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Safety and Efficacy Study of the Acne mRNA vaccine (mrt1800, mrt1801, mrt1802) in Adults 18‑45 Years with Moderate to Severe Acne

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What is this trial about?

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

Acne is a common skin condition that causes pimples, blackheads, and sometimes deeper nodules. The study tests a new type of vaccine called Acne mRNA vaccine that contains three experimental components named MRT1800, MRT1801, and MRT1802. The vaccine is given as an intramuscular injection, which means it is placed into a muscle using a needle, and the product is a suspension for injection, a liquid that contains tiny particles that dissolve in the body. Some participants will receive a simple salt water solution called placebo instead of the vaccine, so that researchers can compare the results.

The purpose of the study is to see if the vaccine is safe, works to reduce acne, and triggers the body’s immune system to recognize the skin problem. Adults aged 18 to 45 with moderate to severe acne will receive a few doses over several weeks and will return for regular visits where doctors check the skin, ask about any side effects such as soreness at the injection site or feeling unwell, and take simple blood tests. The study will continue for several months to monitor any longer‑term effects.

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

    Baseline assessment

    On the day you join the study, you will have a baseline visit. during this visit, study staff will count the number of inflammatory and non‑inflammatory acne lesions on your face, take a blood sample, and record basic health information. these measurements create a reference point for later comparisons.

  2. Step 2

    First injection

    After the baseline assessments, you will receive an injection. the injection may contain the acne mRNA vaccine (a suspension for intramuscular injection) or a placebo consisting of 0.9 % sodium chloride solution. the exact dose and volume are determined by the study protocol but are not disclosed here. the injection is given into a muscle, usually in the upper arm.

  3. Step 3

    Immediate safety observation

    Following the injection, you will remain in the clinic for a short observation period, typically about 30 minutes, so that staff can monitor for any immediate reactions at the injection site or systemic symptoms such as fever or feeling unwell.

  4. Step 4

    Scheduled follow‑up visits

    You will return to the clinic at several time points defined by the study. at each visit, you will again have your acne lesions counted, provide another blood sample to measure antibody levels, and answer questions about any side effects you may have experienced since the previous visit.

    The study staff will also perform routine laboratory tests to check for any out‑of‑range results and will record any adverse events, whether they are considered related to the injection or not.

  5. Step 5

    Core study sentinel cohort assessment

    For participants in the sentinel cohorts, the primary focus is safety. the study will specifically look for unsolicited systemic adverse events, injection‑site reactions, medically‑attended adverse events, serious adverse events, and any events of special interest.

  6. Step 6

    Core study main cohort assessment

    For participants in the main cohorts, efficacy is evaluated. the change in the number of inflammatory, non‑inflammatory, and total acne lesions on your face is compared with the baseline count taken on day 1.

    The study also measures the amount of vaccine‑specific antibodies in your blood to see how your immune system responded.

  7. Step 7

    Long‑term extension

    After the core study period, you may enter a long‑term extension phase. during this phase, you will continue to be monitored for safety, with periodic visits to report any serious adverse events or events of special interest that occur later.

    The same lesion counts and blood tests may be repeated at longer intervals to assess the durability of any benefit and to ensure ongoing safety.

Who can join the trial?

9 criteria

  • Be in overall good health, as determined by the doctor through review of medical history, a physical exam, and lab tests (overtly healthy).
  • Have a doctor‑confirmed diagnosis of moderate or severe facial acne (acne vulgaris).
  • Score a 3 or 4 on the 5‑point Investigator’s Global Assessment (IGA) scale, which means the acne is judged moderate (3) or severe (4).
  • Have at least 25 non‑inflammatory lesions, which are the small bumps called open or closed comedones (blackheads or whiteheads).
  • Have at least 20 inflammatory lesions, which are red, tender spots such as papules and pustules.
  • Have no more than 2 nodulocystic lesions, which are larger, deeper lumps called nodules or cysts.
  • Be either male or female.
  • Be eligible to enroll as a vulnerable participant (for example, a minor) if allowed by the study rules.
  • Fall within the study’s defined age range (identified by code “3” in the protocol).

