Research Promises Better Diabetic Retinopathy Management

STOCKHOLM — At the American Society of Retina Specialists (ASRS) 2024 Annual Meeting, researchers discussed how insights into potential risk factors and new treatments could improve outcomes for patients with diabetic retinopathy.

Jennifer Lim, MD, an ophthalmologist and director of the Retina Service at the University of Illinois Hospital & Health Sciences System in Chicago, told Medscape Medical News that emerging approaches to treating diabetic retinopathy offer hope because they address the root causes of the disease beyond just targeting vascular endothelial growth factor (VEGF). She said innovative methods and add-on treatments could lead to more durable and effective drugs.

Exploration of risk factors and treatment options for diabetic retinopathy could lead to more effective management strategies for the condition, agreed David Boyer, MD, an ophthalmologist at Retina Vitreous Associates Medical Group in Los Angeles, speaking with Medscape Medical News.

Risk Factors for Diabetic Retinopathy

Sodium-glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 receptor agonists (GLP-1 RAs) have gained popularity because of their benefits beyond glycemic control, including weight loss, and cardiovascular and kidney protection. However, the impact of these medications on vision-threatening retinal complications is not fully understood. “There has always been a question about whether these newer diabetes medications might exacerbate diabetic eye disease,” said Boyer.

In a retrospective observational study, researchers included adults with type 2 diabetes and moderate cardiovascular disease risk who had no history of advanced diabetic retinal complications. These patients initiated treatment with GLP-1 RA, SGLT2 inhibitors, DPP-4 inhibitors, or sulfonylureas. The study used inverse probability of treatment weighting to mimic randomization and compared the time to the first treatment for diabetic macular edema or proliferative diabetic retinopathy across the treatment groups.

Results, presented by Andrew J. Barkmeier, MD, an associate professor of ophthalmology at the Mayo Clinic, showed that among 371,698 patients, those who initiated therapy with SGLT2 inhibitors had a lower risk of requiring treatment for sight-threatening retinopathy compared with those using other medication classes. GLP-1 RA did not increase retinopathy risk relative to dipeptidyl peptidase 4 inhibitors and sulfonylurea medications.

“[This study] told us that we do have to keep an eye on patients’ retinopathy when they start on these new inhibitors. But the progression is minimal and, overall, I think most people today favor keeping blood sugar levels as good as possible,” said Boyer, who was not involved in the study.

Another factor that might increase diabetic retinopathy progression is obstructive sleep apnea. This underdiagnosed condition is linked to several health issues, including dementia, stroke, and myocardial infarctions. Although not easily treated, obstructive sleep apnea is manageable, Boyer explained.

Researchers utilized the TriNetX electronic health records research network to identify patients with nonproliferative diabetic retinopathy, both with and without obstructive sleep apnea.

The results, presented by Ehsan Rahimy, MD, a retinal specialist at Palo Alto Medical Foundation and a professor at Stanford University, showed that patients with obstructive sleep apnea had a significantly higher risk of progressing to proliferative diabetic retinopathy and developing new-onset diabetic macular edema. These patients were more likely to require ocular interventions, such as intravitreal injections and laser photocoagulation. They also had greater risks for stroke, myocardial infarction, and death compared with those who did not have obstructive sleep apnea.

“It was good to bring this to everybody’s attention,” said Boyer, who was not involved in the study. “It’s an easy question to ask someone if they snore.”

New Treatments on the Horizon

In another presentation, Nathan C. Steinle, MD, of California Retina Consultants, presented a study that assessed the durability of response to sozinibercept in patients with retinal vascular diseases. This novel therapeutic agent is designed to inhibit VEGF-C and VEGF-D in conditions where VEGF-A suppression alone is insufficient.

Sozinibercept was combined with standard anti–VEGF-A therapies such as ranibizumab or aflibercept. It involved a prospective, post hoc analysis of two phase 1b, open-label, dose-escalation studies, including 40 patients with neovascular age-related macular degeneration (nAMD) (31 patients) or diabetic macular edema (nine patients). These patients, either treatment-naive or previously treated, received three intravitreal injections of ranibizumab or aflibercept in combination with sozinibercept at various doses.

