SYDNEY - Researchers at Royal Melbourne Hospital are set to start a major Phase I trial of a light-sensitive molecule that mops up traces of cancer cells left behind when a brain tumor is removed.

Those involved in the study said that, unlike other therapies involving lasers and light-sensitive compounds, the combination of boronated porphyrin compound (BOPP) and laser light requires only a few minutes to be effective.

Originally discovered by Steve Cahl at the University of San Francisco, the molecule is being developed by Pacific Pharmaceuticals Inc., of San Diego. Pacific has filed an investigational new drug application with the FDA for the trial.

Laurence Shaw, Pacific Pharmaceuticals chairman, president and CEO, told BioWorld International a major problem with present surgical treatment of malignant brain tumors is that the surgeon often is unable to see or remove tiny clusters of cells at the edges of the tumor. Those “nests“ of cells eventually grow into a new tumor.

Shaw said the BOPP trial involves giving the compound to the patient before the operation, so it is in the tumor cells at the time of the operation. After the surgeon removes the tumor, he then shines a low-intensity laser light into the cavity to destroy the remaining nests of cells.

Neither the BOPP compound itself nor the light alone will have any effect on the cells, only the combination of light and the BOPP molecules.

Preclinical trials have shown the BOPP molecules were taken up by tumor cells and quickly cleared from normal tissue, Shaw said.

He added that combinations of light-sensitive compounds and lasers have been tried before in surgical procedures, but required the light to the used for up to 50 minutes - a long time during surgery. Use of the BOPP molecule cuts that time closer to five minutes, Shaw said.

The Royal Melbourne studies are being led by Andrew Kaye, a world authority on the use of photodynamic therapy for the treatment of tumors.

John Hill, who is organizing the trials at the Royal Melbourne Hospital, said the Phase I trial, which Pacific describes as a Phase I/IIa, will involve 25 brain cancer patients and has been designed to test the toxicity of the drug.

Hill, who collaborated with Cahl on the discovery of BOPP, said doses will start at 0.25 milligrams per kilogram of body weight and may be increased to perhaps 30 to 40 times that level. He said a clinical trial notification has been lodged with the Australian authorities for the trial.

Pacific's Shaw commented the BOPP molecule represents a platform technology, as it could be suitable for the treatment of many hyperproliferative diseases, including cancer and non-cancerous disorders such as vascular restenosis. *