The main objective of this study is to determine if NAV-240 works more effectively than a dummy treatment (placebo) for participants with moderate-to-severe HS. The main endpoint of this study is the percentage of participants achieving Hidradenitis Suppurativa Clinical Response (HiSCR) 75 at Week 16, meaning at least a 75% reduction in inflamed skin bumps (abscess and inflammatory nodule (AN) count) with no increase in number of abscesses or draining tunnels (channels under the skin that leak fluid or pus) compared to the baseline (start of the study).

Participants will:

• Receive NAV-240 dose 1, NAV-240 dose 2 or placebo as a drip into the veins (intravenous infusion).
• Visit the clinic up to 9 times for checkups and tests over 22 weeks.
• Complete a daily diary about their skin pain.

Inclusion Criteria:

• History of HS for ≥ 6 months
• Abscesses and Inflammatory Nodules (lesion) count ≥ 5
• Inflammatory HS lesions in at least 2 different body regions, one of which must be Hurley Stage II or III
• Inadequate response to at least one course of antibiotics
• Topical antiseptics are not required but allowed. If in use, the participant must agree to use one single product consistently through Week 16.
• Use of oral antibiotics is allowed during the study under the following conditions: the dose and regimen must remain stable until Week 16. Allowed oral antibiotics include doxycycline, minocycline, or tetracycline.
• Female participants of childbearing potential must have a negative pregnancy test
• Participants of reproductive potential must use a highly effective method of contraception

Exclusion Criteria:

• > 20 draining tunnel count
• Active skin disease (bacterial, fungal, viral infection) that, in the opinion of the Investigator, could interfere with assessment of HS or requires treatment with antibiotic(s) also used to treat HS.
• Has had major surgery, including HS surgery, within 12 weeks prior to Day 1
• History of alcohol or drug abuse within the past 2 years.
• A positive urine drug screen at Screening
• History or evidence of human immunodeficiency virus (HIV), hepatitis B or hepatitis C virus (HCV), or a positive test at Screening
• History or current diagnosis of active tuberculosis (TB), untreated latent TB infection (LTBI), or undergoing current treatment for LTBI, determined by positive TB test
• History of moderate to severe heart failure or recent (within past 6 months) cerebrovascular accident, myocardial infarction, or coronary stenting.
• History of immune deficiency