Intraocular pharmacokinetics of a crystalline lipid prodrug, octadecyloxyethyl-cyclic-cidofovir, for cytomegalovirus retinitis.

PURPOSE: To evaluate the intraocular pharmacokinetics of octadecyloxyethyl-cyclic-cidofovir (ODE-cCDV) after intravitreal injection into rabbit eyes. METHODS: Twenty-seven New Zealand red rabbits (27 eyes) received intravitreal injections of (14)C-labeled ODE-cCDV (100 µg drug suspended in 5% dextrose), and ocular tissues were collected from 3 rabbits at each predetermined time point (1 h, 1 day, 3 days, 1 week, 2 weeks, 3 weeks, 5 weeks, and 9 weeks) after the injection. The eye globes were enucleated, and the vitreous, retina, and choroids were separated and harvested into pre-weighed scintillation vials. Levels of ODE-cCDV were measured by counting in a liquid scintillation counter, and pharmacokinetic (PK) parameters were determined. In addition, 3 eyes of 3 animals were used for autoradiography study at day 1, week 3, and week 6. RESULTS: ODE-cCDV in vitreous as a whole followed a 2-phase first-order elimination, whereas ODE-cCDV in retina and choroid manifested a nearly steady state during the first 3 weeks and then followed a first-order elimination with the apparent elimination half-life of 10.1 and 7.2 days. For vitreous, apparent elimination half-life was 25 days. However, the drug mean residence time was much longer in retina (17.6 days) and choroid (19.6 days) than that in the vitreous (11.6 days). The drug exposure to the retina [area under the curve (AUC) = 1120837.1 ng · day/mL] was greater than the exposure to the vitreous (AUC = 958645.8 ng · day/mL) and the choroid (AUC = 415407.47). CONCLUSION: A crystalline lipid prodrug, ODE-cCDV, has longer vitreous half-life than that in other ocular tissues due to its solid drug depot formation in vitreous. Over time, dissolved free ODE-cCDV from drug depot feeds and accumulates in the retina.

Intraocular properties of a repository urokinase receptor antagonist a36 Peptide in rabbits.

PURPOSE: To evaluate the intraocular properties of A36, a peptide that directly antagonizes the cell surface urokinase receptor and so prevents pericellular urokinase plasminogen activator activity. METHODS: A total of 41 rabbits were used. The toxicity study tested three doses of A36: 1 mg/ eye, 0.3 mg/eye, and 0.1 mg/eye. At 2 and 12 weeks, eyes were evaluated by ERG and histology. Pharmacokinetics were studied in rabbit eyes with the dose of 1 mg/eye in two different formulations: a micronized preparation and a non-micronized formulation. Eyes were enucleated at months 1, 2, 3, 4, and 5. Vitreous, retina, and choroid were collected separately for active A36 analysis. RESULTS: We did not find ocular toxicity with low and medium doses. At the highest dose, there was a transient toxicity at 2 weeks but was not notable at 3 months. The target choroid concentration of A36 was chosen as > or =100 nM. The micronized formulation at months 1, 2, and 3 combined, showed variable levels in the choroid giving 5/10 (50%) of the therapeutic level; the non-micronized formulation at months 4 and 5 combined, gave 6/7 (86%) of the therapeutic level, although this difference was not statistically significant. CONCLUSION: A36 appears to be long lasting; the non-micronized formulation of A36 gave concentrations above therapeutic level in the choroid at months 4 and 5. Optimization of the formulation of A36, particularly the particle size, may result in a promising new compound for exudative age-related macular degeneration treatment.

Intravitreal crystalline drug delivery for intraocular proliferation diseases.

