Grow Your Own: Protalix BioTherapeutics Produces Drugs in Carrot Cells

Abstract

In Charlotte, North Carolina, two scientists coincidentally named Ken—Kenneth Piller, Ph.D., and Kenneth Bost, Ph.D. —have turned soybeans into transgenic protein factories. Their 4 person company, Soymeds (http://www.soymeds.com), is developing a bioterror vaccine, a protein to downregulate immune response for multiple sclerosis, called a toleragen, and thyroglobulin, a therapeutic diagnostic.According to Piller, soybeans are natural storage systems. They produce proteins that are well tolerated and can be delivered orally in soymilk or as an injectable. “We think soybeans are a great proof of concept because they are protein-rich,” said Piller. “Any cell cultures are low protein.” About 20 soybean plants contained in a greenhouse could make a gram of target protein.Piller and Bost received initial funding from the NIH while at the University of North Carolina at Charlotte. Soymeds just got a 3 year, $1.5 million SBIR grant to develop a diagnostic using homogenous soybean-produced thyroglobulin. According to Piller, thyroglobulin is an extremely large protein and therefore difficult to produce. The only current source of thyroglobulin, which costs $100 a milligram, is cadaver thyroids. Thyroglobulin purified this way is highly variable, so tests aren’t standardized and the same test by the same company must be used for yearly checkups. Soymeds thinks they can use soybeans to develop a cheaper, more uniform thyroglobulin protein.Soymeds is developing a soy-derived therapeutic for treatment of multiple sclerosis. Myelin antigens are difficult to express but Soymeds' MS antigen can be delivered in a drinkable soy milk formulation. This therapeutic was tested successfully in mice. The company is also developing a vaccine against staphlococcal enterotoxin B (SEB), a potential biowarfare agent, which was successful when tested in mouse and pig models.There are still technical issues. While virus-like particles are very immunogenic, for example, subunit vaccines against diarrheal diseases require an oral adjuvant—something to help mediate a strong immune reponse—and there are still no good adjuvants that can be used with oral vaccines.Piller realizes that the public has a negative perception of genetically modified organisms. “The reason is that Americans don’t see a benefit coming out of it,” says Piller. “Wouldn’t it be great if a plant-derived therapeutic could save the lives of millions of children or stop and reverse the effects of multiple sclerosis? Oftentimes new therapeutics treat symptoms rather than diseases. We are attempting to target the root of the disease.”Piller recalls a discussion about biosimilars versus biobetters at the Verona conference. “A strong feeling among several leaders in the field is that really, you need a biobetter to advance this technology to the marketplace,” says Piller. “We are trying to fill gaps for problems that currently exist for which there is no solution.”