Pfizer Abandons Obesity Drug Development Over Safety Concerns

The decision is another setback for Pfizer as it seeks a foothold in the obesity drug market.

A Pfizer office in a file image. Johanna Geron/Reuters

Pfizer has discontinued development of its once-a-day oral weight-loss drug, danuglipron, after identifying a potential case of liver injury during clinical trials.

The company announced on April 14 that a participant in one of its studies showed signs of possible liver damage, which resolved after discontinuing the medication. While Pfizer noted that liver enzyme elevations in more than 1,400 patients treated to date were “in line” with those seen in other approved GLP-1 therapies, the safety concern was significant enough to call off further development.

As a result, the company said it will redirect resources toward earlier-stage candidates in its obesity treatment pipeline.

“While we are disappointed to discontinue the development of danuglipron, we remain committed to evaluating and advancing promising programs in an effort to bring innovative new medicines to patients,” Chris Boshoff, Pfizer’s chief scientific officer and president of research and development, said in a statement.

Pfizer said data from the danuglipron clinical program will be submitted for publication in a peer-reviewed journal or presented at a future scientific forum.

The decision is another setback for Pfizer as it seeks a foothold in the rapidly growing obesity drug market, which is projected to exceed $100 billion by the end of the decade. That market has become central to Pfizer’s post-COVID-19 strategy as revenues from pandemic-era vaccine and antiviral sales continue to decline.

Danuglipron, like other drugs in its class—such as Novo Nordisk’s Wegovy and Eli Lilly’s Zepbound—is a GLP-1 receptor agonist. It works by stimulating insulin release in response to elevated blood sugar levels and by slowing down stomach emptying, which helps reduce appetite. Pfizer had hoped that an effective and more convenient oral formulation would allow danuglipron to carve out a competitive niche in a market currently dominated by injectable therapies.

Despite its well-established mechanism, danuglipron has struggled with tolerability in Pfizer’s clinical trials. In December 2023, Pfizer stopped testing danuglipron as a twice-a-day pill after reporting high rates of gastrointestinal side effects in a mid-stage study.

Among roughly 1,400 participants, up to 73 percent of those treated experienced nausea, while 47 percent reported vomiting and 25 percent had diarrhea, Pfizer said at that time. Discontinuation rates for the trial were more than 50 percent across all dosage forms, compared with 40 percent in the placebo group.

With danuglipron shelved, Pfizer’s clinical-stage obesity pipeline now rests on PF-07976016, an oral medication currently in phase-2 trials that, instead of mimicking the GLP-1 hormone, blocks the action of the GIP receptor, a unique approach among weight-loss drugs. According to federal clinical trial records, that study is expected to reach initial completion in December 2025.