PURPOSE: A long-lasting, slow-release, crystalline antiviral drug delivery system was initially reported using ganciclovir and cyclic cidofovir as the prototype compounds. The present study was undertaken to investigate the feasibility of applying this system to antiproliferative small molecules. METHODS: The crystalline lipid prodrugs of hexadecyloxypropyl-arabinofuranosylguanine 5'-monophosphate (HDP-P-AraG), hexadecyloxypropyl 5-fluoro-2'-deoxyuridine cyclic 3',5'-monophosphate (HDP-cP-5-F-2dUrd), and hexadecyloxypropyl 5-fluoro-2'-deoxyuridine 5'-monophosphate (HDP-P-5-F-2dUrd) were synthesized from their parent compounds arabinofuranosylguanine (AraG) and 5-fluoro-2'-deoxyuridine (5-F-2dUrd). All three compounds were tested at escalating doses in rabbit eyes. Only one eye of each animal was injected with test compound, and the fellow eye was injected with 5% dextrose as the control. The injected eyes were monitored by slit lamp, a handheld tonometer, indirect ophthalmoscopy, electroretinography (ERG), and histology. The selected doses were used for efficacy study with the rat CNV model or the rabbit PVR model. RESULTS: The highest nontoxic dose for HDP-P-AraG was 75 microg/eye, and was 70 and 210 microg/eye for HDP-P-5-F-2dUrd and HDP-cP-5-F-2dUrd, respectively. All compounds demonstrated a localized depot of crystalline aggregate in the vitreous with a clear view of vitreous and retina elsewhere. The drug depot of HDP-P-AraG was visible for 4 to 5 weeks; HDP-P-5-F-2dUrd, 8 to 10 weeks; and HDP-cP-5-F-2dUrd longer than 14 weeks. The treatment study showed HDP-P-AraG led to 33% reduction in CNV in the rat (P = 0.015), and HDP-cP-5-F-2dUrd provided 100% prevention of trauma-induced PVR in the rabbit (P = 0.046). The pretreatment study demonstrated a significant protection against intraocular proliferation compared with the 5-FU in a parallel study (P = 0.014). CONCLUSIONS: The intravitreous injectable lipid prodrugs of AraG and 5-fluoro-2'-deoxyuridine could be long-lasting, slow-release, antiproliferative compounds to treat unwanted intraocular proliferation.

Toxicity and intraocular properties of a novel long-acting anti-proliferative and anti-angiogenic compound IMS2186.

PURPOSE: To investigate the intraocular properties and toxicity of IMS2186, a small molecule developed as an anti-choroidal neovascularization (anti-CNV) drug. MATERIALS AND METHODS: Cellular toxicity and mechanism of action was tested on cell lines in vitro. Intraocular studies used rabbits for drug dissolution as well as toxicity and rats for the treatment study as well as the toxicity confirmation study. Rabbits' eyes were injected with 2.5 mg of IMS2186 and observed for 36 weeks. Laser-induced CNV in rats was treated with IMS2186, Kenalog, or phosphate-buffered saline (pBS). Fluorescein angiography (FA) and immunohistochemical processing of the globes was performed. RESULTS: The anti-proliferative IC(50) of IMS2186 for human fibroblast cells was 1.0-3.0 microM and 0.3-3.0 microM for human cancer cells; the IC(50) of IMS2186 to inhibit endothelial tube formation was 0.1-0.3 microM. The IC(50) of IMS2186 for inhibiting the production of pro-inflammatory cytokines was 0.3-1 microM. The IC(50) of IMS2186 for inhibiting macrophage migration was 1 micrM. These biological properties were not species specific. IMS2186 can be formulated as a suspension for long-lasting release and when delivered intraocularly, no intraocular toxicity was observed by slit lamp exam, fundus exam, intraocular pressure measurements, or by electroretinography. FA showed a reduction in the leakage in eyes treated with IMS2186 and triamcinolone acetonide; DAPI staining also showed significantly less cellularity in IMS2186-treated lesions as compared to PBS (p = 0.0025). CONCLUSION: IMS2186 may be a safe intraocular therapeutic agent for intraocular proliferation and angiogenesis.

Discrepancy between fluorescein angiography and optical coherence tomography in detection of macular disease.

