Rhythm’s EMANATE Trial Misses the Mark—But Not the Signal

Drug development rarely fails cleanly. Sometimes, the headline says “missed endpoints,” but the data tells a more complicated story.

That’s exactly what happened with Rhythm Pharmaceuticals and its Phase 3 EMANATE trial evaluating setmelanotide.

The Headline: Primary Endpoints Not Met

EMANATE was a global, randomized, double-blind, placebo-controlled Phase 3 trial. Its goal was straightforward:

Test whether setmelanotide reduces BMI in patients with rare, genetically driven obesity linked to the MC4R pathway.

The trial included four genetic subgroups:

• POMC / PCSK1 (heterozygous variants)
• LEPR (heterozygous variants)
• SRC1 (NCOA1)
• SH2B1

Across all four groups, the primary endpoint—mean percentage BMI reduction vs placebo at 52 weeks—was not met.

Topline Results (Primary Analysis)

• POMC / PCSK1: –4.3% (p=0.15)
• LEPR: –3.6% (p=0.94)
• SRC1 (NCOA1): –4.0% (p=0.12)
• SH2B1: –1.7% (p=0.43)

Statistically, that’s a miss.

The Twist: Post Hoc Analyses Show Strong Signals

Here’s where things get interesting.

When researchers reanalyzed the data using different statistical approaches, a clearer signal emerged—especially in two subgroups.

Where It Worked?

POMC / PCSK1 (Hets):

• –5.5% BMI reduction (p=0.0010)
• Up to –9.7% in patients completing 52 weeks

SRC1 (NCOA1):

• –6.2% BMI reduction (p<0.0001)
• Up to –8.0% in completers

These are not weak effects.

They’re clinically meaningful—just not captured in the original primary analysis framework.

What Went Wrong?

This isn’t just a “drug failed” story. It’s a trial design and patient selection problem. According to David Meeker, the key issue lies in identifying:

“true loss-of-function variants”

In simple terms:

• Not all genetic mutations behave the same way
• Some patients may not respond to MC4R activation
• Mixing responders and non-responders dilutes the overall effect

That’s how you end up with:

• Weak primary endpoint results
• Strong signals in refined subgroups

Why This Still Matters?

Despite the miss, this trial answers an important question: Does MC4R activation work in genetically driven obesity?

The answer appears to be: Yes, but only in the right patients. And that’s a big deal.

Because these patients:

• Have severe, lifelong obesity
• Often lack any approved targeted treatments
• Are underserved by conventional weight-loss therapies

Safety Profile: No Surprises

From a safety standpoint, the data is reassuring. No new safety signals were observed.

Common side effects included:

• Skin hyperpigmentation
• Injection site reactions
• Nausea and vomiting
• Headache

All consistent with previous studies of setmelanotide.

What’s Next for Rhythm?

Rhythm isn’t backing down. Instead, it’s refining its strategy.

Immediate Next Steps

• Deeper analysis of EMANATE data
• Better genetic filtering of patients
• Focus on high-response subgroups

Pipeline Evolution

The company is moving toward next-generation MC4R agonists:

• Bivamelagon
• RM-718

It’s also exploring additional genetic targets identified in earlier trials, including:

• SEMA3 family
• PHIP
• TBX3
• PLXNA family

The Bigger Shift: Precision Obesity Treatment

This trial highlights a broader industry trend: Obesity is not one disease. It’s many.

And treating it effectively requires:

• Genetic stratification
• Targeted therapies
• Smarter trial design

Setmelanotide—marketed as IMCIVREE, already has approvals for certain rare genetic obesity conditions. But EMANATE shows the next step:

Moving from “broad rare obesity” to ultra-precise genetic targeting

Final Takeaway

At first glance, EMANATE looks like a failure. But that’s a shallow read.

The deeper story is this:

• The drug shows real efficacy
• The biology is validated
• The targeting needs refinement

For Rhythm, this isn’t the end of the road. It’s a course correction. And in rare disease drug development, that’s often how breakthroughs actually happen.