CD47 is a widely expressed cell surface protein that functions as a regulator of phagocytosis mediated by cells of the innate immune system, such as macrophages and dendritic cells. CD47 serves as the ligand for a receptor on these innate immune cells, SIRP-alpha, which in turn delivers an inhibitory signal for phagocytosis. We previously found increased expression of CD47 on primary human acute myeloid leukemia (AML) stem cells, and demonstrated that blocking monoclonal antibodies directed against CD47 enabled the phagocytosis and elimination of AML, non-Hodgkin’s lymphoma (NHL), and many solid tumors in xenograft models. Here, we report the development of a humanized anti-CD47 antibody with potent efficacy and favorable toxicokinetic properties as a candidate therapeutic. A novel monoclonal anti-human CD47 antibody, 5F9, was generated, and antibody humanization was carried out by grafting its complementarity determining regions (CDRs) onto a human IgG4 format. The resulting humanized 5F9 antibody (Hu5F9-G4) bound monomeric human CD47 with an 8 nM affinity. Hu5F9-G4 induced potent macrophage-mediated phagocytosis of primary human AML cells in vitro and completely eradicated human AML in vivo, leading to long-term disease-free survival of patient-derived xenografts. Moreover, Hu5F9-G4 synergized with rituximab to eliminate NHL engraftment and cure xenografted mice. Finally, toxicokinetic studies in non-human primates showed that Hu5F9-G4 could be safely administered intravenously at doses able to achieve potentially therapeutic serum levels. Thus, Hu5F9-G4 is actively being developed for and has been entered into clinical trials in patients with AML and solid tumors (ClinicalTrials.gov identifier: NCT02216409).

Anti-CD47 antibody is effective for treating malignant pediatric brain tumors without detectable toxicity in patient-derived xenograft models.

I. The characteristics of prenatal spontaneous activity of rat fetuses of 16 through 20 days of gestation, and the development of responses to cutaneous stimulation are discussed and tabulated. In early fetuses of 16 and 17 days, only few activity bursts occur between long intervals of inactivity. The frequency of activity bursts increases greatly at day 18 and attains a peak at this stage, whereupon it declines to a lower level from day 19 through term. 2. Qualitatively, the movements appear to be unintegrated. Three types of activity have been distinguished: Total, generalized or mass movements, when all parts that are capable of movements participate; regional when only one body region such as the head and forelimbs are in motion, and local movements of single parts. In the earliest stage, only head and forelimb movements are observed. There is a gradual extension of motility in rostro-caudal and proximodistal direction, but there are exceptions to this rule. The movements in the rat fetus seem to be more smooth compared with those of the chick embryo where the movements are more jerky. 3. Our recordings show that no clear, or one-to-one correlation exists between fetal activity and uterine contractions. Amnion contractions do not occur in the rat fetus. 4. The first evoked responses in the rat fetus are interpreted as an incipient total or regional pattern. In later stages of development, discrete, low-amplitude unintegrated local responses are identifiable. At 17 and 18 days the local responses are frequently combined with regional and total mass body movements, but by day 19, total movements are less frequently elicited, and the local responses are more complex, resembling mature and fully integrated action patterns. The conclusion is made that in the rat fetus local complex patterns are built up from less complex units. 5. Spontaneous motility in other mammalian embryos and the origin of integrated specialized local action patterns are discussed in relation to the development of the structure and organization of the spinal cord.

Agents that block the anti-phagocytic signal CD47 can synergize with pro-phagocytic anti-tumor antigen antibodies to potently eliminate tumors. While CD47 is overexpressed on cancer cells, its expression in many normal tissues may create an 'antigen sink' that could minimize the therapeutic efficacy of CD47 blocking agents. Here, we report development of bispecific antibodies (BsAbs) that co-target CD47 and CD20, a therapeutic target for non-Hodgkin lymphoma (NHL), that have reduced affinity for CD47 relative to the parental antibody, but retain strong binding to CD20. These characteristics facilitate selective binding of BsAbs to tumor cells, leading to phagocytosis. Treatment of human NHL-engrafted mice with BsAbs reduced lymphoma burden and extended survival while recapitulating the synergistic efficacy of anti-CD47 and anti-CD20 combination therapy. These findings serve as proof of principle for BsAb targeting of CD47 with tumor-associated antigens as a viable strategy to induce selective phagocytosis of tumor cells and recapitulate the synergy of combination antibody therapy. This approach may be broadly applied to cancer to add a CD47 blocking component to existing antibody therapies.