Therion Biologics Corp. is joining forces with the Harvardresearcher who first isolated a strain of HIV in monkeys todevelop a live, attenuated AIDS vaccine.

Privately held Therion was formed in 1991 when OncogeneSciences Inc. purchased the cancer therapy and diagnosticscomponents of Applied bioTechnology Inc.

Therion of Cambridge, Mass., has spent the past 18 monthssearching for vaccines that can mimic a live, attenuated virusthat Harvard researchers have shown has protected six rhesusmonkeys from infection for two years.

The weakened SIV was created by Ronald Desrosiers ofHarvard Medical School, who first discovered SIV in a colony ofmonkeys in the U.S. He tested a less-virulent SIV strain thatlacks some genetic material in six monkeys and found that theydid not become ill. The monkeys were injected with full-strength SIV and fended off infections.

Desrosiers has helped Therion conduct research at Harvard'sNew England Regional Primate Research Center. Desrosiers'work is subject to an exclusive worldwide license agreementwith Therion.

His research shows "the longest-lasting and most completeprotection" of any potential vaccine tested in an animal so far,said Dennis Panicali, president and chief executive officer ofTherion.

Although immunizations for measles, mumps, rubella and polioall use live attenuated viruses whose infective ability isweakened, Panicali said, these illnesses are short-term andthere are good animal models in which to test the vaccines.

An AIDS vaccine would require a long-term study, he said, toaddress concerns that the virus may be able to regain virulenceor may contribute to cancer formation.

Although there are no good animal models for AIDS, Desrosiershas applied to the National Institutes of Health for permissionto conduct tests in chimpanzees, who don't develop AIDS. Thisresearch would show whether the virus replicates and whetherit causes antibodies to HIV -- information that can be valuablein creating a vaccine.

The National Institute of Allergy and Infectious Diseases hasagreed to fund and collaborate with the company on trials of agenetically engineered AIDS vaccine, TBC-3B. This is a liverecombinant vaccinia virus that expresses several HIVantigens. It is expected to elicit both neutralizing antibodiesand a cell-mediated immune response.

Meanwhile, the company is developing a potential vaccine forHIV-positive individuals who have not developed AIDSsymptoms. Particle-3B contains all major HIV antigens, but nonucleic acid, and is expected to help fight off an initial HIVinfection.

Such a therapeutic treatment might take four years or so todevelop, Panicali said, while a live, attenuated virus vaccine toprevent infection would require eight to 10 years to studylong-term safety issues.

The company is also investigating using vaccines as cancertherapy, a program that might have a shorter developmenttime frame. Its first inquiry focuses on colorectal cancer, inwhich a vaccine might scavenge tumor cells after surgery,radiation and chemotherapy.

Ribi ImmunoChem Research Inc. has a similar program inmelanoma. "It's relatively new," Panicali said, "and hastremendous promise in the treatment of certain types oftumors. It addresses a very large market."

The company began with $3.1 million in seed capital, primarilyfrom venture capital firms, and is currently in the middle ofanother round of venture capital financing, Panicali said.

-- Nancy Garcia Associate Editor

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

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