deficiency type A
Synonyms: Combined deficiency of sulfite oxidase, xanthine dehydrogenase and aldehyde oxidase type A, MOCOD type A
Synonyms: Combined deficiency of sulfite oxidase, xanthine dehydrogenase and aldehyde oxidase type A, MOCOD type A
Synonyms: Combined deficiency of sulfite oxidase, xanthine dehydrogenase and aldehyde oxidase type A, MOCOD type A
Drug discovery
2
drugs
With orphan designations
Overview
Sulfite Oxidase Deficiency Due to Molybdenum Cofactor Deficiency Type A (MoCD-A) is a rare, autosomal recessive neurometabolic disorder caused by MOCS1 mutations, impairing molybdenum cofactor (MoCo) biosynthesis. This disrupts sulfite oxidase activity, leading to toxic sulfite accumulation. Neonates present with intractable seizures, feeding difficulties, and progressive encephalopathy within days of birth. Lens dislocation, spastic quadriplegia, and cystic brain lesions on MRI are common [1][5][8]. Early cPMP (fosdenopterin) replacement can mitigate neurological decline if initiated promptly [1][9].
Key Clinical Insights
Categories: rare developmental anomalies during embryogenesis, rare genetic diseases, rare inborn errors of metabolism, rare neurological diseases, rare ophthalmic disorders
Research Papers
39 drug discovery papers about Sulfite oxidase deficiency due to molybdenum cofactor deficiency type A, with 1 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
39 drug discovery papers about Sulfite oxidase deficiency due to molybdenum cofactor deficiency type A, with 1 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
2026-02-09 | Autism Spectrum Disorder and Long-Term Survival in Attenuated Molybdenum Cofactor Deficiency Type A: A Case Report From Saudi Arabia.
We report the case of an 18-year-old male with genetically confirmed molybdenum cofactor deficiency type A (MoCD-A) due to a homozygous pathogenic MOCS1 variant. He presented in infancy with hypotonia and developmental delay and experienced a generalized tonic seizure at 20 months of age, followed by long-term seizure remission. His clinical course was notable for preserved motor function, below-average cognitive ability, marked speech delay, autism spectrum disorder (ASD), and prominent inattentive symptoms. Metabolic testing demonstrated elevated urinary xanthine, hypoxanthine, and S-sulfocysteine levels, supporting impaired sulfite oxidase activity. Neuroimaging revealed a small, focal hypodensity in the left basal ganglia without progressive changes. This case illustrates an attenuated phenotype of MoCD-A, with survival into adulthood and detailed neuropsychiatric characterization, expanding the recognized clinical spectrum and underscoring the importance of considering metabolic etiologies in patients with overlapping developmental and behavioral features.
2025-09-02 | Brain Magnetic Resonance Imaging of Children With Molybdenum Cofactor Deficiency.
Molybdenum cofactor deficiency (MoCD) is a rare differential diagnosis of neonatal hypoxic ischemic encephalopathy (HIE) with considerable variation in presentation and treatment outcomes. The temporospatial evolution of brain MRI appearances has not been well described. We systematically evaluated 35 MRI brain scans of 13 patients with neonatal MoCD (7 type A, 6 type B) to characterize brain abnormalities arising from exposure to toxicity related to sulfite accumulation and to evaluate changes in response to cPMP treatment in 6 children with MoCD type A. All cases showed evidence of chronic toxicity with developmental disruption. We identified a disease-specific pattern of acute and chronic brain injury, distinct from HIE. White matter edema, as the earliest sign of sulfite-related toxicity, indicates a reversible disease stage. The presence of restricted diffusion in the context of MoCD signifies irreversible brain injury and a poor neurological prognosis, irrespective of subsequent biochemical correction upon cPMP treatment. This is the largest neuroimaging study of children with MoCD and the first longitudinal study to examine MR imaging changes in MoCD type A under cPMP substitution. Neuroimaging can identify diagnostic and prognostic features with relevance for treatment decisions and for the evaluation of the effectiveness of treatment attempts.
2025-05-07 | Metformin restores mitochondrial bioenergetics and redox homeostasis through modulation of mitochondrial biogenesis and dynamics in patient derived cultured fibroblasts and an animal model of molybdenum cofactor deficiency.
