An efficient, reproducible and fast preparation of 188Re-anti-CD20 for the treatment of non-Hodgkin's lymphoma.
BACKGROUND
Therapies using Y-anti-CD20 or I-anti-CD20 have demonstrated their efficacy in patients with B-cell non-Hodgkin's lymphoma. Re is a radionuclide useful for radioimmunotherapy.


OBJECTIVE
To develop a procedure for efficient labelling of anti-CD20 with Re from lyophilized formulations to achieve high radiochemical yield, high specific activity and preservation of the molecular recognition after a simple kit reconstitution without further purification.


METHODS
Re-anti-CD20 was prepared by a direct labelling method using sodium tartrate as a weak competing ligand. Different lyophilized formulations were prepared to optimize tartrate and stannous chloride concentration, pH and reaction time. To evaluate the biological recognition a comparative study of the in-vitro binding of Re-anti-CD20, I-anti-CD20 (positive control) and Re-anti-CEA (negative control) to normal B lymphocytes was performed. Biodistribution studies in normal mice were accomplished to assess the in-vivo Re-anti-CD20 complex stability.


RESULTS
Re labelled anti-CD20 was obtained with high radiochemical purities (>97%) and high specific activity (0.5-0.7 GBq . mg) 1-1.5 h after addition of sodium perrhenate solution to a kit containing 4.4 muM anti-CD20, 4 mM anhydrous stannous chloride, and 140 mM dihydrate sodium tartrate at pH 4. The binding of Re-anti-CD20 to cells was in the same range as I-anti-CD20 (>80%) and was significantly different to cell binding of Re-anti-CEA (<10%). No evidence of free Re release was found at 2, 4 and 24 h after Re-anti-CD20 administration in mice. Lyophilized kits showed high stability during the storage at 4 degrees C for 6 months.


CONCLUSIONS
Optimal reaction conditions were defined enabling high radiochemical purities of Re-anti-CD20 to be obtained routinely and therefore potentially useful in the treatment of non-Hodgkin's lymphoma.
Ferro-Flores
Guillermina
G
Department of Nuclear Materials, Instituto Nacional de Investigaciones Nucleares, Km. 36.5 Carretera México-Toluca, Ocoyoacac, Estado de Mexico, CP 52045, Mexico. gff@nuclear.inin.mx
Torres-García
Eugenio
E
García-Pedroza
Lourdes
L
Arteaga de Murphy
Consuelo
C
Pedraza-López
Martha
M
Garnica-Garza
Héctor
H
D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D018951:Antigens, CD20; D004353:Drug Evaluation, Preclinical; D007553:Isotope Labeling / Q000379:methods; D008228:Lymphoma, Non-Hodgkin / Q000532:radiotherapy*; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D008807:Mice, Inbred BALB C; D009928:Organ Specificity; D016499:Radioimmunotherapy / Q000379:methods*; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics / Q000627:therapeutic use; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
C527563:188Re-anti-CD20 monoclonal antibody; D000911:Antibodies, Monoclonal; D018951:Antigens, CD20; D019275:Radiopharmaceuticals