Results indicated that sozinibercept combination therapy was well tolerated, with no dose-limiting toxicities. In treatment-naive nAMD patients, the mean best-corrected visual acuity (BCVA) improved significantly from baseline at months 3 and 6. Previously treated nAMD patients also showed BCVA improvements, although to a lesser extent. For patients with persistent diabetic macular edema, switching to sozinibercept plus aflibercept resulted in notable BCVA gains. The mean time to requiring retreatment was longer in treatment-naive patients than in those previously treated, indicating a durable response.

“Combination therapy with sozinibercept is going to be really important,” said Lim, who was not involved in the study, “because it attacks with a dual mechanism of action.”

Oral agents promise a potentially easier alternative for patients compared with frequent injections. CU06-1004 is a novel orally administered endothelial dysfunction blocker that has shown promise in stabilizing damaged capillaries, reducing abnormal angiogenesis, and inhibiting inflammatory activation in preclinical studies. “CU06 is very interesting to me because by preventing endothelial loss, it gets to the pathophysiology of why the blood vessels break down,” Lim said.

In a proof-of-concept phase 2a, multicenter, open-label, parallel-group trial, investigators randomly assigned 67 patients with diabetic macular edema to receive 100 mg, 200 mg, or 300 mg of CU06-1004 once daily for 12 weeks, followed by a 4-week follow-up.

Results presented by Victor Gonzalez, MD, of Valley Retina Institute in Texas, indicated that the oral agent improved BCVA, stabilized central subfield thickness, and showed positive anatomical changes in optical coherence tomography images. CU06-1004 was well tolerated, with no drug-related serious adverse events.

“The number [of patients] was very small, and we will need a much longer, larger trial to see if [CU06-1004] has benefits long term,” said Boyer, who was not involved in the study. “But I think we’re all very excited if we can find an oral agent for treating diabetic retinopathy. It would be easier for the patient to take a pill than having to come in for injections.”

The sustained-release axitinib implant, OTX-TKI, is also generating significant interest, particularly for non-proliferative diabetic retinopathy. Axitinib, a tyrosine kinase inhibitor (TKI), targets signaling pathways crucial in cellular processes, providing a novel approach to managing diseases where traditional therapies might fall short. Unlike traditional anti-VEGF treatments that focus solely on cytokine levels, TKIs block the activation of signaling pathways, preventing downstream signaling regardless of cytokine levels. This mechanism is particularly important because it effectively inhibits disease progression even if levels of VEGF are high, Lim explained.

In the phase 1 HELIOS trial, OTX-TKI was assessed in patients with nonproliferative diabetic retinopathy. This multicenter, double-masked, parallel-group clinical study included 21 patients who had not received anti-VEGF treatment, dexamethasone intravitreal implants in the previous 12 months, or intraocular steroid injections in the prior 4 months. Patients were randomly assigned to receive either OTX-TKI or sham treatment.

Results presented by Dilsher S. Dhoot, MD, of California Retina Consultants, indicated that OTX-TKI was generally well tolerated, with no serious ocular adverse events. At 48 weeks, 46.2% of eyes treated with OTX-TKI showed a 1- or 2-step improvement on the Diabetic Retinopathy Severity Scale (DRSS) compared with none in the sham arm. Additionally, no eyes treated with OTX-TKI experienced a worsening on the DRSS, whereas 25% of eyes in the sham arm did. Vision-threatening complications, such as proliferative diabetic retinopathy or diabetic macular edema, developed in 37.5% of the sham group but in none of the OTX-TKI treated eyes. A single injection of OTX-TKI provided durable DRSS improvement for up to 48 weeks, with no patients in either arm requiring rescue therapy.

“This is a really exciting add-on treatment,” Lim said, who was not involved in the study. She explained that it is initially necessary to control the disease with standard treatments, because TKIs may take longer to exhibit their effects. Once the disease is stabilized, TKIs can be used alongside other therapies, potentially reducing the reliance on frequent anti-VEGF injections. “These are preliminary results, but that’s the hope going forward.”

Lim and Boyer report no relevant financial relationships.

Manuela Callari is a freelance science journalist who specializes in human and planetary health. Her words have been published in The Medical Republic, Rare Disease Advisor, The Guardian, MIT Technology Review, and others.