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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Gemtuzumab ozogamicin is an antibody-drug conjugate (ADC) consisting of a CD33-directed monoclonal antibody linked to the cytotoxic agent calicheamicin. It is designed to deliver a potent DNA-damaging agent to CD33-expressing leukemia cells.
## 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
* **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 on Day 1. If no response after the first dose, a second dose of 9 mg/m² may be given 14 days later.
* *Note: Dosing is based on Body Surface Area (BSA). Always verify BSA calculations.*
## Pediatric Dosing
* **Relapsed or Refractory AML (Aged 2 years and older):** 3 mg/m² on Days 1, 4, and 7.
* *Note: Dosages for pediatric patients are weight-dependent when BSA is less than 0.6 m². For BSA < 0.6 m², the dose is 0.1 mg/kg on Days 1, 4, and 7.*
## Dose Adjustments
* **Hepatotoxicity:** If total bilirubin exceeds 2x ULN or AST/ALT exceeds 5x ULN prior to a scheduled dose, withhold treatment until resolution to ≤ Grade 1.
* **Infusion-related reactions:** Interrupt or discontinue infusion based on severity (Grade 3/4 necessitates permanent discontinuation).
## Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin or any component of the product.
* History of severe or ongoing hepatic veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS).
## Adverse Effects
* **Hepatotoxicity:** Including severe, life-threatening VOD/SOS.
* **Infusion reactions:** Fever, chills, hypotension, and dyspnea (premedication with corticosteroids, antihistamines, and acetaminophen is mandatory).
* **Myelosuppression:** Prolonged neutropenia, thrombocytopenia, and anemia.
* **Infection:** Increased risk due to profound immunosuppression.
* **Tumor Lysis Syndrome (TLS):** Monitor electrolytes and renal function closely.
## Key Drug Interactions
* **Hepatotoxic agents:** Use with extreme caution as they may increase the risk of VOD/SOS.
* **Strong CYP3A4 inhibitors/inducers:** While gemtuzumab metabolisms are complex, monitor closely for changes in toxicity or efficacy.
* **Antineoplastics:** Generally avoid concomitant use with other cytotoxic agents unless part of a specific protocol.
## Monitoring
* **Hepatic:** Full liver panel (ALT, AST, alkaline phosphatase, and total bilirubin) prior to each dose. Monitor for jaundice or signs of VOD/SOS.
* **Hematologic:** CBC with differential and platelets frequently during cycles.
* **Metabolic:** Serum electrolytes, uric acid, and creatinine to monitor for TLS.
## Clinical Pearls
* **Premedication:** 30–60 minutes prior to infusion, administer acetaminophen, diphenhydramine, and a corticosteroid (e.g., 50 mg methylprednisolone).
* **VOD Risk:** The risk of VOD is significantly higher in patients undergoing hematopoietic stem cell transplantation (HSCT) post-therapy. Monitor liver function values even after treatment cessation.
* **Handling:** Must be protected from light. Reconstituted vials must be shielded from light during storage and infusion.
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**Educational Disclaimer:** This information is for educational purposes only. Drug dosing, indications, and safety information are subject to change. Always consult the latest FDA-approved package insert (Prescribing Information) and your institution’s clinical guidelines before prescribing or administering medication.
