Study of PRA-216 in Healthy Participants and Participants With Mild-to-Moderate Asthma

This study is a Phase 1/2a randomized, double-blind, placebo-controlled, single- and multiple-dose study with staggered dose escalations in healthy participants and participants with mild to moderate asthma. Single-ascending dose (SAD) cohorts will be evaluated for one single dose administered. Multiple ascending dose (MAD) cohorts will be evaluated for repeat doses . Participants with mild to moderate asthma will be recruited for Phase 2a of this study, to evaluate safety of randomized, double blind, placebo controlled PRA-216. The dose of PRA-216 for this phase was determined from Phase 1 safety, tolerability, and PK data. Additional dose levels or schedules may be used for Phase 2a, depending on data from Phase 1. This study consists of 2 phases, as follows: Phase 1, Part 1: SAD in healthy volunteers. Study visits in this section will entail a single dose administration of PRA-216 or placebo and collection of study data. Phase 1, Part 2: MAD in healthy volunteers. Study visits in this section will entail repeat doses of PRA-216 or placebo and collection of study data. Phase 2a Participants with mild to moderate asthma will receive PRA-216 or placebo.