Regression of lymphoma xenografts after radioimmunotherapy comparing pretargeted anti-CD45 (BC8) and anti-CD20 1F5 antibodies.

Athymic BALB/c mice bearing Ramos lymphoma xenografts were injected intraperitoneally with 1.4 nmol BC8-SA (A-C) or 1F5-SA (D-F), followed 20 hours later by 5.8 nmol clearing agent and 2 hours after that with 800 (A, D), 400 (B, E), or 200 (C, F) μCi⁹⁰Y-DOTA-biotin. Control mice bearing xenograft tumors were treated with 800 μCi (29.6 MBq) ⁹⁰Y-DOTA-biotin alone (♦, G) or pretargeted NRLU-10-SA followed by 800 μCi (29.6 MBq)⁹⁰Y-DOTA-biotin (×; H), or they were untreated (⋄, I). All mice treated with pretargeted BC8-SA are represented by closed triangles (▴), with the exception of 2 mice that had no tumor regression, (▵; C). Mice treated with pretargeted 1F5-SA are represented with open circles (○), except for 1 mouse that had no tumor regression (●, E). Mice that exhibited exponential tumor growth are depicted on a logarithmic scale (C, E-I). Each data point represents an individual animal. The numbers of mice that achieved complete xenograft regression (CR) are indicated relative to the number of mice in each treatment group.