RAPT Therapeutics Initiates prestIgE Phase 2b Clinical Trial of Ozureprubart (RPT904) in Patients with Food Allergies

Rhea-AI Summary

RAPT (Nasdaq: RAPT) initiated the randomized, double-blind, placebo-controlled prestIgE Phase 2b trial of ozureprubart (RPT904) in IgE-mediated food allergy on Oct 27, 2025. The study will run at approximately 30 sites across the U.S., Canada and Australia and tests two dosing regimens (subcutaneous every 8 weeks or every 12 weeks, with a loading dose) versus placebo in a 2:2:1 ratio.

Part 1 will treat ~100 participants with at least one food allergy (peanut, milk, egg, walnut or cashew) for 24 weeks with a primary endpoint measured by DBPCFC at Week 24. Part 2 continues treatment to Week 48 with a DBPCFC at Week 48 and a 16-week safety follow-up. The program follows prior promising Phase 2 data in chronic spontaneous urticaria and positions ozureprubart as a long‑acting anti‑IgE bio‑better targeting the same epitope as omalizumab.

Positive

• Phase 2b initiation across ~30 clinical sites
• Two long‑interval dosing regimens: every 8 weeks and every 12 weeks
• Part 1 enrollment target of ~100 participants across common food allergens
• Primary efficacy assessed by DBPCFC at Week 24
• Builds on promising Phase 2 results in chronic spontaneous urticaria

Negative

• Part 1 sample size of ~100 participants may limit early subgroup analyses
• No clinical efficacy results reported; primary endpoint not assessed until Week 24
• Full randomized treatment and DBPCFC schedule extends to Week 48 plus 16‑week follow‑up

Insights

Clinical Development Analyst

RAPT launched a Phase 2b anti-IgE trial testing ozureprubart in food allergy; primary readout at Week 24.

RAPT Therapeutics advances ozureprubart, a half-life extended anti-IgE monoclonal antibody, into a randomized, double-blind, placebo-controlled Phase 2b. The study compares two subcutaneous dosing schedules, every 8 weeks and every 12 weeks, versus placebo in a 2:2:1 ratio and enrolls about 100 participants in Part 1. The primary efficacy assessment is a prespecified threshold at a DBPCFC at Week 24, with continued treatment and a second challenge at Week 48 and a 16-week safety follow-up.

The program’s logic rests on matching omalizumab’s epitope while extending durability to reduce dosing frequency. Key risks include the small Part 1 sample size for broad claims, reliance on a single DBPCFC timepoint for primary readout, and variability across the included allergens (peanut, milk, egg, walnut, cashew). Operational risks include enrollment and retention across ~30 sites in three countries and the impact of re-randomizing placebo participants on interpretation of longer-term efficacy.

Watch the Week 24 DBPCFC primary outcome as the first decisive milestone, then the Week 48 data for durability by dosing interval and safety signals during the 16-week follow-up. If the Week 24 endpoint meets its threshold, the next 6–12 months of Part 2 data and safety follow-up will determine whether dosing-frequency claims have clinical backing.

• Trial initiation in food allergy follows promising results in Phase 2 trial in chronic spontaneous urticaria, another IgE-driven condition
• RAPT seeks to develop a differentiated anti-IgE therapy for the many patients with food allergies

SOUTH SAN FRANCISCO, Calif., Oct. 27, 2025 (GLOBE NEWSWIRE) -- RAPT Therapeutics, Inc. (Nasdaq: RAPT), a clinical-stage immunology-based biopharmaceutical company focused on discovering, developing and commercializing novel therapies for patients living with inflammatory and immunological diseases, today announced that it has initiated the randomized, double-blind, placebo-controlled prestIgE Phase 2b clinical trial of ozureprubart (formerly RPT904) in IgE-mediated food allergy. The study will involve approximately 30 sites in the U.S., Canada and Australia.

“Food allergies are a large and growing problem for millions of patients worldwide,” said Brian Wong, M.D., Ph.D., President and CEO of RAPT. “Initiating this trial is a significant milestone that reflects our strong execution, the validity of the early preclinical and clinical data generated by our partner, Jeyou, in China and our mission to provide patients with an improved anti-IgE therapy. We look forward to working with leading food allergists in the U.S., Canada and Australia to advance development of ozureprubart.”

Hugh Sampson, M.D., Kurt Hirschhorn Professor of Pediatrics at the Icahn School of Medicine at Mount Sinai and Director Emeritus of the Jaffe Food Allergy Institute, added, “As a half-life extended anti-IgE monoclonal antibody, ozureprubart has the potential to be a transformative new therapeutic option for patients with food allergies. Targeting the same epitope as omalizumab, ozureprubart is a bio-better that is designed to match omalizumab’s established efficacy and safety profile while offering significantly improved durability and reduced dosing frequency.”

prestIgE Trial Design
The prestIgE Phase 2b trial is designed to assess the efficacy and safety of ozureprubart monotherapy in participants with IgE-mediated food allergy. The two-part, multi-center, randomized, double-blind, placebo-controlled study will compare two dosing regimens of ozureprubart (administered subcutaneously every 8 weeks or every 12 weeks, including a loading dose at Week 2) to placebo in a 2:2:1 ratio. In Part 1, approximately 100 participants with at least one food allergy (peanut, milk, egg, walnut or cashew) will be treated for 24 weeks. The primary endpoint for the trial is the proportion of participants who achieve a prespecified target threshold at a double-blind, placebo-controlled, oral food challenge (DBPCFC) at Week 24. In Part 2, the participants in the RPT904 treatment arms will continue treatment for another 24 weeks, while participants on placebo will be re-randomized 1:1 to receive ozureprubart either every 8 weeks or every 12 weeks (with a loading dose at Week 26) through Week 48 and all participants will undergo a DBPCFC at Week 48. Participants will also be followed for an additional 16 weeks in a safety follow-up period.

