Developments in Brief : Blood Clotting Agent Tested on Humans

The first human trials of genetically engineered Factor VIII, the clotting agent missing from the blood of most hemophiliacs, were begun last week by scientists at the University of North Carolina.

Hemophiliacs receive injections of Factor VIII, isolated from human blood plasma, to keep from potentially bleeding to death from even a minor cut or a bruise. Sometimes, however, Factor VIII is contaminated with viruses. Genetically engineered Factor VIII, produced in rodent cells grown in the laboratory, should be free of contamination.

“This represents a hope for a blood product that is not derived from a human source, that offers the potential for total purity,” said Alan Brownstein, executive director of the National Hemophilia Foundation. “That means that people with hemophilia will no longer be vulnerable to diseases that can be transmitted through transfusions.”

Hemophilia strikes one in every 10,000 males; it rarely affects women.

Factor VIII is by far the largest and most complex protein produced by genetic engineering techniques. It is, for example, 35 times as large as human insulin and 20 times as large as cancer-fighting interferons.