QLT Inc., a biotechnology company dedicated to the development and commercialization of innovative ocular products has received orphan drug designation from US FDA for its commercial product, Visudyne (verteporfin for injection), for the potential treatment of chronic or recurrent central serous chorioretinopathy (CSC).
CSC can affect a range of visual function parameters, with an impact that can be mild to severe. CSC symptoms include reduced visual acuity (VA), scotomas, or blind spots in the central visual field, reduced contrast sensitivity and colour vision. Visual acuity losses may range from moderate to severe with patients experiencing a reduced daily functioning and quality of life. CSC is characterized by a serous detachment of the neurosensory retina from the retina pigment epithelium with an accumulation of serous fluid between the retina and retinal pigment epithelium (RPE). These defects occur in the macula and can include the fovea, thereby affecting central visual function with potentially significant visual disability. CSC is primarily a disease of middle-age and may be associated with lifestyles or occupations requiring a high level of visual functioning.
The Company is currently working with external advisors on potential clinical study options for the assessment of the safety and efficacy of Visudyne in the treatment of chronic CSC that will allow QLT to evaluate possible development plans.
The Orphan Drug Act allows for financial incentives to promote the development of drugs and biologics for the treatment of rare diseases or conditions which affect fewer than 200,000 patients in the United States. Incentives include a seven-year period of market exclusivity after approval for the indication, regulatory guidance, FDA fee reductions and tax credits related to development expenses.
CSC can affect a range of visual function parameters with an impact that can be mild to severe, and be acute or chronic in duration. Its symptoms include reduced visual acuity (VA), relative scotoma often in the central visual field, micropsia, metamorphopsia, reduced contrast sensitivity, disturbance of color vision, and decreased stereopsis. VA losses are usually moderate (20/20 to 20/60) but VA loss can be severe (20/200 or worse).
Acute CSC is usually self-limiting. Symptoms resolve spontaneously, particularly VA loss, without treatment within a few months of onset. Despite resolution of the detachment and improvements in VA, some patients may still experience residual symptoms (such as loss of contrast sensitivity), demonstrate lower retinal sensitivity and reduced retinal adaptability. Approximately 30% of patients can develop recurrent disease or chronic disease. In these cases, morbidity is more severe.
Persistent neurosensory detachment can lead to RPE damage and loss of macular photoreceptors, producing permanent visual impairment in VA (as large as 20/250 or worse). In addition, loss of color vision, central visual field, and depth perception have been reported. Chronic disease may lead to serious secondary conditions such as cystoid macular degeneration. Although CSC often initially presents unilaterally, it is likely a bilateral disease that develops asymmetrically such that one or both eyes are affected.
Visudyne therapy is a two-step procedure involving the intravenous administration of the drug into the patient's arm. A non-thermal laser light is then shone into the patient's eye to activate the drug. This produces a reaction that closes the abnormal leaky vessels, resulting in a stabilization of the corresponding vision loss. It is approved worldwide for the treatment of a form of wet age-related macular degeneration (AMD), the leading cause of legal blindness in people over the age of 50, and has been used in more than two million treatments worldwide.
It is commercially available in more than 80 countries for the treatment of predominantly classic subfoveal choroidal neovascularization (CNV). In addition, over 60 countries have approved Visudyne to treat other macular neovascular conditions such as minimally classic and occult with no classic AMD lesions, pathologic myopia and presumed ocular histoplasmosis.