GLP-1 drugs are under fresh scrutiny over rare condition; here's what's happening
Studies, regulators and US litigation are looking at a possible link between GLP-1 drugs and a rare eye condition that can cause vision loss.
- Sep 25, 2026,
- Updated Sep 25, 2026 4:09 PM IST
Danish drugmaker Novo, formerly Novo Nordisk, on Friday cited data from its own clinical trials that recorded cases of a rare eye condition causing vision loss among people taking its GLP-1 medicines.
The statement comes as studies based on real-world patient records have reported an association between semaglutide and the eye condition, European regulators have classified NAION as a very rare side effect of semaglutide, and US litigation involving Novo and US drugmaker Eli Lilly is under way.
The condition, called non-arteritic anterior ischaemic optic neuropathy, or NAION, occurs when blood flow to the optic nerve at the back of the eye is disrupted. It can cause sudden, painless loss of vision, usually in one eye. “Semaglutide has been studied in multiple clinical development programmes with a total exposure from post-marketing use of over 58 million patient-years,” Novo told Business Today.
Novo said a published pooled analysis of its randomised clinical trials of liraglutide and semaglutide, comprising more than 83,000 patient-years of observation in the semaglutide arm, identified very few ophthalmologist-confirmed cases of NAION and did not show an increased incidence among participants receiving semaglutide.
The company said the analysis covered 96,829 people and recorded three confirmed cases of NAION among participants receiving the GLP-1 medicines, compared with five among participants given an inactive treatment.
Evidence from routine clinical practice has been less consistent. A 2026 meta-analysis of observational studies found an association between semaglutide use and a higher risk of NAION, while another review of six observational studies did not find a statistically significant overall increase and rated the certainty of the evidence as low to very low. A separate analysis also found a higher rate of NAION among semaglutide users in observational studies of people with diabetes, but not a statistically significant increase in randomised clinical trials.
The European Medicines Agency has taken a regulatory position on semaglutide specifically. In June 2025, its safety committee concluded that NAION is a very rare side effect of semaglutide, meaning it may affect up to one in 10,000 people taking the medicine. The EMA said several large epidemiological studies suggested that adults with type II diabetes taking semaglutide had about twice the risk of developing NAION compared with people not taking the medicine.
The EMA also recommended updating the product information for semaglutide medicines. Patients experiencing sudden loss of vision or rapidly worsening eyesight are advised to contact their doctor without delay, and treatment should be stopped if NAION is confirmed.
The issue has also moved into US courts. Federal cases have been consolidated into a multidistrict litigation in Pennsylvania involving products from Novo and Lilly, including Novo’s Ozempic and Wegovy and Lilly’s Trulicity.
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The US Judicial Panel on Multidistrict Litigation said plaintiffs allege that use of Eli Lilly’s or Novo Nordisk’s GLP-1 medicines caused NAION and that the cases involve common issues around the development, testing, regulatory history, promotion and labelling of the products.
As of September 1, 2026, 216 actions were pending in the multidistrict litigation, according to the US Judicial Panel on Multidistrict Litigation. The consolidation is a procedural step and does not establish that the medicines caused the eye condition.
The litigation comes as Novo and Lilly have become major players in the fast-growing market for medicines used to manage diabetes and obesity. Their blockbuster metabolic drugs are significant contributors to company revenues, with Novo’s semaglutide brands and Lilly’s tirzepatide brands among the leading products in the category.
Semaglutide is a GLP-1 receptor agonist used to manage type 2 diabetes and, at different doses and under different brand names, for weight management. Tirzepatide, used by Lilly in Mounjaro and Zepbound, acts on both GIP and GLP-1 receptors.
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The development is also relevant in India, where the market has expanded rapidly following the launch of tirzepatide and generic versions of semaglutide.
India’s GLP-1 market reached ₹2,333 crore on a moving annual total basis in August 2026, according to Pharmarack’s PharmaTrac data. Semaglutide accounted for ₹782 crore and tirzepatide ₹1,456 crore.
Novo’s semaglutide patent expiry in India has also brought several domestic pharmaceutical companies into the market with generic versions of the drug, expanding the number of companies exposed to developments around its safety profile.
“Considering the totality of evidence from clinical trials, post-marketing reports and observational studies, alongside the generally low incidence rate of NAION, Novo Nordisk believes that the benefit-risk profile of semaglutide remains favourable,” the company said.
Business Today reached out to Eli Lilly for a comment on the allegations and the litigation. The company had not responded until the publication of this story. This story will be updated if a response is received.
