Shares of Novo Nordisk and Eli Lilly extended declines after Mass Eye and Ear, a Harvard-affiliated hospital, revealed in a new study published in the journal JAMA Ophthalmology that people prescribed semaglutide, sold as Ozempic and Wegovy (Novo), have an elevated risk of developing a "potentially blinding eye condition" called nonarteritic anterior ischemic optic neuropathy (NAION). 

"The study found people with diabetes who had been prescribed semaglutide by their physician and then filled the prescription were more than four times more likely to be diagnosed with NAION," Mass Eye and Ear wrote in a press release, adding, "Those who were overweight or had obesity and prescribed this drug were more than seven times more likely to get the diagnosis." 

The study, which was led by Joseph Rizzo, MD, director of the Neuro-Ophthalmology Service at Mass Eye and Ear, wrote that the "use of these drugs has exploded throughout industrialized countries and they have provided very significant benefits in many ways, but future discussions between a patient and their physician should include NAION as a potential risk." 

Rizzo said, "It is important to appreciate, however, that the increased risk relates to a disorder that is relatively uncommon."

Rizzo disclosed that his research team analyzed thousands of medical records from Mass Eye and Ear to discover the connection between semaglutide and NAION:

The researchers analyzed the records of more than 17,000 Mass Eye and Ear patients treated over the six years since Ozempic was released and divided the patients in those who were diagnosed with either diabetes or overweight/ obesity. The researchers compared patients who had received prescriptions for semaglutide compared to those taking other diabetes or weight loss drugs. Then, they analyzed the rate of NAION diagnoses in the groups, which revealed the significant risk increases.

Rizzo noted several limitations to the study:

"Mass Eye and Ear sees an unusually high number of people with rare eye diseases, the study population is majority white, and the number of NAION cases seen over the six-year study period is relatively small. With small case numbers, statistics can change quickly." 

Mahyar Etminan, a drug safety researcher at the University of British Columbia in Vancouver, who wasn't involved in the study, told Bloomberg, "This is a very serious condition, so if it were true, it changes the risk-benefit calculus."

In the markets, shares of Novo Nordisk in Copenhagen extended their decline, dropping 2.6%, while Eli Lilly in New York fell by around 2%.

Earlier, both pharma companies fell after President Biden and Vermont Senator Bernie Sanders co-authored an opinion piece in USA Today, urging big pharma to slash the prices of anti-obesity drugs