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Safety and Tolerability of REGN7999 in Healthy Adult Participants

Verified siteInvestigationalNo placebo
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What is this trial about?

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

The study looks at a medicine called REGN7999, which works by blocking a protein named TMPRSS6. This type of medicine is being developed for conditions where the body stores too much iron, known as iron overload. In the trial the drug is given in two ways: through a needle into a vein (intravenous) or under the skin (subcutaneous), and the amount given is increased step by step to see how the body handles it.

The purpose of the trial is to find out if a single dose of REGN7999 is safe and well tolerated in healthy adult volunteers. Participants are randomly assigned to receive either the medicine or a placebo, and neither the participants nor the study staff know which one is given. After the dose, participants are checked regularly for any side effects, and blood samples are taken to measure how much of the medicine is in the blood and whether the immune system makes any antibodies against it. The follow‑up period lasts up to about five to six months, depending on the group, with visits scheduled to monitor health and collect samples.

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

    First study visit – baseline assessment

    You arrive at the clinic after signing the consent form. staff collect information about your medical history, perform a physical exam, and take blood samples. these measurements establish a baseline before any medication is given.

  2. Step 2

    Administration of study medication

    You receive a single dose of regn7999 at a dose of 900 mg. the medication is given either by intravenous (iv) infusion or by subcutaneous (sc) injection, depending on the cohort to which you are assigned. a matching placebo may be used in the same manner for comparison.

  3. Step 3

    Immediate post‑dose monitoring

    After the dose, you remain in the clinic for several hours. staff check your vital signs (blood pressure, heart rate, temperature) regularly and may take additional blood samples to assess early drug levels and safety. any side effects that appear are recorded.

  4. Step 4

    Discharge and symptom diary

    Once cleared by staff, you go home. you are given a diary to note any symptoms, discomfort, or other changes you experience until the next scheduled visit.

  5. Step 5

    Follow‑up visits – early phase

    You return to the clinic for follow‑up visits at approximately day 1, day 7, and day 14 after dosing. each visit includes a brief physical check, review of your diary entries, and blood draws to measure regn7999 concentration in serum and to test for anti‑drug antibodies (ada).

    Anti‑drug antibodies are proteins your body may produce that can affect how the medication works. the tests help determine if these antibodies develop over time.

  6. Step 6

    Follow‑up visits – extended phase

    Additional visits are scheduled at weeks 4, 8, 12, and either week 20 or week 26, depending on the cohort:

    - for iv cohorts 1 to 4 and sc cohorts 1 and 2, the final visit occurs at week 20.

    - for iv cohort 5 and sc cohort 3, the final visit occurs at week 26.

    At each of these visits, staff repeat safety assessments, record any adverse events (undesired effects), and collect blood for continued measurement of drug levels and anti‑drug antibodies.

  7. Step 7

    Final study visit – end of study

    At the last scheduled visit (week 20 or week 26), a comprehensive evaluation is performed. this includes a full physical exam, final laboratory tests, and a review of all adverse events that occurred during the study.

    The data collected helps determine the safety, tolerability, and how the body processes regn7999 after a single dose.

Who can join the trial?

5 criteria

  • You must be a man or woman who is between 18 and 60 years old at the time of the screening visit.
  • The study doctor must decide that you are in good health, based on your medical history, a physical check‑up, measurements of your vital signs (such as blood pressure and heart rate), and an ECG (a test that records the electrical activity of your heart) done before the first dose.
  • Your blood levels of hemoglobin (the protein that carries oxygen), serum iron (the amount of iron in your blood), transferrin (a protein that transports iron), serum ferritin (a storage form of iron), and transferrin saturation (how much transferrin is carrying iron) must be at or above the lowest normal range for your age and sex, as measured by the local laboratory and confirmed with a repeat test.
  • Counts of white blood cells (WBC) (cells that fight infection), platelets (cells that help clot blood), red blood cells (RBC) (cells that carry oxygen), as well as your hematocrit (the percentage of blood that is made up of red cells) and RBC hemoglobin must not be noticeably outside the normal range, according to the study doctor’s judgment at screening and before the first dose.
  • You must sign an informed consent form, showing that you understand the study and agree to take part.

