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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Mylotarg is a CD33-directed antibody-drug conjugate (ADC). It delivers the cytotoxic agent calicheamicin to CD33-expressing leukemic cells. It carries a **Boxed Warning for hepatotoxicity, including fatal veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS).**
## Primary Indications
* Newly diagnosed CD33-positive acute myeloid leukemia (AML) in adults and pediatric patients ≥1 month.
* Relapsed or refractory CD33-positive AML in adults and pediatric patients ≥2 years.
## Adult Dosing
* **Newly Diagnosed AML:** 3 mg/m² (up to a max of one 4.5 mg vial) on days 1, 4, and 7 in combination with daunorubicin and cytarabine.
* **Relapsed/Refractory AML:** 3 mg/m² (up to a max of 4.5 mg) on days 1, 4, and 7 as a single agent.
* *Note: Dosing is based on body surface area (BSA).*
## Pediatric Dosing
* **Patients ≥1 month:** 3 mg/m² (up to a max of 4.5 mg) on days 1, 4, and 7 in combination with chemotherapy.
* **Patients ≥2 years:** 3 mg/m² (up to a max of 4.5 mg) on days 1, 4, and 7 as single-agent monotherapy.
* *Note: Always verify BSA-based calculations; rounding to the nearest 0.1 mg is common per institutional policy.*
## Dose Adjustments
* **Infusion reactions:** Interrupt or slow infusion rate.
* **Hepatotoxicity:** If signs of VOD/SOS or severe liver baseline enzyme elevation occur, discontinue permanently or hold until resolution per protocol.
* **No specific renal dosage adjustments:** Formal studies in severe renal impairment have not been conducted.
## Contraindications
* Known severe hypersensitivity to gemtuzumab ozogamicin or any of its components.
## Adverse Effects
* **Severe/Fatal:** Hepatotoxicity (VOD/SOS), infusion-related reactions (hypotension, bronchospasm), hemorrhage, and severe myelosuppression (prolonged thrombocytopenia).
* **Common:** Infection, nausea, stomatitis, constipation, pyrexia, and headache.
## Key Drug Interactions
* **Hepatotoxic Agents:** Avoid concomitant use with other drugs known to cause liver injury or VOD (e.g., azole antifungals like posaconazole as prolonged prophylaxis, or stem cell transplant conditioning regimens) without strict monitoring.
* **CYP3A4 inhibitors/inducers:** While not primarily metabolized via CYP, exercise caution when co-administering with strong inhibitors/inducers due to the complexity of AML treatment protocols.
## Monitoring
* **Liver Function Tests:** Monitor ALT, AST, total bilirubin, and alkaline phosphatase prior to each dose.
* **CBC:** Monitor blood counts frequently for myelosuppression.
* **Infusion monitoring:** Observe for signs of infusion-related reactions (respiratory distress, hypotension).
* **Toxicity:** Vigilant assessment for signs of VOD/SOS (weight gain, right upper quadrant pain, jaundice, ascites).
## Clinical Pearls
* **Premedication:** Always administer corticosteroids, antihistamines, and acetaminophen prior to each dose to mitigate infusion reactions.
* **Handling:** Must be reconstituted and diluted using strict aseptic techniques; it is light-sensitive and must be protected from light during infusion.
* **VOD Risk:** The risk of VOD is highest in patients undergoing hematopoietic stem cell transplant (HSCT) either before or after Mylotarg therapy.
* **Variable Protocols:** Dosing frequency and combination therapy regimens vary significantly by clinical trial and institutional protocols. Always consult the specific clinical pathway or protocol currently in use.
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*Educational Disclaimer: This information is for educational purposes only and does not constitute medical advice. Prescribing information, institutional protocols, and clinical guidelines change frequently. Always verify the current prescribing information (package insert) and consult your institution’s oncology pharmacist or clinical guidelines before administering chemotherapy.*
