Aflibercept May Target Galectin-1, a Novel Angiogenic Factor Associated with Proliferative Diabetic Retinopathy

Angiogenesis, the formation of new blood vessels from a vascular bed, usually occurs during wound healing and organ regeneration. Many studies have shown that vascular endothelial growth factor A (VEGF-A) plays a central role in the endothelial cell proliferation that leads to angiogenesis. Abnormal angiogenesis driven by VEGF-A causes vision-threatening eye diseases such as proliferative diabetic retinopathy (PDR).

Aflibercept (Eylea, Bayer HealthCare/ Regeneron), the most recently developed VEGF antibody, has a higher affinity for binding VEGF-A than the other available anti-VEGF antibodies. It can also target members of the VEGF family other than VEGF-A, for example, VEGF-B.

Now, new findings indicate that, independent of its effect on VEGF-A, Eylea exerts anti-angiogenic effects against galectin-1, a galactoside-binding lectin protein and novel angiogenic factor associated with PDR. These findings were reported by Atsuhiro Kanda, principle investigator of a team from Hokkaido University, Sapporo, Japan, at the Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting in Seattle, WA, on May 2, 2016. The team’s results were also published in an abstract included in the ARVO proceedings.

First, the Japanese team used immunoprecipitation and mass spectrometry analyses to identify proteins that interact with Eylea. Second, using biolayer interferometry, they quantified Eylea’s affinities for binding with those proteins.

Next, the Japanese team did polymerase chain reaction studies to measure Galectin-1 gene mRNA expression levels. They found that expression of this gene was enhanced in hypoxic cell cultures and mouse models of retinal disease.

They also examined tissue samples from human eyes with PDR by using immunofluorescence and enzyme-linked immunosorbent assay. These tests indicated that galectin-1 reacts immunologically in the same areas as VEGFR2, the immunoglobulin fragment that Eylea was engineered to fuse with.

In addition, the team found that intravitreal galectin-1 protein levels were higher in eyes with PDR that in non-diabetic control eyes, and these levels did not correlate with increased VEGF-A levels. Moreover, injections of bevacizumab (Avastin), another VEGF-A antibody, were found to reduce VEGF-A but not galectin-1 levels.

In addition, applying galectin-1 and VEGF-A to human retinal microvascular endothelial cells up-regulated VEGFR2 phosphorylation. However, Eylea eliminated upregulation of VEGFR2 by both galectin-1 and VEGF-A.

Taken together, these results provide the first evidence that Eylea binds to and blocks a pro-angiogenic molecule outside the VEGF family.

The activity of Eylea against other angiogenic molecules besides VEGF may help to explain why Eylea produced greater gains in vision than Avastin after 2 years in anti-VEGF-naïve patients with diabetic macular edema who began anti-VEGF treatment with 20/50 or worse vision. Nevertheless, Eylea did not produce superior results in those who began anti-VEGF treatment with better vision. These results emerged from a randomized trial comparing Avastin, Eylea, and Lucentis (Protocol T) in 660 patients that was done by the Diabetic Retinopathy Clinical Research Network (DRCR.net).

At Monday’s ARVO meeting, DRCR.net investigator Jack Wells, MD, pointed out that Eylea-treated eyes were the least likely to require laser treatment for persistent macular edema. Only 40% of Eylea-treated eyes needed laser treatment, compared to about 66% of Avastin-treated eyes and 50% of Lucentis-treated eyes. However, in general, gains in vision were about the same for Eylea and Lucentis after 2 years.