PURPOSE: To compare high-resolution optical coherence tomography (OCT) and fluorescein angiography (FA) in detection of macular edema (ME) of various etiologies. METHODS: In a retrospective study over a 12-month period at one retina center, data for consecutive eyes that had undergone simultaneous conventional FA (HRA; Heidelberg Engineering, Vista, CA) and StratusOCT (Carl Zeiss Meditec, Dublin, CA) to rule out ME were reviewed. A subset of patients underwent additional examination with extremely high-resolution (6-microm)/ultrahigh-speed spectral OCT/scanning laser ophthalmoscopy (OTI, Inc., Toronto, Ontario, Canada). RESULTS: Of 1,272 eyes, 1,208 (94.97%) had the finding of ME or subretinal fluid confirmed by both techniques. There were 49 eyes (3.86%) for which FA showed dye leakage in the macular area and OCT showed normal foveal contour. Of 10 eyes in this group that underwent imaging with ultrahigh-speed spectral OCT/scanning laser ophthalmoscopy, 8 had subtle diffuse lucencies in the retina. For 15 eyes (1.17%), OCT showed intraretinal and subretinal fluid, which was missed by FA. CONCLUSIONS: Both FA and high-resolution OCT are highly sensitive techniques and correlate well in detection of ME. However, there is a small chance that when performed alone they might miss existing subtle ME.

Comparison of visual acuity in macular degeneration patients measured with snellen and early treatment diabetic retinopathy study charts.

PURPOSE: To compare the measurements of visual acuity (VA) results measured with Snellen and Early Treatment Diabetic Retinopathy Study (ETDRS) charts in eyes with and without age-related macular degeneration (AMD). DESIGN: Cross-sectional study. PARTICIPANTS: One hundred four participants (190 eyes) selected from a university retina practice; 80 participants (142 eyes) had some degree of AMD. METHODS: Visual acuity was measured in each patient using standard procedure with both Snellen and ETDRS charts in random order. Statistical analysis of the results was performed. MAIN OUTCOME MEASURES: Difference in VA measured by both charts in logarithm of minimal angle of resolution (logMAR) notations. RESULTS: Overall, the mean Snellen VA was 0.78 logMAR (= 20/120), and the mean ETDRS VA in the same eye was 0.54 logMAR (= 20/70; P<0.001). In the low vision group (<20/200), represented by patients with AMD, the average difference in number of lines was considerably larger than in the good vision range (>20/30). On average, 20/200 on Snellen was 20/95 on ETDRS (>3 lines difference), and 20/30 on Snellen was 20/25 on ETDRS (<1 line difference). CONCLUSION: Our results show poor agreement between the Snellen and ETDRS charts, and it was more pronounced in the group with poor vision. The ETDRS measurements yielded better VA, particularly in participants with vision <20/200 (representing more advanced AMD patients). We suggest taking these findings into consideration when comparing outcomes in clinical practices (which typically measure VA using standard Snellen charts) with outcomes from clinical trials (which typically measure VA using ETDRS charts).

Intraocular properties of an alkoxyalkyl derivative of cyclic 9-(S)-(3-hydroxyl-2-phosphonomehoxypropyl) adenine, an intravitreally injectable anti-HCMV drug in rabbit and guinea pig.

PURPOSE: The aim of this study was to investigate intraocular properties and determine the highest nontoxic dose of hexadecyloxypropyl-cyclic-HPMPA (HDP-cHPMPA), a novel, potent, intravitreally injectable, slow-releasing crystalline drug for long-acting treatment of cytomegalovirus (CMV) retinitis. METHODS: Various concentrations of HDP-cHPMPA were first studied in vitro in a human foreskin fibroblast (HFF) cell line infected with human cytomegalovirus (HCMV) to determine the EC50. In vivo, 9 pigmented rabbits and 3 doses (55, 100, and 550 microg/eye) were tested in triplicate in 1 eye of each animal. The eyes were monitored with slit lamp, tonopen, indirect ophthalmoscopy, electroretinography (ERG), and histology. A confirmation toxicity study with the dose equivalent to the highest nontoxic dose in rabbit was performed in 9 guinea pig eyes (a second species) to study the potential adverse effect on intraocular pressure (IOP). RESULTS: In vitro testing in HFF cells showed an EC50 against HCMV of 0.02 microM, which is 75- and 60-fold greater than that of ganciclovir and cidofovir, respectively. All eyes injected with 550 microg/eye and 1 eye injected with 100 microg/eye of HDP-cHPMPA showed toxicity clinically (e.g., vitreous cells, disc edema, and retinal inflammation) as well as histologically (e.g., inflammatory cells in iris, vitreous, and retinal layers with disorganization). None of the eyes injected with 55 microg/eye of HDP-cHPMPA showed toxicity clinically (including ERG) and histologically. The equivalent dose (9.2 microg/eye) in the guinea pig eyes did not show toxicity either, including IOP evaluation (P > 0.05 at all time points after injection). CONCLUSIONS: Intravitreal injection of the highest nontoxic dose of 55 microg/eye of HDP-cHPMPA in rabbit eyes yields a calculated intravitreal concentration of 65 microM, which is 3250-fold greater than the EC50 against HCMV (0.02 microM). Also, it does not cause hypotony in rabbit and guinea pig eyes and has a vitreous residence time of over 4 months.

