Striatal Blood Brain Barrier Opening in Parkinson's Dementia

[00:00:41] Dr. Pineda-Pardo: Thank you for the introduction, Sara.

[00:00:44] Dr. Sara Schaefer: The first thing that comes to mind when thinking about the blood-brain barrier, for me at least, is usually that it protects the brain against pathogens and toxins and other insults from outside the brain. However, it is also clearly critical to think about it when we think about how to deliver [00:01:00] medications to the brain, which is more the focus of where this study came from.

Can you talk a little bit more about that?

[00:01:07] Dr. Pineda-Pardo: Yeah, you are totally right, sir. Actually the thing is the BBB, the blood-brain barrier is there for a reason. It's to prevent the entrance of pathogens, toxins, and to selectively permit the entrance of nutrients and other things. But the fact is that most trials for neurodegenerative diseases fail in the search for an effective drug therapy.

One of the reasons for that has been attributed to be the blood-brain barrier, the low permeability or high selectivity. Alternatives to our procedure, to low intensity focus ultrasound So to increase the permeability of the blood-brain barrier might be either too unspecific or too invasive.

So this way we think this is a good way to go. And the possibility of toxins or pathogens that might cross the blood-brain barrier, and this a risk to consider, this is not neglectable, but in case we find a way to deliver a potential effective drug the benefits might exceed the risk, for sure.

And another thing is that well, the reason [00:02:00] why most of the studies that we are seeing are safety trials are because of that. Because we need to consider all the possible factors of these type of interventions.

[00:02:07] Dr. Sara Schaefer: A lot of the drugs that we're starting to talk about are being looked at with intrathecal administration in order to try to avoid the blood-brain barrier as the issue. And even as you said, with the intrathecal administration, there's the concern about how deeply it penetrates into the brain. What parts of the brain are actually being affected by this drug? Is it even getting to the striatum and in what quantities. And of course there's always the patient not being super excited about getting a lumbar puncture all the time, right. So this does seem pretty critical moving forward.

Tell us about the previous studies that have looked at transient opening of the blood-brain barrier in specific brain sites and in specific populations.

[00:02:49] Dr. Pineda-Pardo: Well, using this technology, so low, intensity focus ultrasound. We can distinguish like two lines of, clinical research for opening, for inducing a permeability of the blood-brain barrier. And these are like a cancer [00:03:00] research line for brain cancer through the brain cancer and neurodegeneration.

I want to distinguish this too, because they're following like two different parts and also it is clearly neurodegeneration. So in cancer research, we saw the first papers around 2016 with the invasive devices. And this followed by another publication in 2019 and so on. And the thing is that in these cases, they are targeting the tumor and the peritumoral area, and their objective is quite clear to increase the permeability of the blood tumor barrier to deliver chemotherapy, monoclonal antibody therapies.

And they can go really fast because they do not be as conservative as we have to be with neurodegeneration. This is clearly a one path, and they're advancing a lot. In our case, in neurodegeneration. I will say that the western preclinical experiments in Queensland, they demonstrated that the opening by itself will have an impact in the clearance of beta-amyloid.

They, show this in mice and actually they, even show that the mice are improving in certain tasks, right? So this was definitely a trigger for the trials in neurodegeneration. And this was followed by the first report by Lipsman in, Nir Lipsman in Sunnybrook in [00:04:00] Toronto.

They show in this paper, they performed the opening in patient with Alzheimer disease. And they were able to successfully open the, blood-brain barrier and the white matter. And this was safe, this was well curated and this was followed by another works by in other groups.

Another working in ALS, in cortical regions. And another work in Parkinson's disease dementia. The thing they have in common is that they were targeting cortical areas. Well, hippocampus, but in general, superficial cortical areas.

So these were small targets. So the aim here was to target small regions, for the safety of the procedure and the tolerability. And one of the results that came out of this publication was the replication of the findings by Leinenga. So they showed that the opening by itself alone was able to reduce the amyloid burden. So the thing was found in mice, was replicated in humans, in Alzheimer's disease patients. So this was a good thing. The finding were well moderating magnitude, they were not huge in terms of the amount of amyloid reduction but worse in Africa.

So this [00:05:00] is a, kind of a summary of the early trials before this one, by ours that has been recently published.

[00:05:05] Dr. Sara Schaefer: Yeah. That was one of the most surprising aspects of the paper for me was learning that just opening the blood-brain barrier with focused ultrasound has been shown to reduce beta amyloid deposition in those areas. I have two related questions. One is, what is the proposed mechanism for that and has this been explored in other depositions of proteins like alpha-synuclein or tau.

