Vitrase^®

We are developing Vitrase^®, a proprietary formulation of ovine hyaluronidase, for the treatment of vitreous hemorrhage. Vitrase^® for use as a spreading agent was approved for marketing in the U.S. in May 2004. Prescribing information, click here

How Vitrase^® Works (Mechanism of Action):
The term hyaluronidase describes a group of naturally occurring enzymes that can digest certain forms of carbohydrate molecules called proteoglycans. When injected into the vitreous humor, Vitrase^® breaks down the proteoglycan matrix, causing the vitreous humor to liquefy. The procedure is performed in several minutes in an ophthalmologist's office and is virtually painless due to the application of a topical anesthetic. Vitrase^® can also be injected into connective tissue, where it modifies the permeability of such tissue through the hydrolysis of hyaluronic acid, thereby decreasing the viscosity of the cellular cement and promoting diffusion of injected drugs, thus facilitating their absorption.

Vitreous Hemorrhage:
A vitreous hemorrhage occurs when retinal blood vessels rupture and bleed into the vitreous humor. Vitrase has yet to be approved by FDA as safe and effective for this use. These hemorrhages result from leakage from abnormal, weak blood vessels and are associated with diabetic retinopathy, trauma and other factors. The immediate consequence of a vitreous hemorrhage is a reduction in the amount of light that can pass through the normally clear vitreous humor to the retina. The effects of a hemorrhage can be limited to a few dark spots in vision or, in the case of a severe vitreous hemorrhage, can result in completely obscured vision. Depending on the severity of the vitreous hemorrhage, it may take several months or significantly longer for the body to reabsorb the blood and for the patient to regain vision. In addition to obstructing the patient's vision, a vitreous hemorrhage often prevents physicians from seeing into the back of the eye to diagnose or treat the cause of the hemorrhage. If extensive or repeated bleeding occurs, fibrous tissue or scarring can form on the retina, which can lead to a detachment of the retina and permanent vision loss or blindness.

Patients who seek medical care for a vitreous hemorrhage often visit a physician, who then refers them to a retinal specialist. Treatment options for patients with a vitreous hemorrhage are limited. Currently, there is no drug treatment for vitreous hemorrhage and most retinal specialists initially recommend a "watchful waiting" period, during which the attending physician provides no medical treatment in the hope that the hemorrhage will clear on its own. The risks related to watchful waiting may include continued bleeding and, if caused by diabetic retinopathy, disease progression during the time it takes for the blood to clear on its own, if at all.

An alternative to watchful waiting is a surgical procedure called a vitrectomy, in which the vitreous humor and hemorrhage are surgically removed and replaced with a balanced salt solution. There are serious risks associated with a vitrectomy, including both cataract formation and possible loss of vision associated with retinal detachment. These risks contribute to the limited use of vitrectomy as an initial treatment option for vitreous hemorrhage patients.

Hemorrhage density can vary significantly between patients who experience vitreous hemorrhage, but even a mild hemorrhage indicates the existence of a serious problem. Because of the absence of a validated and generally accepted medical definition of the various densities of vitreous hemorrhage, we classify a vitreous hemorrhage as either mild, moderate or severe depending on the density of the vitreous hemorrhage as observed by the physician:

• mild vitreous hemorrhage is characterized by trace blurring of retinal blood vessels;
• moderate vitreous hemorrhage is characterized by partial obscuration of retinal blood vessels and/or the optic nerve; and
• severe vitreous hemorrhage is characterized by complete obscuration of retinal blood vessels and/or the optic nerve.