The fall comes after US President Donald Trump yesterday sent letters to 17 major pharmaceutical firms, including Novo Nordisk, telling them to cut drug prices in the US.

That prompted share price declines across the sector.

Novo Nordisk on Tuesday slashed its forecast for 2025 sales growth due to competition from compounded, or copycat, versions of Wegovy and appointed veteran insider Maziar Mike Doustdar as its new CEO, prompting its shares to fall 23% on the day.

Novo became Europe’s most valuable listed company following the launch of Wegovy in June 2021.

However, its shares have plunged by more than two-thirds since peaking last year on concerns the drugmaker is losing ground in the obesity drug race.

“The US healthcare system is complex, but Novo Nordisk will continue to work to find solutions that help people access the medicines they need at affordable prices,” Novo said in an emailed statement.

Novo’s shares were 4.9% lower at 8.39am. Today’s drop brings this week’s losses to more than 30% – the stock’s worst-ever weekly fall.

The European healthcare index was down 1.6%, its lowest since April.

“Trump doesn’t have the mandate to tell Novo Nordisk how to price their products in the US, but investors are just panicking about the risk of another downgrade,” said Nordnet analyst Per Hansen.

The pressure to lower prices adds to Novo’s problems in the US, its biggest market.

It faces competition from Eli Lilly and from compounders – custom-made medicines that are based on the same ingredients as branded drugs.

“This is a repricing of the obesity market, it’s a repricing of the US as the world’s most attractive drug market, and it’s a repricing of the risk from Donald Trump,” Hansen said.