The purpose of this study is to establish the efficacy, safety, and tolerability of remibrutinib (LOU064) Dose A and Dose B compared to placebo in participants with moderate to severe hidradenitis suppurativa (HS).

The total duration of the study is 76 weeks and consists of: Screening (up to 4 weeks), Treatment Period 1 (16 weeks, double-blind treatment with remibrutinib (Dose A or Dose B) or placebo, Treatment Period 2 (52 weeks, treatment with remibrutinib (Dose A or Dose B) and Safety Follow-Up (treatment-free follow-up for 4 weeks).

Participants who prematurely discontinue study treatment (either during Treatment Period 1 or Treatment Period 2) are encouraged to remain in the study. Participants who do not wish to remain in the study will enter a 4-week Safety Follow-Up period.

Key Inclusion Criteria:

1. Male and female participants ≥ 12 years of age at the time of signing of the informed consent.

2. Diagnosis of HS based on clinical history and physical examination for at least 6 months prior to the Baseline visit.

3. Participants with moderate to severe HS defined as:

   • A total of at least 5 AN count (abscesses and/or inflammatory nodules) AND
   • Inflammatory lesions should affect at least 2 distinct anatomic areas (e.g., left and right axillae)

Key Exclusion Criteria:

1. Presence of more than 20 fistulae/tunnels (both draining and non-draining) in total at baseline.
2. Any active skin disease or conditions that may interfere with the assessment of HS.
3. Previous exposure to remibrutinib or other BTK inhibitors.
4. Use of other investigational drugs within 5 half-lives of enrollment, or within 30 days (for small molecules) prior to randomization, or until the pharmacodynamic effect has returned to baseline (for biologics), whichever is longer.
5. Significant bleeding risk or coagulation disorders.
6. History of gastrointestinal bleeding.
7. Requirement for anti-platelet (except for acetylsalicylic acid up to 100 mg/d or clopidogrel up to 75 mg/d) or anti-coagulant medication.
8. History or current hepatic disease.
9. Evidence of clinically significant cardiovascular, neurological, psychiatric, pulmonary, renal, hepatic, endocrine, metabolic, hematological disorders, gastrointestinal disease or immunodeficiency that, in the Investigator's opinion, would compromise the safety of the participant, interfere with the interpretation of the study results or otherwise preclude participation or protocol adherence of the participant.
10. History of hypersensitivity to any of the study drug constituents.
11. Known or suspected infectious disease that is active, chronic or recurrent which precludes the participant from participating in the trial as per investigator's assessment. These infectious diseases include and are not limited to opportunistic infections (e.g., tuberculosis, atypical mycobacterioses, listeriosis or aspergillosis) and/or known or suspected Human Immunodeficiency Virus (HIV) infection. Should it be required by local regulations and/or considered appropriate by the investigator, an HIV test can be performed to confirm eligibility.
12. History of live attenuated vaccine administration within 6 weeks prior to randomization or requirement to receive these vaccinations at any time while on study treatment.
13. Major surgery within 8 weeks prior to screening or planned surgery for the duration of the study.

Other protocol-defined inclusion/exclusion criteria may apply.

Novartis is committed to sharing with qualified external researchers, access to patient-level data and supporting clinical documents from eligible studies. These requests are reviewed and approved by an independent review panel on the basis of scientific merit. All data provided is anonymized to respect the privacy of patients who have participated in the trial in line with applicable laws and regulations.

This trial data availability is according to the criteria and process described on www.clinicalstudydatarequest.com