Transthyretin variants

Abstract

The present invention provides a means for increasing the serum half-life of a selected biologically active agent by utilizing transthyretin (TTR) as a fusion partner with a biologically active agent. Specifically, the present invention provides substantially homogenous preparations of TTR (or a TTR variant)-biologically active agent fusions and PEG-TTR (PEG-TTR variant)-biologically active agent fusions. As compared to the biologically active agent alone, the TTR-biologically active agent fusion and/or PEG-TTR-biologically active agent fusion has substantially increased serum half-life.

1 . A nucleic acid encoding a transthyretin (TTR) variant comprising the amino acid sequence as set forth in SEQ ID NO:1 having two to three amino acid substitutions, wherein the cysteine at position 10 and the lysine at position 15 of SEQ ID NO:1 are substituted for another amino acid. 
     
     
         2 . The nucleic acid of  claim 1 , wherein the cysteine at position 10 of the TTR variant is substituted for alanine. 
     
     
         3 . The nucleic acid of  claim 1 , wherein one or more amino acids of the TTR variant is substituted to cysteine. 
     
     
         4 . The nucleic acid of  claim 3 , wherein the amino acid substituted to cysteine is selected from the group consisting of A37, D38, A81, and G83. 
     
     
         5 . The nucleic acid of  claim 4 , wherein the amino acid substituted to cysteine is A81. 
     
     
         6 . The nucleic acid of  claim 4 , wherein the amino acid substituted to cysteine is G83. 
     
     
         7 .- 8 . (canceled) 
     
     
         9 . The nucleic acid of  claim 1 , wherein the lysine at position 15 of the TTR variant is substituted for alanine. 
     
     
         10 .- 13 . (canceled) 
     
     
         14 . A nucleic acid encoding a fusion protein, said fusion protein comprising a biologically active protein fused to a TTR variant comprising the amino acid sequence as set forth in SEQ ID NO:1 having two to three amino acid substitutions, wherein the cysteine at position 10 and the lysine at position 15 of SEQ ID NO:1 are substituted for another amino acid, and wherein said fusion protein has a longer half-life in serum than the biologically active protein lacking the TTR variant. 
     
     
         15 .- 16 . (canceled) 
     
     
         17 . An expression vector comprising a nucleic acid of  claim 1 . 
     
     
         18 . A host cell comprising the expression vector of  claim 17 . 
     
     
         19 .- 20 . (canceled)