Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library

TUDCA (tauroursodeoxycholic acid, taurursodiol): what the evidence says

Name: TUDCA (tauroursodeoxycholic acid, taurursodiol)
Published: 2026-10-27

At a glance

What it is: Caution Not a peptide. TUDCA is a bile acid (ursodeoxycholic acid joined to taurine), a small molecule, not an amino-acid chain. It is listed here only because it is sold alongside research peptides. ^R1 It is not FDA-approved on its own; it was one of two ingredients in the ALS drug Relyvrio, which has since been discontinued. ^{R2, R3}

What the evidence says: Human in a 199-person RCT in primary biliary cholangitis, TUDCA lowered a key liver enzyme about as often as the approved drug UDCA. ^R4 In ALS, a 34-person pilot was positive, but the 337-person phase 3 missed its primary endpoint, and the TUDCA-containing drug Relyvrio failed its phase 3 and was withdrawn. ^{R5, R6, R3}

Biggest risks: generally well tolerated in trials; mild stomach and gut effects were most common. ^{R6, R4} Long-term supplement safety and product quality are not well studied.

Rating


Human Human evidence	Limited: one RCT in a liver disease (n = 199) plus small trials; negative phase 3 data in ALS ^{R4, R6, R3}
Animal Animal / lab evidence	Not reviewed
Regulatory	Not FDA-approved on its own (Relyvrio, which contained it, is discontinued) ^R2 · not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page ^{R7, R8, R9} · not named by WADA ^R10
Established human dose	No (trial amounts only; see Study details)

Evidence verdict: Primary biliary cholangitis: Limited (one 199-person RCT in China, similar to UDCA) · ALS (TUDCA alone): Tested, not shown (phase 3 TUDCA-ALS missed its primary endpoint) · ALS (Relyvrio combination): Tested, not shown (phase 3 PHOENIX failed; withdrawn) · Insulin sensitivity: Very limited (one 20-person, 4-week RCT) · Liver protection while using SARMs or steroids: No human data

This page reports what studies used. It is not dosing advice.

Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source

About the evidence: the best liver data come from one non-inferiority trial against UDCA in one country. The ALS story shows how a promising small trial can fail in a larger one.

What is it?

Related pages: glutathione, mots-c, rad-140.

Does it work?

Human Primary biliary cholangitis (RCT, n = 199): after 24 weeks, a key liver enzyme (ALP) fell by more than 25% in 76% on TUDCA vs 81% on UDCA, a difference that was not significant. ^R4
Human Cirrhosis (n = 23): a small 6-month study of TUDCA in liver cirrhosis. ^R11
Human ALS, TUDCA alone: a 34-person phase 2 found more responders on TUDCA (87% vs 43%) over 54 weeks; ^R5 but the phase 3 TUDCA-ALS trial (337 enrolled) missed its primary endpoint and showed no differences in secondary endpoints, including survival. ^{R6, R12} Full peer-reviewed results were not found. UNVERIFIED
Human ALS, Relyvrio (sodium phenylbutyrate plus TUDCA): CENTAUR (phase 2) slowed functional decline, ^{R13, R14} leading to FDA approval in 2022; the phase 3 PHOENIX trial (NCT05021536, 664 enrolled) ^R15 showed no benefit on the ALSFRS-R functional score at 48 weeks, ^R3 and the sponsor began withdrawing the drug's US and Canadian marketing authorizations. ^{R3, R2}
Human Insulin sensitivity (RCT, n = 20): in obese adults, 4 weeks of TUDCA raised liver and muscle insulin sensitivity by about 30% vs placebo. ^R16
Unknown Protecting the liver while using SARMs or oral steroids: no human data.

Is it safe?

Human Well tolerated in the liver and ALS trials; mild stomach and gut effects were the most common complaints, in both TUDCA and placebo groups. ^{R6, R4}
Unknown Long-term use as a supplement has not been studied.
Supplement products are not reviewed by FDA for content before sale. UNVERIFIED for any specific product.

Gray-market vials: extra risks

A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe.

Is it legal?

