Fosdenopterin: Treatment for Molybdenum Cofactor Deficiency Type A

Table of Contents

1. The Disease: A Broken Assembly Line
2. How Sulfite Damages the Newborn Brain
3. What the Replacement Molecule Does
4. From a Bacterial Extract to a Synthetic Drug
5. The February 2021 Approval and the Label
6. Warnings, Side Effects and Animal Findings
7. Survival Compared With Natural History
8. Neurological Outcomes and What Is Not Reversed
9. Early Start, and Starting Before the Genotype Is Known
10. Urine S-Sulfocysteine, Xanthine and Uric Acid
11. Types B and C: No Response Reported
12. What Is Not Known
13. Regulatory Documents
14. Key Research Papers
15. Connections
16. Featured Videos

The Disease: A Broken Assembly Line

The body uses molybdenum only after fitting it into a larger helper molecule, the molybdenum cofactor. Four human enzymes depend on that cofactor. The most important in this disease is sulfite oxidase, which clears sulfite. Another, xanthine oxidoreductase, turns xanthine into uric acid.

The cofactor is built in three main steps, and each type of the disease stops the line at a different step, as a 2022 review by Johannes and colleagues describes:

• Type A comes from faults in the gene MOCS1, which blocks the first step, the making of cyclic pyranopterin monophosphate.
• Type B comes from faults in MOCS2 or MOCS3, which block the second step.
• Type C comes from faults in GPHN, which blocks the third step.

All types are recessive: a child inherits a faulty copy of the gene from each parent. Type A is the most common, at 50% or more of cases, and its worldwide incidence is estimated at 1 in 200,000 to 500,000 births, with the authors of a 2025 analysis noting that the exact figure is unknown and the disease is likely underdiagnosed. The types cannot be told apart by the clinical picture in the first weeks of life, so a genetic test is needed to name the type.

The largest natural history study, by Spiegel and colleagues, covered 58 patients (41 with type A, 17 with type B). In 36 of the type A patients, symptoms began in the first 28 days, at a median of 2 days of life. Across all patients the most common first symptoms were seizures (60.3%) and feeding difficulties (53.4%). Later problems included profound developmental delay, low muscle tone in the trunk, stiff limbs that progressed to spastic quadriplegia or diplegia, and a head that stopped growing normally.

A 2025 report from northern Israel shows how severe the classic form can be and how much local genetics matters. All 10 confirmed type A patients there, from consanguineous families carrying founder mutations, presented at 1 to 4 days of life, and all had died by the time of the report. Three died in the first month, five within the first year and two after age 7. Milder forms also exist: Lund and colleagues describe two children with later-onset type A who came to attention through developmental delay.

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How Sulfite Damages the Newborn Brain

Sulfite comes from the normal breakdown of sulfur-containing amino acids in protein. Without working sulfite oxidase it builds up. It is highly reactive and can break the disulfide bridges that hold small molecules and proteins in shape. Its reaction with the amino acid cystine produces S-sulfocysteine, and this has two consequences described in the Johannes review: S-sulfocysteine accumulates, and cystine and cysteine run short.

S-sulfocysteine has the same general shape as glutamate, the brain's main excitatory signal. In 2017, Kumar and colleagues showed in cultured mouse neurons that it switches on the N-methyl-D-aspartate (NMDA) receptor, letting calcium flood in. The calcium activated a protein-cutting enzyme, calpain, which destroyed gephyrin, a protein that holds inhibitory connections together, and the neurons lost those inhibitory connections. Blocking the receptor, the calcium entry or calpain abolished the toxicity in these cultured neurons. In a mouse model of the disease, the receptor blocker memantine protected against the appearance of symptoms. The picture is of a brain being overstimulated while its braking system is taken apart, which fits the seizures seen in affected babies.

Other mechanisms have been shown or proposed. In newborn rat pups, sulfite injected into the brain lowered glutathione, a main antioxidant, and reduced the activity of energy-producing enzymes in the cerebral cortex within 30 minutes (Pramio, 2023). The Johannes review also proposes that low cysteine could drive an iron-dependent form of cell death, ferroptosis, while noting that glutathione levels in patients have not been measured.

