SINOMAB BIO-B (03681) announced that the SM17 subcutaneous injection bridging study conducted in China successfully completed the first cohort dosing in healthy subjects on October 14, 2025. As of the announcement date, all subjects demonstrated good tolerance with no adverse events reported, including injection site reactions (ISR).

This bridging study aims to investigate the safety, tolerability, and pharmacokinetic characteristics of SM17 subcutaneous injection formulation, and explore the bioavailability of SM17 subcutaneous injection in humans. The bridging study plans to enroll a total of 30 healthy subjects. All healthy subjects are expected to complete recruitment by November 2025, with full follow-up completed by March 2026.

SM17 is a novel, first-in-class humanized IgG4-κ monoclonal antibody that regulates type II allergic reaction pathways by targeting human interleukin-25 (IL-25) receptor, a key molecule in the "alarmin" pathway. SM17 inhibits the cascade of reactions induced after IL-25 binds to receptors (IL-17RB) on type 2 innate lymphoid cells (ILC2s) and type 2 helper T cells (Th2), thereby producing inhibitory effects on downstream signaling pathway Th2-type interleukins IL-4, IL-5, and IL-13.

IL-25 is a key "alarmin" that has been proven to be associated with pathological changes in autoimmune and inflammatory skin diseases, such as atopic dermatitis (AD). AD patients also show increased all-cause mortality and specific-cause mortality for diseases including infections, respiratory, gastrointestinal, and neoplastic diseases.

Currently approved AD therapies, including biologics, can significantly improve patients' eczema area and severity index as well as quality of life. However, current investigational and marketed drugs cannot simultaneously meet the clinical needs of rapid onset anti-pruritic effects, lesion recovery, and good safety profile, leaving significant market opportunity.

The subcutaneous injection formulation of SM17 was independently developed by the company, featuring advantages of high protein stability, good injection operability, and low injection pain. Bioavailability exceeded 90% in preclinical pharmacokinetic studies. The subcutaneous injection formulation of SM17 is expected to greatly enhance drug administration convenience and patient compliance.

The company conducted a Phase 1 first-in-human 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, showing that SM17 demonstrated good safety with no drug-related serious adverse reactions reported.

In May 2024, the company completed a Phase 1a bridging study in China, showing that SM17 had good tolerability and safety, with pharmacokinetic characteristics comparable to Caucasian populations. In April 2025, positive topline results from the SM17 Phase 1b proof-of-concept study were released. Data showed that 91.7% of patients in the high-dose group achieved itch relief indicators (NRS-4), 75% achieved lesion recovery (EASI 75) indicators, and 41.7% achieved complete or near-complete clearance of AD symptoms indicators (IGA0/1). This data was significantly superior to IL4/IL-13 monoclonal antibody drugs and demonstrated significantly better safety and tolerability compared to Janus kinase inhibitors (JAK inhibitors).

SM17 research results have been published in multiple internationally renowned journals. On April 9, 2024, "Allergy," the official journal of the European Academy of Allergy and Clinical Immunology (EAACI), published SM17 preclinical work research results, proving that SM17's efficacy in treating animal AD was comparable to JAK1 inhibitors and even performed better in some indicators. The journal "Frontiers in Immunology" also published SM17's preclinical models and Phase 1 clinical study results in healthy subjects on December 9, 2024, showing excellent performance in safety, tolerability, and pharmacokinetics in healthy subjects.

The company believes that upstream therapies targeting the Th2 inflammatory cytokine pathway, such as IL-25 receptors, will have broad effects on skin inflammation, meaning SM17 has tremendous potential for safer, more effective, and differentiated advantages in AD treatment.