Improved yield of human albumin from transgenic cow milk

DESCRIPTION (provided by applicant): The overall goal of this program is to provide an abundant, cost-effective, biosecure source of human albumin for human therapeutic use by producing recombinant human albumin (rhA) in the milk of transgenic cows. Human albumin is isolated from donated human plasma, but shifts in the plasma fractionation industry, concerns about cost and anxiety about blood safety have motivated efforts to produce recombinant human albumin as an alternative source for human therapeutic applications. GTC Biotherapeutics Inc. (GTC-Bio) has expressed rhA in transgenic cows at levels of 2 g/L, which is adequate for the pharmaceutical excipient market but not the 400,000 kg annual worldwide therapeutic market. We have developed a strategy for selectively boosting rhA production to 10 g/L, a level that would make this production platform commercially feasible for the therapeutic human albumin market. Preliminary work suggests that hypermethylation of CpG motifs in the coding sequence may limit rhA expression in transgenic animals, and that removing CpG sites without altering the albumin amino acid sequence may significantly increase rhA expression. In this Fast-Track Phase I project, we propose to establish proof of principle for high-level production of rhA by: 1) remodeling the rhA gene to remove CpG sites; 2) evaluating the remodeled construct in transgenic mice, our standard test system; 3) optimizing a novel high-throughput screening method that will substantially reduce the effort and cost of recovering transgenic cell lines for use in generating transgenic animals by somatic cell nuclear transfer; and 4) optimizing an alternative selection scheme to preferentially recover transfected cell lines with high transgene copy numbers. Successful completion of this project will lead to a Fast-Track Phase II project to produce and characterize transgenic calves producing high levels of rhA in their milk. If this program is successful, it will be the first production of rhA at a commercial scale that is cost-effective for therapeutic applications.