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Name: Relyvrio
Synonyms: Albrioza, AMX0035
Therapy Type: Combination, Small Molecule (timeline)
Target Type: Other (timeline)
Condition(s): Amyotrophic Lateral Sclerosis, Alzheimer's Disease
U.S. FDA Status: Amyotrophic Lateral Sclerosis (Approved), Alzheimer's Disease (Phase 2)
Company: Amylyx Pharmaceuticals Inc
Approved for: ALS


AMX0035 is a proprietary, oral combination of two drugs already in use, sodium phenylbutyrate (PB) and tauroursodeoxycholic acid (TUDCA). PB is prescribed under the brand name Buphenyl to treat urea cycle disorders. It acts as a scavenger to facilitate the excretion of excess nitrogen. Interest in repurposing PB to treat neurodegenerative diseases stems from its action as a chemical chaperone, which inhibits endoplasmic reticulum stress responses and neuronal cell death induced by accumulation of misfolded or mutant proteins (Kubota et al., 2006). PB also epigenetically regulates gene expression by inhibiting histone deacetylase.

TUDCA is a naturally occurring bile acid with anti-apoptotic and neuroprotective effects. TUDCA has been used for centuries in Asian medicine, and is widely available over the counter as a nutritional supplement. It is used clinically to help dissolve gallstones, and treat some forms of liver disease. TUDCA inhibits mitochondria-mediated apoptosis and the formation of reactive oxygen species, and blocks apoptosis caused by ER stress (reviewed in Daruich et al., 2019).

The only preclinical data comparing AMX0035 to PB and TUDCA individually describes gene expression and metabolomic changes in ALS patient-derived primary skin cells (Fels et al., 2022). The combination changed more genes and different genes than did PB or TUDCA alone. Both compounds show activity in mouse models of neurodegeneration. PB resulted in fewer plaques and better performance in a spatial memory task in APPswePS1delta9 (Wiley et al., 2011). PB prolonged survival in an ALS mouse model, both when given alone and together with riluzole (Ryu et al., 2005Del Signore et al., 2009). PB was also reported to protect against neurodegeneration in models of α-synuclein toxicity and Parkinson’s disease (Sturm et al., 2016; Ono et al., 2009). TUDCA reduced amyloid deposition and improved cognition in APP/PS1 mice (Nunes et al., 2012). It also improved pathology and behavior in mouse models of Parkinson’s disease, HD, and ALS (reviewed by Ackerman and Gerhard, 2016).

In a clinical study conducted 10 years ago in Milan, Italy, TUDCA alone reportedly had a treatment benefit in ALS. In a Phase 2 trial in 34 ALS patients, treatment with 2 g per day for one year slowed deterioration on the ALS Functional Rating Scale (ALSFRS-R) compared with placebo (Elia et al., 2015). Following on those results, investigators in February 2019 began a Phase 3 trial of TUDCA. It is enrolling 440 ALS patients at 25 sites in seven European Union countries, for an 18-month course of 2 g daily plus riluzole. The primary outcome will be change on the ALSFRS-R; the trial is set to end in December 2022. 

In another trial, PB was judged safe and well tolerated after open-label dose escalation in 40 ALS patients (Cudkowicz et al., 2009). No efficacy measures were included, but PB at 9 g/day was sufficient to induce changes in histone acetylation in patients’ blood cells. PB was also evaluated in Huntington’s (PHEN-HD trial) and Parkinson’s diseases; results are not published.


In June 2017, Amylyx began CENTAUR, a Phase 2 safety and efficacy study of AMX0035 in people with ALS. Funded by foundations and conducted at 25 academic centers in the U.S., the trial enrolled 137 patients aged 18-80 who had been symptomatic for 18 months or less. Participants were randomized 2 to 1 to take either 3 grams PB plus 1 g TUDCA twice daily, or placebo. They could also take edaravone or riluzole. Primary outcomes were disease progression, measured as change on the ALSFRS-R compared with placebo, adverse events, and number of people who stayed on AMX0035 for six months. Secondary outcomes included measures of muscle strength, vital lung capacity, survival, need for tracheostomy, and hospitalizations. Other secondary endpoints were plasma phosphorylated neurofilament H and unspecified imaging biomarkers. The study was completed in September 2019.

According to published trial results, AMX0035 slowed decline on the ALSFRS-R. The treated group lost 1.24 points per month compared to 1.66 for placebo (Sep 2020 news on Paganoni et al., 2020). The benefit appeared over and above any effects of riluzole and edaravarone. No significant differences between AMX0035 and placebo were noted in secondary outcomes. The most common side effects were diarrhea and abdominal pain, which occurred in 5 percent of participants and lessened with time. Ninety-eight out of 137 participants completed the trial.