On brain scans, the injury can look like the damage from oxygen deprivation at birth, and misdiagnosis as that condition is common. A 2025 study of 35 scans from 13 children found a pattern specific to this disease. White matter swelling was the earliest sign and marked a reversible stage. Restricted diffusion, a scan finding of cells that have already been severely injured, marked irreversible damage and a poor neurological outlook, whatever happened to the biochemistry on treatment (Schwahn, 2025).

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What the Replacement Molecule Does

Cyclic pyranopterin monophosphate is the first stable product on the cofactor assembly line. The cell makes it from guanosine triphosphate using two proteins encoded by MOCS1. Later enzymes turn it into molybdopterin and then, by adding molybdenum, into the finished cofactor.

The U.S. label describes the treatment as substrate replacement. In type A only the first step is blocked, and the later machinery still works. Fosdenopterin supplies the missing product from outside the cell, the later enzymes finish the job, and sulfite oxidase and the other molybdenum enzymes regain activity. The drug does not repair the gene, so the supply has to continue.

This approach is possible because of a chemical property of the pathway. The first intermediate is more stable than the cofactor itself, as Schwarz and colleagues reported in 2004, and has the same structure across all phyla of life. The two later products have much shorter half-lives and are very sensitive to oxygen, which the Johannes review gives as the barrier to using them as drugs.

The label's measurements in healthy adults show a half-life for fosdenopterin of 1.2 to 1.7 hours in the blood. It breaks down mainly without enzymes into an inactive product, Compound Z, and the kidneys account for about 40% of its total clearance. The effect on the enzymes lasts much longer than the drug stays in the blood. Three patients were monitored for 2 to 9 months after treatment was stopped. Clinical and metabolic effects lasted for at least 7 days, and the authors estimated a biological half-life for the enzyme activities of about 3 days (Schwahn, 2024).

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From a Bacterial Extract to a Synthetic Drug

• 2004, mice. Schwarz and colleagues overproduced the molecule, then called precursor Z, in the bacterium Escherichia coli, purified it and injected it into knockout mice lacking the gene. The treated mice, which otherwise resemble the human disease, reached adulthood and could reproduce.
• 2010, first reported patient. Veldman and colleagues described a baby diagnosed at 6 days of age who began daily intravenous treatment with the purified bacterial form on day 36, at 80 to 160 micrograms per kilogram. Within 1 to 2 weeks the urine markers were almost normal and convulsions and twitching had disappeared, and the markers held for more than 450 days of treatment.
• 2012, treatment from the first hours. Hitzert and colleagues reported a girl diagnosed before birth who started treatment 4 hours after birth. After brief seizures on the first day, she showed no further signs of neurological deterioration, and the quality of her movements was normal by the end of the first week.
• 2013, chemical synthesis. Clinch and colleagues published a way to make the molecule without bacteria. In laboratory tests it performed comparably to the bacterial version, and the authors noted that the method could be scaled up. The Johannes review credits this with larger quantities and cheaper production.
• 2014 onward, the switch. After a phase 1 safety study of the synthetic form, children on the bacterial form were moved to it step by step within a phase 2/3 study.
• 2015, first cohort. Schwahn and colleagues reported 16 newborns treated between June 2008 and January 2013 in a compassionate-use program, at 80 to 320 micrograms per kilogram per day. They observed no drug-related serious adverse events after more than 6,000 doses.
• 2021, approval of the synthetic form.

The bacterial and synthetic forms have the same molecular structure, and the U.S. label and the pooled analyses combine data from both. The bacterial form is called "recombinant" in those documents.

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The February 2021 Approval and the Label

The U.S. approval record lists fosdenopterin as a new molecular entity, reviewed with priority and approved on February 26, 2021; a 2021 summary by Kang covers the development milestones. The label's indication is to reduce the risk of mortality in patients with molybdenum cofactor deficiency type A. The other regulators reported in the 2025 analysis are the European Medicines Agency (September 2022), the Israeli Ministry of Health (July 2022) and the United Kingdom's medicines regulator (April 2024). The European authorization was granted under "exceptional circumstances," which its product information explains as a recognition that the rarity of the disease made it impossible to obtain complete information, with new information reviewed every year. The National Institute for Health and Care Excellence in England lists its appraisal of the drug as terminated (June 2025).

