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# Mylotarg (gemtuzumab ozogamicin) ## Overview Mylotarg is a targeted immunotherapy, specifically an antibody-drug conjugate, that targets the CD33 protein found on the surface of leukemia cells. It consists of an anti-CD33 antibody linked to a potent cytotoxic agent (ozogamicin). ## Primary Indications * Treatment of newly diagnosed CD33-positive acute myeloid leukemia (AML) in adult patients. * Treatment of relapsed or refractory CD33-positive AML in adult patients. ## Adult Dosing **For Newly Diagnosed CD33-Positive AML:** * **Induction:** 3 mg/m² on days 1, 4, and 7. If the patient does not achieve a complete remission (CR) and is to proceed to consolidation, a second course may be given on days 1, 4, and 7 of the next cycle. * **Consolidation:** 3 mg/m² on day 1 of each cycle for up to 4 cycles. * **Maintenance:** Not applicable. **For Relapsed or Refractory CD33-Positive AML:** * **First course:** 3 mg/m² on day 1. * **Second course:** 3 mg/m² on day 1, provided there is no progressive disease and the patient tolerates the first course. ## Pediatric Dosing Dosing for pediatric patients is not established. ## Dose Adjustments * **Hepatotoxicity:** Dose interruption or discontinuation may be necessary. If bilirubin is > 2 mg/dL or AST/ALT are > 5 times the upper limit of normal, withhold Mylotarg. Resume when bilirubin is ≤ 2 mg/dL and AST/ALT are ≤ 5 times the upper limit of normal. If severe hepatotoxicity occurs, consider permanent discontinuation. * **Thrombocytopenia:** Monitor platelet counts closely. Dose reduction is not specified, but clinical judgment should be used. Transfusion support is critical. * **Overlapping Toxicity:** If myelosuppression (including thrombocytopenia, neutropenia, and anemia) occurs with the first course and is considered prolonged or severe, consider delaying the second course until recovery. ## Contraindications * Known hypersensitivity to gemtuzumab ozogamicin or any component of the formulation. ## Adverse Effects * **Hepatotoxicity:** Veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS) is a serious and potentially fatal adverse event. Risk factors include prior stem cell transplant, liver disease, and higher cumulative doses. * **Myelosuppression:** Including thrombocytopenia, neutropenia, anemia, and febrile neutropenia. * **Bleeding Events:** Including intracranial hemorrhage and gastrointestinal hemorrhage. * **Infusion-Related Reactions:** Fever, rash, chills, dyspnea. * **Gastrointestinal:** Nausea, vomiting, diarrhea, stomatitis. * **Infections:** Sepsis, pneumonia. ## Key Drug Interactions * **Live Vaccines:** Avoid administration during treatment and for at least 6 months after the last dose due to the risk of severe infection. * **Strong CYP3A4 Inhibitors/Inducers:** Ozogamicin is metabolized by CYP3A4. Concomitant use may alter exposure to the cytotoxic moiety, but specific interaction data and recommendations are limited. * **Anticoagulants/Antiplatelets:** Increased risk of bleeding, especially in patients with thrombocytopenia. ## Monitoring * **Hepatotoxicity:** Frequent monitoring of liver function tests (bilirubin, AST, ALT) is crucial, especially in patients with risk factors. * **Complete Blood Counts (CBCs):** With differential and platelet counts, at least weekly during treatment and until recovery. * **Signs and Symptoms of Bleeding and Infection:** Monitor closely. * **Infusion Reactions:** Monitor during and after infusion. ## Clinical Pearls * Mylotarg can cause severe and potentially fatal hepatotoxicity, particularly VOD/SOS. Cumulative dose is a significant risk factor; generally limit total exposure to 2 courses for relapsed/refractory AML. * Close monitoring of liver function, blood counts, and for signs of bleeding and infection is paramount. * Ensure adequate supportive care, including transfusions and prophylactic/treatment of infections. * Administer premedications for infusion reactions as per institutional protocol (e.g., antihistamines, antipyretics, corticosteroids). *** *This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and your institution's protocols before making any treatment decisions.*