RT Journal Article
SR Electronic
T1 Relative Therapeutic Efficacy of <sup>125</sup>I- and <sup>131</sup>I-Labeled Monoclonal Antibody A33 in a Human Colon Cancer Xenograft
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1251
OP 1256
VO 42
IS 8
A1 Els C. Barendswaard
A1 John L. Humm
A1 Joseph A. O’Donoghue
A1 George Sgouros
A1 Ronald D. Finn
A1 Andrew M. Scott
A1 Steven M. Larson
A1 Sydney Welt
YR 2001
UL http://jnm.snmjournals.org/content/42/8/1251.abstract
AB A33, a monoclonal antibody that targets colon carcinomas, was labeled with 125I or 131I and the relative therapeutic efficacy of the 2 radiolabeled species was compared in a human colon cancer xenograft system. Methods: Nude mice bearing human SW1222 colon carcinoma xenografts were administered escalating activities of 125I-A33 (9.25–148 MBq) or 131I-A33 (0.925–18.5 MBq), 125I- and 131I-labeled control antibodies, unlabeled antibody, or no antibody. The effects of treatment were assessed using the endpoints of tumor growth delay and cure. Results: Tumor growth delay increased with administered activity for all radiolabeled antibodies. Approximately 4.5 times more activity was required for 125I-A33 to produce therapeutic effects that were equivalent to those of 131I-A33. This ratio was approximately 7 for a nonspecific, noninternalizing isotype-matched, radiolabeled control antibody. Unlabeled A33 antibody had no effect on tumor growth. Approximately 10 times more activity of 125I-A33 produced toxicity similar to that of 131I-A33, and this ratio fell to approximately 6 for radiolabeled control antibody. Conclusion: Treatment with 125I-A33 resulted in a relative therapeutic gain of approximately 2 compared with 131I-A33 in this experimental system.