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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 the cytotoxic agent calicheamicin. Upon binding to CD33, the complex is internalized, releasing the cytotoxic agent to induce DNA double-strand breaks and apoptosis.
## 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 4.5 mg) on Days 1, 4, and 7 of the induction cycle.
* **Relapsed or Refractory AML (Monotherapy):** 9 mg/m² as a single dose.
* *Note: Dosing is highly regimen-specific; clinicians must follow established institutional protocols or specific trial-based induction/consolidation schedules.*
## Pediatric Dosing
* **Patients ≥ 1 month (Newly Diagnosed):**
* BSA ≥ 0.6 m²: 3 mg/m² (maximum 4.5 mg) on Days 1, 4, and 7.
* BSA < 0.6 m²: 0.1 mg/kg on Days 1, 4, and 7.
* **Patients ≥ 2 years (Relapsed/Refractory):** 3 mg/m² on days 1, 4, and 7.
## Dose Adjustments
* **Hepatic/Renal Impairment:** No formal dosage adjustments provided in the manufacturer label for mild impairment; however, caution is recommended. Avoid in severe hepatic impairment (bilirubin > 2x ULN, AST/ALT > 2.5x ULN).
* **Toxicity:** Hold for severe infusion-related reactions. Permanent discontinuation is required for severe VOD/SOS or persistent Grade 3/4 non-hematologic toxicities.
## Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin or any component of the product.
* History of veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS).
## Adverse Effects
* **Hepatotoxicity:** Including fatal VOD/SOS (highest risk post-hematopoietic stem cell transplant).
* **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).**
## Key Drug Interactions
* **Hepatotoxic Agents:** Risk of additive liver injury; avoid concomitant administration where possible.
* **Strong CYP3A4 inhibitors/inducers:** While the calicheamicin payload is metabolized, clinical interactions are not clearly defined; monitor liver function closely.
## Monitoring
* **Baseline:** Complete blood count (CBC), liver function tests (bilirubin, alkaline phosphatase, ALT, AST), and electrolytes.
* **During Treatment:** Daily CBC and electrolytes during induction; regular monitoring of liver function tests (LFTs) throughout all cycles.
* **VOD/SOS:** Monitor for sudden weight gain, right upper quadrant pain, ascites, and unexplained jaundice.
## Clinical Pearls
* **Premedications:** Administer acetaminophen, an antihistamine, and a corticosteroid prior to each infusion to mitigate infusion reactions.
* **Handling:** Must be protected from light during preparation and administration.
* **VOD Risk:** The risk of VOD/SOS is significantly elevated in patients undergoing subsequent hematopoietic stem cell transplantation (HSCT) or those with prior liver dysfunction.
* **Uncertainty:** Because dosing varies significantly based on whether the agent is used as monotherapy versus in combination with cytarabine/daunorubicin, verify the specific cycle schedule against current NCCN or institutional guidelines before ordering.
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**Educational Disclaimer:** This information is for educational purposes only. Mylotarg dosing and protocols are complex and highly dependent on disease stage and clinical setting. Always verify current prescribing information, institutional protocols, and FDA-approved labeling before prescribing or administering this medication.
