Genzyme Corp. and Tufts University have developed transgenicgoats by introducing a gene for lactate production of tissueplasminogen activator, a cardiovascular protein that is used totreat heart attacks.

The goats will produce t-PA in their mammary glands andsecrete it into their milk, where it can be harvested.

"We have been working on it for three years," said Genzymespokeswoman Donna LaVoie. "We may be able to start clinicaltrials in a couple of years, and commercialization is probablyfive to 10 years away."

Genzyme developed the transgenic goats to demonstrate thefeasibility of using livestock to produce pharmaceuticalproteins in their milk. Genzyme produced t-PA first because anundisclosed Japanese partner requested the protein. However,Genzyme is working on producing several other proteins in thismanner, LaVoie said.

The Cambridge, Mass., company has applied for a patent on itst-PA, which it said is a proprietary variant that is designed towork longer after injection than the t-PA now approved forsale by Genentech Inc.

Using livestock as bioreactors reduces manufacturing andproduction costs. Goats produce about 3 grams of the desiredprotein per liter of milk and sheep produce 35 grams per liter,vs. laboratory yields of one-tenth of a gram per liter of growthmedium.

The goats are capable of breeding and producing transgenicoffspring that express the t-PA producing gene. Genzymeselected goats because their 18-month gestation period isshorter than cows, which take 30 months.

However, a cow produces about 10,000 liters of milk annually,from which 30-35 grams of protein can be extracted per liter,compared with an annual milk production of 730 liters for agoat, said Dr. Jonathan MacQuitty, president and chiefexecutive of GenPharm International Inc., which has justcreated a transgenic dairy calf.

-- Kris Herbst BioWorld Washington Bureau

(c) 1997 American Health Consultants. All rights reserved.