SinoMab (03681.HK) Globally First-in-Class SM03 (Suciraslimab) Achieves Breakthrough Preclinical Results in SLE, DemonstraƟng PosiƟve Immune ModulaƟon with PotenƟal MulƟ-Organ ProtecƟon and Superior Long-Term Safety

【For Immediate Release】 中國抗體製藥有限公司 SinoMab BioScience Limited (Incorporated in Hong Kong with limited liability) (Stock Code: 3681) SinoMab (03681.HK) Globally First-in-Class SM03 (Suciraslimab) Achieves Breakthrough Preclinical Results in SLE, DemonstraƟng PosiƟve Immune ModulaƟon with PotenƟal MulƟ-Organ ProtecƟon and Superior Long-Term Safety (10 July 2025 - Hong Kong) SinoMab BioScience Limited (“SinoMab” or the “Company”, stock code: 03681.HK), is pleased to announce that its globally first-in-class innova Ɵve drug SM03 (Suciraslimab) targe Ɵng Systemic Lupus Erythematosus (SLE) has achieved breakthrough pre- clinical results from In-vivo study. As a monoclonal an Ɵbody targeƟng CD22(a sialic acid-binding transmembrane protein primarily expressed on B cells and associated with various autoimmune and neurodegenera Ɵve diseases), SM03 leverages its unique advantages of “Modula Ɵon of autoimmune network through B cell interacƟon and mulƟ-organ protecƟve effects” to address the unmet needs of long-term medica Ɵon safety and organ protec Ɵon benefits in SLE treatment, providing paƟents worldwide with a safer and greater efficacy new therapeuƟc opƟon. CompeƟƟve Advantages of SM03 in the Treatment of SLE: “B Cell ModulaƟon Without DepleƟon”: DifferenƟaƟng from tradiƟonal B cell depleƟon therapies (BCDTs) such as an Ɵ-CD20 therapies, SM03 specifically regulates autoreac Ɵve B cells without depleƟng normal B cells, thereby reducing infecƟon risks and maintaining immune surveillance. “Dual Mechanism and Dual Regula Ɵon”: The primary mechanism of SM03 involves upstream inhibiƟon of autoreac Ɵve B cell ac ƟvaƟon and autoan Ɵbody produc Ɵon, addressing humoral immune dysregulaƟon (humoral immune axis). The synergis Ɵc mechanism can also modulate B and other immune cell interac Ɵons, thereby ensuring an allevia Ɵon of systemic autoreac Ɵve inflammaƟon through a regulaƟon of the immune network. “Organ Protec Ɵon”: SM03 possesses unique advantage among compe Ɵtors by reducing proteinuria and alleviaƟng glomerular Ɵssue damage mediated by immune complex deposi Ɵon, which is cri Ɵcal for lupus nephri Ɵs (LN). Addi Ɵonally, through its dual-regula Ɵon effects, SM03 miƟgates immune-mediated pulmonary complica Ɵons of lupus such as recurrent alveolar hemorrhage or pulmonary arterial hypertension. These organ-protec Ɵve effects have clinical meaningfulness and are vital for treatment prognosis in the SLE area. By u Ɵlizing a humanized animal (murine) model that closely recapitulate the key pathological features of human systemic lupus erythematosus (SLE)—including the produc Ɵon of pathogenic autoanƟbodies, mulƟ-organ immune complex deposiƟon, and progressive Ɵssue damage—SM03 treatment demonstrated dis ƟncƟve and advantageous immunomodulatory proper Ɵes. The candidate drug selecƟvely inhibits acƟvated B cell subsets (e.g., CD27⁺/CD38⁺) while sparing the overall B cell populaƟon, marking a significant differenƟaƟon to the prevailing immunosuppression therapies induced by commercially available drugs. Notably, SM03 significantly reduces serum levels of anƟ-double-stranded DNA (anƟ-dsDNA) anƟbodies. Such findings have clinical significance, with a high prevalence in approximately 70% of SLE paƟents, these autoanƟbodies not only serve as biomarkers for disease acƟvity but also contribute directly to organ damage by forming immune complexes in Ɵssues such as the kidneys, skin, and joints. These complexes ac Ɵvate the complement cascade and drive progressive organ injury, par Ɵcularly playing a vital role in the pathological deterioraƟon of lupus nephriƟs (LN). Current B cell-targeted therapies in clinical applicaƟon can reduce autoanƟbody levels but o Ōen fail to significantly improve end-organ damage—an issue is significantly found in lupus nephri Ɵs (LN), which affects approximately 50% of SLE pa Ɵents. Moreover, systemic complicaƟons such as pulmonary intersƟƟal disease also lack effec Ɵve therapy. In contrast, SM03 has demonstrated breakthrough organ- protecƟve effects in preclinical studies: a restora Ɵon of proteinuria comparaƟve to healthy animal levels while also significantly reduced the intensity of glomerular immune complex deposiƟon. AddiƟonally, SM03 suppressed pulmonary inflammatory