CStone Pharmaceuticals (CStone) released a voluntary update on the clinical progress of its self-developed trispecific antibody CS2009 (PD-1/VEGF/CTLA-4), highlighting an improved safety profile, compelling early-stage efficacy and an accelerated late-stage development plan.
Clinical programme snapshot • Enrolment: 113 heavily pretreated solid-tumour patients in the global Phase I study (median follow-up ≈ six months) and 85 patients in the ongoing multi-cohort Phase II expansion. • Regulatory status: Phase II Investigational New Drug application approved by the U.S. FDA; multi-regional Phase III trials targeted to begin by end-2026 in non-small cell lung cancer (NSCLC), colorectal cancer (CRC) and small cell lung cancer (SCLC).
Safety highlights (Phase I) • No dose-limiting toxicities observed across six dose levels; maximum tolerated dose not reached. • Grade ≥3 treatment-related adverse events occurred in 23% of patients; Grade ≥3 immune-related AEs in 12.40% and VEGF-related AEs in 4.40%. • Toxicities commonly associated with CTLA-4/PD-(L)1 combinations were not seen at excessive levels.
Efficacy signals 1. NSCLC – First-line, PD-L1 TPS ≥ 50%: CS2009 monotherapy delivered a 90% overall response rate (9/10) and 100% disease control rate. – IO-pretreated, AGA-negative, second/later line (30 mg/kg Q3W): ORR 25% (6/24) and DCR 58.33%.
2. “Cold” tumours – Non-clear cell renal cell carcinoma: ORR 40% and DCR 100% (n=5). – Soft-tissue sarcoma: ORR 33.33% and DCR 66.67% (n=9).
3. Combination cohorts (initial Phase II read-outs) – Early data indicate that adding CS2009 to standard chemotherapy in first-line NSCLC and first-line CRC maintains tolerability without increasing chemotherapy-related toxicity, while showing preliminary antitumour activity (numerical details pending conference disclosure).
Next milestones • Additional Phase I/II data will be presented at the 2026 ASCO Annual Meeting and/or ESMO Congress. • The first wave of global Phase III MRCTs is scheduled to launch by end-2026, focusing on NSCLC, CRC and SCLC.
CS2009 profile The investigational trispecific antibody targets PD-1, VEGFA and CTLA-4 simultaneously, aiming to combine T-cell exhaustion reversal, enhanced T-cell activation and anti-angiogenic effects within the tumour micro-environment.
CStone cautioned that successful development and commercialisation of CS2009 remain subject to clinical outcomes and regulatory review. Shareholders and potential investors are advised to exercise caution when dealing in the company’s securities.