CStone Pharmaceuticals, the Suzhou-based oncology company listed on the Hong Kong Stock Exchange, reported Phase I/II data for its CS2009 trispecific antibody targeting PD-1, VEGF, and CTLA-4 in patients with advanced solid tumors, according to a voluntary disclosure filed on March 26, 2026. The company said that CS2009 monotherapy achieved an overall response rate of 90% (9 of 10 patients) and a disease control rate of 100% in first-line non-small cell lung cancer patients with PD-L1 tumor proportion scores of 50% or greater in the Phase II portion of the trial. In the Phase I dose-escalation portion, 113 patients with advanced solid tumors were enrolled across six dose levels, with a median follow-up of approximately six months. The company reported no dose-limiting toxicities and stated that the maximum tolerated dose was not reached. Grade 3 or higher treatment-related adverse events occurred in 23% of patients, grade 3 or higher immune-related adverse events in 12.4%, and grade 3 or higher VEGF-related adverse events in 4.4%. In IO-pretreated, AGA-negative second- or later-line NSCLC patients receiving 30 mg/kg every three weeks, the ORR was 25% (6 of 24) and the DCR was 58.3% (14 of 24). Responses were also reported in non-clear cell renal cell carcinoma (ORR 40%, n=5) and soft tissue sarcoma (ORR 33.3%, n=9).
The Phase I/II trial is a global multi-center study conducted in Australia and China, with the Phase II portion employing a multi-cohort parallel expansion design evaluating CS2009 monotherapy and combination therapy across 15 cohorts in nine solid tumor types. Eighty-five patients have been enrolled in Phase II. The company did not disclose primary endpoints, duration of response, progression-free survival, or overall survival data. The first-line NSCLC monotherapy cohort included only 10 evaluable patients. Subgroup sample sizes for Phase I efficacy signals in nccRCC and STS were five and nine patients, respectively. No information on blinding, randomization, or independent data monitoring was provided. The data are interim and are based on subsets of enrolled patients; the company did not disclose whether responses were confirmed by independent radiological review. CStone said it plans to initiate Phase III global multi-regional clinical trials by the end of 2026 in NSCLC, colorectal cancer, and small cell lung cancer, and expects to present updated data at the 2026 ASCO and/or ESMO meetings.
CS2009 is designed to simultaneously engage three targets in a single molecule. The established dual-pathway combination of nivolumab plus ipilimumab (PD-1 and CTLA-4 blockade) achieved a five-year overall survival rate of 52% in metastatic melanoma in the CheckMate 067 trial, while bevacizumab plus atezolizumab (VEGF and PD-L1 blockade) demonstrated an overall survival hazard ratio of 0.58 versus sorafenib in hepatocellular carcinoma in IMbrave150. Cross-trial comparisons are limited by differences in study design, duration, and patient populations.
Spot something wrong? Report an issue with this article