Between March 2018 and September 2019, 95 CENTAUR completers went on to an open-label extension study, whose primary outcome was adverse events. An analysis of survival in this phase concluded that people who originally had been randomized to drug lived 6.5 months longer than those originally in the placebo group. The participants from the active drug group survived a median of 24 months after randomization, compared to 18.5 months for the placebo group, a statistically significant difference (Pagnanoni et al., 2021Paganoni et al., 2022). The study was completed in 2021. 

From August 2018 to April 2021, Amylyx ran PEGASUS, a Phase 2 trial in Alzheimer’s disease. Conducted at 10 sites in the U.S., the study enrolled 95 participants with a biomarker-confirmed diagnosis of probable Alzheimer’s disease or mild cognitive impairment due to AD, and randomized them to an undisclosed dose of AMX0035 or placebo for 24 weeks. The primary outcome was safety; secondary outcomes include volumetric and functional MRI, cognition, and psychiatric symptoms, as well as unspecified CSF and plasma biomarkers. The company reported topline results at the November 2021 CTAD conference (press release). AMX0035 met safety and tolerability endpoints, with gastrointestinal side effects in line with previous clinical trials. The trial was not powered to detect efficacy and clinical endpoints revealed none. Treatment led to a significant reduction in CSF AD biomarkers Tau and pTau181, and an increased Aβ42/40 ratio. A marker of DNA damage, 8-hydroxy-2' -deoxyguanosine, was higher in the treated group. At the December 2022 CTAD conference, the company reported changes favoring drug in CSF biomarkers neurogranin, fABP3, and YKL40, but not in NfL, GFAP, an inflammation composite, soluble insulin receptor, or 24S-OH-cholesterol.

In November 2020, Amylyx started a compassionate use program for 40 people with ALS and, in August 2021, started a Phase 1/2 drug exposure/pharmacodynamic study in 14 people with ALS.

In October 2021, Amylyx began PHOENIX, a 600-participant, international Phase 3 trial in ALS, comparing a 48-week course of an undisclosed dose of AMX0035 to placebo. The drug is to be delivered by mouth or feeding tube once daily for three weeks, then twice daily for the rest of the study. Primary outcomes are slope change on the ALS-FRS and survival, adverse events and number of people able to complete the trial; secondary outcomes include various functional and quality-of-life measures but not biomarkers such as neurofilament light or others. Ongoing at around 70 sites in the United States and Europe, the trial is expected to run until November 2023, with topline results expected in 2024. An open-label extension is planned to start in late 2022. An expanded access program exists, as well.

On March 30, 2022, after a day-long meeting, the FDA's Peripheral and Central Nervous System Drugs Advisory Committee voted 6 to 4 against approving AMX0035 for the treatment of ALS based on the data submitted to the agency. In its briefing document issued prior to this AdComs meeting, the FDA had registered concerns with the statistical analysis method chosen for the primary endpoint, with the accounting of deaths that occurred during the study, center effects, group imbalances in incident concomitant medications, and other weaknesses in the data. For the purposes of the AdComs meeting, the briefing document concluded that the available evidence did not amount to substantial evidence of effectiveness. A decision was initially expected in June 2022, but the FDA pushed it back to September, citing a need for more time to evaluate the data.

In May 2022, company scientists published data claiming that AMX0035 treatment lengthened tracheostome/ventilation-free survival and delayed first hospitalization in the CENTAUR trial (Paganoni et al., 2022). 

On June 10, AMX0035, brand name Albrioza, received conditional marketing approval from Health Canada, the country's drug regulatory agency. The approval is contingent on the outcome of the ongoing PHOENIX trial (see Notice of Compliance).

On July 5, Amylyx announced the U.S. FDA would reconvene the advisory committee to discuss a "major amendment" to the AMX0035 application (press release). In this rare second meeting, the committee voted in favor of the drug. The decision came after new analysis of data from the CENTAUR Phase 2 trial and long-term extension, and a pledge from Amylyx to voluntarily withdraw the drug if it fails to show efficacy in their ongoing Phase 3 trial (Endpoints News). On September 29, the FDA approved Albrioza (Oct 2022 news). For a review, see Sun, Li & Bedlack, 2023.

For details on AMX0035 trials, see

Clinical Trial Timeline

  • Phase 2
  • Study completed / Planned end date
  • Planned end date unavailable
  • Study aborted
Sponsor Clinical Trial 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033
Amylyx Pharmaceuticals Inc NCT03533257

