Hong Kong – CStone Pharmaceuticals reported encouraging Phase I/II read-outs for its core asset CS2009, a PD-1/VEGF/CTLA-4 trispecific antibody, at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting. Two poster presentations detailed first-line and later-line performance in non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) as well as mature Phase I results across advanced solid tumours.

First-line NSCLC • In PD-L1 high-expression patients (TPS ≥50%, n = 16), CS2009 monotherapy produced an 81.30% objective response rate (ORR) and a 100.00% disease control rate (DCR); squamous histology registered an ORR of 87.50%, non-squamous 75.00%. • For PD-L1-negative/low squamous NSCLC (TPS ≤5%, n = 8), CS2009 plus chemotherapy delivered a 75.00% ORR and 100.00% DCR; the PD-L1-negative subgroup (TPS <1%) achieved a 100.00% ORR.

Later-line NSCLC • Across all dose levels in heavily pre-treated patients (n = 54), the 6-month duration-of-response rate reached 85.70%. • Combination with docetaxel in second/third-line disease (n = 6) achieved a 66.70% ORR and 100.00% DCR. • Monotherapy at 30 mg/kg in patients previously failing immunotherapy plus platinum chemotherapy (n = 13) yielded a 30.80% ORR and 84.60% DCR.

Colorectal Cancer • Monotherapy in later-line pMMR/MSS mCRC (n = 8 evaluable) generated a 25.00% ORR and 87.50% DCR. • First-line combination with XELOX (n = 6 evaluable) showed a 66.70% ORR and 100.00% DCR.

Other “Cold Tumours” Monotherapy signalled activity in soft-tissue sarcoma (ORR 33.33%, n = 12) and non-clear-cell renal cell carcinoma (ORR 33.33%, n = 6), supporting CS2009’s potential to remodel the tumour micro-environment.

Safety Profile Updated Phase I data (n = 118) reinforced tolerability: Grade ≥3 treatment-related adverse events (TRAE) occurred in 24.60%, immune-related adverse events in 12.70%, and TRAE possibly related to anti-VEGF activity in 5.10%. No dose-limiting toxicities were observed, and the maximum tolerated dose was not reached.

Pharmacokinetics/Pharmacodynamics CS2009 displayed linear pharmacokinetics with a 6–9-day half-life and saturated PD-1/CTLA-4 receptor occupancy at doses ≥20 mg/kg, alongside deep and sustained VEGFA neutralisation.

Next Steps Nearly 300 patients have been enrolled across China and Australia, and U.S. IND clearance has been obtained. CStone targets initiation of a global Phase III multi-regional registrational trial for CS2009 by end-2026, focusing on NSCLC, CRC and additional solid-tumour indications.

Regulatory Reminder The company cautions that successful development and commercialisation of CS2009 remains subject to clinical and regulatory outcomes, and advises investors to exercise caution in securities dealings.