Who cannot join the trial?

8 criteria

  • Having a known or suspected immune system problem you were born with (congenital) or that developed later (acquired), or having taken medicines that suppress the immune system (such as chemotherapy, radiation therapy, or strong steroids) within the last 6 months, or taking steroids for more than 2 weeks in the past 3 months. Immunosuppressive therapy means treatment that weakens the body’s ability to fight infections.
  • Being allergic (systemic hypersensitivity) to any part of the vaccine, having had a life‑threatening allergic reaction to the vaccine or a similar product, or having experienced a severe allergic reaction called anaphylaxis after a COVID‑19 mRNA vaccine. Anaphylaxis is a rapid, serious allergic reaction that can affect breathing and blood pressure.
  • Having active severe forms of acne such as nodulocystic acne, acne conglobate, acne fulminans, or acne caused by chemicals, medicines, or friction (examples: chloracne, drug‑induced acne, acne mechanica). These are uncommon, very inflamed types of acne.
  • Using any acne treatment without stopping it for the required “washout period” (a short break) before joining the study. A washout period allows previous medicines to leave the body.
  • Receiving any other vaccine (aside from the study vaccine) within 4 weeks before or after the study vaccine dose.
  • Having previously received an experimental vaccine against C. acnes (the bacteria that can cause acne).
  • Receiving immune globulins, blood, or blood‑derived products in the past 3 months. These are treatments made from donated blood that can affect the immune system.
  • Having a known positive test (seropositivity) for HIV, hepatitis B virus, or hepatitis C virus. These are infections that affect the immune system or liver.
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Investigated drugs

Acne mRNA vaccine is an experimental vaccine being tested to treat moderate to severe acne. It contains three messenger RNA components (MRT1800, MRT1801, MRT1802) that tell the body’s cells to make proteins that aim to reduce the bacteria and inflammation that cause acne. The vaccine is given as a liquid suspension injected into the muscle. In the study, participants receive this vaccine to see if it is safe, if it improves acne, and whether it remains safe over a longer period.

What is already known about the treatment

  • MRT1800

    This experimental substance is administered by intramuscular injection as a suspension for injection. It is currently being studied in early‑phase clinical trials and is not yet approved for any medical use. The vaccine is designed to treat moderate to severe acne by prompting the body’s immune system to recognize and reduce skin inflammation. It belongs to the class of mRNA vaccines, which work by delivering genetic instructions that cause cells to produce a target protein and trigger an immune response.

  • MRT1801

    Given as an intramuscular injection in a liquid suspension, this investigational agent is in early clinical testing and has no approved therapeutic use. It is intended to help adults with moderate to severe acne by stimulating an immune reaction that lessens acne lesions. The molecule is an mRNA construct that directs cells to make a specific protein, thereby activating the immune system. It is classified as an mRNA vaccine, a type of immunotherapy.

  • MRT1802

    This component is delivered by intramuscular injection as a suspension and is currently only available within research studies, with no commercial approval. Its purpose is to treat acne by training the immune system to target factors that cause skin breakouts. It works at the molecular level by providing messenger RNA that instructs cells to produce a protein that the immune system can recognize, leading to a protective response. It falls under the pharmacological class of mRNA vaccines.

Investigated diseases

Acne - Acne is a common skin condition that produces red, inflamed spots, blackheads, and whiteheads, usually on the face, chest, and back. It begins when hair follicles become clogged with oil and dead skin cells. Over time, the clogged pores can become infected, leading to swelling and the formation of pustules or nodules. The lesions may appear in groups and can vary in size and severity. As the condition continues, lesions may increase in number and become more persistent if the underlying blockage and inflammation are not reduced.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase I/IITrial ID2025-521740-38-00Protocol codeVBE00001Estimated enrolment549 patientsSponsorSanofi Vaccines US Inc.

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