Pharmaceutical giant Pfizer has just declared mid-stage trial results for berobenatide, an experimental anti-obesity and diabetes drug designed to be taken just once a month.
If approved, it could become the first GLP-1 weight-loss therapy (which mimics the gut hormone GLP-1 to regulate blood sugar, slow stomach emptying and reduce appetite) to be administered as a once-a-month injection instead of weekly jabs.
The drug is drawing attention not just for weight loss but convenience. Current blockbuster obesity drugs typically require weekly injections. Pfizer’s candidate aims to reduce that burden dramatically. Patients would initially receive weekly doses before transitioning to a single injection every month.
For people managing obesity as a chronic condition, that would ultimately mean 12 injections a year instead of 52. In a mid-stage clinical study known as VESPER-3, patients without diabetes lost up to 12.3% of their body weight. Importantly, those who switched to monthly dosing continued to lose weight rather than hitting a plateau.
Wegovy (semaglutide) produced about 15% average weight loss in its pivotal late-stage STEP 1 trial over 68 weeks. Zepbound (tirzepatide, which has GIP hormone along with GLP-1) has shown even greater weight loss, averaging around 20% or more in some late-stage studies.
“However, we should not compare the percentage of weight loss. Less frequent dosing has the potential to improve treatment persistence, which is a major determinant of long-term success in obesity management,” says Dr Anoop Misra, Chairman at Fortis CDOC Hospital for Diabetes and Allied Sciences and former professor, AIIMS, Delhi. He spoke to Rinku Ghosh about the significance of the new treatment.
Pfizer’s berobenatide is being positioned as a once-monthly GLP-1 therapy. How significant is this development from a patient adherence and treatment-compliance perspective?
Berobenatide is currently transitioning into a robust global phase 3 development programme (the VESPER program), which consists of 10 planned or ongoing late-stage clinical trials. It is expected to be available for patients around late 2028 to mid-2029 The drug has been engineered to remain in circulation much longer than conventional GLP-1 therapies, allowing sustained activation of GLP-1 receptors throughout the month.
From an Indian perspective, a once-monthly GLP-1 injection is an important advance because long-term adherence remains a major challenge in any treatment in India. Less frequent dosing may reduce treatment fatigue, improve convenience and help patients remain on therapy for longer periods.
The drug showed up to 12.3% weight loss in a mid-stage trial. How should clinicians interpret these results in comparison with established therapies such as Wegovy, Zepbound and Mounjaro?
Clinicians should avoid direct comparisons across trials. The reported weight loss is clinically meaningful and encouraging for monthly therapy. However, semaglutide (Wegovy) and especially tirzepatide (Zepbound, Mounjaro) have demonstrated substantial weight reductions in larger and longer studies. At present, berobenatide appears promising, but its major differentiating feature may be monthly administration rather than weight-loss efficacy.
Pfizer says the side-effect profile appears broadly comparable to existing GLP-1 drugs. What will experts and regulators be looking for in late-stage trials before judging its clinical value?
Experts and regulators will focus on the durability of weight loss, long-term safety, gastrointestinal side effects, discontinuation rates, and cardiovascular and kidney benefits. They will also examine whether the extended drug exposure over an entire month leads to any unique safety concerns. In that way, it may undergo similar scrutiny as once-a-month insulin.
Could less frequent dosing improve long-term outcomes for people living with obesity, or are efficacy and side effects still likely to be the deciding factors?
Less frequent dosing has the potential to improve treatment persistence, which is a major determinant of long-term success in obesity management. However, efficacy and tolerability will continue to be the most important factors. A monthly injection is attractive, but patients and clinicians will ultimately prioritise how much weight is lost, how well it is maintained, and whether side effects remain manageable. Other long term data (especially cardiac) are clearly needed to address these concerns.
GLP-1 drugs are increasingly being viewed as long-term treatments for a chronic disease. How might a monthly injection change the way obesity is managed in routine clinical practice?
A monthly injection could further strengthen the concept of obesity as a chronic disease requiring long-term treatment, similar to diabetes or hypertension. In India, it may improve patient acceptance, reduce the burden of frequent injections, and facilitate longer-term treatment engagement. This could be particularly useful in busy clinical settings and for patients who find weekly injections inconvenient. This may also ensure that the patient remains on treatment for a longer period of time which is needed both for obesity and diabetes.
Looking ahead, do you see the future of obesity treatment moving toward longer-acting therapies, combination drugs, or more personalised approaches based on patient profiles?
The future is likely to involve all three. Use of any drug will depend on efficacy on weight, blood glucose levels and proven cardiovascular and renal benefits. Finally, ease of administration (once monthly) and cost are important determinants. Further, personalised approaches based on liver disease (liver fibrosis), presence of obstructive sleep apnea, knee osteoarthritis, etc, are likely to guide treatment selection. For India, where obesity and diabetes present with considerable heterogeneity, personalised obesity medicine may become increasingly important.
Current blockbuster obesity drugs such as Ozempic typically require weekly injections. Wikimedia Commons 
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