The label directs that the drug be started when a patient has a diagnosis or presumptive diagnosis of type A, that the diagnosis be confirmed immediately afterward, and that the drug be discontinued if genetic testing does not confirm type A.

The dose schedule in the label

Doses are based on actual body weight and are given once daily by intravenous infusion:

• Preterm newborns (under 37 weeks of gestation): 0.4 mg/kg initially, 0.7 mg/kg at months 1 and 2, then 0.9 mg/kg from month 3 to month 12.
• Term newborns (37 weeks and above): 0.55 mg/kg initially, 0.75 mg/kg at months 1 and 2, then 0.9 mg/kg from month 3 to month 12.
• Patients one year of age or older: 0.9 mg/kg.

The label gives an infusion rate of 1.5 mL per minute through non-DEHP tubing with a 0.2 micron filter, and for volumes under 2 mL it describes a slow push over 1 to 2 minutes. The drug is stored frozen, dissolved in sterile water and used within 4 hours, and it is not mixed with other drugs. If a dose is missed, the label says to give it as soon as possible, with the next scheduled dose at least 6 hours later. The label states that a healthcare provider gives the drug or, where a provider judges it appropriate, a caregiver at home; the home and preparation sections were revised in May 2026.

A daily infusion without a stopping point

The label sets no end date for treatment. The European product information calls it "a chronic substrate replacement therapy intended for long-term use." Neither document uses the word "lifelong," but because the gene defect remains, the treatment is in practice daily infusion for life, and the longest reported exposure so far is 12.4 years. In the pooled studies, daily dosing required long-term central venous catheters, and these drive much of the side-effect burden described below.

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Warnings, Side Effects and Animal Findings

The label read for this page (revised May 2026) has no boxed warning and lists no contraindications. Its one warning and precaution is the potential for photosensitivity.

Photosensitivity

This warning comes from animals. In pigmented rats, three days of intravenous fosdenopterin at 4.5 or more times the maximum human dose, followed by ultraviolet radiation, caused dose-dependent skin reactions (redness, swelling, flaking and eschar) along with eye and tissue changes that indicate phototoxicity. The label tells prescribers to advise patients or caregivers to avoid or minimize exposure to direct sunlight and artificial ultraviolet light, including phototherapy, and to use protective clothing, hats, sunglasses and, from 6 months of age, broad-spectrum high-factor sunscreen. It lists redness, a burning sensation of the skin and blisters as reaction symptoms that call for immediate medical attention. The 2025 analysis reports no phototoxicity events in the clinical studies.

Side effects in patients

The label's adverse-reaction table comes from nine treated patients with a median exposure of 4.3 years:

• Catheter-related complications: 8 of 9 (89%)
• Fever: 7 of 9 (78%)
• Viral infection: 5 of 9 (56%)
• Pneumonia, middle ear infection, vomiting and cough or sneezing: 4 of 9 each (44%)
• Viral upper respiratory infection, gastroenteritis, diarrhea and bloodstream infection: 3 of 9 each (33%)

With so few patients and no comparison group, these figures cannot separate the drug from the catheter, the underlying disease or ordinary childhood infections. In the 2025 analysis, most adverse events were judged unrelated to treatment and none led to stopping the drug. Two children with type A treated with the bacterial form died: one of respiratory syncytial virus pneumonia, judged unrelated, and one of necrotizing enterocolitis, judged possibly related by the investigator.

Other animal and laboratory findings in the label

• Development: no adverse effects in pregnant rabbits at about 89 times human exposure, or in pregnant and nursing mice at up to 32 times human exposure.
• Fertility: no effect in mice at about 18 times the maximum human dose.
• Genetic damage: not genotoxic in standard tests.
• Cancer: carcinogenicity studies have not been conducted.

