STCube Completes 100% Patient Enrollment for Phase 1b/2 Clinical Trial in Metastatic Colorectal Cancer

STCube, a precision medicine-based immuno-oncology company, announced on January 15 that it has completed patient enrollment for the Phase 1b/2 clinical trial of its BTN1A1 inhibitor, Nelmastobart, targeting metastatic colorectal cancer (mCRC). A total of 61 patients have been recruited approximately seven months after the first dosing began, and the treatment is now in full progress.

A representative from STCube stated, "The colorectal cancer clinical trial has now entered the full Phase 2 data accumulation stage," adding, "With rapid patient enrollment at five university hospitals, the trial is proceeding on schedule without any setbacks."

Nelmastobart is a first-in-class immune checkpoint inhibitor targeting the novel immune checkpoint BTN1A1. Biomarker-based clinical development is underway to explore new treatment possibilities in solid tumors with high BTN1A1 expression, particularly those with limited response to existing immunotherapies. The company is currently focusing its strategic development on indications such as metastatic colorectal cancer and non-small cell lung cancer.

This clinical trial evaluates the combination therapy of Nelmastobart, TAS-102, and bevacizumab in metastatic colorectal cancer patients who have received at least third-line treatment and have a BTN1A1 TPS (Tumor Proportion Score) of 50 or higher. The aim is to demonstrate greater clinical benefit compared to the current standard therapies, TAS-102 and bevacizumab, which have shown the best clinical outcomes to date.

Results from the Phase 1b evaluation showed that the Nelmastobart combination therapy demonstrated excellent safety and tolerability. The most common adverse events were leukopenia and neutropenia associated with chemotherapy, with no observed correlation to Nelmastobart.

Notably, all six patients who participated in the Phase 1b trial exhibited tumor reduction. Two patients achieved partial response (PR), while four had stable disease (SD) with tumor shrinkage. Among the BTN1A1 TPS 50 or higher patient group (n=5), the objective response rate (ORR) was 40%, and the disease control rate (DCR) reached 100%. Furthermore, in most patients, the third treatment response assessment conducted at six months post-dosing showed continued response without disease progression, confirming cases with progression-free survival (PFS) of at least six months.

A company representative explained, "In patients with metastatic colorectal cancer who have received at least third-line treatment, the median progression-free survival (mPFS) for existing treatment options is only about two to three months on average. In contrast, patients with high BTN1A1 expression are experiencing not just short-term responses but sustained therapeutic effects." The representative added, "This durability of response is a highly meaningful sign of Nelmastobart's potential."

The representative continued, "Currently, nearly half of the patients eligible for Phase 2 evaluation have completed their first tumor assessment at two months post-treatment, and data will continue to accumulate as treatment progresses." The company is focusing on demonstrating the clinical value of Nelmastobart and, based on growing interest in the collected data, is accelerating discussions for global technology transfer and joint development."