Pfizer's twice-daily weight-loss pill discontinued due to side effects

Weight loss with Ozempic or Wegovy requires patients to inject themselves with the medication — a reported drawback for some people. That's why Pfizer and other drug manufacturers are racing for approval of a weight-loss drug that can be taken as a pill.

While some headlines have already proclaimed Pfizer's version, danuglipron, as potentially “the next Ozempic in pill form” and more “user-friendly” than similar treatments, experts say it’s still early in the process to say for sure.

“It needs to be studied on a larger scale and for a longer duration before we can really understand its true impact,” Dr. Christopher McGowan, an obesity medicine specialist in Cary, North Carolina, tells McGowan was not involved in the Pfizer study.

“The important thing is patients can take this by mouth rather than an injection… patients would always prefer to take something by mouth in general.”

Patients also need more options when it comes to weight-loss drugs, so a new medication would be welcome, adds Dr. William Yancy, medical director of the Duke Lifestyle and Weight Management Center, in Durham, North Carolina, who was also not involved in the study.

“No. 1, it may drive down prices, which are still very high,” Yancy says. “No. 2, the pill form may be preferable to some patients. No. 3, the side effects may be different.”

But it could be years before the new drug gets approval and becomes available on the market, McGowan notes.

What is Pfizer’s weight-loss drug?

Known as danuglipron, the diabetes and obesity treatment is in a class of drugs called GLP-1 agonists and mimics a hormone the body releases when a person eats food. People have reduced appetite, and when they do eat, they feel full sooner, as previously reported. Semaglutide, the active ingredient in Ozempic and Wegovy, is also in this class of drugs.

Danuglipron comes in pill form. Unlike oral semaglutide, which is currently available as the Type 2 diabetes treatment Rybelsus, it doesn’t require fasting before or after taking the pill.

Danuglipron was being tested as both a twice-daily and once-daily pill. Pfizer announced on Dec. 1 that it was discontinuing phase 3 clinical trials of the twice-daily version due to high rates of adverse side effects. While these were mostly mild, a large percentage of participants, who had obesity, experienced them: up to 73% had nausea; up to 47% had vomiting, and up to 25% had diarrhea. Over half of participants, all adults with obesity, discontinued the medication during the study.

The company said that it still plans to release data on its once-daily version of danuglipron next year, which will "inform a path forward" regarding pursuing approval for the medication.

The clinical trial did find that twice-daily danuglipron led to "statistically significant" weight loss, the company said: Participants were down between 8% to 13% of their body weight on average after 32 weeks on the medication, and 5% to 9% after 26 weeks.

A previous phase 2 trial in adults with Type 2 diabetes also found that when people took danuglipron twice a day for four months, their body weight was “statistically significantly reduced” compared to a placebo. The results were published in JAMA Network in May 2023.

Study participants who took the highest dose of danuglipron — 120 milligrams, twice daily — lost about 10 pounds in 16 weeks, researchers reported. The paper didn’t directly compare those results to Ozempic or Wegovy, but a phase 3 trial showed patients who received a once-weekly 1 milligram injection of semaglutide lost about 10 pounds in 30 weeks.

Does Pfizer have a weight-loss pill that’s better than Ozempic?

When it comes to effectiveness, it’s a little early to say, McGowan notes.

Danuglipron and semaglutide are different molecules so the dosages can’t be directly compared, but in general, the oral dose required to achieve the same results as an injectable version is significantly higher because the digestive tract is a “more challenging route for absorption,” McGowan says.

The trials were different studies with different populations so they can’t be directly compared, McGowan says.

“Unless you do a direct head-to-head comparison, you really can’t make any definitive conclusions,” he adds.

“But what we can say is that the results are in the same ballpark as what we’ve seen with Ozempic.”

What are the side effects?

The most common side effects of danuglipron were nausea, diarrhea and vomiting, according to the studies.

McGown says the rates of discontinuation of danuglipron are "most concerning" because they may mean the drug will "not be acceptable for widespread use."

Adverse events that emerged during treatment were the most common reason for discontinuation, researchers reported in the Pfizer studies.

The most commonly reported adverse events were gastrointestinal in nature, according to the Pfizer studies. They were mild, more common with higher doses and known to be associated with GLP-1 agonists, Pfizer said in a statement to

In comparison, about 7% of patients treated with Wegovy in clinical trials permanently stopped taking the drug because of adverse reactions, according to Novo Nordisk, which makes Wegovy, the version of Ozempic approved for weight loss.

The most common adverse reactions leading patients to discontinue Wegovy were nausea, vomiting and diarrhea, the company reported. In all, about 4% of patients stopped taking the drug because of a gastrointestinal adverse reaction, it noted.

Danuglipron approval

“We’re still years away with the Pfizer product,” McGowan says.

Pfizer is also testing another oral GLP-1 drug called lotiglipron, which would be taken once a day. It’s currently at the phase 2 trial stage, according to the company’s drug pipeline information.

Pfizer is expected to advance only one of the two drugs into a late-stage trial, Barron’s and Reuters reported.

Pfizer didn’t confirm those reports to

What are the pros and cons of the pill form?

Yancy says this will be helpful for people who wish to avoid injections, though most of his patients find the once-weekly shots are easy to perform and not bothersome.

Another advantage is that there’s no requirement for refrigeration with the pill version, McGowan adds.

A potential downside is that people might forget to take a daily drug, he notes.

Are there other pill forms of GLP-1 for weight loss?

In May 2023, Novo Nordisk announced that obese or overweight adults who took a once-daily 50 milligram dose of oral semaglutide for 68 weeks lost 15% of their body weight. The findings are based on results from a phase 3 study that involved 667 people.

The weight loss was comparable to that achieved with a 2.4 milligram dose of semaglutide injected once a week in the form of Wegovy over the same time frame, the company said in a statement.

Oral semaglutide appeared to be “safe and well-tolerated,” with the most common side effects described as mild to moderate gastrointestinal adverse events, the statement added.

Patients have to take the drug on an empty stomach first thing in the morning with a sip of water and must then wait 30 minutes before they can eat or drink, similar to the directions for Rybelsus, a spokeswoman for Novo Nordisk tells Pfizer’s danuglipron doesn’t have those restrictions, the authors of the JAMA Network study noted.

In its statement, Novo Nordisk says it expects to file for regulatory approval in the U.S. this year.

This article was originally published on