This study is for people with colorectal cancer that has spread and cannot be removed by surgery. Researchers want to test if a new medicine, calderasib, along with another drug called cetuximab, helps when added to the usual treatment. Calderasib and cetuximab are targeted therapies, which means they aim at specific parts of cancer cells. This study has two parts and looks at how safe the new treatment is and whether it helps people live longer without the cancer growing.

• Participants must have a specific gene change called KRAS G12C.
• The study may involve receiving standard chemotherapy with added treatments.
• People with certain health conditions, such as severe heart disease or active infections, cannot join.

Eligibility includes having a confirmed diagnosis of advanced colorectal cancer and possibly having well-controlled HIV or hepatitis if applicable. Participants should not have had recent anticancer treatments or other serious health issues.