Germaine Bergeron-Lynn

Efficacy of Prinomastat® (AG3340), a matrix metalloprotease inhibitor, in treatment of retinal neovascularization

Purpose. To study the activity of the novel anti-angiogenic compound AG3340 (Prinomastat ®) , a selective inhibitor of matrix metalloproteases, in an animal model of retinal neovascularization. Methods. C57BL/6J mice were used to produce oxygen-induced retinal neovascularization. Mice were exposed to room air from birth (P0) to postnatal 7 days (P7) and to hyperoxia (75% oxygen) for the next 5 days. On postnatal day 12 (P12) the animals were returned to the room air and were treated until postnatal day 16 (P16) with intraperitoneal injections of AG 3340. Four groups were assigned: no drug, 1.6 mg/kg/day, 16 mg/kg/day and 48 mg/kg/day. On day 17 (P17) the animals were sacrificed and the eyes prepared for histological sectioning. Preretinal neovascularization was assessed by counting neovascular nuclei of endothelial cells in the preretinal side of the internal limiting membrane (ILM). The use of animals for this study complies with the ARVO guidelines for animal research. Results. AG3340 administered systemically by intraperitoneal injections inhibited hypoxia-induced retinal neovascularization. The inhibition was dose dependent with highly significant decrease of neovascular nuclei counts among eyes treated with 0, 1.6 mg/kg, 16 mg/kg and 48 mg/kg doses. There appears to be a saturation effect of inhibition at the level of 70% at the two highest doses of 16 mg/kg and 48 mg/kg. Conclusions. AG3340 administered systemically significantly inhibits oxygen-induced retinal neovascularization in an animal model and appears to be a promising candidate for the treatment of neovascular retinal diseases.

Preventive Versus Treatment Effect of Ag3340, a Potent Matrix Metalloproteinase Inhibitor in a Rat Model of Choroidal Neovascularization

PURPOSE AG3340 (prinomastat) is a nonpeptidic, small-molecular-weight, synthetic matrix metalloproteinase inhibitor (MMPI) with selective inhibitory action of MMP-2, MMP-9, MMP-3, and MT-MMP1. We evaluated AG3340 injected intravitreally to treat choroidal neovascularization in a laser induced rat CNV model. METHODS In the pretreatment group, the drug was injected the same day after induction of choroidal neovascularization by diode laser. In the treatment group, the drug was injected 2 weeks after induction of choroidal neovascularization (CNV). Fluorescein and indocyanine green angiography were performed to evaluate CNV. ERG recordings and histology were performed to assess toxicity and the CNV lesions. RESULTS When used at the time of CNV induction, 62.8% of lesions in control versus 22.8% of the laser lesions in treated eyes developed CNV (p < 0.0001). The invading fibrovascular complex was thicker in the control eyes than that in the treated eyes. No signs of toxicity were detected. When used to treat established CNV, the percentage of leakage in treated and control eyes were 54.1% and 58.9% respectively (p > 0.05). Prinomastat was effective when given at the time of induction of CNV in the rat model. Administration of prinomastat 2 weeks after laser induction did not show efficacy. CONCLUSION Prinomastat was active in the earliest stages of experimental CNV. It might be best used in combination with photodynamic therapy to inhibit recurrence of CNV from temporarily closed new vessels.

Evaluation of a novel lipid prodrug for intraocular drug delivery: effect of acyclovir diphosphate dimyristoylglycerol in a rabbit model with herpes simplex virus-1 retinitis.

BACKGROUND Acyclovir diphosphate dimyristoylglycerol is a lipid prodrug of acyclovir that forms liposomes and provides substantial activity against herpes simplex virus, acyclovir-resistant strains of herpes simplex virus, and human cytomegalovirus. We therefore tested this promising new drug in a rabbit model of herpes simplex retinitis. METHODS A total of 22 pigmented rabbits were pretreated with either acyclovir diphosphate dimyristoylglycerol, ganciclovir, acyclovir, or buffer. Retinae then were inoculated with herpes simplex virus-1 or buffer 1 week after the injection of drug. In another experiment we compared the effects of acyclovir diphosphate dimyristoylglycerol and acyclovir diphosphate dioleoylglycerol on the optical clarity of vitreous. RESULTS Animals injected intravitreally with acyclovir diphosphate dimyristoylglycerol showed retinitis that was less severe than that in animals injected with ganciclovir, acyclovir, and buffer; differences in grading scores of the retinitis between animals injected with acyclovir diphosphate dimyristoylglycerol and those injected with buffer were statistically significant (P = 0.0015). Vitreous and optical media became clear 4 days after acyclovir diphosphate dioleoylglycerol injection compared with 10 days after with acyclovir diphosphate dimyristoylglycerol injections. CONCLUSION Acyclovir diphosphate dimyristoylglycerol had prolonged antiviral activity against herpes simplex virus-1 retinitis in a rabbit model. This drug delivery system, modified to improve optical clarity, may allow long-acting intravitreal treatment of cytomegalovirus retinitis and other retinal diseases.

