The Vitrasert® implant was developed under Dr. Smith at his previous company, Control Delivery Systems, Inc. (now pSiveda).
Prior to the approval of the ganciclovir implant Vitrasert® in 1996, the treatment of choice for cytomegalovirus (CMV) retinitis was intravenous ganciclovir, a treatment noted for its toxicity, inconvenience, expense, and relative ineffectiveness. After 1 year of IV ganciclovir therapy, 40% of patients develop viral resistance. The Vitrasert® intraocular device consists of a 4.5 mg pellet of ganciclovir coated by a laminated system of biocompatible polymers. It is surgically implanted into the vitreous through the pars plana and attached to the sclera by a suture. The superiority of the implant is due to local delivery (to avoid the problems of the blood eye barrier) and, more importantly sustained release delivery to avoid sub-therapeutic troughs.
The Vitrasert® was compared to conventional IV dosing in 140 patients in a Phase III study. Experimental subjects were implanted with the device and control subjects received IV ganciclovir. The amount of ganciclovir used, compared to conventional dosing was reduced by a factor of 100,000, and the efficacy of treatment was significantly improved (p<0.0001 vs IV). Furthermore, after more than 15,000 devices have been implanted, the development of resistance during therapy has not been reported.