• Body mass index (BMI) ≤50 kg/m2, inclusive

• Diagnosis of clinically active moderate-to-severe HS (Hurley Stage 2 or 3)

• Total abscess or inflammatory nodule (AN) count of ≥5, affecting at least 2 distinct anatomic regions, with at least 1 accessible AN of adequate size for biopsy (diameter \> 1 cm)

• Total draining tunnel (dT) count of ≤20

• Documented history of inadequate response or intolerance to at least a 3-month course of 1 conventional systemic therapy (e.g., antibiotic) and 1 biologic drug (e.g., adalimumab or secukinumab)

• Doses of medications for HS must be stable for at least 5 weeks prior to study drug administration

• Must agree to use highly effective method of contraception for at least 1 year post SBT777101 administration