A fusion polypeptide of the formula: - - - - or - - - - or - - - - or - - - - or - - - - or - - - - wherein, A is an interleukin 2 (IL-2) polypeptide; B is a half-life extension element, wherein the half-life extension element is human serum albumin, or an antigen binding polypeptide which binds human serum albumin; L1 is a protease-cleavable polypeptide linker and L2 is a polypeptide linker that is optionally protease-cleavable, wherein for each of L1 and L2, independently, the protease is selected from the group consisting of a kallikrein, thrombin, chymase, carboxypeptidase A, cathepsin G, an elastase, PR-3, granzyme M, a calpain, a matrix metalloproteinase, a plasminogen activator, a cathepsin, a caspase, a tryptase, or a tumor cell surface protease; and; D is an IL-2 blocking moiety wherein the blocking moiety is an antibody or antigen-binding fragment of an antibody that binds the IL-2 polypeptide; and wherein the fusion polypeptide has attenuated IL-2 receptor activating activity, wherein the IL-2-receptor activating activity of the fusion polypeptide is at least about 10 fold less than the IL-2 receptor activating activity of the polypeptide that contains the IL-2 polypeptide that is produced by cleavage of the protease-cleavable linker L1 or, when L2 is protease-cleavable, by cleavage of both L1 and L2, and wherein the IL-2-receptor activating activity is assessed using a CTLL-2 proliferation assay, a phospho STAT ELISA, or HEK Blue reporter cell assay with equal amounts on a mole basis of the IL-2 polypeptide and the fusion polypeptide. A is an interleukin 2 (IL-2) polypeptide; B is a half-life extension element, wherein the half-life extension element is human serum albumin, or an antigen binding polypeptide which binds human serum albumin; L1 is a protease-cleavable polypeptide linker and L2 is a polypeptide linker that is optionally protease-cleavable, wherein for each of L1 and L2, independently, the protease is selected from the group consisting of a kallikrein, thrombin, chymase, carboxypeptidase A, cathepsin G, an elastase, PR-3, granzyme M, a calpain, a matrix metalloproteinase, a plasminogen activator, a cathepsin, a caspase, a tryptase, or a tumor cell surface protease; and; D is an IL-2 blocking moiety wherein the blocking moiety is an antibody or antigen-binding fragment of an antibody that binds the IL-2 polypeptide; and wherein the fusion polypeptide has attenuated IL-2 receptor activating activity, wherein the IL-2-receptor activating activity of the fusion polypeptide is at least about 10 fold less than the IL-2 receptor activating activity of the polypeptide that contains the IL-2 polypeptide that is produced by cleavage of the protease-cleavable linker L1 or, when L2 is protease-cleavable, by cleavage of both L1 and L2, and wherein the IL-2-receptor activating activity is assessed using a CTLL-2 proliferation assay, a phospho STAT ELISA, or HEK Blue reporter cell assay with equal amounts on a mole basis of the IL-2 polypeptide and the fusion polypeptide. wherein the fusion polypeptide has attenuated IL-2 receptor activating activity, wherein the IL-2-receptor activating activity of the fusion polypeptide is at least about 10 fold less than the IL-2 receptor activating activity of the polypeptide that contains the IL-2 polypeptide that is produced by cleavage of the protease-cleavable linker L1 or, when L2 is protease-cleavable, by cleavage of both L1 and L2, and wherein the IL-2-receptor activating activity is assessed using a CTLL-2 proliferation assay, a phospho STAT ELISA, or HEK Blue reporter cell assay with equal amounts on a mole basis of the IL-2 polypeptide and the fusion polypeptide.