Molybdenum cofactor deficiency (MoCD) is an inborn error of sulfur metabolism caused by inactivating variants in the genes encoding enzymes of the molybdenum cofactor biosynthetic pathway. Patients present with accumulation of sulfite in the brain with secondary mitochondrial bioenergetics and severe neurological manifestations. To investigate the pathophysiology of this disorder, we evaluated mitochondrial and redox homeostasis in fibroblasts derived from a patient with MoCD type A (MOCS1 deficiency) and in an animal model based on the intracerebroventricular administration of sulfite in Wistar rats. Since treatment for MoCD is largely ineffective, we also investigated the effects of metformin, an antidiabetic drug with neuroprotective potential. Reduced basal, maximal, and ATP-linked respiration and reserve respiratory capacity were verified in MOCS1 deficient fibroblasts. The protein content of MFN1/2, OPA1, DRP1, and NRF1 was also reduced, whereas p-DRP1 (Ser 637) was increased. Superoxide levels were elevated in these cells. Metformin treatment reversed these changes. Further, the p-AMPK/T-AMPK protein ratio and the expression of PRKAA1, PPARGC1A, SIRT1, DNM1L, and mitofusin 1 were increased by metformin in the deficient cells. Sulfite administration into rat brain disturbed the antioxidant defenses, and tricarboxylic acid cycle and electron transfer chain function in the striatum, cerebral cortex and cerebellum. Metformin prevented this bioenergetic dysfunction. Our findings show that metformin elicits positive effects in the brain of sulfite-treated rats and in the MOCS1 deficient cell line by modulating mitochondrial biogenesis and fission, identifying potential therapeutic intervention opportunities in MoCD.
2025-05-05 | Perioperative Care of a Child With Molybdenum Cofactor Deficiency.
Molybdenum is a trace mineral that is a key component of several enzyme systems. In the human body, molybdenum is complexed with a pterin-based molybdenum cofactor (MOCO), to form the active center of molybdenum-based enzymes. MOCO is synthesized in a four-step process involving six proteins, iron, ATP, and copper. Defects in any of the individual genes involved in this biosynthesis can result in molybdenum cofactor deficiency (MoCD). MoCD is an autosomal recessive disorder with an estimated incidence of 1 in 100,000 - 200,000 live births. Although most patients appear normal at birth, intractable seizures typically develop within hours to days of life, along with feeding difficulties, and subsequent microcephaly, brain atrophy, and severe developmental delay. Mortality is high, with a reported median survival of 2.4 to 3 years. Given the associated end-organ involvement, anesthetic management may be required during radiologic imaging or surgery procedures. We present a 6-year-old child with MoCD type A, who required anesthetic care for a magnetic expansion control (MAGEC) rod insertion with posterior spinal instrumentation under general anesthesia. End-organ involvement of MoCD is presented, previous reports of anesthetic care reviewed, and options for perioperative management discussed.
2025-03-26 | Increased Survival in Patients With Molybdenum Cofactor Deficiency Type A Treated With Cyclic Pyranopterin Monophosphate.
Molybdenum cofactor deficiency (MoCD) Type A is an ultrarare disorder causing neurodegeneration and early death. Cyclic pyranopterin monophosphate (cPMP), a molybdenum cofactor precursor, is a therapeutic option for patients with MoCD Type A. In this study, efficacy in patients with MoCD Type A treated with recombinant cPMP (rcPMP) and/or fosdenopterin, a synthetic form of cPMP, from one retrospective and two prospective open-label studies (N = 14), was compared with a retrospective/prospective natural history study (untreated; N = 37). Safety was evaluated in treated patients. Patients treated with fosdenopterin/rcPMP had significantly reduced risk of premature/early death versus untreated patients (Cox proportional hazards 5.1; 95% CI 1.32-19.36; p = 0.01). MoCD disease biomarkers of urinary S-sulfocysteine and xanthine returned to near-normal from baseline to last visit in treated patients but remained abnormal in untreated patients. At 12 months, in treated patients, 43% could sit unassisted, 44% were ambulatory, and 57% could feed orally. Initiating fosdenopterin/rcPMP treatment ≤ 14 days after birth appeared to result in better clinical outcomes than initiating > 14 days after birth. Most patients (13/14) had a treatment-emergent adverse event; most were unrelated to fosdenopterin/rcPMP, were mild to moderate in severity, and none led to treatment discontinuation. These results demonstrate that patients with MoCD Type A who received fosdenopterin/rcPMP versus untreated patients were more likely to survive. Some treated patients were able to feed orally and achieve developmental milestones including walking. Fosdenopterin/rcPMP was generally well-tolerated. Improved outcomes in patients treated early support the importance of identifying MoCD in neonates and initiating treatment as soon as possible.
