Activatable cytokine polypeptides and methods of use thereof

Abstract

The disclosure features fusion proteins that are conditionally active variants of a cytokine of interest. 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. Typically, the fusion proteins further comprise an in vivo half-life extension element, which may be cleaved from the cytokine in the tumor microenvironment.

1 - 72 . (canceled) 
     
     
         73 . A fusion polypeptide having the Formula: [D]-[L1]-[A]-[L2]-[D], wherein A is a human interferon (IFN) polypeptide selected from a human interferon alpha (IFNa) polypeptide or a mutein thereof or a human interferon beta (IFNb) polypeptide or a mutein thereof; L1 and L2 are each independently a protease-cleavable polypeptide linker; and D is an IFN blocking moiety, 
     
     
         74 . The fusion polypeptide of  claim 73 , wherein the IFN polypeptide comprises an IFNa polypeptide, functional fragment, or mutein thereof, 
     
     
         75 . The fusion polypeptide of  claim 73 , wherein the IFN polypeptide comprises an IFNb polypeptide, functional fragment, or mutein thereof. 
     
     
         76 . The fusion polypeptide of  claim 73 , wherein D is an IFN blocking moiety, which also extends in vivo half-life. 
     
     
         77 . The fusion polypeptide of  claim 74 , wherein when the IFNa polypeptide and the IFNa blocking moiety are operably linked by the protease-cleavable polypeptide linker, the fusion polypeptide has attenuated IFNa-receptor activating activity, and wherein when cleavage of both linkers occurs, in vivo half-life of the IFNa polypeptide is substantially similar to that of naturally occurring human IFNa. 
     
     
         78 . The fusion polypeptide of  claim 75 , wherein when the IFNb polypeptide and the IFNb blocking moiety are operably linked by the protease-cleavable polypeptide linker, the fusion polypeptide has attenuated IFNb-receptor activating activity, and wherein when cleavage of both linkers occurs, in vivo half-life of the IFNb polypeptide is substantially similar to that of naturally occurring human IFNb. 
     
     
         79 . The fusion polypeptide of  claim 74 , wherein the IFNa-receptor activating activity of the fusion polypeptide is at least about 10X less than the interferon-receptor activating activity of the IFNa polypeptide that is produced by cleavage of the protease cleavable linker. 
     
     
         80 . The fusion polypeptide of  claim 75 , wherein the IFNb-receptor activating activity of the fusion polypeptide is at least about 10× less than the interferon-receptor activating activity of the IFNb polypeptide that is produced by cleavage of the protease cleavable linker. 
     
     
         81 . The fusion polypeptide of  claim 73 , wherein D comprises a serum albumin binding domain, a serum albumin, transferrin, or immunoglobulin Fc, or a fragment thereof. 
     
     
         82 . The fusion polypeptide of  claim 73 , further comprising a tumortargeting domain. 
     
     
         83 . A fusion polypeptide having the Formula: [D1]-[L]-[A]-[L2]-[D2], wherein A is a human IFN polypeptide, L1 and L2 are each independently a protease-cleavable polypeptide linker; and either D1 is human serum albumin or a fragment thereof, and D2 is a human serum albumin binding domain or D2 is human serum albumin or a fragment thereof, and D1 is a human serum albumin binding domain. 
     
     
         84 . The fusion polypeptide of  claim 83 , wherein D comprises an IFN receptor or fragment thereof. 
     
     
         85 . The fusion polypeptide of  claim 73 , further comprising a half-life extension domain. 
     
     
         86 . A method of treating a human subject with or at risk of developing cancer or a viral infection associated with cancer, comprising administering to the subject in need thereof an effective amount of a fusion polypeptide having the Formula: [D]-[L1]-[A]-[L2]-[D], wherein A is a human interferon (IFN) polypeptide, L1 and L2 are each independently a protease-cleavable polypeptide linker; and D is an IFN blocking moiety which also extends in vivo half-life. 
     
     
         87 . The method of  claim 86 , further comprising administering to the subject and an anti-PD-L1, anti-CTLA4, or anti-PD-1 antibody. 
     
     
         88 . The method of  claim 86 , further comprising administering to the subject an IL-2 polypeptide and/or an IL-12 polypeptide.