A Hope: Contaminant-Free Synthetic Heparin
MONDAY, Aug. 18 (HealthDay News) -- Robert J. Linhardt is a chemist with a dream: making the blood-thinner heparin by the bucketful without using animal tissue.
It's a dream that has taken on urgency this year, as the U.S. Food and Drug Administration attributed more than 80 American deaths and hundreds of illnesses to contaminated heparin from the conventional source -- pig intestines processed in China.
That processing often is done in small mom-and-pop workshops, a situation conducive to contamination, said Linhardt, a professor of chemistry, biology and chemical engineering at Rensselaer Polytechnic Institute in Troy, N.Y.
"Our group has been working on understanding heparin biosynthesis for almost 30 years," he said. "We are working on what might be the next generation of heparin production, with no animal source."
Heparin has been made synthetically in the recent past but only in microscopically small amounts. Scheduled to speak Sunday at the American Chemical Society annual meeting, in Philadelphia, Linhardt described a new method of heparin biosynthesis that has produced amounts measured in milligrams. But, it's his hope that production can be scaled up a million-fold.
The process starts with a polysaccharide, a chain of carbohydrate units, extracted from the bacterium E. coli. "We treat it to reduce the molecular size, then subject it to enzymatic steps to convert it to heparin," he explained. "We use recombinant enzymes that are part of the natural pathway for heparin synthesis."
Now comes the difficult part, "scaling up the process so it is commercially viable," Linhardt said. "We are now working with one liter amounts. There are million-liter fermenters. We have to scale up three orders of magnitude, which is pretty daunting but not impossible."
Heparin is given by injection to prevent blood clotting during heart surgery, kidney dialysis and other procedures. Having a completely synthetic heparin would eliminate any worries about the kind of contamination that occurred this year, Linhardt said.
His group has received funding from the U.S. National Institutes of Health. "It's too early to approach a pharmaceutical company," he said. "We have talked to a number of them. They all are interested in the approach but want to wait."
Linhardt is aware that several drugs designed to replace not only heparin but also the widely used clot-preventing medication Coumadin are in clinical trials in Europe, with some already approved for medical use.
"I won't deny there's competition," he said. "But those drugs are a thousand times more expensive than heparin. Also, they are not as good as heparin. It has multiple activities, many of which benefit patients. Those drugs are very specific. They work well only for a small number of applications."
Synthetic heparin could cost no more than the animal-derived product, Linhardt said. "We believe that the heparin market is here to stay," he said.
To learn more about heparin, visit the U.S. National Library of Medicine.