Table 3.6 List of the leading anti-VEGF agents under investigation for the treatment of DME

3.3.2.2 Intravitreal Anti-VEGF

Several investigations into the pathological features of diabetic retinopathy have elucidated a central role of vascular endothelial growth factor (VEGF) in promoting DME. VEGF is a homodimeric protein that stimulates vascular endothelial cell growth and induces vascular permeability [88]. The most studied anti-VEGF agents used are ranibizumab (Lucentis®), bevacizumab (Avastin®), and pegaptanib sodium (Macugen®). Recent encouraging results have highlighted the role of aflibercept (Table 3.6).

Ranibizumab (Lucentis®, Genentech, Inc., South San Francisco, CA) is a humanized antibody that binds to and inactivates all isoforms of VEGF-A and their degradation products with biological activity [88]. Ranibizumab has received FDA and EU approval for the treatment of age-related macular degeneration, macular edema secondary to retinal vein occlusion, and DME. Several randomized clinical trials

h

Fig. 3.21 (a–d) Diabetic macular edema with clusters of hard exudates, intense fluorescein leakage, and increased retinal leakage, more evident in the nasal area. (e–h) Four months later, after grid laser photocoagulation and three monthly injections, an improvement in retinal exudation (e), fluorescein leakage (f, g), and intraretinal thickening (h) is clearly visible

evaluated the efficacy and safety of intravitreal ranibizumab (IVR) as monotherapy, compared to laser or placebo, and as an adjunctive treatment to macular photocoagulation or vitrectomy (Fig. 3.21).

As a monotherapy, the effectiveness of IVR has been evaluated compared to sham therapy [89–91]. The earlier results emerged in 2006 from a small, nonrandomized, phase I, clinical trial (READ-1 study) [89]. Ten patients with chronic DME were treated with 0.5 mg IVR, reaching a significant BCVA gain and CRT decrease and suggesting a potential therapeutic role of IVR. A larger multicenter, phase II, sham-controlled, double-masked RCT (RESOLVE study) elucidated the efficacy and safety of IVR in a 12-month follow-up [90]. Enrolled subjects were randomly assigned to placebo or IVR, low (0.3 mg) or high (0.5 mg) dosing, according to the following strategy: 3 monthly injections and then pro re nata (PRN) IVR. The 12-month results showed a BCVA increase of 10.3 letters in the IVR groups and a BCVA decrease of 1.4 letters in the sham group, while an improvement of ten or more letters was noted in the 60.8 % of IVR arm and in the 18.4 % of placebo.

A decrease in CRT of, respectively, 194.2 and 48.4 μm was recorded in the IVR groups and sham. Further data regarding the efficacy of IVR (at the same two dosing) versus placebo emerged from a larger study evaluating two parallel, phase III, multicenter clinical trials of equal methodology (RISE and RIDE study) [91]. At month 24, globally, a visual improvement of 15 or more letters was seen in the 33.6, 45.7, and 12.3 % of the IVR high dosing, low dosing, and placebo, respectively. Significantly, a CRT reduction, few laser procedures, and decrease in diabetic retinopathy progression have been reported in the IVR groups compared to sham. Ocular safety of IVR was consistent with previous data. Thus, the authors concluded that IVR is more effective than placebo and could enable the visual recovery, reducing the macular edema, with low rates of side effects.

Intravitreal ranibizumab has been compared to the gold standard, focal, or grid laser photocoagulation, in recent randomized clinical trials in order to evaluate which is the best treatment strategy [92, 93, 101, 102]. In a recent multicenter study (READ- 2), subjects were randomly assigned to receive IVR or laser or their association according to the following scheme: group 1 performing IVR at baseline and at months 1, 3, and 5; group 2 receiving focal or grid laser photocoagulation at baseline and if required at the third month; and group 3 having IVR, according to the scheme of group 1, combined at laser at baseline and at third month [92, 101, 102]. From the sixth month, all subjects requiring further treatment were assigned to the IVR treatment. After the primary (at sixth month) end point, several patients were treated with only IVR and the number of required injections was, respectively, 5.3, 4.4, and 2.9 for the three groups in the remaining follow-up of 18 months. At primary end point, the main gain in BCVA was, respectively, 7.4, 0.5, and 3.8 letters and turned into 7.7, 5.1, and 6.8 letters at the 24th month for the three groups. The percentage of patients who gained three or more lines in BCVA was, respectively, 21, 0, and 6 at sixth month, compared with 24, 18, and 26 at 24th month in the three arms. At final fol- low-up, mean CRT was 340, 286, and 258 μm, and the percentage of patients with a CRT of 250 μm or few was, respectively, 36, 47, and 68 % for all groups. Thus, IVR seemed to provide significant benefits in terms of BCVA recovery and CRT decline for almost 2 years. The combination therapy of IVR plus laser seemed to offer a greater reduction in macular edema and a fewer number of required injections. Thus, these results showed that IVR alone and IVR with additional laser seemed to be more effective than laser grid or focal photocoagulation alone. At the 3-year follow-up, the study reported a mean BCVA improvement of 7.2 letters in the IVR group and a CRT of 282 μm [92]. Changes in BCVA and CRT in the other groups were not statistically significant. A greater number of injections were performed in the IVR group compared with the other groups. The study showed that the treatment with IVR alone, even if more aggressive, provided better results resulted in terms of CRT reduction and BCVA improvement during 3 years of follow-up. Thus, the performance of a more extensive focal/grid laser treatment in the other two groups could probably reduce the number of IVR injections to control DME (Fig. 3.22). In conclusion, the authors suggested that IVR could provide excellent long-term visual outcomes in the clinical practice, even if frequent injections are required in most of the patients to optimally control DME and maximize vision results.

