The number out of Milan last week is genuinely striking. Participants receiving the highest-dose combination of eloralintide 9 mg and tirzepatide 15 mg lost an average of 54.1 pounds, or 23.3% of body weight, over 48 weeks, with A1C declining 2.9%. That is among the strongest Phase 2 obesity readouts disclosed to date. The result appears to be in the same ballpark as Lilly’s own triple-agonist candidate retatrutide, which has reported up to about 24% weight loss at 48 weeks in a separate Phase 2 study, though no head-to-head trial has been run.
But the figure that deserves more of investors’ attention was buried further down the release.
Gastrointestinal adverse events were most common and clustered during dose escalation. Discontinuation for adverse events ran 10.8% to 27.0% with EloraTZP, versus 2.9% with tirzepatide alone. At the highest dose combination, the one producing 23.3% weight loss, the treatment discontinuation rate was 27%, mainly due to gastrointestinal side effects. That is not a minor footnote. In an era when real-world adherence is already the central problem with GLP-1 medicines, starting from a Phase 2 discontinuation rate nearly ten times that of tirzepatide alone is a significant structural challenge heading into Phase 3.
Why Adherence Shapes the Franchise More Than Efficacy
The obesity drug market is not won in clinical trials. It is won in the pharmacy refill cycle. In pivotal programs for semaglutide and tirzepatide, discontinuation due to adverse events has often landed in the high single digits, depending on the trial and dose. But those rates have not been replicated in real-world settings. Large real-world analyses have found that roughly half of adults who began taking semaglutide for weight management discontinued within about a year in some insured cohorts. The problem is systemic, not drug-specific.
EloraTZP enters this environment having already shown tolerability pressure in a controlled clinical setting. Some analyst notes have argued that millions of patients have cycled through GLP-1s, stopping for a mix of efficacy shortfalls, tolerability, access, or other factors. Lilly’s pitch is that the amylin pathway offers those patients an alternative. That story holds only if EloraTZP can keep patients on it long enough to deliver meaningful weight loss.
There is a constructive case here. The high discontinuation rate was concentrated during dose escalation, raising the possibility that Lilly could reduce discontinuations through an optimized titration schedule planned for Phase 3. Lilly has said it will initiate Phase 3 trials in the fourth quarter of 2026, and it has also said it plans to advance a co-formulation product into Phase 3. A single injection replacing two separate shots should, in theory, reduce the burden that likely amplifies early GI events.
What Novo and the Field Now Have to Answer
Novo Nordisk is pursuing a parallel approach with cagrilintide, its experimental amylin-based drug. CagriSema, combining cagrilintide and semaglutide, has posted Phase 3 results that include 22.7% weight loss under an efficacy estimand, and Novo has said it has submitted an application to the FDA with the agency expected to review it in 2026. The competitive clock is ticking for both companies, but the shared challenge is not achieving peak efficacy in trials. It is demonstrating that the tolerability profile in real patients will not erode those trial-level results.
Viking Therapeutics (VKTX), Amgen (AMGN), AbbVie (ABBV), and Boehringer Ingelheim are each advancing next-generation obesity candidates, and all of them will face the same question Phase 2b has now raised plainly for Lilly: a drug that produces extraordinary weight loss in completers but loses a quarter of patients to side effects during escalation is not yet an extraordinary franchise. It is a promising molecule that still needs to prove it can be taken.
The 23.3% number is real, it matters, and it extends Lilly’s lead on the science. Long-term investors should watch the Phase 3 titration protocol data with equal attention. That is where the obesity franchise is actually built.
