Pfizer has decided to discontinue the development of the twice-daily version of its experimental weight loss pill after obese patients experienced significant weight loss but struggled to tolerate the drug during a mid-stage clinical study, the company announced on Friday.
The drugmaker cited high rates of adverse side effects, primarily gastrointestinal and mostly mild in nature, as a reason for discontinuing the formulation. Additionally, a significant number of patients stopped taking the drug. Shares of Pfizer fell 4% following the trial results.
While the twice-daily version of the drug will not move into Phase 3 studies, Pfizer plans to release data on a once-a-day version of the drug in the first half of 2024. The company will decide on conducting a phase three study on the once-daily pill based on the upcoming data.
Pfizer’s hope to capture a portion of the growing weight loss drug market is at risk following the setback with the twice-daily drug. With competitors like Eli Lilly and Novo Nordisk racing to develop pill versions of their successful weight loss and diabetes treatments, Pfizer is facing increasing challenges in this space. The company’s once-daily pill aims to mimic a gut-produced hormone called GLP-1 which signals to the brain when the body is full.
Pfizer’s phase two trial on the twice-daily pill showed “statistically significant” reductions in body weight, with patients losing between 6.9% and 11.7% of their body weight at 32 weeks. However, tolerability issues were a cause for concern, as up to 73% of patients experienced nausea, up to 47% experienced vomiting, and up to 25% had diarrhea. More than 50% of patients stopped taking the pill.
Analysts had anticipated patient intolerance to the higher total daily dose of Pfizer’s pill compared to competing products from Eli Lilly and Novo Nordisk. The company believes that a once-daily version could improve patient tolerability and reduce gastrointestinal side effects, but it remains to be seen how the mid-stage trial data will unfold next year.