Pfizer and Amgen test monthly GLP-1 shots for weight loss
The drugmakers are developing longer-lasting GLP-1 injections that could reduce dosing from weekly shots to once a month.
By Tom Brennan · Health & Medicine Correspondent
4 min read
Pfizer and Amgen are testing weight-loss injections designed to last a month, a shift that could cut GLP-1 shots from 52 a year to 12. The companies say less frequent dosing could make the drugs easier for patients to keep taking.
The effort targets a practical problem in obesity treatment: adherence. Dr. Christopher McGowan, a gastroenterologist who runs a weight-loss clinic in Cary, North Carolina, said patients have more chances to miss treatment when a drug must be taken more often.
Dr. John Buse, an endocrinologist at the University of North Carolina School of Medicine who worked on Pfizer’s trial, said patients are interested in monthly dosing because it sharply reduces the number of injections.
How the monthly drugs differ
Current GLP-1 drugs, including semaglutide in Ozempic and Wegovy, act on the GLP-1 receptor, which is involved in blood sugar control and appetite. Tirzepatide, the active ingredient in Mounjaro and Zepbound, also acts on a second receptor, GIP. Eli Lilly’s experimental retatrutide adds a third target.
Those drugs are generally given weekly because the body starts breaking down their active ingredients after about seven days. Pfizer and Amgen are trying to extend that window with new designs that keep the drug active longer.
Pfizer’s experimental drug, berobenatide, is designed to remain attached for longer to albumin, a protein in the blood that can help protect the molecule from being cleared too quickly. Pfizer presented 28-week results from an ongoing midstage weight-loss trial at the American Diabetes Association’s annual conference on Saturday.
In that trial, Pfizer said berobenatide helped patients lose as much as 12.3% of their body weight on average. Pfizer also presented midstage data in people with Type 2 diabetes and said the drug helped patients control blood sugar.
Participants in the weight-loss study started at lower doses that increased over the first several weeks to help manage side effects. They first received weekly injections for 12 weeks, then switched to monthly shots. The trial is planned to continue for 64 weeks.
Buse said gastrointestinal side effects were comparable to, or no worse than, those seen with other GLP-1 medicines, and were more common when patients moved from weekly to monthly dosing. He said berobenatide appears to act on the GLP-1 receptor in a way intended to reduce side effects.
Amgen moves a monthly drug into late-stage testing
Amgen’s monthly candidate, MariTide, uses an antibody to stay in the body longer. Murielle Veniant-Ellison, who leads Amgen’s obesity research and development, said the drug binds to the GLP-1 receptor and also blocks the GIP receptor.
Dr. Daniela Hurtado Andrade, an endocrinologist at the Mayo Clinic in Jacksonville, Florida, said researchers still do not have a settled explanation for why both activating and blocking GIP can be linked to weight loss.
A midstage trial of nearly 600 adults published last year found that MariTide helped patients lose up to 20% of body weight on average after 52 weeks. Reported side effects were similar to other GLP-1 drugs, mainly gastrointestinal problems. Veniant-Ellison said patients might have continued losing weight beyond the 52-week period.
Amgen is also studying whether MariTide can be taken every other month or every three months, and whether it can treat obesity-related conditions including heart disease and sleep apnea.
Dr. Susan Spratt, an endocrinologist and senior medical director at Duke Health’s Population Health Management Office, said monthly shots could help patients who have trouble following a weekly schedule or prefer fewer doses. Spratt, who owns Amgen stock, said some patients may still do better with a weekly routine and she would likely start them there before switching if they tolerate treatment.
Taylor McDaniels, 25, of Pittsburgh, said she generally keeps up with her weekly compounded tirzepatide injection but has missed or delayed shots because of travel or illness. She said she would want to know whether a monthly option has different side effects and whether it controls food cravings as well and for as long as weekly drugs.
This story draws on original reporting from NBC News.