New colorectal cancer treatment trial successful

A recent phase 1 clinical trial has revealed promising results, suggesting that immunotherapy may be an effective treatment for the most prevalent form of colorectal cancer, also known as bowel cancer. This groundbreaking study, published in Nature Medicine, demonstrated that a significant percentage of patients with microsatellite stable metastatic colorectal cancer (MSS mCRC) responded positively to a combination of two immunotherapy drugs, botensilimab and balstilimab.

In the trial, which involved patients from the United States, 61% of participants experienced either a reduction in tumor size or no further tumor progression after undergoing the combined treatment for six months. These findings are particularly noteworthy because, until now, immunotherapy has had limited success in treating MSS mCRC, a common type of colorectal cancer that typically does not respond well to such treatments.

The study was co-authored by Professor Justin Stebbing of Anglia Ruskin University (ARU), who hailed the results as potentially transformative. Stebbing emphasized the significance of these findings, noting that this is the first time consistent and durable responses to immunotherapy have been observed in difficult-to-treat colorectal cancer patients. He expressed optimism that these results could lead to expedited approval of the treatment by health authorities in both the United States and the United Kingdom.

The trial's success is particularly important because it expands the potential applicability of immunotherapy beyond the small subset of colorectal cancer patients who have mismatch repair deficient (dMMR) tumors, which have previously been shown to respond to such treatments. MSS mCRC patients, who make up the majority of colorectal cancer cases, have not benefited from immunotherapy until now.

Botensilimab and balstilimab are both monoclonal antibodies that stimulate the body's immune system to target and destroy cancer cells. The phase 1 trial included 101 patients, with the most common side effects reported being diarrhea and fatigue. These side effects were considered manageable in light of the substantial therapeutic benefits observed.

Dr. Andrea Bullock, Assistant Professor in Medicine at Beth Israel Deaconess Medical Center and joint first author of the study, highlighted the potential impact of the BOT/BAL combination therapy. She noted that this approach might offer new hope to patients with MSS mCRC, a group that has historically seen limited success with immunotherapy treatments.

Dr. Anthony El-Khoueiry, Associate Director of Clinical Research and Chief of Section of Developmental Therapeutics at the USC Norris Comprehensive Cancer Center, and joint last author of the study, also underscored the significance of the findings. He pointed out that the trial's results demonstrate botensilimab's promising anti-tumor activity, even in immunologically cold tumors like MSS colorectal cancer. According to El-Khoueiry, the observed efficacy of botensilimab is a testament to its potential to engage the body's broader anti-tumor immune responses.

Overall, the trial's results mark a significant step forward in the treatment of colorectal cancer, offering a new avenue of hope for patients with MSS mCRC. As the treatment progresses into later-phase clinical trials, there is cautious optimism that regulatory authorities will soon approve its use, providing a new lifeline for many colorectal cancer patients worldwide.