3- and 6-week visits, suggesting that 6 weeks might be too long for an optimal initial injection interval. A similar phenomenon was observed after the second injection of bevacizumab. Combining photocoagulation with bevacizumab did not result in any apparent short-term benefit.

This study also monitored for any possible adverse effects, although the safety evaluation was limited by the small sample size and short follow-up duration. In the subjects treated with bevacizumab, there were several cases of systemic cardiovascular or renal adverse effects (including two cases of myocardial infarction), all of which occurred in subjects with related pre-existing medical conditions. However, the sample sizes were too small to attribute cause of any systemic events to the drug. In addition, there was 1 case of injection-related endophthalmitis in 185 injections, but no important ocular complications attributable to the bevacizumab.

This study therefore indicates a short-term response in reduction of retinal thickness from bevacizumab injection. Definitive determinations of a clinically meaningful benefit of intravitreal bevacizumab for DME will require a large phase III randomized clinical trial. This will also be required to provide definitive conclusions regarding safety. No significant safety concerns have arisen to date, but most of the published data on bevacizumab and diabetic eye disease is limited to retrospective case series and anecdotal case reports.

RANIBIZUMAB IN DIABETIC MACULAR EDEMA

Nguyen and colleagues conducted an open-label study (Ranibizumab for Edema of the mAcula in Diabetes: A Phase 1 Study – the READ-1 Study) to investigate the effect of intravitreal injections of ranibizumab in patients with DME (109). Intraocular injections of 0.5 mg of ranibizumab were administered at entry to the study and at 1, 2, 4, and 6 months after entry. The injection regimen was selected to assess the effect of 3 monthly injections and then determine the impact of increasing the time interval between injections to 2 months for the last 2 injections. The primary outcome measure was foveal thickness measured by OCT at 7 months compared to baseline. Secondary outcome measures were macular volume measured by OCT and VA measured by the protocol of the Early Treatment Diabetic Retinopathy Study (ETDRS) at 7 months compared to baseline, and ocular and systemic safety.

Among the 10 subjects (5 men and 5 women) initially enrolled, pertinent baseline characteristics included: 8 eyes that had received at least two sessions of focal/grid laser photocoagulation not less than 5 months prior to study entry (range 5–120 months), 3 eyes that had received intraocular steroids not less than 10 months prior to entry (range 10–20 months), and a mean foveal thickness of 503 ± 115 m (range 326–729 m) at baseline, indicating the presence of severe, chronic DME that was poorly responsive to standard therapies.

Effect on Foveal Thickness and Macular Volume

Compared to baseline, mean foveal thickness was reduced by 246 m at the primary endpoint of the study (7 months after the first ranibizumab injection), representing an elimination of 85% of the excess foveal thickness that had been present at baseline. In addition, mean macular volume was reduced from 9.22mm3 at baseline to 7.47mm3 at 7 months, a

Fig. 3. Horizontal cross sectional optical coherence tomography (OCT) scans at all time points for patients #8 and #10 to illustrate two patterns of response over time. Ranibizumab injections were administered at baseline, month 1 (M1), month 2, month 4 (M4), and month 6 (M6). Seven days after the first intraocular injection of 0.5mg of Ranibizumab (D7), patient 8 showed an immediate improvement in the appearance of the OCT scan with less intraretinal cystoid spaces and a reduction in excess retinal thickening. Patient 8 continued to have a reduction in excess retinal thickness throughout the course of the study. By month 7 (M7), which was the primary endpoint of the study, patient 8 had eliminated most of the excess retinal thickness. Like patient 8, patient 10 also showed substantial improvement at D7 compared to baseline with resolution of several large cysts. At M4 and M6, 2 months after the third and fourth injections, respectively, the scan showed significant deterioration in patient 10. However, 1 month after injection at M4 and M6, there was marked improvement at M5 and M7, respectively.

reduction of 1.75 mm3 which was statistically significant (P = 0.009). This reduction constituted 77% of the excess macular volume that was present at baseline. OCT scans from two subjects whose DME showed responses to ranibizumab are shown in Fig. 3.

