title: The pharmacokinetics of ¹³¹I-rituximab in a patient with CD20 positive non-Hodgkin Lymphoma: evaluation of the effect of radioiodination on the biological properties of rituximab.
abstract: OBJECTIVE
  To report the pharmacokinetics of ¹³¹I-rituximab a patient with a CD20 positive non-Hodgkin Lymphoma who has received ¹³¹I-rituximab as consolidation treatment after remission induction and to evaluate the effect of radioiodination on the biological properties of rituximab.
  
  
  RESULTS
  The patient was a 65-year-old male with a relapsed CD20 positive follicular non-Hodgkin Lymphoma. After induction therapy the patient was in partial remission. Following administration of a diagnostic dose of 185 MBq ¹³¹I-rituximab, remaining lesions were identified on the wholebody scans. The patient then received a therapeutic dose of 1000 MBq ¹³¹I-rituximab. The uptake by the tumor in the right axilla was 0.17-0.21% of the injected dose. The calculated biological half-life of ¹³¹I-rituximab was 684 hrs. This biological half-life corresponded well with the half-life of unlabeled rituximab which was approximately 720 hrs.
  
  
  CONCLUSIONS
  Even though radioiodination of rituximab results in a reduced binding capacity, whole body scans demonstrated localization of ¹³¹I-rituximab in the tumor area. This observation supports the specific targeting of ¹³¹I-rituximab. The half-life of ¹³¹I-rituximab corresponded to the half-life of unlabeled rituximab. Hence, the pharmacokinetics of ¹³¹ I-rituximab was not relevantly affected by the radioiodination process.
authors.affiliation: Department of Pharmacy and Pharmacology, The Netherlands Cancer Institute/Slotervaart Hospital, Amsterdam, The Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: Tran
authors.forename: J W
authors.initials: JW
authors.lastname: Baars
authors.forename: J P
authors.initials: JP
authors.lastname: de Boer
authors.forename: C A
authors.initials: CA
authors.lastname: Hoefnagel
authors.forename: J H
authors.initials: JH
authors.lastname: Beijnen
authors.forename: A D R
authors.initials: AD
authors.lastname: Huitema
mesh_terms: D000368:Aged; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000493:pharmacokinetics / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived / Q000276:immunology / Q000493:pharmacokinetics / Q000627:therapeutic use*; D018951:Antigens, CD20 / Q000096:biosynthesis / Q000276:immunology; D000970:Antineoplastic Agents / Q000276:immunology / Q000493:pharmacokinetics / Q000627:therapeutic use*; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D004334:Drug Administration Schedule; D006207:Half-Life; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D007553:Isotope Labeling; D008228:Lymphoma, Non-Hodgkin / Q000175:diagnosis / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D049268:Positron-Emission Tomography / Q000379:methods*; D016499:Radioimmunotherapy / Q000379:methods*; D012074:Remission Induction / Q000379:methods; D000069283:Rituximab; D055502:Secondary Prevention; D014018:Tissue Distribution; D016896:Treatment Outcome; D051598:Whole Body Imaging
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D007457:Iodine Radioisotopes; D000069283:Rituximab; C507388:131I-rituximab