Comparison of a tetravalent single-chain antibody-streptavidin fusion protein and an antibody-streptavidin chemical conjugate for pretargeted anti-CD20 radioimmunotherapy of B-cell lymphomas by John M. Pagel, Yukang Lin, Nathan Hedin, Anastasia Pantelias, Donald Axworthy, Diane Stone, Don K. Hamlin, D. Scott Wilbur, and Oliver W. Press Blood Volume 108(1):328-336 July 1, 2006 ©2006 by American Society of Hematology

Purification and characterization of the 1F5 (scFv)4SA fusion protein. Purification and characterization of the 1F5 (scFv)4SA fusion protein. SDS-PAGE analysis of unpurified and iminobiotin-purified 1F5 (scFv)4SA with Coomassie Blue staining. The molecular weights in kilodaltons for Mark12 standards (Invitrogen) are indicated on the left (lane 1). Lane 2 contains a crude lysate from a culture of E coli-producing 1F5 (scFv)4SA. Lanes 3 and 4 contain the flow-through and wash fractions, respectively, from an iminobiotin purification column. Lanes 5 and 6 show the iminobiotin-purified FP either without boiling (lane 5) or denatured by boiling for 5 minutes (lane 6). The FP mass (174 kDa) and the monomer (44 kDa) are indicated on the right. John M. Pagel et al. Blood 2006;108:328-336 ©2006 by American Society of Hematology

Pharmacokinetic and blood-clearance studies. Pharmacokinetic and blood-clearance studies. (A) Whole-blood clearance of 1.4 nM (300 μg) 131I-labeled 1F5 Ab-SA chemical conjugate (▿) or 1.4 nM (245 μg) 125I-labeled 1F5 (scFv)4SA, each injected intraperitoneally into athymic BALB/c mice (n = 5/group). (B) The effect of a biotinylated polymeric, N-acetyl-galactosamine-containing CA, on circulating 125I-1F5 (scFv)4SA FP. 125I-1F5 (scFv)4SA (1.4 nM) was injected intraperitoneally into 5 BALB/c athymic mice at time 0 hours. The CA (50 μg; 5.8 nM intraperitoneally) was injected 20 hours after the labeled FP. In each experiment, serial blood samples were obtained from the retro-orbital venous plexus at the times indicated after the injection of each Ab-SA construct and analyzed by gamma counting. Results are representative of 3 experiments. John M. Pagel et al. Blood 2006;108:328-336 ©2006 by American Society of Hematology

Biodistributions of radioactivity in blood and tumors of athymic mice bearing Ramos xenografts who were injected with either 1F5 (scFv)4SA fusion protein, B9E9 (scFv)4SA fusion protein, 1F5 Ab-SA chemical conjugate, CC49 (scFv)4SA fusion protein, or directl... Biodistributions of radioactivity in blood and tumors of athymic mice bearing Ramos xenografts who were injected with either 1F5 (scFv)4SA fusion protein, B9E9 (scFv)4SA fusion protein, 1F5 Ab-SA chemical conjugate, CC49 (scFv)4SA fusion protein, or directly labeled conventional 111In-DOTA-1F5 Ab. Mice in pretargeted groups (A) were injected with 1.4 nM of each unlabeled construct, followed 20 hours later by 5.8 nM CA, and 4 hours after that by 1.2 nM 111In-DOTA-biotin. In the directly labeled group (B), mice were injected with 1.4 nM of conventional trace-labeled 111In-DOTA-1F5 Ab at time 0 hours. Groups of 5 mice were euthanized 24, 48, 96, and 144 hours after injection of radiobiotin or 111In-DOTA-1F5 Ab. The radioactivity in blood and tumors were quantified by gamma counting, corrected for decay, and expressed as the % ID/g of tissue. 1F5 (scFv)4SA fusion protein (•, tumor; ○, blood), B9E9 (scFv)4SA fusion protein (▪, tumor; □, blood), 1F5 Ab-SA chemical conjugate (▾, tumor; ▿, blood), CC49 (scFv)4SA fusion protein (▴, tumor; ▵, blood), directly labeled conventional 111In-DOTA-1F5 Ab (♦, tumor; ⋄, blood). John M. Pagel et al. Blood 2006;108:328-336 ©2006 by American Society of Hematology

Tumor-to-normal organ ratios for conventional directly labeled 111In-DOTA-1F5 Ab or 111In-DOTA biotin pretargeted with B9E9 (scFv)4-SA fusion protein, 1F5 (scFv)4-SA fusion protein, or 1F5 Ab-SA chemical conjugate. Tumor-to-normal organ ratios for conventional directly labeled 111In-DOTA-1F5 Ab or 111In-DOTA biotin pretargeted with B9E9 (scFv)4-SA fusion protein, 1F5 (scFv)4-SA fusion protein, or 1F5 Ab-SA chemical conjugate. Mice were treated as described in Figure 3. Tumor-to-normal organ ratios of administered 111In-DOTA-1F5 or 111In-DOTA biotin are shown for the 24-hour time point after injection of radioactivity. 1F5 (scFv)4SA fusion protein (▦), B9E9 (scFv)4SA fusion protein (▪), 1F5 Ab-SA chemical conjugate (▨), directly labeled conventional 111In-DOTA-1F5 Ab (□). P values represent differences between the 1F5 (scFv)4-SA fusion protein and directly labeled DOTA-1F5 Ab. John M. Pagel et al. Blood 2006;108:328-336 ©2006 by American Society of Hematology