The label reports no available human data on use in pregnancy or on transfer into breast milk. The effect of kidney or liver impairment on the drug is unknown. At the maximum approved dose it did not prolong the QT interval, a heart-rhythm measure, to a clinically relevant extent.

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Survival Compared With Natural History

No randomized trial exists. The evidence compares treated children with the historical record of untreated children. The authors of the 2025 analysis write that randomized placebo-controlled trials are impractical and potentially unethical in ultrarare, deadly diseases, which often makes historical controls necessary.

The untreated course

In the natural history study, one-year survival in type A with onset in the first 28 days was 71.8%, and the median age at death was 2.4 years.

The U.S. label's analysis

The label compares 13 treated patients with 18 untreated patients matched by genotype:

• Deaths: 2 of 13 (15%) treated, 12 of 18 (67%) untreated.
• Survival at 1 year: 92% treated (95% confidence interval 57% to 99%), 67% untreated (40% to 83%).
• Survival at 3 years: 84% treated (49% to 96%), 55% untreated (30% to 74%).
• Hazard ratio for death: 0.18 (95% confidence interval 0.04 to 0.72), which means a lower risk of death in treated patients.
• Mean survival time up to 3 years: 32 months treated, 24 months untreated, a difference of 8 months with an interval of -1 to 16 months that includes zero. Up to 1 year the means were 11 and 10 months, a difference of 1 month with an interval of -1 to 4 months.

The 2025 pooled analysis

Schwarz and colleagues compared 14 treated patients with 37 untreated patients, at a data cutoff of October 31, 2020. The risk of death was 5.1 times higher in untreated patients (95% confidence interval 1.32 to 19.36). Median overall survival was not reached in the treated group and was 50.7 months in the untreated group. Nine of the 14 treated patients were still on treatment at cutoff.

Limits of these numbers

• The wide intervals reflect the small numbers. One or two deaths would shift the percentages substantially.
• The authors list the lack of randomization and blinding, different assessment timing, and unknown confounders as limitations.
• The groups were not alike. Treated patients all had severe newborn onset, while the untreated group included some with later onset and milder disease, with onset ranging up to 927 days. The authors note that this would make the untreated group look better. Treated patients were also diagnosed far earlier (median 3 days versus 269 days).
• Survival status was confirmed for 38 of the 51 patients at cutoff.
• The natural history and pooled studies were written with authors who worked for, advised or were paid by the drug's developers, as their disclosures state.

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Neurological Outcomes and What Is Not Reversed

The label's indication concerns survival. Neurological function is the harder question, because a child can survive with severe disability. The 2025 full paper gives these results:

• Oral feeding at last assessment: 8 of 14 treated (57%), 10 of 33 untreated (30%).
• Walking independently at last assessment: 4 of 9 treated (44%), 1 of 11 untreated (9%). In the untreated group 9 of 11 needed a wheelchair.
• Sitting unassisted at 12 months: 3 of 7 treated (43%), 3 of 27 untreated (11%).
• Abnormal muscle tone in the trunk at last assessment: 7 of 14 treated (50%), 33 of 37 untreated (89%).

The paper's abstract places all of the first three figures "at 12 months," but its results section ties the feeding and walking figures to the last assessment, which is the version given here.

Several findings set the limits of the treatment:

• Seizures. In the prospective data, seizures were absent or resolved in 5 of 10 treated and 1 of 14 untreated children, and still present in 4 of 10 and 5 of 14. The authors report no statistically significant difference between groups on this measure.
• Brain scans. Most patients in both groups had abnormal scans, and most who completed the assessments showed no change. One treated patient improved.
• Two groups of survivors. Among eight patients who moved from the bacterial to the synthetic form, four had static encephalopathy: they could not walk, had small heads, had seizure disorders and, in three of the four, could not feed by mouth. The other four walked, fed by mouth, had never had seizures and kept developing.
• Injury before treatment. The Johannes review states that the clinical outcome critically depends on how much brain injury occurred before treatment started. Restricted diffusion on a scan signified irreversible injury regardless of later biochemical correction (Schwahn, 2025).

