Study of XmAb942 in Healthy Participants and Participants With Ulcerative Colitis

This study consists of 3 parts, as follows: Part A: Single ascending dose (SAD) in healthy volunteer participants, will entail administration of XmAb942 or matching placebo at 3 different dose levels of XmAb942. Part B: Multiple ascending dosing for up to 3 doses, will entail administration of XmAb942 or matching placebo at 2 different dose levels of XmAb942. Part C: Participants with moderately to severely active UC to receive 3 different dose levels of XmAb942 or placebo during a 12-week induction period and single dose level of XmAb942 during a 40-week maintenance period, followed by a 36 follow-up period.