Human Anti-CD22 Recombinant Antibody (clone RFB4-PE38)

Leucine incorporation is expressed as a percentage of cpm incorporated by control cells incubated without immunotoxin. (○), CA46; (▵), JD-38; (+), Raji; (▪), Namalwa; (•), Daudi; (▴), HUT102. Data are representative of at least three trials for each cell line.

Mansfield, E., Amlot, P., Pastan, I., & FitzGerald, D. J. (1997). Recombinant RFB4 immunotoxins exhibit potent cytotoxic activity for CD22-bearing cells and tumors. Blood, The Journal of the American Society of Hematology, 90(5), 2020-2026.

Whole antibody and recombinant immunotoxin were used to compete for binding of trace amounts of 125I-labeled RFB4 IgG. Counts competed are expressed as a percentage of counts from cells that were incubated without any competitor. (□), RFB4 IgG; (▴), RFB4(dsFv)PE38.

Mansfield, E., Amlot, P., Pastan, I., & FitzGerald, D. J. (1997). Recombinant RFB4 immunotoxins exhibit potent cytotoxic activity for CD22-bearing cells and tumors. Blood, The Journal of the American Society of Hematology, 90(5), 2020-2026.

Athymic nude mice irradiated on day −3 were inoculated with 107 CA46 cells on day 0. Beginning on day 1, injections of 5, 2, or 1 μg RFB4(dsFv)PE38 or PBS/0.2% BSA were given every day for four doses. Tumor growth was monitored by measuring tumor volume and is expressed as the average tumor volume of each group. Control mice were killed before the end of the 21-day observation period because their tumor volumes would have exceeded humane limits. (□), 5 μg; (▴), 2 μg; (○), 1 μg; (▪), PBS/0.2% BSA diluent control. Data are from one of two experiments that gave similar results.

Mansfield, E., Amlot, P., Pastan, I., & FitzGerald, D. J. (1997). Recombinant RFB4 immunotoxins exhibit potent cytotoxic activity for CD22-bearing cells and tumors. Blood, The Journal of the American Society of Hematology, 90(5), 2020-2026.

CD22 was expressed by primary patient blasts. Anti-CD22 antibody binding capacity per cell quantified in 54 primary patient samples revealed an average CD22 density of 451 - 16,523 sites per cell (median, 4,062).

Wayne, A. S., Kreitman, R. J., Findley, H. W., Lew, G., Delbrook, C., Steinberg, S. M., ... & Pastan, I. (2010). Anti-CD22 immunotoxin RFB4 (dsFv)-PE38 (BL22) for CD22-positive hematologic malignancies of childhood: preclinical studies and phase I clinical trial. Clinical Cancer Research, 16(6), 1894-1903.

Cycle 1 BL22 clearance correlated with the absolute peripheral blood blast count (Spearman correlation r = 0.73, 95% confidence interval, 0.45 - 0.88; p < 0.0001)

Wayne, A. S., Kreitman, R. J., Findley, H. W., Lew, G., Delbrook, C., Steinberg, S. M., ... & Pastan, I. (2010). Anti-CD22 immunotoxin RFB4 (dsFv)-PE38 (BL22) for CD22-positive hematologic malignancies of childhood: preclinical studies and phase I clinical trial. Clinical Cancer Research, 16(6), 1894-1903.

Bone marrow biopsies reveal decrease in blast infiltration and increase in normal hematopoietic precursors. TdT (terminal deoxynucleotidyl transferase) immunohistochemistry (blasts stain brown). (Subject #20)

Wayne, A. S., Kreitman, R. J., Findley, H. W., Lew, G., Delbrook, C., Steinberg, S. M., ... & Pastan, I. (2010). Anti-CD22 immunotoxin RFB4 (dsFv)-PE38 (BL22) for CD22-positive hematologic malignancies of childhood: preclinical studies and phase I clinical trial. Clinical Cancer Research, 16(6), 1894-1903.