US drugmaker Pfizer on Friday said it would end a clinical trial of its developmental weight loss pill after high side effect rates caused most participants to stop using it. 

A twice-daily dosing of the highly anticipated drug danuglipron was found to be effective, resulting in weight reductions of between 8-13 percent at 32 weeks, compared to a placebo.

But nearly three-quarters of trial participants experienced nausea, almost half had vomiting, and a quarter had diarrhea. 

Consequently, the discontinuation rate was greater than 50 percent, compared to 40 percent on placebo.

"At this time, twice-daily danuglipron formulation will not advance into Phase 3 studies," the US drugmaker said in a statement. 

Pfizer stocks were trading nearly five percent down after the morning announcement.

Danuglipron belongs to a growing field of powerful and lucrative obesity medications known as GLP-1 agonists.

JPMorgan analysts have predicted annual sales for so-called GLP-1 drugs to reach $140 billion by 2032, with the market dominated by Novo Nordisk and Eli Lilly.

Pfizer won't abandon danuglipron entirely but instead focus on improving it and changing the dosing to once a day, the statement added.

"We believe an improved once-daily formulation of danuglipron could play an important role in the obesity treatment paradigm, and we will focus our efforts on gathering the data to understand its potential profile," said Pfizer's Mikael Dolsten.

In October, Pfizer reported a third-quarter loss of $2.4 billion, compared with $8.6 billion in profits in the year-ago period,following a sharp fall in the sales of its Covid-19 vaccine and therapeutic from pandemic peaks.

GLP-1 agonists have been found to cut the risk of cardiovascular disease associated with obesity — but they also heighten the risk of certain severe gastrointestinal problems, studies show.

Novo Nordisk's obesity drug Wegovy cuts the risk of heart attacks and strokes by a fifth, according to a recent study.

But GLP-1 agonists have also been linked with an increased risk of stomach paralysis, pancreatitis and bowel obstruction.