Visudyne (verteporfin), the first drug therapy for patients with age-related macular degeneration (AMD) with predominantly classic subfoveal choroidal neovascularization (CNV), will be marketed by Novartis in India in this quarter.

A photosensitiser powder or solution for infusion, Visudyne comes from the Switzerland-based Novartis Opthalmic which was previously known as Cibavision.

There are very few treatment options and no proven preventive therapy for AMD whose cause is still unknown. Though laser photocoagulation is one treatment proven to be effective in clinical trials, but only a minority of patients with AMD are good candidates for treatment.

A photodynamic therapy or PDT, Visudyne, whose active ingredient is verteporfin, is a promising treatment that has recently received FDA approval in the United States. The treatment uses light-activated drugs to potentially halt or slow a normal cell growth.

The drug received approval for import and marketing from the Drug Controller General of India last month, Dr Harish Bolar, head of medical department regulatory affairs, Novartis India, informed.

This is a sight-saving drug is a specialized formulation which has been approved world over and the drug did not have to undergo clinical trials. Novartis presented all data regarding the drug and its clinical trials abroad to the DCGI, which referred the same to an expert panel before according its approval.

A vial of Visudyne costs Rs 80,000 to Rs 90,000 inclusive of about 65 per cent import duty. Three to five vials will be needed for treatment over two to three years, depending on the severity of the disease, Dr Bolar said.

Twenty five million people are afflicted by the disease all over the world. As production of Visudyne is a fairly high technology, there are no plans to manufacture the same in India, Dr Bolar added.

The administration of Visudyne therapy consists of a two-step process beginning with administration of the drug, or "photosensitizer," by intravenous injection into the arm.

The drug is activated in the eye using a non-thermal or cold laser, resulting in the closure of abnormal choroidal blood vessels, leaving normal vessels still functional.

It is believed once in the bloodstream Verteporfin attaches to low-density lipoproteins (LDL). The newly formed LDL and Verteporfin complex is taken up by the endothelial cells of the abnormal choroidal blood vessels, which have high levels of LDL-receptors. Verteporfin is then activated with red light 15 minutes after the start of the infusion. Because the laser does not generate heat, the overlying retina is not harmed by the technique.

PDT is a platform technology that utilizes light-activated drugs to treat a wide range of medical conditions. Any disease associated with rapidly growing tissue, including the formation of abnormal blood vessels, can potentially be treated with this technology. In addition to applications in cancer, photodynamic therapy has shown promise as a breakthrough treatment in ophthalmic, autoimmune (involving the immune system) and cardiovascular diseases.

While circulating in the bloodstream, the drug attaches to molecules called lipoproteins. Because cells undergoing rapid proliferation (cell division and growth) require a greater amount of lipoproteins than non-dividing cells, the drug is delivered more quickly and in higher concentrations to these types of cells.

Once the concentration of drug reaches appropriate levels in target cells, it is activated with a pre-calculated dose of light at a particular wavelength much less damaging than the current thermal or hot laser treatment - laser photocoagulation - which can leave permanent blind spots.

The activated Verteporfin subsequently causes the conversion of normal oxygen found in tissue to a highly energized form called "singlet oxygen." The singlet oxygen, in turn, causes cell death by disrupting normal cellular functions. The therapeutic effect is not observed until drug and light are combined.

Because the light is shone directly at the targeted tissue and the drug accumulates in these cells, damage to surrounding tissue is minimized. Because Visudyne therapy is a minimally invasive procedure that can be performed on an outpatient basis, it appears to be a cost-effective alternative to other treatments.

The type of light source used varies depending on the indication being treated. When treating internal conditions such as cancer, a fiber optic is used to deliver light to the treatment site from a laser. In ophthalmology, laser light is shone through the slit lamp of a microscope into the patient's eye.

Macular degeneration is often related to aging and is often abbreviated as AMD or ARMD. Most patients with AMD begin to notice problems sometime after age 50 and it is the most common cause of legal blindness among people over age 50 in the west.