Vistagen Secures FDA “Study May Proceed” Clearance for Refisolone IND, Advancing Phase 2 Development in Menopause-Related Vasomotor Symptoms
Vistagen (Nasdaq: VTGN), a late clinical-stage biopharmaceutical company focused on advancing neuroscience through its proprietary nose-to-brain neurocircuitry platform, has announced a key regulatory milestone for its women’s health pipeline. The company has received a “Study May Proceed” letter from the U.S. Food and Drug Administration under its U.S. Investigational New Drug (IND) application for refisolone nasal spray, enabling further Phase 2 clinical development in the United States.
Refisolone is a novel, non-hormonal and non-systemic investigational therapy being developed to treat moderate to severe vasomotor symptoms (VMS), commonly known as hot flashes, associated with menopause. The FDA’s clearance marks an important step in expanding clinical research efforts for a condition that affects a large proportion of women but still lacks sufficient non-hormonal treatment options.
Addressing a widespread unmet need in women’s health
Menopausal vasomotor symptoms are among the most common and disruptive experiences during the menopausal transition. It is estimated that approximately 75% of women in the United States experience hot flashes, often accompanied by night sweats, sleep disturbances, and reduced quality of life. While hormone replacement therapy has traditionally been used to manage these symptoms, it is not suitable for all patients due to contraindications or personal preferences, creating a clear need for alternative therapies.
Vistagen’s refisolone aims to address this gap by offering a fast-acting, intranasal option that does not rely on systemic hormone modulation. The therapy is part of the company’s broader portfolio of investigational products known as “pherines,” which are designed to engage specific neural pathways via the nasal cavity and rapidly influence brain circuits involved in emotional and physiological responses.
By leveraging this nose-to-brain delivery approach, refisolone is intended to provide symptom relief without the systemic exposure typically associated with oral or injectable therapies. This mechanism could potentially reduce safety concerns and improve tolerability, particularly for patients who are unable or unwilling to use hormone-based treatments.
Building on promising early-stage clinical data
The FDA’s decision to allow the study to proceed in the United States builds on previously generated clinical data from exploratory Phase 2a trials conducted in Mexico. These studies were carried out by Pherin Pharmaceuticals, now a wholly owned subsidiary of Vistagen, and provided early evidence supporting the safety and efficacy of refisolone in treating menopausal hot flashes.
In one randomized, double-blind, placebo-controlled Phase 2a trial involving 36 menopausal women experiencing at least eight hot flashes per day, participants received intranasal refisolone at a dose of 3.2 micrograms, administered as needed up to five times daily over a four-week period. The study was designed to evaluate both the frequency and severity of hot flashes, as well as overall tolerability.
The results demonstrated a statistically significant reduction in both key endpoints among patients treated with refisolone compared to those receiving placebo. Specifically, the frequency of hot flashes was reduced by approximately 80% in the treatment group, compared to a 36% reduction in the placebo group. This difference was highly significant, indicating a strong therapeutic effect.
Importantly, the reduction in hot flash frequency was observed as early as one week into treatment, suggesting a rapid onset of action—an attribute that could be particularly valuable for patients seeking immediate symptom relief. In addition to reducing frequency, refisolone also improved the severity of hot flashes, further enhancing its potential clinical benefit.
Favorable safety and tolerability profile
Safety is a critical consideration in the development of therapies for menopausal symptoms, particularly given the long-term nature of treatment in many cases. In the Phase 2a study, refisolone was generally well tolerated, with no serious drug-related adverse events reported. This favorable safety profile aligns with the therapy’s non-systemic design, which aims to minimize systemic exposure and associated risks.
The absence of significant safety concerns in early-stage trials provides a strong foundation for advancing refisolone into further clinical development. As the program moves forward, larger and more comprehensive studies will be needed to confirm these findings and further characterize the therapy’s safety and efficacy.
Advancing clinical development in the United States
The FDA’s “Study May Proceed” letter represents a critical regulatory milestone, allowing Vistagen to initiate additional Phase 2 trials in the United States. These studies are expected to build on the exploratory data generated to date and further evaluate refisolone’s potential as a treatment for moderate to severe vasomotor symptoms.
Shawn Singh, President and Chief Executive Officer of Vistagen, highlighted the significance of this development, noting that it marks meaningful progress in the company’s women’s health program. He emphasized the substantial unmet need for new treatment options and pointed to the encouraging Phase 2a data as evidence of refisolone’s potential to deliver a fast-acting, non-hormonal solution for millions of women.
A novel approach through nose-to-brain neurocircuitry
Vistagen’s broader scientific strategy centers on its proprietary understanding of nose-to-brain neurocircuitry. This approach focuses on targeting neural pathways directly through the nasal cavity, bypassing traditional systemic circulation and enabling rapid modulation of brain activity.
The company’s pherine platform represents a new class of investigational therapeutics designed to influence neurocircuitry involved in conditions ranging from anxiety and depression to menopausal symptoms. By applying this technology to women’s health, Vistagen is exploring a differentiated pathway for addressing symptoms that have historically been managed through hormonal interventions.
As Vistagen prepares to advance refisolone into additional Phase 2 trials in the United States, the company is positioning itself at the forefront of innovation in non-hormonal menopause treatments. If future studies confirm the promising results seen in early trials, refisolone could emerge as a valuable new option for women seeking safe, effective, and convenient relief from hot flashes.
The regulatory clearance from the FDA not only validates the company’s development strategy but also underscores the growing recognition of the need for diverse treatment approaches in women’s health. With continued clinical progress, refisolone has the potential to reshape the treatment landscape for menopausal vasomotor symptoms and improve quality of life for millions of women worldwide.
About Refisolone Nasal Spray
Refisolone (PH80) nasal spray is a clinical-stage investigational pherine with a novel proposed mechanism of action and potential to treat multiple women’s health disorders. Refisolone is fundamentally differentiated from other investigational product candidates, as well as the FDA-approved treatments, for moderate to severe vasomotor symptoms (hot flashes) due to menopause.
It is designed as a potential on-demand, fast-acting, non-hormonal, and non-systemically absorbed treatment, potentially without certain drug-related adverse events or hormone-related safety signals associated with current FDA-approved treatment options. Refisolone is administered intranasally at microgram-level doses to rapidly activate chemosensory neurons in the nasal cavity, which engage olfactory–limbic and olfactory–hypothalamic pathways that modulate anxiety and thermoregulatory neural circuits.
About Vistagen
Vistagen (Nasdaq: VTGN) is a late clinical-stage biopharmaceutical company leveraging a deep understanding of nose-to-brain neurocircuitry to develop and commercialize a new class of rapid-onset neurocircuitry-focused intranasal product candidates called pherines. Vistagen’s pherine product candidates are designed to achieve therapeutic benefits without requiring absorption into the blood or uptake into the brain, giving them the potential to be a safer alternative to other pharmacological options, if successfully developed and approved.
Vistagen’s pherine pipeline currently consists of five clinical-stage investigational product candidates focused on improving the current standard of care for multiple highly prevalent indications, including social anxiety disorder, major depressive disorder, and vasomotor symptoms (hot flashes) due to menopause.
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