General Information

Zirgan is a topical gel formulation of ganciclovir. Ganciclovir is a guanosine derivative that, upon phosphorylation, inhibits DNA replication by herpes simplex viruses (HSV).

Zirgan is specifically indicated for the treatment of herpetic keratitis (dendritic ulcers).

Zirgan is supplied as a 0.15% gel designed for topical ophthalmic administration. The recommended initial dose is 1 drop in the affected eye 5 times per day (approximately every 3 hours while awake) until the corneal ulcer heals, and then 1 drop 3 times per day for 7 days.

Mechanism of Action

Zirgan (ganciclovir ophthalmic gel) contains the active ingredient, ganciclovir, which is a guanosine derivative that, upon phosphorylation, inhibits DNA replication by herpes simplex viruses (HSV). Ganciclovir is transformed by viral and cellular thymidine kinases (TK) to ganciclovir triphosphate, which works as an antiviral agent by inhibiting the synthesis of viral DNA in 2 ways: competitive inhibition of viral DNA-polymerase and direct incorporation into viral primer strand DNA, resulting in DNA chain termination and prevention of replication.

Side Effects

Adverse events associated with the use of Zirgan may include, but are not limited to, the following:

• blurred vision
• eye irritation
• punctate keratitis
• conjunctival hyperemia

Clinical Trial Results

The FDA approval of Zirgan was based on the following studies:

One open-label, randomized, controlled, multicenter clinical trial enrolled 164 subjects with herpetic keratitis. Zirgan was compared to acyclovir ophthalmic ointment 3% and evaluated for non-inferiority. Zirgan was determined to be non-inferior to acyclovir ophthalmic ointment. Clinical resolution (healed ulcers) at Day 7 was achieved in 77% of the Zirgan arm versus 72% of the acyclovir arm.

Three randomized, single-masked, controlled, multicenter clinical trials enrolled 213 total patients. Zirgan was agained compared to acyclovir ophthalmic ointment 3% in terms of non-inferiority. Zirgan was non-inferior to acyclovir ophthalmic ointment 3% in patients with dendritic ulcers. Clinical resolution at Day 7 was achieved in 72% of the Zirgan arm versus 69% of the acyclovir arm.