Photo Dynamic Therapy


Our Photo Dynamic Therapy division focuses on the discovery of small, light-activated molecules and the development of laser systems that target and destroy cancer cells, control bacterial infections, and promote microbial sterilization.

Photo Dynamic Compounds ("PDC") are drugs that are cytotoxic (cell killing) when exposed to light at specific wavelengths and power levels. Theralase® photo dynamic compounds can be activated by a wide range of laser wavelengths and function effectively regardless of the oxygenation level present in the tissue under treatment, a unique and advantageous feature when dealing with cancerous tissue and certain bacteria that thrive in low oxygenated tissues.

We have partnered with the world-renowned Princess Margaret Cancer Centre in Toronto, Canada and are currently designing a Phase II clinical study of Non-Muscle Invasive Bladder Cancer ("NMIBC") using its lead photo dynamic compound. To view results for Phase 1b click here!

Our TLD-1433 photo dynamic compound has proven to be highly toxic to bladder cancer cells when activated by light, producing a 100% kill rate at very low concentrations.

How Photo Dynamic Therapy Works

Photo Dynamic Therapy ("PDT"), sometimes called photochemotherapy, is a form of phototherapy using nontoxic light-sensitive compounds that are exposed selectively to light. When photosensitizers are exposed to a specific wavelength of light, they produce a form of oxygen known as Reactive Oxygen Species ("ROS"), which is able to destroy resident cells through natural cell death, known as apoptosis.

Each photosensitizer is activated by light of a specific wavelength. This wavelength determines how far the light can travel into the body.

The laser light used in PDT can be directed through a fiber-optic (a very thin glass strand). The fiber-optic is placed close to the cancer to deliver the proper amount of light. The fiber-optic can be directed through a bronchoscope into the lungs for the treatment of lung cancer or through an endoscope into the esophagus for the treatment of esophageal cancer.

Photo Dynamic Therapy Benefits

An advantage of PDT is that it causes minimal damage to healthy tissue. However, because the laser light currently in use cannot pass through more than about 3 centimeters of tissue (a little more than one and an eighth inch), PDT is mainly used to treat tumors on or just under the skin or on the lining of internal organs.

The abnormal blood vessels in the wet form of macular degeneration are traditionally treated with laser. The thermal energy of the laser destroys both the blood vessels as well as the surrounding tissue (retina). Unfortunately, the majority of patients with wet macular degeneration have abnormal blood vessels located beneath the center of vision.

Thus, laser treatment will destroy the center of vision- the very thing we want to protect. Photodynamic therapy could allow selective destruction of abnormal blood vessels without damage to surrounding tissues.

The PDT dye is selectively absorbed by the abnormally proliferating blood vessels. When exposed to low levels of light ("non-thermal") the dye is activated and the abnormal blood vessels are selectively destroyed.

PDT therapy is currently being evaluated in clinical trials. Two drugs are being evaluated: verteporfin (Vysudine) from CIBA vision and tin ethyl etiopurpurin (SnET2) from Miravant.

Initial results are promising and have shown at least temporary recovery or preservation of vision in some patients. FDA approval of the PDT trials await completion of these studies to assess the overall safety and efficacy of these new agents.


It has no long-term side effects when used properly

It’s less invasive than surgery

It usually takes only a short time and is most often done as an outpatient

It can be targeted very precise

Unlike radiation, PDT can be repeated many times at the same site if needed

There’s little or no scarring after the site heals

It often costs less than other cancer treatments

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