STCube "Confirmed Excellent Anticancer Effects in Metastatic Colorectal Cancer Researcher Clinical Trial"

STCube announced on the 10th that patient dosing for phase 1b of the investigator-initiated phase 1b/2 clinical trial of ‘Nelmastobart’ for colorectal cancer has been completed. Since improvement effects exceeding those of existing standard treatments have been confirmed in the dosed patient group, phase 2 is expected to proceed rapidly.

This clinical trial is an investigator-initiated phase 1b/2 study evaluating the efficacy and safety of Nelmastobart combined with capecitabine (brand name Xeloda, an oral cytotoxic chemotherapy) as a third-line treatment for metastatic colorectal cancer patients who have failed or are ineligible for second-line or higher standard chemotherapy (oxaliplatin and irinotecan).

The research team completed dosing up to the 12th patient about six months after the first patient dosing began in February. Currently, all 12 patients in phase 1b are undergoing dosing and follow-up observation. The recommended phase 2 dose (RP2D) was selected as Nelmastobart 800mg and capecitabine 1000mg/m2, which are expected to show high efficacy without drug-related adverse reactions.

Phase 2 will recruit 39 patients and dosing is planned to start soon. The primary endpoint of phases 1b/2 is progression-free survival (PFS) in the group receiving the combination of Nelmastobart and capecitabine.

The patients participating in the clinical trial are terminal colorectal cancer patients who have failed all previous treatments. Among them, the trial targets MSS/pMMR (microsatellite stable/proficient mismatch repair) colorectal cancer patients, known as representative immune checkpoint inhibitor-resistant tumors. MSS/pMMR colorectal cancer accounts for 95% of all metastatic colorectal cancer patients, but immune checkpoint inhibitors including Keytruda are ineffective, making this a field where combination clinical developments with immune checkpoint inhibitors are actively pursued.

For third-line treatment of colorectal cancer, the objective response rate (ORR) of existing standard treatments is only in the 1% range. Drugs such as regorafenib (brand name Stivarga), TAS-102 (brand name Lonsurf), and fruquintinib (brand name Fruzakla) are used, with progression-free survival ranging from 1.9 to 3.7 months and overall survival (OS) from 6.4 to 7.4 months. Fruquintinib received FDA approval in November 2023 with an ORR of 1.5% and PFS of 3.7 months.

An STCube representative stated, “Since patient enrollment for the colorectal cancer investigator-initiated trial is rapid, phase 2 is expected to proceed quickly in the second half of the year. Although the investigator-initiated trial has not yet concluded and results cannot be disclosed at this stage, tumor suppression effects have been confirmed in most patients, so encouraging results are expected in phase 2 as well.”

Nelmastobart is a first-in-class immune checkpoint inhibitor candidate targeting cancer cells expressing the BTN1A1 antigen. It has a mutually exclusive expression mechanism compared to existing PD-(L)1 immune checkpoint inhibitors such as Keytruda and is highly related to chemotherapy resistance, so it is expected to maximize therapeutic effects when combined with existing standard treatments.

This content was produced with the assistance of AI translation services.