Authorization to start PRECISE-HD in participating EU Member States extends a global randomized double-blind placebo-controlled program toward approximately 400 participants across upwards of 31 sites in nine EU countries plus US, UK and Canada to test oral pridopidine 45 mg twice daily on disease progression, functional capacity, motor, cognition, speech and quality of life. [1] The renewal follows PROOF-HD in 499 participants where change in total functional capacity was -0.18 and composite UHDRS was -0.11 versus placebo with no separation, MermaiHD where modified motor score did not demonstrate efficacy, and PRIDE-HD in 408 participants where total motor score did not separate, leaving efficacy resting on post-hoc early-HD total functional capacity benefit of 0.87 overall and 1.16 in HD1/HD2 and an antidopaminergic-free sensitivity pattern. [2][3] Mechanistically distinct symptomatic peers including tetrabenazine, deutetrabenazine with quality-of-life effect, riluzole and rivastigmine cannot validate sigma-1 agonism and no closely comparable precedent exists for a selective sigma-1 agonist in Huntington's disease, so no approval, rejection or HTA decision anchors probability. [4] Tolerability at 45 mg twice daily was placebo-like in 1067 integrated patients with QTc effect of 6.6 ms and long exposure to 6.5 years, but higher doses increased adverse events. [5][6] No ICER or HTA outcome is stated, leaving value tied to unproven functional preservation and confirmatory success dependent on enrichment and confound control.
PROOF-HD overall TFC and cUHDRS missed while 45 mg bid safety held; benefit rests on post-hoc early-HD and ADM-free subgroups. [3]
| Indication | Huntington's disease |
| Drug | pridopidine |
| Mechanism of Action | sigma-1 receptor (S1R) agonist |
| Company | Prilenia Therapeutics B.V. |
| Trial Phase | Phase 3 |
| Trial Acronym | PRECISE-HD |
| NCT ID | NCT07609108 |
| Category | Clinical Trial Event |
| Sub Category | Trial Initiation / First Patient In (FPI) |
| Therapeutic Area | Neuroscience |
| Partner Company | Ferrer |
| Study Population | People living with Huntington’s disease (HD), from early to mid-stage disease (TFC 7-13) |
| Participant Size | Approximately 400 participants |
| Study Design | Randomized, double-blind, placebo-controlled |
| Primary Endpoint | Change from baseline to Week 52 in the combined Unified Huntington’s Disease Rating Scale (cUHDRS) score |
| Study Stages | 52-week placebo-controlled stage, 104-week open-label extension stage |
| Recruitment Regions | EU, US, UK, Canada |
| Regulatory Designations | Orphan Drug Designation (US and EU for HD and ALS), FDA Fast Track designation (US for HD) |
| Conference Name | European Huntington’s Disease Network (EHDN) Clinical Research Congress 2026 |
| Conference Date | October 22–24, 2026 |
EU Authorizes Prilenia and Ferrer's Confirmatory PRECISE-HD Study
Prilenia Therapeutics B.V. and Ferrer announced that their confirmatory Phase 3 PRECISE-HD study of investigational pridopidine for Huntington's disease (HD) has received authorization to commence in participating EU Member States. Recruitment is expected to begin this month across upwards of 31 sites in nine EU countries, joining ongoing enrollment in the US and UK, with Canada to follow. The global, randomized, double-blind, placebo-controlled study aims to enroll approximately 400 participants to evaluate the efficacy and safety of oral pridopidine on disease progression, functional capacity, motor function, cognition, speech, and quality of life in HD patients. This milestone builds on previous research and seeks to generate robust data for regulatory evaluation.
- The confirmatory Phase 3 PRECISE-HD study for pridopidine in Huntington's disease has secured authorization to begin in EU Member States, with recruitment starting this month across 31 sites in nine countries. This expands the global trial, which is already enrolling participants in the US and UK, and will soon include Canada, aiming for a total of approximately 400 participants.
