๐Ÿš€ Phase 3 โญ Most Anticipated Eli Lilly ยท Weekly injection

Retatrutide

LY3437943 ยท Triple Agonist ยท Est. FDA Approval: 2027

Retatrutide targets three hunger hormones at once where every approved drug hits only one or two. Phase 2 produced 24% body weight loss, the highest number ever recorded in a weight loss trial. Phase 3 is underway now.

Phase 2 showed 24% body weight loss, the highest ever recorded in a weight loss trial. More powerful than anything currently approved. Phase 3 trials are now underway.

๐Ÿ’‰
Phase 2 Loss
24%
Est. FDA
2027
At a Glance

Retatrutide by the Numbers

Phase 2 Weight Loss
24.2%
Highest ever in a weight loss trial
Form & Schedule
Weekly Injection
Subcutaneous pen, once a week
Mechanism
Triple Agonist
GLP-1, GIP & Glucagon receptors
Phase 2 Lbs Lost (avg.)
58 lbs
For a 240 lb person over 48 weeks
Manufacturer
Eli Lilly
Same company as Zepbound
FDA Status
Phase 3
Est. approval 2027
Plain English

What Exactly Is Retatrutide?

A weekly injection targeting three hormones. More powerful than anything currently approved. Think of it as the next step beyond Zepbound and Wegovy, targeting one more hormone, and producing meaningfully stronger results.

Every approved GLP-1 drug today, Wegovy, Zepbound, Ozempic, works by targeting one or two hormone receptors in your gut and brain to reduce appetite. Retatrutide targets three: GLP-1, GIP, and glucagon.

That third receptor (glucagon) is what makes it different. While GLP-1 and GIP reduce how much you want to eat, glucagon receptor activation directly increases how many calories your body burns, even at rest. The result is an attack on obesity from both sides at once: less calories in, more calories out.

Zepbound (tirzepatide) hits GLP-1 and GIP and already outperforms Wegovy. Retatrutide adds that third target, which may explain why Phase 2 results surpassed everything before it.

The Triple Mechanism

Three Hormones, One Drug

Three receptors targeted. Attacks hunger and metabolism simultaneously. Each receptor does something different. Together, they produce results no single-target drug has matched.

๐Ÿง 
GLP-1 Receptor
Signals fullness to your brain and slows digestion. The same target as Wegovy and Ozempic. Reduces appetite and food cravings, many describe the "food noise" in their head going quiet.
โšก
GIP Receptor
Enhances the GLP-1 effect and improves how your body handles fat and glucose. Also the target added by Zepbound. Contributes to the stronger results seen in dual and triple agonists.
๐Ÿ”ฅ
Glucagon Receptor
The new addition. Glucagon activation increases energy expenditure, your body burns more calories throughout the day, even without extra exercise. This "calories out" effect is what sets retatrutide apart from its predecessors.
1

You Take a Weekly Shot

A small subcutaneous injection once a week, similar to Zepbound or Wegovy. The dose is gradually increased over several months to reduce side effects.

2

Appetite Drops Significantly

GLP-1 and GIP receptor activation reduces hunger hormones and slows gastric emptying. Most trial participants reported dramatically less interest in food within the first few weeks.

3

Metabolism Gets a Boost

The glucagon component increases your resting metabolic rate. Your body burns more energy throughout the day, accelerating fat loss even when you're not active.

Phase 2 Clinical Trial Data

What the Trials Showed

Phase 2 (TRIUMPH-1): 338 adults, 48 weeks, published June 2023 in NEJM. Retatrutide's Phase 2 results were published in June 2023 in the New England Journal of Medicine (NEJM), one of the most prestigious medical journals in the world. The TRIUMPH-1 trial enrolled 338 adults with obesity, ran 48 weeks, and included a placebo group for comparison.

24.2%
Average Body Weight Lost
Highest dose (12mg) at 48 weeks
17.5%
Lost at Medium Dose (8mg)
Still outperforms many approved drugs
2.1%
Placebo Weight Loss
Makes the drug effect even clearer
๐Ÿ“Š Why 24% Is a Big Deal

To put this in context: Wegovy (semaglutide), currently the best-selling weight loss drug in the world, averages around 15% weight loss. Zepbound (tirzepatide), the most effective approved drug, averages around 20-21%. Retatrutide's Phase 2 result of 24.2% is the highest number ever recorded in a weight loss drug trial. If Phase 3 results match Phase 2, retatrutide could become the new gold standard in obesity treatment.

โ„น๏ธ Phase 2 trials are designed to test effectiveness and find the right dose, they're smaller than Phase 3. Results may differ in the larger Phase 3 trials. All participants also followed a reduced-calorie diet and exercise program.
Development Timeline

Where Things Stand

Phase 3 is underway now. FDA decision expected 2027. Every drug has to pass through three phases of testing before the FDA will approve it. Here's exactly where retatrutide sits today.

2020-2022
โœ“ Done
Phase 1, Is it safe?
A small group of volunteers tested the drug first. It was confirmed safe and well-tolerated at the right dose.
2022-2023
โœ“ Done
Phase 2, Does it work?
338 people tested it for a year. The 24.2% weight loss result made global headlines, the highest number ever recorded in a weight loss drug trial.
2024, Now
โ— Happening Now
Phase 3 testing
The final step before FDA review. Thousands of people across multiple countries are now taking part. Results expected in 2026.
Est. Late 2026
Up Next
Apply to the FDA
Eli Lilly sends all the trial data to the FDA and formally requests approval.
Est. 2027
Up Next
FDA Decision
The FDA reviews the data and decides. If approved, doctors can start prescribing it. A 2027 decision is considered realistic.
๐Ÿ’ก Want to try it before approval?

