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VARIOUS › THERAPEUTIC RADIOPHARMACEUTICALS › OTHER THERAPEUTIC RADIOPHARMACEUTICALS › Iodine (131I) compounds
tositumomab/iodine (131I) tositumomab
V10XA53
Forms & Strengths
- Tositumomab: 35 mg/mL in 14 mL single-use vials
- Iodine-131 tositumomab: Radioimmunoconjugate, custom activity per patient dose (approx. 611 MBq / 16.5 mCi Iodine-131 and 35 mg tositumomab)
Adult Dosing
- Dosimetric step: 450 mg tositumomab IV over 60 minutes followed by 375 MBq (10 mCi) Iodine-131 tositumomab IV over 20 minutes on Day 0
- Therapeutic step: 450 mg tositumomab IV over 4 hours followed by Iodine-131 tositumomab delivering 75 cGy total body irradiation IV over 20 minutes, administered 7-14 days after dosimetric step
- Pre-medication: Acetaminophen 650 mg and diphenhydramine 50 mg PO administered 30 minutes prior to infusion
Pediatric Dosing
- Safety and effectiveness in pediatric patients have not been established
Indications
- Treatment of patients with relapsed or refractory low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma, including patients with rituximab-refractory disease
Mechanism of Action
- Monoclonal antibody (tositumomab) directed against the CD20 antigen expressed on the surface of normal and malignant B-lymphocytes
- Radiolabeled with Iodine-131, delivering beta radiation directly to the target antigen-bearing cells and neighboring tumor cells via cross-fire effect
Contraindications
- Severe hypersensitivity to murine proteins or any component of the radiolabeled or unlabeled tositumomab
- Pregnancy and lactation due to severe risks of fetal harm and radiation exposure
- Patients with >25% lymphoma marrow involvement and/or impaired bone marrow reserve (platelets <100,000/mm3, neutrophils <1,500/mm3)
Adverse Reactions
- Severe and prolonged cytopenias (thrombocytopenia, neutropenia, anemia)
- Infusion reactions (fever, chills, rigors, hypotension, dyspnea, nausea)
- Secondary malignancies including myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML)
- Serious infections and opportunistic infections
- Hypothyroidism
Drug Interactions
- Myelosuppressive agents: Concurrent use may increase severity and duration of bone marrow suppression
- Hematopoietic growth factors: Avoid use within 2 weeks prior to or during treatment due to risk of increased marrow uptake and toxicity
- Drugs altering thyroid function: Potassium iodide solutions must be administered to block thyroid uptake of radioactive iodine
Curated Content: Needs Vetting Before Put to Clinical Use