SILVER SPRING, Md. - An FDA panel on Friday strongly endorsed the safety and efficacy of Chiron Corp.'s Vitrasert Intravitreal Implant (ganciclovir, 4.5 mg) for treatment of AIDS patients with newly diagnosed CMV retinitis. It voted 6-1 to recommend that FDA approve the product.

Substantial issues were raised, however, about the potential consequences of administering local therapy in the absence of systemic therapy, the lack of coordination among FDA divisions in approving a possibly inadequate study protocol, and the degree of surgical expertise required to implant Vitrasert.

FDA and the panel, which consisted of the ophthalmic subcommittee of the Dermatologic & Ophthalmic Drugs Advisory Committee, with representation from the Antiviral Drugs Advisory Committee, started their discussion from the premise that Vitrasert is effective in treating CMV retinitis.

Two Phase III studies

Vitrasert consists of a nonerodable polymer-based sustained release package containing ganciclovir, which is surgically implanted in the posterior of the eye. CMV retinitis is an opportunistic eye infection reported in 15-40 percent of AIDS patients that leads to blindness if not treated.

CHIR presented two Phase III trials, a study of immediate versus deferred Vitrasert treatment conducted at two sites by the National Eye Institute and CHIR's multicenter trial of two doses of Vitrasert compared to intravenous ganciclovir.

Entry criteria for the CHIR trial were newly diagnosed CMV retinitis, no extraocular CMV manifestations requiring treatment, no contraindications to intraocular surgery and no contraindications to IV ganciclovir. The primary end point was time to progression of retinitis, defined as advancement of lesion border or new lesion.