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## Mylotarg (gemtuzumab ozogamicin)
### Overview
Mylotarg is an antibody-drug conjugate targeting CD33, an antigen expressed on the surface of myeloid leukemia cells. It delivers a cytotoxic agent (calicheamicin) directly to these cells.
### Primary Indications
* Treatment of newly diagnosed acute myeloid leukemia (AML) in adult patients who are **not** candidates for intensive induction chemotherapy.
* Treatment of relapsed or refractory AML in adult patients.
### Adult Dosing
* **Newly diagnosed AML (in combination with other chemotherapy for patients not eligible for intensive induction):**
* Day 1: 3 mg/m² intravenously over 2 hours.
* Day 4: 3 mg/m² intravenously over 2 hours.
* Day 7: 2 mg/m² intravenously over 2 hours.
* **Relapsed or refractory AML:**
* Cycle 1: 6 mg/m² intravenously over 2 hours. If tolerated, the dose can be increased for Cycle 2.
* Cycle 2: 6 mg/m² intravenously over 2 hours.
* **Maximum cumulative dose:** 21.1 mg/m² over the course of treatment.
### Pediatric Dosing
Dosing in pediatric patients is not established.
### Dose Adjustments
* **Hepatic Impairment:**
* If bilirubin is >1.5 times the upper limit of normal (ULN), gemtuzumab ozogamicin should not be administered.
* If bilirubin is ≤1.5 times ULN and AST is >3 times ULN, consider withholding gemtuzumab ozogamicin.
* **Renal Impairment:** No specific dose adjustment recommendations are provided, but caution is advised.
* **Infusion Reactions:** If a Grade 1-2 infusion reaction occurs, slow the infusion rate. If a Grade 3-4 reaction occurs, permanently discontinue gemtuzumab ozogamicin.
* **Hepatotoxicity:** Dose interruption or discontinuation may be necessary based on the severity of liver enzyme elevations.
### Contraindications
* None are listed for gemtuzumab ozogamicin itself. However, it should be used with caution in patients with significant hepatic or renal impairment.
### Adverse Effects
* **Very Common:** Febrile neutropenia, thrombocytopenia, anemia, neutropenia, leukopenia, nausea, vomiting, diarrhea, stomatitis, constipation, headache, rash, fatigue, pyrexia, hypokalemia, hypophosphatemia, elevated AST, elevated ALT.
* **Common:** Hepatotoxicity (including VOD/SOS), pulmonary toxicity, infusion reactions, tumor lysis syndrome, sepsis, bleeding events.
* **Hepatotoxicity (VOD/SOS):** This is a serious and potentially fatal adverse event. Risk factors include pre-existing liver disease, prior stem cell transplant, and higher doses of gemtuzumab ozogamicin.
### Key Drug Interactions
* **Warfarin:** Increased risk of bleeding. Monitor INR closely.
* **Other myelosuppressive agents:** Concomitant use with chemotherapy can potentiate myelosuppression.
### Monitoring
* **Complete Blood Counts (CBCs) with differential and platelet counts:** Frequently, especially during and after treatment, to monitor for myelosuppression and recovery.
* **Liver function tests (LFTs):** Baseline and regularly during treatment to monitor for hepatotoxicity.
* **Renal function tests:** Baseline and regularly during treatment.
* **Signs and symptoms of infusion reactions.**
* **Signs and symptoms of VOD/SOS:** Jaundice, ascites, hepatomegaly, thrombocytopenia, and elevated transaminases.
* **Signs and symptoms of bleeding events.**
### Clinical Pearls
* Mylotarg carries a boxed warning for hepatotoxicity, including VOD/SOS, and potential for bleeding events.
* Consider prophylactic measures for patients at high risk of bleeding or VOD/SOS.
* Slow infusion rates if infusion reactions occur.
* Discontinue treatment if severe hepatotoxicity or bleeding occurs.
* The maximum cumulative dose is critical to minimize the risk of severe adverse events, particularly VOD/SOS.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making treatment decisions.*
