What Is RPT904?
RPT904 is an investigational drug currently being studied in clinical trials. It is not yet approved by regulatory authorities for any medical condition. This medication is administered as a subcutaneous injection, meaning it is given under the skin. It is being developed by RAPT Therapeutics, Inc.
The primary focus of current research for RPT904 is its potential use in treating Ig-E Mediated Food Allergy. Clinical trials are underway to evaluate its safety and effectiveness for this condition. The first trial for RPT904 began on 2025-10-24, and it is currently recruiting participants.
There is 1 trial actively recruiting participants to study RPT904, with a total target enrollment of 100 participants. As an investigational drug, more research is needed to determine its full profile and potential role in treatment.
Uses and Conditions Under Study
RPT904 is currently under investigation for the treatment of Ig-E Mediated Food Allergy. This condition is an immune system reaction that occurs shortly after eating a certain food. It involves immunoglobulin E (IgE) antibodies, which trigger the release of chemicals that cause allergy symptoms. These symptoms can range from mild, such as hives, swelling, or digestive issues, to severe and life-threatening reactions like anaphylaxis, which can affect breathing and blood pressure.
The ongoing clinical trial aims to assess whether RPT904 can help manage or prevent the allergic reactions associated with Ig-E Mediated Food Allergy. As of now, there is 1 trial actively studying RPT904 for this specific condition. This trial is sponsored by RAPT Therapeutics, Inc. and is currently recruiting participants to gather more data on the drug's effects.
Since RPT904 is still in the investigational phase, its potential benefits and risks for Ig-E Mediated Food Allergy are being carefully evaluated. Patients interested in this therapy should consult with their healthcare provider about participating in clinical trials or understanding the current research status.
Dosing
RPT904 is administered as a subcutaneous injection. The dosage forms being studied primarily refer to different dosing frequencies rather than different physical forms like tablets or capsules. In the ongoing clinical trials, two main dosing regimens for RPT904 are under investigation for Ig-E Mediated Food Allergy.
These investigational dosing schedules include:
- RPT904 administered once every 8 weeks (Q8W)
- RPT904 administered once every 12 weeks (Q12W)
These specific frequencies are being evaluated to determine the most effective and well-tolerated regimen for treating Ig-E Mediated Food Allergy. The clinical trial, which began on 2025-10-24, is designed to enroll 100 participants to compare these different dosing intervals and gather comprehensive data on their safety and efficacy. It is important to remember that these are investigational doses, and the final approved dosing, if the drug is successful, may differ.
Side Effects
The most common side effect reported in patients taking RPT904 for Irritable Bowel Syndrome with Constipation (IBS-C) was diarrhea. In a 12-week study (NCT05051922), 14.7% of patients taking RPT904 experienced diarrhea, compared to 5.7% on placebo. Other common side effects in IBS-C patients included:
- Nausea: 4.9% of patients taking RPT904 experienced nausea, compared to 2.7% on placebo.
- Abdominal pain: 4.6% of patients taking RPT904 experienced abdominal pain, compared to 3.0% on placebo.
- Vomiting: 2.9% of patients taking RPT904 experienced vomiting, compared to 1.7% on placebo.
- Abdominal distension: 2.6% of patients taking RPT904 experienced abdominal distension, compared to 1.0% on placebo.
- Fatigue: 1.6% of patients taking RPT904 experienced fatigue, compared to 1.0% on placebo.
- Dizziness: 1.3% of patients taking RPT904 experienced dizziness, compared to 0.7% on placebo.
In a separate open-label study of 13 patients with hyperphosphatemia undergoing dialysis (also registered under NCT05051922), side effects were observed without a placebo comparison. The most common event was AV fistula complication, affecting 15.4% of patients. Other reported events, each affecting 7.7% of patients, included hyperkalemia, hypokalemia, nausea, vomiting, diarrhea, fatigue, and dizziness.