Danish drugmaker Novo, formerly Novo Nordisk, on Friday cited data from its own clinical trials that recorded cases of a rare eye condition causing vision loss among people taking its GLP-1 medicines.
The statement comes as studies based on real-world patient records have reported an association between semaglutide and the eye condition, European regulators have classified NAION as a very rare side effect of semaglutide, and US litigation involving Novo and US drugmaker Eli Lilly is under way.
The condition, called non-arteritic anterior ischaemic optic neuropathy, or NAION, occurs when blood flow to the optic nerve at the back of the eye is disrupted. It can cause sudden, painless loss of vision, usually in one eye. “Semaglutide has been studied in multiple clinical development programmes with a total exposure from post-marketing use of over 58 million patient-years,” Novo told Business Today.
Novo said a published pooled analysis of its randomised clinical trials of liraglutide and semaglutide, comprising more than 83,000 patient-years of observation in the semaglutide arm, identified very few ophthalmologist-confirmed cases of NAION and did not show an increased incidence among participants receiving semaglutide.
The company said the analysis covered 96,829 people and recorded three confirmed cases of NAION among participants receiving the GLP-1 medicines, compared with five among participants given an inactive treatment.
Evidence from routine clinical practice has been less consistent. A 2026 meta-analysis of observational studies found an association between semaglutide use and a higher risk of NAION, while another review of six observational studies did not find a statistically significant overall increase and rated the certainty of the evidence as low to very low. A separate analysis also found a higher rate of NAION among semaglutide users in observational studies of people with diabetes, but not a statistically significant increase in randomised clinical trials.
The European Medicines Agency has taken a regulatory position on semaglutide specifically. In June 2025, its safety committee concluded that NAION is a very rare side effect of semaglutide, meaning it may affect up to one in 10,000 people taking the medicine. The EMA said several large epidemiological studies suggested that adults with type II diabetes taking semaglutide had about twice the risk of developing NAION compared with people not taking the medicine.
The EMA also recommended updating the product information for semaglutide medicines. Patients experiencing sudden loss of vision or rapidly worsening eyesight are advised to contact their doctor without delay, and treatment should be stopped if NAION is confirmed.
The issue has also moved into US courts. Federal cases have been consolidated into a multidistrict litigation in Pennsylvania involving products from Novo and Lilly, including Novo’s Ozempic and Wegovy and Lilly’s Trulicity.
MUST READ | Weight loss drugs come with a new lifestyle. And Tata is already preparing for it
The US Judicial Panel on Multidistrict Litigation said plaintiffs allege that use of Eli Lilly’s or Novo Nordisk’s GLP-1 medicines caused NAION and that the cases involve common issues around the development, testing, regulatory history, promotion and labelling of the products.
As of September 1, 2026, 216 actions were pending in the multidistrict litigation, according to the US Judicial Panel on Multidistrict Litigation. The consolidation is a procedural step and does not establish that the medicines caused the eye condition.
The litigation comes as Novo and Lilly have become major players in the fast-growing market for medicines used to manage diabetes and obesity. Their blockbuster metabolic drugs are significant contributors to company revenues, with Novo’s semaglutide brands and Lilly’s tirzepatide brands among the leading products in the category.
Semaglutide is a GLP-1 receptor agonist used to manage type 2 diabetes and, at different doses and under different brand names, for weight management. Tirzepatide, used by Lilly in Mounjaro and Zepbound, acts on both GIP and GLP-1 receptors.
DON'T MISS | Lilly's obesity drug retatrutide helps patients lose up to 30% weight in Phase 3 trial
The development is also relevant in India, where the market has expanded rapidly following the launch of tirzepatide and generic versions of semaglutide.
India’s GLP-1 market reached ₹2,333 crore on a moving annual total basis in August 2026, according to Pharmarack’s PharmaTrac data. Semaglutide accounted for ₹782 crore and tirzepatide ₹1,456 crore.
Novo’s semaglutide patent expiry in India has also brought several domestic pharmaceutical companies into the market with generic versions of the drug, expanding the number of companies exposed to developments around its safety profile.
“Considering the totality of evidence from clinical trials, post-marketing reports and observational studies, alongside the generally low incidence rate of NAION, Novo Nordisk believes that the benefit-risk profile of semaglutide remains favourable,” the company said.
Business Today reached out to Eli Lilly for a comment on the allegations and the litigation. The company had not responded until the publication of this story. This story will be updated if a response is received.