- The PRECISE-HD study is a global, randomized, double-blind, placebo-controlled trial designed to assess pridopidine's efficacy and safety in people living with HD, from early to mid-stage disease (TFC 7-13). It will evaluate clinical effects on disease progression, functional capacity, motor function, cognition, speech, and quality of life. The primary endpoint is the change from baseline to Week 52 in the combined Unified Huntington’s Disease Rating Scale (cUHDRS) score.
- Pridopidine is an investigational, highly selective, oral sigma-1 receptor (S1R) agonist, a mechanism shown to stimulate neuroprotective pathways impaired in neurodegenerative diseases. It has demonstrated a generally favorable safety and tolerability profile in over 1,600 people, with some receiving treatment for up to seven years. The drug holds Orphan Drug Designation in the US and EU for HD and ALS, and FDA Fast Track designation in the US for HD.
Addressing the Unmet Need in Huntington's Disease Treatment
Current treatment for Huntington's disease (HD) remains symptomatic, with no disease-modifying treatment available and clinical practice largely based on expert opinions as well as evidence and/or experience of treating similar symptoms in other conditions. Only two drugs are approved by the US Food and Drug Association for the treatment of HD, the dopamine-depleting drugs tetrabenazine and deutetrabenazine that both target motor symptoms, while pharmacotherapies primarily target motor symptoms and cholinergic modulators address cognitive decline.
Lack of disease modification with persistent progression: Available pharmacologic drugs offer significant symptom relief and improve quality of life but do not modify disease course; with stable deutetrabenazine dosing from weeks 8-145 total maximal chorea scores showed minimal change but total motor score increased versus week 8 (mean change [standard deviation]: 8.2 [11.9]), and sensitive and dynamic response biomarkers are still needed to assess efficacy of mutant huntingtin (mHTT)-lowering candidate therapies.
Limited efficacy breadth and heterogeneous evidence base: Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score (TMS) was improved with dopaminergics (tetrabenazine, deutetrabenazine, and pridopidine) and glutamatergic (riluzole) drugs, yet only pridopidine treatment exhibited efficacy on UHDRS Total Functional Capacity (TFC), deutetrabenazine proved effective for quality of life (QoL), and tetrabenazine improved Stroop Color and Word test while rivastigmine improved verbal fluency; due to substantial heterogeneity results were synthesized descriptively, and evidence of antipsychotics effect on disease progression is limited with no comparative study.
Significant tolerability and safety burden requiring monitoring: Tetrabenazine acts by reversibly inhibiting vesicle monoamine transporter type 2 and depleting serotonin, norepinephrine, and dopamine, and is associated with parkinsonism, other extrapyramidal symptoms (particularly akathisia), depression and suicidality, neuroleptic malignant syndrome, and sedation, with a black box warning for increasing risk of depression and suicidality; long-term deutetrabenazine common adverse events included somnolence, depression, anxiety, insomnia, and akathisia, with adverse events of interest including suicidality and parkinsonism, and tetrabenazine dosing is based in part on genotyping for CYP2D6 metabolizer status with interactions with inhibitors and inducers of cytochrome P450 (CYP) 2D6, reserpine, and lithium.
Differential functional, cognitive, and psychiatric outcomes and discontinuations: Functional decline was lower in the dibenzodiazepine group than other antipsychotic groups (Total Functional Capacity: 0.41 ± 0.17 units per year vs. risperidone and 0.54 ± 0.19 vs. tetrabenazine), benzamides were less effective than other antipsychotics on cognitive evolution (Stroop interference, Stroop color and Literal fluency), documented treatment discontinuation due to adverse effects was less frequent in tiapride courses than in tetrabenazine courses (27% vs 55%; P = 0.005) with fatigue and apathy most common with tiapride and mood-related adverse events more frequently recorded with tetrabenazine, and only 54.9% of participants with moderate to severe depression used antidepressants.