[00:05:29] Dr. Pineda-Pardo: So they're having to propose well, by us, and by all the authors that have explored these two main mechanisms for possible mechanisms for this. One is the lymphatic system. So, opening the blood-brain barrier alone may have an impact on the lymphatic flow just by facilitating the flow of cerebrospinal fluid into the cardiovascular spaces and into the parenchyma and so on.

So this is my suppose boost in the process of clearance amyloid. Actually, we know that beta amyloid accumulates extracellularly and one of the possible [00:06:00] reasons for ventricular accumulation might be the dysfunction of this system, right? So if by just performing, opening, so by just increasing the permeability of the blood brain barrier where, pushing this flow might be facilitated in this clearing process.

And the other mechanism that has been proposed is the inflammatory response of microglial astrocytic activation, that we know that it occurs after BBB opening. So for the restoration of the barrier and so on. Also, for the treating of the toxin of pathogens that might have crossed.

So this, this, this inflammatory response may have something to do with the clearance. The other thing you ask, so for alpha-synuclein and tau to my knowledge, accumulates only intracellulary. So if these two mechanism are the ones responsible or the ones related to the BBB opening. Probably they will have little impact on the clearance of these two proteins. So I guess that in this case, we'll need to combine the opening with some specific drug therapy or so.

[00:06:54] Dr. Sara Schaefer: So what did your team hope to add to this data with your study?

[00:06:58] Dr. Pineda-Pardo: Yeah. So [00:07:00] actually a couple of things. Well, first study as you know, from the abstract and so on, that the idea for trial was not to confirm this, but to show safety of this. Actually, these are the pilots of this type of trial until now, but to add upon these findings we expected to contribute to the evidence, which in my opinion, is still moderate.

So the idea was to contribute to the moderate evidence that I considered still there for, the PET amyloid reduction related to the opening alone.

So actually in addition to the two positive findings, we have in Alzheimer's disease, there was a negative finding by one of the earliest reports by Nir Lipsman. I think that all results give some more to contribute to this degree of evidence. But also the idea here is to test this hypothesis of amyloid reduction in a different pathology, which is Parkinson's, it is about dementia in which amyloid accumulation might follow a different mechanism or even marking and so on. And on the other hand, I like also to stress out that this was not the main outcome. The main primary outcome to study or idea here was to test for feasibility and reversibility and safety, which are like the main [00:08:00] pilots of this type of early BBB open trials.

[00:08:03] Dr. Sara Schaefer: Tell me about the protocol of this study.

[00:08:05] Dr. Pineda-Pardo: Yeah, this was pretty much the same as the previous one in terms it was prospective, exploratory, open level, single arm, phase one safety and so on. So it's basically exploring the safety of the procedure in the same cohort of patients that we published in 2019 in Nature Communications.

The difference was the target, so that we were targeting here, the posterior the postcommissural putamen , and also the extent of the target. So in the previous report, we performed small openings. So small volume of area was targeted, and here we extend it to the whole posterior putamen with a large opening. And well, the idea was to test the safety of this procedure.

And we did that in a cohort of seven patients that were treated twice, like two weeks apart. So this was again, the same as the previous one. And the primary outcomes were what? Most of them were safety outcome, so clinical outcome, the MDS-UPDRS neuropsychological battery, exploring all [00:09:00] cognitive domains, MRI to test the possibility of the opening, inducing some small MRH or edema.

And another thing we are having here as we were targeting the putamen , which. Which I didn't say, but for us, of course, for Parkinson's, this seems like a very meaningful target if we want to restore the dopaminergic denervation with any kind of drug we can imagine. So in here we decide to add FDOPA PET for positron emission tomography, just as a measure of safety, not as a measure of potential benefit.

Also because the idea of opening, inducing a potential Impact into the SWI sewquence is something that needs to be assessed. And this is why we included it. So we also include the secondary measure to evaluate amyloid. And well, so this were all the safety measures. So anything in there was collected as a safety concern.

And regarding feasibility and reversibility, we use what's been used in most of the trials, which is Gabrielino enhance MRI. Basically this is consisting injecting gadolinium, a paramagnetic contrast you're probably [00:10:00] familiar with all of it. And, so basically seeing, enhancing hyperintensity, in the parenchyma around the target is a positive confirmation of the successful procedure.

And again, the disappear of this enhancement is a positive confirmation of the restoration of the blood-brain barrier.

