Prilenia’s Application for European Approval of Pridopidine Withdrawn

Regular HDBuzz readers may recall our September 2024 article examining the long history of pridopidine in Huntington’s disease (HD) research. In that piece, we covered the drug’s journey through four clinical trials – MermaiHD, HART, PRIDE-HD, and PROOF-HD – none of which met their primary endpoints. We also reported on Prilenia’s submission of an application to the European Medicines Agency (EMA) for approval of pridopidine, marketed under the brand name Nurzigma. We noted at the time that submitting an application is a step every drug goes through, approved and rejected alike, and that the community should wait to see how the evaluation unfolded before drawing conclusions.

We now have an answer.

Clinical trial data analysis

Following the completion of PROOF-HD, Prilenia analyzed their results in detail, looking for any signals of benefit within the trial data. One analysis focused on a subgroup of participants who were not taking antidopaminergic medications (ADMs), which are drugs commonly used in HD to manage chorea and behavioral symptoms such as tetrabenazine or risperidone. 

We covered this in depth when the PROOF-HD results were published in Nature Medicine inSeptember 2025. It was on the basis of this subgroup not taking ADMs – fewer than half of the original 499 PROOF-HD participants – that Prilenia built its EMA application, seeking approval specifically for adults with early HD who were not on ADMs.

The application and EMA review

In September 2024, Prilenia submitted a marketing authorization application (MAA) to the EMA for Nurzigma, the brand name under which pridopidine was submitted for approval. A marketing authorization is the European equivalent of FDA approval in the U.S., granting a company the right to commercially sell a drug across European Union member states.

The EMA’s Committee for Medicinal Products for Human Use (CHMP), who are the expert panel responsible for evaluating new medicines, conducted a full assessment. That evaluation concluded in July 2025, when the CHMP recommended refusing marketing authorization. 

The agency found that neither the main PROOF-HD trial nor the subgroup analysis had sufficiently demonstrated effectiveness, and that the drug did not meet the criteria for conditional marketing authorization, which is a lower-bar pathway designed for medicines targeting rare diseases with unmet need and preliminary evidence of benefit. 

Following that recommendation, Prilenia exercised its right to request a re-examination, a standard procedural option available to any applicant.

Withdrawal

On 7 November 2025, Prilenia withdrew the application before that re-examination was completed. 

In its letter to the EMA, included below, the company stated that the withdrawal was based on the need to collect additional clinical data to address the questions raised by the CHMP. The letter also noted that Prilenia reserves the right to submit future applications for pridopidine in HD or other indications.

Why you’re only hearing about this now

HDBuzz is covering this in May 2026, six months after the withdrawal, because Prilenia made no public announcement. We learned of the outcome through happenstance, while reviewing the EMA’s publicly available regulatory records. 

We strongly believe that the HD community deserves to know when a regulatory process concludes, in either direction. So while the withdrawal was not accompanied by a public announcement from Prilenia, that is not uncommon at this stage of a regulatory process. 

However, the absence of a company announcement does mean that the community may not have heard. Ensuring that the HD community has a complete picture of where things stand on the drugs they helped move forward in clinical trials is part of what we do.

What this means

For people currently in clinical trials or compassionate use programs with pridopidine, the withdrawal has no impact; those programs continue unaffected.

For the broader HD community, this outcome is consistent with the full body of evidence from more than fifteen years of clinical testing. The EMA’s independent expert evaluation reached the same conclusion the trial data support: that effectiveness has not yet been demonstrated to the standard required for approval of pridopidine to treat people with HD.

We recognize this is disappointing, particularly for people who felt they benefited from pridopidine during a trial. Those experiences are real. Regulatory approval, however, requires that benefit be demonstrated rigorously across a patient population so that everyone offered a treatment can have confidence in it.

Summary

• Pridopidine (Nurzigma) was submitted to the EMA for European marketing authorization in mid-2024
• The European review board completed its evaluation in July 2025 and recommended refusing approval, finding that neither PROOF-HD nor the subgroup analysis demonstrated effectiveness
• Pridopidine also did not meet criteria for conditional marketing authorization
• Prilenia requested a re-examination, then withdrew the application on November 7, 2025 before that process was completed
• The company cited the need for additional clinical data and reserved the right to reapply in the future
• No public announcement accompanied the withdrawal and HDBuzz learned of it through EMA public records
• People in clinical trials or compassionate use programs are unaffected