Phase 3 trials are still enrolling. You'd get the drug at no cost and have close medical supervision throughout.

Search Open Trials โ†’
Phase 3 by the numbers
People enrolled 3,000+
Trial length 72 weeks
Est. results 2026

"Phase 2 data is phase 2 data and I try not to get ahead of it. But the retatrutide numbers were in a range I associate with surgery, not medication. That's enough for me to keep a close eye on where this goes."

Dr. Quoc N. Dang, DO

Dr. Quoc N. Dang, DO

Bariatric Surgeon ยท Obesity Medicine

Who Should Watch This

Is Retatrutide Right for You?

Not available yet. But here's who it's most likely to help when it is. Retatrutide isn't approved yet, so you can't get a prescription today. But based on Phase 2 data and Eli Lilly's expected indication, here's who it looks best suited for, and who should think carefully.

โœ… Likely Good Candidates

  • Adults with BMI 30+ looking for the most powerful available option
  • People who tried Wegovy or Zepbound but didn't get the results they hoped for
  • People with Type 2 diabetes and obesity (multiple trials ongoing)
  • Adults with obesity-related cardiovascular disease
  • Anyone comfortable with a weekly injection and willing to wait for approval

โš ๏ธ Things to Consider

  • Not yet FDA-approved, availability is at least 1-2 years away
  • Glucagon agonism may affect blood sugar differently than current GLP-1s
  • Side effect profile is similar to Zepbound but not yet fully characterized at Phase 3 scale
  • History of thyroid cancer or pancreatitis warrants careful discussion with your doctor
  • Long-term data (beyond 48 weeks) is still being collected

โš•๏ธ Always consult your doctor before starting or changing any weight loss treatment.

Side by Side

How Retatrutide Compares

Retatrutide vs approved drugs and other pipeline meds. Stacking retatrutide against what's currently available and what's coming.

Drug Weight Loss Mechanism Form Status
๐Ÿ’‰Retatrutide You're here 24% (Ph2) Triple Agonist Weekly injection Phase 3
๐Ÿ’‰Zepbound 21% Dual Agonist (GLP-1, GIP) Weekly injection โœ“ Approved
๐Ÿ’‰CagriSema 25% (Ph3) GLP-1 + Amylin Weekly injection Phase 3
๐Ÿ’‰Wegovy 15% GLP-1 Agonist Weekly injection โœ“ Approved
๐Ÿ’ŠFoundayo 12.4% GLP-1 Agonist Daily pill โœ“ Approved

Phase 2 and Phase 3 numbers are from clinical trials, not direct drug-to-drug comparisons. Interpret any cross-trial numbers carefully.

Common Questions

Retatrutide FAQ

Retatrutide is currently in Phase 3 clinical trials. Eli Lilly is expected to file a New Drug Application (NDA) with the FDA in late 2026. If approved on schedule, it could be available by prescription in 2027. These timelines can shift depending on trial results and the FDA review process.
Zepbound (tirzepatide) targets two receptors: GLP-1 and GIP. Retatrutide adds a third: glucagon. The glucagon receptor activation increases energy expenditure, meaning your body burns more calories even at rest. This is likely why Phase 2 results exceeded Zepbound's Phase 3 outcomes. Both are weekly injections made by Eli Lilly.
Phase 2 trials are smaller and optimized to find the best dose, they sometimes show slightly stronger results than Phase 3 trials, which are larger and more broadly representative. Even so, retatrutide's Phase 2 data was published in the New England Journal of Medicine and considered extremely strong. Most experts expect Phase 3 results to remain strong, though exact numbers may differ.
In Phase 2 trials, the most common side effects were nausea, vomiting, diarrhea, and decreased appetite, very similar to other GLP-1 medications. These were generally mild to moderate and improved over time. The dose escalation schedule is specifically designed to minimize early gastrointestinal side effects. More complete safety data will come from Phase 3.
Not as an approved prescription medication. However, you may be able to participate in an ongoing Phase 3 clinical trial, which means you'd receive the drug for free and under close medical supervision. Search "retatrutide" at ClinicalTrials.gov to find trials near you. Outside of trials, there's currently no legal way to access retatrutide.
Very likely, yes. Eli Lilly is running dedicated Phase 3 trials in people with Type 2 diabetes. GLP-1 agonists consistently improve blood sugar control alongside weight loss, and the dual GLP-1/GIP mechanism in Zepbound already showed strong glucose-lowering effects. Adding glucagon agonism introduces some complexity for diabetes management (glucagon typically raises blood sugar), but Eli Lilly's formulation appears calibrated to produce a net benefit. Full results are pending.
Both are leading weight loss drugs in Phase 3 with results exceeding anything currently approved. CagriSema (Novo Nordisk's combination of semaglutide and cagrilintide) showed 25% weight loss in Phase 3 data released in late 2024. The drugs work through different mechanisms, retatrutide's triple agonism vs. CagriSema's GLP-1 plus amylin analog approach. It's possible both get approved and doctors will choose based on individual patient profiles.
Dr. Quoc N. Dang, DO
Medically Reviewed by
Dr. Quoc N. Dang, DO
Bariatric Surgeon
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