SinoMab (03681.HK) Achieves Key Regulatory Milestone as NMPA Accepts IND Application for SM17, a Novel IL-25 Receptor AnƟbody for Inflammatory Bowel Disease

【For Immediate Release】 SinoMab BioScience Limited 中 國 抗 體 製 藥 有 限 公 司 (Incorporated in Hong Kong with limited liability) (Stock code: 3681) SinoMab (03681.HK) Achieves Key Regulatory Milestone as NMPA Accepts IND ApplicaƟon for SM17, a Novel IL-25 Receptor AnƟbody for Inflammatory Bowel Disease (11 December 2025 - Hong Kong) SinoMab BioScience Limited (“SinoMab” or the “Company”, Stock code: 03681.HK), is pleased to announce an InvesƟgaƟonal New Drug applicaƟon (“IND”) for SM17 in the indicaƟon of Inflammatory Bowel Disease (“IBD”) has been filed with and accepted by the Center for Drug Evalua Ɵon (the “CDE”) of the Na Ɵonal Medical Products Administra Ɵon (“NMPA”) of China. This milestone represents an important advancement in the development of SM17. Upon approval of this IND applicaƟon, the Phase 1 clinical trial data in healthy volunteers that the Company has completed or is currently conduc Ɵng may be leveraged to support the progression of the IBD indicaƟon directly to Phase 2 clinical development. This IND submission represents an important step toward expanding SM17’s therapeuƟc scope beyond atopic dermaƟƟs (“AD”) to IBD, including Crohn’s disease (“CD”) and ulcera Ɵve coli Ɵs (“UC”), which are chronic, debilita Ɵng condiƟons with significant unmet medical needs. According to the data of an independent market research insƟtuƟon, the global annual cost of IBD management is esƟmated to exceed USD 34 billion. In addi Ɵon, current therapies, including TNF blockers, an Ɵ-integrins, and IL-12/23 inhibitors, do not fully address the needs of 20–50% of paƟents due to primary non-response or secondary loss of response within 1–2 years, parƟcularly in those with fistulizing CD or extensive luminal disease. This challenge is largely aƩributable to the significant heterogeneity of IBD pathological pathways, which makes single-cytokine targe Ɵng insufficient for all pa Ɵent subsets, and is further compounded by the absence of an Ɵ-fibroƟc acƟvity in these therapies, allowing progressive Ɵssue remodeling to conƟnue in complicated cases. Long-term use also raises safety concerns, including increased risks of infecƟon and malignancy. Dr. Shui On LEUNG, Execu Ɵve Director, Chairman and Chief Execu Ɵve Officer of SinoMab, comments: "The IND for SM17 in the indicaƟon of IBD is a great milestone of the development of this innova Ɵve drug. Expanding SM17’s indica Ɵon from AD to IBD represents a significant opportunity to address unmet medical needs in a disease area of substan Ɵal clinical and commercial importance. In addi Ɵon, SM17 has mul Ɵ-mechanisƟc profile differen ƟaƟng it from current single- pathway therapies and provides a novel op Ɵon for pa Ɵents with refractory or complex disease phenotypes. A t the same Ɵme, we further believe that therapies targe Ɵng upstream of the Th2 inflammatory cytokine pathway, such as the IL-25 receptor, may have broad effects on skin inflamma Ɵon, suppor Ɵng SM17’s poten Ɵal as a differen Ɵated, safer, and more effecƟve product for the treatment of AD.” SM17 is a novel, first-in-class humanized IgG4-κ monoclonal anƟbody designed to modulate Type II inflammatory responses by targeƟng the receptor of interleukin 25 (IL-25), an “alarmin” molecule central to Type 2 immunity. By binding to the IL-25 receptor (IL-17RB) on Type 2 innate lymphoid cells (ILC2s) and Th2 cells, SM17 blocks IL-25-induced signaling cascades and suppresses downstream cytokines including IL-4, IL-5, and IL- 13. This mechanism posi Ɵons SM17 as a promising candidate for UC, where IL-25 plays a pro-inflammatory role. Furthermore, SM17 offers potenƟal benefits in CD through two complementary mechanisms: modula Ɵon of Th17 -driven inflammaƟon and an anƟ-fibroƟc effect, which may help address complicaƟons such as strictures and fistulas. This mul Ɵ-mechanisƟc profile differen Ɵates SM17 from current single -pathway therapies and provides a novel opƟon for paƟents with refractory or complex disease phenotypes. IL-25 is a criƟcal cytokine implicated in the pathogenesis of IBD, including CD and UC. These chronic inflammatory disorders of the diges Ɵve tract arise from dysfunc Ɵonal immune response to normally harmless commensal bacteria. Depending on the dominant T-helper cell subsets, these responses can be categorized into Th1-, Th2-, or Th17-driven pathways, each associated with disƟnct cytokine profiles. Pa Ɵents with IBD suffer from symptoms such as severe diarrhea, abdominal pain, rectal bleeding and weight loss, o Ōen complicated by fis tulas, strictures and colectomy in advanced stages. Beyond physical morbidity, the relapsing nature of IBD significantly impairs quality of life, with high rates of anxiety, depression and work producƟvity loss. Currently, SM17 is undergoing bridging clinical trials for dosage form conversion, which is expected to be completed as early as the end of February next year, and it is expected to enter Phase 2 clinical trials for AD by mid-2026. We will con Ɵnue to update our shareholders and poten Ɵal investors on material progress in accordance with applicable regulatory requirements. - End - About SinoMab BioScience Limited SinoMab BioScience Limited (Stock Code: 03681.HK) is a pioneer in the research and development of first-in-class and poten Ɵal best-in-class therapeuƟc anƟbody drugs, focusing on autoimmune diseases, neurodegeneraƟve diseases, and other debilita Ɵng diseases, commi Ʃed to addressing unmet medical needs. SinoMab has consistently focused on developing therapeu Ɵc anƟbodies targeƟng novel targets and employing innova Ɵve mechanisms, aiming to achieve differen Ɵated clinical outcomes in areas where exis Ɵng therapies have shown limited efficacy. Its rich R&D pipeline includes: SM17, which has demonstrated excepƟonal anƟ-pruriƟc effects, skin clearance rates, and safety profiles in the treatment of AD , with poten Ɵal applica Ɵons in asthma and idiopathic pulmonary fibrosis (IPF); its flagship anƟ-CD22 anƟbody, Suciraslimab , which has been clinically validated for efficacy in rheumat oid arthri Ɵs (RA) and is currently undergoing clinical evaluaƟon for systemic lupus erythematosus (SLE) and Alzheimer's disease; another innova Ɵve anƟ-CGC (common gamma chain) monoclonal anƟbody, which is preparing to enter clinical studies for the treatment of alopecia areata and viƟligo; and a bispecific monoclonal anƟbody developed by SinoMab that simultaneously sƟmulates bone growth and inhibits bone loss for the treatment of osteoporosis. With breakthrough efficacy as its core pursuit, SinoMab conƟnuously redefines paƟent care standards and maintains a leading posiƟon in the field of breakthrough therapies. This press release is issued by Zhenzhuo Group on behalf of SinoMab BioScience Limited. Investor and Media Inquiries Contact Person: Sherry Wong Citrus Jiang Amy Kiang Phone: (852) 5316 9995 Email: [email protected]

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