GC-1 selectively activates TRβ receptors, which are predominantly expressed in the liver. This drives cholesterol metabolism (LDL-C lowering), lipid oxidation, and metabolic rate without activating TRα receptors in the heart that cause tachycardia and cardiac stress.

Is GC-1 FDA approved?

No. GC-1 (Sobetirome) is not FDA-approved. It was developed by Quatrix/QRX Pharma and reached Phase I clinical trials but was not advanced further. It remains a research compound.

What is GC-1 used for in research?

GC-1 is researched for cholesterol lowering, NAFLD/NASH (liver fat reduction), metabolic syndrome, obesity, and emerging applications in X-linked adrenoleukodystrophy (X-ALD) and remyelination in multiple sclerosis.

How is GC-1 different from thyroid hormones?

T3/T4 activate both TRα (heart, bone) and TRβ (liver, metabolism). This causes cardiac side effects that limit their use for metabolic purposes. GC-1 is ~10× selective for TRβ over TRα, providing metabolic benefits while sparing the heart.

Thyromimetic • Selective TRβ Agonist

GC-1: Sobetirome Thyroid Mimetic

Q: What is GC-1 (Sobetirome)?

GC-1, also known as Sobetirome, is a synthetic thyromimetic compound that selectively activates thyroid hormone receptor beta (TRβ). Unlike natural thyroid hormones (T3/T4) which activate both TRα and TRβ, GC-1 preferentially binds TRβ, allowing metabolic benefits without cardiac side effects.

Q: Has GC-1 been tested in humans?

Yes. A Phase I clinical study in euthyroid men showed substantial LDL-C lowering without significant changes in heart rate or the thyroid axis. However, development was discontinued and it has not progressed to Phase III trials.

By MeetPeptide Research Team

Last updated: March 2026

GC-1 (Sobetirome) is a selective thyroid hormone receptor beta agonist that lowers LDL cholesterol and boosts metabolism without the cardiac side effects of natural thyroid hormones. Phase I human data confirms LDL-C reduction with no heart rate changes.

TRβ

Selective
Receptor Target

TRβ/TRα
Selectivity

Ph I

Human Clinical
Data Available

Background

What Is GC-1 (Sobetirome)?

GC-1 was developed as a liver-selective thyromimetic. Natural thyroid hormones (T3/T4) activate both TRα (heart, bone, CNS) and TRβ (liver, metabolism). By selectively targeting TRβ, GC-1 can drive cholesterol clearance and metabolic effects while avoiding tachycardia, bone loss, and thyroid axis suppression.

🎯

TRβ Selectivity

Approximately 10× selectivity for TRβ over TRα. TRβ mediates the metabolically beneficial effects of thyroid hormones — cholesterol lowering, lipid oxidation, metabolic rate increase.

📉

LDL-C Reduction

TRβ activation in the liver upregulates LDL receptor expression, driving clearance of LDL cholesterol from the bloodstream. Phase I data shows substantial LDL-C lowering in euthyroid men.

🫀

Cardiac Sparing

By avoiding TRα activation, GC-1 does not increase heart rate, cause arrhythmias, or induce cardiac hypertrophy — the main limitations of thyroid hormone therapy.

🧠

Emerging CNS Applications

Research exploring GC-1 prodrugs for remyelination in X-linked adrenoleukodystrophy (X-ALD) and multiple sclerosis. Thyroid hormones are critical for oligodendrocyte differentiation.

Research

What the Research Shows

📋

Context: GC-1 has extensive preclinical data and Phase I human data. It was developed for cholesterol lowering but development was discontinued. The concept has been validated — resmetirom (Rezdiffra), a related TRβ agonist, received FDA approval in 2024 for NASH, proving the mechanism works.

LDL-C Lowering — Phase I in Euthyroid Men

Substantial LDL-C reduction without heart rate changes or thyroid axis disruption

Positive

Liver Fat Reduction — Animal Models

Multiple preclinical models show hepatic lipid reduction and NAFLD improvement

Positive

Cardiac Safety — No TRα Effects

No significant heart rate increases in human or animal studies

Favorable

Remyelination (Preclinical)

GC-1 prodrug (Sob-AM2) shows CNS-targeted remyelination in animal models

Preliminary

Safety

Side Effects & Safety Profile

Cardiac Effects

No significant heart rate changes in Phase I — key safety feature

None

Thyroid Axis Disruption

No significant changes in TSH, T3, or T4 at therapeutic doses

None

Long-term Safety

Limited — only Phase I data in humans, no long-term studies

Unknown

Sources

Study Citations

Phase I Clinical

Sobetirome is a TRβ- and liver-selective thyromimetic that can effect substantial LDL-C lowering without significant changes in heart rate or the thyroid axis in euthyroid men

Lin VH, Klepp HM, Hanley RM. · Endocrine Society Annual Meeting, 2008

Review

Sobetirome: a case history of bench-to-clinic drug discovery and development

Heart Failure Reviews, 2010 · doi: 10.1007/s10741-008-9122-x

Liver Disease

GC-1: A Thyromimetic With Multiple Therapeutic Applications in Liver Disease

Hepatology, 2018 · PMC5885148

TRβ Review

Selective Thyroid Hormone Receptor-Beta (TRβ) Agonists: New Perspectives for Metabolic and Neurodegenerative Disorders

Frontiers in Medicine, 2020 · PMID: 32733906

Self-Assessment

Who Researches GC-1?

This Research Is Commonly Explored By People Who...

Are interested in thyroid hormone pharmacology and selective receptor activation
Want to understand metabolic enhancement without cardiac risk
Follow the TRβ agonist drug class (including FDA-approved resmetirom)
Are researching approaches to cholesterol, NAFLD, or metabolic syndrome

This Research May Not Be Relevant If...

You want FDA-approved options — see resmetirom (Rezdiffra) for NASH
You expect thyroid replacement — GC-1 is not a T3/T4 replacement
You want extensive human safety data — only Phase I exists

📚

Want the Complete Protocol Guide?

Dosing schedules, interaction warnings, and cycle protocols for 50+ compounds — all in one place.

Get the Guide →

⚕️ Disclaimer: This is educational content, not medical advice.

Bottom Line

Key Takeaways

✅ What We Know

~10× selective for TRβ over TRα
Phase I showed LDL-C lowering without cardiac effects
Concept validated by FDA-approved resmetirom
Extensive preclinical data in liver disease models
Emerging CNS applications (remyelination)

⚠️ What We Don't Know

Development discontinued — no Phase II/III data
Not FDA approved
Long-term safety in humans unestablished
Optimal dosing protocol not finalized
Not a peptide — small molecule thyromimetic

🔬 Verified Research Source

Third-party tested compounds from Swiss Chems — one of the most trusted research suppliers.

🧬 GC-1 (Sobetirome) Buy from Swiss Chems — Lab-tested, verified purity → Shop Now

Affiliate link — supports MeetPeptide at no extra cost.

⚠️ Disclaimer

GC-1 (Sobetirome) is NOT FDA approved. Development was discontinued after Phase I. A related TRβ agonist (resmetirom/Rezdiffra) received FDA approval for NASH in 2024. This page is for educational purposes only. Not medical advice. Research Only