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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Mylotarg is a CD33-directed antibody-drug conjugate (ADC) linked to the cytotoxic agent calicheamicin. It is designed to target CD33-positive cells, leading to internalization of the ADC and subsequent DNA double-strand breaks.
## Primary Indications
* Newly diagnosed CD33-positive acute myeloid leukemia (AML) in adults and pediatric patients aged 1 month and older.
* Relapsed or refractory CD33-positive AML in adults and pediatric patients aged 2 years and older.
## Adult Dosing
Standard dosing is weight-based and depends on whether it is used in combination with chemotherapy or as monotherapy:
* **Combination regimen (newly diagnosed):** 3 mg/m² (up to a maximum dose of 4.5 mg) on days 1, 4, and 7.
* **Monotherapy:** 9 mg/m² (up to a maximum dose of 13.5 mg) as a single dose on day 1. If response is insufficient but not progressive, a second dose of 9 mg/m² may be given after at least 14 days.
## Pediatric Dosing
Dosing for pediatric patients (≥1 month) follows weight-based thresholds:
* **Patients ≥12 kg:** Dose is based on body surface area (BSA) at 3 mg/m².
* **Patients <12 kg:** Dose is based on body weight at 0.1 mg/kg.
* *Note: Dosing schedules for pediatrics (e.g., number of doses and frequency) should strictly follow institutional protocols or specific trial regimens (e.g., AAML0531) as they often vary based on disease subtype and risk stratification.*
## Dose Adjustments
* **Hepatotoxicity:** If total bilirubin >2x ULN or AST/ALT >5x ULN, hold until recovery to baseline or ≤Grade 1. Permanently discontinue if severe veno-occlusive disease (VOD) or sinusoidal obstruction syndrome (SOS) occurs.
* **Infusion reactions:** Interrupt or slow infusion for mild to moderate symptoms; terminate permanently for severe anaphylaxis.
* **Hematologic:** No standard dose reduction for myelosuppression, as it is an expected effect of therapy; however, treatment should be held until recovery of counts as per local protocol.
## Contraindications
* Hypersensitivity to gemtuzumab ozogamicin or any component of the formulation.
## Adverse Effects
* **Black Box Warning:** Hepatotoxicity, including VOD/SOS, which can be fatal.
* **Hematologic:** Severe neutropenia, thrombocytopenia, and anemia.
* **Common:** Infection, hemorrhage, nausea, vomiting, fever, and stomatitis.
* **Infusion-related:** Hypotension, dyspnea, and bronchospasm (pre-medication required).
## Key Drug Interactions
* **Hepatotoxic agents:** Use with extreme caution; increased risk of VOD/SOS.
* **Live vaccines:** Avoid; immune response may be impaired due to immunosuppression.
* **Strong CYP3A inhibitors/inducers:** While the calicheamicin payload is a CYP3A4 substrate, dose adjustments are not currently standardized based on inhibitors/inducers.
## Monitoring
* **Hepatic:** Liver function tests (ALT, AST, total bilirubin, alkaline phosphatase) prior to every dose and closely for signs of VOD (e.g., jaundice, rapid weight gain, ascites, hepatomegaly).
* **Hematologic:** Complete blood counts (CBC) frequently during therapy to monitor marrow recovery.
* **Cardiac:** Baseline and periodic ECG monitoring, especially if concurrent with other QT-prolonging drugs.
* **Infusion:** Monitor vital signs throughout the 2-hour infusion window.
## Clinical Pearls
* **Pre-medication:** Mandatory. Administer corticosteroids, antihistamines, and antipyretics 1 hour prior to each infusion to mitigate infusion-related reactions.
* **VOD Risk:** The risk of VOD is significantly increased in patients undergoing hematopoietic stem cell transplantation (HSCT) either pre- or post-Mylotarg. Coordination with the transplant team is critical.
* **Handling:** Must be protected from light at all times; use light-protective shielding during preparation and infusion.
* **Preparation:** Must be reconstituted and diluted carefully using aseptic techniques; do not shake or agitate vials.
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*Disclaimer: This information is for educational purposes only. Mylotarg dosing and administration protocols are complex and highly dependent on patient-specific factors, local institutional guidelines, and clinical trial indications. Always verify current prescribing information in the official FDA-approved package insert or local drug formulary before administration.*
