Ozempic link to rare vision loss risk confirmed in study

Novo Nordisk’s blockbuster shot Ozempic was linked to an increased risk of a rare form of vision loss in a study that backs up Harvard University research published earlier this year.

Diabetes patients who used Ozempic were more than twice as likely to be diagnosed with the rare condition, called NAION, than those who took another type of diabetes drug, according to a team of researchers who studied years of patient records from Denmark and Norway.

The study wasn’t able to determine whether there was a similar impact among people taking Ozempic’s sister drug, Wegovy, for obesity.

The results appeared December 11 on medRxiv, a website that posts studies before they’ve been reviewed by outside scientists.

NAION occurs when a loss of blood flow damages the optic nerve and is most common in people older than 50. Diabetes itself, heart disease, sleep apnoea and other conditions can also raise the risk that it will strike. The overall rate of the condition was very low in the study, with just 1.4 additional cases per 10,000 years of patient observation among patients who took Ozempic compared with those who took the other diabetes drug.

Still, the eye condition is irreversible, untreatable and potentially blinding, and doctors have said that patients should be informed of the possible risk. The corresponding author on the study declined to comment.

Novo shares fell as much as 5.4 per cent in Copenhagen, the most in about a month. The stock has climbed about 8 per cent this year, outpacing a rise of around 4 per cent in a Bloomberg index tracking European pharmaceutical companies.

Assuming the risk remains constant over time, the results indicate that a type 2 diabetes patient taking Ozempic for 20 years would have a 0.3 per cent to 0.5 per cent chance of developing NAION, the research team said.

“It is crucial to weigh the potential risk of NAION against the substantial therapeutic benefits of semaglutide,” the active ingredient in Ozempic and Wegovy, according to authors from the University of Southern Denmark, Norwegian Institute of Public Health and University of Copenhagen, as well as other institutions that conducted the research.

After a thorough evaluation of this study and its own internal safety assessment, Novo said it believes the risk-benefit profile is unchanged. Very few cases of NAION were seen in Novo’s own trials, the company said, “with no imbalance disfavouring” its drugs.

Hints of a link to NAION first emerged in a smaller study published in July by a team from the Harvard-affiliated hospital Massachusetts Eye and Ear. It’s an example of how very rare potential side effects may emerge only after extremely large numbers of people use a medicine.

The Nordic study found a smaller added risk of NAION than the Harvard trial did. That trial focused on patients who had at some point been referred to a doctor for a neuro-ophthalmological assessment, the Danish-Norwegian team noted, and may have been sicker as a result.

The Nordic study compared users of semaglutide and people who took medicines in an older class of drugs, called SGLT-2s. It followed new users of the drugs in Denmark and Norway from the beginning of 2018 - the year Ozempic was launched in those markets - until June 2024 in Denmark and May 2022 in Norway. The researchers included more than 44,000 Ozempic patients in Denmark and more than 16,000 in Norway, finding 32 cases of NAION in the entire group.

The findings with Wegovy, which became available in Denmark in 2022 and in Norway in early 2023, were inconclusive because not enough patients were included.