2026-02-09 | Autism Spectrum Disorder and Long-Term Survival in Attenuated Molybdenum Cofactor Deficiency Type A: A Case Report From Saudi Arabia.
We report the case of an 18-year-old male with genetically confirmed molybdenum cofactor deficiency type A (MoCD-A) due to a homozygous pathogenic MOCS1 variant. He presented in infancy with hypotonia and developmental delay and experienced a generalized tonic seizure at 20 months of age, followed by long-term seizure remission. His clinical course was notable for preserved motor function, below-average cognitive ability, marked speech delay, autism spectrum disorder (ASD), and prominent inattentive symptoms. Metabolic testing demonstrated elevated urinary xanthine, hypoxanthine, and S-sulfocysteine levels, supporting impaired sulfite oxidase activity. Neuroimaging revealed a small, focal hypodensity in the left basal ganglia without progressive changes. This case illustrates an attenuated phenotype of MoCD-A, with survival into adulthood and detailed neuropsychiatric characterization, expanding the recognized clinical spectrum and underscoring the importance of considering metabolic etiologies in patients with overlapping developmental and behavioral features.
2025-09-02 | Brain Magnetic Resonance Imaging of Children With Molybdenum Cofactor Deficiency.
Molybdenum cofactor deficiency (MoCD) is a rare differential diagnosis of neonatal hypoxic ischemic encephalopathy (HIE) with considerable variation in presentation and treatment outcomes. The temporospatial evolution of brain MRI appearances has not been well described. We systematically evaluated 35 MRI brain scans of 13 patients with neonatal MoCD (7 type A, 6 type B) to characterize brain abnormalities arising from exposure to toxicity related to sulfite accumulation and to evaluate changes in response to cPMP treatment in 6 children with MoCD type A. All cases showed evidence of chronic toxicity with developmental disruption. We identified a disease-specific pattern of acute and chronic brain injury, distinct from HIE. White matter edema, as the earliest sign of sulfite-related toxicity, indicates a reversible disease stage. The presence of restricted diffusion in the context of MoCD signifies irreversible brain injury and a poor neurological prognosis, irrespective of subsequent biochemical correction upon cPMP treatment. This is the largest neuroimaging study of children with MoCD and the first longitudinal study to examine MR imaging changes in MoCD type A under cPMP substitution. Neuroimaging can identify diagnostic and prognostic features with relevance for treatment decisions and for the evaluation of the effectiveness of treatment attempts.
2025-05-07 | Metformin restores mitochondrial bioenergetics and redox homeostasis through modulation of mitochondrial biogenesis and dynamics in patient derived cultured fibroblasts and an animal model of molybdenum cofactor deficiency.
Molybdenum cofactor deficiency (MoCD) is an inborn error of sulfur metabolism caused by inactivating variants in the genes encoding enzymes of the molybdenum cofactor biosynthetic pathway. Patients present with accumulation of sulfite in the brain with secondary mitochondrial bioenergetics and severe neurological manifestations. To investigate the pathophysiology of this disorder, we evaluated mitochondrial and redox homeostasis in fibroblasts derived from a patient with MoCD type A (MOCS1 deficiency) and in an animal model based on the intracerebroventricular administration of sulfite in Wistar rats. Since treatment for MoCD is largely ineffective, we also investigated the effects of metformin, an antidiabetic drug with neuroprotective potential. Reduced basal, maximal, and ATP-linked respiration and reserve respiratory capacity were verified in MOCS1 deficient fibroblasts. The protein content of MFN1/2, OPA1, DRP1, and NRF1 was also reduced, whereas p-DRP1 (Ser 637) was increased. Superoxide levels were elevated in these cells. Metformin treatment reversed these changes. Further, the p-AMPK/T-AMPK protein ratio and the expression of PRKAA1, PPARGC1A, SIRT1, DNM1L, and mitofusin 1 were increased by metformin in the deficient cells. Sulfite administration into rat brain disturbed the antioxidant defenses, and tricarboxylic acid cycle and electron transfer chain function in the striatum, cerebral cortex and cerebellum. Metformin prevented this bioenergetic dysfunction. Our findings show that metformin elicits positive effects in the brain of sulfite-treated rats and in the MOCS1 deficient cell line by modulating mitochondrial biogenesis and fission, identifying potential therapeutic intervention opportunities in MoCD.
