Under both the Q8W and Q12W dosing regimens, the efficacy and safety of JYB1904 were comparable to those of omazulizumab administered every 4 weeks.

The effects of a single dose of JYB1904 persisted through Week 16.

Tolerability was good, with no study drug-related serious adverse events observed.

Jeyou will advance JYB1904 to Phase 3 clinical development in China.

RAPT will discuss the Phase 3 development pathway with the FDA.

RAPT will hold a conference call today at 8:30 a.m. Eastern Time.

On October 20, 2025, Shanghai Jeyou Pharmaceutical Technology Co., Ltd. (hereinafter referred to as “Jeyou Pharmaceutical”), a modern, innovative pharmaceutical company committed to becoming an internationally advanced and domestically leading enterprise; RAPT Therapeutics, Inc. (Nasdaq: RAPT), a biopharmaceutical company focused on the discovery, development, and commercialization of innovative therapies for inflammatory and immune-mediated diseases; today announced positive topline results from a Phase 2 trial conducted by Jeyou Pharma evaluating JYB1904 (RPT904) as a monotherapy for chronic spontaneous urticaria (CSU). The trial, conducted in China, was designed to evaluate the safety and efficacy of JYB1904 administered every 8 weeks (“Q8W”) and every 12 weeks (“Q12W”) compared to omalizumab administered every 4 weeks (“Q4W”). The study was not a formal non-inferiority study, and no statistical hypothesis testing was performed. The results indicate that JYB1904 administered at Q8W or Q12W demonstrates comparable efficacy and safety to omazulizumab administered at Q4W. The two companies believe these results will support the advancement of JYB1904 into Phase 3 clinical development.

This randomized, double-blind Phase 2 study enrolled 137 adult patients with chronic spontaneous urticaria inadequately controlled by H1 antihistamines. All subjects received 16 weeks of treatment and were randomized in a 1:1:1 ratio to the following three groups: Patients in the JYB1904 Q8W group received 300 mg subcutaneous (SC) injections at Week 0 and Week 8; patients in the JYB1904 Q12W group received a single 300 mg SC injection at Week 0 only (to represent a dosing interval of at least once every 12 weeks); while patients in the omazumab Q4W group received 300 mg subcutaneous injections at Weeks 0, 4, 8, and 12. The primary endpoint of this study was the change from baseline in the 7-day Urticaria Activity Score (UAS7) at Weeks 8, 12, and 16; The key secondary endpoint was the proportion of patients with UAS7 = 0 at weeks 8, 12, and 16. Following the 16-week treatment period, patients continued to be observed for a 16-week follow-up period (during which no additional treatment was administered). The data reported here are from the first 16-week treatment period.

Compared with the omazulizumab Q4W group, data from the JYB1904 Q8W and Q12W treatment groups showed numerically superior improvements in the UAS7 endpoint at all time points (Weeks 8, 12, and 16), and the proportion of patients with UAS7=0 also demonstrated a numerically higher advantage.

The mean baseline UAS7 scores for the JYB1904 Q8W group, Q12W group, and omazulizumab Q4W group were 28.7 (±7.2), 28.9 (±6.6), and 28.8 (±7.9), respectively. The least-squares means (and 95% confidence

intervals) for the change in UAS7 from baseline at the three time points are as follows:

The proportions (in percent) of patients who achieved UAS7=0 (and the 95% confidence intervals) at these three time points were as follows:

JYB1904 was well tolerated, with no serious adverse events related to the study drug and no treatment-related adverse events leading to discontinuation of treatment.

“Based on these positive results, we are preparing to advance JYB1904 to Phase III clinical trials,” said Mr. Li Sheng, President of Jeyou Pharmaceuticals. “ “We have high hopes for JYB1904 and aim to secure approval as soon as possible, with the goal of bringing this important therapy to the many patients in China suffering from chronic spontaneous urticaria.”

“Although existing biologics have been on the market for many years, there is still room for improvement in the treatment of CSU,” said Professor Zhang Jianzhong of Peking University People’s Hospital. “ “The results of this trial demonstrate that a single dose of JYB1904 can maintain efficacy for 12 weeks, which is encouraging; this means patients can receive treatment once every three months rather than requiring monthly injections. This represents a significant advancement in the field of CSU treatment, both in terms of the burden of disease and patient convenience.”

“These data confirm the highly attractive product characteristics of JYB1904. The study results not only demonstrate that JYB1904 exhibits similar or potentially superior activity compared to omazumab, but also that clinical benefits persist through Week 16 following a single dose,” added Dr. Brian Wong, President and CEO of RAPT. “We believe these data support advancing the pivotal Phase 3 clinical trial for CSU, and we plan to discuss the subsequent development plan with regulatory authorities.”

About Chronic Spontaneous Urticaria (CSU)

Chronic spontaneous urticaria is a mast cell-driven disease that clinically presents as wheals of varying sizes accompanied by intense itching. Although standard-dose H1 antihistamines provide symptom relief for some patients, they do not address the underlying pathophysiological mechanism involving IgE autoantibodies. Therefore, for patients with CSU that cannot be controlled by antihistamines, there is an urgent need for therapeutic approaches that target the upstream IgE-mast cell axis.

About JYB1904

JYB1904 is a novel anti-IgE monoclonal antibody that targets the same epitope as omazulizumab. The drug has been modified using half-life extension technology, and its potential indications include various allergic inflammatory diseases such as food allergies and chronic spontaneous urticaria. JYB1904 exerts its effects by inhibiting free and cell-bound human immunoglobulin E (IgE)—a key driver of allergic diseases. Early clinical studies indicate that JYB1904 exhibits superior pharmacokinetic and pharmacodynamic properties compared to omazulizumab, a first-generation anti-IgE monoclonal antibody.

About Shanghai Jeyou Pharmaceutical Technology Co., Ltd.

Shanghai Jeyou Pharmaceutical Technology Co., Ltd. (hereinafter referred to as “Jeyou Pharmaceutical”), originally the innovation platform of Jiangxi Jimin Kexin Group, has now evolved into an independently operated entity. The company has assembled a strong research and development team with end-to-end capabilities covering the entire drug discovery and development process. To date, more than 10 projects in Jeyou Pharmaceutical’s in-house pipeline have entered the clinical stage.

About Jiangxi Jimin Kexin Group

Jiangxi Jimin Kexin Group is a leading comprehensive pharmaceutical group in China. Since its establishment in 1999, the company has established a strong presence in key strategic areas such as oncology, nephrology, cardiovascular and cerebrovascular diseases, pain management, and respiratory medicine, and has established a full industrial chain spanning R&D, manufacturing, and commercialization. For more information, please visit: www.jemincare.com。

About RAPT Therapeutics, Inc.

RAPT is a clinical-stage immunobiopharmaceutical company dedicated to discovering, developing, and commercializing innovative therapies for patients with inflammatory and immune-mediated diseases. Leveraging its deep, proprietary expertise in immunology, the company aims to develop innovative therapies that modulate the key immune responses underlying these diseases.