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Fasedienol (developmental code PH94B; international nonproprietary name aloradine) is a synthetic steroidal compound of the "pherine" class, formulated as a low-dose intranasal spray for the acute, as-needed treatment of anxiety. It is chemically the synthetic 4,16-androstadien-3β-ol isomer (molecular formula C19H28O), structurally related to but deliberately distinct from the endogenous putative human pheromone 5,16-androstadienol. Unlike classical neurosteroids such as allopregnanolone, it is not appreciably absorbed into the systemic circulation and does not act by directly modulating central GABA-A receptors (the brain's main inhibitory ion channels); instead it activates peripheral chemosensory neurons in the nasal mucosa, generating afferent signals that reach the olfactory bulb and amygdala (the brain's fear and threat-processing hub). Developed by Pherin Pharmaceuticals and later licensed to VistaGen Therapeutics, it advanced through positive Phase 2 trials in social anxiety disorder but produced mixed results in the pivotal PALISADE Phase 3 program, and it has continued to be investigated for generalized anxiety disorder and post-traumatic stress disorder.
- Rapid, on-demand reduction of acute social and performance anxiety within minutes of an intranasal dose
- Non-systemic action avoids the sedation, cognitive dulling, and next-day grogginess associated with benzodiazepines
- No demonstrated tolerance, physical dependence, or withdrawal liability in clinical testing
- Objectively reduces autonomic arousal, lowering heart rate, respiratory rate, and electrodermal activity
- Generally benign, mostly local tolerability profile with no systemic hormonal effects
- Mild application-site effects such as nasal discomfort or rhinorrhea
- Headache reported in some participants
- Transient changes in taste
Overview
A non-systemic intranasal "pherine" that calms acute anxiety within minutes by activating nasal chemosensory neurons rather than by entering the brain or engaging GABA-A directly.
- Fasedienol is delivered at a microgram-scale intranasal dose and produces measurable calming within minutes, yet it is not absorbed into the bloodstream in pharmacologically meaningful amounts, so it acts entirely at the nose rather than in the brain.
- It is the synthetic 4,16-androstadien-3β-ol isomer, deliberately distinct from the endogenous 5,16-androstadienol, a putative human pheromone detectable in sweat and saliva.
- Unlike classical neurosteroids, it has no measurable affinity for GABA-A, serotonin, or nuclear steroid hormone receptors; its target is peripheral nasal chemosensory neurons, making it mechanistically unlike every approved anxiolytic.
- The international nonproprietary name aloradine refers to this molecule (PH94B) specifically, and not to the separate antidepressant pherine candidate PH10.
Mechanism
Fasedienol is a member of the "pherine" (vomeropherine) class, synthetic 16-androstene-type steroidal molecules that act at chemosensory neurons of the nasal epithelium rather than as systemically distributed drugs. Administered as a microgram-scale intranasal spray, it binds and activates isolated human nasal chemosensory receptor neurons at nanomolar concentrations (a reported half-maximal effective concentration near 200 nM), historically attributed to the vomeronasal organ (VNO, an accessory chemosensory structure), while showing no measurable affinity for nuclear steroid hormone receptors (, androgen, or glucocorticoid receptors).
This distinguishes it sharply from endogenous neurosteroids, which act centrally as positive modulators of -A receptors; fasedienol is thought to work peripherally with negligible systemic . Receptor activation produces a local electrical response, recorded as an electrogram or electrovomerogram (EGNR), whose afferent signals travel to subsets of olfactory bulb output neurons and are relayed onward to limbic circuitry.
The proposed downstream pathway engages inhibitory (gamma-aminobutyric acid-releasing) neurons and neuropeptide signaling that dampen activity in the amygdala, the bed nucleus of the stria terminalis (BNST, an extended-amygdala region governing sustained anxiety), and the locus coeruleus (LC, the brain's principal noradrenergic nucleus), thereby suppressing hypothalamic-pituitary-adrenal (HPA) axis drive and sympathetic catecholamine output.
