A Phase 1, Randomized, Double-blind, Placebo-controlled Study Evaluating AMG 691 in Healthy Participants and Participants With Mild-to-Moderate Asthma

Inclusion Part A and B * Participants must be capable of giving informed consent and have provided informed consent. * Participants must be 18 to 65, inclusive at time of signing of informed consent. * Participants must have a Body Mass Index between 18.0 to 30 kg/m\^2 and total body weight ≥ 40 kg at screening. * Participants must be overtly healthy as determined by the investigator based on medical evaluation and study screening procedures. * Female participants must be of non-childbearing potential. Inclusion Part C * Participants must be capable of giving informed consent and have provided informed consent. * Participants must be 18 to 70, inclusive at time of signing of informed consent. * Body mass index between 18.0 to 35 kg/m\^2 and total body weight ≥ 40 kg at screening. * Participants must have documentation of physician diagnosed asthma for ≥ 12 months prior to screening. * Participants must have documented bronchodilator responsiveness of forced expiratory volume in 1 second (FEV1) ≥ 10% in the 10 years before screening or at the screening visit. * Participants must have a pre-bronchodilator percent predicted FEV1 ≥ 50% at screening visit and Day -1. For participants on high-dose ICS, participants must have a percent-predicted FEV1 ≥ 70% at screening visit and on day -1. * Participants must have peripheral blood eosinophils ≥ 200 cells/μl at screening visit and Day -1. * Participants must have a fractional exhaled nitric oxide (FeNO) ≥ 25 ppb at screening visit…