Methods and compositions based on diphtheria toxin-interleukin-3 conjugates
The present invention provides methods for inhibiting interleukin-3 receptor-expressing cells, and, in particular, inhibiting the growth of such cells by using a diphtheria toxin-human interleukin-3 conjugate (DT-IL3) that is toxic to cells expressing the interleukin-3 receptor. In preferred embodiments, the DT-IL3 conjugate is a fusion protein comprising amino acids 1-388 of diphtheria toxin fused via a peptide linker to full-length, human interleukin-3. In certain embodiments, the methods of the present invention relate to the administration of a DT-IL3 conjugate to inhibit the growth of cancer cells and/or cancer stem cells in humans, which cells express one or more subunits of the interleukin-3 receptor. Exemplary cells include myeloid leukemia cancer stem cells. In other embodiments, the methods of the present invention relate to ex vivo purging of bone marrow or peripheral blood to remove cells that express one or more subunits of the interleukin-3 receptor such that the purged bone marrow or peripheral blood is suitable, e.g., for autologous stem cell transplantation to restore hematopoietic function.
1. A method for inhibiting cancer cells in a human diagnosed with plasmacytoid dendritic cell cancer, comprising administering to said human an effective amount of a pharmaceutical composition comprising a human interleukin 3 (IL-3)-diphtheria toxin conjugate, wherein said conjugate is administered at a dose greater than 4 μg/kg to about 12.5 μg/kg, and wherein said method results in inhibition of the growth of plasmacytoid dendritic cell cancer cells.
2. The method of claim 1 , wherein the inhibition results in a reduction in the proliferation of plasmacytoid dendritic cell cancer cells, a stabilization in the amount of plasmacytoid dendritic cell cancer cells, a reduction in the amount of plasmacytoid dendritic cell cancer cells, a stabilization in the amount of plasmacytoid dendritic cell cancer blasts, a reduction in the amount of plasmacytoid dendritic cell cancer blasts, an improvement in hematopoietic function in the subject, and/or an improvement in the marrow blast index of the subject.
3. The method of claim 2 , wherein said stabilization or reduction is measured by blood tests; blast count; blast percentage; physical examination; complete blood count; flow cytometric analyses; bone marrow aspirate; bone marrow analyses; skin surveillance, hematopoietic function; marrow blast index; the amount of normal white blood cells, red blood cells, and/or platelets; histology; immunohistochemistry; frequency of transfusion; and/or bone marrow biopsy.
4. The method of claim 1 , wherein the cells of said plasmacytoid dendritic cell cancer express the IL-3 receptor.
5. The method of claim 1 , wherein the conjugate is administered at a dose of about 5.3 μg/kg, about 7.1 μg/kg, about 9.4 μg/kg, or about 12.5 μg/kg.
6. The method of claim 1 , wherein the conjugate is administered at a dose that is the maximum tolerated dose.
7. The method of claim 1 , wherein the conjugate is administered at least two times a week.
8. The method of claim 1 , wherein the conjugate is administered at least three times a week.
9. The method of claim 1 , wherein the conjugate is administered over a period of two weeks or more.
10. The method of claim 1 , wherein the conjugate is administered once every day for five days.
11. The method of claim 1 , wherein the conjugate is administered for multiple cycles.
12. The method of claim 1 , wherein the human has abnormal cytogenetics.
13. The method of claim 1 , wherein the conjugate is a chemical conjugate.
14. The method of claim 1 , wherein the conjugate is a recombinantly expressed protein.
15. The method of claim 1 , wherein the conjugate is expressed as a single polypeptide comprising the catalytic and translocation domains of diphtheria toxin and human IL-3.
16. The method of claim 1 , wherein the conjugate comprises amino acid residues 1 to 388 of diphtheria toxin linked via a peptide bond to human IL-3.
17. The method of claim 1 , wherein the plasmacytoid dendritic cell cancer is refractory.
18. The method of claim 1 , wherein the human is in a state of remission from the plasmacytoid dendritic cell cancer.
19. The method of claim 1 , wherein the human has been previously treated with a therapeutic agent and/or has undergone radiation therapy.
20. The method of claim 1 , wherein the human is currently being administered a therapeutic agent other than a human IL-3-diphtheria toxin conjugate and/or is undergoing radiation therapy.
21. The method of claim 1 , wherein the human has relapsed from plasmacytoid dendritic cell cancer.
22. The method of claim 1 , wherein the human has failed plasmacytoid dendritic cell cancer treatment.
23. The method of claim 1 , wherein the human is susceptible to adverse reactions from other plasmacytoid dendritic cell cancer therapies.
24. The method of claim 1 , wherein the human is refractory to chemotherapy.
25. The method of claim 1 , wherein the human has not been previously treated for plasmacytoid dendritic cell cancer.