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# Mylotarg (gemtuzumab ozogamicin)
## Overview
Mylotarg is a CD33-directed antibody-drug conjugate (ADC). It consists of a humanized anti-CD33 monoclonal antibody covalently linked to calicheamicin, a potent cytotoxic antitumor antibiotic.
## Primary Indications
* Newly diagnosed CD33-positive acute myeloid leukemia (AML).
* Relapsed or refractory CD33-positive AML in adults and pediatric patients aged 2 years and older.
## Adult Dosing
* **Newly diagnosed AML (combination therapy):** 3 mg/m² (up to a maximum dose of 4.5 mg) on days 1, 4, and 7 in combination with daunorubicin and cytarabine.
* **Newly diagnosed AML (monotherapy):** 6 mg/m² on day 1, followed by 3 mg/m² on day 8.
* **Relapsed/Refractory AML:** 3 mg/m² (up to a maximum dose of 4.5 mg) on days 1, 4, and 7.
## Pediatric Dosing
* **Patients ≥ 2 years:** Dosing is typically BSA-based (3 mg/m² for relapsed/refractory or combination regimens). Follow institutional protocols for weight-based adjustments if BSA calculation is not provided in specific clinical trial settings. Doses should not exceed the calculated BSA-based amount matching the adult maximum of 4.5 mg.
## Dose Adjustments
* **Hepatotoxicity:** If total bilirubin > 2x ULN, or AST/ALT > 2.5x ULN, hold treatment until recovery. Permanently discontinue if severe veno-occlusive disease (VOD) occurs.
* **Hematologic Toxicity:** Monitor for prolonged myelosuppression. Dose adjustments are largely protocol-driven based on neutrophil and platelet recovery.
## Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin or any component of the formulation.
* Prior history of VOD/sinusoidal obstruction syndrome (SOS).
## Adverse Effects
* **Hepatotoxicity:** Risk of severe and fatal VOD/SOS, specifically post-hematopoietic stem cell transplant (HSCT).
* **Infusion-related reactions:** Including anaphylaxis, hypotension, and dyspnea.
* **Myelosuppression:** Profound neutropenia, thrombocytopenia, and anemia.
* **Infection:** Elevated risk of opportunistic infections due to severe immunosuppression.
* **Hemorrhage:** Associated with thrombocytopenia.
## Key Drug Interactions
* **Hepatotoxic agents:** Use with extreme caution as they may increase the risk of VOD.
* **CYP-inducing/inhibiting agents:** Gemtuzumab ozogamicin is not primary metabolized by CYP enzymes; however, avoid concurrent medications that cause significant liver stress.
* **Live vaccines:** Avoid administration due to profound immunosuppression.
## Monitoring
* **Hepatic Profile:** Baseline and periodic monitoring of ALT, AST, total bilirubin, and alkaline phosphatase. Monitor bilirubin daily during the post-transplant period for signs of VOD.
* **CBC:** Monitor blood counts frequently (daily prior to each dose and throughout therapy) for cytopenias.
* **Infusion monitoring:** Observe for at least 1 hour post-infusion for hypersensitivity.
## Clinical Pearls
* **Pre-medication:** Administer corticosteroids, antihistamines, and acetaminophen 1 hour prior to infusion to attenuate infusion-related reactions.
* **Handling:** Mylotarg is a cytotoxic agent. Ensure safe handling procedures (chemotherapy precautions) are followed during reconstitution and administration.
* **VOD Risk:** The risk of VOD is highest in patients who undergo HSCT post-treatment or who have had prior HSCT. Monitor closely for weight gain, hepatomegaly, and ascites.
* **Note:** Exact dosing and timing may vary based on specific induction/consolidation protocols (e.g., AAML0531 or local institutional guidelines). Always refer to the specific clinical trial or protocol guidelines.
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*Disclaimer: This information is for educational purposes only. Clinical practice guidelines change frequently. Always verify current prescribing information, institutional protocols, and FDA-approved labeling before administering cytotoxic oncological therapies.*
