Virotherapy discussed trials using engineered adeno viruses to combat cancer. A new study uses a modified herpes simplex virus.

A modified herpes simplex virus, built with a potent immune stimulant to thwart the spread of cancer cells, is being tested in patients with a variety of tumor types, including melanoma, breast, head and neck, and colorectal cancer.

In early clinical studies, the engineered virus -- developed by Biovex Ltd. under the trade name OncoVEX -- showed promise of causing necrosis (death) of tumors cells in most patients.

"Tumor necrosis was evidenced clinically and/or by histology in biopsies taken about two weeks after the final dose in a number of patients," said Jennifer Hu, M.B.B.S., a clinical research fellow at Hammersmith Hospital (Imperial College) in London, who conducted much of the study. "In some cases necrosis was considerable."

Like other oncolytic viruses, the modified herpes simplex virus used in these studies was engineered to attack tumors cells without harming surrounding healthy tissue. This virus also was further altered to increase its potency.

However, the Biovex scientists went one step further when they inserted into the virus the gene for a powerful antitumor immunity stimulant called GM-CSF, (granulocyte macrophage colon stimulating factor). Its job is to induce an immune response to any surviving cancer cells released during the initial viral attack, essentially preventing the spread of these cells to other parts of the body.

"This aims to treat metastatic disease and reduce tumor recurrence," said Robert Coffin, Ph.D., chief scientific officer at Biovex Ltd. While this has not been demonstrated in patients, the approach has show promise in pre-clinical studies.

In a phase I/II clinical trial, the scientists tested their modified virus in 26 patients, including eight with melanoma, 13 with breast, three with head and neck cancer, and two with colorectal cancer. Each patient, all in the later stages of their disease, received either a single injection of the virus, the volume depending on tumor size, or in later stages of the clinical trial, three injections separated by two to three weeks.

Aside from evidence of tumor necrosis, the scientists detected expression of GM-CSF in injected tumors.

"There were no obvious differences in the effects on the different tumor types," added Hu. "Following the promising data, this version of OncoVEX is now entering Phase II development in a number of tumor types."

There's also work using modified measels virus.

Scientists at the Mayo Clinic in Rochester, Minn., reported that the engineered virus seeks out and destroys liver cancer cells, leaving surrounding healthy tissue in tact.

The iodine "transport" protein attached to the virus acts as a kind of homing beacon for radioactive iodine, providing a second line of attack against the cancer cells, technically known as radio-virotherapy.

"These results clearly demonstrate the high potential of this modified virus to serve as a novel vector for cancer gene therapy of hepatocellular carcinoma," said Boris Blechacz, M.D., a research fellow in the Molecular Medicine Program at the Mayo Clinic and the study's lead investigator.

It's beginning to seem as if what was once an SF phantasy is becoming a present reality.