Vafidemstat Enters PMS With Safety-Only Data: First-Mover Advantage Meets Pivotal Evidence Gap

EMA Approves Oryzon's HOPE-2 Phase II Study for Phelan-McDermid Syndrome

Oryzon Genomics announced that the European Medicines Agency (EMA) has approved its Clinical Trial Application (CTA) to initiate the HOPE-2 Phase IIa study of vafidemstat for Phelan-McDermid Syndrome (PMS). This single-center, single-arm, open-label study will enroll 12 adult patients to evaluate the safety and tolerability of vafidemstat over 12 weeks, with an optional extension. Secondary objectives include assessing its effect on anger, aggression, and overall disease severity in PMS patients, a severely disabling genetic disorder with no approved pharmacologic treatments.

• The HOPE-2 study is a single-center, single-arm, open-label Phase IIa trial designed to enroll 12 adult patients with Phelan-McDermid Syndrome. The primary objective is to evaluate the safety and tolerability of vafidemstat, administered for 12 weeks, with an investigator-assessed option to continue treatment through week 24 based on clinical benefit. This study aims to address the significant unmet medical need in PMS, a condition currently lacking approved pharmacologic treatments.
• Secondary objectives of the HOPE-2 study focus on assessing vafidemstat's effect on anger and aggression, measured by the Aberrant Behavior Checklist (ABC) Irritability Subscale and the Clinical Global Impression of Severity - Anger and Aggression (CGI-S A/A). Efficacy in treating overall disease in adults with PMS will be measured using the Repetitive Behavior Scale-Revised (RBS-R), the Phelan-McDermid Syndrome Assessment of Severity (PMSA-S), and other ABC subscales including Stereotypic Behaviour, Hyperactivity/Noncompliance, Inappropriate Speech, and Social Withdrawal.
• Vafidemstat is highlighted as the only LSD1 inhibitor in clinical development for Central Nervous System disorders, possessing a potent and unique mechanism of action that modulates transcriptional programs involved in neural plasticity, neuroinflammation, and neuronal excitability. Preclinical findings, including LSD1 inhibition triggering a 'reset' of neuronal transcription and reversing social behavior and aggression phenotypes in SHANK3-deficient mice, support its potential as a promising treatment option for Phelan-McDermid Syndrome.
• The HOPE-2 study, conducted in Spain, is part of Oryzon’s VANDAM project, which falls under the Med4Cure Important Project of Common European Interest (IPCEI) on Health. This initiative has received funding from the Spanish Ministry of Science, Innovation and Universities and the Centre for the Development of Industrial Technology and Innovation (CDTI), supported by the European Union – NextGenerationEU. Oryzon will also collaborate with the Spanish Phelan-McDermid Syndrome Association to support participant identification.

The Urgent Need for New Therapies in Phelan-McDermid Syndrome

Current treatment approaches for Phelan-McDermid Syndrome (PMS) remain largely symptomatic and non-curative, addressing individual manifestations rather than the underlying genetic etiology. The syndrome's phenotypic heterogeneity — driven by deletion size, affected genes beyond SHANK3, and individual clinical variables — complicates the development of standardized therapeutic protocols. Emerging pharmacological and non-pharmacological strategies show promise, but significant gaps persist across multiple domains of care.

• Absence of disease-modifying therapies: No treatments targeting the root cause of PMS — haploinsufficiency of SHANK3 or broader 22q13.3 deletions — are established. Potential therapeutic options under discussion, including risperidone, intranasal insulin, insulin growth factor 1, and oxytocin, remain investigational, with their roles not yet definitively defined in clinical practice.

• Genotype-dependent drug response variability: Pharmacological effects in PMS are highly genotype- and drug-dependent. Screening of risperidone, lithium chloride, carbamazepine, and MPEP in shank3 zebrafish models demonstrated that only risperidone normalized sensory responses, while others had no effect or genotype-specific outcomes — underscoring that treatment responses cannot be generalized across the PMS population without patient stratification.