infiltraƟon and fibrosis progression, with histopathological improvements surpassing those observed with comparator drugs. This differenƟated advantage stems from SM03’s innova Ɵve mechanism of ac Ɵon: by regulaƟng autoreacƟve B cell func Ɵon in a non -depleƟng manner, it modulates autoanƟbody produc Ɵon while enhancing B cell to other immune cell interacƟon networks to suppress downstream immune cell ac ƟvaƟon cascades. This enables coordinated protec Ɵon across mul Ɵple organs. Given its clearly in vivo efficacy and favorable safety profile, SM03 is expected to be a superior therapeuƟc opƟon for LN and mulƟ-organ damage in SLE. Note: The research findings presented in this report are excerpts from ongoing studies. Detailed methodology, complete data, and analyses will be submi Ʃed for publica Ɵon in a peer -reviewed academic journal. Dr. Shui On LEUNG, Execu Ɵve Director, Chairman and Chief Execu Ɵve Officer of SinoMab, comments: "While t he global rheumatoid arthriƟs (RA) treatment market conƟnues to expand, the compeƟƟve landscape of therapeuƟcally dominant drug is remains relaƟvely fierce. In contrast, systemic lupus erythematosus (SLE), a life-threatening disease, sƟll lacks a treatment that can both effecƟvely overcome long-term immune tolerance and provide comprehensive organ protec Ɵon. This represents a significant unmet medical need and offers a substanƟal market potenƟal.” As the pioneering anƟbody targeƟng CD22, SM03 has made significant preclinical progress in the field of systemic lupus erythematosus (SLE). Leveraging its unique dual mechanism of acƟon, SM03 not only precisely modulates B cell acƟvaƟon and differenƟaƟon but also reprograms mulƟcellular interacƟon networks with B cells as the central immune hub. SM03 has demonstrated its superior efficacy and safety characterisƟcs compared to convenƟonal B cell deple Ɵon therapies in animal models. These findings provide early evidence that SM03 has the potenƟal of inducing immune tolerance, reducing autoanƟbody producƟon, and providing mulƟ-organ protecƟon. The drug is well-poised to become a first-in-class innovaƟve therapy addressing the unmet clinical needs of lupus nephriƟs (LN) and refractory SLE. Going forward, the company will accelerate the clinical development of SM03 for the SLE indica Ɵon and further expand its impact in the field of autoimmune diseases, offering this innovaƟve therapy to more paƟents worldwide. About Systemic Lupus Erythematosus (SLE) Market SLE treatment refers to a range of medical interven Ɵons aimed at managing and allevia Ɵng the symptoms of the disease. SLE is a chronic autoimmune disorder characterized by the immune system aƩacking the body’s own Ɵssues and organs, resul Ɵng in widespread inflamma Ɵon and Ɵssue damage. In recent years, the incidence of SLE has been rising globally, and the SLE treatment market is experiencing unprecedented rapid expansion. According to a report by Frost & Sullivan, there are curr ently approximately 1.0349 million SLE pa Ɵents in China, a figure projected to increase to 1.0947 million by 2030. Research Nester esƟmates that the global SLE treatment market exceeded USD 2.4 billion in 2024 and is forecasted to grow at a compound annual growth rate (CAGR) of more than 7.8%, reaching over USD 6.37 billion by 2037. - End - About SinoMab BioScience Limited SinoMab BioScience Limited (Stock Code: 03681.HK) is dedicated to the research, development, manufacturing and commercializaƟon of therapeuƟcs for the treatment of immunological diseases. SinoMab is headquartered in Hong Kong with its R&D base in Hong Kong and produc Ɵon base in mainland China. The Company's flagship product Suciraslimab (SM03) is a potenƟal global first-in- class mAb against CD22 for the treatment of rheumatoid arthri Ɵs (RA) and other immunological diseases. SM03 (Suciraslimab) has completed the Phase 3 clinical trial for RA in China and is pending NMPA’s markeƟng approval for RA in China. In addi Ɵon, the Company possesses other potenƟal first -in-class drug candidates, some of which are already in clinical stage, with their indicaƟons covering rheumatoid arthri Ɵs (RA), Sjogren’s syndrome (SS), systemic lupus erythematosus (SLE), atopic dermaƟƟs (AD), idiopathic pulmonary fibrosis (IPF), asthma, and other diseases with major unmet clinical needs. This press release is issued by Zhenzhuo 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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