"As Seen in GEN—Flashback" Volume 8, No.7, July/August 1988
Researchers Produce Fab Proteins in E.coli
By Judy Berlfein
Scientists at International Genetic Engineering, Inc. (Ingene) of Santa Monica, Calif. have engineered the first E. coli to produce Fab proteins. The antibody fragments bind specifically to a human colon cancer cell line. Earlier this year, the company announced they were also synthesizing Fab proteins in yeast cells.
“There’s a real need for a quick way of making Fabs,” Dr. Ivor Royston, director of clinical immunology at the University of California San Diego Cancer Center said. “It looks like Fabs are going to be very useful for imaging cancers.”
The fragments penetrate tumors faster than whole antibody which is more advantageous when using isotopes with short half-lives.
For example, technetium and iodine-123 both have half lives of approximately 11 or 12 hours. Whole antibody takes two to three days to penetrate a tumor and by then the isotope has lost activity and produces a poor image. With a Fab fragment, the antibody enters the tumor quickly while the isotope is still intact. In addition, Dr. Royston added, there is evidence that by using Fabs, there may be less non-specific uptake in the liver.