ibritumomab

Ibritumomab tiuxetan is a radiolabeled monoclonal antibody that targets the CD20 antigen on B lymphocytes. It is used as a form of radioimmunotherapy for certain CD20-positive non-Hodgkin lymphomas. The product consists of the anti-CD20 antibody ibritumomab linked to tiuxetan, a chelator that binds the radioactive isotope yttrium-90, delivering targeted radiation to CD20-expressing cells.

Mechanism of action involves the antibody binding to CD20 on B cells, followed by the yttrium-90 radiation emitted by the chelated metal. The localized beta radiation damages the DNA of the malignant B cells and nearby tumor-associated cells. In addition to the direct cytotoxic effect of radiation, the antibody can contribute to B-cell depletion through immune mechanisms such as antibody-dependent cellular cytotoxicity, though the radiolabeled component is the primary therapeutic modality in this product.

Administration typically follows a two-step regimen. Patients usually receive rituximab to deplete circulating B cells, after which ibritumomab tiuxetan is given as a single intravenous dose. The activity is dose-adjusted based on body weight, and the treatment is ordinarily conducted in specialized facilities with radiopharmacy and radiation-safety provisions. Dosing and scheduling may vary by indication and regional guidelines.

Indications center on adults with relapsed or refractory CD20-positive non-Hodgkin lymphomas, often in follicular lymphoma or other CD20-positive subtypes. The regimen is generally considered after prior therapies have failed or are unsuitable.

Adverse effects most commonly include hematologic toxicity (neutropenia, thrombocytopenia), infection risk, fatigue, nausea, and infusion-related reactions. Radiation exposure necessitates adherence to safety guidelines to protect caregivers and others. Contraindications include significant marrow suppression, active infection, pregnancy, and breastfeeding.