US: not FDA-approved as a single-ingredient drug; no single-ingredient Drugs@FDA application found (openFDA searched Oct 27, 2026).
Related approvals: Relyvrio (sodium phenylbutyrate plus taurursodiol) was approved for ALS in Sep 2022 and is now discontinued. ^{R2, R3} The parent bile acid ursodiol (UDCA) is FDA-approved, for example as Actigall. ^R17
Compounding: not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page. ^{R7, R8, R9}
Sport: not named on WADA's 2026 Prohibited List. ^R10 Whether S0 applies is unclear: taurursodiol has held a drug approval, and approval status outside the US was not checked. UNVERIFIED

Study details

These are amounts researchers used, not recommendations.

Study	People / model	Route	Amount used	Follow-up	Reported	Citation
Ma 2016 (RCT)	199 adults with primary biliary cholangitis	Oral	250 mg three times daily (vs UDCA)	24 weeks	ALP fell over 25% in 76% vs 81% on UDCA (not significant)	PMID 27893675
Kars 2010 (RCT)	20 obese adults	Oral	1,750 mg/day	4 weeks	Liver and muscle insulin sensitivity up about 30%	PMID 20522594
Elia 2016 (phase 2 RCT)	34 adults with ALS, on riluzole	Oral	1 g twice daily	54 weeks	More responders (87% vs 43%)	PMID 25664595
TUDCA-ALS (phase 3)	337 adults with ALS, on riluzole	Oral	1 g twice daily	18 months	Missed primary endpoint	^{R12, R6}

Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 27, 2026)

^R1 PubChem CID 9848818, Tauroursodeoxycholic acid (synonyms TUDCA, taurursodiol), checked Oct 27, 2026. https://pubchem.ncbi.nlm.nih.gov/compound/9848818
^R2 Drugs@FDA, Relyvrio (sodium phenylbutyrate and taurursodiol), application NDA216660 (openFDA drugsfda record checked Oct 27, 2026). https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=NDA216660
^R3 Ketabforoush A, et al. Sodium phenylbutyrate and tauroursodeoxycholic acid: a story of hope turned to disappointment in amyotrophic lateral sclerosis treatment. Clin Drug Investig. 2024;44(7):495-512 (review reporting PHOENIX results). PMID 38909349
^R4 Ma H, et al. Medicine (Baltimore). 2016. PMID 27893675
^R5 Elia AE, et al. Eur J Neurol. 2016. PMID 25664595
^R6 TUDCA-ALS consortium. Announcement of top-line results from the European phase 3 clinical trial of TUDCA in ALS, Mar 27, 2024. https://www.tudca.eu/top-line-results-announcement/
^R7 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
^R8 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
^R9 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
^R10 WADA. The 2026 Prohibited List, full list checked; compound not named. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
^R11 Pan XL, et al. J Huazhong Univ Sci Technolog Med Sci. 2013. PMID 23592128
^R12 ClinicalTrials.gov NCT03800524, TUDCA-ALS, phase 3 of TUDCA added to riluzole, Humanitas Mirasole, 337 enrolled, registry status unknown (CT.gov API v2, checked Oct 27, 2026). https://clinicaltrials.gov/study/NCT03800524
^R13 Paganoni S, et al. N Engl J Med. 2020. PMID 32877582
^R14 ClinicalTrials.gov NCT03127514, CENTAUR, phase 2 of AMX0035, Amylyx, completed (CT.gov API v2, checked Oct 27, 2026). https://clinicaltrials.gov/study/NCT03127514
^R15 ClinicalTrials.gov NCT05021536, PHOENIX, phase 3 of AMX0035 (sodium phenylbutyrate plus taurursodiol), Amylyx, 664 enrolled (CT.gov API v2, checked Oct 27, 2026). https://clinicaltrials.gov/study/NCT05021536
^R16 Kars M, et al. Diabetes. 2010. PMID 20522594
^R17 Drugs@FDA, Actigall (ursodiol), application NDA019594 (openFDA drugsfda record checked Oct 27, 2026). https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=NDA019594

Disclaimer

This page is for education and harm reduction, not medical advice or a recommendation to use TUDCA (tauroursodeoxycholic acid, taurursodiol). This compound is not FDA-approved. Any product sold under this name in the US is unregulated. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).