Sirion Therapeutics, Inc, a privately held ophthalmic-focused biopharmaceutical company, announced that the US Food and Drug Administration (FDA) has approved its New Drug Application for Zirgan (ganciclovir ophthalmic gel) 0.15 per cent as a treatment for acute herpetic keratitis (dendritic ulcers). The FDA granted orphan drug designation to Zirgan for this indication in April 2007.

Herpetic keratitis, an ocular disease caused by the herpes simplex virus (HSV), is a significant cause of corneal blindness and a leading indication for corneal transplantation in the US, with approximately 50,000 new and recurrent cases each year. After the initial outbreak, HSV becomes a latent infection in the trigeminal ganglion or cornea, with repeated recurrences that frequently lead to corneal scarring and ocular inflammation, increasing the risk of blindness.

Zirgan is the trademark of Laboratoires Théa of France and Sirion Therapeutics, Inc., has the exclusive US rights to develop and market Zirgan. Available in Europe under the brand name Virgan, this topical ophthalmic antiviral gel has successfully treated herpetic viral infections for more than 10 years. In 2007 Sirion received orphan drug designation from the FDA for ganciclovir ophthalmic gel. This designation is a special status for rare diseases or conditions that affect fewer than 200,000 patients in the US.

The FDA approval was based on the results of clinical trials conducted by Laboratoires Théa of France in Europe, Asia, and Africa that compared the efficacy and tolerability of Zirgan to acyclovir ophthalmic ointment 3 per cent in patients with herpetic keratitis. Both ganciclovir gel and acyclovir ointment are standardof- care therapies outside of the US, and selectively target the replication of HSV DNA, unlike older antivirals which affect both healthy and infected cells.

In one open-label, randomized, controlled, multicenter clinical trial which enrolled 164 patients with herpetic keratitis, Zirgan was non-inferior to acyclovir in patients with dendritic ulcers. Clinical resolution (defined as percentage of healed ulcers) at Day 7 was achieved in 77 per cent (55/71) for Zirgan versus 72 per cent (48/67) for acyclovir. In three randomized, single-masked, controlled, multi-centre clinical trials which enrolled 213 patients, Zirgan was non-inferior to acyclovir in patients with dendritic ulcers. Clinical resolution at Day 7 was achieved in 72 per cent (41/57) for Zirgan versus 69 per cent (34/49) for acyclovir.

"The approval of Zirgan represents a true advance in topical antiviral therapies in the US," commented Barry Butler, CEO of Sirion. "Up to this point, no therapy targeting only viral-infected cells was available for topical ocular use. Zirgan provides doctors with a much needed modern treatment for herpetic keratitis."

The recommended dosing regimen for Zirgan is 1 drop in the affected eye 5 times per day until the ulcer heals, and then 1 drop 3 times per day for 7 days. Trifluridine ophthalmic solution, which is commonly used for topical treatment of herpetic keratitis, is dosed at 1 drop every 2 hours while awake for a maximum of 9 drops daily until the ulcer heals. Zirgan will be supplied in a 5 gram tube and will be available by prescription through retail pharmacies.

"We anticipate Zirgan will be commercially available to US physicians in early 2010," noted Susan Benton, senior vice-president of sales and marketing for Sirion. "We're pleased to introduce this important treatment option for herpetic keratitis to the US," she continued, "especially since it has been the standard of care in the Europe for over 10 years. We believe it will provide patients and physicians with an effective, safe, and convenient treatment for herpetic keratitis."

Herpes simplex virus infections are very common, with nearly 60 per cent of the US population showing evidence of infection by age five. Approximately 1 per cent of infected patients develop ocular outbreaks, with 20,000 primary cases of ocular herpes diagnosed in the US each year. After the primary infection, ocular HSV typically becomes latent until triggers such as stress, UV radiation, and hormonal changes reactivate the virus and cause recurrent outbreaks. Those recurrences account for an additional 28,000 cases per year in the US. The risk of blindness increases with the number and severity of recurrences, making prompt treatment imperative to limit scarring and other more serious complications caused by herpetic ulcers.