Vistagen (VTGN) wins FDA go-ahead to advance refisolone Phase 2 hot flash studies
Filing Impact
Filing Sentiment
Form Type
8-K
Rhea-AI Filing Summary
Vistagen Therapeutics reported that the FDA issued a “Study May Proceed” letter under its U.S. Investigational New Drug application for refisolone nasal spray. This clearance allows the company to advance refisolone’s Phase 2 clinical development in the U.S. for menopausal vasomotor symptoms, or hot flashes.
The update highlights prior exploratory Phase 2a data from Mexico, where refisolone showed rapid, statistically significant reductions in hot flash frequency and severity versus placebo and was well-tolerated, supporting further development of this non-hormonal, intranasal women’s health candidate.
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Insights
FDA clearance to proceed Phase 2 refisolone trials strengthens Vistagen’s women’s health pipeline.
Vistagen has received an FDA “Study May Proceed” letter for refisolone nasal spray under its U.S. IND. This formally permits further Phase 2 development in the U.S. for moderate to severe vasomotor symptoms (hot flashes) due to menopause, a large women’s health need.
The company cites an exploratory randomized, double-blind, placebo-controlled Phase 2a study in Mexico (N=36). Refisolone 3.2 μg, used intranasally as needed up to five times daily for four weeks, reduced hot flash frequency by 80% versus 36% with placebo, with benefits observed as early as one week (p < .001) and no serious drug-related adverse events.
This event is directionally positive but still early-stage. Actual commercial impact will depend on the design and outcomes of upcoming U.S. Phase 2 studies, subsequent Phase 3 data, and future regulatory decisions, as emphasized by the extensive forward-looking statement and risk disclosures.
8-K Event Classification
2 items: 8.01, 9.01
2 items
Item 8.01
Other Events
Other
Voluntary disclosure of events the company deems important to shareholders but not covered by other items.
Item 9.01
Financial Statements and Exhibits
Exhibits
Financial statements, pro forma financial information, and exhibit attachments filed with this report.
Key Figures
Phase 2a study size: 36 patients
Refisolone dose: 3.2 μg
Hot flash reduction refisolone: 80% reduction
+3 more
6 metrics
Phase 2a study size
36 patients
Randomized, double-blind, placebo-controlled menopausal VMS trial in Mexico
Refisolone dose
3.2 μg
Intranasal, as needed up to five times daily for four weeks
Hot flash reduction refisolone
80% reduction
Decrease in daily menopausal hot flash frequency in refisolone-treated patients
Hot flash reduction placebo
36% reduction
Decrease in daily hot flash frequency in placebo group
Onset of effect
1 week
Reduction in frequency observed as early as one week (p < .001)
Prevalence of hot flashes
Approximately 75%
Proportion of women in America experiencing hot flashes during menopausal transition
Key Terms
Investigational New Drug (IND) application, vasomotor symptoms (VMS), pherines, double-blind, placebo-controlled, +2 more
6 terms
Investigational New Drug (IND) application regulatory
"letter from the U.S. Food and Drug Administration (FDA) under its U.S. Investigational New Drug (IND) application for refisolone nasal spray"
An investigational new drug (IND) application is a formal request submitted to a drug regulator asking permission to begin testing a new medicine in people. It compiles lab results, manufacturing details and proposed human trial plans so regulators can judge safety before human studies start; for investors, an accepted IND is a key milestone that opens the clinical development pathway and can materially change a company’s risk profile and potential value, like getting a license to road-test a prototype.
vasomotor symptoms (VMS) medical
"Phase 2 development for treatment of moderate to severe vasomotor symptoms (VMS) (also known as “hot flashes”) due to menopause"
Vasomotor symptoms are sudden changes in body temperature regulation, most commonly experienced as hot flashes and night sweats, caused by brief shifts in blood flow and nervous system signals that control heat. They matter to investors because they create demand for drugs, therapies and devices, influence healthcare spending and clinical trial activity, and can affect workforce productivity—making them a clear market and regulatory opportunity.
pherines medical
"a new class of intranasal product candidates called pherines, today announced receipt of a “Study May Proceed” letter"
double-blind, placebo-controlled clinical
"exploratory randomized (N=36), double-blind, placebo-controlled Phase 2a clinical study in VMS (hot flashes)"
A clinical trial design in which participants are randomly assigned to receive either the experimental treatment or an inactive substitute (a placebo), and neither the participants nor the researchers know who is receiving which. This setup limits bias and makes it far easier to tell whether a drug or intervention truly works, similar to a blind taste test, so results carry more weight for regulatory decisions and for investors assessing a product’s commercial prospects.
