The study consists of three parts; Part 1: single ascending dose (SAD), Part 2: multiple ascending dose (MAD) in healthy volunteers and Part 3: proof of concept (POC) study in mild asthmatics. There will be 5 cohorts in SAD and 3 cohorts in MAD, the doses used in the MAD will be based on emerging safety, tolerability and pharmacokinetics (PK) from Part 1 (SAD). POC is a randomized, placebo- controlled, double blind, two period cross-over, proof of concept study in male and female of non child bearing potential with history of mild asthma. the highest identified dose of RP3128 in Part 2 (MAD) will be considered for POC