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A study of SAR448851 with FLORQUINITAU (18F) to assess safety and effectiveness in early Alzheimer’s disease

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What is this trial about?

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

Early Alzheimer's disease is a condition that affects memory and thinking skills, usually beginning with mild problems that gradually become more noticeable. The study investigates an oral medication called SAR448851, which is taken as a hard capsule, and compares it to a matching placebo that looks the same but does not contain the active drug.

The purpose of the study is to evaluate the safety and effectiveness of SAR448851 in people with early Alzheimer’s disease. Participants will take the study medication every day for about 48 weeks, during which they will have regular visits for simple blood tests that measure a protein called p‑tau217, a marker that can show changes related to the disease, and may also undergo a brain scan to look for amyloid plaques, which are tiny buildups associated with Alzheimer’s. After the first 48 weeks, participants may choose to continue in an open‑label phase, where everyone receives the active medication, for up to another year, with continued monitoring.

Throughout the trial, safety is closely watched by checking for any side effects, measuring vital signs, and performing routine laboratory tests. Any serious problems are recorded, and participants can stop the study at any time if needed.

The research process

The trial runs in 9 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization and baseline assessments

    After joining the study you will be assigned by a computer to receive either sar448851 or a matched placebo. the assignment is unknown to you and the study staff.

    You will have an initial visit where blood is drawn, a brain scan called a mri is performed, and a special imaging test called a pet scan is scheduled.

  2. Step 2

    Start of study medication

    You will begin taking one oral capsule each day. the capsule contains 25 mg of sar448851 if you were assigned to the active group, or no active drug if you were assigned to the placebo group.

    The capsule is taken by mouth with water, preferably at the same time each day, for the next 48 weeks.

  3. Step 3

    Baseline pet scan with mk-6240

    Shortly after the first medication dose you will receive an intravenous injection of the tracer mk-6240 (185 MBq). the injection is given into a vein and lasts only a few seconds.

    The tracer allows a pet scan to measure amyloid plaques in the brain. you will lie on a scanner table while images are taken; the procedure takes about 30 minutes.

  4. Step 4

    Regular clinic visits during the double‑blind phase

    You will return to the clinic at weeks 4, 12, 24, 36 and 48. at each visit you will:

    • provide a blood sample for laboratory tests and to measure the level of sar448851 in your body.
    • undergo safety checks such as blood pressure, heart rhythm (ecg), and a brief questionnaire about side effects.
    • receive a brief physical examination.

    If any side effects occur, the study staff will record them as treatment‑emergent adverse events (events that start after you begin the medication).

  5. Step 5

    Continuation of daily medication through week 48

    You will keep taking the assigned capsule every day for the full 48‑week period. missing doses should be avoided; if a dose is missed, you should take it as soon as you remember unless it is close to the next scheduled dose.

  6. Step 6

    End of double‑blind phase assessment

    At week 48 you will have a final set of assessments similar to the earlier visits, including blood tests, a brain mri, and another pet scan with mk-6240 to compare changes over time.

  7. Step 7

    Optional open‑label extension

    After week 48 you may choose to continue in an open‑label extension. in this part all participants receive the active drug sar448851 at the same 25 mg daily dose, regardless of earlier assignment.

    The open‑label period lasts an additional 48 weeks, up to week 96.

  8. Step 8

    Clinic visits during the open‑label extension

    During weeks 60, 72, 84 and 96 you will attend clinic visits that include the same safety checks, blood sampling, and imaging procedures as before.

    The purpose is to monitor long‑term safety and to measure changes in disease‑related biomarkers.

  9. Step 9

    Final assessment at week 96

    At the end of week 96 a final evaluation is performed. this includes a blood draw, a brain mri, and a pet scan with mk-6240 to assess the overall effect of the medication over the 96‑week period.

Who can join the trial?

