Sensorium Therapeutics Reports Positive Phase 1a Results for SNTX-2643 in Anxiety Disorders

Early Study Shows CNS Activity After a Single Dose

Sensorium Therapeutics has reported positive results from a Phase 1a study of SNTX-2643, an investigational medicine being developed for social anxiety disorder (SAD) and generalized anxiety disorder (GAD).

The company presented the results at Psych Congress 2026 in New Orleans, Louisiana.

SNTX-2643 is designed to act on the serotonin transporter, or SERT, in a state-selective way. The company is developing it as a potential new type of treatment for anxiety disorders.

In the Phase 1a study, SNTX-2643 was generally well tolerated in healthy adults. The drug also showed predictable levels in the blood after different doses.

Researchers also found signs of brain activity after a single 3 mg dose. These effects started about two hours after dosing and were still visible 24 hours later.

The findings are early and were collected in healthy volunteers. They do not yet show that SNTX-2643 can treat anxiety disorders in patients.

What Is SNTX-2643?

SNTX-2643 is Sensorium Therapeutics’ lead investigational drug from its SENS-01 program.

The company is developing the medicine for social anxiety disorder and generalized anxiety disorder. It may also have potential in other central nervous system disorders.

The drug is designed to modulate the serotonin transporter, known as SERT.

Serotonin is a chemical messenger in the brain that plays an important role in mood, anxiety and other brain functions. SERT helps control how serotonin is transported and recycled between nerve cells.

Sensorium is developing SNTX-2643 as a state-selective SERT modulator. The company believes this approach could produce different effects from commonly used anxiety medicines.

The goal is to develop a medicine that could act more quickly while potentially reducing some unwanted effects associated with existing treatments.

Phase 1a Study Included 63 Healthy Adults

The Phase 1a study included 63 healthy adults.

The study was designed to look mainly at safety and how the body processes SNTX-2643.

It included several parts. One part used single ascending doses, meaning participants received increasing doses so researchers could understand how the drug behaves at different exposure levels.

Another part was a randomized, double-blind, placebo-controlled target-engagement cohort. This part was designed to see whether SNTX-2643 produced measurable changes in brain activity.

A separate open-label cohort looked at whether food affected how the drug was absorbed.

The target-engagement group included 25 participants. Fifteen received a single 3 mg dose of SNTX-2643, while 10 received placebo.

Safety was the primary endpoint of the study. Researchers also looked at blood levels of the drug and several exploratory measures of brain activity.

SNTX-2643 Was Generally Well Tolerated

The safety results from the Phase 1a study were generally positive.

Most treatment-emergent adverse events were mild and temporary.

No serious adverse events or deaths were reported. No participants stopped treatment because of an adverse event.

Researchers also did not identify clinically significant findings in laboratory tests, ECGs or physical examinations.

These findings provide early safety information as Sensorium moves the program toward studies in people with anxiety disorders.

Drug Levels Were Predictable

The study also provided information about how SNTX-2643 behaves in the body.

The median time to reach peak blood concentration was about 1.5 to two hours after dosing.

The median half-life was approximately four to six hours.

Food did not have a clinically significant effect on the exposure of SNTX-2643. This means the amount of drug reaching the bloodstream was not meaningfully changed by food under the conditions tested.

The company plans to evaluate doses higher than 3 mg in future studies.

Researchers Used EEG to Look at Brain Activity

One of the main exploratory parts of the study involved quantitative electroencephalography, or qEEG.

qEEG measures electrical activity in the brain. It can help researchers see whether a medicine is changing brain activity after it is taken.

In the 3 mg target-engagement group, SNTX-2643 increased beta activity and reduced relative delta activity beginning about two hours after dosing.

These changes remained visible through 24 hours.

Beta activity is a faster type of brain activity that is often associated with an alert and actively processing brain state. Delta activity is slower and is more common during lower-arousal states and sleep.

The pattern seen in the study was more consistent with increased cortical activation rather than sedation.

However, these were exploratory measurements. The study was not designed to prove that the changes in brain activity would translate into improvements in anxiety symptoms.

The Drug Was Also Tested During an Anxiety Challenge

Researchers used another test to see how SNTX-2643 affected the brain during an experimentally induced stress response.

Participants watched videos designed to produce fear, anxiety and other negative emotional responses.

The videos were selected from the Open Library for Affective Videos, a research library containing stimuli that have been characterized for emotional response and arousal.

The purpose was to create a controlled situation in which researchers could measure how the brain responds to psychological stress.

SNTX-2643 Reduced Stress-Related Brain Activity

During the stress challenge, participants who received placebo showed clear increases in beta and gamma EEG activity.

These higher-frequency brain signals can be associated with increased arousal and anxiety-related processing during stressful situations.

Participants who received a single 3 mg dose of SNTX-2643 showed a reduction in this response.

The difference was observed both two hours and 24 hours after dosing.

At two hours, gamma activity increased rapidly in the placebo group during the stress challenge. Researchers did not observe a similar increase in the SNTX-2643 group.

A similar separation between the treatment and placebo groups was still visible 24 hours after dosing.

Additional analyses suggested that SNTX-2643 reduced stress-related cortical activity without broadly suppressing overall brain activity.

The Brain Response Was Different at Rest and During Stress

The researchers observed two different patterns depending on the situation.

When participants were at rest, SNTX-2643 shifted brain activity toward a more activated cortical profile.

During the psychological stress challenge, the drug reduced the increase in high-frequency brain activity caused by the stressful stimulus.

