Atezolizumab/Chemo Earns FDA Priority Review in Stage III dMMR/MSI-H Colon Cancer

The FDA has accepted and granted priority review to a supplemental biologics license application (sBLA) for atezolizumab (Tecentriq) and atezolizumab and hyaluronidase-tqjs (Tecentriq Hybreza) in combination with chemotherapy as adjuvant treatment of stage III deficient DNA mismatch repair (dMMR) or microsatellite instability–high (MSI-H) colon cancer, according to a news release from the developer, Roche.¹ The agency is expected to make an approval decision by October 9, 2026.

The application is supported by data from the landmark phase 3 ATOMIC trial (NCT02912559), which previously demonstrated a 50% reduction in the risk of disease recurrence or death with adjuvant atezolizumab plus chemotherapy vs chemotherapy alone in patients with resected stage III dMMR colon cancer.² In the intent-to-treat population at a median follow-up of 40.9 months, the 3-year disease-free survival (DFS) rate was 86.4% in the atezolizumab plus chemotherapy arm compared with 76.6% in the chemotherapy-alone arm. Full results from ATOMIC were subsequently published in The New England Journal of Medicine earlier this year, cementing that this regimen may be a potential new standard of care in this molecularly defined population.³

“This filing acceptance brings us closer to establishing adjuvant [atezolizumab] plus chemotherapy as a new standard of care for certain types of early colon cancer,” said Levi Garraway, MD, PhD, chief medical officer and head of global product development at Roche.¹ “The ATOMIC results demonstrate that [atezolizumab] plus chemotherapy can substantially reduce the risk of disease recurrence or death, helping more patients remain cancer free following surgery.”

ATOMIC enrolled 712 patients across more than 300 sites in the National Clinical Trials Network. Eligible patients had resected stage III colon cancer with dMMR status confirmed by immunohistochemistry, an ECOG performance status of 2 or less, and no prior chemotherapy or radiation. Patients were randomly assigned 1:1 to receive atezolizumab plus mFOLFOX6 (leucovorin, fluorouracil, and oxaliplatin) for 12 cycles (6 months) followed by atezolizumab monotherapy for an additional 13 cycles (6 months), or mFOLFOX6 alone for 12 cycles. The primary end point was DFS.

The safety profile of the combination was consistent with that observed in prior studies of atezolizumab and FOLFOX6. Grade 3 and 4 adverse events (AEs) were noted in 84.1% of the experimental arm and 71.9% of the control arm, with nonhematologic AEs consisting of 69.4% and 54.5% of those, respectively. The most common grade 3 or 4 AEs in the experimental arm were decreased neutrophil count (43.6%), peripheral sensory neuropathy (18.5%), and diarrhea (12.1%).

Grade 3 and 4 treatment-related AEs were noted in 72.5% and 61.7% of patients in the experimental and control arms, respectively. Notably, 6 patients in the atezolizumab plus chemotherapy group and 2 patients in the chemotherapy alone group experienced grade 5 events. In the combination arm, 2 of the deaths (sudden death and sepsis) were deemed by the investigators to be related to treatment.

The sBLA covers both the intravenous formulation and the subcutaneous formulation, which collectively represent the first PD-(L)1 cancer immunotherapy available in both delivery forms. The developer has indicated it will pursue additional regulatory filings internationally, including with the European Medicines Agency, to expand access to this adjuvant option for patients with dMMR/MSI-H stage III colon cancer worldwide.

“One in 3 patients with stage III colon cancer will relapse within 5 years, underscoring the need for new adjuvant treatment options,” stated Michael Sapienza, chief executive officer of the Colorectal Cancer Alliance, in the press release.¹ “This milestone represents a critical step toward a reality where treatment is tailored to a patient’s specific tumor biology from the very beginning, giving them a better chance of preventing a recurrence.”

References

1. FDA grants priority review for Roche's Tecentriq for a certain type of stage III colon cancer. News release. Roche. June 10, 2026. Accessed June 11, 2026. https://tinyurl.com/ybye9md4
2. Sinicrope FA, Ou F-S, Arnold D, et al. Randomized trial of standard chemotherapy alone or combined with atezolizumab as adjuvant therapy for patients with stage III deficient DNA mismatch repair (dMMR) colon cancer (Alliance A021502; ATOMIC). J Clin Oncol. 2025;43(suppl 17):LBA1. doi:10.1200/JCO.2025.43.17_suppl.LBA1
3. Sinicrope FA, Ou F-S, Arnold D, et al. Atezolizumab plus FOLFOX for stage III mismatch repair-deficient colon cancer. N Engl J Med. 2026;394(12):1115-1126. doi:10.1056/NEJMoa2507874