non-systemically absorbed medical
"on-demand, fast-acting, non-hormonal, and non-systemically absorbed treatment, potentially without certain drug-related adverse events"
olfactory–limbic and olfactory–hypothalamic pathways medical
"activate chemosensory neurons in the nasal cavity, which engage olfactory–limbic and olfactory–hypothalamic pathways that modulate anxiety and thermoregulatory neural circuits"
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 8-K
CURRENT REPORT
PURSUANT TO SECTION 13 OR 15(d) of the SECURITIES EXCHANGE ACT OF 1934
Date of Report (Date of earliest event reported): April 22, 2026
(Exact name of registrant as specified in its charter)
(State or other jurisdiction of incorporation) | (Commission File Number) | (IRS Employer Identification Number) | ||||||
(Address of principal executive offices)
(650 ) 577-3600
(Registrant’s telephone number, including area code)
Not Applicable
(Former name or former address, if changed since last report)
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:
Securities registered pursuant to Section 12(b) of the Act:
| Title of each class | Trading Symbol(s) | Name of each exchange on which registered | ||||||
Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR 230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR 240.12b-2)
Emerging Growth Company o
If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act o
Item 8.01 Other Events.
On April 22, 2026, Vistagen Therapeutics, Inc. (the “Company”) issued a press release to announce that the Company has received a “Study May Proceed” letter from the U.S. Food and Drug Administration (“FDA”) under its U.S. Investigational New Drug application for refisolone nasal spray, the Company’s non-hormonal, non-systemic product candidate in Phase 2 development for treatment of moderate to severe vasomotor symptoms (also known as “hot flashes”) due to menopause.
The FDA’s Study May Proceed letter enables the Company to pursue further Phase 2 clinical development of refisolone in the U.S., building on successful exploratory Phase 2a clinical studies for the treatment of menopausal hot flashes and premenstrual dysphoric disorder previously conducted in Mexico. A copy of the press release is attached to this Current Report on Form 8-K as Exhibit 99.1.
Item 9.01 Financial Statements and Exhibits.
(d)Exhibits Index
| Exhibit No. | Description | |||||||
| 99.1 | Press Release issued by Vistagen Therapeutics, Inc., dated April 22, 2026 | |||||||
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document) | |||||||
Signatures
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.
| Vistagen Therapeutics, Inc. | ||||||||
| Date: April 28, 2026 | By: | /s/ Shawn K. Singh | ||||||
| Shawn K. Singh President and Chief Executive Officer | ||||||||
Exhibit 99.1
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
SOUTH SAN FRANCISCO, Calif. – April 22, 2026 – Vistagen (Nasdaq: VTGN), a late clinical-stage biopharmaceutical company pioneering neuroscience with nose-to-brain neurocircuitry to develop and commercialize a new class of intranasal product candidates called pherines, today announced receipt of a “Study May Proceed” letter from the U.S. Food and Drug Administration (FDA) under its U.S. Investigational New Drug (IND) application for refisolone nasal spray, the Company’s non-hormonal, non-systemic product candidate in Phase 2 development for treatment of moderate to severe vasomotor symptoms (VMS) (also known as “hot flashes”) due to menopause. The FDA’s Study May Proceed letter enables the Company to pursue further Phase 2 clinical development of refisolone in the U.S. for a large unmet need in women’s health, building on successful exploratory Phase 2a clinical studies for the treatment of menopausal hot flashes and premenstrual dysphoric disorder conducted in Mexico.
“This regulatory milestone marks another important step forward in our women’s health program for refisolone. 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. “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.”
In an exploratory randomized (N=36), double-blind, placebo-controlled Phase 2a clinical study in VMS (hot flashes) due to menopause in menopausal women with eight (8) or more daily hot flashes, refisolone was administered intranasally at a 3.2 μg dose as needed up to five (5) times daily for four (4) weeks. Refisolone (n=18) demonstrated 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. The reduction in the frequency of hot flashes was observed as early as one (1) week (p < .001) in the refisolone population. Refisolone was well-tolerated in the study, with no serious drug-related adverse events. The exploratory Phase 2a study was conducted in Mexico by Pherin Pharmaceuticals, now a wholly owned subsidiary of Vistagen.
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. Connect at www.Vistagen.com.
