**Study Overview:** This study is testing a new medicine called *povorcitinib* for people with *moderate to severe asthma* that isn't well controlled. Asthma is a condition that makes it hard to breathe because the airways in the lungs are swollen or blocked. The study will look at how different doses of *povorcitinib* affect how well your lungs work. **Eligibility:** To join, you must have asthma that's been treated with medium or high doses of *ICS-LABA* (a combination of inhaled medicines) for at least a year. You should have had asthma attacks needing extra treatment twice in the last year, but not in the last month. Certain health conditions or treatments, like smoking or having other lung diseases, may prevent you from participating. **Key Points:** - **Study Duration & Visits:** The study will have several visits over a specific period. - **Compensation:** Participants might receive compensation for their time. - **Risks:** There may be some risks or side effects from the medication or procedures, which will be explained by the study team. This study could help find better treatments for asthma, but it's important to consider the time commitment and potential risks.