主页 > 生命科学 >
【技术产业】肝素事件：换个角度 机遇和危机并
Skip to next paragraph
Enlarge This Image
Rick Friedman for The New York Times
Hiren Patel at Altus Pharmaceuticals, which is working to develop a synthetic version of pancreatic enzymes.
The pills are life-sustaining for most of the nearly 30,000 people in the United States with cystic fibrosis, a hereditary disease that attacks the lungs and digestive tract.
But partly because of the drug’s source there have been longstanding concerns about those capsules, according to Leslie Hendeles, a University of Florida professor of pharmacy and pediatrics who has studied them.
“What would happen if there were a virus, a pig virus, something analogous to mad cow disease?” Dr. Hendeles asked.
The recent recall of the Baxter International blood thinner heparin, which has been linked to 19 deaths and whose main ingredient comes from pig intestines, has raised public awareness that even in the age of sophisticated bioengineering, certain crucial medicines are still derived from animal parts. The concerns remain, even though, as it turned out, the heparin problem had nothing to do with the pigs.
A company called Scientific Protein Laboratories, which supplies the active ingredient in heparin to Baxter International, is also the supplier of much of the pig-derived pancreatic enzymes used by cystic fibrosis patients.
Medical and drug scientists have long worried about animal-derived drugs, but they also know that the search for synthetic alternatives has often ended in frustration.
“A number of pharmaceutical firms are trying to eliminate all animal-sourced products from their raw material streams,” said Dr. Robert G. Rohwer, the director of a Department of Veterans Affairs neurovirology laboratory. “It’s a very demanding task.”
In the case of cystic fibrosis, though, continued as well as a history of unusual variations and impurities in the pig-derived pills, have led the Cystic Fibrosis Foundation to pursue an alternative. The foundation is working with Altus Pharmaceuticals of Cambridge, Mass., to develop a synthetic version of the enzyme capsules. Altus has entered the final stages of clinical studies on the drug and is planning to seek Food and Drug Administration approval next year to market its synthetic product.
The company’s chief financial officer, Jonathan I. Lieber, said that to make the drug, the company uses enzymes derived from microbes that come not from animals but from bacteria and fungus. The enzymes are crystallized, then reproduced in large vats similar to those used to brew beer.
Synthetic replacements are also being sought for other medical products, including the lung fluids called surfactants that are used in neonatal wards and for raw materials used in pharmaceutical production. There are also various efforts to find synthetic versions of heparin.
History has shown that the risk of transmitting disease from animal-based drugs, while small, is not merely theoretical, according to Paul W. Brown, a retired National Institutes of Health senior investigator.
“Any time you take a tissue or an extract process from a tissue from one species and put it into a another species or even another animal, you run the risk of unwanted pathogens that you didn’t know were there; that’s been responsible for repeated problems over the course of time,” Dr. Brown said. “If you can do something without taking tissue or a product from another being, you’re ahead of the game.”
Even before the heparin recall, efforts were under way to find synthetic alternatives to that drug. Millions of vials of heparin are used each year in this country to prevent the formation of blood clots during major surgery and kidney dialysis. So far, no ideal synthetic version has been found.
Arixtra, a synthetic drug that is marketed by GlaxoSmithKline and copies the most active portion of heparin, has been successfully used for some types of surgery. But besides being about 10 times as expensive as heparin — the company said Arixtra sells for about $42 for a low dose and twice that for a higher dose — it has at least one major medical drawback. Unlike heparin, Arixtra has no specific antidote to enable doctors to reverse its anti-clotting properties if a patient develops bleeding problems. Robert J. Linhardt, a heparin expert at Rensselaer Polytechnic Institute in Troy, N.Y., who has been working to develop another synthetic alternative, said the use of pigs for heparin was of less concern to him than the issue of where the heparin pigs came from. The recent recall in the United States involved heparin material from Chinese pigs that Scientific Protein Laboratories supplied to Baxter International, a leading heparin marketer.
“There are 700 million pigs slaughtered each year, and 400 million are slaughtered in China,” Dr. Linhardt said. “It makes us dependent. Basically 70 percent of the supply of heparin is coming from China. There’s very little regulatory control in China. So the reason why synthetic heparins are appealing is that they could be made in places where there is stronger regulatory control.”
阅读本文的人还阅读：
作者:admin@医学,生命科学 2010-12-12 17:11
医学,生命科学网