Source: Forbes Magazine

Author: Kerry A. Dolan

Drugs toxic enough to kill cancer cells are toxic enough to kill healthy ones, too. How can the poison be targeted? One possibility that has long fascinated scientists is to administer a drug that becomes activated only when exposed to radiation. One treatment for the rare skin cancer cutaneous T-cell lymphoma, for example, involves an interaction between a chemical (psoralen) and ultraviolet light. But the trick is not easily applied to internal cancers, and in any event most therapies involving light-activated drugs have been commercial failures.

Llew Keltner believes he can succeed where others have faiLED. He is chief executive of Light Sciences Oncology, a firm in Bellevue, Wash. that aims to use tiny light-emitting diodes to activate anticancer drugs. The LEDs are inserted through the skin using a biopsylike needle that goes directly into a tumor.

Light Sciences’ target, for now, is liver cancer, one of the deadliest and hardest cancers to treat. Most liver tumors can’t be removed with conventional surgery because either they are inaccessible or the patient is too sick to go under the knife. The treatment starts with the injection of a photosensitive chemical derived from chlorophyll, the green pigment in plants and algae that help them feed off sunlight. By itself the chemical is close to harmless. Exposed to red light, the molecule transfers energy to an oxygen molecule (O2), splitting it into singlet oxygen, which is unstable and causes damage to the tumor as well as to the lining of the blood vessels that supply it.

In a midstage trial of 27 patients with colorectal cancer that spread to the liver, tumors either partially or totally disappeared after 60 days in 24% of those treated with the light-activated drug, compared with 10% in those with untreated tumors. Even modest gains are enough to win a cancer drug a sizable market.

Results from a late-stage trial now under way with 200 patients in 11 countries won’t be known until the spring or summer of 2009, but Keltner is hoping that if the results are positive, approval from the Food & Drug Administration could come in 2010.

The LED procedure was born in the early 1990s in the garage of James Chen, a Seattle neurosurgeon looking for treatments for his patients with incurable brain cancer. Chen studied photodynamic therapy but wanted to see for himself if it worked. Instead of using a costly laser, he found an engineer to design a bundle of light-emitting diodes, which in 1993 were just beginning to be used in taillights in cars. In his makeshift lab Chen was able to use the LEDs to coax a drug to kill antibiotic-resistant bacteria. “It was amazingly effective,” says Chen. His next goal: develop the technology to kill cancer tumors inside the body.

Chen began talking to one of his patients, Craig Watjen, about his experiments. Watjen, a retired Microsoft (nasdaq: MSFT –news – people ) finance executive, eventually invested more than $50 million into what became Light Sciences Oncology. Watjen brought in Keltner, a physician with a doctorate in biostatistics, who became chief executive in 2005. Since then the tiny company has raised an additional $137 million from investors including the venture arm of Johnson & Johnson(nyse: JNJ – news – people ), Adams Street Partners and Fidelity Investments’ New Insights mutual fund for institutions.