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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Mylotarg is a CD33-directed antibody-drug conjugate consisting of a humanized anti-CD33 monoclonal antibody covalently linked to the cytotoxic agent calicheamicin. It is designed to deliver the payload specifically to CD33-expressing leukemia cells, causing double-strand DNA 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 (Combinational):** 3 mg/m² (up to a maximum dose of 4.5 mg) on days 1, 4, and 7 in combination with daunorubicin and cytarabine.
* **Relapsed/Refractory AML (Monotherapy):** 9 mg/m² on day 1. If only partial response is achieved, a second dose of 3 mg/m² may be administered on day 8.
* *Note: Always verify exact dosing against local institutional protocol and specific clinical trial parameters.*
## Pediatric Dosing
* **Newly diagnosed AML (Combinational):**
* BSA ≥ 0.6 m²: 3 mg/m² (max 4.5 mg) on days 1, 4, and 7.
* BSA < 0.6 m²: 0.1 mg/kg on days 1, 4, and 7.
* **Relapsed/Refractory AML (Monotherapy):**
* 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.
## Dose Adjustments
* **Hepatic Impairment:** Avoid in patients with severe hepatic impairment (total bilirubin > 2x ULN, or AST/ALT > 2.5x ULN). Dosage reductions may be required for mild/moderate impairment based on clinical judgment.
* **Toxicity:** Hold or discontinue for severe infusion-related reactions, severe pulmonary toxicity, or persistent grade 3/4 non-hematologic toxicities.
## Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin.
* Patients with documented moderate or severe hepatic impairment.
## Adverse Effects
* **Hepatotoxicity:** Including Veno-Occlusive Disease (VOD)/Sinusoidal Obstruction Syndrome (SOS), especially in patients undergoing hematopoietic stem cell transplant (HSCT).
* **Myelosuppression:** Grade 3/4 thrombocytopenia, neutropenia, and anemia.
* **Infusion-Related Reactions:** Fever, chills, hypotension, and dyspnea (premedication with corticosteroids, antihistamines, and acetaminophen is required).
* **Infections:** Significant risk of opportunistic infections due to neutropenia.
* **Hemorrhage:** Directly related to severe thrombocytopenia.
## Key Drug Interactions
* **Hepatotoxic Agents:** Co-administration with other hepatotoxic drugs increases the risk of VOD/SOS.
* **Live Vaccines:** Avoid vaccination with live or live-attenuated vaccines due to immunosuppression.
## Monitoring
* **Liver Function:** Pre-treatment and during treatment; monitor for signs of VOD/SOS (jaundice, weight gain, ascites, hepatomegaly).
* **CBC with differential:** Frequently monitor blood counts until recovery.
* **Infusion Site:** Monitor closely during and for at least 1 hour after infusion for hypersensitivity reactions.
* **Electrolytes and Renal Function:** Baseline and regular monitoring as clinically indicated.
## Clinical Pearls
* **Premedication:** Always administer corticosteroids, antihistamines, and acetaminophen 30 to 60 minutes prior to every infusion to reduce the severity of infusion reactions.
* **VOD Risk:** The risk of VOD is significantly higher if Mylotarg is followed by HSCT. A minimum 2-week interval between the last dose of Mylotarg and HSCT is recommended if possible.
* **Stability:** The reconstituted product must be protected from light and used immediately.
* **Handling:** Must be handled as a hazardous cytotoxic agent using appropriate protective equipment and containment.
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**Educational Disclaimer:** This information is for educational purposes only and does not replace professional medical judgment. Always verify current prescribing information, institutional protocols, and FDA package inserts before administering any medication.