Case reports show what even the earliest treatment has and has not achieved so far:

• Schwahn and colleagues (2024) describe a child diagnosed by an incidental finding of very low cystine after presenting with low blood sugar at 10 hours of age, and treated before severe encephalopathy set in. The authors call this the first and, at the time, only index patient treated early enough to avoid severe brain injury. Motor development was normal, but at age 7 the child had significant communication difficulties and a mild to moderate learning disability, despite complete and sustained correction of the biochemistry.
• A boy treated within 2 hours after prenatal diagnosis had, at age 4, a cognitive age equivalent of 20 months, walked independently and was seizure-free (Schwarz, 2025).
• Etchegaray and colleagues (2025) describe a baby diagnosed at 16 weeks of pregnancy, delivered at 32 weeks and 6 days, and given fosdenopterin within 10 minutes of birth. Seizures began at about 12 hours, escalated to status epilepticus by 24 hours and resolved by 60 hours. The child was diagnosed with spastic quadriplegic cerebral palsy at 6 months, with cognition relatively spared, and at 24 months was seizure-free with moderate motor impairment.

These cases point to damage starting before birth. A meta-analysis of 30 published cases found that prenatal origin of brain damage was possible in all 21 classic cases and certain in 11 of them (52%), and it concluded that this is more frequent than anticipated (Ferreira, 2024). Treatment that starts at birth cannot address that part of the injury. The Etchegaray authors conclude that prenatal interventions are needed to improve outcomes further; no such treatment has been established.

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Early Start, and Starting Before the Genotype Is Known

The clearest timing data come from a prespecified but very small subgroup of the pooled analysis:

• Started within 14 days of birth (11 patients): 7 of 11 fed by mouth, 4 of 7 walked, 6 of 7 sat unassisted.
• Started after 14 days (3 patients, at days 32, 37 and 69): none fed by mouth (0 of 3), walked (0 of 2) or sat unassisted (0 of 2).

There was no apparent difference in overall survival between the two subgroups. Untreated patients appeared to do better than the late-start group, which the authors say may partly reflect later-onset, milder disease among the untreated. The 2015 cohort reached a similar conclusion: three patients treated early remained seizure-free with near-normal development.

Treating on suspicion

The label allows a start on a presumptive diagnosis, and the reason is the clock. Genetic results can take longer than the brain injury does. In the pooled data, six patients treated for suspected type A turned out not to have it (four had type B, one an unknown type and one an unknown diagnosis). They received treatment for 3 to 17 days. Two had adverse events, which were non-serious apart from one case of severe cardiac failure. The 2025 authors present this as evidence that treatment before genetic confirmation is viable, and they state that early empirical treatment of encephalopathic infants with a potential diagnosis of type A is worth considering. The 2015 authors wrote that type A needs urgent exploration in every encephalopathic newborn.

The diagnostic gap

The barrier is recognition. The disease is not on the U.S. Recommended Uniform Screening Panel or in newborn screening programs, according to the 2025 paper, and the 2024 consensus guidelines describe common diagnostic delays caused by a nonspecific picture and a lack of easily available tests. Two case reports show how narrow the window can be:

• Rapid whole-genome sequencing gave a provisional diagnosis on day 4 of life. Emergency access to the drug was weighed and judged unsuitable given the severity of disease and the delay, and the baby died on day 9 (Kingsmore, 2020).
• A laboratory protocol that reported results within 48 hours identified the biochemical pattern, but the baby died before the preliminary diagnosis could be shared (Crenshaw, 2026).

Prenatal diagnosis gives the longest lead time, as in the Etchegaray family, who had an earlier affected child. Six of the 14 treated patients in the pooled analysis were diagnosed before birth. Veldman and colleagues also showed in 2010 that the disease could be detected from newborn-screening cards, though this has not become routine. Blood and urine clues reported in the literature include very low cystine and low uric acid.

