Eli Lilly’s Zepbound is still viewed as the leading weight-loss shot, according to a market analyst who compared the drug to a rival injection from Pfizer. The comment comes as drugmakers race to meet rising demand for obesity treatments in the United States and abroad.
The analyst said the clinical and commercial momentum favors Lilly at this stage, citing trial results, physician adoption, and early sales for tirzepatide, the active ingredient in Zepbound. Pfizer, which is advancing its own program, faces a higher bar as it seeks to enter a crowded field anchored by Lilly and Novo Nordisk.
“Eli Lilly’s Zepbound still looks like the heavyweight in weight loss compared to Pfizer’s injection,” the analyst said.
How Zepbound Reached the Front of the Pack
Zepbound, approved by U.S. regulators in late 2023 for chronic weight management, builds on tirzepatide’s record in type 2 diabetes under the brand Mounjaro. The drug targets two hormones involved in appetite and glucose control. That approach produced large weight reductions in late-stage studies.
In the SURMOUNT program, patients on tirzepatide achieved average weight loss of about 15% to more than 20% at 72 weeks, depending on the dose and trial group. Doctors have cited the magnitude of loss, along with improvements in metabolic measures, as key reasons for adopting the medicine.
By contrast, Pfizer’s efforts are earlier. The company has been developing weight-loss candidates, including an experimental injection. It is seeking a profile that can match or outdo established GLP-1 based therapies on weight loss, side effects, and dosing convenience.
Comparing Efficacy, Tolerability, and Dosing
Analysts often judge weight-loss drugs on three basics: how much weight patients lose, how well they tolerate the therapy, and how easy it is to take. On available data, Lilly has an advantage on the first measure. The tirzepatide program has shown double-digit percentage weight loss across several trials and populations.
Gastrointestinal side effects such as nausea and diarrhea remain common for the class. Physicians manage them with slow dose escalation and diet counseling. The analyst suggested that any new entrant will need either stronger weight loss, a gentler side-effect profile, or a simpler schedule to shift prescriber habits.
- Efficacy: Tirzepatide has shown 15%–20%+ average weight loss over 72 weeks.
- Tolerability: GI symptoms are typical but often manageable with titration.
- Dosing: Zepbound is a once-weekly injection; convenience is a factor for long-term use.
Supply, Access, and Real-World Constraints
Strong demand has strained supplies for anti-obesity drugs across the class. Lilly has invested in manufacturing expansion to ease shortages and support growth. Access is also shaped by insurance coverage, which varies widely for weight-loss indications in the United States.
For Pfizer, entering a market facing supply pressure could be a mixed picture. A new option might find ready demand, but only if production scales and coverage aligns. The analyst noted that reliability of supply can be as important as headline trial results in winning prescriber loyalty.
Competition From Novo Nordisk and Others
Novo Nordisk’s semaglutide, sold as Wegovy for obesity and Ozempic for diabetes, remains a major force. Semaglutide has shown around 15% average weight loss in studies and gained wider uptake after trial data suggested a reduction in cardiovascular risk for some patients with obesity.
This sets a high benchmark for any new product. To carve out share, Pfizer must show clear gains on weight reduction, fewer side effects, or added health benefits. Pricing and payer negotiations will also influence how quickly a new therapy can scale.
Investor View and What Comes Next
The analyst’s read favors Lilly in the near term, given established data, physician comfort, and brand momentum. Pfizer’s injection, still in development, will face scrutiny over study design, endpoints, and safety signals as more results arrive.
Key milestones to watch include head-to-head or cross-trial comparisons, longer-term outcomes on cardiovascular and metabolic health, and any signs of improved tolerability. Manufacturing updates and payer coverage decisions will also guide uptake across the class.
Lilly enters the next phase with a lead in efficacy and market presence. Pfizer’s path will depend on delivering convincing clinical data and a reliable supply plan. For patients and clinicians, the main questions remain steady weight loss, manageable side effects, and access. The next wave of trial readouts and capacity updates will show whether the current leader can extend its advantage or face a stronger challenge.