5 criteria

  • Be between 55 and 85 years old when you sign the consent form.
  • Have a doctor’s diagnosis of mild cognitive impairment (MCI) due to Alzheimer’s disease (early memory problems) or mild Alzheimer’s dementia (early stage of the disease).
  • Show a Clinical Dementia Rating (CDR) score between 0.5 and 1.0, indicating mild dementia, and a CDR‑Memory Box score of at least 0.5 during the screening visit.
  • Have a study partner who is over 18 years old, has known you for at least one year, spends at least 8 hours per week with you, and can give a separate written consent.
  • Provide proof of cerebral amyloid pathology by having a positive visual reading on an amyloid PET scan, which is a brain imaging test that shows amyloid plaques linked to Alzheimer’s disease.

Who cannot join the trial?

6 criteria

  • The participant has a history of serious brain conditions such as frontotemporal dementia (memory and behavior problems caused by damage to the front part of the brain), Lewy body dementia (fluctuating alertness and visual hallucinations), Huntington’s disease (a genetic disorder that causes movement and thinking problems), a serious infection of the brain, Parkinson’s disease (tremor and stiffness), many concussions, multiple sclerosis (damage to the protective covering of nerves), epilepsy (recurrent seizures) or repeated seizures (except fever‑related seizures that happen in childhood).
  • The participant shows more than four tiny brain bleeds called microhemorrhages (each smaller than 10 mm) or has superficial siderosis (a thin layer of iron‑containing blood breakdown products on the surface of the brain).
  • The participant carries two copies of the genetic variant known as apolipoprotein‑E epsilon 4 (APOE4) allele (written as APOE4/4), which is linked to higher risk of Alzheimer’s disease.
  • The participant is currently receiving or has previously received any anti‑amyloid immunotherapy (medicines that target the amyloid protein, such as aducanumab, lecanemab, or donanemab) or any treatment that targets TREM‑2 (a protein involved in brain immune response).
  • The participant is currently taking anticoagulant therapies (blood‑thinning medicines that prevent clot formation).
  • The participant has had a malignancy (cancer) within the past three years, except for certain skin cancers, early‑stage prostate cancer, fully removed kidney cancer, or early cervical cancer that was successfully treated.
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Investigated drugs

  • SAR448851

    is an experimental oral capsule being studied for people with early Alzheimer’s disease. In this trial participants take the capsule daily for 48 weeks. The main goal is to see if the medicine can lower a protein called p‑tau217 in the blood, which is linked to the disease. The study also looks at how safe the medicine is and whether participants can tolerate it over a long period.

  • MK-6240

    is a special imaging agent that is given by a quick intravenous injection. It is used during the trial to take detailed pictures of the brain with PET scanning. This helps researchers see the amount of disease‑related changes in the brain and provides a background picture to compare with the effects of the test medicine.

What is already known about the treatment

  • SAR448851

    This drug is taken as a hard capsule taken by mouth, usually 25 mg per dose. It is still an investigational medicine being studied in Phase 2 trials and is not yet approved for general use. It is being tested for early Alzheimer’s disease and aims to lower abnormal tau protein that builds up in the brain. It belongs to the class of small‑molecule tau‑targeting agents that aim to modify disease progression.

  • MK-6240

    This agent is given as an intravenous injection of a solution that contains the radioactive tracer florquinitau (¹⁸F). It is an experimental imaging compound used in PET scans and is not yet approved for routine clinical practice. It helps doctors see tau plaques in the brain of people with Alzheimer’s disease by attaching to the plaques and emitting a signal that the scanner detects. It is classified as a radiopharmaceutical imaging agent.

Investigated diseases

Alzheimer's disease - Alzheimer's disease is a progressive brain disorder that leads to loss of memory and thinking skills. It starts with mild forgetfulness and difficulty finding words, then gradually affects daily activities. As the disease advances, people may have trouble recognizing familiar places and people. Changes in brain cells cause a decline in judgment and problem‑solving abilities. Over time, the ability to communicate and move independently becomes increasingly limited.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-524581-14-00Protocol codeACT23645Estimated enrolment1 066 patientsSponsorSanofi-Aventis Recherche & Developpement

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