Non-genotoxic conditioning regimen for stem cell transplantation

Abstract

The present invention provides a clinically applicable method of stem cell transplantation that facilitates engraftment and reconstitutes immunocompetence of the recipient without requiring radiotherapy or chemotherapy, and without development of GVHD or graft rejection.

1 . A method of providing for stem cell engraftment in a mammalian subject, the method comprising a conditioning regimen that comprises:
 contacting said subject concomitantly with (i) an agent that specifically binds to endogenous stem cells in a targeted tissue and (ii) an agent that blocks interaction between CD47 and SIRPα; in a dose effective to ablate targeted endogenous stem cells from said subject;   contacting said subject with (iii) an agent that induces transient immunosuppression;   introducing a cellular composition comprising exogenous stem cells to said subject following a wash-out period of time sufficient to reduce the serum level of (i) and (ii) to non-toxic levels in the subject;   wherein the exogenous stem cells engraft in the absence of myeloablative conditioning.   
     
     
         2 . The method according to  claim 1 , wherein the targeted tissue is bone marrow and the targeted stem cells are hematopoietic stem cells. 
     
     
         3 . The method of  claim 1 , wherein the exogenous stem cells are autologous or allogeneic relative to the subject. 
     
     
         4 . The method of  claim 1 , wherein the exogenous stem cells are genetically engineered ex vivo. 
     
     
         5 . The method of  claim 1 , wherein said agent that specifically binds to endogenous stem cells in a targeted tissue is a monoclonal antibody specific for c-kit. 
     
     
         6 . The method of  claim 1 , wherein the agent that blocks interaction between CD47 and SIRPα is selected from: a soluble SIRPα polypeptide; an antibody specific for CD47, an antibody specific for SIRPα, and a soluble CD47 polypeptide. 
     
     
         7 . The method of  claim 1 , wherein the agent that induces transient immunosuppression is selected from an agent that inhibits CD40/CD40L activity; mycophenolic acid, cyclosporine A, rapamycin, FK506, and corticosteroids. 
     
     
         8 . The method of  claim 7 , wherein the agent that induces transient immunosuppression is an antibody specific to CD40L. 
     
     
         9 . The method of  claim 8 , wherein the agent that induces transient immunosuppression is administered concomitantly with the exogenous stem cells. 
     
     
         10 . The method of  claim 1 , wherein the subject is an immunocompetent human. 
     
     
         11 . The method of  claim 1 , wherein the subject is haploidentical relative to the exogenous stem cells. 
     
     
         12 . The method of  claim 1 , wherein the exogenous stem cells are administered as a composition of whole bone marrow mononuclear cells. 
     
     
         13 . The method of  claim 1 , wherein the stem cells are MHC matched to the recipient. 
     
     
         14 . The method of  claim 1 , further comprising contacting the subject with (iv) an agent the depletes one or both of T cells and NK cells, wherein the agent (iv) is administered prior to introduction of the exogenous stem cells, and optionally concurrent with the introduction of the exogenous stem cells. 
     
     
         15 . The method of  claim 14 , wherein the subject is HLA-mismatched relative to the exogenous stem cells. 
     
     
         16 . The method of  claim 14 , wherein the cellular composition comprises hematopoietic stem cells selected for CD34 +  expression from bone marrow, cord blood, or peripheral blood. 
     
     
         17 . The method of  claim 16 , wherein the cellular composition comprises at least 50% CD34+ cells. 
     
     
         18 . The method of  claim 14 , wherein the cellular composition comprises hematopoietic stem cells derived from pluripotent cells in vitro. 
     
     
         19 . The method of  claim 14 , wherein the cellular composition comprises at least 10 5  CD34 +  cells/kg of recipient body weight. 
     
     
         20 . The method of  claim 14 , wherein the agent (iv) depletes T cells and NK cells. 
     
     
         21 . The method of  claim 20 , wherein the agent (iv) is an antibody selected from an antibody specific for CD2, CD52, CD45; or anti-thymocyte globulin (ATG). 
     
     
         22 . The method of  claim 14 , wherein an agent (iv) that selectively depletes T cells is selected from an antibody specific for one or more of CD3, CD4, and CD8. 
     
     
         23 . The method of  claim 14 , wherein an agent (iv) that selectively depletes NK cells is selected from an antibody specific for one or more of CD122 and CD56. 
     
     
         24 . A method of providing for stem cell engraftment in a mammalian subject, the method comprising:
 HLA typing a donor and recipient to determine an HLA-matched or HLA-mismatched pair;   obtaining hematopoietic cells from the donor comprising CD34 +  hematopoietic stem and progenitor cells (HSPC) and optionally isolating HSPC of the desired phenotype;   formulating an effective dose of the HSPC cellular composition;   selecting a set of agents for non-genotoxic conditioning regimen on the recipient prior to infusion of the hematopoietic cells, based on the number of donor cells administered to the recipient; the purity of the donor cells; the degree of major histocompatibility mismatch between donor and recipient; and the immune status of the recipient;   administering the set of agents for non-genotoxic conditioning;   infusing the hematopoietic cells; and   monitoring the recipient for hematopoietic stem cell engraftment.