Retatrutide vs Eloralintide: Weight Loss, Side Effects and Status

Retatrutide has the bigger published weight loss in the eloralintide vs retatrutide comparison, but the two drugs have never been tested against each other. At 48 weeks, adults on eloralintide 9 mg lost an average of 20.1% of their body weight, and adults on retatrutide 12 mg lost 24.2%, both in Phase 2 trials and both on Lilly's efficacy estimand. Retatrutide also has an 80-week Phase 3 result of 28.3%. Eloralintide's Phase 3 trials only started in 2026.

The drugs are built differently. Eloralintide activates one receptor, the one for the hormone amylin. Retatrutide activates three, for GIP, GLP-1 and glucagon. Here they are side by side.

Sources for each cell are in the sections below. The rest of this page explains why you can't simply subtract one column from the other.

Everything here is as of October 31, 2026. Eloralintide is moving fast, so the trial dates in particular are worth rechecking.

How the two drugs work

Amylin is a hormone your body releases after you eat, and it helps you feel full. Lilly describes eloralintide as a selective amylin receptor agonist designed to preferentially activate the amylin 1 receptor, and says the effect on eating is likely mediated by satiety (Lilly's eloralintide FAQ and release).

Retatrutide copies three gut hormones at once. In Lilly's description it activates the GIP, GLP-1 and glucagon receptors. The GLP-3 page covers the mechanism in more depth.

Our read: Lilly is pitching eloralintide two ways at once. In its Nov 6, 2025 release, a Lilly executive says it "could serve as an alternative to incretin therapies" and could be "a complementary option" for people who need more efficacy, and its trial list covers both plans.

Eloralintide vs retatrutide weight loss, trial by trial

Eloralintide's one finished obesity trial was a 48-week Phase 2 in 263 US adults without type 2 diabetes (Billings et al., The Lancet, November 2025). At 48 weeks, on the efficacy estimand, people lost an average of 9.5% on 1 mg, 12.4% on 3 mg, 17.6% on 6 mg and 20.1% on 9 mg, against 0.4% on placebo (Lilly). Lilly notes these results aren't adjusted for multiplicity. The Lancet abstract rounds the 9 mg result to 20%. We didn't find an eloralintide figure for the treatment-regimen estimand, which counts everyone randomized, in the sources we could open.

Retatrutide's matching length comes from its own Phase 2: 24.2% at 48 weeks on 12 mg in 338 adults, again on the efficacy estimand (Lilly's release on the NEJM paper). That is the closest like-for-like pair available, and it still mixes different doses, populations and sites.

The longer result is TRIUMPH-1. Over 80 weeks, 12 mg averaged 28.3% on the efficacy estimand, and 25.0% on the treatment-regimen estimand that the NEJM paper leads with, against 2.2% and 3.9% on placebo.

Type 2 diabetes tells the same story at lower levels for both drugs. In Lilly's 48-week Phase 2b, eloralintide alone gave 8.2% (3 mg), 12.3% (6 mg) and 11.1% (9 mg), against 3.0% on placebo, in 367 adults with type 2 diabetes. Retatrutide 12 mg lost 20.9% at 80 weeks in TRANSCEND-T2D-2 (efficacy estimand, Lilly topline). Again, different length, different trial.

Side effects and stopping rates

Nausea is the headline for both, and the eloralintide numbers are messier than a dose-response line. In the Lancet Phase 2, nausea was 11% on 1 mg, 13% on 3 mg, 64% on 6 mg, 33% on 9 mg, 54% on the 6 to 9 mg schedule and 25% on the 3 to 9 mg schedule, with 14% on placebo. The 6 mg arm had only 28 people, so a single arm's rate can swing a lot. Fatigue was the other common event: 43% on 9 mg and 46% on 6 to 9 mg, against 12% on placebo. Lilly says the events were mild to moderate and fell with slower escalation.

In TRIUMPH-1, nausea was 28.6%, 38.4% and 42.4% on 4, 9 and 12 mg against 14.8% on placebo, so about 4 in 10 people on the top dose. Vomiting hit 25.3% on 12 mg against 4.8%, and diarrhea 32.0% against 13.5%. Dysesthesia, a burning or oversensitive skin feeling, reached 12.5% against 0.9% (Lilly's release).

Stopping rates are harder to compare. In TRIUMPH-1, 11.3% on 12 mg stopped treatment because of side effects, against 4.9% on placebo. For eloralintide, the monotherapy trial's participant-flow table on ClinicalTrials.gov lists study withdrawals for adverse events of 1 of 54 on 9 mg and 2 of 52 on the 3 to 9 mg schedule, against 2 of 53 on placebo. That isn't the same measure as Lilly's treatment discontinuation rate, and Lilly's release didn't give that rate for the Phase 2. In the diabetes Phase 2b, Lilly reported 0% to 10.8% stopping for side effects on eloralintide alone and 16.7% on placebo.

