SINOMAB BIO-B(03681): The first cohort of healthy subjects has completed the bridging experiment of the subcutaneous injection formulation of SM17 in China.

SINOMAB BIO-B (03681) announced that the first batch of healthy subjects in the bridging experiment of SM17 subcutaneous injection formulation conducted in China on October 14, 2025, has been successfully dosed. As of the date of this announcement, all subjects tolerated well and no adverse events (including injection site reactions (ISR)) were reported. This bridging experiment aims to study the safety, tolerability, pharmacokinetic characteristics of SM17 subcutaneous injection formulation, and explore the human bioavailability of SM17 subcutaneous injection. A total of 30 healthy subjects are planned to be enrolled in this bridging trial. All healthy subjects are expected to complete recruitment by November 2025 and complete all follow-ups by March 2026. SM17 is a novel, globally innovative humanized IgG4- monoclonal antibody that regulates the type II allergic reaction pathway through targeting the key molecule interleukin 25 (IL-25) receptor of the "alarmin" pathway. SM17 inhibits a series of reactions induced after inhibiting IL-25 binding to the receptor (IL-17RB) on type 2 innate lymphoid cells (ILC2s) and type 2 helper T cells (Th2), thereby suppressing the downstream signaling pathways of Th2-type interleukin IL-4, IL-5, and IL-13. IL-25 is a key "alarmin" that has been shown to be associated with the pathological changes in autoimmune and inflammatory skin diseases, such as atopic dermatitis (AD). AD patients have an increased overall and cause-specific mortality for diseases such as infections, respiratory, gastrointestinal, and neoplastic diseases. Currently approved therapies for AD (including biologics) can significantly improve the eczema area and severity index as well as the quality of life of patients. However, there is still a significant market opportunity as existing drugs cannot meet the clinical demand for fast-acting anti-itching, skin lesion recovery, and good safety simultaneously. The subcutaneous administration formulation of SM17 developed by the company has high protein stability, good injectability, low injection pain, and other advantages. The bioavailability in preclinical pharmacokinetic studies exceeds 90%. The subcutaneous administration formulation of SM17 is expected to greatly enhance the convenience of drug administration and patient compliance. The company conducted a Phase 1 clinical trial in the United States (NCT05332834) to evaluate the safety and tolerability of SM17 in healthy subjects. The clinical report was obtained in the first quarter of 2024, which showed that SM17 has good safety and no serious drug-related adverse reactions were reported. In May 2024, the company completed a Phase 1a bridging trial in China, showing good tolerability and safety of SM17, with pharmacokinetic characteristics comparable to the Caucasian population. In April 2025, positive topline results of the Phase 1b proof-of-concept study for SM17 were released. Data showed that 91.7% of patients in the high-dose group achieved the itching relief index (NRS-4), 75% achieved the skin lesion recovery index (EASI 75), and 41.7% achieved the complete or near-complete clearance of AD symptoms index (IGA0/1). This data significantly outperformed IL-4/IL-13 class monoclonal antibodies and demonstrated better safety and tolerability than Janus kinase inhibitors (JAK inhibitors). The research results of SM17 have been published in several internationally renowned journals. On April 9, 2024, the official journal of the European Academy of Allergy and Clinical Immunology (EAACI) "Allergy" published the research results of SM17 preclinical work, proving that the efficacy of SM17 in treating animal AD is comparable to JAK1 inhibitors and even superior in some indicators. The journal "Frontiers in Immunology" also published the Phase 1 clinical study results of SM17 in healthy subjects on December 9, 2024, showing its outstanding safety, tolerability, and pharmacokinetics in healthy subjects. The company believes that targeting upstream therapies of Th2 inflammatory cytokine pathways (such as IL-25 receptor) will have a broad effect on skin inflammation, indicating that SM17 has great potential in AD treatment with greater safety, efficacy, and differentiation advantages.