The purpose of this version is to: - Modify eligibility criterion #35 to allow subjects to continue on non-opioid analgesics provided that the dose and dosing regimen have been stable for at least 14 days preceding the Baseline visit and are expected to remain stable at least until Week 16 visit. - Add a statement regarding dose/regimen adjustments for subjects who are on a documented stable dose and dosing regimen of a non-opioid analgesic treatment prior to entering the study. - Clarify eligibility criteria #24, 25, and 36 and relevant text in Section 5.2 and Section 5.3 to indicate duration of contraception use and expectation for live vaccines to be 20 weeks after the last dose of study drug or as guided by the local risankizumab label if approved, whichever is longer. - Clarify in Section 5.3 that ibuprofen is an allowed medication for pain management during study conduct. - Delete over the counter soap as a prohibited medication to treat HS in Section 5.3 - Clarify in Section 5.4, Allowed Concomitant Medications/Therapies that subjects will document their HS-related analgesic pain. - Increase the number of approximate enrollment sites from 50 to 60 sites. - Clarify in criterion #27 that for subjects who have had prior exposure to anti-TNF therapy, the last anti-TNF treatment administration must have occurred at least 3 months or 5 half-lives (whichever is longer) prior to Baseline. - Clarify data collection procedures in Section 3.4 and Section 3.11 of the Operations Manual. - Add requirement for collection of PK and ADA/nAb samples in the context of a suspected anaphylactic reaction in Section 3.13 of the Operations Manual. - Reduce duration of post-dose safety surveillance to 1 hour in Section 3.13 of the Operations Manual.

The purpose of this version is to: - Clarify the wording describing Hidradenitis Suppurativa Clinical Response (HiSCR) throughout the protocol. This clarification has no impact on the overall HiSCR analysis. - Clarify the wording describing the definition of NRS30 throughout the protocol. This clarification has no impact on the overall NRS30. - In Section 5.1, eligibility criterion #27, removed the cap of no more than 15% TNF-IR subjects from eligibility and changed the last anti-TNF treatment administration to having occurred at least 2 months prior to Baseline. - Clarify in Section 5.3 that metformin (except for continuous treatment of pre-existing diabetes) is a prohibited systemic therapy for HS during study conduct. - Clarify in Section 5.3, criterion #6, the prohibited treatments for HS-related pain during study conduct. - Clarify in Section 5.4, any lesion that undergoes an intervention as a rescue treatment will be counted as permanently present from the date of intervention. - Clarify in Section 5.5, the withdrawal criteria. - In Section 5.8, removed the cap of no more than 15% TNF-IR subjects. - Clarify in Section 5.8, the 4 strata in the study. - Update the description of analgesic therapy relative to subject pain in Section 5.4, Allowed Concomitant Medications/Therapies. - Remove Response Adaptive Randomization (RAR) in Section 5.8 and throughout protocol. - Remove Internal Executive Review Committee (IERC) in Section 5.8 and throughout protocol. - In Section 5.5, update wording on study withdrawal. - In Section 6.1, update safety considerations pertaining to adverse events and use of drug. - In Section 6.1, update the details about how to handle subjects who do not continue into Period B from the ITT Population. - In Section 7.3, update the statistical analysis for efficacy and the control for overall type-I error.

(continued) - In Section 7.3, update the power and sample size evaluation using adjusted assumptions. - Modify list of protocol signatories.

The purpose of this version is to revert the following text in Section 5.4 and Section 5.5 as introduced in Protocol Version 1.0 based upon Agency feedback on Protocol Version 3.0: - Remove the provision in Section 5.4, that the investigator should consult with the TA MD to determine whether discontinuation from the study would be in the best interest of the subject if the subject requires more than 2 protocol-allowed interventions after the Week 16 visit. - Add to Section 5.5, the discontinuation criterion if a subject requires > 2 protocol-allowed HS interventions.

The purpose of Protocol Version 5.0 is to update the following sections below and incorporate necessary protocol modifications due to the COVID-19 pandemic and per revised Risankizumab Safety Standards (v7.0) as follows: Modifications to the Protocol and Operations Manual due to State-of Emergency or Pandemic Situations One of the purposes of this version is to provide flexibility during state-of emergency or pandemic situations so subjects may safely enroll and continue study participation as follows: - Included information in Section 2.2 on the re-evaluation of the benefit and risk to subjects participating in the study. The benefit-risk profile of various immunomodulatory therapies is being evaluated. -Modify the following sections to account for state-emergency or pandemic situations: Update Section 5.5 to permit mitigation strategies for withdrawal/interruption/discontinuation of study drug. Update Section 5.9 to define protocol deviations to include those due to the COVID-19 pandemic. Update Section 7.3 to clarify that in the efficacy analysis, Non-Responder Imputation incorporating multiple imputation will be utilized to handle missing data due to COVID-19. Update Section 8.2 with a reference to the Operations Manual to permit modifications to the study protocol as necessary due to state-of emergency or pandemic situations and note investigators should also notify AbbVie if any urgent safety measures are taken. Update Section 9 to note that remote monitoring may be employed as needed. Update Appendix D to add reference to Operations Manual for allowed modifications.

(continued) Protocol - In the Synopsis and Section 2.1, replaced the term/abbreviation "inflammatory nodule (AN)" with "abscess and inflammatory nodule (AN)." - In the Section 2.2, updated that subjects with active systemic infection or clinically important infection will not be included in the study. - In the Section 2.2, removed text stating that there are no cases of active TB, including no reactivation of TB in subjects diagnosed with latent TB, across the entire risankizumab development program to date. - In the Section 2.2, updated that subjects with positive QuantiFERON-TB testing/TB skin test who have latent TB and are considered at low risk for reactivation are not required to be treated with TB prophylaxis. - Clarified in Section 3.3 that the additional endpoint with respect to the proportion of subjects achieving at least 1 grade improvement from Baseline in PGIS scale is among subjects with Baseline PGIS of at least "minimal." - In Section 5.3, removed text for new topical therapies and clarified the use of non-antibiotic topical therapies or changes in the concentration/frequency of such treatments for the treatment of HS. - In Section 5.3, added in addition to systemic antibiotic use, "and/or topical" antibiotic use is only allowed for the treatment of acute, non-HS related infections. - In Section 5.3, added Dengue (Dengvaxia®) to the list of examples of live attenuated vaccines that are not permitted during study participation and including up to 140 days after the last dose of study drug. - In Section 5.5, added hepatic test abnormalities confirmed by a second sample should be at least 48 hours apart. - In Section 6.1 for product complaints and pregnancies, replaced the reporting period from '1 business day' or '1 working day' (respectively) to '24 hours.'

(continued) - In Section 6.1, update the text 'areas of safety interest' to 'areas of safety interest/safety topics of interest' and rename Table 2 'Areas of Safety Interest' to 'Supplemental Adverse Events eCRFs.' - In Section 6.1, removed text that infections, especially opportunistic infections, are a potential risk with immunomodulators. - In Appendix C, updated protocol signatories and titles. - In Appendix D, removed "PGA Skin Pain and Analgesic Use" as an assessment performed at the Week 36 visit.