Standardized visual acuity results associated with primary versus secondary bevacizumab (avastin) treatment for choroidal neovascularization in age-related macular degeneration.

PURPOSE: To compare standardized visual outcomes and macular thickness changes associated with primary and secondary bevacizumab (Avastin; Genentech, Inc., South San Francisco, CA) therapy for choroidal neovascularization (CNV) in age-related macular degeneration (AMD). METHODS: Eighteen eyes received primary bevacizumab treatment; 20 eyes received pegaptanib (Macugen; Eyetech/OSI Pharmaceuticals, New York, NY) as initial treatment followed by bevacizumab therapy. Both medications were injected at 6-week intervals. Best-corrected visual acuity was measured with the ETDRS chart. Three- and 6-month data were analyzed for all eyes. RESULTS: Mean visual acuity improvement in the primary bevacizumab treatment cohort was 1.5 ETDRS lines at 3 months (P = 0.0009) and 2.2 ETDRS lines at 6 months (P=0.0004) compared with -0.4 ETDRS line at 3 months (P=0.27) and 0.2 ETDRS line at 6 months (P=0.70) in the secondary bevacizumab treatment group. Mean decrease in retinal thickness was also higher in the primary bevacizumab treatment group (90.9 microm [P=0.0037] vs 43.8 microm [P=0.13], respectively) than in the secondary bevacizumab treatment group (73.72 microm [P=0.051] vs 33.0 microm [P=0.21], respectively) at 3 months and 6 months. CONCLUSION: Primary bevacizumab therapy resulted in significantly greater visual improvement than secondary bevacizumab treatment at 3 months or 6 months. To our knowledge, this is the first report comparing primary bevacizumab treatment of CNV in AMD with secondary bevacizumab treatment after multiple pegaptanib injections.

Evaluation of subretinal triamcinolone acetonide in patients with exudative age-related macular degeneration.

PURPOSE: The aim of this paper was to present the results of subretinal delivery of triamcinolone acetonide (TCA) in humans with choroidal neovascularization (CNV) caused by age-related macular degeneration (AMD). METHODS: Twenty two (22) eyes of 22 patients underwent pars plana vitrectomy with subretinal TCA administration. Two milligrams (2 mg) of preservative-free TCA were delivered through a 32-gauge automatic subretinal injector in 20 microL of volume. Visual acuity, fluorescein angiography (FA), and intraocular pressure (IOP) were recorded and compared pre- and postoperatively. RESULTS: Preoperative average+/-standard deviation visual acuity in the treated eye was 1.408+/-0.129 (logMAR; median 20/400) and 1.403+/-0.114 (logMAR; median 20/300) postoperatively (P=0.51). The mean area of pre- and postoperative FA leakage in the operated eyes was 21.31+/-1.125 and 19.29+/-1.108 mm2, respectively (P=0.04). The average IOP value before treatment was 15.3+/-0.78 mmHg. Three (3) months after surgery, it was 20.5+/-2.04 mmHg (P=0.02). Six (6) months and 1 year after surgery, the average IOP was 17.0+/-0.66 mmHg (P=0.9) and 15.6+/-1.02 mmHg (P=0.6), respectively. CONCLUSIONS: Subretinal TCA stabilizes visual acuity, decreases FA leakage in eyes with CNV owing to AMD, and does not increase IOP, as seen with intravitreous injections.