IL-15 and IL-15R\alpha sushi domain based immunocytokines

1. An immunocytokine comprising:

a) a conjugate, and

b) an antibody or a fragment thereof, wherein said fragment thereof is capable of reacting with the same antigen as its antibody counterpart, directly or indirectly linked by covalence to said conjugate,

wherein said conjugate comprises:

(i) a polypeptide comprising the amino acid sequence of an interleukin 15, and

(ii) a polypeptide comprising the amino acid sequence of a sushi domain of an interleukin-15 receptor alpha (IL-15Rα)

wherein the conjugate comprises the amino acid sequence of SEQ ID NO: 17.

2. The immunocytokine of claim 1 , wherein the amino acid sequence of the conjugate and the amino acid sequence of the antibody or fragment thereof are not separated by any linker amino acid sequence.

3. The immunocytokine of claim 1 , wherein the amino acid sequence of the conjugate and the amino acid sequence of the antibody or fragment thereof are separated by a linker amino acid sequence.

4. The immunocytokine of claim 1 , wherein the antibody or fragment thereof is directed against an antigen selected from the group consisting of tumor neovascularization antigens and tumor extracellular matrix antigens.

5. The immunocytokine of claim 1 , wherein the amino acid sequence of the conjugate is in a C-terminal position relative to the amino acid sequence of the antibody or fragment thereof.

6. The immunocytokine of claim 1 , wherein the antibody or fragment thereof is directed against tumoral antigens.

7. A pharmaceutical composition comprising the immunocytokine as defined in claim 1 , and a pharmaceutically acceptable carrier.

8. The pharmaceutical composition of claim 7 , wherein said pharmaceutical composition is for treating cancer in a subject by an administration by injection at a dose of 2.5 mg/kg of subject or less.