Who cannot join the trial?

22 criteria

  • Being pregnant or currently breastfeeding.
  • Being a woman who could become pregnant (a woman of child‑bearing potential) and not willing to use a very reliable method of birth control for the whole study period. Highly reliable birth control includes:
    • Consistent use of hormonal pills, patches, rings, injections or implants that stop ovulation and have been started at least two menstrual cycles before screening.
    • An intra‑uterine device (IUD) or a hormone‑releasing IUD placed in the uterus.
    • Permanent surgical sterilization such as tubal ligation (tying the fallopian tubes) or a partner’s vasectomy (cutting the tubes that carry sperm).
    • Abstaining from sexual activity as described in the study protocol.
    • Being a pre‑menopausal woman (still having menstrual cycles) whose birth‑control method still causes regular bleeding, or who is currently menstruating. Women must either be post‑menopausal, have had permanent removal of the uterus or ovaries, or be using a method that stops periods.
    • Having a significant medical problem in any of the following areas that could affect safety or study results:
      • Heart or blood‑vessel disease (such as congestive heart failure or angina).
      • Lung or breathing problems.
      • Liver disease.
      • Kidney disease.
      • Stomach or digestive‑tract disease.
      • Hormone (endocrine) disorders.
      • Blood‑related disorders (hematological).
      • Infections that are ongoing or have caused serious problems.
      • Autoimmune diseases (where the immune system attacks the body).
      • Cancer (oncologic disease).
      • Psychiatric (mental health) conditions.
      • Nervous‑system (neurological) disorders.
      • Having a history of long‑term anemia (low red‑blood‑cell count) at any time.
      • Having donated a whole blood unit within the past 56 days, or plasma within the past 7 days, or planning to donate blood or plasma at any time during the study.
      • Having taken part in another clinical trial with an experimental drug (including biologic therapies) within the last 90 days, or within a period equal to at least five times the drug’s half‑life (whichever is longer), or at least 4 weeks for other non‑biologic investigational drugs.
      • Receiving a COVID‑19 vaccine less than one week before the planned start of the study drug, or not being able to complete the COVID‑19 vaccination series at least one week before the first dose of the study medication.
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Investigated drugs

REGN7999 is an experimental medicine that blocks a protein called TMPRSS6. In this study, healthy volunteers received a single dose of the drug either through a vein (intravenous) or under the skin (subcutaneous). The purpose was to find out whether the drug is safe, how well the body processes it, and how it influences the body’s iron‑regulating system. The product comes as a powder that is mixed with liquid right before it is injected.

What is already known about the treatment

REGN7999 - REGN7999 is supplied as a powder that is mixed with liquid and given as a single 900 mg injection either into a vein (intravenous) or under the skin (subcutaneous). It is currently in Phase 1 clinical trials and has not yet been approved for any medical use, although it is being studied for diseases that involve iron overload. The drug works by blocking the protein TMPRSS6, which increases a hormone that reduces iron absorption, helping to lower excess iron in the body. Pharmacologically, it is classified as a monoclonal antibody TMPRSS6 antagonist.

Investigated diseases

Iron overload - Iron overload is a condition where excess iron accumulates in the body’s tissues. The excess iron is gradually stored in organs such as the liver, heart, and pancreas. Over time, the buildup can cause the organs to become enlarged and function less efficiently. The condition often progresses silently, with symptoms appearing only after iron has been deposited for many years. Monitoring iron levels helps to track the progression of the condition.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase ITrial ID2022-500398-15-00Protocol codeR7999-HV-2154Estimated enrolment64 patientsSponsorRegeneron Pharmaceuticals Inc.

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