A Phase II Study of Immunotherapies (Tiragolumab and Atezolizumab) in Combination With Stereotactic Body Radiation Radiotherapy in Microsatellite Stable (MSS) Metastatic Colorectal Cancer (mCRC)

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Trial Details

Sponsor: National Cancer Institute (NCI) (federal)

Phase: 2

Start date: None

Planned enrollment: 36

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chevron Show for: Tiragolumab (MTIG7192A, RG6058, RO7092284)

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Trial ID: NCT06603818
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More trial details at ClinicalTrials.gov More info

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Goal: To evaluate the safety, recommended phase II dose, and preliminary efficacy of combining the immune checkpoint inhibitors tiragolumab (anti-TIGIT) and atezolizumab (anti-PD-L1) with stereotactic body radiation therapy (SBRT) in patients with MSS metastatic colorectal cancer, a population for whom immunotherapy alone has shown little benefit.

Patients: Adults (≥18 years) with histologically confirmed, microsatellite stable (MSS) metastatic colorectal cancer, ECOG performance status 0-1, who have progressed on at least two prior lines of systemic therapy. Patients must have at least two lesions (one amenable to SBRT, one non-irradiated for measurable disease) and adequate organ function. Key exclusions include prior checkpoint inhibitor exposure, ongoing immunosuppression, active autoimmune disease, or uncontrolled comorbidities.

Design: This is a single-arm, non-randomized phase II trial enrolling up to 36 participants. The trial includes a safety lead-in (to confirm RP2D) and efficacy assessment using a binary endpoint of 9-week progression-free survival.

Treatments: Participants receive atezolizumab and tiragolumab intravenously every 3 weeks for up to 2 years, combined with SBRT to a selected lesion on days 1, 3, and 5 of cycle 1. Tiragolumab is a fully human IgG1 antibody targeting TIGIT, an inhibitory receptor on T cells and NK cells that interacts with CD155. By blocking TIGIT, tiragolumab aims to enhance anti-tumor immunity. In phase II NSCLC data (CITYSCAPE trial), tiragolumab plus atezolizumab demonstrated improved response rates and PFS versus atezolizumab alone, although recent phase III trials have been negative in lung cancer. Its safety profile is generally manageable, with mostly grade 1/2 immune-related adverse events.

Outcomes: Primary outcomes include establishing the recommended phase II dose (RP2D) and the proportion of participants who are progression-free at 9 weeks. Secondary outcomes include safety and tolerability, best overall response rate (per RECIST 1.1), progression-free survival, and overall survival.

Burden on patient: The trial presents a moderate to high burden on participants. The regimen includes IV infusions every 3 weeks, SBRT over the first week, and frequent blood draws including mandatory collection every cycle. Imaging is required every 9 weeks. Baseline and on-treatment tumor biopsies are requested, with additional biopsies possible at progression. There is a significant time commitment per visit (approximately 8 hours) and potentially increased travel for radiation and frequent assessments. This intensity exceeds standard care for refractory mCRC.

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National Institutes of Health Clinical Center

Bethesda, Maryland, 20892, United States

[email protected] / 240-760-6050

Status: Recruiting

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