Non-genotoxic conditioning regimen for stem cell transplantation
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 engraftment of HLA-mismatched hematopoietic stem cells in an immunocompetent human subject, the method comprising a conditioning regimen of:
contacting said subject concomitantly with (i) an antibody that specifically binds to CD117 and (ii) an agent that blocks interaction between CD47 and SIRPα; in a dose effective to ablate targeted endogenous hematopoietic stem cells from bone marrow of said subject;
introducing a cellular composition comprising exogenous allogeneic hematopoietic stem cells mismatched at one or more major MHC loci 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, the cellular composition comprising: exogenous hematopoietic stem cells mismatched at one or more major MHC loci; and
concomitantly contacting said subject with (iii) an agent that induces transient immunosuppression, wherein the agent is an anti-CD40L antibody; and
contacting the subject with (iv) an agent the depletes NK cells, wherein the agent (iv) is administered prior to or concurrently with the exogenous stem cells;
wherein the exogenous stem cells engraft in the absence of myeloablative conditioning.
2. 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.
3. The method of claim 1 , wherein the subject is haploidentical relative to the exogenous stem cells.
4. The method of claim 1 , wherein an agent (iv) that selectively depletes NK cells is selected from an antibody specific for one or more of CD122 and CD56.
5. The method of claim 1 , wherein the agent (iv) is an antibody selected from an antibody specific for CD2, CD52, CD45; or anti-thymocyte globulin (ATG).
6. The method of claim 1 , wherein an agent (iv) further comprises an agent that selectively depletes T cells, selected from an antibody specific for one or more of CD3, CD4, and CD8.
7. The method of claim 5 , wherein the cellular composition comprises at least 50% hematopoietic stem cells selected for CD34 + expression from bone marrow, cord blood, or peripheral blood.
8. The method of claim 6 , wherein the cellular composition comprises at least 50% hematopoietic stem cells selected for CD34 + expression from bone marrow, cord blood, or peripheral blood.
9. The method of claim 5 , wherein the cellular composition comprises hematopoietic stem cells derived from pluripotent cells in vitro.
10. The method of claim 5 , wherein the cellular composition comprises at least 10 5 CD34 + cells/kg of recipient body weight.