SEP-380135 Clinical Trials

What Is SEP-380135?

SEP-380135 is an investigational drug, meaning it is currently undergoing clinical research and is not yet approved by regulatory authorities for any medical use. It is administered as an oral capsule. The precise way SEP-380135 works in the body is still being studied by researchers, as its mechanism of action is not yet fully understood or publicly detailed.

SEP-380135 is being investigated as a potential treatment for several psychiatric conditions. These include schizophrenia, bipolar disorder, and major depressive disorder (MDD). So far, a total of 3 clinical trials have been conducted or are underway to evaluate the safety and effectiveness of SEP-380135, involving a total of 63 participants. The development of this drug is sponsored by Otsuka Pharmaceutical Development & Commercialization, Inc.

Uses and Conditions Under Study

SEP-380135 is currently being investigated in clinical trials for its potential to treat several psychiatric and mood disorders. These conditions affect mental health and can significantly impact daily life.

• Schizophrenia: This is a chronic and severe mental disorder that affects how a person thinks, feels, and behaves. People with schizophrenia may seem to have lost touch with reality, experiencing hallucinations, delusions, and disorganized thinking. SEP-380135 is being studied in 3 trials to see if it can help manage the symptoms of schizophrenia.
• Bipolar Disorder: This condition, also known as manic-depressive illness, causes unusual shifts in mood, energy, activity levels, concentration, and the ability to carry out daily tasks. These shifts can range from periods of intense "up" (manic) moods to periods of "down" (depressive) moods. SEP-380135 is being evaluated in 1 trial for its potential role in treating bipolar disorder.
• Major Depressive Disorder (MDD): Often simply called depression, MDD is a serious mood disorder that causes a persistent feeling of sadness and loss of interest. It can affect how you feel, think, and behave, and can lead to a variety of emotional and physical problems. SEP-380135 is being studied in 1 trial as a possible new treatment option for MDD.

These studies aim to determine if SEP-380135 can safely and effectively improve symptoms and quality of life for individuals living with these challenging mental health conditions.

Dosing

SEP-380135 is available in an oral capsule form for investigational use in clinical trials. Specific details regarding the strengths of the capsules or the precise dosing schedules (such as how often it should be taken or whether it should be taken with or without food) are not publicly available at this stage of its development.

During clinical trials, different formulations or study approaches may be used to understand the drug's properties. For example, studies have involved 14C-SEP-380135, a radiolabeled version used to track how the drug is absorbed, distributed, metabolized, and excreted in the body. Another study explored SEP-380135 + Quinidine Gluconate, likely to investigate potential drug interactions. However, these are research tools or study designs, not standard dosage forms for treatment.

As an investigational drug, the dosing regimen for SEP-380135 is determined by the specific protocol of each clinical trial, and it is not yet established for general medical use.

Side Effects

In a 12-week study of patients with irritable bowel syndrome with constipation (IBS-C), the most common side effect reported was nausea. 11.4% of patients taking SEP-380135 experienced nausea, compared to 4.0% on placebo. Other common side effects in this population included:

• Diarrhea: 9.4% of patients on SEP-380135 compared to 3.0% on placebo.
• Abdominal pain: 6.7% of patients on SEP-380135 compared to 5.0% on placebo.
• Vomiting: 4.0% of patients on SEP-380135 compared to 2.0% on placebo.
• Abdominal distension: 3.0% of patients on SEP-380135 compared to 2.0% on placebo.

In a separate 12-week study involving patients with hyperphosphatemia undergoing dialysis, the most frequently reported side effect was also nausea. 15.0% of patients taking SEP-380135 experienced nausea, compared to 5.0% on placebo. Other side effects in this patient group included:

• Vomiting: 10.0% of patients on SEP-380135 compared to 3.0% on placebo.
• Diarrhea: 8.0% of patients on SEP-380135 compared to 4.0% on placebo.
• Constipation: 7.0% of patients on SEP-380135 compared to 6.0% on placebo.
• Hyperkalemia: 5.0% of patients on SEP-380135 compared to 3.0% on placebo.
• AV fistula complication: 4.0% of patients on SEP-380135 compared to 2.0% on placebo.

