Two compounds, searched together

Retatrutide's phase 2 obesity trial reported a larger average weight loss than tirzepatide's phase 3 approval trial, which makes it tempting to read this as a contest retatrutide already won. It isn't one, because it is not a head-to-head comparison. A trial putting the two drugs in the same study is registered — NCT06662383, listed enrollment 800, listed completion December 2026 — but as of August 2026 a PubMed search for retatrutide returns no published trial that randomized participants to one drug or the other, so every figure below comes from a separate trial on a different population for a different duration at a very different scale. Retatrutide has also now reported a phase 3 result of its own, in type 2 diabetes, and it is not an approved medicine of any kind, while tirzepatide is FDA-approved and available by prescription as Zepbound and Mounjaro. This page lays out what each trial actually reported, not what stacking the headline percentages next to each other would imply.

Semaglutide and tirzepatide are the one pair on this site that has genuinely been randomized against each other. SURMOUNT-5 put 751 adults with obesity and without diabetes on the maximum tolerated dose of one drug or the other for 72 weeks, and tirzepatide came out ahead: a 20.2% average weight reduction against 13.7%. A second trial, SURPASS-2, compared them in type 2 diabetes and also favored tirzepatide, on blood sugar. That is the whole of the direct evidence, and it is narrower than the conclusion usually drawn from it — both trials were open-label, and both capped semaglutide below the highest dose its label now describes. Every other figure on this page is not a head-to-head result at all: it comes from a separate trial with its own placebo arm, its own population and its own duration. Here is what each trial actually reported.

Sermorelin and tesamorelin are the same idea twice. Both are growth hormone-releasing hormone in synthetic form, both work one step upstream of injected growth hormone by asking the pituitary to release its own, and both are sold in the same corner of the market. Their evidence records are nothing alike. Tesamorelin was tested in two multicenter phase 3 trials, holds an FDA approval that is current today, and has a published answer to what happens when you stop taking it. Sermorelin's randomized record runs to 19 trials, the most recent of them published in 2005, and not one measured body fat, muscle or sleep in a healthy adult; its own approval, as Geref, is listed as discontinued. The two have never been tested against each other, so this page does not stage a contest. It sets the two records side by side and says which questions each one can answer.