Therapeutic efficacy of pretargeted RIT (PRIT) compared with conventional RIT in athymic mice bearing Ramos Burkitt lymphoma xenografts. PRIT mice were injected intravenously via tail vein with 300 μg of either (A) anti-CD20 1F5-SA, (B) anti–HLA-DR Lym-1-SA, (C) anti-HD22 HD39-SA, (D) control HB8181-SA, or (F) a combination of the 3 Ab-SA conjugates followed 20 hours later with 50 μg CA, and 4 hours later with 800 μCi (29.6 MBq) ⁹⁰Y-DOTA-biotin. Mice treated with conventional RIT received either 200 μCi (7.4 MBq) or 300 μCi (11.1 MBq) of either ⁹⁰Y-labeled (A) 1F5-SA, (B) Lym-1-SA, (C) HD39-SA, (D) HB8181, or (E) a combination of the 3 directly labeled Abs injected intravenously via tail vein. Untreated mice did not receive any therapy. Tumor growth is reported as percentage of initial tumor volume (y-axis) measured over time (x-axis). When mice required killing due to tumor progression or severe toxicity, the final tumor volume was carried through until the last mouse in the group died or 100 days after treatment was reached. Error bars indicate SD.