This study tests a new medicine, **B07**, to help people with **metastatic colorectal cancer** (a type of cancer that has spread) maintain their weight and muscle during chemotherapy, a treatment that uses drugs to kill cancer cells. **B07** is given daily through a shot under the skin and is tested against a **placebo** (a harmless substance) to see if it works. The study includes up to 120 participants and lasts for 12 weeks, starting with their second cycle of chemotherapy. The main goal is to keep weight and muscle steady. *Key Points:* - The study lasts 12 weeks and involves daily self-injections or injections by a caregiver. - Participants must have a BMI (Body Mass Index) of 29 or less and be starting specific chemotherapy treatments. - You must be over 18, able to eat normally, and meet other health criteria to join. If you qualify and are interested, you’ll need to attend regular visits and agree to use contraception if you’re able to have children. Participants must also sign an informed consent form.