FDA Grants Priority Review to Adjuvant Atezolizumab Plus Chemotherapy for Stage III dMMR Colon Cancer

The FDA has accepted and granted priority review to the supplemental biologics license application (sBLA) for atezolizumab (Tecentriq) and atezolizumab/hyaluronidase-tqjs (Tecentriq Hybreza) in combination with chemotherapy as adjuvant treatment for patients with stage III mismatch repair–deficient (dMMR) or microsatellite instability–high (MSI-H) colon cancer following surgical resection.¹

The FDA has set a target action date of October 9, 2026, for the application under the Prescription Drug User Fee Act (PDUFA). If approved, the combination would represent the first immunotherapy-based adjuvant regimen available for this molecularly defined patient population.

The sBLA is supported by results from the phase 3 Alliance ATOMIC trial (NCT02912559), in which adding atezolizumab to modified (m) FOLFOX-6 (leucovorin calcium [folinic acid], fluorouracil, and oxaliplatin) reduced the risk of disease recurrence or death by 50% compared with chemotherapy alone in patients with stage III dMMR colon cancer (HR, 0.50; 95% CI, 0.35-0.73; P < .001).^1,2 Findings published in the New England Journal of Medicine showed that, at a median follow-up of 40.9 months (IQR, 26.7-58.6), the atezolizumab regimen produced a 36-month disease-free survival (DFS) rate of 86.3% (95% CI, 81.8%-89.8%) vs 76.2% (95% CI, 70.9%-80.6%) in the chemotherapy alone arm.

“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,” Levi Garraway, MD, PhD, Roche’s chief medical officer and head of global product development, stated in a news release.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.”

How was the ATOMIC trial designed?

ATOMIC is a randomized, open-label, multicenter study evaluating the addition of atezolizumab to mFOLFOX-6 chemotherapy in patients aged 12 or older with stage III colon cancer harboring dMMR, as determined by immunohistochemistry testing. The trial enrolled 712 patients across 312 sites between September 2017 and January 2023; these patients were randomly assigned 1:1 to one of 2 arms:

• Experimental arm (n = 355): mFOLFOX-6 plus atezolizumab (840 mg intravenous every 2 weeks) for 12 cycles (6 months), followed by atezolizumab monotherapy for an additional 13 cycles (6 months).
• Control arm (n = 357): mFOLFOX-6 alone for 12 cycles.

Of note, 1 cycle of mFOLFOX-6 was allowed pre-enrollment.² No other prior chemotherapy or radiation exposure was permitted.

Baseline characteristics and stratification variables were well balanced between groups. The median age was 64 years (range, 49.0-72.0); 55.1% of the patients were women, and 83.7% had proximal tumors. Overall, 46.1% had clinically low-risk tumors (Tx, T1, T2, or T3; N1 or N1c) and 53.9% had high-risk tumors (T4, N2, or both).

The study’s primary end point was DFS.^1,2 Secondary end points included overall survival (OS) and safety.²

What additional OS and safety data were reported from ATOMIC?

At the February 4, 2025, data cutoff, with a median OS follow-up of 45.8 months (IQR, 32.0-64.7), there was no statistically significant difference in OS by study arm (stratified log-rank P = .6787).² The 5-year OS rate was 89.7% (95% CI, 85.2%-92.9%) for atezolizumab plus mFOLFOX-6 vs 87.9% (95% CI, 83.1%-91.4%) for mFOLFOX-6 alone (stratified HR, 0.90; 95% CI, 0.55-1.47).

The safety profile of atezolizumab combined with FOLFOX-6 in ATOMIC was described as consistent with that observed in previous studies of atezolizumab and mFOLFOX-6.¹ Any-grade adverse effects (AEs) occurred at similar rates in both arms, at 100% vs 98.5%, respectively. Regardless of attribution, atezolizumab plus mFOLFOX-6 had a higher incidence of grade 3/4 AEs than mFOLFOX-6 alone (84.1% vs 71.9%), as well as higher rates of nonhematologic toxicities (69.4% vs 54.5%), such as fatigue (10.1% vs 3.3%). Grade 3/4 hematological toxicities were reported in 46.8% of patients in the atezolizumab plus mFOLFOX-6 arm vs 38.6% in the mFOLFOX-6 arm. A higher rate of grade 3/4 neutrophil count decrease occurred in the atezolizumab plus mFOLFOX-6 arm than in the mFOLFOX-6 arm (43.6% vs 35.9%).

What is next for adjuvant atezolizumab in colon cancer?

In addition to the current sBLA, Roche has stated its intention to pursue additional regulatory filings for atezolizumab in the adjuvant dMMR/MSI-H colon cancer indication, including a submission to the European Medicines Agency.¹

“One in 3 patients with stage III colon cancer will relapse within 5 years, underscoring the need for new adjuvant treatment options,” Michael Sapienza, CEO of the Colorectal Cancer Alliance, concluded in the news release. “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 11, 2026. Accessed June 11, 2026. https://www.roche.com/media/releases/med-cor-2026-06-11
2. Sinicrope FA, Ou FS, Arnold D, et al. Atezolizumab plus FOLFOX for stage III mismatch repair–deficient colon cancer. N Engl J Med. 2026;394(12):1155-1166. doi:10.1056/NEJMoa2507874