A New Era in Colorectal Cancer: FDA Approves Nivolumab Plus Ipilimumab

On April 8, 2025, the US Food and Drug Administration (FDA) approved, for adults and pediatric patients aged 12 and older with unresectable or metastatic microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) disease, the treatment of colorectal cancer (CRC) with nivolumab (Opdivo) plus ipilimumab (Yervoy) .

The FDA also converted the earlier accelerated approval of single-agent nivolumab to full approval for MSI-H or dMMR metastatic CRC progressing after fluoropyrimidine, oxaliplatin, and irinotecan treatment.

MSI-H (Microsatellite Instability-High) and dMMR (Mismatch Repair Deficiency)indicate impaired cellular DNA repair. In certain cancers, these biomarkers make tumors more susceptible to immune attack and suggest a better response to immunotherapies . Approximately 5-15% of colorectal cancers are MSI-H (microsatellite instability-high) or dMMR (mismatch repair-deficient).

Colorectal cancer (CRC) is among the most common cancers worldwide in both incidence and mortality. Standard chemotherapy often produces limited responses in advanced, unresectable, or metastatic disease. In recent years, however, striking immunotherapy activity in this patient group has driven major changes in treatment.

FDA Approval Based on CHECKMATE-8HW

Trial Design

This FDA approval was based on results published on November 27, 2024, in NEJM from CHECKMATE-8HW , an open-label, three-arm, randomized phase 3 trial. It included patients with advanced CRC who had not previously received immune checkpoint inhibitors and whose MSI-H or dMMR status was centrally confirmed.

Patients were randomized to three arms:

1. Nivolumab + ipilimumab:

   • Nivolumab 240 mg every 3 weeks + ipilimumab 1 mg/kg every 3 weeks (up to 4 doses), followed by nivolumab 480 mg every 4 weeks.

2. Single-agent nivolumab:

   • Nivolumab 240 mg every 2 weeks for 6 doses, followed by 480 mg every 4 weeks.

3. Investigator's choice of standard chemotherapy.

1st-Line Combination Treatment: 4 Times Longer PFS

The first-line analysis included 255 patients with centrally confirmed MSI-H/dMMR. Nivolumab + ipilimumabshowed statistically significant superiority over chemotherapy:

• Median progression-free survival (PFS):

  • Combination arm: Not yet reached (95% CI: 38.4 months – not estimable)

  • Chemotherapy arm: 5.8 months (95% CI: 4.4 – 7.8 months)

• Hazard ratio (HR): 0.21 (95% CI: 0.14 – 0.32) → 79% reduction in the risk of progression!

• p-value: <0.0001 (highly significant)

These results show that, compared with chemotherapy, combination immunotherapy provided PFS 4 times as long .

Combination Versus Nivolumab Alone Across Treatment Lines

The second analysis included 582 patients. Combination treatment showed important differences compared with nivolumab alone:

• Median PFS:

  • Combination: Not yet reached (95% CI: 53.8 months – not estimable)

  • Nivolumab alone: 39.3 months (95% CI: 22.1 – not estimable)

• Hazard ratio (HR): 0.62 (95% CI: 0.48 – 0.81) → 38% reduction in the risk of progression.

• p-value: 0.0003

• Objective response rate (ORR):

  • Combination: 71% (95% CI: 65% – 76%)

  • Nivolumab: 58% (95% CI: 52% – 63%)

  • p-value: 0.0011 → Significant superiority

Safety Profile: Manageable, Expected Adverse Effects

Combination Treatment (Nivolumab + Ipilimumab)

• Most common adverse effects (≥20%):

  • Fatigue

  • Diarrhea

  • Itching (pruritus)

  • Abdominal pain

  • Musculoskeletal pain

  • Nausea

Single-Agent Nivolumab

• Most common adverse effects (≥20%):

  • Fatigue

  • Diarrhea

  • Abdominal pain

  • Itching

  • Musculoskeletal pain

Immune-mediated adverse events specific to immunotherapy require careful monitoring. Overall, however, these treatments have a manageable safety profile.

Why Does This Approval Matter?

Because tumors carrying MSI-H or dMMR biomarkers are more susceptible to immune attack, patients with colorectal cancer may derive substantial benefit from immunotherapy. With this FDA approval:

• Immunotherapy has become a standard first-line option for MSI-H/dMMR colorectal cancer .

• Both adult and pediatric patients can benefit from this new treatment option.

• Combination immunotherapy offers important advantages in progression-free survival and response rates.

Conclusion and Future Perspectives

This approval is a milestone that fundamentally changes immunotherapy's role in colorectal cancer treatment. Particularly where chemotherapy has limited benefit, the potential for prolonged tumor control makes this combination a promising option for oncologists and patients.