Eloralintide's tolerability pitch is plausible but unproven at Phase 3 size: the biggest eloralintide arm in either Phase 2 had 54 people.

What the numbers can't tell you

Every row in the table above is a cross-trial comparison. The trials differ in four ways that move the answer.

First, length and dose steps. Eloralintide's best arm ran 48 weeks and retatrutide's ran to 80. Second, the people: eloralintide's Phase 2 was 78% women, with an average weight of 109.1 kg, while TRIUMPH-1 enrolled 2,339 adults with a baseline weight of 112.7 kg. Third, size: 263 people against thousands. Fourth, the estimand. Lilly's headline numbers for both drugs assume everyone stayed on treatment, and for retatrutide the gap to the treatment-regimen figure is 3.3 points (28.3% vs 25.0%).

Without a head-to-head trial, you can't say how much of the 4-point gap at 48 weeks (24.2 minus 20.1, our subtraction) is the drug. TRIUMPH-5, retatrutide against tirzepatide, is the head-to-head still to report; retatrutide vs tirzepatide covers where it stands.

Where each drug is in development

Eloralintide finished Phase 1 and Phase 2. Lilly's September 2026 FAQ says it is now running Phase 3 trials of eloralintide for obesity and related conditions, such as obstructive sleep apnea and knee osteoarthritis pain. ClinicalTrials.gov lists ENLIGHTEN-1 (1,980 people without type 2 diabetes; primary endpoint weight change at week 64; primary completion estimated March 2028), ENLIGHTEN-2 (1,035 people with type 2 diabetes; estimated January 2028) and ENLIGHTEN-3 in sleep apnea (800 people; estimated March 2028). Treat those dates as registry estimates. The registry doesn't publish the Phase 3 dose levels.

Retatrutide has six Phase 3 readouts, from TRIUMPH-4 in December 2025 to TRANSCEND-T2D-2 on October 28, 2026. Lilly last said, on September 29, 2026, that it plans to submit retatrutide to the FDA in the first quarter of 2027 as a Biologics License Application (BLA). On October 2, 2026, the FDA decided that retatrutide is a drug, not a biological product, so an application would need to be filed under section 505 of the Federal Food, Drug, and Cosmetic Act. Lilly's appeal on that question is pending in the Seventh Circuit, and we found no ruling as of October 31, 2026. The release date page tracks the timeline.

Our read: retatrutide is ahead of eloralintide on the registered dates, since Lilly plans a filing in 2027 and eloralintide's Phase 3 trials don't finish before 2028. Neither has a price or a launch date.

Dosing and who gets them

Both are weekly injections. Retatrutide's Phase 3 trials started everyone at 2 mg and stepped up every 4 weeks to 4, 9 or 12 mg targets; see the dose levels page for the steps. Eloralintide's Phase 2 tested 1, 3, 6 and 9 mg plus two step-up schedules, and Lilly says slower escalation lowered side effects. The Phase 3 doses and schedule haven't been published.

Neither is a prescription product anywhere. Anything sold online under either name isn't Lilly's, and if you're looking at a retatrutide for sale listing, that page covers batch testing, labels and regulator warnings. For eloralintide, the only legitimate route is a clinical trial, found through the ClinicalTrials.gov records above.

Could you combine eloralintide and retatrutide?

No published trial has done it. The ClinicalTrials.gov search for eloralintide (21 records as of October 31, 2026) turned up no trial that includes retatrutide.

What Lilly has studied is eloralintide plus tirzepatide, called EloraTZP. In a 48-week Phase 2b, 367 adults with type 2 diabetes got eloralintide, tirzepatide or both as separate injections. The top combination, eloralintide 9 mg plus tirzepatide 15 mg, averaged 23.3% weight loss and a 2.9-point A1C drop, against 14.8% and 2.4 for tirzepatide 15 mg alone (efficacy estimand). Stopping for side effects ran 10.8% to 27.0% across the combinations, against 2.9% on tirzepatide alone, and stomach side effects were more frequent in the combination arms. Lilly says it plans Phase 3 trials of a co-formulation by the end of 2026, and the two AMPLIFY trials are registered but not yet recruiting.

That gives a fair hint at what adding amylin does on top of an incretin drug, and a warning that it costs tolerability. It says nothing direct about adding it to retatrutide, which already works on the GLP-1 receptor. If this matters to you, bring it to your doctor as a question for a future trial rather than something to try.

Who this comparison helps

If you're weighing the two as future options, the practical questions to take to a doctor are whether weight loss size or tolerability matters more to you, whether you have type 2 diabetes (where both drugs show smaller weight results than in people without it), and whether you'd rather wait for the amylin drug's Phase 3 data or for the first approved incretin option. For the wider pipeline, see new weight loss drugs and all retatrutide alternatives.

One last number to keep: ENLIGHTEN-1's primary endpoint is measured at week 64, not week 48, so even the first Phase 3 readout will not line up exactly with either Phase 2 figure used here.