Study designed to validate the PK/PD relationship between plasma 5‑HTP exposure and direct biomarkers of brain serotonin synthesis

Data expected to further strengthen the evidence for Serotonin Synthesis Amplification as a novel therapeutic modality for psychiatric indications

Topline data expected in Q2 2026

Evecxia Therapeutics, Inc.—a clinical-stage neuroscience company developing a novel class of Serotonin Synthesis Amplification therapies—today announced that the first patient has been dosed in a Phase 1b randomized, placebo-controlled target-engagement study in patients with depression and treated with serotonin reuptake inhibitor antidepressants.

This placebo-controlled Phase 1b trial is designed to confirm the pharmacokinetic/pharmacodynamic (PK/PD) relationship between plasma exposure of 5-hydroxytryptophan (5-HTP - the natural immediate precursor to serotonin) and direct biomarkers of brain serotonin synthesis, using EVX-301, a proprietary intravenous formulation of 5-HTP. The study evaluates changes in cerebrospinal fluid (CSF) levels of serotonin and its primary metabolite, 5-hydroxyindoleacetic acid (5-HIAA), following 24 hours of EVX-301 administration. The trial plans to enroll 18 patients with depression who are on stable serotonin reuptake inhibitor (SSRI or SNRI) treatment, randomized in a 2:1 ratio to receive EVX-301 (n=12) or placebo (n=6). Topline results are anticipated in the second quarter of 2026.

“This study represents a critical value-creation milestone for Evecxia,” said Jacob Jacobsen, PhD, Chief Executive Officer and Co-founder of Evecxia Therapeutics. “By directly linking plasma 5-HTP exposure to gold standard biomarkers of brain serotonin synthesis, we aim to conclusively demonstrate target engagement in patients already receiving standard antidepressant therapy. This mechanism-focused validation would substantially de-risk our programs and support advancement across multiple high-unmet-need psychiatric indications.”

In the second half of 2026, Evecxia plans to commence its first Phase 2 trial of lead candidate EVX-101 in obsessive-compulsive disorder (OCD) patients responding inadequately to first-line SSRIs. OCD is common, severe, and therapeutic options are scarce.

About Evecxia Therapeutics

Evecxia is the first Company dedicated to realizing the therapeutic potential of Serotonin Synthesis Amplification—building a stronger, more resilient brain serotonin system—to treat psychiatric indications. This therapeutic modality is backed by decades of clinical evidence supporting that amplifying serotonin synthesis can safely augment efficacy when serotonin reuptake inhibitor antidepressant monotherapy is inadequate. Evecxia’s novel pharmacology increases serotonin production itself, which is distinct from the pharmacologies of serotonin reuptake inhibitors and psychedelics. Evecxia has two Phase 2 clinical-stage drug candidates in development. EVX-101 is being developed as next-line oral adjunctive (add-on) therapy for obsessive-compulsive disorder (OCD) and depression patients for whom monotherapy with first-line serotonin reuptake inhibitor antidepressants (e.g., SSRIs such as Prozac®) is inadequate. EVX-301 is being developed as a rescue therapy for patients hospitalized for suicidal ideation crisis.

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"By directly linking plasma 5-HTP exposure to gold standard biomarkers of brain serotonin synthesis, we aim to conclusively demonstrate target engagement in patients already receiving standard antidepressant therapy." — Jacob Jacobsen, CEO & Co-founder