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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Mylotarg is an antibody-drug conjugate that targets CD33, a protein found on the surface of myeloid leukemia cells. It delivers a cytotoxic agent (calicheamicin) directly to these cells, leading to cell death.
## Primary Indications
* Acute Myeloid Leukemia (AML) in adults who are newly diagnosed or have relapsed/refractory disease and are not eligible for intensive induction chemotherapy.
## Adult Dosing
* **For newly diagnosed AML:**
* Day 1: 3 mg/kg
* Day 4: 3 mg/kg
* Day 7: 2 mg/kg
* **For relapsed/refractory AML:**
* Cycles 1 and 2: 3 mg/kg on Day 1
* Cycle 3 (if needed): 2 mg/kg on Day 1
* Maximum single dose: 3 mg/kg.
* Maximum cumulative dose: 10 mg/kg.
## Pediatric Dosing
* The safety and efficacy in pediatric patients have not been established.
## Dose Adjustments
* **Hepatotoxicity:**
* If bilirubin > 2 mg/dL or AST/ALT > 3x upper limit of normal (ULN), withhold treatment.
* Resume at a reduced dose (e.g., 2 mg/kg for newly diagnosed AML, 1 mg/kg for relapsed/refractory AML) if bilirubin ≤ 2 mg/dL and AST/ALT ≤ 3x ULN.
* If hepatotoxicity recurs, permanently discontinue.
* **Thrombocytopenia:**
* If platelets < 50,000/mcL, withhold treatment.
* Resume when platelets ≥ 50,000/mcL.
* If severe thrombocytopenia recurs, consider dose reduction.
* **Infusion Reactions:**
* If grade 2-3 reaction, slow infusion rate.
* If grade 4 reaction, discontinue permanently.
## Contraindications
* None listed.
## Adverse Effects
* **Hepatotoxicity:** Including veno-occlusive liver disease (VOD)/sinusoidal obstruction syndrome (SOS), elevated bilirubin, elevated AST/ALT. This is a serious and potentially fatal adverse effect.
* **Myelosuppression:** Including thrombocytopenia, neutropenia, anemia.
* **Infusion-related reactions:** Fever, chills, rash, dyspnea.
* **Gastrointestinal:** Nausea, vomiting, diarrhea, stomatitis.
* **Bleeding/hemorrhage.**
* **Infections.**
## Key Drug Interactions
* **Strong CYP3A4 inhibitors/inducers:** Gemtuzumab ozogamicin is metabolized by CYP3A4. Concurrent use may alter exposure. Caution is advised.
* **Other myelosuppressive agents:** Increased risk of myelosuppression.
## Monitoring
* **Liver function tests (LFTs):** Frequently monitor bilirubin, AST, ALT, especially prior to and during treatment.
* **Complete blood counts (CBCs):** Monitor platelet count, ANC, hemoglobin.
* **Signs and symptoms of infusion reactions.**
* **Signs and symptoms of bleeding and infection.**
## Clinical Pearls
* Mylotarg carries a Black Box Warning for severe and potentially fatal hepatotoxicity, particularly VOD/SOS. Risk is higher in patients with moderate-to-severe hepatic impairment or prior HCT.
* Monitor LFTs very closely. Pre-treatment evaluation of liver function is crucial.
* Dosing is based on actual body weight.
* Administer as an intravenous infusion. Do not administer as an IV push or bolus.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for complete details and to verify dosages and safety information before prescribing or administering any medication.
