Suzhou, China, November 4th, 2025—CStone Pharmaceuticals (“CStone,” HKEX: 2616),  an innovation-driven biopharmaceutical company focused on the research and development of therapies for oncology, autoimmune/inflammation, and other key disease areas, today announced that the Investigational New Drug (IND) application for the Phase Ⅱ clinical trials of CS2009 (PD-1/VEGF/CTLA-4 tri-specific antibody) combination therapies for advanced solid tumors has been approved by the China National Medical Products Administration (NMPA).

Dr. Jason Yang, CEO, President of R&D, and Executive Director at CStone, stated, “ The promising preliminary data from the Phase I study of CS2009 has given us great confidence, supporting our efforts to accelerate its Phase II development. Based on this, the Phase II clinical trial for CS2009 features a multi-cohort, parallel expansion design, comprising 15 monotherapy and combination therapy cohorts across 9 solid tumor indications, including non-small cell lung cancer (NSCLC) and hepatocellular carcinoma (HCC). The Phase II study is currently actively enrolling patients in Australia. The approval of the IND in China will further accelerate the clinical development progress, allowing us to explore and validate the broad therapeutic potential of CS2009.”

About CS2009 (PD-1/VEGF/CTLA-4 Tri-specific Antibody)

CS2009, an innovative tri-specific antibody designed and developed by CStone, combines three clinically validated targets—PD-1, VEGFA, and CTLA-4—and exerts multidimensional anti-tumor effects through synergistic actions. Specifically, anti-PD-1 activity reverses T cell exhaustion, anti-CTLA-4 activity promotes T cell activation and proliferation, while anti-VEGFA activity blocks tumor angiogenesis and improves the tumor micro-environment (TME). In the TME, anti-PD-1 and anti-CTLA-4 activities are significantly enhanced by crosslinking with VEGFA. Meanwhile, CS2009 preferentially blocks PD-1 and CTLA-4 on double-positive tumor-infiltrating T cells while minimizing interference with CTLA-4 regulation in peripheral T cells.

CStone has disclosed the preliminary Phase I data of CS2009 at the 2025 European Society for Medical Oncology (ESMO) Annual Congress.

The ongoing global, multicenter Phase II clinical trial of CS2009 features a multi-cohort, parallel expansion design to evaluate the safety, tolerability, pharmacokinetics/pharmacodynamics (PK/PD), and efficacy of CS2009 as monotherapy and combination regimens. The study comprises 15 monotherapy and combination therapy cohorts across 9 solid tumor indications, including NSCLC, HCC, colorectal cancer (CRC), platinum-resistant ovarian cancer (PROC), triple-negative breast cancer (TNBC), extensive-stage small cell lung cancer (ES-SCLC), Cervical Cancer (CC), gastric or gastroesophageal junction cancer (GC/GEJC), and esophageal squamous cell carcinoma (ESCC). Patient enrollment is actively ongoing in Australia and will soon commence in China, with subsequent expansion planned for the United States.

About CStone

CStone (HKEX: 2616), established in late 2015, is an innovation-driven biopharmaceutical company focused on the research and development of therapies for oncology, autoimmune/inflammation, and other key disease areas. Dedicated to addressing patients’ unmet medical needs in China and globally, the Company has made significant strides since its inception. To date, the Company has successfully launched 4 innovative drugs and secured approvals for 16 new drug applications covering 9 indications. The company’s pipeline is balanced by 16 promising candidates, featuring potentially first-in-class or best-in-class antibody-drug conjugates (ADCs), multispecific antibodies, immunotherapies and precision medicines. CStone also prides itself on a management team with comprehensive experiences and capabilities that span the entire drug development spectrum, from preclinical and translational research to clinical development, drug manufacturing, business development, and commercialization.

For more information about CStone, please visit: www.cstonepharma.com.

IR contact: ir@cstonepharma.com

PR contact: pr@cstonepharma.com

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