Last Updated: 07 Dec 2022


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News Citations

  1. Micro Nudge? Positive Phase 2 Results for ALS Combination Drug
  2. FDA Approves ALS Drug on Phase 2 Data

Research Models Citations

  1. APPSwe/PSEN1dE9 (C3-3 x S-9)
  2. APPPS1

Paper Citations

  1. . Trial of Sodium Phenylbutyrate-Taurursodiol for Amyotrophic Lateral Sclerosis. N Engl J Med. 2020 Sep 3;383(10):919-930. PubMed.
  2. . Long-term survival of participants in the CENTAUR trial of sodium phenylbutyrate-taurursodiol in amyotrophic lateral sclerosis. Muscle Nerve. 2021 Jan;63(1):31-39. Epub 2020 Oct 30 PubMed.
  3. . Survival analyses from the CENTAUR trial in amyotrophic lateral sclerosis: Evaluating the impact of treatment crossover on outcomes. Muscle Nerve. 2022 Aug;66(2):136-141. Epub 2022 May 31 PubMed.
  4. . Effect of sodium phenylbutyrate/taurursodiol on tracheostomy/ventilation-free survival and hospitalisation in amyotrophic lateral sclerosis: long-term results from the CENTAUR trial. J Neurol Neurosurg Psychiatry. 2022 May 16; PubMed.
  5. . Suppressive effects of 4-phenylbutyrate on the aggregation of Pael receptors and endoplasmic reticulum stress. J Neurochem. 2006 Jun;97(5):1259-68. Epub 2006 Mar 15 PubMed.
  6. . Review: The bile acids urso- and tauroursodeoxycholic acid as neuroprotective therapies in retinal disease. Mol Vis. 2019;25:610-624. Epub 2019 Oct 14 PubMed.
  7. . Effects of PB-TURSO on the transcriptional and metabolic landscape of sporadic ALS fibroblasts. Ann Clin Transl Neurol. 2022 Oct;9(10):1551-1564. Epub 2022 Sep 9 PubMed.
  8. . Phenylbutyric acid reduces amyloid plaques and rescues cognitive behavior in AD transgenic mice. Aging Cell. 2011 Jun;10(3):418-28. PubMed.
  9. . Sodium phenylbutyrate prolongs survival and regulates expression of anti-apoptotic genes in transgenic amyotrophic lateral sclerosis mice. J Neurochem. 2005 Oct 21; PubMed.
  10. . Combined riluzole and sodium phenylbutyrate therapy in transgenic amyotrophic lateral sclerosis mice. Amyotroph Lateral Scler. 2009 Apr;10(2):85-94. PubMed.
  11. . Neuroprotection by Epigenetic Modulation in a Transgenic Model of Multiple System Atrophy. Neurotherapeutics. 2016 Oct;13(4):871-879. PubMed.
  12. . A chemical chaperone, sodium 4-phenylbutyric acid, attenuates the pathogenic potency in human alpha-synuclein A30P + A53T transgenic mice. Parkinsonism Relat Disord. 2009 Nov;15(9):649-54. PubMed.
  13. . TUDCA, a Bile Acid, Attenuates Amyloid Precursor Protein Processing and Amyloid-β Deposition in APP/PS1 Mice. Mol Neurobiol. 2012 Mar 23; PubMed.
  14. . Bile Acids in Neurodegenerative Disorders. Front Aging Neurosci. 2016;8:263. Epub 2016 Nov 22 PubMed.
  15. . Phase 2 study of sodium phenylbutyrate in ALS. Amyotroph Lateral Scler. 2009 Apr;10(2):99-106. PubMed.

Other Citations

  1. Elia et al., 2015

External Citations

  1. press release
  2. day-long meeting
  3. briefing document
  4. Notice of Compliance
  5. press release
  6. Endpoints News
  7. Sun, Li & Bedlack, 2023

Further Reading


  1. . Sodium Phenylbutyrate-Taurursodiol for ALS. N Engl J Med. 2020 Dec 3;383(23):2294. PubMed.
  2. . Sodium Phenylbutyrate-Taurursodiol for ALS. N Engl J Med. 2020 Dec 3;383(23):2293-2294. PubMed.
  3. . Sodium Phenylbutyrate-Taurursodiol for ALS. Reply. N Engl J Med. 2020 Dec 3;383(23):2294. PubMed.
  4. . Hastening the Diagnosis of Amyotrophic Lateral Sclerosis. Neurology. 2022 May 16; PubMed.
  5. . Tauroursodeoxycholic acid (TUDCA) supplementation prevents cognitive impairment and amyloid deposition in APP/PS1 mice. Neurobiol Dis. 2013 Feb;50:21-9. Epub 2012 Sep 10 PubMed.
  6. . Amyloid-β pathology is attenuated by tauroursodeoxycholic acid treatment in APP/PS1 mice after disease onset. Neurobiol Aging. 2015 Jan;36(1):228-40. Epub 2014 Sep 28 PubMed.
  7. . Phenylbutyrate rescues dendritic spine loss associated with memory deficits in a mouse model of Alzheimer disease. Hippocampus. 2010 Nov 10; PubMed.
  8. . Phenylbutyrate is a multifaceted drug that exerts neuroprotective effects and reverses the Alzheimer´s disease-like phenotype of a commonly used mouse model. Curr Pharm Des. 2013 Feb 19; PubMed.