Regression of lymphoma xenografts after PRIT comparing anti-CD20 B9E9 (scFv)4SA fusion protein and 1F5 Ab-SA chemical conjugate. Regression of lymphoma xenografts after PRIT comparing anti-CD20 B9E9 (scFv)4SA fusion protein and 1F5 Ab-SA chemical conjugate. Athymic BALB/c mice bearing Ramos lymphoma xenografts were injected intraperitoneally with either 1.4 nM B9E9 (scFv)4SA (•) or 1F5 Ab-SA (▵), followed 20 hours later by 5.8 nM CA, and 4 hours after that with (A) 200, (B) 400, (C) 800, (D) 1000, or (E) 1200 μCi (7.4, 14.8, 29.6, 37, or 44.4 MBq, respectively) 90Y-DOTA-biotin. Tumor volume curves are truncated at the time of euthanasia of the first mouse in each group. Control mice bearing xenograft tumors were treated with pretargeted CC49 (scFv)4SA (▪). John M. Pagel et al. Blood 2006;108:328-336 ©2006 by American Society of Hematology

Analysis of cumulative survival of mice bearing Ramos lymphoma xenografts treated with PRIT using anti-CD20 B9E9 (scFv)4SA fusion protein and 1F5 Ab-SA chemical conjugate. Analysis of cumulative survival of mice bearing Ramos lymphoma xenografts treated with PRIT using anti-CD20 B9E9 (scFv)4SA fusion protein and 1F5 Ab-SA chemical conjugate. Groups of 10 mice bearing Ramos tumor xenografts were treated as described in Figure 5 and analyzed for survival as a function of time. Treatment groups included mice treated with 1.4 nM of either B9E9 (scFv)4SA, control CC49 (scFv)4SA, or 1F5 Ab-SA, followed 20 hours later by 5.8 nM CA, and 4 hours after that with 200, 400, 800, 1000, or 1200 μCi (7.4, 14.8, 29.6, 37, or 44.4 MBq, respectively) 90Y-DOTA-biotin. Survival curves in this figure correspond to treatment groups designated in Figure 5. John M. Pagel et al. Blood 2006;108:328-336 ©2006 by American Society of Hematology

Regression of lymphoma xenografts after PRIT comparing anti-CD20 1F5 (scFv)4SA fusion protein and 1F5 Ab-SA chemical conjugate. Regression of lymphoma xenografts after PRIT comparing anti-CD20 1F5 (scFv)4SA fusion protein and 1F5 Ab-SA chemical conjugate. Athymic BALB/c mice bearing Ramos lymphoma xenografts were injected intraperitoneally with either 1.4 (⋄) or 2.8 (○) nM 1F5 (scFv)4SA or 1F5 Ab-SA (▪), followed 20 hours later by 5.8 nM CA, and 4 hours after that with (A) 800 or (B) 1200 μCi (29.6 or 44.4 MBq, respectively) 90Y-DOTA-biotin. Control mice bearing xenograft tumors were treated with pretargeted CC49 (scFv)4SA (□). Tumor volume curves though day 60 incorporate the tumor size determined at the time of euthanasia. John M. Pagel et al. Blood 2006;108:328-336 ©2006 by American Society of Hematology

Analysis of cumulative survival of mice bearing Ramos lymphoma xenografts treated with PRIT using anti-CD20 1F5 (scFv)4SA fusion protein and 1F5 Ab-SA chemical conjugate. Analysis of cumulative survival of mice bearing Ramos lymphoma xenografts treated with PRIT using anti-CD20 1F5 (scFv)4SA fusion protein and 1F5 Ab-SA chemical conjugate. Groups of 10 mice bearing approximately 100 mm3Ramos tumor xenografts were treated as described in Figure 7 and analyzed for survival as a function of time. Treatment groups included mice treated with 1.4 (⋄) and 2.8 (○) nM of 1F5 (scFv)4SA, 1.4 nM of control CC49 (scFv)4SA (□), or 1.4 nM of 1F5 Ab-SA chemical conjugate (▪), followed 20 hours later by 5.8 nM CA, and 4 hours after that with (A) 800 or (B) 1200 μCi (29.6 or 44.4 MBq, respectively) 90Y-DOTA-biotin. Survival curves in this figure correspond to treatment groups designated in Figure 7. John M. Pagel et al. Blood 2006;108:328-336 ©2006 by American Society of Hematology