The light treatment
There's a class of chemicals that can do a rather extraordinary thing - absorb energy from light and pass it on as chemical energy. These "photochemicals" have fascinated chemists for years but only recently have they become a hot topic in medical circles.

Light-activated chemicals called porphyrins are now being used to treat cancer tumors. In experimental therapies, a certain type of porphyrin is injected into a patient a few days before light treatment. The chemical settles in the tumor and when struck by light, from a laser for example, it becomes "excited" and passes energy on to oxygen molecules near the membranes of the tumor cells. The unstable oxygen molecules bounce around uncontrollably, blowing holes in the cell membrane and eventually destroying the tumor. The patient avoids all the terrible side effects of chemotherapy or radiation therapy.

Much of the ground-breaking research in light-activated drug therapy has been carried out at the University of British Columbia. Ten years ago four UBC professors founded a company - Quadra Logic Technologies - to develop drugs, and they are now focusing on these light-activated compounds.

Dr David Dolphin, a UBC chemistry professor and vice-president of technology development for QLT, is one of the pioneers of this research. Six years ago, Dolphin's group at UBC discovered new porphyrin-based compounds called "benzoporphyrin derivatives" or BPDs. Work done in collaboration with UBC microbiology professor Dr Julia Levy (one of the founders of QLT) showed that BPDs have great promise for use in light-activated drug therapy. The technology was transferred to QLT for further development.

BPD represents an improvement over an earlier light-activated drug. With BPD, the patient can safely enjoy sunlight 24 hours after treatment, compared to four weeks for the earlier drug. As well, the waiting time between injection of BPD and the use of light therapy is expected to be only about three hours, compared to two days for the earlier drug.

Now at the end of a long and costly period of extensive testing, BPD is soon to be used in clinical trials.

Cancer treatment may be only one of BPD's applications. It may also help provide safer blood products for transfusions. Initial studies show that 99.99999 percent of viruses in a blood product can be destroyed by treatment with BPD. logo