ATI-450 vs Placebo in Participants With Moderate to Severe Hidradenitis Suppurativa (HS)

AN count was the sum of number of abscess and inflammatory nodules across anatomical regions.

The least square (LS) mean change from baseline in the count at Week 12 was estimated from the Mixed Model Repeated Measures (MMRM) model.

HiSCR50 Achiever was defined as a participant having a ≥50% reduction from baseline in the total abscess and inflammatory nodule count, with no increase in the number of abscesses, and no increase in the number of draining fistula counts from baseline. A participant was considered an achiever only if all 3 criteria mentioned above were fulfilled.

Model-based estimates and 90% confidence intervals (CIs) were produced. Firth's penalized likelihood logistic regression model with fixed effects for treatment and baseline count of inflammatory abscesses and nodules was used.

The IHS-4 is a validated tool used to access the HS severity and is calculated based on the clinical signs of HS: inflammatory nodules, abscesses and draining tunnels (fistulas and sinuses). The IHS-4 score = (number of nodules multiplied by 1) + (number of abscesses multiplied by 2) + (number of draining tunnels [fistulas/sinuses] multiplied by 4).

Mild HS is a score of 3 or less, moderate HS is a score of 4-10, and severe HS is a score of 11 or higher. A decrease in score means less severity.

NRS30 Achiever was defined as participants achieving at least a 30% reduction from baseline in Patient's Global Assessment of Skin Pain (PGA-SP) and at least 1 unit reduction from baseline in PGA-SP at Week 12 among participants with baseline PGA-SP ≥3.

Model-based estimates and 90% CIs were produced. Firth's penalized likelihood logistic regression model with fixed effects for treatment and baseline PGA-SP was used.

In the HS-PGA scale, the Investigators rated the counts of nodules (inflammatory and non-inflammatory) abscesses and fistulas (both draining and nondraining) and assigned a participant to 1 of 6 categories ranging from clear (0) to very severe (5). A decrease in score means a better outcome.

The DLQI is a 10-item validated questionnaire used to assess the impact of HS disease symptoms and treatment on quality of life (QoL). It consists of questions including a single "yes/no" question and questions with possible responses of "not at all," "a little," "a lot," or "very much." These questions evaluate the impact of skin diseases on different aspects of a participant's QoL over the prior week, including symptoms and feelings, daily activities, leisure, work or school, personal relationships, and the side effects of treatment. Each question was scored using a 4-point scale ranging from 0 to 3 based on a participant's response: not at all/not relevant (0), a little (1), a lot (2) and very much (3). The total score of the DLQI ranged from 0 to 30 and was calculated by adding up the scores from each question. The higher the score, the greater the impact on a participant's QoL.

TEAEs are defined as AEs with an onset date on or after the date of first administration of study drug and before the date of last administration of study drug + 30 days. A summary of non-serious AEs and serious AEs, regardless of causality is located in Reported AEs section.