Anti-CD33 antibody-drug conjugate Pregnancy: Can cause embryo-fetal harm when administered to a pregnant woman, based on its mechanism of action and animal findings (embryo-fetal toxicity including structural abnormalities and altered growth). There are no available data in pregnant women. Advise pregnant women of the potential risk to a fetus.

Gemtuzumab ozogamicin (Specialist drug)

Brand names: Mylotarg

Gemtuzumab ozogamicin is an intravenous antibody-drug conjugate used by haemato-oncology specialists to treat CD33-positive acute myeloid leukaemia.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 3 mg/m2 (up to one 4.5 mg vial) per dose

Route: Intravenous infusion

Frequency: Newly-diagnosed de novo CD33-positive AML, combination regimen: induction cycle on Days 1, 4 and 7 in combination with daunorubicin and cytarabine; consolidation cycles on Day 1 (2 consolidation cycles). Do NOT administer gemtuzumab ozogamicin during a second induction cycle if one is required.

Max: Each dose is capped at one 4.5 mg vial in the combination regimen and in the relapsed/refractory single-agent regimen; the newly-diagnosed single-agent regimen (6 mg/m2, 3 mg/m2, 2 mg/m2) is NOT limited to one 4.5 mg vial

OTHER ADULT REGIMENS. Newly-diagnosed CD33-positive AML, SINGLE AGENT: induction 6 mg/m2 on Day 1 and 3 mg/m2 on Day 8 (not limited to one 4.5 mg vial); continuation, for patients without evidence of disease progression after induction, up to 8 courses of 2 mg/m2 on Day 1 every 4 weeks (not limited to one 4.5 mg vial). RELAPSED OR REFRACTORY CD33-positive AML, single agent (adults and paediatric patients 2 years and older): 3 mg/m2 (up to one 4.5 mg vial) on Days 1, 4 and 7 — treatment consists of a single course. PREMEDICATION (adults): paracetamol (acetaminophen) 650 mg orally and diphenhydramine 50 mg orally or intravenously 1 hour before dosing, plus methylprednisolone 1 mg/kg (or an equivalent dose of an alternative corticosteroid) within 30 minutes before the infusion; repeat the same corticosteroid dose for any sign of an infusion reaction (fever, chills, hypotension, dyspnoea) during the infusion or within 4 hours afterwards. Use appropriate measures to prevent tumour lysis syndrome. For hyperleukocytosis (leucocyte count 30 Gi/L or greater), cytoreduction is recommended before administration. MONITORING: monitor blood counts frequently through resolution of cytopenias, and blood counts and chemistries at least three times per week through recovery from treatment-related toxicities; dose interruption or permanent discontinuation may be required. Persistent thrombocytopenia in combination therapy: in adults, if the platelet count does not recover to 100 Gi/L or greater within 14 days of the planned start of the consolidation cycle, discontinue. SOURCE LIMITATION: no UK SPC (eMC) was fetched in this bundle — this draft is distilled from the US MYLOTARG prescribing information and must be verified against the UK SPC before use.

Paediatric dose

Dose: 0.1 mg/kg

Route: Intravenous infusion

Frequency: Newly-diagnosed de novo CD33-positive AML, combination regimen, patients 1 month and older: given once in Induction 1 in combination with standard chemotherapy, and once in Intensification 2. No gemtuzumab ozogamicin is given in the second induction cycle or in the first or third intensification cycles.

Max: The 0.1 mg/kg dose applies only to patients with body surface area LESS THAN 0.6 m2; patients 1 month and older with a BSA of 0.6 m2 or greater receive 3 mg/m2 instead

US labelling (MYLOTARG) — no UK SPC was available in this bundle. Paediatric premedication: paracetamol (acetaminophen) 15 mg/kg (maximum 650 mg) and diphenhydramine 1 mg/kg (maximum 50 mg) 1 hour before dosing, plus methylprednisolone 1 mg/kg orally or intravenously within 30 minutes before the infusion; additional doses of paracetamol and diphenhydramine may be given every 4 hours after the initial pretreatment dose. Safety and effectiveness in patients under 1 month of age with newly-diagnosed de novo AML have not been established, nor as a single agent in paediatric patients with newly-diagnosed AML. Relapsed or refractory CD33-positive AML in patients 2 years and older is dosed 3 mg/m2 (up to one 4.5 mg vial) on Days 1, 4 and 7. All paediatric doses must be checked against a children's formulary and the UK SPC before administration.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

Contraindications

History of hypersensitivity to gemtuzumab ozogamicin or any of its components or excipients — reactions have included anaphylaxis

Side effects

Haemorrhage — severe, including fatal, haemorrhage may occur at recommended doses; monitor platelet counts frequently
Hepatotoxicity, including life-threatening and sometimes fatal hepatic veno-occlusive disease (VOD) — VOD was reported in 6/131 (5%) adults in ALFA-0701, median 9 days from dose to onset
Infusion-related reactions, including anaphylaxis — monitor during and for at least 1 hour after the end of the infusion
Infection, fever and febrile neutropenia (more than 15% of patients)
Nausea, vomiting, constipation, mucositis and decreased appetite (more than 15% of patients)
Increased AST and increased ALT, headache and rash (more than 15% of patients)

Clinical monograph

How it works

Its anti-CD33 antibody binds leukaemic blasts and, on internalisation, releases the DNA-damaging calicheamicin derivative that causes double-strand breaks and apoptosis.

Prescribing in practice

Hepatotoxicity, including potentially fatal veno-occlusive disease (sinusoidal obstruction syndrome), is a key risk and requires close monitoring of liver function and clinical vigilance, particularly around stem-cell transplant.
Severe and sometimes fatal infusion reactions can occur, so give premedication and administer under supervision with the infusion slowed or stopped if reactions develop.
Profound myelosuppression and tumour lysis syndrome can occur; ensure supportive care and blood-count monitoring.

Monitoring

Monitor liver function tests (watching for veno-occlusive disease), full blood count, and for infusion reactions and tumour lysis around each dose.

Counselling the patient

Report any fever, chills, breathlessness or rash during or after the infusion.
Tell your team about abdominal pain, swelling or yellowing of the skin or eyes.
Attend all blood tests, as your counts and liver will be monitored closely.

Evidence & guidelines

Gemtuzumab ozogamicin is licensed for CD33-positive acute myeloid leukaemia on the basis of randomised trial data, with its veno-occlusive disease risk well characterised in the SPC and haematology literature.

Reference: NICE TA545; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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