Recombinant fusion proteins targeting CD47 and CD24, preparation and use thereof

1. A recombinant fusion protein, comprising an anti-CD24 antibody or an antibody fragment thereof, and a CD47 binding peptide,

wherein the anti-CD24 antibody or antibody fragment thereof comprises a heavy chain variable region, a heavy chain constant region, and a light chain variable region, wherein the heavy chain variable region comprises a heavy chain variable CDR-1 (HV-CDR1), a HV-CDR2 and a HV-CDR3 having amino acid sequences set forth in SEQ ID NOs: 7, 8 and 9, respectively, the light chain variable region comprises a light chain variable CDR-1 (LV-CDR1), a LV-CDR2 and a LV-CDR3 having amino acid sequences set forth in SEQ ID NOs: 10, 11 and 12, respectively, and the heavy chain constant region has Fc binding affinity and is linked to C-terminus of the heavy chain variable region,

wherein the CD47 binding peptide comprises a signal-regulatory protein (SIRP) extracellular domain having an amino acid sequence having at least 95% sequence identity to SEQ ID NO: 1,

wherein the CD47 binding peptide is linked to the anti-CD24 antibody or antibody fragment thereof.

2. The recombinant fusion protein of claim 1 , wherein at least one paratope of the anti-CD24 antibody or antibody fragment thereof is linked to the CD47 binding peptide at N-terminus of the heavy chain variable region or the light chain variable region constituting the paratope.

3. The recombinant fusion protein of claim 2 , wherein each paratope of the anti-CD24 antibody or antibody fragment thereof is linked to the CD47 binding peptide at N-terminus of the heavy chain variable region or the light chain variable region constituting the paratope.

4. The recombinant fusion protein of claim 3 , wherein each paratope of the anti-CD24 antibody or antibody fragment thereof is linked to the CD47 binding peptide at N-terminus of the heavy chain variable region constituting the paratope.

5. The recombinant fusion protein of claim 3 , wherein each paratope of the anti-CD24 antibody or antibody fragment thereof is linked to the CD47 binding peptide at N-terminus of the light chain variable region constituting the paratope.

6. The recombinant fusion protein of claim 1 , wherein the heavy chain variable region and the light chain variable region comprise amino acid sequences of i) SEQ ID NOs: 2 and 3, respectively; ii) SEQ ID NOs: 2 and 4, respectively; or iii) SEQ ID NOs: 5 and 6, respectively.

7. The recombinant fusion protein of claim 1 , wherein the heavy chain constant region comprises the amino acid sequence of SEQ ID NO: 13.

8. The recombinant fusion protein of claim 1 , further comprising a light chain constant region having the amino acid sequence of SEQ ID NO: 14, linked to the C-terminus of the light chain variable region.

9. The recombinant fusion protein of claim 3 , wherein the anti-CD24 antibody or antibody fragment thereof is linked to the CD47 binding peptide via a linker.

10. The recombinant fusion protein of claim 9 , wherein the linker is -(Gly-Gly-Gly-Gly-Ser) 3 -(SEQ ID NO: 15), -(Gly-Gly-Gly-Gly-Ser) 2 -(SEQ ID NO: 16), or -(Gly-Gly-Gly-Gly-Ser) 4 -(SEQ ID NO: 17).

11. The recombinant fusion protein of claim 9 , comprising

i) a CD47 binding peptide-linker-anti-CD24 heavy chain variable region-heavy chain constant region fragment having the amino acid sequence of SEQ ID NO: 18, and an anti-CD24 light chain variable region-light chain constant region fragment having the amino acid sequence of SEQ ID NO: 20;

ii) a CD47 binding peptide-linker-anti-CD24 heavy chain variable region-heavy chain constant region fragment having the amino acid sequence of SEQ ID NO: 18, and an anti-CD24 light chain variable region-light chain constant region fragment having the amino acid sequence of SEQ ID NO: 22;

iii) an anti-CD24 heavy chain variable region-heavy chain constant region fragment having the amino acid sequence of SEQ ID NO: 24, and a CD47 binding peptide-linker-anti-CD24 light chain variable region-light chain constant region fragment having the amino acid sequence of SEQ ID NO: 26; or

iv) an anti-CD24 heavy chain variable region-heavy chain constant region fragment having the amino acid sequence of SEQ ID NO: 28, and a CD47 binding peptide-linker-anti-CD24 light chain variable region-light chain constant region fragment having the amino acid sequence of SEQ ID NO: 30.

12. A nucleic acid molecule encoding the recombinant fusion protein of claim 1 .

13. An expression vector comprising the nucleic acid molecule of claim 12 .

14. A host cell comprising the expression vector of claim 13 .

15. A pharmaceutical composition, comprising the recombinant fusion protein of claim 1 , and at least one pharmaceutically acceptable excipient.

16. The pharmaceutical composition of claim 15 , further comprising at least one pharmaceutically acceptable adjuvant.

17. A method for treating a disease associated with over-expression of CD47 and/or CD24 in a subject in need thereof, comprising administering to the subject the pharmaceutical composition of claim 15 .

18. The method of claim 17 , wherein the disease is selected from the group consisting of acute myelocytic leukemia (AML), chronic myelocytic leukemia (CML), acute lymphoblastic leukemia (ALL), non-Hodgkin's lymphoma (NHL), multiple myeloma (MM), bladder cancer, ovarian cancer, prostate cancer, lung cancer, colon cancer, breast cancer, pancreatic cancer, renal cell carcinoma, cervical cancer, endometrial cancer, cholangiocarcinoma, stomach adenocarcinoma, and glioblastoma.