Albumin variants and conjugates

摘要

Based on the three-dimensional structure of albumin, the inventors have designed variant polypeptides (muteins) which have one or more cysteine residues with a free thiol group (hereinafter referred to as “thio-albumin”). The variant polypeptide may be conjugated through the sulphur atom of the cysteine residue to a conjugation partner such as a bioactive compound.

主权项

1. A conjugation competent polypeptide comprising up to and including five conjugation competent cysteine residues,
a) wherein said polypeptide comprises an albumin sequence having at least 96% sequence identity to SEQ ID NO: 1; and b) wherein said polypeptide is a mutant comprising a Cysteine at or immediately following an amino acid residue in the albumin sequence which corresponds to the second, third, fourth or fifth residue relative to the N- or C-terminus of the albumin sequence; and/or c) wherein the polypeptide is a mutant comprising a Cysteine at or adjacent to an amino acid residue in the albumin sequence which:
i) has a solvent accessibility of at least 80%, is not located within secondary structure, has a B-factor of a C-alpha atom of at least 50 as defined by x-ray crystallography and has no polymorphism at this position that is known to cause thermal instability; orii) has a solvent accessibility of at least 80%, is located within secondary structure, has a B-factor of a C-alpha atom of at least 30 as defined by x-ray crystallography and has no polymorphism at this position is known to cause thermal instability; and d) optionally, wherein the polypeptide comprises additional alterations to the albumin sequence where each alteration is an amino acid deletion, substitution, or insertion; with the proviso that, where there are two or fewer conjugation competent cysteine residues within the polypeptide, such polypeptide does not include a cysteine at the position corresponding to position 1 of SEQ ID NO: 1.