Complex neuropsychiatric comorbidity and diagnostic overlap: Overlapping psychomotor and behavioral features make diagnosis of HD with concomitant catatonia challenging, all catatonia cases received lorazepam with variable responses and electroconvulsive therapy (ECT) yielding partial or complete relief in most though recurrence was frequently observed with one requiring maintenance ECT and another worsened, antipsychotics were inconsistently used and sometimes exacerbated symptoms with evidence to suggest antipsychotics with strong dopamine antagonism should be used cautiously, and individuals with HD who present with irritability may be managed with antidepressants and antipsychotics but they are often not sufficient.
Unpacking the PRECISE-HD Study Design for Pridopidine
Key Huntington's disease trials span randomised, double-blind, placebo-controlled designs and open-label extensions, evaluating symptomatic and safety outcomes over 10 weeks to 36 months. Interventions include VMAT2 inhibitors, dopaminergic stabilizers, and repurposed agents, with primary endpoints anchored to Unified Huntington's Disease Rating Scale motor and chorea scores, tolerability, and neuropsychiatric scales.
| Trial | Design and Duration | Population | Intervention | Primary Endpoint |
|---|---|---|---|---|
| PBT2 phase 2 (NCT01590888) | 26-week, randomised, double-blind, placebo-controlled trial | adults (≥25 years old) with early-stage to mid-stage Huntington's disease | once daily PBT2 250 mg, PBT2 100 mg, or placebo | safety and tolerability |
| TREND-HD ethyl-EPA (NCT00146211) | Six-month multicenter, randomized, double-blind, placebo-controlled trial followed by a 6-month open-label phase | Three hundred sixteen adults with Huntington disease | placebo or ethyl-EPA, 1 g twice a day | Six-month change in the Total Motor Score 4 component of the Unified Huntington's Disease Rating Scale |
| Pridopidine dose-ranging trial | randomized, double-blind, placebo-controlled trial for 12 weeks | Two hundred twenty-seven subjects enrolled | pridopidine, either 20 (n=56), 45 (n=55), or 90 (n=58) mg daily for 12 weeks or matching placebo (n=58) | change from baseline to week 12 in the Modified Motor Score, a subset of the Unified Huntington's Disease Rating Scale Total Motor Score |
| KINECT-HD valbenazine (NCT04102579) | phase 3, randomised, double-blind, placebo-controlled trial for 12 weeks of double-blinded treatment | adults with genetically confirmed Huntington's disease and chorea (Unified Huntington's Disease Rating Scale [UHDRS] Total Maximal Chorea [TMC] score of 8 or higher) | oral placebo or valbenazine (≤80 mg, as tolerated) | least-squares mean change in UHDRS TMC score from the screening and baseline period (based on the average of screening and baseline values for each participant) to the maintenance period (based on the average of week 10 and 12 values for each participant) |
| Deutetrabenazine open-label extension (NCT01897896) | open-label, single-arm, multi-center study | Of 119 patients (Rollover, n = 82; Switch, n = 37) | deutetrabenazine; Mean dose at week 8 was 38.1 mg (Rollover) and 36.5 mg (Switch) | evaluate the long-term safety and tolerability of deutetrabenazine for the treatment of Huntington disease |
| Latrepirdine trial | Double-blind, randomized, placebo-controlled trial for a 90-day treatment period | Ninety-one participants with mild to moderate HD enrolled at 17 US and UK centers | Latrepirdine, 20 mg 3 times daily (n = 46), or matching placebo (n = 45) | tolerability, defined as the ability to complete the study at the assigned drug dosage |
| Bupropion for apathy trial | phase 2b multicentre, double-blind, placebo-controlled crossover trial for 10 weeks | individuals with HD and clinical signs of apathy according to the Structured Clinical Interview for Apathy-Dementia (SCIA-D), but not depression (n = 40) | bupropion 150/300mg or placebo daily | significant change of the Apathy Evaluation Scale (AES) score after ten weeks of treatment as judged by an informant (AES-I) |
