NEI Clinical Studies
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Ganciclovir Implant Study for Cytomegalovirus Retinitis
To determine the therapeutic efficacy of a sustained-release intraocular drug delivery system for ganciclovir therapy of cytomegalovirus (CMV) retinitis in patients with acquired immunodeficiency syndrome (AIDS).
CMV retinitis occurs in 20 to 30 percent of patients with AIDS and is the leading cause of visual loss in these patients. At present, ganciclovir and foscarnet are the only drugs that have been approved by the U.S. Food and Drug Administration for the treatment of CMV retinitis. The therapeutic regimen for each drug consists of a 2-week induction period followed by daily maintenance intravenous infusions. Unfortunately, CMV retinitis usually progresses despite daily maintenance therapy, and both drugs are associated with significant systemic toxicity that often limits their therapeutic usefulness. As an alternative to intravenous administration, direct intravitreal injections of ganciclovir have been studied and have been shown to be effective in delaying the progression of CMV retinitis. The short half-life of the drug, however, necessitates one to two intraocular injections a week to maintain therapeutic levels. Widespread adoption of this technique has been limited because of the logistical difficulties and inherent risks associated with numerous intravitreal injections.
A drug delivery system capable of continuous delivery of ganciclovir into the vitreous cavity has been developed. The device consists of a 6-mg pellet of ganciclovir that is coated with a series of polymers with variable permeability to ganciclovir. The device is surgically implanted through the pars plana.
Thirty eyes of 26 patients with unilateral non-sight-threatening CMV retinitis were randomly assigned to one of two groups: (1) immediate therapy with a device designed to release ganciclovir into the vitreous cavity at a rate of 1 µg/h over approximately a 4-month period or (2) deferred treatment. In patients with bilateral non-sight-threatening CMV retinitis, one eye was randomly assigned to receive a ganciclovir implant with the other eye assigned to deferred treatment. (Note: The original trial design included a third randomized arm using a 2 µg/hour device. This arm was dropped for logistical reasons after enrolling two patients.)
Patients assigned to immediate treatment underwent surgery to implant the ganciclovir device within 48 hours of enrollment and baseline photographs. Postoperatively, patients were evaluated the next day, weekly for 2 weeks, and then every 2 weeks until progression of CMV retinitis occurred. At each examination, in both eyes, visual acuity with current correction and best correction was determined using Early Treatment Diabetic Retinopathy Study eye charts; intraocular pressure was determined; evidence of inflammation or cataract was evaluated; and all retinal findings were documented. Any adverse event considered even possibly related to the device or to the implantation procedure was documented. Standardized nine-field fundus photographs were taken at each 2-week visit. The ganciclovir implant was exchanged at 32 weeks or earlier if progression of CMV retinitis occurred.
The primary end point was time to CMV retinitis progression, defined as the time (days) from initiating therapy until the advancement of 750-µm over a 750 µm front of any border of any lesion was observed. Standardized nine-field photographs were taken at 2-week intervals and analyzed in a masked fashion by the Fundus Photograph Reading Center to determine evidence of CMV retinitis progression.
Secondary end points included time to development of CMV retinitis in the contralateral eye, time to development of visceral CMV, and time to death.
All patients must have had AIDS as defined by the Centers for Disease Control and Prevention and non-sight-threatening CMV retinitis (>3,000 µm from the fovea and >1,500 µm from the optic disc). Patients could not have been previously treated with systemic ganciclovir or foscarnet and must not have had evidence of other organ involvement with CMV. Patients must have had an absolute neutrophil count (ANC) greater than 1,000 cells/mL and a platelet count greater than 25,000/mm³.
Patient Recruitment Status
Recruitment began in October 1992 and was completed in December 1993.
Current Status of Study
Twenty-six patients (30 eyes) were enrolled. The median time to progression to retinitis was 15 days in the deferred treatment group (n = 16) versus 226 days in the immediate treatment group (n = 14). During the study, 39 primary implants and 12 exchange implants were placed in immediate-treatment eyes, deferred-treatment eyes that progressed, or contralateral eyes that developed CMV retinitis. Postoperative complications in the total series included seven late retinal detachments and one retinal tear without detachment. Final visual acuity was 20/25 or better in 34 of 39 eyes. The estimated risk of developing CMV retinitis in the fellow eye was 50 percent at 6 months. Biopsy-proven visceral CMV disease developed in 8 of 26 patients (31 percent). The median survival was 295 days.
The ganciclovir implant is effective for the treatment of CMV retinitis. Patients with unilateral CMV retinitis treated with the implant are likely to develop CMV retinitis in the fellow eye, and some patients will develop visceral CMV disease.
Martin DF, Parks DJ, Mellow SD, Ferris III FL, Walton RC, Remaley NA, Chew EY, Ashton P, Davis MD, Nussenblatt RB: Treatment of cytomegalovirus retinitis with an intraocular sustained-release ganciclovir implant: A randomized controlled clinical trial. Arch Ophthalmol 112: 1531-1539, 1994.
Robert B. Nussenblatt, M.D.
National Eye Institute
National Institutes of Health
Warren Grant Magnuson Clinical Center
Building 10, Room 10N202
10 Center Drive MSC 1858
Bethesda, MD 20892-1858
Telephone: (301) 496-3123
Last Updated: 9/23/98