FDA says "study may proceed" for Vistagen's refisolone nasal spray for vasomotor symptoms

Vistagen’s refisolone nasal spray, in development to treat moderate-to-severe vasomotor symptoms because of menopause, got a green light for continued phase 2 clinical development after receipt of a “Study May Proceed” letter from the FDA.¹

According to an announcement from the biopharmaceutical company, the process will continue in the United States under an Investigational New Drug Application for the company’s non-hormonal, non-systemic product candidate.

The continuation comes after refisolone demonstrated improvements vs placebo in frequency and severity of daily menopausal hot flashes.

In an exploratory randomized, double-blind, placebo-controlled phase 2a trial among menopausal women (n = 36) with 8 or more daily hot flashes, refisoloe was delivered intranasally at a 3.2 μg, as needed, up to 5 times daily for 4 weeks.

Among 18 people in the refisolone group, “statistically significant improvements versus placebo (n=18) in both the frequency and severity of daily menopausal hot flashes, with hot flash frequency reduced by 80% in refisolone-treated patients compared to 36% in the placebo group,” were observed according to Vistagen.

Further, a reduction in the frequency of vasomotor symptoms was observed as early as 1 week in the refisolone population ( P < 0..1). No serious drug-related adverse events were recorded, and Vistigen reported that the investigational nasal spray was well-tolerated in the study. The study was originally conducted by Pherin Pharmaceuticals in Mexico, which is now a wholly-owned subsidiary of Vistagen.

“Approximately 75% of all women in America experience hot flashes during their menopausal transition, yet there is a critical need for new treatment options,” said Shawn Singh, President and Chief Executive Officer of Vistagen, in a statement. “As demonstrated in exploratory Phase 2a clinical data, refisolone has the potential to advance women’s health and bring a fast-acting, non-hormonal treatment option for millions of women seeking relief from menopausal hot flashes.”

According to the company, the nasal spray has a novel proposed mechanism of action with the potential to treat “multiple women’s health disorders.” The intranasal delivery at microgram-level doses is designed to rapidly activate chemosensory neurons in the nasal cavity, “which engage olfactory–limbic and olfactory–hypothalamic pathways that modulate anxiety and thermoregulatory neural circuits,” stated Vistagen.

Reference:

Vistagen Receives FDA “Study May Proceed” Letter Under its Refisolone IND Application, Enabling Further Phase 2 Clinical Development for the Treatment of Vasomotor Symptoms (Hot Flashes) due to Menopause. Vistagen. News release. Published April 22, 2026. Accessed April 22, 2026. https://www.businesswire.com/news/home/20260422186960/en/Vistagen-Receives-FDA-Study-May-Proceed-Letter-Under-its-Refisolone-IND-Application-Enabling-Further-Phase-2-Clinical-Development-for-the-Treatment-of-Vasomotor-Symptoms-Hot-Flashes-due-to-Menopause