[00:10:15] Dr. Sara Schaefer: Thanks for that great overview. What were the results with regard to the primary outcomes, which again, were safety, feasibility and reversibility.

[00:10:25] Dr. Pineda-Pardo: So feasibility and reversability we're pretty much confirmed and basically we confirm capacity to induce opening in the posterior putamen. And the restoration of the opening was confirmed in most of the cases 24 hours after the procedure. And in some cases this is something that has not been seen before.

Actually, we saw that in few cases, 24 hours after the procedure, there was still some enhancement with dotty appearance, like small spots and this seem to be co-located within paravascular spaces. So for some reason there's still some minimal leakage within the paravascular spaces, but [00:11:00] this, will monitor this in subsequent follow ups of this upcoming year. And this was feasibility and reversibility and about safety, basically, we didn't see any major or serious adverse events for the patients. No clinical or neuropsychological permanent change was observed on the patients. And in the MRI we did observe a couple of things. There is one thing that's has been reported by us and by other, which is what we call T2 Hyperintensities.

It seems that in some cases maybe related to a higher dose of ultrasound and opening we might see a small hyperintensity in T2 Star, which seems to be related from histological studies. That study was published recently in PNAS, seems to be related to extravasation or red blood cells.

At the end, we are opening the blood-brain barrier and as you said at the beginning, many things can come out and for some reason the blood cells might come out and this will affect the T2 star images. In any case, this didn't have any clinical corrections, so we didn't have any clinical event associated to it.

And this seems to be attenuated along, follow up. So it's something we see in acute [00:12:00] evaluation, but seems to be attenuated in longer follow ups. And in our series we also saw two patients with, with mild edema. This is something that we follow and it resolved. This was mild vascular edema, but it's, again, this is something that maybe actually we'll do when you are performing larger BBB openings, Which are disrupting the blood-brain barrier in a larger volume.

So fluorodopa, we didn't observe any change. This was, again, as I said before, a safety measure, but we observed a non-significant, but an average increment of fluorodopa activity. We do not have an explanation for that, but it was intriguing. We saw that this increment was correlated with reduction in amyloid. So there was an intrinsic mechanism that relate this to, but we don't have an explanation for that. But it still was interesting. Something that needs a further exploration.

[00:12:44] Dr. Sara Schaefer: So we talked about the results of the primary outcomes, but what about the exploratory outcome of the study? What were the results of that?

[00:12:53] Dr. Pineda-Pardo: As I said, we acquired FDOPA, to evaluate the impact of the opening in the posterior putamen regarding [00:13:00] amyloid burden. And in our case, we find an unexpected finding, but higher in magnitude, than we were expecting. Based on the previous report, we found that the average chain was close to 20%.

Which was higher than in previous studies. And not only this, we also found that there was a data association, so significant correlation between the enhancement on the gadolinium contrast T1w-Dd images, so the enhancement we saw in the target and the reduction in amyloid. So finding this significant association help us to establish a link between the procedure itself.

So between the opening of the blood-brain barrier and the reduction in amyloids that we are seeing in this patient.

[00:13:37] Dr. Sara Schaefer: So interesting that you were able to see that correlation even with such small power in the study that that was still statistically significant, that the more gadolinium enhancement there was, and therefore the more blood-brain barrier opening there was the greater the reduction in beta amyloid deposition.

Some of the patients in the study had [00:14:00] a unilateral target twice. While others had a unilateral target, followed by bilateral targets. You do explain this a little bit in the paper, but can you just tell our listeners why there was that difference and did their outcomes differ?

[00:14:14] Dr. Pineda-Pardo: So the reason for that is, was to increase safety testing gradually. So the plan was to go first with something that might be like one step farther from the previous experiments. So going to another target in two separate sessions.

So we test the safety of repeated procedure in the same target, and once we confirm that we decide to increase complexity or to increase extent of the targeting. So actually bilateral targeting is with this type of procedure, it's not something that requires a super methodological change.

So actually it's pretty much the same procedure. It just increased a little bit in in time maybe higher dosage of micro bubbles. But this is why we did it in separate blocks, in first three patients and second three patients to the other arm.

[00:14:56] Dr. Sara Schaefer: So going off of that, the patients in this study underwent the [00:15:00] procedure twice, either unilateral, followed by unilateral or unilateral, followed by bilateral, and were followed up for six months. Do you have any concern that the reversibility or safety might be less favorable with longer follow up?

It sounds like potentially not since you followed any patients who still had gadolinium enhancement or edema to determine that there was resolution. or do you have any concern with an idea of multiple focus to ultrasounds procedures as presumably in order to administer treatments to a patient, it's unlikely to be a one and done type of situation.

