We are recruiting subjects aged 18 to 65 years (inclusive) with Alopecia Areata , to participate in a research study that evaluates the safety of an investigational study drug. The research will involve two groups of people who will receive different amounts of a medication called IMG-007. The first group, called Cohort 1, will have six participants who will receive three IV infusions of IMG-007 300 mg over a period of 4 weeks. The second group, called Cohort 2, will have 24 participants who will receive three IV infusions of IMG-007 600 mg over a period of 4 weeks. Each group will go through three phases: a screening phase that can last up to 4 weeks, a 16-week treatment phase, and an 8-week follow-up phase.