An experimental drug developed by Eli Lilly has shown promising results in providing significant weight loss benefits, surpassing any drug currently on the market. In a mid-stage clinical trial, the drug retatrutide helped participants lose an average of approximately 24% of their body weight, equivalent to around 58 pounds. According to NBC, the findings were presented by the company at the American Diabetes Association's annual meeting in San Diego and simultaneously published in The New England Journal of Medicine.
If the results are confirmed in a larger, phase 3 clinical trial, which is expected to conclude by late 2025, retatrutide could potentially surpass Lilly's other weight loss drug, tirzepatide. Experts had previously predicted that tirzepatide could become the best-selling drug of all time. Currently approved for Type 2 diabetes as Mounjaro, tirzepatide is anticipated to receive FDA approval for weight loss later this year or early next year.
Retatrutide's Effectiveness Approaches Bariatric Surgery
The results of the study have left experts astounded. Dr. Shauna Levy, a specialist in obesity medicine and the medical director of the Tulane Bariatric Center in New Orleans, described the findings as "mind-blowing." She noted that the drug's effectiveness appeared to be approaching that of bariatric surgery, stating, "It's certainly knocking on the door or getting close."
The study highlights the recent surge in the discovery of new treatments for weight loss as pharmaceutical companies invest in GLP-1 agonists, a new class of drugs that mimic a hormone responsible for reducing food intake and appetite. These drugs, including semaglutide and Lilly's tirzepatide, have been transformative for individuals struggling with obesity.
Retatrutide, in addition to mimicking GLP-1 and another hormone called GIP, also mimics glucagon, another hormone that may help reduce appetite and enhance metabolism efficiency. This triple action of retatrutide could explain its superior weight loss efficacy, according to Dr. Holly Lofton, the director of the weight management program at NYU Langone Health.
Eli Lilly's chief scientific and medical officer, Dr. Dan Skovronsky, explained that retatrutide aims to utilize the body's natural signaling molecules responsible for food metabolism and satiety. By turning these molecules into medicines, the drug harnesses the body's own mechanisms to control weight.
In a phase 2 trial that involved 338 obese or overweight adults, retatrutide was administered as a weekly injection. After 48 weeks, patients receiving the highest dose of 12 milligrams lost an average of 24.2% of their body weight, equivalent to 57.8 pounds. Notably, the weight loss had not plateaued by the end of the trial, suggesting that participants could have achieved further weight loss if they had continued taking the medication.
Potential Side Effects: Nausea, Vomiting, and Digestive Issues Among Known Retatrutide Effects
One trial participant, Jucynthia Jessie from Laplace, Louisiana, lost 60 pounds and expressed surprise at the remarkable results. While she has gained some weight since completing the trial, she believes that sustainable weight loss can be maintained through healthy lifestyle choices.
Comparatively, retatrutide exhibited faster weight loss than other medications. Novo Nordisk's semaglutide reduced body weight by approximately 15%, or about 34 pounds, after 68 weeks, while Lilly's tirzepatide resulted in an average weight loss of 22.5%, or about 52 pounds, after 72 weeks. However, direct comparisons cannot be made as these drugs were not evaluated head-to-head in a clinical trial.
Regarding side effects, retatrutide demonstrated a similar profile to other weight loss medications, such as nausea, vomiting, diarrhea, and constipation. These side effects typically diminish with prolonged use.
While awaiting FDA approval, retatrutide's future remains uncertain. Eli Lilly has initiated a phase 3 clinical trial involving thousands of participants, set to conclude in December 2025. If the results continue to hold, the drug will undergo a rigorous review process by the FDA. Furthermore, researchers believe that retatrutide and similar drugs could have potential applications in treating obstructive sleep apnea and reducing the risk of heart disease.
Dr. Skovronsky emphasized the current golden age of drug discovery for treating metabolic diseases, expressing hope that retatrutide could provide weight loss results comparable to bariatric surgery. As different patients may require distinct treatments, he suggested that multiple medications would be necessary, highlighting the importance of continued research and development in this field.
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