CStone Announces Major Clinical Validation Milestone for CS2009 at ESMO 2026: Data from More Than 300 Patients Support Mechanism, Safety and Broad Antitumor Activity

CS2009, an Innovative PD-1/VEGF/CTLA-4 trispecific antibody, demonstrates a differentiated profile through synergistic triple-pathway targeting, favorable tolerability and encouraging efficacy across multiple solid tumors

Highlights

• Three pillars of clinical validation: Clinical data from over 300 patients support proof of mechanism, proof of safety and proof of concept across multiple solid tumor types.
• Innovative design and triple-pathway synergy: Pharmacodynamic (PD) observations support engagement of PD-1, CTLA-4 and VEGF pathways, reinforcing the scientific rationale for CS2009's differentiated molecular design.
• Differentiated safety profile: The growing clinical dataset shows consistent tolerability, with low rates of severe CTLA-4-associated and VEGF-related toxicities, supporting the potential for sustained treatment and combination with other therapies.
• Compelling efficacy across first-line and heavily pretreated NSCLC: CS2009 monotherapy achieved an ORR of 87.5% in first-line PD-L1-high NSCLC, reaching 100% at 30 mg/kg. In heavily pretreated NSCLC, including patients previously exposed to immunotherapy, CS2009 monotherapy demonstrated an ORR of 28.0% at 30 mg/kg, with a median duration of response of 10.5 months. In combination with chemotherapy, CS2009 achieved an ORR of 85.7% at 30 mg/kg in first-line squamous NSCLC and 55.6% at 30 mg/kg in second- or third-line immunotherapy-pretreated NSCLC.
• Strong antitumor activity in first-line and heavily pretreated pMMR/MSS metastatic colorectal cancer (mCRC): CS2009 combined with XELOX achieved an ORR of 63.6% and a DCR of 100% in first-line mCRC, including an ORR of 68.8% among patients with liver metastases. Given the limited follow-up to date, the ORR may increase as additional data mature. Importantly, CS2009 monotherapy demonstrated an ORR of 20.0% and a DCR of 93.3% in heavily pretreated mCRC, providing encouraging evidence of single-agent activity in traditionally immunotherapy-resistant pMMR/MSS disease.
• Promising antitumor activity across a broad range of additional solid tumors: Beyond NSCLC and mCRC, CS2009 has also demonstrated encouraging antitumor activity in multiple other solid tumors, including soft tissue sarcoma (STS), non-clear-cell renal cell carcinoma (nccRCC), small-cell lung cancer (SCLC), ovarian cancer, hepatocellular carcinoma, gastric cancer, esophageal cancer, metastatic castration-resistant prostate cancer (mCRPC), and triple-negative breast cancer (TNBC), further reinforcing its broad therapeutic potential as a next-generation immuno-oncology backbone.
• Global development and partnership: CStone is preparing global registrational Phase III studies and actively pursuing strategic partnership discussions with multinational pharmaceutical companies.

SUZHOU, China, Oct. 26, 2026 /PRNewswire/ -- CStone Pharmaceuticals ("CStone," HKEX: 2616), an innovation-driven biopharmaceutical company focused on the research and development of therapies for oncology, immunology, inflammation, and other key disease areas, today announced a major clinical validation milestone for CS2009, its investigational PD-1/VEGF/CTLA-4 trispecific antibody, following two Rapid Oral presentations at the European Society for Medical Oncology (ESMO) Congress 2026.

With clinical data generated from more than 300 patients across multiple solid tumor types, CS2009 has achieved three important clinical validation milestones: proof of mechanism, proof of safety, and proof of concept across a broad range of cancers. The latest ESMO data in NSCLC and mCRC further strengthen these validations with compelling monotherapy and combination efficacy results, including in patients previously treated with immunotherapy and those with traditionally immunologically "cold" tumors.

The results mark a significant clinical de-risking milestone and support the potential of CS2009's innovative design to address limitations of existing immuno-oncology therapies.

Dr. Jason Yang, Chief Executive Officer, President of R&D and Executive Director of CStone, commented: "The ESMO 2026 data represent a defining milestone in the development of CS2009. In less than two years since entering clinical development, we have generated data from more than 300 patients and built compelling, converging evidence across three essential dimensions: mechanism of action, safety and antitumor efficacy across multiple cancer types. This is far more than an incremental clinical data update. We believe it is a major step in validating the scientific rationale, differentiated design and broad therapeutic potential of CS2009.

Our ambition was never simply to combine three established targets into one molecule. We designed CS2009 to integrate the complementary benefits of PD-1, VEGF and CTLA-4 blockade while addressing the systemic toxicity that has historically constrained CTLA-4-based treatment. We have now generated robust clinical data to validate this design.

We are particularly encouraged by the promising monotherapy antitumor activity observed in heavily pretreated NSCLC following prior immunotherapy, and in traditionally 'cold' tumors such as mCRC. Together with the strong first-line combination results in NSCLC and mCRC, these findings underscore CS2009's potential as a next-generation immuno-oncology backbone. We are preparing global Phase III registrational clinical trials and are in active discussions with potential multinational partners to accelerate CS2009's development worldwide."

Learn more about CS2009 at ESMO 2026：https://www.cstonepharma.com/en/html/news/3890.html

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, immunology, 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 four innovative drugs and secured approvals for 21 new drug applications covering nine indications. The Company's pipeline comprises 13 innovative drug candidates, including potential first-in-class or best-in-class antibody-drug conjugates (ADCs) and mono-/multi-specific antibodies across oncology, immunology and inflammation. CStone has an experienced management team with comprehensive capabilities spanning 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.