This study looks at whether a medicine called **dupilumab** can help adults who have had severe itching, called **chronic pruritus of unknown origin (CPUO)**, for at least 6 months. Chronic pruritus means having an itch that doesn't go away, and "unknown origin" means doctors don't know why it's happening. In this study, there are two parts: **Study A** and **Study B**. Participants will be randomly chosen to get either dupilumab or a fake medicine called a placebo, both alongside antihistamines (medicine to help with allergies) and moisturizers to soothe their skin. **Study A** lasts up to **44 weeks**, and **Study B** lasts up to **32 weeks**, including a follow-up period to check on participants.

• Participants must be between **18 to 90 years old** and have severe itch (rating of 7 or more out of 10).
• Each participant will need to visit the study site multiple times over the study period.
• Risks include possible side effects of the medicine, but the study aims to ensure safety.