A Study to Test Different Doses of BI 1701963 in Combination With Irinotecan in People With Advanced Bowel Cancer With Kirsten Rat Sarcoma Viral Oncogene Homologue (KRAS) Mutation

This study is open to adults with advanced bowel cancer (colorectal cancer) with a KRAS mutation. This is a study in people for whom previous treatment was not successful and surgery is not a treatment option. The purpose of this study is to find the highest dose of BI 1701963 that people with bowel cancer can tolerate when taken together with a medicine called irinotecan. The study also tests whether BI 1701963 in combination with irinotecan is able to make tumours shrink. BI 1701963 may help to turn off KRAS. Activating KRAS mutations make tumours grow. Irinotecan is a medicine to treat bowel cancer. Participants can stay in the study as long as they benefit from treatment and can tolerate it. During this time, participants take BI 1701963 as tablet once a day and get irinotecan as infusion every two weeks. The doctors regularly monitor the size of the tumour. The doctors also collect information on any health problems of the participants.