Retatrutide's top dose cut body weight by a quarter over 80 weeks in a 2,339-adult trial

Subtract the placebo arm and the 12 mg dose is worth 21.1 percentage points of body weight over 80 weeks ^[1]. In a blinded trial of 2,339 adults, that is a large effect ^{[1] [2]}. The dose curve flattens near the top. Going from 4 mg to 9 mg added 6.1 points of average loss. Going from 9 mg to 12 mg added 1.3 ^[2]. ScienceAlert reported that side effects came with the improvements ^[16].

The 25% is the more conservative of two estimates. It counts people who stopped treatment or started prohibited weight-management therapies ^[9]. A second analysis estimated the result if everyone had kept taking the drug as intended. It put the full 12 mg group at 28.3% at 80 weeks ^[12], 3.3 points higher ^[6]. Both figures are averages, and individual results varied ^[9].

The two-year figures need more care. The first eligible participants to finish 80 weeks went into a 24-week extension, 532 people in all ^[10]. That is about 23% of those randomized ^[3]. In the original 12 mg group, now on a maximum tolerated dose of 9 or 12 mg, average loss reached 29.9% at 104 weeks ^[11], or 30.3% under the as-intended analysis ^[12]. That is 4.9 points above the full group's 80-week figure ^[8], but the two numbers describe different groups of people. Participants on placebo switched to retatrutide during the extension ^[13]. The thing this doesn't tell you is how much of those extra points comes from 24 more weeks on the drug and how much comes from who reached the extension. Without a two-year placebo arm, the design cannot separate the two ^[13].

The knee and sleep results come from subgroups. Among 574 participants with knee osteoarthritis, pain on a 0-10 scale fell 4.1 points on 12 mg and 2.5 points on placebo ^[14]. After subtracting placebo, the drug's share is 1.6 points ^[4]. The 243 participants with obstructive sleep apnea were about a tenth of enrollment ^[7]. At the top dose, their episodes of stopped or shallow breathing fell by 32.1 an hour, against 9.6 on placebo ^[15]. That is a gap of 22.5 events an hour ^[5].

The drug works by activating three hormone receptors at once: GLP-1, GIP and glucagon ^[4]. In obese mice, that combination lowered food intake and raised energy expenditure ^[5]. This trial tracked clinical outcomes and did not measure what each pathway contributed ^[6]. I'd treat the energy-expenditure half of the rationale as a mouse finding until a human study measures it.

ScienceAlert's headline calls retatrutide an Ozempic rival ^[17]. The trial randomized people only to retatrutide or placebo ^[2]. Any ranking against Ozempic would have to come from setting separate trials side by side, each with its own population and analysis. In the earlier phase 2 trial, the top dose produced 24.2% loss at 48 weeks. The phase 3 trial followed the effect for longer in a larger group ^{[7] [3]}. Retatrutide is still experimental ^[18].