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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Mylotarg is a CD33-directed antibody-drug conjugate (ADC) consisting of a humanized anti-CD33 monoclonal antibody linked to the cytotoxic agent calicheamicin. It is primarily used for the treatment of CD33-positive acute myeloid leukemia (AML).
## Primary Indications
* Newly diagnosed CD33-positive AML in adults and pediatric patients aged 1 month and older (in combination with chemotherapy).
* Relapsed or refractory CD33-positive AML in adults and pediatric patients aged 2 years and older as a single agent.
## Adult Dosing
Standard dosing is based on body surface area (BSA) and clinical setting; **always refer to institutional protocol.**
* **Newly diagnosed AML (combination):** 3 mg/m² (up to a maximum dose of 4.5 mg) on days 1, 4, and 7 of the induction cycle.
* **Relapsed/Refractory AML (single agent):** 9 mg/m² as a single dose.
## Pediatric Dosing
* **Aged $\ge$ 1 month (newly diagnosed):** 3 mg/m² (maximum 4.5 mg) on days 1, 4, and 7. For patients with BSA < 0.6 m², the dose is 0.1 mg/kg on days 1, 4, and 7.
* **Aged $\ge$ 2 years (relapsed/refractory):** 9 mg/m² (if BSA $\ge$ 0.6 m²) or 0.3 mg/kg (if BSA < 0.6 m²) as a single dose.
## Dose Adjustments
* **Hepatic Impairment:** Avoid in patients with severe hepatic impairment (total bilirubin > 2x ULN, AST/ALT > 2.5x ULN). No dose adjustment is required for mild impairment, but monitor closely.
* **Infusion Reactions:** If a reaction occurs, interrupt or discontinue infusion; consider premedication (corticosteroids, antihistamines, acetaminophen) for subsequent doses.
## Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin or any of its components.
* Known severe hepatic impairment (as defined above).
## Adverse Effects
* **Hepatotoxicity:** Including veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS). Increased risk if followed by hematopoietic stem cell transplantation (HSCT).
* **Myelosuppression:** Prolonged neutropenia, thrombocytopenia, and anemia.
* **Infusion-Related Reactions:** Fever, chills, hypotension, and dyspnea (usually during or shortly after infusion).
* **Infections:** Increased risk of opportunistic infections secondary to neutropenia.
* **Hemorrhage:** Associated with thrombocytopenia.
## Key Drug Interactions
* **Hepatotoxic Agents:** Avoid concomitant use with other known hepatotoxic medications to minimize the risk of VOD/SOS.
* **Live Vaccines:** Avoid live virus vaccines during therapy; immune response may be impaired.
## Monitoring
* **Liver Function:** ALT, AST, total bilirubin, and alkaline phosphatase baseline and prior to each dose.
* **VOD/SOS:** Monitor for signs of jaundice, hepatomegaly, rapid weight gain, or ascites.
* **CBC:** Frequent monitoring of blood counts for recovery of neutrophils and platelets.
* **Infusion:** Monitor closely for signs of infusion-related reactions (e.g., hypotension, bronchospasm).
## Clinical Pearls
* **VOD/SOS Risk:** The risk of VOD/SOS is significantly elevated in patients undergoing HSCT. Ensure at least 60 days elapse between the last dose of Mylotarg and HSCT unless clinically mandated.
* **Handling:** Must be protected from light and reconstituted using aseptic technique.
* **Premedication:** Always premedicate with acetaminophen, diphenhydramine, and a corticosteroid 1 hour prior to infusion to attenuate infusion-related reactions.
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**Educational Disclaimer:** This information is for educational purposes only. Dosing, contraindications, and interaction profiles can change; always verify the current official prescribing information (package insert) and consult your institution’s clinical guidelines before prescribing or administering medication.
