Pfizer, Inc. announced that it is discontinuing development of its experimental daily weight loss pill after a trial participant suffered a liver injury potentially linked to the drug. The company confirmed that the oral GLP-1 drug, danuglipron (PF-06882961), is no longer in development following the incident.1 Pfizer has been studying danuglipron since 2022.2
A Pfizer spokesperson said the drug potentially caused liver injury in a patient in the trial, adding that the patient did not experience any liver-related symptoms. The spokesperson explained that the patient’s liver enzymes were elevated but “recovered rapidly” after stopping the danuglipron. Elevated liver enzymes, which often indicate cell damage in the liver, is an adverse health outcome that has been linked to some other obesity drugs.
The Pfizer spokesperson explained that the trial quickly increased the pill’s dose over a short period. Pfizer halted the weight loss drug’s development after it reviewed all clinical data for danuglipron and considered recent input from regulators, according to a release.3
Pfizer said a Phase 2 study met key pharmacokinetic (how the drug is absorbed, processed and cleared by the body) goals and showed competitive efficacy and tolerability in Phase 3 testing. More than 1,400 participants who took the experimental drug experienced elevated liver enzymes, similar to levels seen with other approved medications; however, one participant experienced more serious issues.4
Pfizer plans to share the results of its clinical trials for danuglipron at a scientific meeting or submit them for review in a scientific peer-reviewed journal. Chris Boshoff, MD, PhD, who serves as Pfizer’s Chief Scientific Officer and President of Research and Development, confirmed that the company is also focusing on the development of additional weight-loss drugs.5
Pfizer abandoned the twice-daily version of danuglipron in 2023 after trial participants experienced vomiting and nausea. In 2024, they shifted focus to developing a once-daily pill, which they believed could have offered a competitive edge over other weight-loss medications taken twice daily. Several companies are now working on weight-loss pills, following the surge in popularity of injectable drugs that target the GLP-1 hormone. Ozempic and Wegovy, two popular injectables, are linked to GLP-1.6
Smaller Weight Loss Drugmakers Gain Ground After Pfizer Ends Trial
Pfizer’s decision to end the trial of their weight loss drug gave a boost to two smaller drug makers, Structure Therapeutics and Viking Therapeutics. Both companies are developing similar weight-loss pills and Pfizer’s withdrawal gives these companies a better chance at bringing their own weight loss pills to market.
Bigger companies like Novo Nordisk and Eli Lilly still lead the weight-loss drug market with popular injectables like Ozempic, Wegovy, and Mounjaro.7 Novo Nordisk and Eli Lilly are cutting prices for patients who pay out of pocket and expanding access through self-pay pharmacy programs, making their drugs more affordable for people without insurance.8
Weight Loss Drugs Have Many Documented Adverse Side Effects
The side effects of weight-loss drugs like Ozempic, Wegovy, and Mounjaro include serious health risks such as gastroparesis (stomach paralysis), which can lead to chronic vomiting and complications like dehydration and malnutrition. The drugs can also cause significant issues during surgery, with a risk of food regurgitation and aspiration into the lungs, potentially leading to pneumonia.
Additionally, there have been reports linking these medications to increased suicidal thoughts and depression, prompting investigations by health authorities in the U.K. and E.U. While the U.S. Food and Drug Administration (FDA) requires warnings for depression and suicide risks for Wegovy, such warnings are not on the packaging for Ozempic, which is only FDA-approved for diabetes treatment.9
More serious risks include thyroid tumors, pancreatitis, kidney failure, gallbladder problems, and changes in vision. Additionally, these drugs have been linked to liver damage, and a black box warning highlights the potential risk of thyroid C-cell tumors in animals, though it’s still uncertain if this applies to humans. The long-term effects of these medications remain unclear.10
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Click here to view References:1 Constantino AK. Pfizer will end development of weight-loss pill over fears about its impact to the liver. CNBC Apr. 14, 2025.
2 Cone A. Pfizer ends development of weight-loss pill after patient’s liver injury. UPI Apr. 14, 2025.
3 Constantino AK. Pfizer will end development of weight-loss pill over fears about its impact to the liver. CNBC Apr. 14, 2025.
4 Ibid.
5 Cone A. Pfizer ends development of weight-loss pill after patient’s liver injury. UPI Apr. 14, 2025.
6 Pfizer. Pfizer Announces Topline Phase 2b Results of Oral GLP-1R Agonist, Danuglipron, in Adults with Obesity. Dec. 1, 2023.
7 Yahoo Finance. Smaller obesity drugmakers jump after Pfizer scraps weight-loss pill. Apr. 15, 2025.
8 Genovese D. Pfizer will end development of daily weight-loss pill after liver injury. Fox Business Apr. 14, 2025.
9 Baker A. Popular Weight-Loss Drugs Linked to Stomach Paralysis, Suicide and More. The Vaccine Reaction Aug. 21, 2023.
10 Baker A. Ozempic Weight Loss Drug Linked to Increased Risk of Thyroid Cancers. The Vaccine Reaction Jul. 23, 2023.
One Response
You can’t safely inject health. And you can’t safely take weight off by popping pills. Fatties of the world need to hit the gym and put down the diet soda. For all the money wasted on this drug research for weight loss, they could have put free exercise equipment up in a thousand parks across America or provided national advisement on the dangers of chemicals and trusting pharmaceuticals to be miracle solutions to everything. What a waste of time resource and effort.
Studying what takes the weight off. (puts on white lab coat. Chews on end of pencil. Stares intensely at grid and graph work. Gets on phone. Ponders the data. Checks stock options for the most profitable avenue of ‘invention’ that may be possible. Proclaims Eureka!) Who’s still buying this?
How about researching what puts weight on. Like too much screen time. Ionizing radiation from cell phones, wireless devices, and other technology which compromises the blood. Genetically modified foods your body can not digest properly. Diet sodas. High fructose corn syrup which is undisclosed in almost all ‘conventional’ foods. The additives, dyes, preservatives, nutritionally devoid food like appearing substances. The environmental toxins everywhere raining down on us. The excess cost of safe staple food and the artificially low cost of dangerous pesticide and preservative laden foods.
The completely annoying and unhealthy trend of shaming people in good shape and saying we can’t poke fun at obese people anymore to help whip them into better shape. One wonders if they’ve ever personally experienced to joy of a person like this ruining their couch or compromising kitchen chairs with one single sitting. True story. Sorry, still not buying this. However; Never make fun of an overweight person on a bicycle. They are exactly where they need to be.