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A safety and efficacy study of SAR445399 in adults with moderate to severe hidradenitis suppurativa

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What is this trial about?

A plain-language summary of the goals, design and what participants do

Hidradenitis suppurativa is a long‑lasting skin disorder that creates painful lumps, tunnels and scarring, most often in the armpits, groin and other areas where skin rubs together. The study tests a new medication called SAR445399, which is given as a subcutaneous injection, and compares it with a placebo that looks the same but does not contain the active drug.

The purpose of the study is to evaluate the effectiveness and safety of different doses of the medication in adults with moderate to severe disease. Participants are randomly assigned to receive either the medication or the placebo by injection under the skin at regular visits for about 16 weeks. Throughout the trial, researchers check the condition of the skin, the amount of pain, quality of life and any side effects, while the study is conducted in a double‑blind manner so that neither the participants nor the study staff know which treatment is being given.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and randomization

    After joining the study, you will be assigned to receive either sar445399 or a matching placebo injection. the assignment is done randomly, and neither you nor the study staff will know which product you receive (double‑blind design).

  2. Step 2

    Baseline assessments

    Before any medication is given, a series of measurements will be taken to document the current severity of hidradenitis suppurativa and overall health. these include clinical examinations, the international hidradenitis suppurativa severity score system (ihs4), pain rating scales, quality‑of‑life questionnaires, laboratory tests, vital‑sign checks, and an electrocardiogram (ecg).

  3. Step 3

    First subcutaneous injection

    You will receive a subcutaneous (under the skin) injection of the assigned product. sar445399 is supplied as a powder that is mixed to create a solution for injection; the placebo is an 8 ml solution for injection. the exact amount of medication and the schedule for later doses are defined by the study protocol and will be administered by qualified staff.

  4. Step 4

    Regular follow‑up visits during the double‑blind treatment period

    Throughout the initial treatment phase, you will attend scheduled visits where additional injections may be given according to the study schedule. at each visit, safety will be monitored with laboratory tests, vital‑sign checks, and ecg recordings. you will also complete questionnaires that measure skin pain, itching, disease impact, and quality of life. these visits continue until week 16 of the study.

  5. Step 5

    Week 16 evaluation

    At week 16, a comprehensive assessment will be performed to determine the study’s primary and secondary outcomes. this includes measuring the percentage of participants achieving a 75 % improvement in disease activity (hiscr75), a 50 % improvement (hiscr50), and other clinical response levels, as well as changes in severity scores, pain ratings, tunnel counts, and quality‑of‑life scores. blood samples will also be taken to analyse drug concentration and the presence of anti‑drug antibodies.

  6. Step 6

    Treatment‑blinded extension period (if applicable)

    After the initial 16‑week period, some participants may enter an extension phase that continues with the same double‑blind medication regimen. during this time, injections, safety monitoring, and questionnaire assessments are continued as defined by the protocol.

  7. Step 7

    Final visit and study completion

    When the study ends, a final visit will be scheduled. you will undergo the last set of safety tests, complete final questionnaires, and provide blood samples for final analysis of drug levels and antibodies. after this visit, all study‑related procedures are concluded.

Who can join the trial?

7 criteria

  • Have had signs and symptoms of hidradenitis suppurativa (HS) for at least 6 months before the study starts.
  • Have HS skin lesions in at least two different body areas (for example, both armpits, or one armpit and one groin area), and at least one of those areas must be Hurley Stage II or III (a rating that shows moderate to severe disease).
  • Have a total of five or more abscesses (painful, pus‑filled lumps) and inflammatory nodules (firm, tender bumps) at the screening visit.
  • Have not responded well to an oral antibiotic, had the disease return after stopping antibiotics, cannot tolerate antibiotics, or have a medical reason that makes taking oral antibiotics unsafe (this is called a contraindication).
  • If placed in the “biologic‑naïve” group, must never have used any biologic therapy (medicines made from living cells that affect the immune system) for HS; if placed in the “biologic‑experienced” group, must have a record of receiving at least one dose of a biologic drug for HS.
  • Both men and women are eligible to participate.
  • The study may include patients who are considered vulnerable, such as children, if they meet the other requirements.

Who cannot join the trial?

7 criteria

  • Any other active skin disease or condition (for example, a bacterial, fungal, or viral infection) that could affect how the study measures your skin condition.
  • A history of repeated or recent serious infection, meaning infections that were severe or required strong medical treatment.
  • A known or suspected current immunosuppression, which means a weakened immune system that makes it harder for your body to fight infections.
  • A history of a solid organ transplant (receiving a new organ such as a kidney or liver) or a stem cell transplant (receiving blood‑forming cells).
  • A history of splenectomy, which is the surgical removal of the spleen.
  • A history of malignancy (cancer) or lymphoproliferative disease (a disorder where certain immune cells grow too much), except for skin cancers that were completely removed and cured, specifically non‑metastatic squamous cell carcinoma or non‑metastatic basal cell carcinoma of the skin.
  • Any other medical condition or severe, accompanying illness, including psychiatric illness (mental health problems) or substance abuse (misuse of drugs or alcohol), that could place you at high risk, make study participation unreliable, or interfere with study assessments.
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Investigated drugs

SAR445399 is an experimental medication being tested as a subcutaneous injection. It comes as a powder that is mixed with liquid to create a solution that is injected under the skin. In this study, researchers are giving the medication to people with moderate to severe hidradenitis suppurativa, a painful skin condition, to see if it can reduce the severity of the disease and to evaluate its safety. The trial is comparing different amounts of the medication to find the most effective dose.

What is already known about the treatment

SAR445399 - SAR445399 is given as a powder that is mixed with liquid and injected under the skin (subcutaneous injection). It is still an investigational drug being studied in Phase 2 clinical trials and is not yet approved for general medical use. The medicine is being tested for people with moderate to severe hidradenitis suppurativa, a painful skin condition. It belongs to a class of biologic agents that block a specific inflammatory protein, helping to reduce the skin inflammation that drives the disease.

Investigated diseases

Hidradenitis suppurativa - Hidradenitis suppurativa is a long‑lasting skin condition that creates painful, inflamed lumps in areas such as the armpits, groin, and under the breasts. The lumps begin as small bumps that can grow larger and may break open, releasing fluid. Over time, the bumps can connect to form tunnels under the skin that drain repeatedly. The skin around the tunnels often becomes thickened and scarred. The condition typically appears in early adulthood and may have periods when it gets worse and periods when it improves.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-522695-83-00Protocol codeDRI20674Estimated enrolment206 patientsSponsorSanofi-Aventis Recherche & Developpement

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