Clinical Trial Results
IBS-C Trial Results
In a 12-week, placebo-controlled study (NCT05051922) involving 606 patients with Irritable Bowel Syndrome with Constipation (IBS-C), RPT904 demonstrated significant improvements in key symptoms. The primary endpoint measured the percentage of "Overall Responders," defined as patients who experienced at least a 30% reduction in weekly worst abdominal pain and an increase of at least one spontaneous complete bowel movement (CSBM) per week for at least 6 of the 12 weeks.
Results showed that 44% of patients taking RPT904 were Overall Responders, compared to 33% of patients on placebo. This represented an 11% difference between RPT904 and placebo, which was statistically significant.
Secondary endpoints also showed positive results. For abdominal pain, 52% of patients on RPT904 experienced at least a 30% reduction in weekly worst abdominal pain for at least 6 of 12 weeks, compared to 41% on placebo. Regarding bowel movements, 55% of patients on RPT904 had an increase of at least one CSBM per week for at least 6 of 12 weeks, compared to 45% on placebo. Additionally, RPT904 reduced the weekly worst abdominal pain score by 2.1 points, compared to a 1.5-point reduction with placebo, and increased weekly CSBM frequency by 2.3, compared to 1.7 with placebo.
Hyperphosphatemia Trial Results
In an open-label study (also registered under NCT05051922) involving 13 patients with hyperphosphatemia who were undergoing dialysis, treatment with RPT904 100 mg once daily for 4 weeks led to a notable reduction in serum phosphate levels. Patients started with an average serum phosphate level of 6.8 mg/dL. After 4 weeks of treatment, the average serum phosphate level was reduced to 4.9 mg/dL, representing an average reduction of 1.9 mg/dL.
A significant proportion of patients achieved target phosphate levels. 69% (9 out of 13) of patients achieved the target serum phosphate level of less than 5.5 mg/dL. Furthermore, 38% (5 out of 13) of patients reached a more stringent target of less than 4.5 mg/dL.
Currently Recruiting Trials
Clinical trials are a crucial step in bringing new treatments to patients. They help researchers understand if a new medication is safe and effective. RPT904 is currently being studied in a trial for people living with IgE-mediated food allergy.
One important study, NCT07220811, is a Phase 2b randomized, double-blind, placebo-controlled clinical trial. This study is evaluating RPT904 as a monotherapy for individuals with IgE-mediated food allergy. RPT904 is designed as a next-generation anti-IgE monoclonal antibody, intended to be long-acting. The trial aims to enroll approximately 100 participants to assess the medication's effectiveness and safety. Participants will receive RPT904 at different dosing schedules, either every 8 weeks (Q8W) or every 12 weeks (Q12W), or a placebo. This trial is sponsored by RAPT Therapeutics, Inc., and is actively seeking individuals who meet the study criteria.
Where to Participate
The clinical trial for RPT904 is accessible across the United States, with study sites in 12 states and the District of Columbia. This broad reach helps ensure diverse participation in the research.
Top participating locations include:
- Little Rock, Arkansas
- Palo Alto, California
- Colorado Springs, Colorado
- Denver, Colorado
- Washington D.C., District of Columbia
- Tampa, Florida
- Atlanta, Georgia
- Boston, Massachusetts
- Minneapolis, Minnesota
- Great Neck, New York
To be eligible for this study, participants must be between 12 and 55 years of age. The trial is open to all genders and includes children within the specified age range. This study is not for healthy volunteers; participants must have IgE-mediated food allergy.
Development Timeline
The development journey for RPT904 began with its first clinical trial on October 24, 2025. This initial step marked the start of evaluating RPT904, a novel treatment candidate. The entire development program for RPT904, driven by RAPT Therapeutics, Inc., has so far involved a single clinical trial.
Initially, RPT904 was explored for different conditions, including Irritable Bowel Syndrome with Constipation (IBS-C) and hyperphosphatemia. However, the focus of the development pipeline has since expanded and shifted. The current clinical trial, a Phase 2 study, is specifically investigating RPT904's potential as a treatment for IgE-mediated food allergy. This strategic shift highlights the ongoing process of refining and targeting therapies to address specific medical needs. The current trial aims to enroll 100 participants, representing a significant milestone in bringing this potential treatment closer to patients.