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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Mylotarg is a humanized antibody-drug conjugate (ADC) that targets CD33, a protein found on the surface of myeloid leukemia cells. It delivers a cytotoxic agent (calicheamicin) directly to cancer cells, leading to DNA damage and cell death.
## Primary Indications
* Acute Myeloid Leukemia (AML) in adults who are newly diagnosed and unfit for intensive chemotherapy.
* Relapsed or refractory AML in adults.
## Adult Dosing
**Newly Diagnosed AML (unfit for intensive chemotherapy):**
* Cycle 1: 3 mg/m² on Day 1, 13, and 25.
* Cycle 2 (if no unacceptable toxicity or disease progression): 3 mg/m² on Day 1, 13, and 25.
* If Cycle 2 is not administered: 6 mg/m² on Day 1, 13, and 25.
* **Maximum dose per administration is 4.5 mg.**
**Relapsed or Refractory AML:**
* First cycle: 6 mg/m² on Day 1.
* Second cycle (if no unacceptable toxicity or disease progression): 3 mg/m² on Day 1, 4, and 7.
* **Maximum dose per administration is 4.5 mg.**
## Pediatric Dosing
The safety and efficacy of Mylotarg in pediatric patients have not been established.
## Dose Adjustments
* **Hepatotoxicity:** Dose interruption or discontinuation may be necessary based on the severity of liver enzyme elevations or bilirubin levels. Specific guidelines for dose reduction or discontinuation based on AST/ALT and bilirubin levels are detailed in the full prescribing information.
* **Thrombocytopenia:** Monitor platelet counts closely. While Myelotarg can cause thrombocytopenia, it is often a component of the disease itself. Specific dose adjustments are not typically recommended solely for thrombocytopenia unless related to veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS).
* **VOD/SOS:** Discontinue Mylotarg permanently for patients who develop VOD/SOS.
## Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin, calicheamicin, or any component of the formulation.
## Adverse Effects
**Black Box Warnings:**
* **Hepatotoxicity:** Severe, potentially fatal hepatotoxicity, including VOD/SOS, has occurred. Risk factors include prior stem cell transplant, prior chemotherapy, and severe baseline liver dysfunction.
* **Myelosuppression:** Severe neutropenia, thrombocytopenia, and anemia can occur.
**Common Adverse Effects:**
* Febrile neutropenia
* Nausea, vomiting
* Diarrhea
* Mucositis
* Headache
* Fever
* Fatigue
* Rash
* Anemia
* Thrombocytopenia
* Increased liver enzymes (AST, ALT)
* Hyperbilirubinemia
## Key Drug Interactions
* **Warfarin:** Increased risk of bleeding. Close monitoring of INR is recommended.
* **Strong CYP3A4 Inhibitors/Inducers:** Gemtuzumab ozogamicin is metabolized to calicheamicin, which is a substrate of CYP3A4. Co-administration with strong CYP3A4 inhibitors or inducers may alter calicheamicin exposure, though the clinical significance is not fully characterized.
## Monitoring
* **Hepatotoxicity:** Monitor liver function tests (AST, ALT, bilirubin) frequently, especially during the first cycle and after dose increases. Monitor for signs and symptoms of VOD/SOS.
* **Myelosuppression:** Monitor complete blood counts (CBC) with differential and platelet counts regularly.
* **Bleeding:** Monitor for signs and symptoms of bleeding.
* **Infusion Reactions:** Monitor for signs and symptoms of infusion reactions during and after administration.
* **Pregnancy:** Perform pregnancy testing for females of reproductive potential.
## Clinical Pearls
* Mylotarg administration requires careful patient selection, particularly regarding hepatic function and prior treatment history.
* Vigilant monitoring for hepatotoxicity, especially VOD/SOS, is crucial due to its potentially fatal nature.
* Due to the risk of severe myelosuppression, appropriate prophylactic measures (e.g., growth factors, antibiotics) should be considered.
* The maximum dose per administration is 4.5 mg, regardless of the calculated dose based on m².
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**Disclaimer:** This information is intended for educational purposes and does not substitute for professional medical advice. Always consult the most current prescribing information and your healthcare provider for any health concerns or before making any decisions related to your health or treatment.
