FDA clears Phase II study of CStone Pharmaceuticals’ trispecific antibody
Original story from CStone Pharmaceuticals (Suzhou, China)
US FDA’s IND clearance advances CStone Pharmaceuticals’ CS2009 (PD-1/VEGF/CTLA-4 trispecific antibody) into Phase II development, expanding multispecific immunotherapy in solid tumors.
CStone Pharmaceuticals, 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 US FDA has cleared the IND application to initiate a Phase II clinical trial of its core asset, CS2009, in patients with advanced solid tumors.
This clearance 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
- Colorectal cancer
- Triple-negative breast cancer
- Extensive-stage small-cell lung cancer
- Platinum-resistant ovarian cancer
Initial Phase I data for CS2009, previously presented at the 2025 European Society for Medical Oncology (ESMO; Lugano, Switzerland) 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 (VA, USA) and ESMO congress later this year.
Jason Yang, 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.”
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About CS2009
CS2009, 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.
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