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

Targazyme, Inc., Carlsbad CA

Investigators

Abstract

[unreadable] 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 increased 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 of 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 animals 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 adhesion, 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 enzyme, 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 recently 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 innovative 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 Stem 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 to 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 R&D 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 widespread, commercial clinical use would profoundly improve patient welfare and survival rates, reduce treatment costs, and strengthen the nation's cord blood industry. [unreadable] [unreadable] [unreadable]