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Urine S-Sulfocysteine, Xanthine and Uric Acid

These three urine measurements follow the two main failed enzymes. S-sulfocysteine reflects sulfite oxidase failure and runs high. Xanthine builds up when xanthine oxidoreductase fails, and uric acid, its product, falls low or becomes undetectable. Elevated hypoxanthine, thiosulfate and sulfite and low blood cystine belong to the same pattern.

The 2025 analysis reports mean urine values, in micromoles per millimole of creatinine, at baseline and last visit:

• S-sulfocysteine, reference 0 to 18: treated 164.2 to 9.2; untreated 136.3 to 156.6.
• Xanthine, reference 0 to 63.4: treated 246.2 to 19.6; untreated 315.8 to 338.2.
• Uric acid, reference 820 to 1,026: treated 444.3 to 500.6; untreated 99.1 to 45.0.

The paper describes reductions of 94% in S-sulfocysteine and 92% in xanthine, maintained over 30 to 48 months. It describes uric acid levels as normal in treated patients, although the printed mean of 500.6 sits below its printed reference range. It also notes that uric acid in the first days of life partly comes from the mother across the placenta, which makes baseline values misleading.

The speed is striking. The 2015 cohort saw all three markers return to almost normal within 2 days in all type A patients, and they stayed there for up to 5 years. The U.S. label reports S-sulfocysteine means of 11 down to 7 from month 3 to month 48 in nine patients, against a baseline of 89.8 in the one patient measured before any treatment.

Correct biochemistry does not guarantee a healthy brain. The child described by Schwahn in 2024 developed a learning disability despite sustained normal values, and a scan finding of restricted diffusion carried a poor outlook regardless of correction.

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Types B and C: No Response Reported

The drug acts at the first step of the assembly line, so it can only help when that first step is the one that is broken. The 2015 cohort included five babies with type B, and the authors detected no biochemical or clinical response in them. That cohort had no type C patients. The statement about type C rests on the position of the block in the pathway: the Johannes review states that the substitution is not applicable to types B and C, because their defects come after this step. The same review reports no specific treatment for types B and C or for isolated sulfite oxidase deficiency, a related disease in which the enzyme itself is missing.

Other approaches for these types remain experimental. In one baby with type B, six hepatocyte (liver cell) transfusions between day 1 and day 18, combined with a protein-restricted diet, stabilized some biochemistry but did not prevent acute brain injury, which was visible on imaging at 35 hours (Selvanathan, 2025). Not every case in these types is severe: five Roma patients carrying a particular MOCS2 variant had only mild or no symptoms, with low uric acid as a key clue (Cho, 2025).

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What Is Not Known

• The true size of the benefit. The consensus guidelines themselves state that the evidence base for the rational use of the treatment is very limited, and no randomized comparison exists.
• Long-term neurological outcome. The oldest treated children are still young, and the reported function in the early-treated group comes from a handful of patients. Later-onset disease has been reported only in small numbers.
• Adults. The U.S. label bases adult use on the pediatric studies, and the European product information notes limited data in adolescents and adults.
• The best dosing interval. The three-patient withdrawal study suggests that less-than-daily dosing could be a safe alternative, but this has not been tested in a trial and is not part of the label.
• Prenatal treatment. Injury can begin before birth, and whether it can be prevented is unanswered.
• Combined approaches. A blocker of the N-methyl-D-aspartate receptor protected mice in the 2017 study, but in humans such blockers have been studied only sporadically, with one mild case improving on dextromethorphan and no clear benefit in another, according to the Johannes review.
• Photosensitivity in people. The warning rests on animal data, and clinical studies have reported no cases so far.
• Cancer risk, kidney and liver effects, and pregnancy. The label reports no carcinogenicity studies and no human data on these questions.