The net effect is a rapid, minutes-scale sympatholytic and anxiolytic response, objectively reflected in reduced heart rate, respiratory rate, and electrodermal activity, achieved without sedation, systemic hormonal activity, or the tolerance and dependence associated with -A-targeting anxiolytics. Because the mechanism is receptor-mediated at the nasal mucosa and not dependent on central drug exposure, no pharmacologically active systemic metabolites are implicated.
receptor fingerprint
Human nasal chemosensory receptor neurons (vomeronasal-type)Agonist / activator at nanomolar concentrations (EC50 near 200 nM)
Nasal chemosensory neurons (peripheral)Depolarization and electrogram activation
Olfactory bulbAfferent relay of the chemosensory signal
Olfactory bulb output neuronsDownstream activation via chemosensory afferents
Amygdala fear and threat circuitryIndirect inhibitory modulation
interneurons of the BNST and locus coeruleusIndirect facilitation of inhibitory signaling
Sympathetic and autonomic outflowSympatholytic (reduces heart rate, respiratory rate, electrodermal activity)
Amygdala (fear circuit)Functional attenuation via afferent input
Sympathetic autonomic outflowSympatholytic reduction of heart rate, respiration, and electrodermal activity
Nuclear steroid hormone receptors (, androgen, glucocorticoid)No appreciable binding affinity
-A receptor (central)No direct binding or modulation
Safetyrisks and cautions, not medical advice
Across Phase 2 and Phase 3 studies, fasedienol has shown a benign tolerability profile, with adverse events that were generally mild, transient, and local to the site of administration, such as nasal discomfort, rhinorrhea, headache, and transient changes in taste. Because it is not appreciably absorbed systemically and does not bind nuclear steroid hormone receptors, it does not produce the hormonal, sedative, or cognitive effects associated with either exogenous steroids or benzodiazepines, and no signal for tolerance, physical dependence, or withdrawal has been reported. It is an investigational agent that is not approved by any major regulatory authority for any indication; therefore its long-term safety, use in pregnancy, and interactions remain incompletely defined, and any use outside a clinical trial would be off-label and unsupervised.
History
Fasedienol originates from vomeronasal and pheromone research conducted at the Monell Chemical Senses Center and by David Berliner, Louis Monti-Bloch, and colleagues in the late twentieth century, foundational work that characterized human nasal chemosensory responses to androstene steroids (Monti-Bloch and colleagues, 1994). The molecule was developed by Pherin Pharmaceuticals as a synthetic "pherine" and entered clinical testing under the code PH94B.
An early multicenter, randomized, double-blind, placebo-controlled Phase 2 trial in 91 women with generalized social anxiety disorder (Liebowitz and colleagues, American Journal of Psychiatry, 2014) reported that a single intranasal dose significantly reduced Subjective Units of Distress during public-speaking and social-interaction challenges, with 75 percent of treated participants rated much or very much improved versus 37 percent on placebo.
A subsequent as-needed Phase 2 study (Liebowitz and colleagues, Depression and Anxiety, 2016) again favored PH94B on primary anxiety measures. VistaGen Therapeutics acquired worldwide rights and advanced the compound, later assigned the international nonproprietary name aloradine, into the pivotal PALISADE Phase 3 program for social anxiety disorder. Those late-stage results were mixed: the first Phase 3 trial did not separate from placebo on its primary endpoint, while a later trial reported a positive topline signal, and the program ultimately did not secure approval for social anxiety disorder. The compound has continued to be evaluated for generalized anxiety disorder and post-traumatic stress disorder.
Reputation
Within psychiatric and nootropic circles, fasedienol is regarded as one of the more conceptually novel anxiolytic candidates of its era, notable for the claim that a drug can calm acute anxiety without entering the brain or systemic circulation and without engaging the GABA-A receptor. Its early Phase 2 data generated genuine interest as a potential non-sedating, non-addictive, on-demand alternative to benzodiazepines, and reviews of the anxiety pipeline have repeatedly singled it out as a first-in-class mechanism (Garakani and colleagues, 2020; Singewald and colleagues, 2023).
Enthusiasm has been tempered, however, by the inconsistent Phase 3 results and by longstanding scientific skepticism about the premise itself, since the adult human vomeronasal organ is widely considered vestigial and the exact identity of the nasal receptors it activates remains debated. It is best characterized as a scientifically intriguing but clinically unproven agent whose ultimate value is still unsettled.
