Vistagen Plans New Phase 3 Approach for Fasedienol After FDA Meeting

Vistagen has announced a regulatory update following a Type C meeting with the U.S. Food and Drug Administration (FDA) on the future Phase 3 development of fasedienol, its lead investigational nasal spray for social anxiety disorder (SAD). The announcement, made on November 9, 2026, follows the company’s June 2026 PALISADE-4 trial (NCT06615557), which did not meet its primary endpoint.

According to the company, the FDA provided constructive feedback on using the Liebowitz Social Anxiety Scale (LSAS) as the primary endpoint in a future Phase 3 study in adults, along with additional assessments to determine the drug’s acute effects.

Vistagen now plans to submit a revised protocol to the FDA, incorporating interim assessments using electronic diaries (eDiaries) and qualitative patient surveys into the proposed study design. The updated approach is expected to evaluate fasedienol’s potential in a broader patient population rather than limiting its development to acute anxiety associated with specific situations.

FDA Feedback Shapes the Revised Phase 3 Development Strategy

During the Type C meeting, Vistagen discussed potential registration-directed development pathways for fasedienol with the FDA.

The main proposal involved using LSAS as the primary endpoint in a future Phase 3 study. The assessment evaluates two aspects of social anxiety: fear or anxiety and avoidance across different social interaction and performance situations.

The FDA’s feedback also addressed the importance of interim assessments to determine whether acute symptom relief could translate into longer-term functional improvement.

To address this, Vistagen plans to incorporate two additional patient-assessment methods:

• Electronic diaries (eDiaries): Intended to capture patients’ experiences and changes in anxiety symptoms during everyday social and performance situations between scheduled clinical assessments.
• Qualitative patient surveys: Intended to provide additional insight into patients’ perceptions of symptom changes, avoidance behaviour and their ability to participate in everyday activities.

The company also reported that the FDA acknowledged fasedienol’s reported safety profile and its potential to benefit a broad population of patients with SAD.

Based on the regulatory feedback, Vistagen plans to pursue development for the overall treatment of social anxiety disorder rather than focusing exclusively on acute anxiety associated with specific situations.

PALISADE-4 Phase 3 Trial: Primary Endpoint Not Achieved

PALISADE-4 was a Phase 3, randomised, double-blind, placebo-controlled trial that evaluated a single dose of intranasal fasedienol in adults with social anxiety disorder.

The study involved 238 participants and used a simulated public-speaking challenge to assess the drug’s potential to reduce acute anxiety symptoms.

Its primary endpoint was the change from baseline in the Subjective Units of Distress Scale (SUDS), which measures the intensity of subjective distress experienced during anxiety-provoking situations.

Topline results announced on June 30, 2026, showed that fasedienol did not achieve a statistically significant improvement over placebo in the overall study population.

The least-squares mean change in SUDS score was:

• Fasedienol group: -9.5
• Placebo group: -11.4
• Between-group difference: 1.9 (p=0.427)

The trial also failed to demonstrate treatment differences on its secondary endpoints.

However, a post-hoc analysis involving 123 participants with very severe social anxiety, defined by a baseline LSAS score of at least 95, showed a nominally statistically significant improvement in the primary endpoint. The least-squares mean change in SUDS was -12.8 with fasedienol compared with -3.7 with placebo, representing a between-group difference of -9.1 (p=0.036).

These subgroup findings are exploratory and require confirmation in appropriately designed prospective studies. They cannot independently establish treatment efficacy.

Despite the lack of efficacy demonstrated on the primary endpoint, the company reported favourable safety and tolerability findings consistent with earlier clinical trials.

Fasedienol Targets Social Anxiety Through an Intranasal Pherine Approach

Fasedienol, also known as PH94B, is an investigational intranasal drug candidate developed by Vistagen as part of its pherine platform.

The compound is designed to act through nasal chemosensory pathways and associated neurocircuitry. According to the company’s proposed mechanism, fasedienol has the potential to produce rapid therapeutic effects without requiring systemic absorption into the bloodstream or uptake into the brain.

Clinical Context of Revised Phase 3 Programme

Following the PALISADE-4 results, Vistagen is considering a revised approach to evaluate fasedienol in patients with social anxiety disorder. The proposed Phase 3 study will use LSAS as its primary endpoint, allowing researchers to assess both fear or anxiety and avoidance across different social and performance situations.

The revised study design is also expected to include eDiaries and qualitative patient surveys. These assessments could help researchers understand how patients experience changes in their symptoms between clinical visits and whether treatment makes it easier for them to participate in everyday social activities.

In September 2026, Vistagen also reported preliminary findings from the open-label extension of PALISADE-4. The company reported a mean improvement of 31.4 points in LSAS scores at Month 4 among participants with available assessments. Improvements were also observed in the fear/anxiety and avoidance subscales. However, these findings were exploratory, as the extension was open-label and did not include a concurrent placebo-controlled comparison. They cannot establish treatment efficacy.

Unlike PALISADE-4, which focused on anxiety during a simulated public-speaking challenge, the proposed approach aims to examine the potential benefits of fasedienol across a broader range of social situations.

Vistagen plans to submit the revised protocol to the FDA. However, details such as study duration, sample size, dosing schedule and endpoint hierarchy have not yet been disclosed. Further clinical evidence will be needed to determine whether the proposed approach can demonstrate meaningful improvements in social anxiety and everyday functioning.

Reference

Vistagen Provides Regulatory Update Following Productive Type C Meeting with U.S. FDA on Phase 3 Development of Fasedienol for Social Anxiety Disorder, Vistagen, 09 November 2026