New ALS drug wins approval from the FDA  

Relyvrio approved on the basis of clinical trial and extension study with 137 patients; first new ALS treatment since 2017

March 3, 2023

Relyvrio (sodium phenylbutyrate/taurursodiol) is the first new ALS treatment to receive FDA approval since 2017. 

Condition overview 1-5 

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease. It breaks down the nerve cells in the brain and spinal cord resulting in loss of voluntary muscle action. People may lose the ability to speak, eat, move and breathe. Muscle weakness affects approximately five per 100,000 people, with approximately 16,000 cases in the U.S.  

ALS symptoms most commonly develop between the ages of 55 to 75 with men slightly more likely than women to develop the condition. There is no cure for ALS. It ultimately leads to death within three to five years from onset of symptoms in most patients. 

Current Treatments 5 

ALS can be difficult to diagnose because early symptoms are similar to other neurological diseases. Delays in diagnosis can cause delays in treatment. Treatments don’t reverse the damage of ALS, but they can slow the progression of symptoms, prevent complications and preserve a patient’s independence.5 

  • Riluzole has been shown to prolong survival by about three months and extend the time before ventilatory support is needed. 
    • Exservan® (riluzole): 50 mg oral film.
    • Tiglutik ® (riluzole) mildly thick liquid approved for oral and PEG tube administration.
  • Radfacava® (edavarone): Edavarone is taken by IV infusion and has shown 33% smaller functional decline over 24 weeks of treatment compared to placebo in patients who were within two years of ALS diagnosis.4,5

Relyvrio overview 

Relyvrio (sodium phenylbutyrate/taurursodiol) is a powder for suspension supplied as sachets. It is an oral fixed-dose combination of sodium phenylbutyrate and taurursodiol. Administration is oral or via feeding tube and cost is anticipated to impact the pharmacy benefit. 

The wholesale acquisition cost for Relyvrio is $158,000 for a year’s supply. This is significantly higher than the cost effective annual price of $9,100 and $30,600 suggested by the Institute for Clinical and Economic Review (ICER) believes is cost-effective. Still, the figure is about $10,000 less than the list price of Radicava (edaravone), another ALS therapy that came onto the U.S. market five years ago. Amylyx anticipates sodium phenylbutyrate/taurursodiol may be added to standard of care therapies (i.e., riluzole and edavarone).  

Relyvrio significantly slowed the loss of physical function in people living with ALS.1 Relyvrio can be taken as a monotherapy or with existing approved treatments. 

Safety 1-4 

The most common adverse effects leading to discontinuation were diarrhea, abdominal pain, nausea and upper respiratory tract infection. Side effects impacted at least 15% of patients in a Phase 2 trial.  

Efficacy 1  

A multicenter Phase 2 clinical trial of 137 participants with ALS encompassed a six-month randomized, placebo-controlled phase and an open-label extension (OLE) long-term follow-up phase. Vital status was obtained (35-month maximum follow-up post-randomization) for 135 of 137 participants. The median overall survival was 25 months in those randomized to sodium phenylbutyrate/taurursodiol and 18.5 months among those randomized to placebo. 

In March 2022, the drug got mixed reviews from the FDA Peripheral and CNS advisory committee (4-yes; 6-no) on the question of whether sodium phenylbutyrate/taurursodiol is effective in the treatment of patients with ALS. In a Sept. 2022 meeting, the committee voted 7-yes, 2-no, on the same question.  

ALS Extended Pipeline 6,7 

The following table includes medications that could be approved for ALS in the next two years. 

Drug name 


Drug class 

Route of Admin 

Potential PDUFA Year 


AB Science 

Tyrosine kinase inhibitor 





Sigma 1 receptor agonist 





Selective fast skeletal muscle troponin activators 





Stabilizes proteins and activates autophagy 





PDE4&10 inhibitor and macrophage migration inhibitor 



Prime monitors the drug pipeline 

The drug pipeline is full of new, groundbreaking specialty drugs. Prime focuses on clinical strategies designed to keep clients ahead of drug trends — because it’s easier to manage change when you see it coming.  


  1. Amylyx Pharmaceuticals Announces FDA Approval of RELYVRIO™ for the Treatment of ALS. September 29, 2022. Accessed at: 
  2. National Institute of Neurological Disorders and Stroke. Search term: Amyotrophic lateral sclerosis. Accessed in April 2022 a t: Amyotrophic Lateral Sclerosis (ALS) Fact Sheet | National Institute of Neurological Disorders and Stroke (  
  3. Paganoni S, Macklin EA, Hendrix S, et al. Trial of sodium phenylbutyrate-taurursodiol for amyotrophic lateral sclerosis. NEJM 2020; 383: 919-930. Accessed in April 2022 at: Trial of Sodium Phenylbutyrate–Taurursodiol for Amyotrophic Lateral Sclerosis | NEJM  
  5. FDA Approves New Treatment Option for Patients with ALS. September 29, 2022. U.S. Foof and Drug Administration. Accessed at: 
  6. Search term: Motor Neuron Disease. Accessed in April 2022. 
  7. Search term: Amyotrophic lateral sclerosis. Accessed in April 2022 

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