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## Mylotarg (gemtuzumab ozogamicin)
### Overview
Mylotarg is an antibody-drug conjugate consisting of a humanized anti-CD33 antibody linked to the cytotoxic agent calicheamicin. It targets CD33-expressing myeloid leukemia cells.
### Primary Indications
* Treatment of newly diagnosed acute myeloid leukemia (AML) in adults who are not eligible for intensive induction chemotherapy.
* Treatment of relapsed or refractory AML in adults.
### Adult Dosing
**Newly Diagnosed AML (not eligible for intensive induction chemotherapy):**
* **Cycle 1:** 3 mg/m² on days 1, 4, and 7.
* **Cycle 2:** 3 mg/m² on day 1.
* **Cycle 3:** 3 mg/m² on day 1, if achieved hematologic remission.
**Relapsed or Refractory AML:**
* **First course:** 6 mg/m² on day 1.
* **Second course:** 3 mg/m² on day 1, administered if hematologic remission is achieved.
* **Maximum dose:** 6 mg/m² per administration.
### Pediatric Dosing
There is no established pediatric dosing. Use in pediatric patients is not recommended.
### Dose Adjustments
* **Hepatic Impairment:**
* **Total Bilirubin 1.5 to 3 times the upper limit of normal (ULN):** Reduce dose by 50%.
* **Total Bilirubin > 3 times ULN:** Mylotarg is contraindicated.
* **Myelosuppression:** Delay dosing and consider dose reduction based on the nadir of ANC and platelets and recovery. Protocol-specific guidance should be followed.
### Contraindications
* Known hypersensitivity to gemtuzumab ozogamicin, its components, or calicheamicin derivatives.
* Active unsafe bleeding.
* Total Bilirubin > 3 times ULN.
### Adverse Effects
* **Most Common:** Febrile neutropenia, nausea, vomiting, diarrhea, abdominal pain, mucositis, headache, pyrexia, fatigue, rash, and cough.
* **Serious:**
* **Hepatotoxicity:** Veno-occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS) is a significant risk, especially with prior stem cell transplant or hepatic impairment.
* **Hemorrhage:** Including severe or life-threatening bleeding events.
* **Infusion-related reactions:** Can occur during or after infusion.
* **Myelosuppression:** Leading to neutropenia, thrombocytopenia, and anemia.
* **Embryo-fetal toxicity.**
### Key Drug Interactions
* **Potent CYP3A4 Inhibitors/Inducers:** Monitor for potential effects on the antibody component, though direct metabolism of the antibody is unlikely to be significant.
* **Anticoagulants and Antiplatelet Agents:** Use with caution due to increased risk of bleeding.
* **Live Vaccines:** Avoid due to immunosuppression.
### Monitoring
* **Complete Blood Count (CBC) with differential and platelet count:** Prior to each dose, and as clinically indicated. Monitor for myelosuppression.
* **Liver Function Tests (LFTs):** Including bilirubin and transaminases, prior to each dose and as clinically indicated. Monitor for hepatotoxicity.
* **Signs and symptoms of bleeding:** Monitor closely, especially in patients with pre-existing bleeding disorders or those receiving anticoagulants.
* **Signs and symptoms of infusion-related reactions:** Monitor during and after infusion.
* **Signs and symptoms of VOD/SOS:** Monitor closely, particularly in high-risk patients.
### Clinical Pearls
* Administer prophylactic antiemetics and antidiarrheals.
* Consider prophylactic antibiotics and growth factors for febrile neutropenia.
* Due to the risk of VOD/SOS, careful patient selection and monitoring are crucial, especially in patients with a history of stem cell transplant.
* The drug carries a boxed warning for hepatotoxicity and hemorrhage.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines, and exercise clinical judgment when making treatment decisions. Dosages and recommendations may vary based on local protocols and individual patient factors.
