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 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.