STCube Achieves Results Surpassing Standard Treatment in Metastatic Colorectal Cancer

mPFS of 6.3 Months Observed in BTN1A1 High-Expression Group

STCube confirmed a median progression-free survival (mPFS) of 6.3 months in the BTN1A1 high-expression patient group from an investigator-initiated clinical trial in patients with metastatic colorectal cancer. This result exceeds the existing standard treatment outcome of approximately 2 to 3 months mPFS. This suggests that the BTN1A1-targeting strategy could emerge as a new alternative for precision immunotherapy in colorectal cancer.

STCube released its research findings on October 13 through an abstract scheduled to be presented at the European Society for Medical Oncology (ESMO 2025) in Berlin, Germany, on October 17 (local time). The disclosed abstract includes both clinical and preclinical results of BTN1A1-targeted therapy for colorectal cancer and non-small cell lung cancer.

There are two research abstracts, each covering: ▲ Enhancement of standard treatment efficacy in non-small cell lung cancer and colorectal cancer through BTN1A1-targeted immunotherapy ▲ Analysis of BTN1A1 H-Score and multiple biomarkers to predict clinical benefits of the combination therapy of Nelmastobat and Capecitabine (Phase 1b/2 study in metastatic colorectal cancer). Nelmastobat is a first-in-class BTN1A1 inhibitor currently being developed by STCube.

Yoo Seunghan, Chief Scientific Officer of STCube, stated, "We observed a specific phenomenon where BTN1A1 expression increases in both non-small cell lung cancer and colorectal cancer following chemotherapy." He added, "When Nelmastobat was combined with chemotherapy, it demonstrated superior antitumor effects compared to monotherapy," and explained, "Significant results were observed in PD-L1 negative tumors with high BTN1A1 expression."

The results of immunohistochemistry (IHC) analysis from the investigator-initiated Phase 1b/2 clinical trial of Nelmastobat and Capecitabine combination therapy in metastatic colorectal cancer were also released. In the BTN1A1 H-Score 250 or higher group (high-expression group, n=3), an mPFS of 6.3 months was observed. In the BTN1A1 H-Score 150-249 group (n=7) and the less than 150 group (n=15), the mPFS was 4.2 months and 4.0 months, respectively. No new safety issues were observed in these patients, and the combination therapy demonstrated generally good tolerability.

Professor Lee Suhyeon of the Department of Oncology at Korea University Anam Hospital, who conducted the clinical trial, stated, "Among 25 patients with refractory or metastatic colorectal cancer, IHC analysis showed that patients with high BTN1A1 H-Score, as well as higher proportions of YAP1 (related to chemotherapy resistance), SLFN11 (related to sensitivity to DNA-damaging agents), and Ki-67/PD-L1 dual-expression cells (related to cell proliferation and immunosuppression), tended to have longer progression-free survival."

He explained, "This suggests that BTN1A1, based on its correlation with other indicators, can be utilized as a precise predictive biomarker for efficacy."

He added, "The combination therapy of Nelmastobat and Capecitabine demonstrated promising clinical efficacy and safety in heavily pretreated metastatic colorectal cancer patients. The BTN1A1 inhibition strategy offers a new treatment option through immunomodulation and holds potential for expansion as a precision immunotherapy."