Figure 5. A Monoclonal Antibody Directed Against Human CD47 Depletes AML In Vivo.

A–D. Newborn NOG mice were transplanted with AML LSC, and 8–12 weeks later, peripheral blood (C,D) and bone marrow (E,F) were analyzed for baseline engraftment prior to treatment with anti-CD47 (B6H12.2) or control IgG antibody (Day 0). Mice were treated with daily 100 microgram intraperitoneal injections for 14 days, at the end of which, they were sacrificed and peripheral blood and bone marrow were analyzed for the percentage of human CD45+CD33+ leukemia. (A) Pre- and post-treatment human leukemic chimerism in the peripheral blood from representative anti-CD47 antibody and control IgG-treated mice as determined by flow cytometry. (B) Summary of human leukemic chimerism in the peripheral blood assessed on multiple days during the course of treatment demonstrated elimination of leukemia in anti-CD47 antibody treated mice compared to control IgG treatment (p=0.007). (C) Pre- and post-treatment human leukemic chimerism in the bone marrow from representative anti-CD47 antibody or control IgG-treated mice as determined by flow cytometry. (D) Summary of human leukemic chimerism in the bone marrow on day 14 relative to day 0 demonstrated a dramatic reduction in leukemic burden in anti-CD47 antibody treated mice compared to control IgG treatment (p=0.006).

E. H&E sections of representative mouse bone marrow cavities from mice engrafted with SU004 AML LSC post-treatment with either control IgG (panels 1,2) or anti-CD47 antibody (panels 4,5). IgG-treated marrows were packed with monomorphic leukemic blasts, while anti-CD47-treated marrows were hypocellular, demonstrating elimination of the human leukemia. In some anti-CD47 antibody-treated mice that contained residual leukemia, macrophages were detected containing phagocytosed pyknotic cells (panels 3,6 arrows).