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e

f

Fig. 3.22 (a–d) At baseline diffuse diabetic macular edema, with few hard exudates (a), leaking microaneurysms (b), diffuse leakage (c), and increased retinal thickness, with a small subretinal detachment and multiple intraretinal cysts on OCT (d). (e) After three intravitreal injections of ranibizumab, OCT shows flattening of the retina. (f) Two months later, OCT demonstrates recurrence of macular edema. Re-treatment is required, and macular laser photocoagulation could be suggested

Based on these data, an additional larger trial (RESTORE study) with 12 months of duration was performed to assess if IVR alone or associated with macular laser photocoagulation was superior to laser treatment alone [93]. Patients were randomized into the following study arms: IVR plus sham laser, IVR plus laser, or sham IVR plus laser. Patients were followed each month and received IVR/sham on a monthly scheme and the pro re nata (PRN) administration or underwent laser/sham at baseline and then PRN. The results showed that IVR alone or combined with laser was superior to laser alone in terms of visual acuity recovery and macular edema resolution (Fig. 3.23). In fact, at the twelfth month, mean BCVA letter score was, respectively, +6.1, +5.9, and +0.8 compared to baseline in the three groups, and a BCVA increase of 15 or more letters was seen, respectively, in 22.6, 22.9, and 8.2 % of the patients randomized in the three arms. In addition, a greater reduction in CRT was reported in the IVR groups compared to laser alone (−118.7, −128.3,

Fig. 3.23 (a–c) Clinically significant diabetic macular edema, characterized by circinate ring of hard exudates (a), intense fluorescein leakage (b), and increased retinal thickness, with large cystoid spaces (c). (d–f) Six months later, after grid laser photocoagulation and three monthly injections of ranibizumab, a marked reabsorption of exudation is clearly seen (d), associated to reduction of fluorescein leakage (e) and flattening of the retina, with persistence of few small intraretinal cysts (f)

and −61.3 μm in the three arms, respectively). Therefore, the authors concluded that IVR as monotherapy or combined with laser provided a greater visual improving and macular edema decline in patients with DME compared to laser alone. Participants who completed the 1-year trial (core study) were eligible to participate to the 24-month open-label extension. In the expanded study, patients included in all the three groups underwent open-label injections and could receive laser therapy according to the investigator’s discretion. At the third month, the mean change in BCVA from core study baseline was, respectively, +8, +6.7, and +6 in the three groups, respectively [103].

The efficacy of IVR alone or adjunct to laser has been confirmed through another wider trial and its 3-year results [76, 94]. The DRCR.net reported the expanded

results of a previously reported study assessing the efficacy of IVR or IVTA combined with laser [38, 39]. In the previous study, patients were randomized into three different treatments: IVR with prompt or deferred (≥24 weeks) laser and 4 mg IVTA with prompt laser, compared with sham injections with laser alone for treatment of center-involved DME. The study found that IVR with prompt or deferred laser was superior to laser alone at the first year [76]. In the extension, eyes originally assigned to IVR plus prompt laser or IVR plus deferred laser maintained their original randomization protocol, while eyes originally assigned to sham plus laser or IVTA plus prompt laser could elect to switch to IVR. The 3-year follow-up evaluated which was the best association treatment strategy: IVR plus prompt or deferred laser [94] (Fig. 3.24). The study suggested that grid/focal laser photocoagulation performed at the beginning of IVR should be considered not better but possibly worse than laser treatment deferral of 24 or more weeks. In particular, the mean change in BCVA letter score from baseline was 2.9 letters more in the deferral group compared with the prompt laser group. A fewer number of IVR injections were performed in the prompt group. Nevertheless, the 5-year follow-up is ongoing.

