The purpose of this study is to evaluate the long-term safety, tolerability and efficacy of remibrutinib (LOU064) in adult participants with moderate to severe hidradenitis suppurativa (HS) who have completed either of the preceding Phase 3 studies, CLOU064J12301 or CLOU064J12302.

This is a global Phase 3, multicentre, double-blind, double-dummy, parallel-group extension study. It fulfils the Novartis commitment to provide post-trial access.

The study includes a double-blind and an open-label treatment phase:

Double-blind, double-dummy treatment continues from Week 68 (end of core study) until final database lock (DBL) of both core studies or until up titration. Participants remain on the same blinded regimen they were on during Treatment Period 2 of the preceding Phase 3 studies.

After final DBL of both core studies, treatment transitions to open-label.

Participants will continue treatment until commercial availability and reimbursement in their country, another access mechanism is available, or 4 years of extension treatment is completed.

Participants who discontinue treatment early or do not transition to commercial remibrutinib will enter a 4-week treatment-free safety follow-up.

Key Inclusion Criteria:

• Signed informed consent must be obtained before any assessment is performed.
• Participant has completed the full study treatment period according to the protocol (68 weeks) in the core studies (CLOU064J12301 or CLOU064J12302).
• Participant does not meet any treatment discontinuation criteria of the core study at Week 68.

Key Exclusion Criteria:

• Ongoing or planned use of prohibited HS or non-HS treatments.
• Participants not expected to benefit from participation in the extension study or participants expected to be exposed to an undue safety risk if participating in the extension study, as assessed by the Investigator.
• Current severe progressive or uncontrolled disease, which in the judgment of the Investigator renders the participant unsuitable for 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.