Retatrutide 2026 Phase 3 Roadmap: TRIUMPH & TRANSCEND Programs

🚀 Overview: Two Major Trial Programs

Eli Lilly is running 8 Phase 3 trials for retatrutide in 2026 across two programs:

TRANSCEND Program — Type 2 Diabetes (3 trials)
TRIUMPH Program — Obesity & Related Conditions (5 trials)

With today's TRANSCEND-T2D-1 success (March 19, 2026), retatrutide is on track for FDA submission in late 2026.

📊 TRANSCEND Program (Diabetes)

TRANSCEND-T2D-1 ✅ SUCCESS (March 19, 2026)

Status: Complete
Results:

2% A1C reduction
16.8% weight loss (36.6 lbs)
Only 5% discontinued due to side effects

TRANSCEND-T2D-2 (Expected Q2 2026)

What it tests: Retatrutide + background diabetes therapy (metformin, etc.)
Why it matters: Most diabetes patients are already on medication
Expected results:

2-2.5% A1C reduction (better than T2D-1)
12-18% weight loss
Drug interaction safety data

TRANSCEND-T2D-3 (Expected Q2-Q3 2026)

What it tests: Cardiovascular safety in high-risk diabetes patients
Why it matters: Required by FDA, enables CV indication label
Expected results:

Non-inferiority for CV events (required)
Possible superiority (reduced heart attacks/strokes)
Similar A1C/weight loss to other trials

🏋️ TRIUMPH Program (Obesity)

TRIUMPH-1 (Expected Q3 2026) 🌟 FLAGSHIP

What it tests: Obesity without diabetes (primary weight loss trial)
Why it matters: Determines FDA obesity approval and label claims
Expected results (72 weeks):

24-28% weight loss (highest dose)
vs. Zepbound: 21% at 72 weeks
vs. Wegovy: 15% at 68 weeks

TRIUMPH-2 (Expected Q3-Q4 2026)

What it tests: Obesity with comorbidities (sleep apnea, hypertension, PCOS)
Why it matters: Drives insurance coverage decisions
Expected results:

Similar weight loss to TRIUMPH-1
40-60% sleep apnea resolution
5-10 mmHg blood pressure reduction
PCOS symptom improvement

TRIUMPH-3 (Expected Q4 2026)

What it tests: Weight loss maintenance (withdrawal study)
Why it matters: Proves long-term treatment necessity
Design:

Patients lose weight on retatrutide
Then continue treatment OR switch to placebo
Measure weight regain without treatment

TRIUMPH-5 (Expected Q4 2026)

What it tests: 4mg maintenance dose (lower dose option)
Why it matters: Lower cost, fewer side effects, better tolerability
Expected results:

12-15% weight loss (lower than 8-12mg doses)
1.5-1.8% A1C reduction
Significantly reduced side effects

TRIUMPH-6 (Expected Q4 2026)

What it tests: MASH (metabolic liver disease)
Why it matters: Huge unmet need (25% of US adults have fatty liver)
Expected results (based on Phase 2):

70-80% liver fat reduction
40-60% MASH resolution
1-2 stage fibrosis improvement

📅 2026 Trial Calendar

Quarter	Expected Readouts
Q1 2026	✅ TRANSCEND-T2D-1 (March 19)
Q2 2026	TRANSCEND-T2D-2, TRANSCEND-T2D-3 (interim)
Q3 2026	TRIUMPH-1 (flagship), TRIUMPH-2
Q4 2026	TRIUMPH-3, TRIUMPH-5, TRIUMPH-6, FDA submission

🎯 FDA Submission Strategy

Multiple Indications

Lilly will likely file for 3 simultaneous indications:

Type 2 Diabetes — TRANSCEND data (3 trials)
Chronic Weight Management (Obesity) — TRIUMPH data (4 trials)
MASH — TRIUMPH-6 data (if successful)

Priority Review Potential

Retatrutide may qualify for priority review (6 months vs 10 months) because:

Superior efficacy vs existing options
Addresses unmet medical need (MASH)
Breakthrough designation in Phase 2

❓ FAQs

What happens if TRIUMPH-1 shows less than expected weight loss?

Unlikely given:

TRIUMPH-4 showed 24-28% (osteoarthritis patients)
Today's diabetes trial showed 16.8% (harder to lose weight with diabetes)
Phase 2 showed 24% at 48 weeks

Even if results are 20-22%, that still beats Zepbound (21%).

Which trial result matters most?

TRIUMPH-1 (Q3 2026) — the flagship obesity trial. This determines:

FDA obesity approval
Label claims for weight loss %
Competitive positioning vs Zepbound/Wegovy
Insurance coverage breadth

Can Lilly file for approval before all trials complete?

Theoretically yes with TRANSCEND + partial TRIUMPH data, but Lilly will likely wait for all 8 trials to maximize label claims and indications.

✅ Bottom Line: Path to Approval

The roadmap is clear:

✅ March 2026: TRANSCEND-T2D-1 success (done)
⏳ Q2-Q3 2026: Remaining TRANSCEND trials
⏳ Q3 2026: TRIUMPH-1 flagship obesity trial
⏳ Q4 2026: Final TRIUMPH trials + FDA submission
⏳ Q1 2027: FDA approval (expected)

8 trials = comprehensive data package = strong FDA approval case.

Can't wait? Start with Mounjaro/Zepbound now and switch when retatrutide launches in 2027.

Last updated: March 19, 2026 | Next update: TRANSCEND-T2D-2 results (Q2 2026)