Effect on Visual Acuity

Throughout each study time point, mean and median visual acuities were better than those at baseline. At the primary endpoint (7 months after the initial ranibizumab injection), mean and median visual acuity improved by 12.3 and 11 letters in the initial 10 subjects, which represents an improvement of a little more than 2 lines. Figure 4 provides updated visual acuity data on the final 18 subjects who participated in the READ study and shows the mean and median visual acuity improved by 10 letters (2 lines) at 7 months.

In this study cohort, there was a strong correlation (R2 value of 0.78) between visual acuity and foveal thickness as measured by OCT. However, the rate of change of these two outcome measures was different, and rapid changes in foveal thickness were

Fig. 4. Mean and median change in visual acuity from baseline at each study visit after intravitreal ranibizumab for diabetic macular edema. Mean change (squares) and median change (diamonds) in visual acuity were measured in the number of letters that were read on the Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity chart. The arrows show times of intraocular injection of 0.5 mg of Ranibizumab. At the primary endpoint (7 months) there was an improvement of 10 letters in mean visual acuity and 10 letters in median visual acuity among the 18 participants.

associated with more gradual improvements in visual acuity. Figure 5 shows the reduction in excess retinal thickness through 7 months of follow-up in the final 18 participants. Further studies are underway to investigate the correlation between visual acuity and retinal thickness as measured by OCT.

Intraocular injections of ranibizumab were tolerated well with no ocular inflammation or adverse events. There were no systemic adverse events; no thromboembolic events, cerebral vascular accidents, nor myocardial infarctions. Capillary nonperfusion was measured by image analysis on baseline and month 6 fluorescein angiograms with the investigator masked with respect to time point. The mean area of nonperfusion was 0.19812 disc areas at baseline and 0.19525 at 6 months. Therefore, no significant change in capillary nonperfusion was seen throughout the study.

The READ-2 Study, a multi-center phase 2 randomized clinical trial investigating the bioactivity and safety of ranibizumab for DME is underway in the United States. The three treatment arms in the study include: (1) ranibizumab, (2) ranibizumab with focal laser photocoagulation, and (3) focal laser photocoagulation with deferred ranibizumab. Preliminary results are expected in 2008.

Fig. 5. The mean excess foveal thickness at each study visit after ranibizumab for diabetic macular edema. Each bar represents the mean or median value for excess foveal thickness for all 18 patients at the designated study visit. The arrows show when intraocular injections of 0.5mg of ranibizumab were administered. Compared to baseline, foveal thickness was reduced by 241 m at the primary endpoint of the study, constituting elimination of over 80% of the excess foveal thickness that had been present at baseline.

Another clinical trial investigating ranibizumab for diabetic retinopathy is also under way, A double-masked, multicenter, phase II study assessing the safety and efficacy of ranibizumab (0.3 and 0.5 mg intravitreal injections) compared with non-treatment control (sham injection) for the treatment of DME is recruiting patients in the United States as well as in Europe, New Zealand and Asia.

The primary objective is to explore whether ranibizumab treatment is superior to non-treatment in reducing macular edema from baseline to Month 6 in patients diagnosed with DME. Results are expected in 2009.

Finally, the Diabetic Retinopathy Clinical Research Network (DRCR.net) is conducting a randomized, multicenter clinical trial investigating intravitreal ranibizumab or triamcinolone acetonide in combination with laser photocoagulation for diabetic macular edema. This study will involve subjects with DME involving the center of the macula (with OCT central subfield thickness greater than 250 ) responsible for visual acuity of 20/32 or worse. The objective is to determine which is a better treatment approach for DME: laser alone, laser combined with intravitreal triamcinolone, laser combined with intravitreal ranibizumab, or intravitreal ranibizumab alone. Patient recruitment for this study began in March 2007. The primary efficacy outcome will be visual acuity at 12 months adjusted for the baseline acuity, with secondary outcomes being the change