**Study Summary**: This study is to check how safe and tolerable a new medicine called AMG 691 is. It involves people who are healthy and those with mild-to-moderate asthma. *Asthma* is a condition where breathing becomes difficult due to swollen airways. The study is divided into different parts, including single doses for healthy people and multiple doses for both groups. Participants must be 18-65 years old, have a certain weight and height, and be generally healthy. For those with asthma, they need to have had it for at least a year and meet specific breathing test results. **Key Points**: - **Study Length and Visits**: Multiple visits may be required but the exact number isn't detailed here. - **Compensation**: It may be provided, but details are not specified. - **Risks**: Participants with severe infections or certain medical histories are excluded to minimize risks. Before joining, individuals should ensure they meet all the criteria and understand the study's requirements, benefits, and potential risks. *Informed consent* is mandatory, meaning participants agree to take part after understanding everything about the study.