JSP191 Antibody Conditioning Regimen in MDS/AML Subjects Undergoing Allogenic Hematopoietic Stem Cell Transplantation

This is a Phase 1a/b study to evaluate the safety and tolerability of an antibody conditioning regimen known as JSP191, in combination with low dose radiation and fludarabine in subjects with Myelodysplastic Syndrome (MDS) or Acute Myeloid Leukemia (AML) undergoing allogenic blood stem cell transplantation. Blood Stem Cell transplantation offers the only potentially curative therapy for many forms of Acute Myeloid Leukemia (AML) and for Myelodysplastic Syndrome (MDS). While standard of care conditioning regimens given prior to blood Stem Cell transplantation, such as standard TBI/Flu conditioning are well tolerated, they are associated with increased rates of relapse due to persistence of disease causing Hematopoietic Stem Cells and insufficient graft versus leukemia effect. The biological conditioning regimen JSP191 is an antibody that binds to CD117. CD117 is the receptor for Stem Cell Factor on blood forming cells. CD117 binding to Stem Cell Factor is critical for survival and maintenance of blood forming stem cells. The binding of JSP191 to CD117 blocks CD117 from binding to Stem Cell Factor on blood forming stem cells. In the absence of CD117/Stem Cell Factor binding, hematopoietic stem cells that are currently occupying the bone marrow niches in MDS/AML patients are depleted. This study will investigate the safety and tolerability of adding JSP191 (an anti-CD117 monoclonal antibody therapy) to standard TBI/Flu conditioning regimen in adults with AML and MDS undergoing hematopoietic stem cell transplant.