Bevacizumab (Avastin®, Genentech In. San Francisco, CA, USA) is a full-length recombinant humanized antibody that competitively inhibits all isoforms of VEGF and is approved by the FDA for the treatment of metastatic colon cancer, metastatic breast cancer, and non-small cell lung cancer. Intravitreal bevacizumab (IVB) has been used off-label with some benefits in the treatment of many retinal disorders, including DME and PDR, neovascular age-related macular degeneration, and central or branch retinal vein occlusion. Several studies have been published evaluating IVB (at different doses) in DME, retrospective or prospective, all showing improvement in BCVA and OCT outcomes, but also short-term efficacy and a high rate of recurrences [95, 96, 104–107] (Fig. 3.25).

Earlier results regarding the efficacy of IVB in the short term compared to laser were reported in a randomized, phase II clinical trial published in 2007 [95]. Subjects were randomly assigned to one of the following five arms: group 1 consisted in focal photocoagulation at baseline; group 2 assigned to IVB 1.25 mg at baseline and at 6-week follow-up; group 3, randomized to IVB 2.5 mg at baseline and at 6 weeks; group 4, IVB 1.25 mg at baseline and sham injection at the sixth week; and group 5, 1.25 mg IVB at baseline and 6 weeks with additional photocoagulation at 3 weeks. The study provided some interesting conclusions. Compared to laser photocoagulation, IVB 1.25 and 2.5 mg provided a greater reduction in CRT at 3 weeks, while at longer follow-up no meaningful differences in CRT between laser and IVB groups were reported. In the short-term, there was not likely a large difference between the two IVB doses. In addition, the study suggested that the reduction in CRT appeared to plateau at 3 weeks from the IVB and in most eyes a progressive decline in CRT was seen between the 3- and 6-week visits. Thus, the authors concluded that 6 weeks might be a too long interval for an optimal second IVB. Moreover, the study revealed that combining photocoagulation with IVB provided no apparent benefit in the short term.

a

b

c

d

Fig. 3.24 (a) A 70-year-old male, with diagnosis of DM type 2 since 20 years and poor metabolic control, associated to hypertension and renal failure, who complains a visual acuity drop (BCVA 20/125). Visual examination discloses the presence of cataract, diabetic macular edema with severe retinal thickness, associated to serous retinal detachment and multiple intraretinal cystoid spaces. (b) Two months after first intravitreal injection of ranibizumab and prompt grid laser treatment, visual acuity improved (BCVA 20/100) and retinal thickness reduced. (c) After six months, the patient complaints again a visual acuity decline (BCVA 20/200), and increasing of retinal thickness was detected. (d) Six months later, after three further intravitreal injections of ranibizumab, visual acuity improved again (BCVA 20/100), and the retina was completely flat

d

h

i

Fig. 3.25 (a–d) Clinically significant diabetic macular edema, characterized by circinate lipids (a), multiple leaking microaneurysms (b), diffuse fluorescein leakage (c), increased retinal thickness, with a large central cyst (d). (e–h) Six months later after grid laser photocoagulation and five intravitreal injections of bevacizumab, a complete regression of hard exudates (e), a marked improvement in fluorescein leakage (f, g), and a reduction in retinal thickness are noticeable, even with persistence of central intraretinal cysts (h). (i) Two months later, a recurrence of diabetic macular edema is visible on OCT, and the patients started again with the intravitreal injections of bevacizumab

Other reports suggested that the two dosing regimens offered similar advantages in the treatment of DME, evaluating the BCVA improvement and the CRT reduction [104, 105].

Interesting results emerged from a larger study with longer follow-up evaluating two different treatment options: IVB 1.25 mg and macular laser photocoagulation in eyes with persistent DME [96, 107]. The 2-year results showed that the IVB arm

a

b

Fig. 3.26 (a) DME refractory to previous grid laser photocoagulation. (b) One year after multiple injections of bevacizumab, a clear reduction of the retinal thickness is seen, with persistence of small intraretinal cysts. Interestingly, a change in the vitreoretinal interface is evolving

gained a mean of 8.6 letters compared to a mean loss of 0.5 letters in the laser group. A BCVA improvement of 10 or more letters was reported in 49 and 7 % of the two groups, respectively. A mean reduction in CRT of 146 and 118 μm was registered in the two arms, respectively. A median number of 13 and 4 treatments were recorded in the two groups, respectively, over a 24-month follow-up. Thus, the study showed that IVB 1.25 mg provided meaningful benefits in BCVA and CRT at 1 year and that such results were maintained over the second year with a mean number of four injections (Fig. 3.26).

