In vitro characterization of (177)Lu-radiolabelled chimeric anti-CD20 monoclonal antibody and a preliminary dosimetry study.
OBJECTIVE
(131)I- and (90)Y-labelled anti-CD20 antibodies have been shown to be effective in the treatment of low-grade, B-cell non-Hodgkin's lymphoma (NHL). However, the most appropriate radionuclide in terms of high efficiency and low toxicity has not yet been established. In this study we evaluated an immunoconjugate formed by the anti-CD20 antibody rituximab and the chelator DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid). DOTA-rituximab was prepared as a kit formulation and can be labelled in a short time (<20 min) with either (177)Lu or (90)Y.


METHODS
Immunoconjugates with different numbers of DOTA molecules per rituximab were prepared using p-SCN-Bz-DOTA. In vitro immunoreactivity and stability were tested and preliminary dosimetric results were acquired in two patients.


RESULTS
The immunological binding properties of DOTA-rituximab to the CD20 antigen were found to be retained after conjugation with up to four chelators. The labelled product was stable against a 10(5) times excess of diethylenetriaminepentaacetic acid (DTPA, 37 degrees C, 7 days). Two patients with relapsed NHL were treated with 740 MBq/m(2) body surface (177)Lu-DOTA-rituximab. Scintigraphic images showed specific uptake at tumour sites and acceptable dosimetric results. The mean whole-body dose was found to be 314 mGy. The administration of (177)Lu-DOTA-rituximab was tolerated well.


CONCLUSIONS
Our results show that DOTA-rituximab (4:1) can be labelled with (177)Lu with sufficient stability while the immunoconjugate retains its immunoreactivity. (177)Lu-DOTA-rituximab is an interesting, well-tolerated radiolabelled antibody with clinical activity in a low dose range, and provides an approach to the efficient treatment with few side effects for patients with relapsed NHL.
Institute of Nuclear Medicine, University Hospital Basel, Basel, Switzerland.
Flavio
F
Forrer
Jianhua
J
Chen
Melpomeni
M
Fani
Pia
P
Powell
Andreas
A
Lohri
Jan
J
Müller-Brand
Gerhard
G
Moldenhauer
Helmut R
HR
Maecke
D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000276:immunology*; D002460:Cell Line; D002614:Chelating Agents / Q000737:chemistry; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry; D006801:Humans; D018796:Immunoconjugates / Q000494:pharmacology*; D008187:Lutetium; D008224:Lymphoma, Follicular / Q000532:radiotherapy; D008228:Lymphoma, Non-Hodgkin / Q000532:radiotherapy; D051379:Mice; D010865:Pilot Projects; D016499:Radioimmunotherapy; D011868:Radioisotopes; D019275:Radiopharmaceuticals / Q000494:pharmacology*; D000069283:Rituximab; D015021:Yttrium Radioisotopes
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D002614:Chelating Agents; D006573:Heterocyclic Compounds, 1-Ring; D018796:Immunoconjugates; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D015021:Yttrium Radioisotopes; C071349:1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid; D000069283:Rituximab; D008187:Lutetium