Immunotherapeutic molecules and uses

1. A composition for redirecting T cells to unwanted cells comprising:

(i) a targeting moiety capable targeting to unwanted cells wherein the targeting moiety is an anti-HER2 antibody or antigen binding fragment thereof and wherein the targeting moiety is not masked, and

(ii) at least one further moiety that has a masked immune cell binding region so as to prevent binding of the further moiety to an immune cell, wherein the immune cell binding region is an anti-CD3 antibody or antigen binding fragment thereof, and wherein the masked immune cell binding region is capable of being selectively unmasked by cleavage of at least one protease cleavage site when the molecule is in the vicinity of the unwanted cells so as to allow binding of the further moiety to an immune cell and,

wherein the further moiety is a scFv antibody in which the linker that joins the heavy chain variable domain (VH) and light chain variable domain (VL) is of insufficient length, optionally a peptide linker of 14 or less amino acids, to allow pairing of the VH and VL domains such that the scFv antibody cannot bind to the immune cell, and wherein, when in the vicinity of the unwanted cells, pairing of the VH and VL domains occurs by selectively cleaving one or more cleavage sites in said linker such that the VH and VL domains from the scFv antibody can bind to the immune cell.

2. A composition according to claim 1 , wherein the anti-CD3 antibody or antigen binding fragment thereof is a single chain antibody construct.

3. A composition according to claim 1 , wherein each of the further moiety and targeting moiety are parts of a single polypeptide chain.

4. A pharmaceutical composition, comprising a composition according to claim 1 , and a pharmaceutically acceptable carrier, diluent or excipient.

5. A method of treating carcinoma expressing HER2 on the cell membrane, the method comprising:

(i) administering a composition according to claim 1 to a subject or (ii) administering a composition according to claim 1 and a further therapeutic agent, which may include one or more of an immunostimulatory drug, an anti-cancer agent, and an inhibitor of an antibody response against the agent of the invention.

6. A method according to claim 5 comprising

(i) a composition according to claim 1 and

(ii) a further therapeutic agent suitable for treating carcinoma, optionally wherein the further therapeutic agent is one or more of an immunostimulatory drug, an anti-cancer agent, and an inhibitor of an antibody response against the agent of the invention.

7. The composition according to claim 1 , wherein the anti-HER2 antibody is a full length antibody.

8. The composition according to claim 1 , wherein the anti-HER2 antibody is an antigen binding fragment of an antibody.

9. The composition according to claim 1 , wherein the anti-HER2 antibody is an scFv, a camelid antibody, or an engineered camelid antibody.

10. The composition according to claim 1 , wherein the anti-HER2 antibody or antigen binding fragment thereof is a human antibody or a humanized antibody.

11. The composition according to claim 1 , wherein the anti-CD3 scFv is a human scFv or a humanized scFv.

12. The composition according to claim 1 , wherein the linker in the further moiety that joins the heavy chain variable domain (VH) and light chain variable domain (VL) of insufficient length is a peptide linker of 14 or less amino acids.

13. The composition according to claim 12 , wherein the peptide linker is of 10 amino acids.

14. The composition according to claim 12 , wherein the peptide linker is of 9 amino acids.

15. The composition according to claim 12 , wherein the peptide linker is of 8 amino acids.

16. The composition according to claim 12 , wherein the peptide linker is of 7 amino acids.