Drug Update · Rare Disease

FDA Approves Zycubo for Menkes Disease: Cuts Death Risk 78%

September 07, 2026

Approval date

01/12/2026

Indication

Treatment of Menkes disease in pediatric patients

Primary efficacy

78% reduction in risk of death (HR 0.22; 95% CI 0.10-0.49) in ZYCUBO-ET vs EC-ET

Secondary efficacy

73% reduction in risk of death (HR 0.27; 95% CI 0.12-0.57) in ZYCUBO-LT vs EC-LT

Recommended dosing

1.45 mg subcutaneously twice daily <1 year; 1.45 mg subcutaneously once daily 1 to <17 years

Pooled safety dataset size

129 ZYCUBO-treated patients

Safety bullet count

Clinical Perspective

Pediatricians, medical geneticists, and pediatric neurologists caring for infants and children with Menkes disease should be aware that the FDA has approved an injectable copper replacement product, ZYCUBO, for pediatric patients ^[1]^[2]^[3]^[4]^[5]. The approval is supported by survival comparisons versus contemporaneous external controls showing large reductions in death risk in both early- and late-treated cohorts, and the labeling specifies baseline and serial laboratory monitoring for copper, ceruloplasmin, electrolytes, kidney and liver function, and CBC during treatment ^[2]^[3]. What remains unclear from the provided sources is the long-term functional neurologic outcomes in treated patients beyond survival?

Dr. Lakshmi Venkatesan, MBBS, MD (Paediatrics), DM (Medical Genetics) · Medical Genetics

ZYCUBO (copper histidinate) injection was approved by the FDA on January 12, 2026 for the treatment of Menkes disease in pediatric patients, based on survival analyses from two open-label, single-arm clinical trials comparing treated patients to an untreated contemporaneous external control cohort ^[1]^[2]^[3]^[4]^[5]. In the pooled primary efficacy analysis, early-treated patients had a 78% reduction in the risk of death versus the external control early-treatment cohort (HR 0.22; 95% CI 0.10-0.49) ^[3]^[5].

Clinical Context

ZYCUBO is a copper replacement therapy administered by subcutaneous injection; it delivers bioavailable copper intended to bypass impaired gastrointestinal copper absorption in Menkes disease ^[2]^[3]. The product is developed and marketed by Sentynl Therapeutics, Inc. and was reviewed under NDA 211241, receiving an orphan-designation-related rare pediatric disease priority review voucher at approval ^[1]^[3]. The FDA evaluated two open-label, single-arm clinical trials and supportive expanded-access data, comparing outcomes to contemporaneous external controls for the efficacy assessment ^[3]^[5]. Labeling includes recommended baseline and on-treatment laboratory monitoring because copper accumulation can cause kidney injury, liver dysfunction, and hematological abnormalities ^[2].

Key Findings

In the pooled primary efficacy population, ZYCUBO reduced the risk of death by 78% versus the external control early treatment (EC-ET) cohort (HR 0.22; 95% CI 0.10-0.49) in the ZYCUBO-Early Treatment cohort (ZYCUBO-ET) ^[3]^[5]. Median survival in ZYCUBO-ET was 177.1 months (95% CI 33, NE) versus 17.6 months (95% CI 11.5, 28.6) in EC-ET ^[3].
In the ZYCUBO-Late Treatment cohort (ZYCUBO-LT) compared with the external control late-treatment cohort (EC-LT), ZYCUBO reduced the risk of death by 73% (HR 0.27; 95% CI 0.12-0.57) ^[3]^[5]. Median survival in ZYCUBO-LT was 62.4 months (95% CI 29.6, 80.7) versus 20.7 months (95% CI 12.6, 28.6) in EC-LT ^[3].
The FDA’s approval was supported by evidence from two open-label, single-arm trials (Trial 1 and Trial 2) with survival comparisons to untreated contemporaneous external controls and supplemented by expanded access program data ^[3]^[5].

Safety & Tolerability

Most common adverse reactions (incidence ≥7%) reported in the pooled safety analysis included pneumonia, viral infection, respiratory failure, seizure, bacterial infection, hemorrhage, hypotension, vomiting, tachycardia, pyrexia, volume depletion, fracture, dyspnea, transaminases elevation, diarrhea, fungal infection, anemia, and local administration reaction ^[2].
The pooled safety analysis from two open-label, single-arm trials included 129 ZYCUBO-treated patients with a median exposure duration of 24 months (range: 1 to 39 months) ^[2]. Serious adverse reactions reported in ≥5% of treated pediatric patients included pneumonia, dehydration, seizure, respiratory distress, respiratory syncytial virus infection, cardiopulmonary failure, upper respiratory tract infection, respiratory failure, and vomiting ^[2].
Expanded-access (CYP-001) data showed higher incidences of several serious adverse events compared with the pooled trial safety dataset, including seizure, respiratory distress, pneumonia, dyspnea, respiratory failure, dehydration, infantile spasm, and others; many events were considered consistent with the natural history of Menkes disease ^[3].

Study Design

The efficacy evidence comes from two open-label, single-arm clinical trials (Trial 1, NCT00001262; Trial 2, NCT00811785) in pediatric patients treated for up to three years, with survival compared to an untreated contemporaneous external control cohort collected under a protocol amendment to Trial 2 ^[5]^[6]. The pooled primary efficacy population included patients with severe pathogenic ATP7A variants born after 1999, yielding 83 patients in the pooled efficacy analysis (66 ZYCUBO; 17 external control) ^[5]^[3]. The NDA review also incorporated expanded access program (CYP-001) safety data during review completion ^[3].

FAQ

Q1 What is ZYCUBO approved for?

ZYCUBO (copper histidinate) is approved for the treatment of Menkes disease in pediatric patients. The FDA labeling states that ZYCUBO is a copper replacement product indicated for Menkes disease in pediatric patients and is not indicated for Occipital Horn Syndrome.

Q2 How does ZYCUBO work?

ZYCUBO is described in FDA materials as a bioavailable copper replacement therapy administered by subcutaneous injection to bypass impaired gastrointestinal copper absorption observed in patients with Menkes disease; this approach aims to deliver copper in a form the body can use despite the ATP7A-related absorption defect.

Q3 What is the recommended dose of ZYCUBO?

The recommended pediatric dosing in the prescribing information is: for patients less than 1 year of age, 1.45 mg administered subcutaneously twice daily (8–12 hours between injections); for patients 1 year to less than 17 years of age, 1.45 mg administered subcutaneously once daily. The labeling also specifies baseline and serial laboratory monitoring and subcutaneous reconstitution and administration instructions. Clinicians should consult current prescribing information for complete dosing guidance.

Q4 What are the most common side effects?

The prescribing information lists the most common adverse reactions (incidence ≥7%) observed in the pooled safety analysis as pneumonia, viral infection, respiratory failure, seizure, bacterial infection, hemorrhage, hypotension, vomiting, tachycardia, pyrexia, volume depletion, fracture, dyspnea, transaminases elevation, diarrhea, fungal infection, anemia, and local administration reaction. The label also highlights risks of copper accumulation with potential kidney injury, liver dysfunction, and hematological abnormalities and recommends monitoring during treatment.

FDA Approves Zycubo for Menkes Disease: Cuts Death Risk 78%

Direct Clinical Takeaway & Evidence Summary

FDA Approves Zycubo for Menkes Disease: Cuts Death Risk 78%

Clinical Perspective

Clinical Context

Key Findings

Safety & Tolerability

Study Design

FAQ

References

Cite & Reference This Monograph

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