The PHOENIX Trial:
A Clinical Trial for People
Living With Amyotrophic Lateral
Sclerosis (ALS)

Learn about eligibility and more

About the PHOENIX trial

The PHase 3 PHOENIX trial (NCT05021536) will evaluate if the investigational drug, SOdium PhENylbutyrate/TaurursodIol (ursodoXicoltaurine) (PB/TURSO), is effective and safe as a treatment for adults with ALS.

PB/TURSO is not currently approved by FDA or EMA. The trial will use a placebo (a substance that looks and tastes the same as the investigational drug but does not have any active substance) as a way to compare the safety and effectiveness of PB/TURSO.

  • Pre-clinical
  • Phase 1
  • Phase 2
  • Phase 3
  • Phase 4

PHOENIX is a phase 3 trial, in which many people will be participating in both the United States and Europe. Because PHOENIX is a randomized, double-blind trial, individuals will be chosen at random to receive PB/TURSO or placebo, and neither the doctors nor the participants will know who received the investigational drug.

What will the trial measure to determine if the investigational drug is safe and effective?

The PHOENIX trial will compare PB/TURSO and placebo groups across several measures that are important in ALS.

  • Safety and tolerability
  • Function and survival
    • The Revised Amyotrophic Lateral Sclerosis Rating Scale (ALSFRS-R) will be used to assess and monitor key measures of functional status, such as: speech, handwriting, walking, and more
  • Breathing: Slow Vital Capacity (SVC)
  • Participant quality of life and health status
  • Time it takes to transition through ALS disease stages
  • Survival without requiring permanent breathing support

Caregivers will be asked to complete a questionnaire at the baseline visit and every 12 weeks during the trial. A caregiver is a person who regularly looks after and provides the necessary care for a person with ALS. A caregiver can also be a professional, such as a hired personal assistant or hired nursing staff.

What should participants in the PHOENIX trial expect?

  • 48

    Each participant will be in the PHOENIX trial for approximately 1 year (48 weeks).

  • 60/40

    Participants in the PHOENIX trial will have a 60% chance of receiving PB/TURSO and 40% chance of receiving placebo.

  • Study visits

    The PHOENIX trial is designed to be telemedicine-friendly; in-clinic visits will occur at the start of the study and every 3 months (12 weeks) after for a total of up to 6 in-person visits. All other visits will be performed virtually.

  • Accessibility

    Some of the participating sites may arrange for shipment of the study drug to participants’ homes. For in-clinic visits, travel reimbursement will be provided.

  • Other meds

    If participants are taking riluzole and/or edaravone for ALS before the start of the trial, they may continue to take them during this trial.

    If participants are not already taking either medication, then they are not allowed to start riluzole or edaravone therapy during the trial.

What is PB/TURSO?1,2

PB/TURSO is an investigational drug, also known as AMX0035. PB/TURSO is a combination of sodium phenylbutyrate (PB) and taurursodiol (also called ursodoxicoltaurine; TURSO).

How is PB/TURSO administered to trial participants?

PB/TURSO is a powder that comes in packets, which can be mixed with water and taken by mouth or through a feeding tube. Placebo will be administered in the same way.

Am I potentially eligible?

Clinical trials have specific eligibility criteria to ensure that the goals of the study are met. Eligibility criteria differ from study to study.

The below are only select criteria for the PHOENIX trial. For a list of the full eligibility criteria for the PHOENIX trial please visit (NCT05021536). Select criteria includes:

  • Be at least 18 years old
  • Have been diagnosed with definite or clinically probable ALS (Based on revised El Escorial criteria by a physician who is experienced in management of ALS)
  • Have started experiencing ALS symptoms within the past 24 months
  • Have a slow vital capacity (SVC) of at least 55% at the time of screening
  • Be taking a stable dose of riluzole and/or edaravone at the time of screening if you choose to use these medications during the course of the PHOENIX trial (Participants are not allowed to start riluzole or edaravone therapy during the trial)
  • Does not need a tracheostomy or permanent assisted ventilation (PAV: > 22 hours of assisted ventilation daily for > 7 days)

Speak with your ALS doctor or care team to review the full list of eligibility criteria to determine if this is the right trial for you.

PHOENIX Trial Locations

PHOENIX is a clinical trial with sites in Europe and the United States. Select your region below to see what site is closest to you or click here to view a list of the clinical site locations.

Sites are activating on a rolling basis; please note that listed sites may not yet be active, but will be updated once they are. The latest information is available on

Your ALS doctor or care team can help you determine
next steps in terms of trial participation.


  1. Paganoni S, et al. N Engl J Med. 2020;383:919-930.
  2. Paganoni S, et al. Muscle Nerve. 2021;63:31-39.doi:10.1002/mus.27091.