Eli Lilly announced the results of a large clinical trial of a new drug, retatrutide, in which the Washington University Medical Center (UW Medicine) in Seattle was an active participant. As one of the leading academic medical centers in the U.S., UW Medicine regularly takes part in multicenter trials, helping enroll patients, conduct safety and efficacy research, and publish results, which speeds FDA approval of such drugs.
Participants lost substantially more weight than with existing anti-obesity medications. In the 80-week study, subjects receiving the highest dose lost an average of 70 pounds (about 32 kg), or 28% of their starting body weight. Among patients with a body mass index over 35 (moderate to severe obesity), weight loss over two years reached 85 pounds (nearly 39 kg), or 30.3% — roughly comparable to bariatric surgery.
However, this powerful effect was accompanied by side effects. Eleven percent of participants taking the highest dose experienced gastrointestinal symptoms (nausea, vomiting, diarrhea) severe enough to drop out early. That rate is higher than for other weight-loss drugs.
Retatrutide acts on three hormones that regulate appetite and metabolism simultaneously: GLP-1, GIP and glucagon. By comparison, popular drugs like Wegovy and Zepbound affect only one or two of these mechanisms. This triple action likely explains the unprecedented effectiveness of the new drug.
A 12–14% weight loss with oral formulations or about 20% with injections of existing drugs is insufficient for the 24 million Americans with severe obesity (BMI ≥40). They typically need to lose 80–100 pounds. Surgery usually achieves that, but as effective pills appear, demand for surgery has fallen.
Notably, even a low dose of retatrutide produced strong results (about 19% weight loss) while being remarkably well tolerated. More people in the placebo group dropped out due to side effects than in the active-drug group.
Despite the impressive data, the drug is not yet approved by regulators. Meanwhile, Americans have begun ordering counterfeit versions from China online, alarming doctors: patients are not under medical supervision and risk harm. The Port of Seattle, the largest seaport in the U.S. Pacific Northwest through which a significant share of international trade—and pharmaceutical ingredients—passes, could be a channel for importing both legitimate active pharmaceutical ingredients (APIs) and potentially counterfeit drugs, especially from countries with weaker controls. U.S. Customs and Border Protection (CBP) in Seattle inspects containers, but the risk of counterfeit penetration remains.
Separately, Eli Lilly is suing the U.S. Food and Drug Administration over the classification of retatrutide. The company seeks recognition of it as a biologic drug, which would allow a longer monopoly and enable higher prices. The Washington state attorney general could file an amicus curiae brief in support of the state’s position if the suit affects Washington residents’ interests, for example access to affordable drugs including generics or compounded versions of weight-loss medications. A state attorney general’s position is not binding on a federal court but can influence the decision, especially if they argue consumer-rights or antitrust harms.
Experts remind that obesity is a chronic disease, and long-term health impacts matter in addition to pounds lost. If results are confirmed, retatrutide could be a true breakthrough, changing expectations for medical treatment of obesity. In addition to pharmacological approaches, Seattle-based medtech companies such as Accolade and 98point6 offer digital weight-management programs, dietician consultations, and health coaching. These services complement drug treatment by helping patients change lifestyle. Other Seattle startups, for example those focusing on personalized nutrition or fitness apps, are also developing nonpharmacologic approaches to combat obesity.
