SonoLight Technology

About Photodynamic and Sonodynamic Therapies

Photodynamic Therapy (PDT) is increasingly used in the practice of medicine and is the basis for the pioneering treatment for age-related wet macular degeneration. Other treatment modalities based on PDT have also been approved by the regulators. The principle involves a drug (the photosensitizer) which is relatively harmless until it is illuminated by light of various wavelengths, depending on the photosensitizer. The drug is delivered to the target tissue as selectively as possible and then the target tissue is illuminated. This activates the photosensitizer which then destroys the diseased tissue, predominately through the action of singlet oxygen. The killing effect is a combination of apoptosis (programmed cell death) and necrosis. It is also thought that PDT – mediated destruction of cancerous tissue may also serve to mobilize the immune system to further eliminate cancerous cells, through an ‘uncloaking’ of masked tumor antigens. The main drawback of PDT is the relatively limited penetration of light into human tissue. Even longer wavelength light cannot penetrate more than 5mm. This limits such treatments to surface (topical) applications unless light can be delivered inside the body, as with Quest’s prostate cancer treatment system.

Characteristics of the Ideal Photo/Sonosensitizer

• Absorption and phototoxic activity in the optimum ‘phototherapeutic window’ (560 - 700 nm)
• Excellent sonodynamic activity in the frequency range 1 – 3 MHz
• Low molecular weight (MW 550 – 880)
• Available in pure monomeric form
• Simple pharmacokinetics, rapid serum and skin clearance
• Negligible cytotoxicity in vitro and in vivo
• Excellent photopotentiation (2 orders of magnitude) conferring excellent safety margin
• Phototoxicity mediated via conventional type II reactions as well as type I (indicates utility for hypoxic tumour cells)
• Potent inhibitors of protein kinases
• Confer apoptotic cell death
• No genotoxicity
• Excellent tumor control
• Potential for targeted delivery
• Amenable to nuclear targeting to further augment sono/phototoxicity

Quest believes that its family of Hypocrellin B derived photosynthesizers share more of these desired characteristics than any other photosynthesizer currently in development or in use.

SL052 for Prostate Cancer – in Phase I Clinical Trial

SL052 is an injectible formulation of another HB derivative and is indicated for prostate cancer. It is anticipated that the compound will be injected intra-arterially or intravenously into patients and will selectively accumulate in the target tissue (prostate tumor). The SL052 photosensitizer will then be activated by laser light delivered through multiple optical fibers under the control of a sophisticated computerized control system. This technology will enable surgeons to selectively destroy the tumor volume, limiting the collateral destruction often caused by conventional surgery, cryotherapy, radiation, etc. In collaboration with Edmonton’s prestigious Cross Cancer Institute (Dr. Ron Moore), Quest has completed evaluations of the PDT system in animal models and is engaged in a phase I clinical trial on human patients.

There are currently two clinical centers participating in the clinical trial. The first center is with Dr. Ron Moore at the Cross Cancer Institute in Edmonton, and the second centre with Dr. John Trachtenberg at Princess Margaret Hospital in Toronto.

SL052 for Prostate Cancer is designed to be more effective than current treatments in destroying the cancerous tumors on the prostate while limiting collateral damage to healthy tissue. Pre-clinical studies in small and large animals have demonstrated the effectiveness of SL052 in selective destruction of normal and cancerous prostate tissues, with minimal side effects. The use of 18 F FDG (flurodeoxy glucose) PET imaging pre and post PDT treatment, highlighted the complete shut down of metabolic activity at the tumor site 24 hours after PDT treatment.

The practical application of this new PDT treatment system on the prostate gland has also been demonstrated using a canine prostate model. The intra-arterial drug delivery system allows the selective and significant accumulation of the photosensitizer in the prostate which is easily confirmed by fluorescence detection. PDT treatment of the prostate gland causes complete glandular tissue ablation within the intact capsule. Sexual and urological functions appear to be intact after the treatment with some acute voiding difficulties observed within the first few days.

Tumor Pre-treatment	35 Days Post SL052 PDT

Tumor ablation with SL052 Photodynamic therapy in a mouse tumor model

PET Imaging Pre and Post PDT Treatment




PET Imaging (Light Only Control)




Canine Prostate Glandular Tissue Ablation Post SL052 PDT Treatment