A serum albumin variant, or functional fragment thereof, comprising one or more amino acid substitutions selected from (i) glycine, isoleucine, lysine, methionine, phenylalanine, tryptophan, tyrosine, valine and leucine substituted for glutamine at position (522); (ii) valine substituted for alanine at position (552); and (iii) alanine, glutamic acid, histidine, serine, lysine and arginine substituted for glycine at position (572).