• Underdiagnosis limiting treatment access: Due to lack of clinical recognition and often insufficient laboratory testing, PMS is under-diagnosed and its true incidence remains unknown. This delays initiation of early intervention programs, occupational therapy, and communication therapies that affected individuals are known to benefit from.

• Communication and speech impairment as a therapeutic target remains underdeveloped: Absence of speech affects 50%–80% of individuals with PMS, and communicative skills in the expressive domain other than spoken language remain understudied. Loss of language and other developmental skills is reported in around 40% of individuals, yet standardized, evidence-based intervention protocols for this population are lacking.

• Lack of standardized neurocognitive assessment tools: PMS presents significant challenges in neurocognitive assessment, particularly for underrepresented populations such as Spanish-speaking adults, due to the absence of standardized diagnostic tools adapted to their needs. Without validated outcome measures, evaluating therapeutic efficacy across clinical trials is substantially hindered.

• Multisystem complexity requiring interdisciplinary management without unified guidelines: PMS is a multi-system disorder encompassing neurological, gastrointestinal, renal, lymphatic, and cardiac involvement, with lymphedema occurring in 10–25% of individuals with deletions. Clinical care must encompass various specialties and therapists, yet coordinated, PMS-specific interdisciplinary management frameworks remain limited.

Vafidemstat's Expanding CNS Pipeline Beyond Phelan-McDermid Syndrome

Vafidemstat (ORY-2001), a brain-penetrant, orally bioavailable, irreversible inhibitor of KDM1A (LSD1) and MAO-B, is being investigated across a range of neuropsychiatric and neurodegenerative indications beyond Phelan-McDermid Syndrome. The REIMAGINE phase IIa basket trial demonstrated statistically significant improvements in agitation/aggression and disease-specific features across three distinct psychiatric disorders, with changes evident within the first 2 weeks of treatment.

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Epigenetic Modulation: A Strategic Move into Phelan-McDermid Syndrome

The European Medicines Agency's (EMA) approval for the HOPE-2 Phase IIa study of vafidemstat in Phelan-McDermid Syndrome (PMS) marks a significant step for Oryzon Genomics and the broader field of neurodevelopmental disorder therapeutics. PMS, a rare genetic condition stemming from SHANK3 gene deletions, currently lacks approved pharmacologic treatments, representing a substantial unmet medical need. Vafidemstat, an inhibitor of the histone lysine-specific demethylase KDM1A (LSD1), operates via an epigenetic mechanism, influencing gene transcription critical for brain function.

This move builds on promising earlier data. Vafidemstat demonstrated good safety and tolerability, central nervous system (CNS) penetration, and target engagement in healthy volunteers. Crucially, the REIMAGINE Phase IIa basket trial showed significant reductions in agitation and aggression, alongside improvements in other neuropsychiatric scales, across patients with borderline personality disorder, ADHD, and autistic spectrum disorder. These findings suggest a broad applicability for vafidemstat in managing challenging behaviors associated with various CNS conditions.

Strategically, targeting PMS positions vafidemstat as a potential first-in-class treatment for an orphan indication, offering significant market potential if successful. This also reinforces a platform approach, where the drug's epigenetic mechanism could address a spectrum of neurodevelopmental and psychiatric disorders. The prior psychometric characterization of PMS patients, aimed at identifying optimal endpoints, underscores a commitment to precision medicine, which could streamline future clinical development.

However, the path forward is not without challenges. The HOPE-2 study's single-center, single-arm, open-label design, with only 12 adult patients, means initial efficacy signals will require careful interpretation and further validation in larger, controlled trials. The specific and complex phenotypic presentation of PMS, including intellectual disability and speech delay, may respond differently than the aggression observed in other neurodevelopmental disorders. Ensuring that the chosen endpoints truly capture clinically meaningful improvements for PMS patients will be paramount. Nevertheless, this CTA represents a crucial advancement in exploring epigenetic modulation for a severely debilitating genetic disorder.