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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Gemtuzumab ozogamicin is a CD33-directed antibody-drug conjugate (ADC). It consists of a humanized anti-CD33 monoclonal antibody covalently linked to the cytotoxic agent calicheamicin, which induces double-strand DNA breaks leading to cell death.
## Primary Indications
* Newly diagnosed CD33-positive acute myeloid leukemia (AML) in adults and pediatric patients aged 1 month and older.
* Relapsed or refractory CD33-positive AML in adults and pediatric patients aged 2 years and older.
## Adult Dosing
Induction and consolidation dosing vary based on clinical protocol (e.g., in combination with daunorubicin/cytarabine or as monotherapy). Always verify regimen-specific protocols.
* **Combination therapy (newly diagnosed):** 3 mg/m² (up to a maximum dose of 4.5 mg) on Days 1, 4, and 7.
* **Monotherapy (relapsed/refractory):** 9 mg/m² as a single dose.
* **Maximum single dose:** 9 mg/m² for monotherapy; 4.5 mg for combination therapy.
## Pediatric Dosing
* **Aged 1 month and older:** Dosage is based on BSA for patients ≥0.6 m² or weight for patients <0.6 m².
* **BSA ≥0.6 m²:** 3 mg/m² on Days 1, 4, and 7.
* **Weight <0.6 m²:** 0.1 mg/kg on Days 1, 4, and 7.
* *Note:* Ensure the dose for patients <0.6 m² does not exceed the equivalent 3 mg/m² BSA dose for a patient with BSA 0.6 m².
## Dose Adjustments
* **Hepatic Impairment:** Avoid in patients with total bilirubin >2x ULN or AST/ALT >2.5x ULN.
* **Toxicity:** Consider dose interruption or discontinuation for severe infusion-related reactions, prolonged myelosuppression, or symptoms of VOD/SOS.
## Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin or any component of the formulation.
## Adverse Effects
* **Veno-Occlusive Disease (VOD)/Sinusoidal Obstruction Syndrome (SOS):** High-risk, especially in patients undergoing hematopoietic stem cell transplant (HSCT), high-dose therapy, or having pre-existing liver disease.
* **Myelosuppression:** Severe neutropenia, thrombocytopenia, and anemia.
* **Hepatotoxicity:** Elevation of liver enzymes and bilirubin.
* **Infusion-related reactions:** Hypotension, bronchospasm, and dyspnea.
* **Infections:** Increased risk due to prolonged myelosuppression.
## Key Drug Interactions
* **Hepatotoxic agents:** Use with extreme caution as concurrent use may increase the risk of VOD/SOS.
* **QT-prolonging agents:** Potential for additive effects on cardiac conduction.
## Monitoring
* **Liver Function:** Baseline and periodic monitoring of total bilirubin, ALT, AST, and alkaline phosphatase. Monitor closely for signs of VOD/SOS (rapid weight gain, jaundice, ascites, hepatomegaly).
* **CBC:** Frequent monitoring of blood counts for myelosuppression.
* **Cardiac:** Baseline and periodic ECGs if clinically indicated.
* **Infusion:** Monitor closely for signs of hypersensitivity throughout the infusion.
## Clinical Pearls
* **Pre-medication:** Mandatory premedication with a corticosteroid, antihistamine, and antipyretic 30–60 minutes prior to infusion to attenuate infusion-related reactions.
* **HSCT Timing:** If HSCT is planned, the interval between the final Mylotarg dose and transplantation should be carefully evaluated due to the increased risk of VOD.
* **Handling:** Mylotarg is cytotoxic; follow hazardous drug handling protocols.
* **Uncertainty:** Dosing protocols are highly dependent on the specific treatment backbone; always cross-reference with institutional oncology guidelines or clinical trial protocols.
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**Disclaimer:** This information is for educational purposes only. Drug information, protocols, and clinical standards can change rapidly. Always verify current prescribing information, institutional protocols, and FDA-approved labels before administering any medication.
