Expert throws light on retinopathy complication seen in SUSTAIN-6
The higher rate of diabetic retinopathy seen in patients taking the glucagon-like peptide 1 (GLP-1) receptor agonist semaglutide vs placebo is likely a result of the rapid lowering of HbA1c, a new analysis of data from the SUSTAIN-6*
“Patients who had retinopathy complications had a rapid and steep decrease of approximately 2.5 percent in HbA1c level,” said investigator Dr Tina Vilsbøll, clinical manager at the Steno Diabetes Center in Copenhagen, Denmark. “Rapid improvement in glycaemic control is a risk factor for retinopathy complications.”
Semaglutide cut the primary composite outcome of cardiovascular (CV) death, nonfatal MI, or nonfatal stroke in SUSTAIN-6, an outcome that established its noninferiority to placebo, with a safety profile that was comparable to other GLP-1 agonists for type 2 diabetes (T2D). Rates of new or worsening nephropathy were lower with semaglutide vs placebo. However, rates of retinopathy complications (vitreous haemorrhage, blindness, or conditions requiring treatment with an intravitreal agent or photocoagulation) were significantly increased with semaglutide (hazard ratio, [HR], 1.76; p=0.02). [N Engl J Med 2016;375:1834-1844]
Further analysis of the data showed that the 79 patients who had retinopathy had a longer duration of diabetes (17.7 years vs 13.9 for the overall study population) and higher mean HbA1c (9.4 percent vs 8.7 percent for the entire cohort). [ADA 2017, presentation 1-AC-SY09]
Almost 65 percent of patients who experienced retinopathy were taking insulin compared with 58 percent of the total study population. In addition, 83.5 percent of those in the retinopathy group had a history of diabetic retinopathy at baseline, 29 percent had a history of proliferative retinopathy, and 17.7 percent had a laser or injection therapy for proliferative retinopathy.
“When we split the patients into those without retinopathy at baseline and patients with retinopathy, patients who did not have any history of retinopathy [had] no signals with semaglutide — it was exactly the same as placebo,” said Vilsbøll.
Regulatory guidance mandates the need to establish CV safety of novel diabetes therapies. SUSTAIN-6 was the second CV outcomes trial to demonstrate positive results for a GLP-1 agonist in T2D patients at high risk of cardiovascular disease (CVD). The trial was a randomized, double-blind, placebo-controlled, parallel group trial of 3,297 patients from 230 sites in 20 countries. Researchers compared semaglutide 0.5 mg or 1.0 mg once weekly vs placebo, on top of their standard care regimen.
Vilsbøll said the data at hand suggest that compared with the full study population, patients with retinopathy complications had worse control of their HbA1c and are more likely to have pre-existing retinopathy at baseline. Considering that patients with the greater treatment effect in terms of HbA1c were the ones most at risk, clinically this means clinicians should exercise caution when using potent glucose-lowering agents in this population.
“When initiating a highly effective treatment [such] as semaglutide, similar guidance should be given in these vulnerable patients,” Vilsbøll concluded.