Human immunodeficiency virus type 2 (HIV-2) vector-mediated in vivo gene transfer into adult rabbit retina

Purpose. To evaluate the potential usefulness of HIV-2 viral vector in in vivo retinal gene therapy. Methods. An HIV-2 virus based viral vector was constructed and administered subretinally and intravitreally into rabbit eyes. After viral vector administration, the eyes were closely monitored for any adverse effects by slit lamp, indirect ophthalmoscopy, and fundus photography. Eyes were enucleated at specified times after injection, and reporter gene expression was identified within cell types and graded by the pattern and distribution of staining cells using fluorescent microscopy. Results. The HIV-2 viral vector demonstrated efficient gene transfer into many types of retinal cells without apparent cytotoxicity. Notably with subretinal injection, the HIV-2 vector resulted in higher efficiency of transduction of photoreceptor cells than of the other cell types (p < 0.05). With the intravitreal administration of HIV-2 viral vectors, cellular transduction and transgene expression in the ganglion cell layer was the dominant finding. Conclusions. HIV-2 viral vector may be a useful gene delivery vehicle for retinal photoreceptor cells and ganglion cells. It deserves further exploration to investigate its potential merit in long term gene therapy protocols and in other animal species.

Evaluation of intraocular pharmacokinetics and toxicity of prinomastat (AG3340) in the rabbit.

To determine the ocular pharmacokinetics, physiological and histological effects of prinomastat (a matrix metalloprotease inhibitor), a total of seventy-seven eyes of New Zealand White rabbits received intravitreous and subtenon injections of prinomastat or of acidified water vehicle as control, Doses of 0.5 mg in 0.05 mL of prinomastat or acidified water were used for intravitreal injection. For the subtenon injections, doses of 5 mg prinomastat in 0.5 mL of acidified water were administered in the superotemporal quadrant. Intraocular pharmacokinetics were determined by analyzing vitreous samples at different postinjection time points using Liquid Chromatography-Mass Spectroscopy/Mass Spectroscopy (LC-MS/MS). The toxicity was evaluated by biomicroscopy, electroretinography (ERG), pneumatonometry, and histology. No toxicity was found with either administration method. At day 14 after intravitreal injection, levels of prinomastat in the vitreous and choroid were 1.4 ng/mg and 7.8 ng/mg, respectively. The retinal levels of prinomastat were 22 ng/mg at 24 hr and dropped below 1 ng/mg at 48 hr. Prinomastat remained well above minimum effective concentration in the choroid for at least four weeks after a single intravitreal injection, suggesting that local intravitreal injection may have potential in treating choroidal neovascularization.

Intraocular Tolerance Of Perfluorooctylbromide (perflubron)

Purpose To determine the intraocular tolerance of perfluorooctylbromide (perflubron) in vitrectomized rabbit and pig eyes and evaluated its use as a vitreous substitute in vitreoretinal surgery. Methods Pars plana vitrectomy was performed on 33 Dutch pigmented rabbits and 11 micro mini pigs. After vitrectomy the eyes were filled with perflubron for 2 hours, 1 week, 2 weeks, 1 month, and up to 6 months. Results No clinical, electroretinographic, or light and electron microscopic evidence of adverse effects on the retina and lens were observed. Perflubron emulsified and dispersed into small bubbles after 2–3 weeks. The lens showed mild posterior subcapsular cataracts in pig eyes after long-term retention of perflubron. Conclusion These findings indicate that perflubron is safe for intraoperative and for longterm use intravitreally. However, emulsification and the breakdown into small bubbles limits the view of the retina when perflubron is used as a long-term tamponade.

Treatment of herpes retinitis in an animal model with a sustained delivery antiviral drug, liposomal 1-O-octadecyl-SN-glycerol-3-phosphonoformate.

PURPOSE To evaluate the clinical treatment efficacy of a long-lasting intravitreous injectable anti-cytomegalovirus (CMV) liposomal drug, 1-O-octadecyl-sn-glycerol-3-phosphonoformate (ODG-PFA). METHODS Sixty-four pigmented rabbits were used for evaluation of the potency and duration of action of ODG-PFA after intravitreal injection using a herpes simplex virus (HSV)-1 retinitis model. For the potency evaluation, liposomal ODG-PFA was injected into rabbit vitreous at the same time that HSV-1 virus was inoculated onto the retina (simultaneous treatment). For the duration evaluation, ODG-PFA was injected days or weeks before inoculation (pretreatment). Retinitis was clinically graded by indirect ophthalmoscopy, and the retinitis scores were compared across the treatment and control groups. RESULTS Simultaneous treatment study revealed that ODG-PFA was much more potent than its parent compound, foscarnet (P = 0.0027). Pretreatment study indicated that ODG-PFA possesses a much longer antiviral effect (at least 2 weeks) than foscarnet after a single intravitreal injection. CONCLUSION Liposomal ODG-PFA is a potent long-lasting intravitreal injectable antiviral compound that may be an ideal alternative for treatment of CMV retinitis in patients with acquired immunodeficiency syndrome.

