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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Gemtuzumab ozogamicin is a CD33-directed antibody-drug conjugate. It consists of a humanized anti-CD33 monoclonal antibody covalently linked to the cytotoxic agent calicheamicin, a potent DNA-damaging antibiotic.
## 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
Must be administered as a 2-hour IV infusion. Premedication with a corticosteroid, antihistamine, and acetaminophen is required.
* **Newly diagnosed AML:** 3 mg/m² (up to a maximum dose of 4.5 mg) on days 1, 4, and 7 in combination with chemotherapy.
* **Relapsed/Refractory AML:** 3 mg/m² (up to a maximum dose of 4.5 mg) on days 1, 4, and 7 as a single agent.
## Pediatric Dosing
**Note:** Dosing is weight-based for patients with a body surface area (BSA) < 0.6 m².
* **BSA ≥ 0.6 m²:** 3 mg/m² (up to a maximum dose of 4.5 mg) on days 1, 4, and 7.
* **BSA < 0.6 m²:** 0.1 mg/kg on days 1, 4, and 7.
## Dose Adjustments
* **Hepatotoxicity:** If total bilirubin > 2x ULN or AST/ALT > 2.5x ULN prior to a dose, hold treatment until recovery to baseline or ≤ Grade 1.
* **Veno-occlusive disease (VOD):** Discontinue permanently if signs of VOD/SOS develop.
## Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin or any component of the formulation.
## Adverse Effects
* **Hepatotoxicity:** Including severe, sometimes fatal, veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS).
* **Myelosuppression:** Profound neutropenia, thrombocytopenia, and anemia.
* **Infusion-Related Reactions:** Fever, chills, hypotension, and dyspnea.
* **Infections:** Increased risk due to prolonged neutropenia.
* **Tumor Lysis Syndrome:** Monitoring required especially in patients with high peripheral blast counts.
## Key Drug Interactions
* **Strong CYP3A4 inhibitors/inducers:** Use caution. Monitor closely for altered efficacy or increased toxicity.
* **Hepatotoxic Agents:** Risk of VOD may be exacerbated by the use of gemtuzumab ozogamicin in patients following hematopoietic stem cell transplant (HSCT) or with other hepatotoxic medications.
## Monitoring
* **Liver Function:** ALT, AST, total bilirubin, and alkaline phosphatase prior to each dose and throughout treatment.
* **CBC:** Complete blood count with differential performed frequently to monitor for recovery of marrow function post-treatment.
* **Signs/Symptoms:** Monitor for clinical signs of VOD (e.g., rapid weight gain, hepatomegaly, ascites, jaundice).
* **ECG/Cardiac:** Monitor for QT interval prolongation.
## Clinical Pearls
* **VOD Risk:** The risk of VOD is significantly higher in patients undergoing hematopoietic stem cell transplant (HSCT) before or after Mylotarg therapy.
* **Infusion Timing:** Always premedicate 30–60 minutes prior to infusion to reduce the risk of reaction.
* **Extravasation:** Not a vesicant, but follow standard site precautions for monoclonal antibodies.
* **Stability:** Administer immediately after preparation. If delayed, refrigerate at 2°C–8°C for no more than 16 hours.
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**Disclaimer:** This information is for educational purposes only. Clinical dosing may vary based on institutional protocols, specific clinical trial enrollment, or patient-specific factors. Always consult the most current FDA-approved prescribing information and your institutional pharmacy or hematology-oncology department before prescribing or administering medication.