2025-05-05 | Perioperative Care of a Child With Molybdenum Cofactor Deficiency.
Molybdenum is a trace mineral that is a key component of several enzyme systems. In the human body, molybdenum is complexed with a pterin-based molybdenum cofactor (MOCO), to form the active center of molybdenum-based enzymes. MOCO is synthesized in a four-step process involving six proteins, iron, ATP, and copper. Defects in any of the individual genes involved in this biosynthesis can result in molybdenum cofactor deficiency (MoCD). MoCD is an autosomal recessive disorder with an estimated incidence of 1 in 100,000 - 200,000 live births. Although most patients appear normal at birth, intractable seizures typically develop within hours to days of life, along with feeding difficulties, and subsequent microcephaly, brain atrophy, and severe developmental delay. Mortality is high, with a reported median survival of 2.4 to 3 years. Given the associated end-organ involvement, anesthetic management may be required during radiologic imaging or surgery procedures. We present a 6-year-old child with MoCD type A, who required anesthetic care for a magnetic expansion control (MAGEC) rod insertion with posterior spinal instrumentation under general anesthesia. End-organ involvement of MoCD is presented, previous reports of anesthetic care reviewed, and options for perioperative management discussed.
2025-03-26 | Increased Survival in Patients With Molybdenum Cofactor Deficiency Type A Treated With Cyclic Pyranopterin Monophosphate.
Molybdenum cofactor deficiency (MoCD) Type A is an ultrarare disorder causing neurodegeneration and early death. Cyclic pyranopterin monophosphate (cPMP), a molybdenum cofactor precursor, is a therapeutic option for patients with MoCD Type A. In this study, efficacy in patients with MoCD Type A treated with recombinant cPMP (rcPMP) and/or fosdenopterin, a synthetic form of cPMP, from one retrospective and two prospective open-label studies (N = 14), was compared with a retrospective/prospective natural history study (untreated; N = 37). Safety was evaluated in treated patients. Patients treated with fosdenopterin/rcPMP had significantly reduced risk of premature/early death versus untreated patients (Cox proportional hazards 5.1; 95% CI 1.32-19.36; p = 0.01). MoCD disease biomarkers of urinary S-sulfocysteine and xanthine returned to near-normal from baseline to last visit in treated patients but remained abnormal in untreated patients. At 12 months, in treated patients, 43% could sit unassisted, 44% were ambulatory, and 57% could feed orally. Initiating fosdenopterin/rcPMP treatment ≤ 14 days after birth appeared to result in better clinical outcomes than initiating > 14 days after birth. Most patients (13/14) had a treatment-emergent adverse event; most were unrelated to fosdenopterin/rcPMP, were mild to moderate in severity, and none led to treatment discontinuation. These results demonstrate that patients with MoCD Type A who received fosdenopterin/rcPMP versus untreated patients were more likely to survive. Some treated patients were able to feed orally and achieve developmental milestones including walking. Fosdenopterin/rcPMP was generally well-tolerated. Improved outcomes in patients treated early support the importance of identifying MoCD in neonates and initiating treatment as soon as possible.
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Drug Discovery Landscape
2 orphan drug designations for Sulfite oxidase deficiency due to molybdenum cofactor deficiency type A, including 2 approved therapies.
2 orphan drug designations for Sulfite oxidase deficiency due to molybdenum cofactor deficiency type A, including 2 approved therapies.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
Cyclic pyranopterin monophosphate [NULIBRY] | small molecules | EMA | 2010-09-20 | 2022-09-16 | TMC Pharma (EU) Limited |
fosdenopterin [Nulibry] | small molecules | FDA | 2009-11-05 | 2021-02-26 | Origin Biosciences, Inc. |
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