A Study to Evaluate the Long-Term Safety and Efficacy of Povorcitinib in Participants With Moderate to Severe Hidradenitis Suppurativa

Primary Outcome Measures

1. Proportion of participants with Treatment-Emergent Adverse Events (TEAEs)
   TEAE is defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not it is considered drug-related. An AE can therefore be any unfavorable or unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of study drug.

Secondary Outcome Measures

1. Proportion of participants with Serious Treatment-Emergent Adverse Events (TEAEs)
   Serious TEAE is defined as any untoward medical occurrence that, at any dose, meet at least one of the following criteria: (a) results in death; (b) is life-threatening; (c) requires inpatient hospitalization or prolongation of existing hospitalization; (d) results in persistent or significant disability/incapacity; (e) is a congenital anomaly/birth defect; (f) is an important medical event.
2. Proportion of participants with TEAEs leading to study drug discontinuation
   Defined as any TEAE that leads to discontinuation of study drug.
3. Proportion of participants who achieve Hidradenitis Suppurativa Clinical Response (HiSCR)
   HiSCR is defined as at least a 50% reduction from baseline of parent study in the total abscess and inflammatory nodule (AN) count, with no increase from baseline of parent study in abscess or draining tunnel count.
4. Proportion of participants who achieve Hidradenitis Suppurativa Clinical Response 75 (HiSCR75)
   HiSCR75 is defined as at least a 75% reduction from baseline of parent study in the total AN count, with no increase from baseline of parent study in abscess or draining tunnel count.
5. Proportion of participants who achieve Hidradenitis Suppurativa Clinical Response 90 (HiSCR90)
   HiSCR90 is defined as at least a 90% reduction from baseline of parent study in the total AN count, with no increase from baseline of parent study in abscess or draining tunnel count.
6. Proportion of participants who achieve Hidradenitis Suppurativa Clinical Response 100 (HiSCR100)
   HiSCR100 is defined as a 100% reduction from baseline of parent study in the total AN count, with no increase from baseline of parent study in abscess or draining tunnel count.
7. Proportion of participants with flare at each visit
   Flare is defined as at least a 25% increase in the total AN count with a minimum increase of 2 ANs relative to Week 54.
8. Time to first flare
   Time to first flare during the long-term extension study.
9. Mean change from baseline of parent study in Hidradenitis Suppurativa Quality of Life (HiSQoL) score at each visit
   The HiSQoL is a HS-specific, health-related quality of life (QoL) instrument. The HiSQoL total score ranges from 0 to 68, with higher scores indicating higher disease impact on QoL.
10. Mean change from baseline of parent study in Dermatology Life Quality Index (DLQI) score at each visit
    The DLQI is a skin disease specific questionnaire aimed at the evaluation of how symptoms and treatment affect participants' health-related quality of life (QoL). The DLQI total score ranges from 0 to 30, with higher scores indicating lower skin health related QoL.
11. Proportion of participants with no increase in abscess and inflammatory nodule (AN) count relative to Week 54 at each visit
12. Proportion of participants with no increase in abscess, inflammatory nodule, and draining tunnel (ANdT) count relative to Week 54 at each visit
    ANdT count is defined as the total sum of abscesses, inflammatory nodules, and draining tunnels.
13. Proportion of participants with no increase in draining tunnel count relative to Week 54 at each visit
14. Proportion of participants with a total AN count of 0, 1, or 2 at each visit
    AN count defined as the total sum of abscesses and inflammatory nodules.
15. Proportion of participants with a total ANdT count of 0, 1, or 2 at each visit
    ANdT count is defined as the total sum of abscesses, inflammatory nodules, and draining tunnels.