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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Gemtuzumab ozogamicin is a CD33-directed antibody-drug conjugate (ADC). It consists of a humanized anti-CD33 monoclonal antibody covalently linked to the cytotoxic agent calicheamicin, which causes DNA double-strand breaks leading to cell death.
## Primary Indications
* Newly diagnosed CD33-positive acute myeloid leukemia (AML) in adults and pediatric patients ≥1 month.
* Relapsed or refractory CD33-positive AML in adults and pediatric patients ≥2 years.
## Adult Dosing
* **Newly Diagnosed AML:** 3 mg/m² (up to a maximum of one 4.5 mg vial) on Days 1, 4, and 7 in combination with daunorubicin and cytarabine.
* **Relapsed/Refractory AML:** 3 mg/m² (up to a maximum dose of one 4.5 mg vial) on Days 1, 4, and 7 as a single agent.
## Pediatric Dosing
* **≥1 Month:** 3 mg/m² (for patients with BSA ≥0.6 m²) or 0.1 mg/kg (for patients with BSA <0.6 m²).
* **Schedule:** Days 1, 4, and 7. Follow specific institutional protocols for combination regimens vs. monotherapy.
## Dose Adjustments
* **Hepatotoxicity:** If total bilirubin >2x ULN or AST/ALT >5x ULN prior to a scheduled dose, delay dose until recovery to ≤ULN or baseline.
* **Permanent Discontinuation:** Discontinue if sinusoidal obstruction syndrome (SOS)/veno-occlusive disease (VOD) is diagnosed.
* **Infusion Reaction:** Interrupt or decrease infusion rate; discontinue if severe.
## Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin or any of its components.
* Prior severe or life-threatening hypersensitivity reaction to the drug.
## Adverse Effects
* **Hepatotoxicity:** Including severe, potentially fatal veno-occlusive disease (VOD/SOS).
* **Myelosuppression:** Severe neutropenia, thrombocytopenia, and anemia.
* **Infusion-Related Reactions:** Fever, chills, hypotension, and dyspnea (premedication with steroid, antihistamine, and acetaminophen is required).
* **Infection:** Increased risk due to prolonged myelosuppression.
* **Tumor Lysis Syndrome (TLS).**
## Key Drug Interactions
* **Hepatotoxic Agents:** Use with caution; may increase the risk of VOD/SOS.
* **Myelosuppressive Agents:** Concurrent use may potentiate hematologic toxicity; dose adjustments or clinical monitoring required per protocol.
## Monitoring
* **Hepatic:** Monitor ALT, AST, total bilirubin, and alkaline phosphatase frequently during therapy and for signs/symptoms of VOD (weight gain, hepatomegaly, ascites).
* **Hematologic:** Complete blood counts (CBC) frequently to monitor for recovery of counts.
* **Electrolytes:** Monitor for signs of Tumor Lysis Syndrome and initiate prophylaxis (hydration/allopurinol).
## Clinical Pearls
* **Premedication:** Always administer an antihistamine, acetaminophen, and a corticosteroid (e.g., prednisone 1 mg/kg) prior to each dose to mitigate infusion reactions.
* **VOD Risk:** Patients undergoing hematopoietic stem cell transplant (HSCT) after Mylotarg are at significantly higher risk for VOD. Avoid hepatotoxic conditioning regimens where possible.
* **Dosing Limits:** For adults, rounding the dose to the nearest vial size (4.5 mg) is common practice to prevent wastage, but strictly respect the maximum dose per cycle; confirm local protocol for rounding.
* **Handling:** Must be protected from light during reconstitution and infusion.
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**Educational Disclaimer:** This information is for educational purposes only. Drug dosing, contraindications, and precautions are subject to change. Always verify the most current prescribing information (package insert) and institutional protocols before ordering or administering any medication. Consult a licensed pharmacist or physician for clinical decisions.