[00:15:37] Dr. Pineda-Pardo: The one and done will be ideal, actually, well, based on our findings, I do not foresee like there might be expectancy for issue, that it's reversibility or safety longer follow up. So that we decide to, finish or follow up like six months. But the patients were completely fine. Also the other reports do not see a reason to expect a change in that. I do think that's important, what you also [00:16:00] commented about repeatability, So imagine this procedure, it has to be repeated like once a week during one year for a specific treatment. I see this as a real challenge. This is something that in neurogenetics disorders has not been tested. The maximum number of treatments that have been performed for same target three, well, two to three, one paper was three, and most of the rest were, were only two sessions.

So extending that into, 10, session or 20. My compromise vasculature, I don't know how. But, this is something that for sure will need to be tested. But I will say that everything is a matter of trade offs. So if we have a potential drug for which we expect a certain clinical benefit, we might consider evaluating a trade-off between one risk and the other and considering maybe one exposure to life of BBB opening once a month or one every two months. I don 't know.

But for sure the goal here, as I see it and as some other colleges and research in this area see it, I guess the goal here for neurodegeneration is to go for a one and done thing.

[00:16:56] Dr. Sara Schaefer: You have high aspirations!

[00:16:58] Dr. Pineda-Pardo: Yeah, of course, [00:17:00] of course. But this is what I would like, and this is what we are exploring.

And not only as, but others. I guess that the developments in gene therapy will be the other thing to aim towards. I think this, could be a goldmine so that we are having a single limited impact into the blood-brain barrier and an effective long lasting effect. This is what we aim for, but we will see.

[00:17:19] Dr. Sara Schaefer: The gold at the end of the rainbow.

So moving on to limitations of the study. Clearly power was a limitation and was, less than 10 subjects. What other limitations did you identify and what might the next steps be? And related, and you kind of got into this a little bit, but how do you envisage this technique being incorporated in the future?

[00:17:40] Dr. Pineda-Pardo: Lack of power is one thing, or inside sample site was seven patients. But I want, before going to other limitation, I want to say that in here, one must consider that we're not giving any therapeutic expectations to the patients, right? So it's very difficult to recruit patients for these type of trials. And compared to other [00:18:00] reports, seven patients was limited but adequate in terms of testing safety, but major limitation in this study was and I guess also for many other studies, and we say it in the paper, it was the covid lockdown. It was just in the middle of the study.

And it was something that probably mask potential result that we could have seen in cognitive impact of the procedure? I don't say we will expect of course a cognitive improvement. I cannot say that I do not know, but this is something that definitely covid lockdown has masked out. And there are other limitations. There are most of them technical and we'll see in the coming months. A lot of improvement in this area. We are already seeing it in terms of controllability. Right now we are performing openings of the blood-brain barrier, a large target, but we do not control how homogeneous are these opening or what type of drugs in terms of molecular weights or solvability are gonna be able to cross.

And in this regard, there are many things like the flow, the influx of drug that will go through the BBB , et cetera. So in our group, our next step will be to continue testing safety for other indications, [00:19:00] targets, or pathology or so on. But definitely the objective here for us and for others is to include pharma development.

So we need to invest potential drugs that might benefit of this type of procedure. And definitely this is key in order to go for the success of the technique. And what's the second thing you ask was?

[00:19:15] Dr. Sara Schaefer: If you had a crystal ball, what would you see in your crystal ball?

[00:19:19] Dr. Pineda-Pardo: So that's a very simple thing as an ambulatory procedure that can be performed fast without need of, right now we are using a head frame as fixated in the patient without a frame, a fully controllable system that you just program. I want to deliver this concentration of drug into this area in the brain.

The system will estimate how much energy, how much micro levels everything in order to deliver this specific amount of drug into the brain. And something, of course, that can be repeated several times without compromising the vasculature. But what I really do see, and I do not near a crystal ball, and we will probably see it soon, I think for the studies that I've been seeing around. Is the entrance of this into the brain cancer treatment with a combination with chemotherapy.[00:20:00] I think this is the more direct future incorporation into clinics. But of course, I mean, our aim is to offer gene therapy, and we're working.

[00:20:06] Dr. Sara Schaefer: Thanks for this enlightening conversation. I learned a lot even above and beyond reading the paper itself.

[00:20:12] Dr. Pineda-Pardo: Thank you very much. Thank you for the invitation, and if you let me, I will also would like to thank my team. This is a team workforce, so it's not a single person and I would like to thank them all.