Pets are cancer treatment pioneers

By GINA STAFFORD

915 words

1 October 1999

10:16 AM

Associated Press Newswires

APRS

English

(c) 1999. The Associated Press. All Rights Reserved.

KNOXVILLE, Tenn. (AP) - They get the same kinds of cancers as the people they live with.

Melanomas, lymphomas, brain tumors and ovarian cancers - all strike cats and dogs about as often as the cancers occur in humans.

That's according to one scientist involved in a research project that has the potential to cure family pets of cancers while it yields data with human treatment applications.

The five-year project is just getting under way and teams a Knoxville-based biotech firm, Photogen Technologies Inc., with Tufts University School of Veterinary Medicine in Massachusetts.

Incorporated in May 1997, Photogen is a development-stage company working on photodynamic technologies for non-invasive or minimally invasive cancer treatments.

Such procedures also are the working arena of interventional radiologists such as Dr. Gerald Wolf, a Harvard University professor emeritus recently appointed Photogen's medical director.

Photogen President and Chief Executive Officer John Smolik said his company's work on photodynamic therapy, or PDT - which combines light and light-sensitive drugs to destroy cancer cells - helped attract Wolf.

"I think he was intrigued because it's totally non-invasive," Smolik said.

Wolf is former director of the Center for Imaging and Pharmaceutical Research at Massachusetts General Hospital. While there and with Photogen sponsorship, Wolf demonstrated that a PDT compound Photogen was researching could be activated with radiation. Photogen calls the compound PH-10.

The company found PH-10 while looking at a group of photo-active agents already approved by the U.S. Food and Drug Administration. PH-10 has been used as a food-coloring agent and can be activated with light and X-rays, Wolf said.

"We've submitted patent applications for its use as an X-ray sensitizer and as a photodynamic therapy agent," Smolik said.

In April, Photogen and Wolf revealed experimental work in which 70 percent of cancerous tumor cells in lab mice were killed in a 24-hour period using a combination of PH-10 and low-voltage radiation.

Recently, Wolf announced further research had shown a 90 percent "kill" rate of cancerous cells within 48 hours of treatment with the same combination of radiation and PH-10.

"In reality, it's pretty easy to cure tumors artificially grown in mice, but it hasn't been so easy to cure in humans," Wolf said. "The slowly developing cancers humans get are quite different from cancer a mouse gets seven days after planting a tumor in his body."

PH-10 greatly enhances the radiation's killing power and holds promise for preserving healthy tissue, Wolf said.

"About 70 percent of cancer patients get some form of radiation, but radiation almost kills normal cells as much as cancer," he said. "Put PH-10 in there, and it selectively binds to cancer cells and makes them much more sensitive to radiation."

"With that science," Smolik added, "it gave us the ability to very credibly say we can treat disease anywhere in the body without cutting you open."

Through the use of hardware and software built into Photogen's CT (computed tomography) scanners, a tumor can be located and a needle used to inject the drug into it, Smolik said.

"Once the tumor is loaded with the drug, it's radio-opaque, meaning it shows up on a CT scan," he said. "Then we focus radiation from a regular cancer radiation machine."

With PH-10's ability to enhance radiation, there's also the potential for dramatically reducing the amount of radiation needed. Side effects - like going bald, getting burned or becoming nauseated - may be eliminated, and health risks may be "greatly reduced," Smolik said.

Under Wolf's direction, Photogen's oncology program will be expanded to add breast cancer to its lung and prostate cancer treatment studies.

Wolf also will transfer his group to Tufts, where he will become a research professor at the vet school, which has the largest residency training program in veterinary emergency and critical care in the United States.

Tufts' Center for Animals and Public Policy offers the nation's only graduate degree in the field of human/animal relationships and related public policies.

"Tufts has a wonderful radiation program and was obviously the one we should try to affiliate with on a research basis," Wolf said. "The project has two good aspects: one is to improve cancer treatment for animals, the other is to get some experience treating the same kind of cancer as in humans."

That's to come from working with pets brought by their owners to the school for treatment. Photogen is providing Tufts with one of its Picker CT scanners for use in the program.

"At Tufts, they see over 6,000 animals a year brought in with naturally produced cancers," Smolik said. "We want to apply our technique to those pets - a dog with bladder cancer or skin cancer - and use these treatments and check their efficacy.

"We get data and the owner may get a well pet. That data from the treatment of naturally produced tumors will help design and better focus our human trials."

Wolf said the goal is to have clinical trials using the Tufts research under way within five years.

Meanwhile, though their subjects will be animals, researchers will "have to live by the same standards in veterinary care as we would with humans," Wolf said.

"The difference is the one who agrees to the treatment is the owner and not the patient."

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