What to know about retatrutide, the next game-changing weight-loss drug scientists are excited about

• New medication retatrutide is undergoing testing for use to treat diabetes and boost weight loss.
• A similar "game changer" weight loss drug called semaglutide was approved in 2021 and quickly sold out.

A potential new weight loss drug is undergoing continued research, on the heels of other blockbuster medications like semaglutide that are changing how the medical industry approaches weight management.

Retatrutide is a once-weekly injection from pharmaceutical company Eli Lilly, which is in the process of completing phase 2 trials to study the drug for both weight loss and managing type 2 diabetes.

The testing follows the approval of weight loss medication semaglutide in 2021, a once-weekly injectable medication originally used to treat diabetes. Experts called it a "game changer" for weight loss, and it quickly sold out. A similarly promising diabetes drug called tirzepatide, also a weekly injection, is awaiting FDA approval for weight loss.

Both work by mimicking a hormone called GLP-1, which helps regulate blood sugar and can make people feel full more quickly after eating.

Retatrutide works similarly, but in addition to GLP-1, it also acts on two other hormones. One, called glucose-dependent insulinotropic polypeptide (GIP), also helps manage blood sugar.

The other, called glucagon, may help suppress appetite and increase energy expenditure, so you eat fewer calories and burn more, evidence suggests.

A spokesperson for Eli Lilly said that the combined effects are "expected to deliver significantly more weight loss" than other weight loss medications, based on current research.

Preliminary analysis from phase 2 trials indicated people taking retatrutide with obesity (a body mass index of 30 or higher), but not diabetes, could lose up to 24% of their body weight in 48 weeks, Investors Business Daily reported. That's more weight loss at a faster rate than trial results for tirzepatide, which led to 20% reduction in body weight in 72 weeks.

Currently, the overall safety profile of retatrutide is comparable to similar medications, according to the Eli Lilly spokesperson. Semaglutide is linked to some side effects such as nausea, but it considered to be as safe as other routinely used prescription medications, Dr. W. Scott Butsch, director of obesity medicine at the Cleveland Clinic, previously told Insider.

The Eli Lilly spokesperson said the company is currently completing data analysis from phase 2 trial results, and plans to share more detailed information on the results, including safety information, at the 2023 American Diabetes Association Scientific Sessions conference scheduled for June 23 to 26.

More details on the full timeline for the drug, including phase 3 trials, will be announced in 2023, according to the spokesperson.