A number of studies compared the effectiveness of IVB versus IVTA [97, 108, 109]. Thus, these and more other works have the limitation of a small study population and a limited follow-up, which lacked sufficient power to compare safety and effectiveness of the two treatments. In a randomized three-arm clinical trial evaluating IVB alone or in association with IVTA compared to macular laser photocoagulation, IVB yielded a better visual outcome compared with laser at a 24-week follow-up [97].

Pegaptanib sodium (Macugen®, Eyetech Inc, Cedar Knolls, NJ, USA) is a selective anti-VEGF165 blocker, which is considered the major ocular pathological isoform of VEGF. Intravitreal pegaptanib (IVP) is currently approved for the treatment of wet age-related macular degeneration and has been assessed in several works as a treatment option in DME, showing positive results [98, 99, 110, 111]. The preliminary results emerged from a randomized, double-masked, multicenter clinical trial (Macugen Diabetic Retinopathy Study Group), evaluating the effects of IVP, different dosing (0.3, 1, and 3 mg), performed every 6 weeks (for a total of nine administration) compared to sham in center-involved DME over a period of 48 weeks [98]. A meaningful BCVA gain of ten or more letters was noticed in 34 % of the group receiving IVP 0.3 mg compared to placebo (10 %), and a mean CRT

reduction of, respectively, 68 and 4 μm was observed in the two groups. Laser photocoagulation was performed in fewer subjects in each IVP arm.

The efficacy of IVP 0.3 mg has been confirmed later in a large, randomized, clinical trial (Macugen 1013 study) [99, 111]. Subjects randomly received IVP or placebo every 6 weeks and additional focal/grid photocoagulation if necessary from the 18th week in the first year. In the second year, patients received IVP on a PRN regimen. A total of 36.8 and 19.7 % of subjects from the two groups, respectively, experienced a BCVA gain of ten or more letters at week 54. Mean change in BCVA in the IVP group was superior to placebo at all time points, showing at week 102 a BCVA increase of 6.1 and 1.3 letters in the IVP and sham groups, respectively. A fewer number of laser procedure were deemed necessary in the IVP arm. Thus, this study confirmed that IVP is considered as an effective treatment modality in DME, with a safety profile.

Aflibercept (VEGF Trap-Eye, Eylea, Regeneron Inc., New York) is a fusion protein, which binds both the two pro-angiogenic factors VEGF-A and placental growth factor (PGF), showing a greater affinity than their natural receptors. Currently, intravitreal aflibercept (IVA) is an approved treatment for the neovascular form of age-related macular degeneration. Preliminary results on DME have been recently published showing a longer duration of action, probably related to its increased intravitreal half-life [100, 112]. In a recent randomized, phase 2 clinical trial (DA VINCI study), the efficacy of IVA has been assessed on different dosing regimens in a 1-year outcome. Participants were randomly assigned to one of the five treatment options: IVA 0.5 mg every 4 weeks, IVA 2 mg every 4 weeks, IVA 2 mg every 8 weeks after 3 initial monthly doses, IVA 2 mg PRN after 3 initial monthly doses, or macular laser. The results in terms of mean BCVA improvements at week 52 were, respectively, 11.0, 13.1, 9.7, and 12.0 letters for the all IVA groups, compared to a visual decline of 1.3 letters for the laser group. A visual gain of 15 or more letters were, respectively, 40.9, 45.5, 23.8, and 42.2 % in the IVA arms compared to 11.4 % for laser. In addition, a mean improvement in CRT of, respectively, 165.4, 227.4, 187.8, and 180.3 μm for the IVA regimens compared to 58.4 μm for laser was seen at 52 weeks. Thus, the authors concluded that IVA was effective and well tolerated in the treatment of DME. Interestingly, the study showed that IVA 2 mg, after 3 monthly doses and then administered every 8 weeks, is not better than IVA, same dose, 3 monthly injections initially and then PRN.

Summary 3.6

The most studied anti-VEGF agents in DME are ranibizumab, bevacizumab, and pegaptanib sodium. Their safety and efficacy have been compared to placebo and to laser photocoagulation showing favorable results. Recent promising outcomes emerged also from the administration of aflibercept.