Shares of Eli Lilly & Co. fell in New York premarket trading after new industry prescription data for the drugmaker's blockbuster obesity shot Zepbound and recently approved oral weight-loss pill Foundayo disappointed Wall Street analysts.

Foundayo generated 3,707 prescriptions in its second week, according to new prescription-tracking data from IQVIA cited by RBC Capital Markets analysts. That compares with 18,410 prescriptions for Novo's oral version of Wegovy during its second week after launch, suggesting Lilly's weight-loss drugs are falling behind in the GLP-1 race.

"While we believe comparisons early into launch should be considered immaterial, Foundayo's uptake this week is likely to be received negatively," RBC Capital Markets analyst Trung Huynh wrote in a note to clients earlier.

In a separate note citing the IQVIA data, Cantor analyst Carter Gould said, "We see slower TRx (total prescriptions) growth continuing in the injectable segment across diabetes and obesity, though injectable Wegovy notably grew by 7% week over week."

Gould noted, "While we are cautious to make definitive claims off of one week of launch data from IQVIA, we acknowledge that investors will be scrutinizing the numbers, and believe that Foundayo scripts totaling just 20% of what oral Wegovy achieved during their first full week could cause the stock to be weak today."

Shares of Eli Lilly fell as much as 4% in premarket trading. Through Thursday's close, the stock was down 14.6% for the year.

Danske Bank analysts wrote earlier that Novo might hold the lead in obesity pills because Wegovy is a much better product than competitors.