March 12, 1999

Plants and pharmaceuticals subject of Hardman Forum

Plants and pharmaceuticals subject of Hardman Forum

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At this year's Joel Hardman Studen-Invited Pharmacology Forum, Elaine Sanders-Bush, Ph.D. (left), received the Teaching Award in Pharmacology. On hand were (from left) students Michael Christensen, Chris Sansam and Lisa Parker. (Photo by Donna Jones Bailey)

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Julian K-C. Ma, Ph.D., at the recent Hardman Forum. (Photo by Donna Jones Bailey)

The rolling fields of farmland you see on a drive through the country may one day be acres of growing pharmaceuticals.

This vision ‹ that plants can be used to produce pharmaceutical products ‹ was the basis for this year's Joel G. Hardman Student-Invited Pharmacology Forum. The topic of the forum was "The Modern Medicine Cabinet: Botanical Approaches to Novel Therapeutics."

Paul Alan Cox, Ph.D., director of the National Tropical Botanical Garden in Hawaii, began the symposium with a presentation titled: "Ethnobotany and the Search for New Drugs."

"I'm a little intimidated speaking as part of a pharmacology symposium, since basically I'm a jungle guy," Cox said, showing a slide of the Hawaiian landscape. "My research tools are a notebook, a pencil, and a machete. This is my laboratory."

The congressionally chartered national garden in Hawaii seeks to conserve some of the planet's most endangered plants. In his world-wide quest for rare plants, Cox also searches for those that might benefit Western medicine.

He described himself as part anthropologist and part botanist; he studies how indigenous people use plants for medicine.

"Indigenous people represent an uncontrolled human bioassay carried out over generations. By learning how they use plants, we can obtain good candidates for therapeutics," Cox said.

In fact, Cox's search has yielded five lead compounds that pharmaceutical companies are pursuing for various therapeutic uses.

Carole L. Cramer, Ph.D., chief scientific officer of CropTech Development Corp. and professor of Plant Pathology and Physiology at Virginia Tech, presented "Tobacco-based Bioproduction of Complex Human Enzyme Therapeutics."

Although the majority of pharmaceuticals are small molecules, there is an emerging class of drugs based on proteins, Cramer said. CropTech, which Cramer formed with her husband, David N. Radin, Ph.D., seeks to use tobacco plants to produce protein pharmaceuticals.

But why tobacco?

"Tobacco is the easiest plant to genetically engineer, and it is a prolific seed producer, so you can scale up rapidly from a single engineered plant," Cramer said. "It is also an excellent biomass producer, and there is broad public support for new uses for tobacco."

CropTech has successfully engineered tobacco plants to produce the human clot-busting enzyme urokinase, which will undergo clinical trials for the treatment of heart attack and stroke. The company has also created tobacco plants that produce the enzymes glucocerebrosidase and iduronidase, used to treat Gaucher Disease and Hurler's Syndrome, respectively.

Julian K-C. Ma, Ph.D., Senior Lecturer and Consultant, United Medical and Dental Schools, Guy's Hospital London, concluded the symposium with his presentation: "Plants ‹ An Efficient Expression System for Complex Mammalian Proteins."

Ma has genetically engineered tobacco plants to produce secretory antibodies directed against Streptococcal mutans, bacteria that cause tooth decay. The secretory antibodies are composed of four different protein components, which tobacco plants can successfully synthesize and assemble into a complex, three-dimensional structure.

Ma tested the function of the antibodies by applying them directly to the teeth of volunteers for 15 days. The antibodies protected teeth from S. mutans colonization for up to one year after treatment, whereas saline or different antibodies provided no protection from S. mutans colonization.

"This is the first trial in humans to show that an antibody produced by plants is functional and effective. We are interested in this type of immunotherapy to prevent other kinds of mucosal infections," Ma said.

In addition to Ma's secretory antibodies, two other plant-produced proteins have successfully passed Phase I clinical trials.

The annual student-organized pharmacology forum honors Joel G. Hardman, Ph.D., professor of Pharmacology, Emeritus. Hardman was chair of the department of Pharmacology from 1975-1990, and served as associate vice-chancellor for Health Affairs until his retirement in 1997.

"The students named the forum in honor of Dr. Hardman to acknowledge his contributions to enhancing graduate student training and his career-long efforts as a researcher and mentor," said Ronald B. Emeson, Ph.D., Joel G. Hardman Professor of Pharmacology.

Prior to the symposium presentations, Elaine Sanders-Bush, Ph.D., professor of Pharmacology and Psychiatry, received the 1999 Teaching Award in Pharmacology.

"Dr. Sanders-Bush has an obviously strong commitment to bringing out the best in every student," said Michael Christensen, one of the Pharmacology graduate students presenting the award.

The Pharmacology graduate student organizers of this year's forum were Ashley Brady, Linda Hutchinson, and John Partridge.