About Food Allergy
Food allergies are a significant and growing health problem in the United States, Europe and throughout the developed world. It is estimated that more than 17 million people in the United States have been diagnosed with a food allergy, including approximately 3.5 million children. Approximately 40% of people with food allergies are allergic to more than one food, and approximately half of food-allergic people in the United States have had a severe reaction from their food allergies. Food allergies occur when the immune system responds to a harmless food as if it were a threat. In a non-allergic patient, tolerance for food proteins develops early in life and the immune cells do not mount a response when food proteins are detected. In an allergic patient, the immune system is sensitized to one or more food proteins, or allergens (sensitization phase). As a result of this sensitization, the patient’s immune system produces IgE antibodies, which are directed against that particular allergen. The IgE antibodies bind to mast cells and basophils via its receptor called FceR1. When an IgE antibody bound to these immune cells encounters the allergen it is directed against the mast cells and basophils are activated and release histamine and other inflammatory mediators which then provoke the symptoms of an allergic reaction (effector phase). Symptoms may include hives, swelling, vomiting, abdominal pain, wheezing, breathlessness and lowered blood pressure. Allergic reactions can be triggered by exposure to minute quantities of the relevant food allergen and can be painful, frightening and potentially deadly. In some cases severe reactions known as anaphylaxis can occur which can lead to death. Such reactions require urgent medical attention and often result in treatment at hospital emergency departments.

About Ozureprubart (formerly RPT904)
Ozureprubart is a novel, half-life extended anti-IgE bio-better monoclonal antibody (mAb) targeting the same epitope as omalizumab for the treatment of patients with food allergy, chronic spontaneous urticaria and other allergic inflammatory diseases. Ozureprubart is designed to inhibit free and cell-bound human immunoglobulin E (IgE), a key driver of allergic diseases, and in early clinical studies has demonstrated extended pharmacokinetics and pharmacodynamic properties compared to omalizumab, a first generation anti-IgE mAb.

About RAPT Therapeutics, Inc.
RAPT is a clinical-stage immunology-based biopharmaceutical company focused on discovering, developing and commercializing novel therapies for patients living with inflammatory and immunological diseases. Utilizing our deep and proprietary expertise in immunology, we develop novel therapies that are designed to modulate the critical immune responses underlying these diseases.

Forward-Looking Statements
This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as “anticipate,” “estimates,” “expects,” “look forward,” “potential,” “will,” “seeks” and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. These statements relate to future events and involve known and unknown risks, uncertainties and other factors that may cause actual results, performance or achievements to be materially different from any future performances or achievements expressed or implied by the forward-looking statements. Each of these statements is based only on current information, assumptions and expectations that are inherently subject to change and involve a number of risks and uncertainties. Forward-looking statements include, but are not limited to, statements about the efficacy and safety of ozureprubart, the clinical development of ozureprubart, including the design of the prestIgE trial, plans for regulatory interactions, the therapeutic and commercial potential of ozureprubart, and other statements that are not historical fact. Many factors may cause differences between current expectations and actual results, including unexpected or unfavorable safety or efficacy data observed during clinical studies, preliminary data and trends that may not be predictive of future data or results or that may not demonstrate safety or efficacy or lead to regulatory approval, RAPT’s reliance on its partners and other third parties, clinical trial site activation or enrollment rates that are lower than expected, unanticipated or greater than anticipated impacts or delays due to macroeconomic and geopolitical conditions (including the long-term impacts of ongoing overseas conflicts, tariffs and trade tensions, fluctuations in inflation and interest rates and other economic uncertainty), changes in expected or existing competition, changes in the regulatory environment, the uncertainties and timing of the regulatory approval process and the sufficiency of RAPT’s cash resources. Detailed information regarding risk factors that may cause actual results to differ materially from the results expressed or implied by statements in this press release may be found in RAPT’s Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (SEC) on August 7, 2025 and subsequent filings made by RAPT with the SEC. These forward-looking statements speak only as of the date hereof. RAPT disclaims any obligation to update these forward-looking statements, except as required by law.

RAPT Investor Contact:
Sylvia Wheeler
swheeler@wheelhouselsa.com

RAPT Media Contact:
Aljanae Reynolds
areynolds@wheelhouselsa.com

FAQ

What is RAPT announcing about ozureprubart (RPT904) on Oct 27, 2025?

RAPT initiated the randomized, double‑blind, placebo‑controlled prestIgE Phase 2b trial of ozureprubart in IgE‑mediated food allergy across ~30 sites in the U.S., Canada and Australia.

How is the prestIgE Phase 2b trial of RAPT (RAPT) designed and dosed?

The two‑part trial randomizes participants 2:2:1 to ozureprubart dosed subcutaneously every 8 weeks or every 12 weeks (with a loading dose) versus placebo.

How many participants and which food allergies are included in Part 1 of the RAPT trial?

Part 1 will treat approximately 100 participants with at least one of these allergies: peanut, milk, egg, walnut or cashew for 24 weeks.

What are the primary efficacy timing and endpoint for RAPT’s prestIgE trial?

The primary endpoint is the proportion of participants meeting a prespecified threshold at a double‑blind, placebo‑controlled oral food challenge (DBPCFC) at Week 24.

What happens after Week 24 in the RAPT ozureprubart Phase 2b trial?

In Part 2, active‑arm participants continue to Week 48; placebo participants are re‑randomized to ozureprubart dosing through Week 48, followed by a 16‑week safety follow‑up.