Forward Looking Statements
This press release contains certain forward-looking statements within the meaning of the federal securities laws, including, without limitation, statements regarding the potential to pursue and conduct, and the intended outcome of, further Phase 2 clinical studies of refisolone for women’s health conditions, including refisolone’s potential as a new treatment option for moderate to severe vasomotor symptoms (hot flashes) due to menopause, and the proposed mechanism of action of refisolone and Vistagen’s other pherine product candidates. These forward-looking statements involve known and unknown risks that are difficult to predict and include all matters that are not historical facts. In some cases, you can identify forward-looking statements by the use of words such as “may,” “could,” “expect,” “project,” “outlook,” “strategy,” “intend,” “plan,” “seek,” “anticipate,” “believe,” “estimate,” “predict,” “potential,” “strive,” “goal,” “continue,” “likely,” “will,” “would” and variations of these terms and similar expressions, or the negative of these terms or similar expressions. Such forward-looking statements are necessarily based upon estimates and assumptions that, while considered reasonable by Vistagen and its management, are inherently uncertain. As with all pharmaceutical products, there are substantial risks and uncertainties in the process of pursuing development and commercialization of development-stage product candidates, and actual results or developments may differ materially from those projected or implied in these forward-looking statements. There can be no guarantee that any of Vistagen’s product candidates, including refisolone, will successfully complete ongoing or future clinical trials within estimated timelines or at all, receive regulatory approval or be commercially successful. Other factors that may cause such a difference include, without limitation, risks and uncertainties relating to conducting and/or completing ongoing clinical trials, as currently expected or at all; Vistagen’s ability to successfully employ cash preservation measures and secure adequate financing for its operations, including financing or collaborative support for continued clinical development of refisolone and its other product candidates; Vistagen's dependence on third-party collaborators for the development, regulatory approval, and/or commercialization of its product candidates and other aspects of its business, which are outside of Vistagen's full control; risks associated with current and potential future healthcare reforms; the scope and enforceability of Vistagen’s pending patent applications and patents, including some patent properties related to various methods of using refisolone to treat migraines and dysmenorrhea and other patent properties related to methods of using Vistagen’s other pherine product candidates to treat various disorders; fluctuating costs of materials and other resources and services required to conduct Vistagen’s ongoing and/or planned clinical and non-clinical trials; market conditions; the impact of general economic, industry or political conditions in the United States or internationally; and other technical and unexpected hurdles in the development, manufacture and commercialization of Vistagen’s product candidates. These risks and others are more fully discussed in the section entitled “Risk Factors” in Vistagen’s Quarterly Report on Form 10-Q for the period ended December 31, 2025, as well as discussions of potential risks, uncertainties, and other important factors in our other filings with the U.S. Securities and Exchange Commission (SEC). Vistagen’s SEC filings are available on the SEC’s website at www.sec.gov. You should not place undue reliance on these forward-looking statements, which apply only as of the date of this press release and should not be relied upon as representing Vistagen’s views as of any subsequent date. Vistagen explicitly disclaims any obligation to update any forward-looking statements other than as may be required by law. If Vistagen does update one or more forward-looking statements, no inference should be made that Vistagen will make additional updates with respect to those or other forward-looking statements.
Investor Inquiries:
IR@vistagen.com
Media Inquiries:
Media@vistagen.com
References
Monti, L. et. al. (2024) Refisolone PH80 Nasal Spray for Treatment of Vasomotor Symptoms (Hot Flashes) Associated with Menopause: Phase 2 Randomized, Controlled Study. The Menopause Society 2024 Annual Meeting. September 10, 2024
FAQ
What did Vistagen Therapeutics (VTGN) announce regarding refisolone?
Vistagen announced it received an FDA “Study May Proceed” letter under its U.S. IND for refisolone nasal spray. This clearance allows further Phase 2 clinical development in the U.S. for treating moderate to severe vasomotor symptoms (hot flashes) due to menopause.
What prior clinical data support Vistagen’s refisolone program?
Refisolone’s program is supported by an exploratory randomized, double-blind, placebo-controlled Phase 2a study in Mexico with 36 menopausal women. Refisolone significantly reduced hot flash frequency and severity versus placebo over four weeks and was well-tolerated, with no serious drug-related adverse events reported.
How effective was refisolone in the Phase 2a hot flash study?
In the exploratory Phase 2a study, refisolone-treated patients showed an 80% reduction in daily hot flash frequency versus 36% in the placebo group. Improvements appeared as early as one week (p < .001), suggesting a rapid effect in reducing menopausal vasomotor symptoms.
What makes refisolone different from existing menopause hot flash treatments?
Refisolone is described as a non-hormonal, non-systemically absorbed intranasal pherine with a novel proposed mechanism of action. It is designed as a potential on-demand, fast-acting treatment, aiming to avoid certain hormone-related safety signals associated with current FDA-approved therapies for menopausal hot flashes.
What broader pipeline focus does Vistagen (VTGN) highlight?
Vistagen highlights a pherine-based pipeline of five clinical-stage intranasal product candidates. These are designed to modulate nose-to-brain neurocircuitry for conditions including social anxiety disorder, major depressive disorder, and vasomotor symptoms due to menopause, aiming for rapid-onset effects without systemic absorption.
What risks and uncertainties does Vistagen note about refisolone’s development?
Vistagen emphasizes that development involves substantial risks, including the possibility that refisolone may not complete clinical trials on expected timelines or at all, obtain regulatory approval, or achieve commercial success. The company also cites financing needs, collaborator dependence, and patent, market, and economic risks.