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Regulatory Documents

1. U.S. National Library of Medicine, DailyMed. Fosdenopterin for injection: prescribing information, revised May 2026 (read through the openFDA label record, November 2026). DailyMed label
2. U.S. Food and Drug Administration, Drugs@FDA. New Drug Application 214018: original approval February 26, 2021, priority review, new molecular entity. Drugs@FDA record
3. European Medicines Agency. Fosdenopterin: summary of product characteristics and package leaflet. European product information (PDF)
4. National Institute for Health and Care Excellence. Fosdenopterin for treating molybdenum cofactor deficiency type A (terminated appraisal). London; 2025 Jun 25. PubMed PMID: 40763239

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Key Research Papers

1. Schwahn BC, Van Spronsen FJ, Belaidi AA, Bowhay S, Christodoulou J, Derks TG, Hennermann JB, Jameson E, König K, McGregor TL, Font-Montgomery E, Santamaria-Araujo JA, Santra S, Vaidya M, Vierzig A, Wassmer E, Weis I, Wong FY, Veldman A, Schwarz G. Efficacy and safety of cyclic pyranopterin monophosphate substitution in severe molybdenum cofactor deficiency type A: a prospective cohort study. Lancet. 2015;386(10007):1955-1963. PubMed PMID: 26343839
2. Schwarz G, Basel DG, Schwahn BC, Spiegel R, Wong FY, Bliss R, Squires L. Increased Survival in Patients With Molybdenum Cofactor Deficiency Type A Treated With Cyclic Pyranopterin Monophosphate. Journal of Inherited Metabolic Disease. 2025;48(2):e70000. PubMed PMID: 40132614
3. Spiegel R, Schwahn BC, Squires L, Confer N. Molybdenum cofactor deficiency: A natural history. Journal of Inherited Metabolic Disease. 2022;45(3):456-469. PubMed PMID: 35192225
4. Schwahn BC, van Spronsen F, Misko A, Pavaine J, Holmes V, Spiegel R, Schwarz G, Wong F, Horman A, Pitt J, Sass JO, Lubout C. Consensus guidelines for the diagnosis and management of isolated sulfite oxidase deficiency and molybdenum cofactor deficiencies. Journal of Inherited Metabolic Disease. 2024;47(4):598-623. PubMed PMID: 38627985
5. Johannes L, Fu CY, Schwarz G. Molybdenum Cofactor Deficiency in Humans. Molecules. 2022;27(20):6896. PubMed PMID: 36296488
6. Kumar A, Dejanovic B, Hetsch F, Semtner M, Fusca D, Arjune S, Santamaria-Araujo JA, Winkelmann A, Ayton S, Bush AI, Kloppenburg P, Meier JC, Schwarz G, Belaidi AA. S-sulfocysteine/NMDA receptor-dependent signaling underlies neurodegeneration in molybdenum cofactor deficiency. Journal of Clinical Investigation. 2017;127(12):4365-4378. PubMed PMID: 29106383
7. Pramio J, Grings M, da Rosa AG, Ribeiro RT, Glanzel NM, Signori MF, Marcuzzo MB, Bobermin LD, Wyse ATS, Quincozes-Santos A, Wajner M, Leipnitz G. Sulfite Impairs Bioenergetics and Redox Status in Neonatal Rat Brain: Insights into the Early Neuropathophysiology of Isolated Sulfite Oxidase and Molybdenum Cofactor Deficiencies. Cellular and Molecular Neurobiology. 2023;43(6):2895-2907. PubMed PMID: 36862242
8. Schwarz G, Santamaria-Araujo JA, Wolf S, Lee HJ, Adham IM, Gröne HJ, Schwegler H, Sass JO, Otte T, Hänzelmann P, Mendel RR, Engel W, Reiss J. Rescue of lethal molybdenum cofactor deficiency by a biosynthetic precursor from Escherichia coli. Human Molecular Genetics. 2004;13(12):1249-55. PubMed PMID: 15115759
9. Veldman A, Santamaria-Araujo JA, Sollazzo S, Pitt J, Gianello R, Yaplito-Lee J, Wong F, Ramsden CA, Reiss J, Cook I, Fairweather J, Schwarz G. Successful treatment of molybdenum cofactor deficiency type A with cPMP. Pediatrics. 2010;125(5):e1249-54. PubMed PMID: 20385644
