Pfizer Halts Development of Oral Weight Loss Pill Due to Safety Concerns
Pfizer announced on Monday the discontinuation of its experimental oral weight loss medication, danuglipron, following a concerning incident during clinical trials where a participant experienced a liver injury that might be associated with the drug. A spokesperson for the company clarified that the individual did not report any symptoms typically linked to liver issues. After ceasing the medication, the participant’s liver enzyme levels returned to normal fairly quickly.
This incident took place during a trial that involved rapidly increasing the medication’s dosage in a short span of time. Pfizer’s decision to halt the drug’s development followed a comprehensive review of available clinical data and feedback from regulatory authorities.
Dr. Chris Boshoff, Pfizer’s chief scientific officer, expressed disappointment over the decision but reaffirmed the company’s commitment to advancing other promising medicines. He emphasized that Pfizer is still committed to exploring alternative weight loss treatments and continues its research efforts in this area.
The termination of danuglipron’s development adds to a series of challenges Pfizer faces in the competitive landscape of GLP-1 medications—specialized drugs that emulate gut hormones, helping to suppress appetite and manage blood sugar levels. Currently, the market is largely dominated by injectable treatments, with Eli Lilly and Novo Nordisk leading the way. Pfizer is working to introduce a more user-friendly oral option but is trailing behind these established competitors.
Industry analysts anticipate that the GLP-1 market could surpass $150 billion by the early 2030s. Within this growing sector, oral formulations are expected to capture around $50 billion, while injectable drugs will account for the remaining share.
Pfizer has had prior setbacks with danuglipron, notably pausing a twice-daily version of the drug in December 2023 due to tolerability issues among patients in earlier studies. However, the company appeared optimistic regarding the once-daily format of danuglipron in July when it announced plans for further studies in the second half of the year to test various doses of the pill.
Interestingly, despite the cancellation of the drug, Pfizer’s latest studies reportedly met crucial objectives and indicated that a specific formulation of danuglipron could deliver competitive efficacy and tolerability in advanced trials. The company also mentioned that the frequency of elevated liver enzymes in trial participants aligns with that seen in currently approved GLP-1 medications, based on a safety assessment of over 1,400 individuals who had taken the pill.
Earlier in June 2023, Pfizer abandoned another once-daily weight loss candidate due to a similar liver enzyme elevation issue encountered during mid-stage trials. This string of disappointments has led to skepticism among investors regarding Pfizer’s prospects in the GLP-1 sector.
Nonetheless, Pfizer is not abandoning its ambitions in the obesity treatment arena. The company is exploring other early-stage experimental obesity drugs, including an oral treatment that inhibits another gut hormone, GIPR, which advanced to phase two trials last year. In addition, a separate once-daily oral GLP-1 is undergoing phase one trials.
Confident in the potential of these new avenues, former Chief Scientific Officer Mikael Dolsten suggested that targeting GIPR might yield a more effective and better-tolerated treatment for patients.
Danuglipron aimed to facilitate weight loss by mimicking GLP-1, a mechanism similar to that of Novo Nordisk’s weight loss injection Wegovy and diabetes drug Ozempic. Eli Lilly’s weight loss injection Zepbound and diabetes medication Mounjaro also focus on GLP-1, along with activation of another gut hormone called GIP.
Currently, the only GLP-1 oral medication authorized by the Food and Drug Administration (FDA) is Novo Nordisk’s Rybelsus, which is primarily utilized for treating Type 2 diabetes and generated approximately $3.38 billion in sales in 2024.
Pfizer’s recent announcement arrives during a period of recovery for the company, as it stabilizes its stock value following a decline tied to its Covid-19 related revenues. The pharmaceutical giant is banking on its pipeline of cancer drugs to provide sustainable growth while maintaining a keen interest in obesity treatment as a core focus moving forward.