Ganciclovir release rates in vitreous from different formulations of 1-O-hexadecylpropanediol-3-phospho-ganciclovir.

PURPOSE To determine the optimal formulation of lipid prodrug, 1-O-hexadecyloxypropyl-phospho-ganciclovir (HDP-P-GCV), for intravitreal delivery. METHODS Equal concentrations of crystalline or liposomal HDP-P-GCV were exposed to rabbit whole vitreous, core vitreous, peripheral vitreous, human plasma, and heat inactivated rabbit vitreous, and the samples were incubated at 37 degrees C for one week. Aliquots were taken at day 1, 2, 3, and 7 and subjected to HPLC analysis for conversion to GCV. RESULTS The resultant concentration of GCV from crystalline HDP-P-GCV in vitreous was 198 +/- 49 microM (n = 3) at day 1 and 1253 +/- 248 microM (n = 3) at day 7. The resultant concentration of GCV from the liposomal formulation of HDP-P-GCV in vitreous was much lower, yielding a concentration of 66 +/- 7 microM (n = 3) at day 1 and 243 +/- 39 microM (n = 3) at day 7 (P < 0.001, t Test). When the crystalline HDP-P-GCV was incubated with heat-inactivated vitreous, the detectable GCV concentrations were low (22 microM) and did not increase over time. The concentration of GCV detected from the crystalline HDP-P-GCV in the core vitreous was 19.69 +/- 3.84 microM (n = 3) at day 1 and 1537.36 +/- 177.14 microM (n = 3) at day 7. The concentration of GCV released from crystalline HDP-P-GCV in peripheral vitreous was 32.86 +/- 5.07 microM (n = 3) at day 1 and 1805.78 +/- 327.94 microM (n = 3) at day 7. Detectable GCV concentration from both core and peripheral vitreous samples increased over time, however, the magnitude of GCV release from peripheral vitreous samples was higher (P < 0.05, t Test). CONCLUSION In vitreous, HDP-P-GCV as a crystalline formulation was converted to GCV more rapidly than liposomal formulation of HDP-P-GCV. Vitreous cells may play an important role in the metabolism of either formulation of HDP-P-GCV delivered into vitreous.

THE AGAR SANDWICH TECHNIQUE FOR RETINAL BIOPSY PROCESSING

Background The authors developed an agar sandwich technique for retinal biopsy processing. This tissue agar embedding technique allows for a rapid and reliable method to handle and transport retinal biopsies from the operative field to the histology laboratory. Methods Biopsies from rabbit retinas infected with herpes simplex virus, epiretinal membranes from patients with macular pucker, and retinas from patients with acute retinal necrosis were studied. Each retinal biopsy was fixed, mounted on an agar disc, and covered with liquid agar. Light microscopy, electron microscopy, immunocytochemistry, and polymerase chain reaction were employed on the agar-embedded tissue. Results The tissues remained mounted in the agar sandwich and maintained their orientation throughout the processing. The morphologic integrity, histologic characteristics, antigenic properties, and DNA quality all were preserved using the agar sandwich technique. Conclusion The agar sandwich technique is an efficient and simple technique for handling small biopsy specimens that require various analyses.

An animal model of focal, subacute, viral retinitis.

To study local intravitreal therapies for retinitis due to herpes viruses, an animal model of focal, subacute, relatively nonlethal herpes family retinitis is needed. Herpes simplex virus type 1 (HSV-1) was injected into the subretinal space of 33 Dutch pigmented rabbit eyes. The animals were observed for up to 42 days after the inoculation. All inoculated eyes developed a focal, enlarging area of retinitis in a predictable manner, showing focal enlarging areas of retinal opacification and necrosis with variable retinal hemorrhage. In the inoculated eyes, retinal detachment developed in all animals within 21 days; 33% of the animals developed focal retinitis in the uninoculated eye. Histologic examination showed encephalitis to be present in 11 (73%) of the 15 animals studied after 1 week. This model may be used to evaluate the therapeutic efficacy of new antiviral agents and modalities in the treatment of herpes family viral retinitis. The model is most similar to herpes simplex or zoster retinitis in humans, but also shares some similarities (and differences) with cytomegalovirus (CMV) retinitis in humans.