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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-positive leukemic cells. It is a highly potent agent requiring strict adherence to infusion protocols to mitigate hypersensitivity and infusion-related reactions.
## 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
* **Newly Diagnosed AML (Combination Therapy):** 3 mg/m² (up to a maximum dose of 5 mg) on days 1, 4, and 7 in combination with daunorubicin and cytarabine.
* **Relapsed/Refractory AML (Monotherapy):** 9 mg/m² as a single dose.
* *Note: Dosing based on body surface area (BSA).*
## Pediatric Dosing
* **Newly Diagnosed AML (Combination Therapy):**
* BSA ≥ 0.6 m²: 3 mg/m² on days 1, 4, and 7.
* BSA < 0.6 m²: 0.1 mg/kg on days 1, 4, and 7.
* **Relapsed/Refractory AML:** 3 mg/m² (BSA ≥ 0.6 m²) or 0.1 mg/kg (BSA < 0.6 m²) on days 1, 4, and 7.
* *Maximum dose: 5 mg per dose.*
## Dose Adjustments
* **Hepatic Impairment:** Avoid in patients with total bilirubin > 2x ULN or AST/ALT > 2.5x ULN.
* **VOD/SOS:** Permanently discontinue if severe veno-occlusive disease (VOD) occurs.
* **Infusion Reactions:** Interrupt infusion for Grade 2+ reactions; resume at a slower rate once resolved. Discontinue for anaphylaxis.
## Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin or any component of the formulation.
## Adverse Effects
* **Hepatotoxicity:** Including severe VOD/sinusoidal obstruction syndrome (SOS), particularly post-hematopoietic stem cell transplant (HSCT).
* **Hematologic:** Severe neutropenia, thrombocytopenia, and anemia.
* **Infections:** High risk of opportunistic infections (fungal, bacterial, viral).
* **Infusion Reactions:** Fever, chills, hypotension, and dyspnea.
* **Hemorrhage:** Associated with thrombocytopenia.
## Key Drug Interactions
* **Hepatotoxic Drugs:** Exercise caution with concomitant use of drugs known to cause liver injury or VOD.
* **Live Vaccines:** Avoid live vaccines as they may cause severe or fatal infections in immunocompromised patients.
## Monitoring
* **Hepatic Function:** LFTs (bilirubin, ALT, AST, alkaline phosphatase) at baseline and before each dose. Monitor closely for signs of VOD (weight gain, hepatomegaly, ascites).
* **Hematologic:** CBCs with differentials; frequent monitoring during induction/consolidation.
* **Electrolytes:** Monitor for tumor lysis syndrome (uric acid, potassium, phosphorus, calcium).
* **Infusion:** Continuous monitoring during the 2-hour infusion period.
## Clinical Pearls
* **Premedication:** Always administer corticosteroids, antihistamines, and antipyretics 1 hour prior to infusion to reduce the risk of infusion-related reactions.
* **VOD Risk:** The risk of VOD is greatest in patients who have undergone prior HSCT or proceed to HSCT following Mylotarg monotherapy.
* **Preparation:** Must be reconstituted and diluted using strict aseptic technique. Protect from light.
* **Timing:** Optimal timing of post-therapy HSCT remains a subject of institution-specific clinical protocol and clinical judgment. Always verify institutional guidelines regarding the wait interval between the last dose and transplant.
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**Educational Disclaimer:** This information is for educational purposes only. Prescribing information for oncology agents changes rapidly; always verify current FDA-approved labeling and institutional protocols before prescribing or administering Mylotarg. Consult the latest package insert or a clinical pharmacist for the most current data.
