COPENHAGEN (Reuters) -Shares in Novo Nordisk fell at opening on Friday, after the Wegovy-maker and rival Eli Lilly ( LLY ) struck a deal late on Thursday with U.S. President Donald Trump to slash prices of their GLP-1 weight-loss drugs.

Novo's shares traded 2.3% lower at opening in an overall flat market on the Copenhagen stock exchange. 

The deal will lower prices for Novo's and Eli Lilly's ( LLY ) popular weight-loss drugs for the U.S. government's programs, as well as for cash payers and give wider access to patients under Medicare. The companies will also get relief from tariffs for three years as part of the deal. 

Novo said the deal would have a negative "low single-digit" impact on global sales growth next year as a result of the lower prices, while bigger volumes under Medicare were expected in the mid- to long-term.