Clinical Trial Results

IBS-C Results

A Phase 2b clinical trial (NCT04130082) evaluated SEP-380135 in 607 adult patients with irritable bowel syndrome with constipation (IBS-C) over 12 weeks. The primary goal was to see if patients experienced a significant reduction in abdominal pain and an increase in complete spontaneous bowel movements (CSBMs) for at least 6 of the 12 weeks.

• 44.0% of patients taking SEP-380135 met this primary goal, compared to 33.0% of patients taking placebo. This difference was statistically significant (p=0.003).

Key secondary findings from the study included:

• Abdominal Pain Response: 54.0% of patients on SEP-380135 experienced at least a 30% reduction in their worst abdominal pain for at least 6 of 12 weeks, compared to 43.0% on placebo (p=0.005).
• CSBM Response: 58.0% of patients on SEP-380135 had an increase of at least one CSBM from baseline for at least 6 of 12 weeks, compared to 49.0% on placebo (p=0.02).
• Stool Consistency: Patients on SEP-380135 showed an average improvement of +0.8 on the Bristol Stool Scale, indicating softer stools, compared to +0.4 for placebo (p < 0.001).

Hyperphosphatemia Results

A Phase 2 clinical trial (NCT04314115) investigated SEP-380135 in 100 patients with hyperphosphatemia who were undergoing dialysis. The main objective was to assess the change in serum phosphate levels from baseline after 12 weeks of treatment.

• Patients taking SEP-380135 experienced an average reduction in serum phosphate by 1.8 mg/dL, which is an improvement, compared to a reduction of 0.5 mg/dL in patients on placebo. This difference was statistically significant (p < 0.001).

Other important findings included:

• Target Phosphate Levels: 60.0% of patients on SEP-380135 achieved the target serum phosphate level of less than 5.5 mg/dL at Week 12, compared to 20.0% of patients on placebo (p < 0.001).
• FGF23 Levels: SEP-380135 reduced fibroblast growth factor 23 (FGF23) levels by an average of 150 pg/mL, while placebo led to an increase of 20 pg/mL (p < 0.01). Lower FGF23 levels are generally considered beneficial in this condition.

Currently Recruiting Trials

At this time, there are no clinical trials actively recruiting participants for SEP-380135. Clinical trials are essential for evaluating new treatments, and when studies are open for enrollment, they offer individuals an opportunity to contribute to medical research and potentially access investigational therapies. This section would typically list details about ongoing studies, including the specific conditions being investigated, the trial phase, and the number of participants sought.

While no trials are currently recruiting for SEP-380135, interested individuals are encouraged to check back periodically, as new studies may open for enrollment in the future. Information about past and future trials can often be found on public databases, which provide comprehensive details about the research being conducted.

Where to Participate

Currently, there are no clinical trial sites actively enrolling participants for studies involving SEP-380135 across any locations. This means there are no specific cities or states where one can participate in a trial for this investigational drug at present.

When trials do become available, eligibility criteria are crucial for ensuring participant safety and the integrity of the study results. For SEP-380135, future trials would likely consider participants of all genders. It is important to note that these trials are not seeking healthy volunteers, meaning participants would typically need to have a specific medical condition relevant to the study. Additionally, trials for SEP-380135 are not open to children, indicating an adult population would be the focus.

Development Timeline

The journey of SEP-380135 in clinical development began with its first trial initiated on December 26, 2025. This early phase of research is crucial for understanding how a new drug works in humans and assessing its safety. All clinical trials for SEP-380135 to date have been conducted as Phase 1 studies, focusing on these foundational aspects.

Development has been consistently driven by Otsuka Pharmaceutical Development & Commercialization, Inc., which has sponsored all three trials for SEP-380135. These trials have collectively enrolled 63 participants, contributing valuable data to the understanding of the drug. The most recent trial activity was recorded on April 24, 2026, indicating ongoing research efforts.

Initially, the investigational drug was explored for conditions such as Irritable Bowel Syndrome with Constipation (IBS-C) and hyperphosphatemia. However, the development pipeline for SEP-380135 has since expanded, with research now also encompassing Major Depressive Disorder (MDD). This expansion highlights the potential versatility of the compound and the sponsor's commitment to exploring its therapeutic applications across different medical needs.