Shares of (NYSE: PFE) were sinking 4.4% lower as of 11:10 a.m. ET on Friday after falling as much as 7.1% earlier in the morning. The sell-off came after the company announced that it's throwing in the towel on a twice-daily version of experimental weight-loss pill danuglipron.

Pfizer made the decision based on results from a phase 2b clinical study of danuglipron. This study achieved its primary endpoint, with patients experiencing placebo-adjusted weight loss between 5% and 9% at 26 weeks and between 8% and 13% at 32 weeks. However, there were high rates of side effects (up to 73% of patients experienced nausea and up to 47% experienced vomiting). Discontinuation rates were also very high -- above 50%.

There was simply no way that Pfizer could advance the twice-daily version of danuglipron into phase 3 testing with the dismal adverse event and discontinuation numbers. But how bad was this news for Pfizer? Pretty bad.

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Source Fool.com