Eli Lilly's eloralintide moves into Phase 3 alone and with tirzepatide

Eli Lilly's experimental obesity drug eloralintide has moved into Phase 3 testing, where it is being studied both by itself and in combination with tirzepatide, the molecule sold as Mounjaro and Zepbound ^[1]. Eloralintide is a selective amylin receptor agonist, a molecule designed to mimic amylin, a hormone the body releases along with insulin when you eat ^[2].

The step up to late-stage testing follows Phase 2 results that set a new mark for the class. In a 48-week trial of 263 adults, weight loss ranged from about 9 percent at the 1 mg dose up to 20 percent at the 9 mg dose, compared with 0.4 percent on placebo ^[2]. Side effects rose with dose: nausea was reported in 11, 13, 64 and 33 percent of participants across the dosing arms, versus 14 percent on placebo, and fatigue reached as high as 46 percent ^[2].

Those tolerability numbers are central to how the field is watching eloralintide. Amylin drugs used alone have generally topped out around 10 to 12 percent weight loss ^[2]. Eloralintide broke that ceiling, but its 64 percent nausea rate in one arm sits far above what other amylin developers have reported ^[2]. Zealand Pharma's petrelintide, developed with Roche, produced up to 10.7 percent weight loss versus 1.7 percent on placebo in a 493-person Phase 2 trial, with vomiting reported in 3 percent of participants on the drug versus 6.2 percent on placebo ^[2]. Direct comparisons between trials in this class are unreliable because the studies used different lengths, populations and methods ^[2].

Combining an amylin drug with an incretin such as tirzepatide is the approach most companies are now pursuing, on the idea that the two work through different receptors and different brain circuits ^[2]. The first direct test of that idea did not confirm it: in the REDEFINE-4 trial, CagriSema, Novo Nordisk's combination of cagrilintide and semaglutide, failed to match tirzepatide 15 mg over 84 weeks ^[2]. That result involved a different amylin analog paired with a different partner, so it does not settle the question for eloralintide ^[2].

Why it matters for patients

No amylin-based drug is approved for weight management in the United States, and eloralintide is not available to patients outside clinical trials ^[1][2]. The FDA is reviewing CagriSema, with a decision expected in late 2026 ^[2]. People taking semaglutide (Ozempic, Wegovy, Rybelsus) or tirzepatide (Mounjaro, Zepbound) today would not see any change in their own treatment from this Phase 3 expansion.

The practical question the class is trying to answer is not only how much weight a drug can take off, but whether people can stay on it. A drug that produces somewhat less weight loss but far less nausea and vomiting could matter for the many patients who stop GLP-1 treatment within the first year because of gastrointestinal side effects ^[2]. Whether that trade-off holds up outside a supervised trial has not been tested in Phase 3 ^[2].

A related claim, that amylin drugs preserve lean muscle better than GLP-1s, remains unproven. At the ADA 2026 meeting, researcher Thomas Lutz said the preclinical data on this are not conclusive, and one rat study found that weight loss from cagrilintide included both fat and lean mass ^[2]. Whether eloralintide would be covered by insurance, and at what price, has not been disclosed.

What happens next

The Phase 3 trials for eloralintide, ENLIGHTEN-1 and ENLIGHTEN-6, both began in February 2026 and were still recruiting as of September, with primary results not expected before 2028 ^[1]. Zealand's petrelintide Phase 3 was endorsed in April 2026 and starts in the second half of this year, while ZUPREME-2, testing petrelintide in obesity plus type 2 diabetes, reports later this year; a Phase 2 combining petrelintide with Roche's CT-388 is planned for later in 2026 ^[2]. Those timelines overlap with Lilly's, so several amylin readouts could land close together ^[1].