GC-1: Sobetirome Thyroid Mimetic
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.
Receptor Target
Selectivity
Data Available
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.
Approximately 10× selectivity for TRβ over TRα. TRβ mediates the metabolically beneficial effects of thyroid hormones — cholesterol lowering, lipid oxidation, metabolic rate increase.
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.
By avoiding TRα activation, GC-1 does not increase heart rate, cause arrhythmias, or induce cardiac hypertrophy — the main limitations of thyroid hormone therapy.
Research exploring GC-1 prodrugs for remyelination in X-linked adrenoleukodystrophy (X-ALD) and multiple sclerosis. Thyroid hormones are critical for oligodendrocyte differentiation.
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.
Side Effects & Safety Profile
Study Citations
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
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Key Takeaways
- ~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)
- 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
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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
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