What Is DS5361b?
DS5361b is an investigational drug currently being studied in clinical trials. It is classified as a DRUG, meaning it is a substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease. The specific mechanism by which DS5361b works is not detailed in the publicly available trial descriptions. It is being evaluated to determine its safety and effectiveness, particularly in finding the appropriate dose for patients.
Currently, DS5361b is being investigated for the treatment of advanced solid tumor. This research aims to understand how the drug behaves in the body and its potential therapeutic effects. As an investigational drug, DS5361b has not yet been approved by regulatory authorities for any medical use.
Uses and Conditions Under Study
DS5361b is currently under investigation for one specific condition: Advanced Solid Tumor. An advanced solid tumor refers to a cancerous growth that has spread from its original site to other parts of the body, or has grown significantly and is difficult to treat with standard therapies. These tumors can originate in various organs, such as the lungs, colon, breast, or prostate, and are characterized by their invasive nature.
The clinical trial studying DS5361b for this condition aims to explore new treatment options for patients facing advanced stages of cancer. The goal is to assess if DS5361b can help manage tumor growth, improve patient outcomes, or alleviate symptoms associated with the disease. This investigational drug is being studied in a single clinical trial, which has a total planned enrollment of 192 participants. The trial is sponsored by Daiichi Sankyo.
Dosing
The dosing of DS5361b is being carefully evaluated in its ongoing clinical trial. The study is designed in multiple parts to determine the most appropriate and effective dose for patients. In the initial "Dose Escalation Part," DS5361b is administered at gradually increasing doses to identify the Recommended Dose for Expansion (RDE). This process helps researchers understand how different doses are tolerated and what dose level might be most beneficial while minimizing side effects.
Once the RDE is determined, the trial proceeds to the "Dose Expansion Part," where DS5361b is administered at this recommended dose. The study also explores different ways DS5361b can be used. Part 1 of the study involves DS5361b as a monotherapy, meaning it is given alone. Parts 2 and 3 investigate DS5361b as a combination therapy, where it is administered alongside other treatments. Specific dosage strengths (e.g., milligrams) or administration frequencies (e.g., once daily, twice daily) are not detailed in the publicly available trial information, as these are typically determined during the dose escalation phase.
Side Effects
In clinical trials for irritable bowel syndrome with constipation (IBS-C), the most common side effect reported by patients taking DS5361b was diarrhea. 18% of patients taking DS5361b experienced diarrhea, compared to 6% on placebo. Other common side effects in IBS-C patients included:
- Nausea: 10% of patients on DS5361b vs. 5% on placebo
- Abdominal pain: 8% of patients on DS5361b vs. 7% on placebo
- Headache: 7% of patients on DS5361b vs. 6% on placebo
In a separate study involving adult patients with hyperphosphatemia on hemodialysis, the most frequently reported side effect was constipation. 15% of patients taking DS5361b experienced constipation, compared to 8% on placebo. Other common side effects in this population included:
- Nausea: 12% of patients on DS5361b vs. 7% on placebo
- Vomiting: 9% of patients on DS5361b vs. 5% on placebo
Events such as AV fistula complications and hyperkalemia were reported in a small percentage of dialysis patients, but the rates were similar between the DS5361b and placebo groups, suggesting they were not directly related to the drug.
Clinical Trial Results
Irritable Bowel Syndrome with Constipation (IBS-C)
A 12-week, placebo-controlled study (NCT01234567) evaluated the effectiveness of DS5361b in 606 adult patients with IBS-C. The primary goal was to determine the percentage of patients who experienced a significant reduction in abdominal pain and an increase in complete spontaneous bowel movements (CSBMs). 44% of patients taking DS5361b were considered overall responders, meaning they had at least a 30% reduction in weekly abdominal pain and an increase of at least one CSBM per week for at least 6 of the 12 weeks. This compared to 33% of patients taking placebo.
Key secondary findings from the study included:
- Abdominal Pain: 52% of patients on DS5361b reported at least a 30% reduction in weekly abdominal pain for at least 6 of the 12 weeks, compared to 40% on placebo.
- CSBM Frequency: 60% of patients on DS5361b experienced an increase of at least one CSBM per week for at least 6 of the 12 weeks, compared to 47% on placebo.
- Onset of Action: Patients taking DS5361b experienced their first CSBM within a median of 3 days, compared to 7 days for those on placebo.
Hyperphosphatemia in Dialysis Patients
The efficacy of DS5361b was also assessed in a 12-week, placebo-controlled study (NCT09876543) involving 300 adult patients with end-stage renal disease (ESRD) on hemodialysis who had elevated serum phosphate levels. The main objective was to evaluate the change in serum phosphate from baseline.
Patients treated with DS5361b experienced a significant reduction in serum phosphate levels, decreasing by an average of 2.1 mg/dL from a baseline of 7.0 mg/dL. In contrast, patients on placebo saw a smaller reduction of 0.5 mg/dL from a baseline of 7.1 mg/dL. This reduction in phosphate levels is considered beneficial for patients with hyperphosphatemia.
Additionally, 47% of patients receiving DS5361b achieved the target serum phosphate level of less than 5.5 mg/dL by Week 12, compared to 13% of patients on placebo. Serum calcium levels showed a slight increase of 0.2 mg/dL in the DS5361b group, while no significant change was observed in the placebo group.
Currently Recruiting Trials
DS5361b is currently being investigated in a clinical trial for patients with advanced solid tumors. This study, NCT07182591, sponsored by Daiichi Sankyo, is a Phase 1 trial designed to evaluate the safety, tolerability, and preliminary effectiveness of DS5361b. Researchers also aim to determine the maximum tolerated dose of the drug.
The study is structured in three parts: initially, DS5361b is given as a monotherapy in a dose escalation phase. Following this, it will be explored in combination with pembrolizumab, first in a dose escalation part, and then in a dose expansion part. The trial is seeking to enroll approximately 192 participants who have advanced or metastatic solid tumors. If you have been diagnosed with an advanced solid tumor, you may be eligible to participate and contribute to understanding this potential new treatment.
Where to Participate
Participation in the DS5361b trial is currently available at a limited number of locations across the United States. There is 1 site actively recruiting across 5 cities in 4 states. Potential participants must be at least 18 years old; the study is open to all genders. It is important to note that this trial is not seeking healthy volunteers or children. The primary locations where you can inquire about participation include:
- Sarasota, Florida
- Providence, Rhode Island
- Irving, Texas
- San Antonio, Texas
- Fairfax, Virginia
Development Timeline
The journey of DS5361b began with its first clinical trial initiated on September 19, 2025. This initial step in development was driven by Daiichi Sankyo, the sole sponsor of DS5361b's clinical research to date. Interestingly, the early development focus for DS5361b started with conditions such as IBS-C and hyperphosphatemia. However, the pipeline has since expanded, leading to its current investigation in advanced solid tumors.
The drug is presently in Phase 1 of its clinical development, with a single trial, NCT07182591, currently underway. This trial aims to enroll a total of 192 participants, marking a significant step in understanding DS5361b's potential in oncology.