Last reviewed 2026-04-23 · How we verify

LT3 (liothyronine)

M. Medici · Phase 3 active Small molecule

LT3 (liothyronine) is a Thyroid hormone replacement Small molecule drug developed by M. Medici. It is currently in Phase 3 development for Hypothyroidism (replacement therapy), Myxedema coma (acute severe hypothyroidism). Also known as: Intervention group LT4/LT3 combination therapy.

Liothyronine is a synthetic form of triiodothyronine (T3) that binds to thyroid hormone receptors to increase metabolic rate and cellular energy production.

Liothyronine is a synthetic form of triiodothyronine (T3) that binds to thyroid hormone receptors to increase metabolic rate and cellular energy production. Used for Hypothyroidism (replacement therapy), Myxedema coma (acute severe hypothyroidism).

Likelihood of approval

58.3% vs 58.3% industry baseline

If approved by FDA: likely 2028–2030

Steps remaining: NDA/BLA submission

Confidence: High

Why this estimate

Baseline phase 3 → approval rate +58.3pp
Industry-wide phase 3 drugs reach approval ~58.3% of the time (BIO/Informa 2023 industry benchmark across all therapeutic areas).

Predicted approval windows by jurisdiction (conditional on FDA approval)

Regulator	Country	Likely year	Lag vs FDA
FDA	US	2028–2030	—
EMA	EU	2029–2031	+0.7 yr
MHRA	GB	2029–2031	+0.7 yr
Health Canada	CA	2029–2032	+0.9 yr
TGA	AU	2029–2032	+1.2 yr
PMDA	JP	2029–2032	+1.5 yr
NMPA	CN	2030–2033	+2.3 yr
MFDS	KR	2029–2032	+1.4 yr
CDSCO	IN	2029–2033	+1.8 yr
ANVISA	BR	2030–2033	+2.3 yr

Hover any row for the lag rationale. Lag estimates are reduced when the drug has FDA Breakthrough or EMA PRIME designation (sponsors file globally in parallel).

Estimate based on the BIO/Informa industry phase transition rates plus per-drug modifiers for therapeutic area, sponsor type, FDA designations, mechanism, and trial design. Per-jurisdiction lags from Tufts CSDD international approval studies. Not investment, clinical or regulatory advice. Methodology: /methodology#likelihood.

At a glance

Generic name	LT3 (liothyronine)
Also known as	Intervention group LT4/LT3 combination therapy
Sponsor	M. Medici
Drug class	Thyroid hormone replacement
Target	Thyroid hormone receptor alpha (TRα), Thyroid hormone receptor beta (TRβ)
Modality	Small molecule
Therapeutic area	Endocrinology
Phase	Phase 3

Mechanism of action

LT3 is the active thyroid hormone that regulates metabolism, thermogenesis, and protein synthesis by binding to thyroid hormone receptors (TRα and TRβ) in target tissues. It is more potent and faster-acting than levothyroxine (T4), the inactive precursor. LT3 directly stimulates mitochondrial oxidative metabolism and increases oxygen consumption across multiple organ systems.

Approved indications

Hypothyroidism (replacement therapy)
Myxedema coma (acute severe hypothyroidism)

Common side effects

Tachycardia
Palpitations
Tremor
Anxiety
Insomnia
Heat intolerance
Headache

Key clinical trials

Novel Approaches to the Treatment of Hypothyroidism (PHASE2, PHASE3)
T4/T3 Therapy in Hypothyroidism (PHASE2)
LT4/LT3 Combination Therapy Versus LT4 Monotherapy in Patients with Autoimmune Hypothyroidism. (PHASE3)
Developing Oral LT3 Therapy for Heart Failure - HFpEF (PHASE1, PHASE2)
Developing Oral LT3 Therapy for Heart Failure - HFrEF (PHASE1, PHASE2)
Energy Metabolism in Thyroidectomized Patients (PHASE2)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Source	Used for
ClinicalTrials.gov	Trial enrolment, design, endpoints, results

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

LT3 (liothyronine) CI brief — competitive landscape report
LT3 (liothyronine) updates RSS · CI watch RSS
M. Medici portfolio CI

Frequently asked questions about LT3 (liothyronine)

What is LT3 (liothyronine)?

LT3 (liothyronine) is a Thyroid hormone replacement drug developed by M. Medici, indicated for Hypothyroidism (replacement therapy), Myxedema coma (acute severe hypothyroidism).

How does LT3 (liothyronine) work?

Liothyronine is a synthetic form of triiodothyronine (T3) that binds to thyroid hormone receptors to increase metabolic rate and cellular energy production.

What is LT3 (liothyronine) used for?

LT3 (liothyronine) is indicated for Hypothyroidism (replacement therapy), Myxedema coma (acute severe hypothyroidism).

Who makes LT3 (liothyronine)?

LT3 (liothyronine) is developed by M. Medici (see full M. Medici pipeline at /company/m-medici).

Is LT3 (liothyronine) also known as anything else?

LT3 (liothyronine) is also known as Intervention group LT4/LT3 combination therapy.

What drug class is LT3 (liothyronine) in?

LT3 (liothyronine) belongs to the Thyroid hormone replacement class. See all Thyroid hormone replacement drugs at /class/thyroid-hormone-replacement.

What development phase is LT3 (liothyronine) in?

LT3 (liothyronine) is in Phase 3.

What are the side effects of LT3 (liothyronine)?

Common side effects of LT3 (liothyronine) include Tachycardia, Palpitations, Tremor, Anxiety, Insomnia, Heat intolerance.

What does LT3 (liothyronine) target?

LT3 (liothyronine) targets Thyroid hormone receptor alpha (TRα), Thyroid hormone receptor beta (TRβ) and is a Thyroid hormone replacement.

Drug class: All Thyroid hormone replacement drugs
Target: All drugs targeting Thyroid hormone receptor alpha (TRα), Thyroid hormone receptor beta (TRβ)
Manufacturer: M. Medici — full pipeline
Therapeutic area: All drugs in Endocrinology
Indication: Drugs for Hypothyroidism (replacement therapy)
Indication: Drugs for Myxedema coma (acute severe hypothyroidism)
Also known as: Intervention group LT4/LT3 combination therapy

Primary sources · FDA · ClinicalTrials.gov · EMA · SEC EDGAR · ChEMBL · Wikidata · full sourcing