Chugai Pharmaceutical has submitted a regulatory application to Japan’s Ministry of Health, Labour and Welfare (MHLW) seeking an additional indication for Tecentriq Intravenous Infusion 840 mg (atezolizumab) as adjuvant treatment for adults and paediatric patients with microsatellite instability-high (MSI-High) colon cancer.

The application is supported by results from the global, investigator-initiated Phase 3 ATOMIC trial (Alliance A021502), which evaluated Tecentriq in patients with pathological Stage 3 deficient mismatch repair (dMMR) colon cancer following curative surgical resection.

The study assessed the addition of Tecentriq to standard adjuvant modified FOLFOX6 (mFOLFOX6) chemotherapy. Results for the primary endpoint of Disease-Free Survival (DFS) showed a three-year DFS rate of 86.3 percent in patients receiving the Tecentriq combination, compared with 76.2 percent  among those receiving mFOLFOX6 alone.

The Tecentriq combination produced a statistically significant improvement in DFS, reducing the risk of disease recurrence or death by approximately 50 percent  compared with chemotherapy alone. The stratified hazard ratio was 0.50, with a 95 percent confidence interval of 0.35–0.73 and p<0.001.

The safety findings were consistent with the established safety profile of Tecentriq, with no new safety signals identified. The most frequently reported adverse events in the combination arm included hepatic dysfunction at 43.9 percent, skin disorders at 33.8 percent and hypothyroidism at 18.8 percent.

The ATOMIC study is being conducted by the Alliance for Clinical Trials in Oncology, a US National Cancer Institute-supported research group. It is an open-label, randomised Phase 3 study comparing six months of standard mFOLFOX6 chemotherapy with a combination regimen of mFOLFOX6 plus Tecentriq for six months, followed by Tecentriq monotherapy for another six months.

The findings are significant for patients with dMMR colon cancer, a molecular characteristic associated with MSI-High tumours. Impairment of the DNA mismatch repair system can lead to the accumulation of genetic mutations in tumour cells, potentially making these cancers more responsive to immune checkpoint inhibitors.

In Japan, colorectal cancer is the country’s most commonly diagnosed cancer. Approximately 154,000 new colorectal cancer cases were reported in 2023, while around 54,000 deaths were recorded in 2024. An estimated 6–7 percent of colorectal cancer cases in Japan are associated with dMMR.

For patients with pathological Stage 3 colorectal cancer, adjuvant chemotherapy is a standard treatment approach. However, recurrence can still occur in approximately 30 percent of patients after treatment, highlighting the need for additional therapeutic options that can reduce the risk of disease returning following curative surgery.

Tecentriq is a humanised anti-PD-L1 monoclonal antibody and immune checkpoint inhibitor. It is designed to block interactions involving PD-L1 and receptors on T cells, helping restore T-cell activity and strengthen the immune response against tumour cells.

In Japan, Tecentriq was launched in April 2018 and has subsequently received approval across seven tumour types, including extensive-stage small-cell lung cancer, non-small-cell lung cancer, breast cancer, hepatocellular carcinoma, alveolar soft part sarcoma, extranodal natural killer/T-cell lymphoma of the nasal type and thymic carcinoma.

Chugai said it will continue efforts to secure regulatory approval and expand treatment options for patients with MSI-High colon cancer.

Separately, the US Food and Drug Administration (FDA) has granted Priority Review to the Tecentriq application for the relevant indication, with a regulatory decision expected by October 9, 2026.