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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Mylotarg is a CD33-directed antibody-drug conjugate (ADC). It consists of a humanized anti-CD33 monoclonal antibody covalently linked to calicheamicin, a potent cytotoxic antitussive agent that causes DNA double-strand breaks.
## Primary Indications
* Newly diagnosed CD33-positive acute myeloid leukemia (AML) in adults.
* Relapsed or refractory CD33-positive AML in adults and pediatric patients aged 2 years and older.
## Adult Dosing
Standard dosing is based on body surface area (BSA) and cycle timing (protocol-dependent):
* **Newly Diagnosed AML:** 3 mg/m² (up to a max dose of 5 mg) on days 1, 4, and 7 in combination with daunorubicin and cytarabine.
* **Relapsed/Refractory AML:** 9 mg/m² as a single dose for monotherapy.
* *Note: Always consult local institutional protocols as dosing regimens vary significantly based on combination chemotherapy schedules.*
## Pediatric Dosing
**Aged 2 years and older (Relapsed/Refractory AML):**
* **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.
* *Maximum individual dose: 5 mg.*
## Dose Adjustments
* **Hepatic Impairment:** Avoid in patients with severe hepatic impairment (Total bilirubin > 2x ULN, AST/ALT > 2.5x ULN).
* **Infusion Reactions:** Interrupt infusion for symptoms; resume at a slower rate if Grade 1 or 2, permanent discontinuation for Grade 3 or 4.
* **Toxicity:** Dose modifications for severe hematologic or non-hematologic toxicity vary by clinical protocol; hold therapy for persistent severe toxicities.
## Contraindications
* Hypersensitivity to gemtuzumab ozogamicin or any component of the formulation.
## Adverse Effects
* **Hepatotoxicity:** Including veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS). Increased risk in patients undergoing hematopoietic stem cell transplant (HSCT).
* **Myelosuppression:** Profound neutropenia, thrombocytopenia, and anemia.
* **Infusion-Related Reactions:** Fever, chills, hypotension, and dyspnea.
* **Infections:** Increased risk due to prolonged myelosuppression.
* **Tumor Lysis Syndrome (TLS):** Particularly in patients with high white blood cell counts.
## Key Drug Interactions
* **Strong CYP3A4 Inhibitors/Inducers:** Use caution, though the contribution of metabolic clearance for the cytotoxic payload to total drug clearance is limited.
* **Hepatotoxic Agents:** Concomitant use increases risk of VOD/SOS.
* **Live Vaccines:** Avoid due to immunosuppressed state.
## Monitoring
* **Liver Function Tests:** Monitor bilirubin, ALT, and AST prior to each dose and after treatment (watch for signs of VOD/SOS like jaundice, hepatomegaly, or rapid weight gain).
* **Complete Blood Count:** Monitor frequently for recovery of cytopenias.
* **Electrolytes/Renal Function:** Monitor closely for TLS.
## Clinical Pearls
* **Premedication:** Always administer corticosteroids, antihistamines, and acetaminophen 1 hour before infusion to reduce infusion-related reaction incidence.
* **VOD Risk:** Avoid gemtuzumab ozogamicin for at least 2 weeks post-HSCT or, conversely, ensure adequate time between last dose and conditioning for transplant.
* **Handling:** Mylotarg is a cytotoxic drug; handle with strict hazardous drug protocols. Reconstituted solutions must be protected from light and used immediately.
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*Disclaimer: This information is for educational purposes only. Clinical protocols must be verified against current institutional guidelines, updated FDA prescribing information, and patient-specific factors before administration.*
