Shanghai, China, October 19, 2026 — ImmuneOnco Biopharmaceuticals (Shanghai) Inc. ("ImmuneOnco"; HKEX: 01541) today announced that the first patient has been enrolled and dosed in the Phase Ib clinical trial evaluating IMM0306S, the subcutaneous formulation of its wholly owned amulirafusp alfa (IMM0306), for the treatment of systemic lupus erythematosus (SLE). This milestone marks a key step in the clinical development of IMM0306S in autoimmune diseases and holds the potential to further improve long-term treatment experience and adherence for patients.

IMM0306S: A Formulation Innovation That Enhances Treatment Convenience

IMM0306S is a subcutaneous formulation developed from ImmuneOnco's amulirafusp alfa (IMM0306). Amulirafusp alfa is the world's first CD47×CD20 bispecific molecule to enter clinical development, developed on the Company's proprietary "mAb-Trap" technology platform. As a differentiated biologic, the product is being advanced in parallel for both oncology and B-cell-mediated autoimmune indications.

On August 21, 2026, ImmuneOnco announced that the Investigational New Drug (IND) application for IMM0306 in SLE had received clearance from the U.S. Food and Drug Administration (FDA). That progress represented a key step in the global clinical development of IMM0306 in autoimmune diseases and offers the prospect of a breakthrough new treatment option for millions of SLE patients worldwide.

At the European Alliance of Associations for Rheumatology (EULAR) annual meeting held in London, United Kingdom, in June 2026, ImmuneOnco presented data from the Phase Ib/II study of intravenous IMM0306 in patients with moderate-to-severe active SLE. The results showed SRI-4 response rates of 72.7% and 80.0% at Week 24 in the 1.2 mg/kg and 1.6 mg/kg dose groups, respectively, with clinically meaningful improvements across key measures and significant improvements in key biomarkers, including anti-dsDNA antibodies and complement C3/C4. The drug also demonstrated a favorable safety profile, with no observed cytokine release syndrome (CRS) or significant infectious events. ImmuneOnco will present the latest Phase Ib/II clinical findings for IMM0306 in SLE as a poster at the American College of Rheumatology (ACR) Convergence 2026 annual meeting, to be held November 6–11, 2026, in Orlando, Florida, United States.

Compared with intravenous administration, subcutaneous IMM0306S offers notable clinical advantages:

• An improved safety profile: Administered by subcutaneous injection, IMM0306S substantially lowers peak plasma concentrations, reducing the incidence of infusion-related reactions and further enhancing the safety and tolerability of treatment.

• Greater convenience and flexibility: Subcutaneous injection requires no intravenous access, greatly simplifying the administration process and shortening treatment time. In the future it may enable outpatient or at-home self-administration, markedly improving patient adherence and treatment flexibility.

Advancing a Diversified Autoimmune Pipeline

The Phase Ib study initiated for IMM0306S is a multicenter, randomized, double-blind, placebo-controlled trial designed to evaluate the safety and efficacy of IMM0306S in active systemic lupus erythematosus. Beyond SLE, ImmuneOnco's autoimmune disease pipeline is expanding rapidly, with clinical studies of IMM0306 in several high-value autoimmune indications — including IgG4-related disease and primary membranous nephropathy — advancing steadily.

Dr. Wenzhi Tian, Chairman, Chief Executive Officer and Chief Scientific Officer of ImmuneOnco, commented:

"Enrolling the first patient with IMM0306S in the SLE indication is an important achievement in our continued commitment to autoimmune diseases. Subcutaneous dosing not only improves convenience for patients but also reflects our patient-centric research and development philosophy. We will keep advancing our clinical studies efficiently, with the goal of bringing safer and more effective treatment options to patients with autoimmune diseases as soon as possible."

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

"The efficacy and safety data from IMM0306's Phase Ib/II program in SLE are encouraging. An SRI-4 response rate as high as 80.0%, with no observed CRS or serious infections, provides strong clinical evidence for CD47-targeted therapy in autoimmune diseases. Our original intent in developing the subcutaneous formulation was to give patients a more convenient and comfortable treatment experience. Completing first patient enrollment with IMM0306S is a substantive step forward in combining an innovative mechanism with an optimized formulation, and we look forward to future data further validating the value of this differentiated strategy."

Cautionary Statement under Rule 18A.05 of the Rules Governing the Listing of Securities on The Stock Exchange of Hong Kong Limited

ImmuneOnco cannot assure that IMM0306S or IMM0306 will successfully complete clinical development, receive regulatory approval or ultimately be marketed. The Company's prospects depend on numerous factors beyond its control. Shareholders and potential investors are advised to exercise caution when dealing in the shares of the Company.