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A Study of SPT-300 Compared to Placebo for Adults with Major Depressive Disorder with or without Anxious Distress

Fast replyInvestigationalNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study is looking at Major Depressive Disorder, which is a condition where people experience persistent feelings of sadness and loss of interest in activities that can affect daily life. Some people with this condition may also experience anxious distress, which means having feelings of worry or tension along with their depression. The study will test a medication called SPT-300, which contains brexanolone caprilcerbate, and compare it to placebo. The medication comes in capsule form and is taken by mouth.

The purpose of this study is to see how well SPT-300 works as a single treatment for reducing symptoms of depression in adults who have Major Depressive Disorder, whether or not they also have anxious distress. The study will also look at how safe the medication is and how well people tolerate it. Researchers want to understand if this treatment can help improve the symptoms that people with depression experience.

During the study, participants will be randomly assigned to receive either SPT-300 or placebo. The study is double-blind, which means neither the participants nor the doctors will know who is receiving which treatment. Participants will take the medication for a period of time, with the maximum daily amount being 375 milligrams. The treatment period can last up to six months. Throughout the study, participants will have regular visits where doctors will assess their depression symptoms and overall condition to see if there are any changes. The study will measure depression symptoms using standard rating scales to determine if the treatment is working.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Treatment period begins

    After enrollment, you will begin the treatment phase of the study. This is a double-blind study, which means neither you nor your doctor will know whether you are receiving the active medication SPT-300 (containing brexanolone caprilcerbate) or a placebo (an inactive substance that looks like the medication but contains no active ingredient).

    The medication will be provided in capsule form and taken by mouth.

  2. Step 2

    Regular study visits and assessments

    Throughout the study, you will attend scheduled visits where your doctor will assess your symptoms and overall health.

    At these visits, your doctor will evaluate your depressive symptoms using standardized rating scales. One of these is called the Hamilton Depression Rating Scale-17 (HAM-D-17), which is a tool that helps measure the severity of depression through a series of questions.

    Your doctor will also use the Clinician Global Impression-Severity (CGI-S) scale, which provides an overall assessment of how severe your condition is at that time.

  3. Step 3

    Visit at day 42

    At Visit 6, which occurs on Study Day 42 (approximately 6 weeks after starting treatment), your doctor will conduct important assessments.

    The changes in your depression symptoms from the beginning of the study to this visit will be measured using the HAM-D-17 scale.

    Your overall clinical condition will also be evaluated using the CGI-S scale at this visit.

  4. Step 4

    Completion of treatment phase

    After completing all scheduled visits and assessments, the treatment phase of the study will end.

    Your participation in the active treatment portion of the study will be complete at this point.

Who can join the trial?

6 criteria

  • You must be between 18 and 65 years old
  • You must be willing and able to provide written informed consent, which means you agree in writing to take part in the study after understanding what it involves
  • You must have a main diagnosis of Major Depressive Disorder, which is a condition causing persistent feelings of sadness and loss of interest in activities
  • You may have other anxiety conditions such as generalized anxiety disorder (excessive worry about everyday things), social anxiety disorder (intense fear of social situations), or panic disorder (sudden episodes of intense fear), but only if these have not been the main focus of your treatment in the past 6 months and your doctor considers depression to be your primary condition
  • Your current depressive episode, which is a period of depression symptoms, must have lasted at least 4 weeks but not more than 18 months before joining the study
  • Both men and women can participate in this study

Who cannot join the trial?

4 criteria

  • The source data does not provide specific exclusion criteria, which are reasons why a patient cannot participate in the study
  • Without detailed exclusion criteria information, it is not possible to list the specific conditions or situations that would prevent someone from joining this clinical trial
  • Exclusion criteria typically include factors such as other medical conditions, certain medications being taken, pregnancy status, or previous treatments that might affect the study results
  • For this particular study about Major Depressive Disorder, which is a condition causing persistent feelings of sadness and loss of interest, the specific reasons for exclusion are not available in the provided information
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Investigated drugs

SPT-300 is an investigational medication being studied as a treatment for major depressive disorder. This medicine is being tested to see if it can help reduce symptoms of depression when used on its own, without being combined with other antidepressant medications. In this study, it is being evaluated in adults who have depression, including those who also experience anxious distress along with their depression.

A placebo is also used in this study. A placebo looks like the real medication but contains no active medicine. It is used to help researchers understand whether any improvements seen in the study are due to the actual medication or other factors.

What is already known about the treatment

SPT-300 – SPT-300 is an investigational medication currently being studied in clinical trials for the treatment of Major Depressive Disorder, which may occur with or without feelings of anxiety and worry. The specific form of administration and exact way it works in the body have not been publicly disclosed in the available trial information, as this medication is still in the research phase and has not yet been approved for general medical use. This drug is being tested to see if it can effectively reduce symptoms of depression when used alone, without other antidepressant medications. The study aims to evaluate whether SPT-300 is safe, well-tolerated by patients, and effective in improving mood and emotional well-being in adults suffering from depression.

Investigated diseases

  • Major Depressive Disorder

    Major Depressive Disorder is a mental health condition characterized by persistent feelings of sadness, emptiness, and loss of interest in activities that were once enjoyable. The disorder affects how a person thinks, feels, and handles daily activities such as sleeping, eating, or working. Symptoms must be present for at least two weeks and represent a change from previous functioning. People with this condition may experience changes in appetite, sleep disturbances, fatigue, difficulty concentrating, and feelings of worthlessness or guilt. The disorder can occur as a single episode or recur multiple times throughout a person's life. Major Depressive Disorder significantly impairs social, occupational, and other important areas of functioning.

  • Anxious Distress

    Anxious Distress is a specifier used to describe the presence of anxiety symptoms occurring alongside another mental health condition, most commonly depression. It is characterized by feelings of tension, restlessness, and unusual worry that make it difficult to concentrate. Individuals experiencing anxious distress may feel keyed up or on edge most of the time. They often worry excessively about various events or activities and may fear that something awful might happen. The presence of anxious distress can affect how the primary condition progresses and how the person experiences their symptoms.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-521240-37-00Protocol codeSPT-300-2024-203Estimated enrolment367 patientsSponsorSeaport Therapeutics Inc.

sourced from the EU Clinical Trials Register and site verification

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).