STCube to Present Phase 1b Biomarker Analysis Results for Colorectal Cancer at ASCO GI in January

STCube announced on December 18 that two studies have been officially accepted for presentation at the ASCO GI (American Society of Clinical Oncology Gastrointestinal Cancers Symposium), the world’s largest academic conference in the field of gastrointestinal cancers. The accepted studies include the results of a Phase 1b clinical trial of Nelmastobart for metastatic colorectal cancer and a research abstract on a BTN1A1-based patient selection biomarker. ASCO GI will be held in San Francisco, USA, from January 8 to 10 next year (local time).

This presentation will introduce the validity and development value of a biomarker-based Phase 2 clinical strategy, based on key data on BTN1A1 expression and treatment response obtained from the Phase 1b trial in metastatic colorectal cancer.

Based on the results of the Phase 1b study, the researchers evaluated not only BTN1A1 expression but also its association with various tumor and immune-related biomarkers, including PD-L1, CD8, Ki-67, SLFN11, CK, and YAP1, thereby strengthening the biological rationale for a BTN1A1-based patient selection strategy.

STCube is currently conducting a Phase 1b/2 clinical trial of Nelmastobart in combination with trifluridine-tipiracil (TAS-102) and bevacizumab for metastatic colorectal cancer. The Phase 1b portion was conducted with all-comer patients, without BTN1A1 screening, and analysis showed that 5 out of 6 patients (83%) exhibited high BTN1A1 expression (TPS≥50). The ongoing Phase 2 trial is a biomarker-based study, enrolling only patients with BTN1A1 TPS (Tumor Proportion Score) ≥50.

No toxicity related to Nelmastobart was observed in the Phase 1b study, and encouraging results were seen in the initial response evaluation. Partial response (PR) was observed in 2 out of 5 patients with BTN1A1 TPS≥50, while the remaining patients exhibited decreasing stable disease (SD), indicating a trend toward tumor reduction. In the second tumor assessment conducted at the 4-month mark, all patients continued to benefit from the treatment, and no cases of progressive disease (PD) were reported.

An STCube representative explained, "BTN1A1 not only shows a high frequency of expression in metastatic colorectal cancer patients, but even higher expression levels are observed in third-line patients who have failed previous chemotherapy. Not only in this Phase 1b study but also in previous investigator-initiated trials, Nelmastobart has shown a clear treatment response in patients with high BTN1A1 expression. This data is being used as important evidence for designing the biomarker-based Phase 2 trial and for discussions on global collaboration."

STCube plans to share its BTN1A1-targeted immuno-oncology platform and clinical strategy for Nelmastobart with global pharmaceutical companies and researchers during ASCO GI 2026, continuing discussions for collaboration. In addition, the company will meet with major pharmaceutical companies at the JP Morgan Healthcare Conference, which will be held immediately after the symposium, to discuss specific partnership options and development strategies.