Eli Lilly missed forecasts in the first quarter.
That as the rollout of vaccines hit demand for its COVID-19 antibody therapies.
Overall net earnings dropped 7% to $1.36 billion.
Sales of COVID-19 drugs came in at just over $810 million - when analysts had forecast something nearer to a billion.
Demand for antibody medicines has also been hit by complexities in administering the treatments.
And the U.S. government last month stopped distributing one Lilly product over fears it would not be effective against new variants of the virus.
The firm is now focusing on treatments featuring a combination of drugs.
Lilly now expects adjusted full-year earnings of up to $8 per share, down from a previous estimate of up to $8.40.