GLP-1 analog peptides, semaglutide, tirzepatide and retatrutide — their efficacy on MC4R deficient obesity and the limits of comparison
The human trials here don’t settle the MC4R-specific question. Their participants and comparisons matter more than a tidy ranking.
What we can say about MC4R deficient obesity
The clinical papers linked here don’t rank semaglutide, tirzepatide and retatrutide specifically for people with MC4R deficient obesity. That is a narrower question than how much weight changed in a general obesity trial.
The direct obesity comparison tests two of these medicines. The retatrutide trial compares the third with placebo. Joining those results doesn’t create a three-way trial or an MC4R-specific result.
The human trials discussed below don’t supply that three-way, MC4R-specific comparison. General obesity results can’t quietly fill the gap.
Tirzepatide has a direct comparison
Mounjaro and Zepbound both contain tirzepatide. It acts on two hormone receptors, GIP and GLP-1. Semaglutide acts on GLP-1; retatrutide adds glucagon. They aren’t simply three versions of the same medicine.
In the head-to-head obesity trial, tirzepatide led to a larger average drop in weight over the 72 weeks than semaglutide. Participants had obesity without type 2 diabetes. Tirzepatide’s maker funded the study, and participants knew which medicine they received.
That is useful evidence for that comparison. It doesn’t pick a medicine for every person or establish which one is best for every outcome.
The diabetes trial asks something else
The diabetes comparison also tested tirzepatide against semaglutide, this time in adults with type 2 diabetes. It belongs with a question about that population and the treatments tested.
We don’t use it as a second vote in a universal contest. Blood sugar, body weight and heart events are different outcomes. A trial answering one question doesn’t automatically answer the others.
Retatrutide can’t be added to the podium
The early retatrutide obesity trial used placebo, a dummy treatment, as its comparison. Neither semaglutide nor tirzepatide was tested against it there.
So the weight findings can be encouraging without establishing a winner across all three. Retatrutide is still investigational, without FDA approval. Sharing a receptor target with an approved medicine doesn’t change that.
A useful comparison keeps the cautions
Tirzepatide can cause digestive problems. The Zepbound (tirzepatide) label also describes gallbladder concerns and a thyroid-tumour warning based on rodent findings, with human relevance unknown. A better average result never replaces a safety review.
For people with MC4R deficient obesity, these sources leave the three-way comparison open. A general obesity result can’t settle that narrower question. Our individual essays keep each medicine’s findings and limits together. We’d rather stop at that boundary than let a tidy ranking say more than the papers do.