LABELLING AND BIOLOGICAL EVALUATION OF ANTI-CD20 FOR TREATMENT OF NON-HODGKIN'S LYMPHOMA

摘要

A radiopharmaceutical based on the use of Mab anti-CD20 labelled with ~(131)I and ~(188)Re is proposed for the treatment of non-Hodgkin's lymphoma. The antibody has been successfully used alone as well as associated with cytotoxic drugs, therefore encouraging the present research. The radionuclides were chosen on the basis of their decay properties and availability. Labelling techniques employed were previously used with other monoclonals. Oxidation with chloramine-T was used for ~(131)I labelling and SnF_2·2H_2O as the reducing agent for ~(188)Re. Non-specific precipitation and Sephadex purification were used for primary control and extraction. Quality control procedures including thin layer as well as high performance liquid chromatography were undertaken. Biodistribution in mice as well as affinity characteristics in a source rich in CD20 antigens were also studied. Stability over time was estimated. It was concluded that the labelling of anti-CD20 with β emitters of therapeutic interest, in this case ~(131)I and ~(188)Re, gave reliable results by simple and efficient methodologies, yielding products compatible with clinical radioimmunotherapy. Quality control methods for the evaluation of radiochemical purity showed good reproducibility with short bench time. Immunoaffinity studies showed binding dependency on membrane antigen concentration and good specificity of binding was demonstrated by inhibition with unlabelled anti-CD20. Use of membranes, stable at -80°C for more than 6 months instead of concentrated short lived leucocytes, has shown excellent reproducibility and therefore they are convenient at production centres distant from blood banks. Biodistributions were useful to determine the normal pattern and kinetics of uptake and excretion.