10. Hitzert MM, Bos AF, Bergman KA, Veldman A, Schwarz G, Santamaria-Araujo JA, Heiner-Fokkema R, Sival DA, Lunsing RJ, Arjune S, Kosterink JG, van Spronsen FJ. Favorable outcome in a newborn with molybdenum cofactor type A deficiency treated with cPMP. Pediatrics. 2012;130(4):e1005-10. PubMed PMID: 22987873
11. Clinch K, Watt DK, Dixon RA, Baars SM, Gainsford GJ, Tiwari A, Schwarz G, Saotome Y, Storek M, Belaidi AA, Santamaria-Araujo JA. Synthesis of cyclic pyranopterin monophosphate, a biosynthetic intermediate in the molybdenum cofactor pathway. Journal of Medicinal Chemistry. 2013;56(4):1730-8. PubMed PMID: 23384403
12. Kang C. Fosdenopterin: First Approval. Drugs. 2021;81(8):953-956. PubMed PMID: 33909276
13. Schwahn BC, Hart C, Smith LA, Hart A, Fairbanks L, Arenas-Hernandez M, Turner C, Horman A, Rust S, Santamaria-Araujo JA, Mayr SJ, Schwarz G, Sharrard M. cPMP rescue of a neonate with severe molybdenum cofactor deficiency after serendipitous early diagnosis, and characterisation of a novel MOCS1 variant. Molecular Genetics and Metabolism. 2024;143(4):108598. PubMed PMID: 39488078
14. Schwahn BC, Barvíková K, Wu HT, Horman A, Emmett E, Kožich V. Pharmacodynamic profiling in three patients with molybdenum cofactor deficiency type A reveals prolonged biological effects after withdrawal of cyclic pyranopterin monophosphate. Molecular Genetics and Metabolism. 2024;143(1-2):108563. PubMed PMID: 39168057
15. Schwahn BC, Sinha R, Wright JAM, Pavaine J. Brain Magnetic Resonance Imaging of Children With Molybdenum Cofactor Deficiency. Journal of Inherited Metabolic Disease. 2025;48(5):e70079. PubMed PMID: 40887454
16. Ferreira EA, Hofstede FC, Haijes-Siepel HA, Lichtenbelt KD, Pistorius L, de Sain-van der Velden MGM, Nikkels PGJ, Lequin MH, de Vries LS, van der Crabben SN, van Hasselt PM. Timing of cerebral damage in molybdenum cofactor deficiency: A meta-analysis of case reports. Genetics in Medicine Open. 2024;2:101853. PubMed PMID: 39669634
17. Etchegaray A, Haffner D, Cruz SM, Ogunleye O, Xia J, Schlegel A, Olutoye OO, Chaudhari BP. Early Neonatal Fosdenopterin Treatment for Molybdenum Cofactor Deficiency Type A: New Insights into Its Natural History and Potential Role for Fetal Therapy. Journal of Clinical Medicine. 2025;14(10):3561. PubMed PMID: 40429556
18. Crenshaw MM, Midgette Y, Mohan S, Wei R, Anneling M, Williams M, Patel M, Cocanougher BT, Young SP, Niyazov D, El-Gharbawy A, Stiles AR. Treatable Neonatal Molybdenum Cofactor Deficiency: Rapid Demise Despite Rapid Biochemical Diagnosis. JIMD Reports. 2026;67(1):e70061. PubMed PMID: 41531943
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PubMed Topic Searches

1. PubMed: fosdenopterin
2. PubMed: cyclic pyranopterin monophosphate and molybdenum cofactor deficiency
3. PubMed: molybdenum cofactor deficiency natural history
4. PubMed: S-sulfocysteine neurotoxicity

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Connections

• Drugs — every drug page on the site
• Molybdenum Deficiency — why this disease is genetic, not dietary
• Molybdenum — the mineral at the center of the cofactor
• Molybdenum for Sulfite Metabolism — the enzyme this disease disables
• Molybdenum for Detoxification — the cofactor-dependent enzymes together
• Molybdenum for Uric Acid — the xanthine and uric acid pathway
• Sulfur Deficiency — the sulfite intoxication disorders in context
• Cerebral Palsy — the diagnosis given to some children with this injury
• Phenylketonuria — another inborn error where early detection shapes the outcome

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