MONTREAL - The technique of using light-activated drugs to kill cancer cells in solid tumors in the body has received a great deal of attention in recent years.

Theratechnologies Inc., of Montreal, is employing the process in a different way. The company has developed a photosensitive molecule, TH 9402, as well as an easy-to-use photodynamic device that helps eradicate cancer cells outside of the body.

The ex vivo photodynamic purging (PDP) process involves withdrawing a bone marrow or peripheral blood sample from the patient. The cancerous cells present in the sample are saturated with TH 9402 and destroyed using an activated light source.

The remaining normal progenitor cells are reinfused into the patient in the form of an autologous graft. This process helps restore the bone marrow function that has been ablated as a result of intense chemotherapy and radiotherapy.

Andre de Villers, president and CEO of Theratechnologies, said the company now has received approval from Health Canada's Medical Devices Bureau, in Ottawa, to begin clinical validation of the PDP treatment in patients suffering from chronic myeloid leukemia.

A trial, scheduled to start shortly, will be conducted by Denis Claude Roy, a hematologist at Maisonneuve-Rosemont Hospital, in Montreal. PDP has been classified as a medical device, not as a drug or biological product, which means the clinical validation period could be reduced considerably.

Theratechnologies also is conducting preclinical trials using PDP in non-Hodgkin's lymphoma, and the company intends to apply the therapy against breast cancer. *