A new combination therapy has been found to give better results for patients with a certain type of colorectal cancer that no longer responds to chemotherapy.
Researchers at City of Hope conducted a Phase 3 clinical trial and discovered that combining two drugs—sotorasib and panitumumab—helped patients live longer without their disease getting worse. The results were published in the Journal of Clinical Oncology.
Earlier this year, the U.S. Food and Drug Administration (FDA) approved this combination to treat patients with metastatic colorectal cancer carrying the KRAS G12C mutation after chemotherapy stopped working.
In the new study, patients who received both drugs had longer periods where their cancer did not worsen compared to those who received standard treatments. There was also a trend toward longer overall survival in the combination therapy group.
KRAS is a gene that helps control how cells grow and divide. When it mutates, it can cause cancer. Up to 45% of people with colorectal cancer have some form of KRAS mutation, but only about 10% of those have the specific G12C mutation. This mutation makes the cancer harder to treat.
Sotorasib was the first drug developed to specifically target KRAS G12C. It works by locking onto the mutated protein and preventing it from signaling cancer cells to grow. Panitumumab is a different kind of drug called a monoclonal antibody. It blocks a protein known as EGFR, which also promotes cell growth and division and is often too active in cancers like colorectal cancer.
Previous research showed that sotorasib worked better when paired with panitumumab. Building on that, this new study, called CodeBreaK 300, tested the drug combination against the current standard treatments, which include trifluridine/tipiracil or regorafenib.
The trial included 160 patients whose cancer had already worsened despite earlier chemotherapy treatments like oxaliplatin and irinotecan.
Patients in the trial were divided into three groups. One group received a high dose (960 mg) of sotorasib plus panitumumab, another group received a lower dose (240 mg) of sotorasib plus panitumumab, and the third group received standard treatment.
Results showed that the higher dose of sotorasib led to better outcomes. About 30% of patients in the high-dose group saw their tumors shrink by more than half, compared to only about 2% of patients on standard treatments.
While the trial wasn’t designed to fully measure overall survival, early results were promising. Patients who got the higher dose of sotorasib lived about 30% longer than those who received standard care.
Dr. Marwan Fakih, who led the study, said this new combination therapy should become the new standard of care for these patients. He added that the success of this approach suggests it may be even more effective when used earlier in the treatment process, possibly alongside chemotherapy.
Side effects seen in the trial were mostly manageable. The most common included diarrhea, muscle and joint pain, nausea, tiredness, liver problems, and coughing.
Researchers are now conducting follow-up studies to see if the combination of sotorasib, panitumumab, and chemotherapy can be used as a first-line treatment for people newly diagnosed with KRAS G12C metastatic colorectal cancer.
This breakthrough offers new hope for patients with a cancer type that has been very hard to treat, and it marks another step forward in making cancer care more personalized based on a patient’s specific genetic makeup.
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The research findings can be found in Journal of Clinical Oncology.
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