Shares of Danish pharmaceutical giant Novo Nordisk slid 2.5% on Friday, extending a 2.7% loss on Thursday as analysts pored over the details of the firm's first-quarter results and monitored a potential rival weight loss treatment.

The company reported that sales for its blockbuster injectable weight loss treatment Wegovy, more than doubled to 9.38 billion Danish kroner ($1.4 billion). Novo Nordisk, which also makes diabetes treatment Ozempic, said the rise in sales had offset a slight reduction in prices.

Novo Nordisk expects prices to drop further as new entrants enter the market, CFO Karsten Knudsen said on a media call, adding that the company was not seeing much evidence of Wegovy users moving to other rival treatments.

Analysts expected even higher weight loss drug sales in the quarter, and some noted that Novo Nordisk's 2024 outlook raise for both sales growth and operating profit was due to one-off accounting adjustments.

"While we continue to see Novo as a wide-moat firm, with strong intangible assets surrounding its cardiometabolic business, we think high obesity drug demand and a scarcity of supply have driven share prices above their intrinsic value," Karen Andersen, strategist at Morningstar, said in a Thursday note.

The boom in demand for weight loss treatments saw Novo Nordisk overtake French luxury group LVMH to become Europe's most valuable company last year. Shares gained 49% in 2023 and are up 25% year to date.