Press coverage of PPL pig-cloning news; mentions "rival team" of BTRN and Novartis:
Scientists Clone Pigs Lacking
Implant-Rejection Gene
Genetic Researchers Are Closer to Producing Animals
Whose Organs Could Be Transplanted Into Humans
By GAUTAM NAIK
Staff Reporter of THE WALL STREET JOURNAL
LONDON -- PPL Therapeutics PLC, which cloned Dolly the sheep, moved a step closer to producing genetically altered pigs whose hearts and other organs or tissues could be transplanted into people.
The company said it used cloning techniques to produce four piglets with organs more likely to be accepted by humans in a transplant operation.
Efforts to make it possible for animal organs to be used in human transplants have long been hindered by the problem of immune-system rejection. While such transplants aren't yet possible and probably won't be for at least several years, the demand for a new source of organs is acute. In the U.S. alone, more than 80,000 people are in need of organ transplants. Last year, about 24,000 transplants were done in the U.S., using human organs.
The scientific race to harvest animal organs for human use heated up in January. Within days of each other, PPL and a rival team composed of Swiss drug maker Novartis AG and biotechnology concern BioTransplant Inc. separately announced the creation of similar genetically modified pigs. The pigs lacked one of two copies of a gene that makes a sugar called alpha-1,3 galactose, the substance that triggers the immune-system rejection in transplants to humans. By inactivating one copy of that gene, both groups had taken the first step toward overcoming the rejection problem.
Now, scientists at PPL have made further progress by cloning four pigs with both copies of the gene deactivated, or "knocked out." Tissues from these pigs are "completely devoid" of the pig sugar that spurs the rejection, PPL said.
The pigs were born July 25 at PPL's labs in Blacksburg, Va. The development isn't of major commercial significance to PPL, mainly because it plans to spin off the operations involved in animal-to-human organ transplantation, also known as xenotransplantation. During the past three months of market turmoil, PPL shares have fallen 62%. Thursday, PPL shares rose 0.5 pence, or 7.4%, to 7 pence on the London Stock Exchange.
Scientists believe it may take five to seven years before xenotransplantation becomes a reality.
"We're now ready to go into pivotal pig-to-primate trials and need to show in excess of 90-day survival before [regulatory authorities] approve human trials," said David Ayares, chief operating officer and vice president of research at PPL. Those studies will begin during the next few weeks and should be completed in 12 to 18 months, he said.
PPL Chief Executive Geoff Cook said, "It's not inconceivable to do human studies between two and four years from now."
Pigs are deemed to be one of the best alternatives to organs harvested from human cadavers. They are easy to breed, and many of their organs are similar in size to those in humans. Once a genetic change is introduced into a population, "donor animals" can be bred easily by conventional techniques.
Still, there are obstacles. Pigs harbor certain viruses potentially dangerous to humans. And even if the rejection problem is resolved, it remains to be shown that a pig's kidney or heart will work well in a human body.
PPL drew a lot on the cloning technology that led to Dolly the sheep. In the latest experiment, scientists took skin cells from a pig fetus that already had one copy of the relevant genes knocked out and deactivated the second copy of the genes in the cells.
They then transferred the genetic information from these cells to unfertilized pig eggs -- the cloning operation -- and implanted the eggs into a foster mother. The resulting pigs were born with both copies of the relevant genes deactivated.
About 70% of PPL's "knockout" work was funded by the U.S. government.
Write to Gautam Naik at gautam.naik@wsj.com
Updated August 23, 2002 6:35 a.m. EDT |
