SINOMAB BIO-B: The bridging study of the subcutaneous injection formulation SM17 in China has completed the administration to the first cohort of healthy subjects

According to the announcement from SINOMAB BIO-B (03681), the bridging study for the subcutaneous injection formulation of SM17 conducted in China has successfully completed the administration to the first cohort of healthy subjects on October 14, 2025. As of the date of this announcement, all subjects have tolerated the treatment well, with no adverse events reported (including injection site reactions (ISR)). This bridging study aims to investigate the safety, tolerability, and pharmacokinetic characteristics of the SM17 subcutaneous injection formulation, as well as to explore the human bioavailability of the SM17 subcutaneous injection formulation. A total of 30 healthy subjects are planned to be enrolled in this bridging study. All healthy subjects are expected to complete recruitment by November 2025 and complete all follow-ups by March 2026.

SM17 is a novel, globally first humanized IgG4-κ monoclonal antibody that targets the key molecule interleukin 25 (IL-25) receptor, which regulates the type II allergic response pathway through the "alarmin" pathway. SM17 inhibits the receptor (IL-17RB) on type 2 innate lymphoid cells (ILC2s) and type 2 helper T cells (Th2) that is activated by IL-25 binding, thereby suppressing the downstream signaling pathways of Th2-type interleukins IL-4, IL-5, and IL-13.

IL-25 is a key "alarmin" that has been shown to be associated with pathological changes in autoimmune and inflammatory skin diseases, such as atopic dermatitis ("AD"). Patients with AD have an increased all-cause mortality and specific cause mortality from diseases including infections, respiratory, gastrointestinal, and neoplastic diseases. Currently approved AD therapies (including biologics) can significantly improve the eczema area and severity index and quality of life for patients. However, existing marketed drugs cannot simultaneously meet the clinical needs for rapid onset of itch relief, skin lesion recovery, and good safety, leaving a significant market gap.

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

The company conducted a Phase 1 first-in-human clinical trial (NCT05332834) in the United States to evaluate the safety and tolerability of SM17 in healthy subjects. Clinical reports are expected in the first quarter of 2024, showing that SM17 has good safety with no reported serious adverse reactions related to the drug. In May 2024, the company completed a Phase 1a bridging study in China, demonstrating good tolerability and safety of SM17, with pharmacokinetic characteristics comparable to those in Caucasian populations. In April 2025, positive top-line results from the Phase 1b proof-of-concept study of SM17 were released. Data showed that 91.7% of patients in the high-dose group achieved the itch relief indicator (NRS-4), 75% reached the skin lesion recovery indicator (EASI 75), and 41.7% achieved the complete or nearly complete resolution of AD symptoms indicator (IGA0/1). This data significantly outperformed IL-4/IL-13 monoclonal antibody drugs and demonstrated significantly better safety and tolerability compared to 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's preclinical work, demonstrating that SM17's efficacy in treating animal AD is comparable to that of JAK1 inhibitors, and even performs better on certain indicators. The journal "Frontiers in Immunology" also published the results of SM17's preclinical models and Phase 1 clinical studies in healthy subjects on December 9, 2024, showing its outstanding safety, tolerability, and pharmacokinetics in healthy subjects.

The company believes that upstream therapies targeting the Th2 inflammatory cytokine pathway (such as the receptor for IL-25) will have a broad impact on skin inflammation, indicating that SM17 has enormous potential for a safer and more effective treatment for AD with differentiated advantages