GLP-19 min read·April 2026

The Future of Incretins: Inside Eli Lilly's 2026 Pipeline (and What's Next)

Tirzepatide, retatrutide, orforglipron, and what's after them. Lilly's incretin pipeline in 2026 and the metabolic-tracking implications for serious users.

Quick Summary - Eli Lilly currently has the most aggressive incretin pipeline in the industry — five compounds in active development across the GLP / GIP / glucagon receptor space. - Approved today: tirzepatide (Mounjaro / Zepbound). - Phase 3 active: retatrutide (triple agonist), orforglipron (oral GLP-1). - Earlier-stage: combination therapies pairing GLP-class compounds with bimagrumab (myostatin antibody) for muscle preservation. - The strategic logic: cover every patient access tier. Injectable for max efficacy. Oral for scale and global reach. Combination for muscle quality concerns. Triple agonist for severe metabolic disease. - Informational reporting only — not medical advice.

Where The Industry Is, As Of April 2026

Step back and look at the GLP-class landscape:

•**Novo Nordisk** dominates the originator GLP space (semaglutide / Ozempic / Wegovy). They have CagriSema (cagrilintide + semaglutide combo) in Phase 3 and an oral semaglutide reformulation in development. Their next-gen amylin program is also active.

•**Eli Lilly** went from an underdog in this space to the apparent technical leader in five years. Tirzepatide is the highest-efficacy approved compound. Retatrutide is the highest-efficacy compound in Phase 3. Orforglipron is the most clinically advanced oral.

•**Amgen** has MariTide (the company's GIP antagonist + GLP-1 agonist combo, peptide-antibody conjugate) in Phase 3.

•**Pfizer, Roche, Boehringer Ingelheim, Structure Therapeutics** all have programs but are behind Lilly and Novo.

Within this landscape, Lilly's strategic position is the broadest pipeline by access tier — they're targeting different patient populations with different molecules, not just iterating on one mechanism.

The Lilly Incretin Pipeline (2026)

### Tirzepatide (approved)

•**Brand:** Mounjaro (T2D) / Zepbound (chronic weight management)

•**Mechanism:** Dual GLP-1 + GIP agonist

•**Status:** FDA-approved, broadly deployed

•**Note:** Remains the efficacy benchmark for the class

### Retatrutide (Phase 3 — TRIUMPH program)

•**Code:** LY-3437943

•**Mechanism:** Triple GLP-1 + GIP + glucagon agonist

•**Phase 2 result:** ~24% mean body weight reduction at 48 weeks at high dose

•**Status:** Phase 3 trials reading out across obesity, T2D, CV outcomes, OSA, knee OA

•**Note:** The "GLP-3" of community discussion. Heart rate signal warrants monitoring

### Orforglipron (Phase 3)

•**Code:** LY-3502970

•**Mechanism:** Small-molecule oral GLP-1 agonist (not a peptide)

•**Phase 3 result:** ~12-15% mean body weight reduction at 72 weeks at highest dose

•**Status:** Phase 3 read-out reported; regulatory submission timing 2026

•**Note:** First oral GLP that doesn't require special absorption enhancers or food restrictions

### Eloralintide (Phase 2)

•**Mechanism:** Long-acting amylin analog

•**Note:** Lilly's response to Novo's CagriSema — amylin-class can be paired with GLP-1 for additive metabolic effects, particularly on satiety and gastric emptying

### Bimagrumab + GLP combination (Phase 2)

•**Background:** Lilly acquired Versanis in 2023 for the bimagrumab (myostatin antibody) program

•**Mechanism:** Pairs muscle-preserving bimagrumab with GLP-class weight loss

•**Note:** Addresses one of the largest legitimate concerns about high-dose GLP therapy — lean mass loss alongside fat mass loss. Bimagrumab blocks myostatin signaling to preserve muscle during caloric deficit

Why The Pipeline Logic Makes Sense

If you sit at Lilly and ask "who wants weight loss therapy in 2030?", the answer is multiple distinct populations:

The maximum-effect cohort: People with severe obesity, metabolic syndrome, or comorbidities where 20%+ weight reduction matters clinically. These users are willing to inject weekly and tolerate side effects. Retatrutide is built for them.

The convenience cohort: People with moderate weight loss goals who don't want a weekly injection. Orforglipron's oral pill is built for them.

The muscle-quality cohort: Strength athletes, older adults at sarcopenia risk, anyone who wants to lose fat without losing as much lean mass. Bimagrumab combo is built for them.

The global access cohort: Markets without reliable cold chain or where injection delivery is impractical. Oral orforglipron addresses this.

This is a portfolio strategy. Lilly isn't betting on one molecule — they're betting on covering the entire incretin demand curve.

What's Coming After 2026 (Speculative)

Several frontier directions are publicly discussed in pipeline disclosures and conference presentations:

Quad agonists: A theoretical molecule activating GLP-1 + GIP + glucagon + a fourth target (most often discussed: amylin). The "GLP-4" framing in community discussion sometimes references this. Lilly hasn't disclosed a clinical-stage quad agonist publicly, but several preclinical programs in this space are known.

Body-composition-optimized combinations: Combining GLP-class with myostatin antibodies, amylin analogs, or activin receptor modulators to preserve lean mass during weight loss.

Tissue-specific GLP delivery: Targeted formulations to engage particular receptor populations (e.g., gut-specific or CNS-specific GLP-1 activation).

Oral peptide breakthroughs: New formulation chemistry to make injectable peptides orally available without the absorption-enhancer compromises of current oral semaglutide.

What This Means For Tracking

If you're an optimizer running any GLP-class compound today, the practical implication is:

1. Your biomarker watchlist doesn't change. HbA1c, ApoB, triglycerides, ALT, fasting glucose / insulin, weight, body composition. These markers tell the story whether you're on tirzepatide today, switch to retatrutide in 2027, or pick up orforglipron when it launches.

2. Trend continuity matters. If you're going to be in this class long-term — and many users will be — the value of consistent tracking compounds. A user who has 5 years of biomarker trends through compound switches has dramatically more useful data than someone who started fresh on each new drug.

3. Body composition matters more, not less. As the field moves toward muscle-preserving combinations, tracking lean mass alongside fat mass becomes table stakes. DEXA, BIA, or even consistent measurements at the same body sites — not just the scale.

4. Wearable recovery data becomes more useful. Retatrutide's heart rate signal, GLP-class effects on sleep architecture and HRV — all of this is more visible to someone tracking with a wearable than to someone relying only on quarterly labs.

How MyProtocolStack Handles The Class

The compound library covers tirzepatide, semaglutide, retatrutide, MK-677, HGH, and the broader peptide universe. The reconstitution calculator handles the standard vial sizes. StackAI reads your lab panels in context of which GLP-class compound you're running, your dose history, your recovery trends, and your stated goal — not just the numbers in isolation.

[Compound library](https://myprotocolstack.com/library) · [Calculators](https://myprotocolstack.com/calculators) · [Set up tracking](https://myprotocolstack.com/auth/login)

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Sources & references: Eli Lilly investor presentations and pipeline disclosures (2025-2026). Phase 3 read-outs from TRIUMPH (retatrutide) and ATTAIN-1 (orforglipron) programs. Novo Nordisk pipeline disclosures for industry comparison. Informational only — not medical advice. Discuss any pharmacologic decision with your prescribing physician.

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