Why Was the ALS Drug Relyvrio Withdrawn from the Market?

Relyvrio (a combination of sodium phenylbutyrate and taurursodiol) was voluntarily withdrawn from the market in the United States and Canada in early 2024 ^[1][2]. The manufacturer made this decision after a large, late-stage clinical trial known as the PHOENIX trial showed that the medication was not effective at slowing the progression of Amyotrophic Lateral Sclerosis (ALS) ^[3][4].

Learning that a previously approved treatment has been withdrawn is deeply disappointing and emotionally devastating, especially when dealing with a disease like ALS where treatment options are already so limited.

Understanding the Initial Approval

To understand why Relyvrio was withdrawn, it helps to know how it was approved in the first place. In September 2022, the U.S. Food and Drug Administration (FDA) granted approval for Relyvrio based on the results of a smaller Phase 2 study called the CENTAUR trial ^[5][6]. This study, which included 137 participants, suggested that the drug could slow the loss of physical function and potentially extend survival ^[7].

Because ALS is a severe disease with high unmet need, the FDA approved Relyvrio based on these early results ^[8]. This allowed patients immediate access to the drug while the manufacturer conducted a larger, mandatory confirmatory study to prove it worked ^[9].

The PHOENIX Trial Results

The confirmatory Phase 3 study, known as the PHOENIX trial, was designed to test Relyvrio in a much larger group of patients over 48 weeks ^[3]. Unfortunately, the results from this larger trial did not support the earlier hopeful findings.

The PHOENIX trial found that there was no significant difference between the group taking Relyvrio and the group taking a placebo (an inactive dummy pill) when it came to slowing down the decline of physical functions ^[3][1]. The trial also did not show any improvement in secondary goals, such as breathing function or overall survival ^[10].

Because the medication failed to demonstrate a clinical benefit in this rigorous study, the manufacturer voluntarily chose to withdraw Relyvrio’s marketing authorizations ^[2][3].

What This Means for Your Care Plan

The withdrawal of Relyvrio means the medication is no longer available as an FDA-approved treatment for new patients ^[1]. However, if you are currently taking Relyvrio, you do not necessarily have to stop immediately.

• Continuing Relyvrio: When the drug was withdrawn, the manufacturer announced a program to provide the drug free of charge to patients who were already taking it, provided that the patient and their doctor agree it is beneficial to continue ^[2].
• Transitioning Off: If you and your doctor decide to stop the medication, it is critical that you do so under medical supervision. Your neurologist will guide you on how to safely transition off the drug to minimize any sudden changes to your care plan.

Other Approved Treatment Options

Your care team can help you explore other FDA-approved therapies that have proven benefits for ALS management ^[11]:

• Riluzole: The first FDA-approved treatment for ALS, which has been shown to extend survival ^[12].
• Edaravone: A medication available via IV or oral suspension, approved to help slow the decline of physical function ^[13][14].
• Tofersen (Qalsody): A targeted therapy specifically for the estimated 2% of ALS patients whose disease is caused by a mutation in the SOD1 gene ^[11][15].

It is important to review your treatment plan with your care team to ensure you are receiving the most effective, evidence-based care available today.