Novel Approach to Enhance Cord Blood-Mediated Bone Marrow Homing and Engraftment

DESCRIPTION (provided by applicant): Despite significant recent government and private-sector efforts to improve the current state of the art in bone marrow transplants, many patients still suffer from lack of adequate matching bone marrow inventories and from severe treatment-related complications. Key drawbacks to conventional approaches include the major delays in finding compatible donors and precipitation of graft-versus-host disease (GVHD). Clearly, new alternatives are required for patients who need bone marrow transplants. Various sources of hematopoietic stem cells (mobilized peripheral blood, bone marrow and cord blood) have been utilized in bone marrow transplants for decades. While each has its individual limitations, cord blood has seen increase d usage due to its availability and reduced GVHD. However, the slow rate of engraftment observed with cord blood (compared with that for stem cells from other sources) is a severe limitation on its utilization. Studies done to date indicate that this slow rate of engraftment is likely due to the fact that the selectin-mediated interaction between stem cell and endothelial cell needed to tether and roll cells along the endothelial layer is reduced in cord blood-derived stem cells. Experiments from a number o f different laboratories along with our own preliminary data have now shown that this deficit can be overcome by enforced fucosylation (Engraftin) with a short pre-incubation of cord blood with fucosyltransferase and its substrate prior to injection into a nimals This pretreatment has been shown to result in increased engraftment in immune-compromised mice. Homing to the bone marrow is known to involve a number of different yet coordinated steps, starting with selectin-mediated rolling, integrin-mediate adhe sion, extravasation and migration/homing to the marrow niche guided by the chemotactic agent, stromal cell-derived factor (SDF). The response of stem cells to this homing signal from SDF is enhanced by diprotin A (Engrafta)-mediated inhibition of the enzym e, dipeptidylpeptidase IV, which normally metabolizes the SDF. The overall result of pretreatment with Engrafta is increased engraftment in immune-compromised mice. These observations have been documented by at least four independent laboratories, and rece ntly have been documented using human cord blood. Consequently, the goal of this Phase I SBIR project is to prove the feasibility of extending and further delineating the commercial and therapeutic potential of Engraftin and Engrafta by pursuing an innovat ive combination approach. Specifically, we will test for an additive or synergistic effect on engraftment by pretreating ex vivo human MNCs with Engraftin, in combination with Engrafta. Engraftin and Engrafta technologies-exclusively licensed to America St em Cell (ASC)-have both been shown by numerous investigators to enhance the engraftment of cord blood in pre-clinical animal models of bone marrow transplants. PUBLIC HEALTH RELEVENCE: The SBIR project proposed here by America Stem Cell (ASC) is designed t o prove the feasibility of employing the innovative combination of two new, promising technologies that have been shown by a number of independent investigators individually to enhance the engraftment or homing potential of cord blood-derived stem cells. ASC has assembled an expert RandD team to pursue this opportunity to address key drawbacks in our current capabilities in effectively treating patients who require bone marrow transplants. Successful translation of these enhancing technologies into widesp read, commercial clinical use would profoundly improve patient welfare and survival rates, reduce treatment costs, and strengthen the nation's cord blood industry.