This difference is important because the researchers are trying to understand how SNTX-2643 affects brain circuits under different conditions.

The findings are still exploratory, and future studies will need to determine whether this pattern is related to actual improvements in anxiety symptoms.

Effects Remained Visible as Drug Levels Fell

One of the findings Sensorium is highlighting is the difference between blood drug levels and the observed brain effects.

After a single 3 mg dose, the average plasma concentration of SNTX-2643 was approximately 6.0 ng/mL at two hours.

At 24 hours, the concentration had fallen to about 0.6 ng/mL.

Despite this large reduction in plasma concentration, the separation between SNTX-2643 and placebo during the stress challenge remained visible at 24 hours.

This could suggest that the pharmacodynamic effect may last longer than the period of peak drug exposure.

However, the company has stressed that the mechanism and duration of this finding still need to be studied.

Future trials will also need to determine whether the effect has any meaningful impact on anxiety symptoms in patients.

Researchers Also Studied Attention and Information Processing

Sensorium also evaluated event-related potentials, or ERPs.

ERPs measure the electrical response of the brain to specific stimuli. They can provide information about attention, perception and information processing.

The study did not show clinically significant impairment in the exploratory measures of attention, information processing or perceptual judgment that were evaluated.

This is relevant because sedation and cognitive impairment can be concerns with some medicines used to manage anxiety.

Still, the Phase 1a study was small and conducted in healthy volunteers, so these findings will need to be evaluated in larger patient studies.

Autonomic Measures Showed Additional Changes

Researchers also looked at measures of the body's automatic nervous system.

At two hours after dosing, SNTX-2643 was associated with a lower heart rate compared with placebo.

Heart-rate variability also increased.

A similar directional pattern was observed at 24 hours.

These findings may indicate increased parasympathetic activity, which is associated with the body's rest-and-recovery functions.

The autonomic findings were exploratory and will need further evaluation in future clinical studies.

What Sensorium Says About the Findings

Sensorium CEO and co-founder Jacob Hooker said the company developed SNTX-2643 by starting with observations in human biology and working backward to identify a potential drug target.

He said the Phase 1a results provide early evidence that the biological difference the company was targeting can also be observed in humans.

The company is particularly interested in the measurable CNS activity seen within hours of a single dose and the persistence of some effects at 24 hours.

Sensorium said the findings provide a basis for continuing development of the program.

Why New Anxiety Treatments Are Still Needed

Social anxiety disorder and generalized anxiety disorder can affect many parts of a person's daily life.

Social anxiety disorder can make normal social situations difficult. Generalized anxiety disorder can cause persistent and excessive worry that interferes with work, relationships and everyday activities.

Existing anxiety treatments include medicines that have been used for many years.

Some treatments can take several weeks to show their full effects. Others can cause problems such as sedation, tolerability issues or dependence concerns.

SNTX-2643 is being developed with the goal of producing a different treatment profile.

However, whether it can provide faster or more useful treatment for patients remains an open clinical question.

SNTX-2643 Is Designed as a State-Selective SERT Modulator

Sensorium describes SNTX-2643 as a first-in-class state-selective serotonin transporter modulator.

The company believes this mechanism could distinguish the drug from standard anxiety medicines.

The proposed development goals include rapid onset of action, reduced off-target effects and the potential to avoid sedation and other adverse effects associated with some benzodiazepines and selective serotonin reuptake inhibitors, or SSRIs.

These are development goals rather than established clinical benefits at this stage.

The Phase 1a study provides early information about safety, pharmacokinetics and CNS activity, but it does not establish clinical efficacy.

Higher Doses Will Be Studied

The 3 mg dose used in the target-engagement cohort provided the first human data on the CNS effects of SNTX-2643.

Sensorium plans to evaluate higher doses in future studies.

The next studies will help researchers understand how the drug behaves at higher exposure levels and whether the brain activity findings seen in healthy volunteers can translate into meaningful effects in people with anxiety disorders.

The company will also continue evaluating the mechanism and duration of the pharmacodynamic effects observed at 24 hours.

Results Were Presented at Psych Congress 2026

The Phase 1a findings were presented at the Psych Congress 2026 Annual Meeting in New Orleans, Louisiana.

The presentation was Poster 199, titled “The Novel Serotonin Transporter Modulator SNTX-2643: Results from a Pharmacokinetic and Target Engagement Evaluation in Healthy Adults.”

The authors were Andrew J. Cutler, M.D.; Colville Brown, M.D.; Jacob Hooker, Ph.D.; and Jerry Rosenbaum, M.D.

Colville Brown, M.D., was the presenting author.

What Comes Next for SNTX-2643?

Sensorium now plans to continue clinical development of SNTX-2643.

The company will use the Phase 1a data to help design subsequent studies, including evaluation of higher doses and testing in people with anxiety disorders.

The key question will be whether the measurable changes in brain activity and stress responses observed in healthy adults can translate into improvements in symptoms for patients with social anxiety disorder or generalized anxiety disorder.

Further studies will also provide more information about the drug's safety, dosing, duration of action and clinical effects.

About Sensorium Therapeutics

Sensorium Therapeutics is a clinical-stage CNS biotechnology company developing small-molecule medicines for psychiatric and neurological disorders.

The company uses its SensAI discovery platform to identify potential drug candidates with different mechanisms of action.

The platform combines chemistry, pharmacology, behavioral science and neuroscience.

SNTX-2643 is currently the company's lead investigational therapy and is being developed through the SENS-01 program for anxiety disorders.