Advance in cloning propels biotech firm
Naomi Aoki The Boston Globe
Saturday, August 24, 2002
PPL Therapeutics PLC has said it cloned piglets lacking both copies of a gene responsible for triggering a violent immune response in humans, advancing long-held hopes for growing a supply of organs available for transplant to people.
The announcement, made Thursday, appears to put PPL Therapeutics, the British company that helped clone Dolly the sheep in 1997, ahead of Immerge BioTherapeutics Inc. of Charlestown, Massachusetts, in the race to be the first to create a safe pool of donor organs from pigs.
Within days of each other in January, the two companies announced that they had cloned pigs whose DNA was altered to "knock out" one of the pair of alpha-1-galactose genes. The gene produces a coating of sugar on the surface of pig cells, which causes the human immune system to reject pig tissue and organs.
Immerge, a joint venture of Novartis Pharma AG and Biotransplant Inc., said its efforts to knock out both copies of the gene were "proceeding well." But PPL is the first to publicly announce that it has successfully cloned the "double knockout" pigs. Four healthy piglets were born on July 25. A fifth piglet died of unknown causes shortly after birth, the company said.
"This advance brings us closer to the promise of a potential solution to the worldwide shortage of organs and cells for transplantation," said David Ayares, chief operating officer and vice president for research at PPL's U.S. subsidiary in Virginia, where the pigs were cloned.
For nearly two decades, scientists have been studying pigs as a potential source of organs for humans. Surprisingly enough, pigs are biologically similar to people and carry fewer deadly diseases than primates.
But the research has been riddled with setbacks. Chief among them has been the powerful attack mounted by the body's immune system against foreign invaders - a natural defense that causes an almost immediate rejection of animal organs.
But advances in recent years have breathed new life into the field, known as xenotransplantation. At least six labs have been searching for a way to manipulate pigs so their organs could be used for human transplants.
Analysts predict the market could generate billions of dollars for companies that succeed in the quest. Nearly 80,000 people are on waiting lists, thousands more with ailing organs do not make the lists, and 16,000 people die each year in the United States alone while they wait.
"Developing another source of organs would have a profound impact on society, so from a practical perspective this is a very important advance," said Dr. Jeffrey Platt, head of transplantation biology at the Mayo Clinic in Minnesota.
In a matter of weeks, Ayares said, PPL scientists will begin transplanting cells from the young piglets into primates. If the cells are not rejected and survive for more than 90 days, the company plans to seek regulatory approval to transplant insulin-producing cells into humans as a potential treatment for diabetes.
"It's conceivable that in the next two years we could start human clinical trials," Ayares said.
The transplantation of whole organs is likely to be further away and require additional genetic modification. Other questions remain. Pigs also carry a potentially harmful virus, known as porcine endogenous retrovirus, or PERV. Although the virus has never been transmitted to humans, it raises concerns about the risk of infection.
Shares of PPL rose 0.25 pence to 7.5 pence (11.4 cents) in midday Friday trading, adding to the 0.5 pence gain Thursday as 6 million shares traded, more than 30 times the average daily volume.
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