| Sativex pilot (NCT01502046) | double-blind, randomized, placebo-controlled, cross-over pilot clinical trial for 12 weeks | Twenty-six patients were randomized and 24 completed the trial | Both Sativex(®) and placebo were dispensed as an oral spray, to be administered up to 12 sprays/day | safety, assessed by the absence of more severe adverse events (SAE) and no greater deterioration of motor, cognitive, behavioral and functional scales during the phase of active treatment |
Pridopidine's Sigma-1 Receptor Agonism and Safety Profile
Pridopidine was well tolerated with an adverse event profile comparable to placebo in Huntington's disease (HD) in pooled and meta-analytic data. A systematic review and meta-analysis of 4 randomized controlled trials with 1130 patients (816 in the pridopidine group and 314 in the placebo group) reported overall adverse events (risk ratio [RR], 1.03; 95% confidence interval [CI], 0.94-1.13; P = 0.09 [sic P = 0.49]) and serious adverse events (RR, 1.62; 95% CI, 0.88-2.99; P = 0.12). A second meta-analysis pooling 1,119 patients across four RCTs reported adverse events (RR 1.06, 95% CI = 0.96 to 1.16, p = 0.24), and a systematic review of dopamine stabilizers reported total adverse events (RR 1.05, 95% CI 0.92 to 1.20). An integrated safety analysis of pooled data from 1067 patients with HD enrolled in four double-blind, placebo-controlled studies found an adverse event profile comparable to that of placebo with no significant differences when analyzed by age, sex, baseline total functional capacity (TFC), cytosine-adenine-guanine (CAG) repeat length, use of antidopaminergic medications (ADMs), and region, with no new safety signals in a larger sample and characterization in approximately 1600 participants across multiple studies.
Long-term and cardiac safety data in HD support continued tolerability at the recommended human dose of 45 mg twice daily (bid), with dose-related increases at higher doses. Concentration-QTc analysis from PRIDE-HD in 402 patients showed a slope of 0.012 ms per ng/mL (90% CI, 0.0109-0.0127), with predicted placebo-corrected change from baseline in the Fridericia-corrected QT interval of 6.6 ms (upper bound 90% CI, 8.0 ms) at 45 mg bid, below the level of concern and not clinically relevant, with cardiac-related adverse event frequencies similar to placebo, no patients reaching a QTcF of 500 ms and no torsade de pointes at any dose. In the 1-year MermaiHD open-label extension, 353 of 386 randomized controlled trial completers entered and 305 (86.4%) completed, with at least 1 adverse event in 79.6% [n = 90/113] for placebo, 80.8% [n = 101/125] for 45 mg/day and 82.6% [n = 95/115] for 90 mg/day, and at least 1 serious adverse event in 8.0% [n = 9/113], 12.8% [n = 16/125], and 8.7% [n = 10/115], respectively, with falls and worsening of chorea most commonly reported and no clinically meaningful changes in laboratory parameters or EKG-related safety concerns. Open-HART with pridopidine 45 mg BID remained safe and tolerable over 36 months with 89% reporting at least one adverse event and 30% treatment-related events, most commonly falls (12.7%), anxiety (9.3%), insomnia (8.5%), irritability (6.8%), and depression (5.9%), two seizures, no arrhythmias or suicide attempts, and five deaths considered treatment unrelated, and remained safe and well tolerated at 48 and 60 months and up to 6.5 years in open-label extension studies. In PRIDE-HD with pridopidine 45, 67.5, 90, or 112.5 mg twice daily for 52 weeks, the most frequent adverse events were diarrhoea, vomiting, nasopharyngitis, falls, headache, insomnia, and anxiety, the most common treatment-related events were insomnia, diarrhoea, nausea, and dizziness, and serious adverse events occurred in pridopidine groups only as falls (n=5), suicide attempt (n=4), suicidal ideation (n=3), head injury (n=3), and aspiration pneumonia (n=3), with one death in the 112.5 mg group due to aspiration pneumonia considered possibly related. Pridopidine at 90 mg/day showed an adverse event profile similar to placebo in MermaiHD, while meta-analytic subgroup data showed pridopidine at doses at or above 90 mg/day increased total adverse events (RR 1.11, 95% CI = 1.00 to 1.22, p = 0.04) with nasopharyngitis and insomnia.
