This is a randomized, double-blind, placebo-controlled, parallel-group phase 1b study to evaluate AT193 in approximately 44 participants with HS. The treatment period will be 8 weeks followed by a 2-week nontreatment follow-up. The primary objective of this study is to evaluate the safety and tolerability of AT193. The secondary objectives of this study are to evaluate the preliminary efficacy in the treatment of HS.

Inclusion Criteria:

• Diagnosis of HS or signs and symptoms consistent with HS for at least 3 months before screening in the judgment of the investigator.
• Stable disease for at least 2 months before screening in the judgment of the investigator.
• A woman of childbearing potential must use appropriate contraceptive measures during the study period.
• A woman of childbearing potential must have a negative urine pregnancy test result at screening.
• Written informed consent must be obtained before any study procedure is performed.

Exclusion Criteria:

• Pregnant or breastfeeding.
• Any active skin disease that may interfere with evaluation of study drug or outcome assessment.
• History or evidence of a clinically significant disorder, condition, or disease that would pose a risk to participant safety or interfere with the study evaluation, procedures, or completion in the judgment of the investigator.
• Change in smoking or marijuana history within 3 months before Day 1 or planned during study period.