Human serum albumin (HSA) is the most abundant protein in human serum. The circulation half-life of this stable protein is extremely long (over three weeks), a feature which has been exploited to obtain in vivo stabilization of recombinant proteins.
Using a serum albumin binding domain (ABD) derived from streptococcal protein G as fusion partner for proteins of therapeutic value, a strategy for production of engineered biotherapeutics with increased in vivo stability have been developed. The serum albumin binding activity of the ABD fusion partner results, after injection into the blood stream, in the formation of long-lived complexes with HSA.