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Each of these studies has value in its own right. Collectively, they underscore the quality and scope of the analysis referred to by Professor Feller and Dr. Wessner.

THE FIVE LITTLE PIGS:A TALE OF XENO-ORGAN TRANSPLANT

David Ayares

PPL Therapeutics, Inc.

PPL Therapeutics, said Mr. Ayares, is new to the ATP, having received its first grant only five months previously. The company—a U.S. subsidiary of a foreign company—is working to develop the technology of transgenic animals, based on earlier work at the Roslyn Institute in Scotland. At its Blacksburg, Virginia, facility it has two technology focuses:

  • transgenic production, that is, transplanting genes for various human proteins into farm animals, to produce pharmaceutically and nutritionally important proteins in their milk; and

  • xenotransplantation, that is, genetically modifying pigs so as to produce cells and organs suitable for transplantation into humans without spurring immune rejection of the grafts.

PPL's lead product is alpha-1-antitrypsin (AAT), a compound used in treating cystic fibrosis and other diseases. It is produced in the milk of sheep at very high rates, making the process much cheaper than the traditional recombinant methods. The company is also working on recombinant methods for producing a variety of other human proteins for therapeutic and nutritional purposes. It has several products in clinical trials. The company, PPL Therapeutics, became widely known a few years ago for producing Dolly, the cloned sheep. Cloning of animals is a necessary step in order to multiply quickly the amounts of the various pharmaceutical products that the original transgenic animals yield.

Xenotransplantation

This technology addresses a critical shortage of human organs for transplantation purposes. Altogether more than 62,000 patients are on waiting lists for lungs, hearts, or kidneys, and every day 11 of them die while waiting. The demand for transplants is growing, but the supply of human organs is not. The potential market is estimated at $10 billion per year.

Xenografts from pigs have several advantages:

  • the supply is potentially unlimited (through cloning);



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