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Promising new immune checkpoint inhibitor for colorectal cancer

In New Zealand, colorectal cancer (CRC) is the most diagnosed cancer and the second most common cause of death due to cancer. Overall survival rates of people are highly variable even with advancements in therapy. One form of therapy, known as immune checkpoint inhibitors (ICI), aims to reinvigorate the immune response to help destroy tumour cells. However, immune checkpoint inhibitors have only been effective in people with microsatellite instable high or mismatch repair deficient CRC, which represent about 4% of CRC types. ICI therapy has been elusive for the more common form of CRC known as the microsatellite stable CRC.

In a recently concluded phase 1 clinical trial, a new ICI botensilimab (antiCTLA4) was used in conjunction with balstilimab (antiPD1) was studied for safety in patients with microsatellite stable CRC that were not responding to chemotherapy. The study involved 101 patients that were followed for 6 months after receiving therapy. Promisingly, 61% of the patients had some form of response (either tumour shrinkage or stable disease). Furthermore, the most common side effects reported by the patients in the study were diarrhoea and fatigue. The treatment modality has now entered into late-stage clinical trials.