Prilenia Withdraws European Application for Huntington's Disease Drug Pridopidine After Regulatory Rejection
Key Insights
Prilenia Therapeutics (search) withdrew its European marketing application for pridopidine (Nurzigma (search)) in November 2025 after the EMA's expert committee recommended refusing approval for Huntington's disease (search) treatment.
The EMA found that neither the main PROOF-HD trial nor subgroup analyses sufficiently demonstrated effectiveness, with the drug failing to meet criteria for conditional marketing authorization despite targeting a rare disease with unmet medical need.
Despite the regulatory setback, Prilenia announced a data sharing agreement with CHDI Foundation (search) to donate clinical trial datasets from placebo arms of PRIDE and PROOF studies to advance future Huntington's disease (search) research.
Prilenia Therapeutics (search) has withdrawn its European marketing application for pridopidine (Nurzigma (search)) following a regulatory rejection, marking another setback for the experimental Huntington's disease (search) treatment that has failed to meet primary endpoints across multiple clinical trials over fifteen years of development.
The European Medicines Agency (search)'s Committee for Medicinal Products for Human Use concluded its evaluation in July 2025, recommending refusal of marketing authorization after finding that neither the main PROOF-HD trial nor subgroup analyses had sufficiently demonstrated effectiveness. The drug also failed to meet criteria for conditional marketing authorization, a lower-bar pathway designed for medicines targeting rare diseases with unmet medical need.
Regulatory Timeline and Withdrawal
Prilenia submitted the marketing authorization application in September 2024, seeking approval specifically for adults with early Huntington's disease (search) who were not taking antidopaminergic medications. The application was based on a subgroup analysis from the PROOF-HD trial, focusing on participants not using drugs like tetrabenazine or risperidone commonly prescribed for chorea and behavioral symptoms.
Following the CHMP's negative recommendation, Prilenia exercised its right to request a re-examination but ultimately withdrew the application on November 7, 2025, before the process was completed. In its withdrawal letter to the EMA, the company stated the decision was based on the need to collect additional clinical data to address regulatory questions.
The withdrawal received no public announcement from Prilenia, with the HD community learning of the outcome through regulatory records review six months later.
Clinical Development History
Pridopidine's journey through Huntington's disease (search) research spans four major clinical trials—MermaiHD, HART, PRIDE-HD, and PROOF-HD—none of which met their primary endpoints. The PROOF-HD study, published in Nature Medicine, involved 499 participants and served as the basis for the European application through its subgroup analysis of patients not taking antidopaminergic medications, representing fewer than half of the original trial participants.
Data Sharing Initiative
Despite the regulatory setback, Prilenia announced a Data Use Agreement with CHDI Foundation (search) to advance Huntington's disease (search) research. Under the agreement, Prilenia will provide clinical data from the placebo arms of its PRIDE and PROOF studies to help researchers better understand placebo-related effects in clinical trial outcomes.
"Collaboration which balances scientific rigor with data openness is an ethical and scientific imperative," said Dr. Michael R. Hayden, Prilenia's Chief Executive Officer. "Sharing data is key to accelerating and advancing knowledge and understanding and accelerates progress aimed at the development of much needed treatments capable of diminishing the effect of intractable diseases such as HD."
Robi Blumenstein, president of CHDI Management, noted that the data donation "will help us better understand how placebo-related effects influence clinical trial outcomes, which could improve the design and interpretation of future trials and ultimately support the development of more effective approaches to slow the progression of this devastating disease."
Future Development Plans
Prilenia retains ownership of the underlying clinical data and reserves the right to submit future applications for pridopidine in HD or other indications. The company plans a potential registrational Phase 3 study of pridopidine in early to mid-stage Huntington's disease (search), scheduled to commence in the second quarter of 2026.
For patients currently participating in clinical trials or compassionate use programs with pridopidine, the withdrawal has no impact, with those programs continuing unaffected.
Disease Context
Huntington's disease (search) affects an estimated 100,000 people worldwide, with an additional 300,000 at risk of developing the inherited neurodegenerative disorder. The disease typically manifests between ages 30 and 50, progressing slowly over 15 to 20 years with patients gradually losing their ability to work, communicate, and manage daily activities.
Currently available treatments focus solely on symptomatic relief and palliative care, with no approved therapies impacting overall disease progression. The EMA's evaluation concluded that effectiveness has not yet been demonstrated to the standard required for regulatory approval, consistent with the full body of evidence from more than fifteen years of clinical testing.