This research study is designed to find out if a new medicine called RCT2100 is safe for people to use. The study has two parts: Part 1 is for healthy adults, and Part 2 is for people with Cystic Fibrosis (CF), a lung disease. In Part 1, healthy people will inhale one dose of RCT2100 through a nebulizer, a machine that turns liquid medicine into mist. In Part 2, people with CF will inhale multiple doses. The goal is to learn about the medicine's safety, how it spreads in the body, and if there are any side effects.

• Healthy adults must be between 18-55 years old, weigh at least 50 kg, and be non-smokers.
• People with CF must have lung function above 40% and either cannot use or tolerate CFTR modulators, which are special CF medicines.
• The study excludes those with certain health issues, recent infections, or recent use of CF medicines.

Participation involves multiple visits and tests, but the study does not mention compensation. Joining this study can help advance CF treatment but carries usual research risks, like side effects.