Eli Lilly said sales of weight loss drug Zepbound and diabetes treatment Mounjaro soared in the first quarter.

Eli Lilly on Thursday posted better-than-expected quarterly results, although sales of its popular weight-loss drug, Zepbound, came in slightly below Wall Street estimates, sending its shares down 4% in premarket trading.

Eli Lilly ( LLY 2.92%) has been growing its sales at a good clip over the past year. This is partly thanks to Zepbound, a weight loss medicine that's already generating more than $1 billion in quarterly sales, although it was approved only in late 2023.