(Reuters) - Shares in Danish drugmaker Novo Nordisk dropped as much as 5.3% on Friday, set for their biggest one-day fall since August 2022, after rival Amgen said it was encouraged by interim trial data on its experimental obesity drug.

Novo Nordisk were last down 4.4% by 1022 GMT, having hit their lowest in two months earlier in the day.

Amgen on Thursday said it was very encouraged after completing an interim analysis of its mid-stage study of experimental weight-loss drug MariTide, which, if approved, would compete Novo's Wegovy and Eli Lilly's Zepbound.

"Novo's share price today is certainly factoring in some negative reaction to Amgen's positive commentary on MariTide development yesterday," Kepler Cheuvreux analyst David Evans said, but added that "a continued negative reaction to results and pricing concerns yesterday is likely also a smaller part of the move today".

Amgen did not provide any specifics on the actual data of its trial, but competition is heating up in a market estimated to be worth as much as $100 billion by the end of the decade, in which Novo Nordisk has the lead for now.