CStone Pharmaceuticals Receives FDA Clearance for CS2009 Phase II Trial in Advanced Solid Tumors

CStone Pharmaceuticals (HKEX: 2616) announced that the U.S. Food and Drug Administration has cleared the Investigational New Drug (IND) application to initiate a Phase II clinical trial of its core asset, CS2009, in patients with advanced solid tumors. This marks a significant milestone in the global development of this innovative immunotherapy.

The CEO, President of R&D, and Executive Director at CStone stated, "We are pleased to receive FDA clearance to proceed with the global Phase II clinical trial of CS2009. This milestone follows a productive interaction with the agency, during which they reviewed our comprehensive Phase I data—including safety and antitumor activity data collected during dose escalation and expansion—and provided alignment on key elements of the Phase II study design, including dose optimization and expansion strategies. We are now actively advancing CS2009 clinical program globally and look forward to sharing further updates as the study progresses."

CS2009 is an innovative trispecific antibody designed and developed by CStone, with the potential to be first- or best-in-class. It 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.

The ongoing global, multicenter Phase II clinical trial of CS2009 features a multi-cohort, parallel expansion design to evaluate the efficacy, safety, tolerability, and pharmacokinetics/pharmacodynamics (PK/PD) of CS2009 as monotherapy and combination regimens. The study comprises 15 monotherapy and combination therapy cohorts across 9 solid tumor indications, including NSCLC, CRC, TNBC, ES-SCLC, PROC, cervical cancer (CC), hepatocellular carcinoma (HCC), gastric or gastroesophageal junction cancer (GC/GEJC), and esophageal squamous cell carcinoma (ESCC). The trial is actively enrolling patients in Australia and China and has received IND clearance in the U.S.

Initial Phase I data for CS2009, previously presented at the 2025 European Society for Medical Oncology (ESMO) annual meeting, demonstrated a favorable safety profile with encouraging antitumor activities. Further clinical data from both the phase I and II is expected to be disclosed at the upcoming American Society of Clinical Oncology (ASCO) and ESMO congress later this year.

CStone, 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. To date, the Company has successfully launched 4 innovative drugs and secured approvals for 20 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.