Subjective profileweighing the evidence above
The most interesting anxiolytic idea in years, and the tolerability really is close to nothing, with no sedation, no fog and no dependence signal. But it did not reliably separate from placebo in Phase 3, and that is the fact that matters. Worth following; it is investigational and not something to obtain.
Resources
This entry is here for reference.
Research
- 1991first citedEffect of putative pheromones on the electrical activity of the human vomeronasal organ and olf…
- 2014controlled trialEffect of an acute intranasal aerosol dose of PH94B on social and performance anxiety in women…
- 2024most active year3 papers
- 2026most recentMedicines for Anxiety: A Hundred Years of Tranquillity and More to Come?
- 1.Effect of an acute intranasal aerosol dose of PH94B on social and performance anxiety in women with social anxiety disorder.
- 2.Effect of as-needed use of intranasal PH94B on social and performance anxiety in individuals with social anxiety disorder.
- 3.Effect of fasedienol (PH94B) pherine nasal spray and steroidal hormones on electrogram responses and autonomic nervous system activity in healthy adult volunteers.
- 4.Neural circuits of anxiolytic and antidepressant pherine molecules.
- 5.The human vomeronasal system.
- 6.Pharmacotherapy of Anxiety Disorders: Current and Emerging Treatment Options.
- 7.Alleviating anxiety and taming trauma: Novel pharmacotherapeutics for anxiety disorders and posttraumatic stress disorder.
- 8.Anxiety disorders, PTSD and OCD: systematic review of approved psychiatric medications (2008-2024) and pipeline phase III medications.
- 9.Neurosteroids as a prospective treatment for Social Anxiety Disorder.
- 10.Overview of Psychiatric Medications in the Pipeline in Phase III Trials as of June 1, 2024: A Systematic Review.
- 11.A Neuroanatomic and Pathophysiologic Framework for Novel Pharmacological Approaches to the Treatment of Post-traumatic Stress Disorder.
- 12.An interview with Shawn Singh: Chief Executive Officer and Director of VistaGen Therapeutics (Nasdaq: VTGN).
22 listed here; entry last updated August 2026
Reviews
My notesprivate to this device
FAQ
Is fasedienol a neurosteroid or a pheromone?
It is a synthetic steroidal molecule of the pherine (vomeropherine) class, closely related to putative human pheromones. It is often grouped with neurosteroids because of its steroid backbone, but pharmacologically it behaves very differently: classical neurosteroids act centrally on GABA-A receptors, whereas fasedienol acts peripherally on nasal chemosensory neurons and is not appreciably absorbed into the body.
How is it different from a benzodiazepine like Xanax?
Benzodiazepines enter the brain and potentiate GABA-A receptors, which relieves anxiety but can cause sedation, cognitive impairment, tolerance, and dependence. Fasedienol works from the nasal mucosa, triggering an afferent signal to the amygdala without meaningful systemic drug exposure, and in trials it produced no sedation and no dependence signal.
Is fasedienol approved or available?
No. It is an investigational drug that has not been approved by the FDA or other major regulators for any indication. It advanced through Phase 3 testing for social anxiety disorder with mixed results and has been explored for generalized anxiety disorder and post-traumatic stress disorder.
Does it rely on the human vomeronasal organ?
Its proposed mechanism involves nasal chemosensory receptors historically attributed to the vomeronasal organ. This is scientifically contested, because the adult human vomeronasal organ is widely regarded as vestigial, so the precise receptor population it activates remains an open question.
Why did the Phase 3 program produce mixed results?
Acute, as-needed anxiety trials are highly sensitive to strong placebo responses and to the exact challenge paradigm used. The first pivotal Phase 3 trial did not separate from placebo on its primary endpoint, while a later trial reported a positive topline signal, leaving the compound's efficacy for social anxiety disorder unresolved.
Limitations of the evidence
- Inconsistent efficacy in late-stage trials, where it did not reliably separate from placebo in the Phase 3 program
- Investigational status means long-term and rare adverse effects remain incompletely characterized
Adverse effects
- Mild application-site effects such as nasal discomfort or rhinorrhea
- Headache reported in some participants
- Transient changes in taste