Activatable interleukin-2 polypeptides and methods of use thereof
The disclosure features fusion proteins that are conditionally active variants of IL-2. In one aspect, the full-length polypeptides of the invention have reduced or minimal cytokine-receptor activating activity even though they contain a functional cytokine polypeptide. Upon activation, e.g., by cleavage of a linker that joins a blocking moiety, e.g., a steric blocking polypeptide, in sequence to the active cytokine, the cytokine can bind its receptor and effect signaling.
1. A conditionally active cytokine comprising:
a) a half-life extension domain which is an immunoglobulin Fc;
b) an IL-2 binding moiety, wherein the IL-2 binding moiety comprises a ligand-binding domain or fragment of a cognate receptor for the IL-2 polypeptide or an antibody or antigen binding fragment of an antibody that binds the IL-2 polypeptide; and
c) an IL-2 polypeptide;
wherein the IL-2 binding moiety and the IL-2 polypeptide are operably linked to the immunoglobulin Fc, and the IL-2 binding moiety is linked operably linked to the immunoglobulin Fc through a linker that comprises a cleavable peptide; and
wherein the IL-2 polypeptide has attenuated IL-2-receptor activating activity at least about 10 fold less than the IL-2-receptor activating activity of the polypeptide that comprises the IL-2 polypeptide that is produced by cleavage of the cleavable linker.
2. The conditionally active cytokine of claim 1 , wherein the IL-2 polypeptide binds to a IL-2 receptor.
3. The conditionally active cytokine of claim 2 , wherein the IL-2 polypeptide binds one, two, or three IL-2 receptor subunits with an affinity and/or selectivity that differs from that of the corresponding wild-type IL-2.
4. The conditionally active cytokine of claim 2 , wherein the IL-2 polypeptide binds to a IL-2 receptor alpha in a manner same as wild-type IL-2.
5. The conditionally active cytokine of claim 1 , wherein the binding moiety inhibits activation of IL-2 receptor alpha/beta/gamma by the IL-2 polypeptide.
6. The conditionally active cytokine of claim 1 , wherein the binding moiety inhibits activation of IL-2 receptor beta/gamma by the IL-2 polypeptide.
7. The conditionally active cytokine of claim 1 , wherein the serum half-life of the IL-2 polypeptide that is produced by cleavage of the second linker is comparable to the half-life of wild-type IL-2.
8. The conditionally active cytokine of claim 1 , wherein the IL-2 blocking moiety comprises a fragment of a cognate receptor for the IL-2 polypeptide.
9. The conditionally active cytokine of claim 8 , wherein the cognate receptor for the IL-2 polypeptide is IL-2Rbeta (CD122).
10. The conditionally active cytokine of claim 8 , wherein the cognate receptor for the IL-2 polypeptide is IL-2Ralpha (CD25).
11. The conditionally active cytokine of claim 8 , wherein the cognate receptor for the IL-2 polypeptide is IL-2Rgamma.
12. The conditionally active cytokine of claim 1 , wherein the IL-2 blocking moiety is an antibody or antigen binding fragment of an antibody that binds the IL-2 polypeptide and is selected from the group consisting of a single domain antibody, Fab, and scFv.
13. The conditionally active cytokine of claim 1 , wherein the IL-2 receptor activating activity is assessed by a CTLL-2 proliferation assay, a phosphor STAT ELISA, or HEK Blue receptor cell assay and by equal amounts, on a mole basis, of the IL-2 polypeptide and the cytokine.