SHANGHAI, China, July 10, 2026 – ImmuneOnco Biopharmaceuticals (Shanghai) Inc. (hereinafter referred to as “ImmuneOnco” or the “Company”; HKEX Stock Code: 01541.HK) announced today that the first patient has been successfully dosed (First Patient In, FPI) in the Phase II/III clinical study of its proprietary amulirafusp alfa (IMM0306) for the treatment of Immunoglobulin G4-related disease (IgG4-RD). This significant milestone marks the official commencement of the clinical development of this innovative drug in the field of rare autoimmune diseases, bringing new therapeutic hope to IgG4-RD patients who face substantial unmet medical needs.

Addressing Rare Disease Pain Points by Precisely Targeting Core Pathological Mechanisms
IgG4-RD is a chronic, progressive, fibro-inflammatory disease that can affect multiple organs, including the pancreas, bile ducts, salivary glands, lacrimal glands, and retroperitoneal tissue. In severe cases, it can lead to organ failure. Current treatment modalities are limited by low response rates, high relapse rates, and a lack of long-term evidence-based data. Inebilizumab injection (a CD19 monoclonal antibody) remains the only approved biologic for this indication, indicating a massive unmet clinical need. Studies have shown that abnormal B-cell activation and infiltration of IgG4-positive plasma cells are the core pathological mechanisms of IgG4-RD, which aligns perfectly with the therapeutic targets of IMM0306.

Designing Phase II/III Clinical Study to Accelerate Drug Development
The newly initiated Phase II/III clinical study (Registration No.: CTR20262001) has a primary endpoint of evaluating the efficacy of IMM0306 in reducing the risk of disease relapse in patients with IgG4-RD. Secondary endpoints focus on assessing the safety, tolerability, population pharmacokinetics, and immunogenicity of the drug. Subjects will receive an intravenous infusion once a week for four consecutive weeks , with the same dosing regimen to be repeated at Week 27.

Highlighting Cross-Indication Potential with Comprehensive Pipeline Expansion in Autoimmune Diseases
Clinical progress of IMM0306 in the oncology field has fully validated its superior efficacy and safety in B-cell malignancies, providing strong support for its development in B-cell-mediated autoimmune diseases. Previously, IMM0306 demonstrated potent, durable, and excellent safety profiles in an open-label, multi-center Phase Ib dose-escalation study for systemic lupus erythematosus (SLE). The study enrolled 32 patients with moderate-to-severe active SLE and evaluated four dose cohorts ranging from 0.8 mg/kg to 2.0 mg/kg. As of March 5, 2026, no dose-limiting toxicities (DLTs), no cytokine release syndrome (CRS) of any grade, and no treatment-related serious adverse events (SAEs) were observed across all dose cohorts, with immunoglobulin levels remaining stable. In terms of efficacy, peripheral blood CD19+ B cells were rapidly depleted to undetectable levels following the first dose in all patients. At Week 24, the SRI-4 response rates were outstanding across three dose cohorts: 71.4% for the 0.8 mg/kg cohort, 72.7% for the 1.2 mg/kg cohort, and 80.0% for the 1.6 mg/kg cohort, with efficacy sustained through Week 52. The 1.2 mg/kg and 1.6 mg/kg doses have been identified as the recommended Phase II doses (RP2D), and Phase II clinical trials have been initiated.

Currently, ImmuneOnco is comprehensively advancing the diversified layout of this drug in the autoimmune field. In addition to SLE and IgG4-RD, IMM0306 has received clinical trial approvals for multiple major indications, including membranous nephropathy and primary Sjögren's syndrome (pSS). Meanwhile, the subcutaneous injection formulation of IMM0306 is also under clinical development, which is expected to further improve long-term medication adherence and enhance the patient experience.

Dr. Wenzhi Tian, Founder, Chairman, CEO, and CSO of ImmuneOnco, commented:
“The successful enrollment of the first patient in the IgG4-RD indication for IMM0306 represents another important milestone for the Company in the field of rare autoimmune diseases. Currently, there is a severe lack of effective treatments for IgG4-RD. Based on the favorable safety profile and effective B-cell depletion observed in previous clinical trials, including those for SLE, we are confident in expanding this innovative therapy to a broader range of autoimmune diseases. ImmuneOnco will continue to uphold the concept of 'patient-centricity', advance all clinical trials scientifically and rigorously, and strive to bring this differentiated innovative therapy to the market as soon as possible, providing breakthrough treatment options for patients with autoimmune and rare diseases worldwide.”

Dr. Zhuli Wu, Chief Medical Officer of ImmuneOnco, stated:

“As a multi-organ rare disease, IgG4-RD is characterized by high relapse rates and significant side effects associated with glucocorticoid therapy. The successful first patient dosing of IMM0306 for the IgG4-RD indication is a crucial step in our exploration of treatments for B-cell-mediated autoimmune diseases. Leveraging the unique CD47×CD20 dual-targeting mechanism of IMM0306, we aim to reduce relapses and improve complete remission rates by depleting pathogenic B cells. The design of this Phase II/III clinical study balances scientific rigor with R&D efficiency. We will closely monitor the safety and efficacy data of the subjects, striving to provide IgG4-RD patients with a safe and effective innovative treatment option as soon as possible.”