An experimental weight-loss injection, nicknamed 'Godzilla' and known as retatrutide, may soon surpass the effectiveness of Mounjaro, the current leading "King Kong" of weight-loss drugs, according to a new study. Researchers found that retatrutide has the potential to help patients lose nearly a quarter of their body weight after 48 weeks, a rate higher than that observed with tirzepatide, the active ingredient in Mounjaro.
Tirzepatide, which mimics two appetite-regulating hormones (GLP-1 and GIP), has been shown to help patients shed over a fifth of their body weight in approximately 17 months. However, retatrutide, a "triple agonist" that also targets the hormone glucagon, has demonstrated even greater efficacy in preliminary trials. Glucagon is thought to increase the body's energy expenditure, potentially contributing to the higher weight loss observed.
Another experimental drug, amycretin, which targets GLP-1 and amylin (a hormone that signals fullness), has also shown comparable weight loss results to retatrutide after just 36 weeks. These findings suggest that these emerging treatments could become the most potent weight-loss interventions developed to date if approved by health officials.
For comparison, existing popular GLP-1 receptor agonists like semaglutide, the active ingredient in Wegovy and Ozempic, can lead to weight loss of up to 18.7 percent over a similar period. Newer oral treatments, such as the Wegovy pill (semaglutide) and Foundayo (orforglipron), have also shown significant results, with the Wegovy pill facilitating up to 15.5 percent weight loss over 68 weeks and Foundayo achieving up to 14.7 percent over 36 weeks.
The systematic review, which analyzed 38 trials involving over 25,000 participants, compared the safety and efficacy of various weight-loss drugs against placebos. The research, published in the Annals of Internal Medicine, included an examination of new experimental drugs like retatrutide and amycretin.
Regarding side effects, the review noted that approximately 76 percent of participants taking the weight-loss drugs reported gastrointestinal issues such as diarrhea, vomiting, nausea, and constipation, compared to about 40 percent in the placebo group. Around 10 percent of patients discontinued the drugs due to these side effects. Rare instances of severe biliary disorders, pancreatitis, psychiatric disorders, and six deaths were also reported in the trials.
It is important to note that the researchers indicated that the differences in trial designs for each drug mean the results cannot be directly compared. Additionally, separate official drug safety data has linked hundreds of deaths and tens of thousands of adverse reactions to some of these weight-loss medications, although the reports do not definitively prove causation.