Last updated on February 2018

Blood Brain Barrier Opening in Alzheimer' Disease

Brief description of study

In Alzheimer's disease (AD) an imbalance between the production and clearance of the -amyloid peptide is hypothesized as the driving event of the disease. The decreased clearance of A could be partly linked to a progressive dysfunction of the brain vasculature and of the blood brain barrier (BBB). Among many possible explanations for these failures of the multiple clinical trials evaluating innovative drugs in AD, one is the lack of target engagement, as none of these drugs is able to readily cross BBB. This barrier acts as a wall that actively and passively prevents the crossing of molecules between the blood and the brain parenchyma compartments. Only 0.3% of intravenously injected anti-A immunoglobulins reach the brain despite a half-life of 15-20 days. Low intensity Focal ultrasound associated to microbubble injection can open the BBB in a non invasive way. These openings are reversible in 2 hours to 2 days depending on the intensity of the ultrasound. Ultrasound opening of the BBB was initially used in a transgenic mouse model of AD to increase the brain delivery of an anti-A antibody. In this article, the A load was reduced in ultrasound treated brain region. Surprisingly it was then demonstrated that the simple opening of the BBB without any adjunct anti-A treatment was able to drive the same A clearance effects. This is probably linked to endogenous antibodies that are able to penetrate the brain parenchyma and target A plaques. Four opening sessions elicited positive promnesic effects in these mice. Our group conceived and developed a mean to easily, reproductively and innocuously open the BBB. A unique extra-dural ultrasound emitter (sonoCloud) is surgically implanted in the skull under local anesthesia. It emits low intensity contact ultrasound (LICU) that are not deterred by bone and thus are able to open the BBB.Preclinical studies show the SonoCloud device is safe and efficient as it allowed reproducible and repeatable opening of the BBB in rabbits, dogs and non human primates. Drugs up to 2000 Kilo Daltons (kDa) are able to cross the BBB to reach the brain parenchyma in which the concentration of Carboplatin was increased by 700% in the BBB opened region. No adverse event was evidenced both clinically, by EEG, Evoked potential, MRI, 18 Fluorodeoxyglucose (FDG) PET and histology in the primates after 7 bi-monthly sessions of LICU BBB opening. SonoCloud and its external generator have been certified by the academic start-up CarThra (APHP, UPMC). Our multidisciplinary skills (neurology, neurosurgery, neuroimaging, basic science departments in the same University hospital setting) and our previous experience of BBB opening in Man give us the unique opportunity to translate this procedure from neuro-oncology to AD which could

  1. Have a positive effect on brain lesion load and symptoms by itself and 2) allow anti-AD (or more broadly, central nervous system) drugs to engage their targe

Detailed Study Description


Alzheimer's disease is the most prevalent neurodegenerative disease totalizing 33 million patients worldwide. If nothing is done to decrease the incidence of 1.8 Million patient/year, the prevalence will double in the next 20 years.

Physiopathologically, the amyloid cascade remains the predominant hypothesis. It states that an imbalance between the production and clearance of the -amyloid peptide is the driving event of the disease, leading to Tau hyperphosphorylation and accumulation in neurons as neurofibrillary tangles, neurodegeneration (synaptic and neuronal loss) and cognitive impairment. The decreased clearance of A could be partly linked to a progressive dysfunction of the brain vasculature and of the BBB.

New sets of diagnosis criteria for AD have been proposed to address the low specificity (70%) of the previous ones, that could be one of the causes of failure of previous clinical trials. Among these new criteria, cerebrospinal fluid (CSF) biomarkers and positon emission tomography (PET) with new ligands of amyloid plaques and more recently tau deposition are indicators of the underlying histopathology of the disease, and can also be used to evaluate early intervention efficacy as they are pathologic in the preclinical phase of AD, its prodromal phase.

the investigators aim to test an innovative BBB opening procedure that could drastically decrease AD patients' brain lesion load and alleviate their symptomatology.

Scientific/medical questions:

  1. What is the tolerance of LICU and the SonoCloud device in a population of patients with mild AD? 2) What are the physiopathological impact of LICU BBB opening in these patients as asserted by amyloid and 18FDG PET-MRI?

For the first phase I clinical trial in the world using LICU in AD to repeatedly open the BBB.

Primary objective: To evaluate the tolerance of the BBB opening session in 5 AD patients (Adverse event recording, cognitive and MRI evaluations).

Co-primary objective: To assess the impact of BBB opening on the hallmark lesions of AD (A & Tau) through PET-MRI imaging (decrease of the standardized uptake value ratio (SUVR) after vs. before treatment in the left supramarginal gyrus and left (treated) vs. right (untreated) supramarginal gyrus).

Secondary objective: increase cognitive performance in AD patients through the repeated opening of the BBB in the left supramarginal gyrus

Methods :

Ten patients suffering from mild AD will be included in the study.

Protocol :

Seven BBB opening session will be performed at a bi-monthly rate focusing on the left supramarginal gyrus, a cortical structure known to be affected by both amyloid and tau lesions early on during the evolution of the disease. All adverse events induced by surgery itself or by the LICU will be recorded. Amyloid and Tau lesion load will be evaluated benefiting from the PET-MRI that allows to clearly evaluate fine changes in SUVR taking into account loco-regional cortical specificity (cortical thickness). PET image analysis.

Mean Standard Uptake Values Ratios (SUVR) will be calculated with cerebellar gray matter activity as reference in volumes of interest. Voxel-wise uptake will then be divided by this reference value to get SUVR maps. PET images will be corrected for motion and partial volume effect thanks to simultaneous MRI acquisition. To analyze the longitudinal PET data, each follow-up T1-weighted MRI will be co-registered to the baseline MRI, and a within-subject template image will be calculated by averaging the coregistered T1-weighted images. This mean image will be used to calculate optimal transformation parameters to Montreal Neurological Institute (MNI) space. Next, baseline and follow-up PET images will be co-registered to the baseline MRI, spatially normalized to MNI using this optimal transformation, and scaled with cerebellar gray uptake. Individual percent annual changes maps will be then calculated. These maps will represent the voxel-wise calculation of percent metabolic change after BBB opening.

The investigators think that the clinical trial will be well tolerated by the patients as the rate of local adverse events is expected to be 1% since the SonoCloud device implantation is extra dural (without dura opening). The implantation is performed under local anaesthesia in an outclinic fashion.

Drawbacks and possible solution to overcome the problems :

Among expected drawback the investigators will have to be very vigilant for Amyloid related imaging anomalies (ARIAs) due to the sudden entry of endogenous antibodies in the brain parenchyma of patients with A and Tau prevalent lesions. If these ARIAs were to happen, an amendment of the protocol could be devised to add steroids, or reduce ultrasound intensity, or extend time during each opening session, or reduce number of BBB opening session, or in last use immunosuppressive drugs prior to the opening of the BBB.

This is the first study worldwide with the means to safely, repeatedly and reproductively open the BBB in AD, or more broadly, in any neurodegenerative disease. It is noteworthy to consider that it is only a phase I study aiming to demonstrate the feasibility of the technique in a mild form of AD. If this is the case and even in the absence of a positive effect on the lesions and symptoms it will then be possible to propose new projects aiming to associate these safe BBB opening to anti-AD drugs. In fact, this study could pave the way for further treatment venues of various neurodegenerative disease that share a brain accumulation of proteins that cannot be readily targeted in case of BBB integrity.

Clinical Study Identifier: NCT03119961

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