What happened

Shares of the Danish pharma giant Novo Nordisk (NVO 2.70%) were down by 3.4% on elevated volume as of 1:14 p.m. ET Tuesday afternoon. The drugmaker's shares are falling in response to the strong mid-stage data for Pfizer's orally administered diabetes and weight loss drug, danuglipron, which were published yesterday in JAMA Network medical journal.

So what

What's the big deal? Novo's shares have more than doubled in value over the prior two years, thanks to the breakout success of its type 2 diabetes and weight loss drug semaglutide. In the U.S., semaglutide is sold under the brand names Ozempic (injected version) or Rybelsus (pill form) for diabetes, and Wegovy (an injected therapy) for weight loss.

Wall Street analysts previously thought that semaglutide could haul in an astonishing $47 billion in annual sales by 2031, despite stiff competition from Eli Lilly's Mounjaro in both the type 2 diabetes and weight loss settings. With Pfizer developing another formidable competitor, Novo's flagship medication may fail to live up to these enormous sales forecasts. 

Now what

Is Novo's stock a buy on this weakness? With one of the highest valuations within the big pharma space prior to this downturn, it's pretty clear that investors were counting on semaglutide to deliver stellar levels of growth for years to come. However, Novo's core value proposition will ultimately depend on a host of moving parts that are outside of the company's control. This mid-stage win by rival Pfizer is a case in point. As such, it might be better to wait for a more compelling entry point into this highflying big pharma stock