In amyotrophic lateral sclerosis (ALS), pridopidine 45 mg twice daily for 24 weeks showed a safety profile comparable to placebo. In the HEALEY ALS Platform Trial regimen with a safety dataset of pridopidine (n = 121) and placebo (n = 163), the most common adverse events were falls (28.1% vs 29.3%, respectively) and muscular weakness (24.0% vs 31.7%, respectively), with no impact on ALS progression for the primary disease rate ratio of 0.99 [95% credible interval, 0.80-1.21]. Exploratory subgroup analysis in definite/probable ALS with early disease described pridopidine as well-tolerated with a safety profile comparable to placebo.
Pridopidine's Global Phase 3: A Critical Juncture for HD Treatment
The launch of the global confirmatory Phase 3 PRECISE-HD study for pridopidine represents a significant development for the Huntington's disease (HD) community, a patient population grappling with a progressive, debilitating neurodegenerative disorder for which no disease-modifying treatments currently exist. This trial aims to definitively assess pridopidine's potential to slow or halt disease progression, building on extensive preclinical and clinical research.
Pridopidine's mechanism of action, primarily as a highly selective sigma-1 receptor (S1R) agonist, offers a unique approach. Research indicates that S1R activation plays a crucial role in neuronal survival and function, modulating pathways involved in calcium signaling, mitochondrial health, ER stress, and the transport of brain-derived neurotrophic factor (BDNF). These neuroprotective effects, observed in various HD models, suggest pridopidine could offer more than just symptomatic relief, potentially addressing the underlying pathology of HD.
However, the path to this confirmatory trial has not been without challenges. Earlier Phase 2/3 studies, including MermaiHD, HART, and PRIDE-HD, did not consistently meet their primary motor efficacy endpoints. PRIDE-HD, in particular, failed to replicate previous secondary motor benefits and highlighted the potential for a strong placebo effect in HD trials. This history underscores the critical need for the robust, global design of PRECISE-HD, which aims to enroll approximately 400 participants and evaluate a broad spectrum of endpoints.
The study's comprehensive endpoint assessment, encompassing functional capacity, motor function, cognition, speech, and quality of life, reflects an evolving understanding of HD's multifaceted impact. While traditional measures like the Total Functional Capacity (TFC) scale have been used, studies suggest its limitations, especially in early-stage disease. The inclusion of measures like speech, which is emerging as a sensitive digital biomarker for early detection and monitoring, indicates a forward-thinking approach to capturing holistic patient benefit.
From a safety perspective, pridopidine at its recommended dose of 45 mg twice daily has generally been well-tolerated, with an adverse event profile comparable to placebo in pooled analyses. Long-term open-label extension studies have also shown no new safety concerns over several years. However, a meta-analysis did suggest that higher doses (≥90 mg/day) might be associated with an increase in certain adverse events, a factor that could influence future dosing strategies if higher efficacy is linked to higher doses.
Ultimately, the success of PRECISE-HD could mark a paradigm shift in HD treatment, offering a much-needed disease-modifying option. For Prilenia and Ferrer, a positive outcome would solidify their position in the rare disease market and validate the S1R agonist strategy, potentially opening doors for pridopidine in other neurodegenerative conditions. The stakes are high, not just for the companies, but for the thousands of individuals living with Huntington's disease worldwide.
Frequently Asked Questions
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