CStone's CS2009 Trispecific Antibody Receives FDA Clearance for Phase II Trial
CStone Pharmaceuticals received FDA IND clearance to initiate a Phase II trial of CS2009, a PD-1/VEGF/CTLA-4 trispecific antibody, in patients with advanced solid tumors across nine cancer indications.
CS2009 (PD-1/VEGF/CTLA-4 trispecific antibody) has received Investigational New Drug (IND) clearance from the U.S. Food and Drug Administration (FDA) to initiate a Phase II clinical trial in patients with advanced solid tumors. This marks a significant milestone in the global development of this innovative immunotherapy.
The ongoing global multicenter Phase II trial is currently enrolling patients in Australia and China. The study design includes 15 cohorts evaluating both monotherapy and combination therapy regimens across 9 solid tumor indications, including but not limited to non-small cell lung cancer (NSCLC), colorectal cancer (CRC), triple-negative breast cancer (TNBC), extensive-stage small cell lung cancer (ES-SCLC), and platinum-resistant ovarian cancer (PROC). The trial also includes cervical cancer (CC), hepatocellular carcinoma (HCC), gastric or gastroesophageal junction cancer (GC/GEJC), and esophageal squamous cell carcinoma (ESCC).
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.
The Phase II clinical trial 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.
CS2009 is an innovative trispecific antibody designed and developed by CStone Pharmaceuticals (HKEX: 2616), 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.
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.