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- Thank you very much.
It's a pleasure to be here and thank you for the invitation
to speak today.
My name is Justin Ichida.
I'm an associate professor
in the Department of Stem Cell Biology
and Regenerative Medicine at USC.
I'm gonna tell you about a new program that we have
trying to develop a drug for coronavirus infection.
I think, you know, probably like a lot of scientists,
we were
not
working on viral
drugs or
biology at all
when the pandemic hit, but
we found something that was,
you know, that we were working with
that was extremely relevant, I think, to
COVID-19.
And I'll tell you about that today.
So, you know,
what we're primarily doing in my lab at USC is to,
to make new therapeutics or drugs for Lou Gehrig's disease
or ALS.
Our approach is very Stem cell based so we
generally
use
patient blood
to create Stem cells in a Petri dish,
which we can then coax to become any cell in the body,
and for us we coax them to become
the types of nerve cells that are lost in ALS patients.
These cells are called motor nerve cells.
And what's remarkable about these cells is that
once you create them from ALS patients,
they actually mimic the disease in a dish.
So you can see them degenerate over time,
faster than those from healthy controls
and
that allows you to search for new drugs
that might help ALS patients by screening through
all of the drugs that are available
and finding the ones that best,
you know, rescue the survival of those
ALS patient nerve cells in a dish.
And so that's one of the projects that we've
really been doing in the lab over the past several years.
And when we did that project,
one of the major findings we had was that we found that
blocking the
activity of a specific enzyme in the cell called PIKfyve
was one of the most effective ways of preventing ALS
patients nerve cell death.
And you can see that in this picture here,
all of these white cells
are motor nerve cells from an ALS patient.
And you can see with placebo, there was really no effect,
there was really a large loss of the cells,
but with this drug called the PIKfyve inhibitor,
you can see that we preserved many of these.
Now, one thing that's important is that
the known or existing PIKfyve
inhibitor
chemicals
that are out there today,
none of them are really suitable for using in humans.
The reason is because they're very unstable in the body.
They don't last long enough to really
elicit their therapeutic benefit.
So we have been working in our lab
and with a startup company called the AcuraStem
to make a new PIKfyve inhibitor
that can last for a long time in the body
and therefore,
you know, block the activity of PIKfyve in humans
for the treatment of ALS.
Now, what happened was once the pandemic hit,
people had, you know, really scrambled to find
if there were any types of known chemicals
that could block coronavirus infection,
and so some of the folks down in San Diego
did a
screen
and they tested
all known chemicals,
including the FDA approved drugs,
all known chemicals that had ever been tested
at some point in humans,
there are 12,000 of these,
and they looked for things that
blocked coronavirus infection in cells in a dish.
And what they found was that the same
type of chemical that we had found to be
effective at rescuing ALS motor nerve cells
was also the most
potent
way to block
coronavirus infection.
And this is their results.
And basically all you need to know is that
each of these boxes represents one experiment
and as you go from left to right,
they're increasing the amount of these different drugs
that you have on the right here.
And as you go, as you increase in concentration,
when you get to the yellow boxes,
that means the virus is being blocked
from infecting the cells.
And you can see that this PIKfyve inhibitor,
Apilimod,
blocks the cells from being infected
much earlier at much lower concentrations
than any of the other chemicals,
including the one drug here, Remdesivir,
that has already approved for,
has been shown to clinically
reduce coronavirus infection.
So this type of drug, this PIKfyve inhibitor
is about 20 or 30 times better at blocking viral infection
than the drugs that we have today.
And so we thought that, wow,
we should really test our new PIKfyve inhibitors
that we're making that can now survive for a long time
in human,
in the body for the ability to block coronavirus infection
and we should move this towards the clinic.
And so that's the project that CIRM
funded
for us to do.
And so the question is why does it block infection?
And this cartoon can help to illustrate that.
So this is just a picture of a cell that's been
kind of chopped in half,
and you're sort of looking at a cross section of the cell.
And what you'll see is that
the virus can enter cells in two different ways.
And I'm gonna concentrate primarily today on this
late pathway.
There's also an early pathway which I'll briefly mention.
So the late pathway,
this virus comes along to the surface of the cell,
it binds to a specific protein on the cell,
and then it gets engulfed into the cell,
but it remains in this lipid,
this membrane and closed vesicle where it's trapped.
And it actually can't get out of this
and start replicating within the cell unless
something happens.
So what happens is that enzyme that I talked about, PIKfyve,
it helps to get this vesicle to fuse with another type of
membrane and closed vesicle called the lysosome.
When that happens, some of the proteins in the lysosome
can actually activate this virus
to be able to crawl out of that vesicle
and when it does that, now the virus gets released into the
rest of the host cell and it can replicate and amplify.
So if you block PIKfyve activity,
this virus remains trapped in these vesicles
and never can replicate and really fully infect the cell.
And so that's how we're blocking the infection.
What makes the virus, the coronavirus tricky
is that it has a second way of infecting cells
called the early pathway.
And so in reality, I think we'll need to block
both of these pathways to really
completely block the infection of the virus.
But today we're working on this late pathway.
So as I mentioned before,
the existing,
the best existing
PIKfyve
inhibitors,
they're chemicals that are similar to drugs
but they're not really fully drugs
and the reason is because as you can see,
one example of that type of molecule,
it's called apilimod in the blue line,
you can see that when it goes into the body,
it drops to below effective concentrations
within just a couple of hours.
So as you can imagine,
that's not very effective at blocking infections.
But the new inhibitors that we've made
have a substantially longer lifetime in the body
and so we believe that they could actually be effective
against the coronavirus infection.
So one of the drug candidates
that we've made called ASR-149,
we've tested it now
in the CIRM project, we've tested it to see if it can
actually
inhibit
the PIKfyve
enzyme in the body.
We've tested this first in mice here.
These are just a cross section of lung tissue
from mice and everywhere where you see these green spots
here,
these are evidence that the drug ASR-149
is actually inhibiting PIKfyve in these lung cells.
And so what you notice is that with ASR-149,
you see a lot more of the green spots,
which really indicates that it's getting into the lung
where the coronavirus would normally infect
and it's blocking the PIKfyve activity
in those lung cells.
So that is very promising for the ability of it to hopefully
block coronavirus infection in people.
What we've done besides that
is go into now making sure that
our new PIKfyve inhibitor
called ASR-149,
still inhibits PIKfyve with high efficiency.
And so this is an example of that where we have
a slightly weakened version of the coronavirus that
doesn't replicate
and so we can use it safely in our lab at USC.
And then we would compare its ability to-
We compare the ability of that coronavirus to infect cells,
if we had, you know, either a placebo control,
which is called DMSO here,
or our ASR-149, you can see that
ASR-149 severely blocked infection of the cells.
Remdesivir did not block infection in this case
and we didn't expect it to because although it works
in humans, it works by blocking the,
the viral replication process,
and since these are replication defective coronaviruses,
we're just looking at one, a single infection of cells,
and so we're not looking at replication at all.
So we didn't expect Remdesivir to work
and it definitely didn't.
But the bottom line is that ASR-149
was very effective here.
So let me take you one step further,
we tested it against real live replicating coronavirus,
and this had to be done at a special facility in Utah.
And what they found is that
they're looking at,
in this case, they're looking at the ability of coronavirus
to block infection and so
the higher you go on this,
y-axis, means there's more blockage against the virus.
And you can see that as we went higher in the dose
of 149, we got to a point where we limited-
We blocked infection by a hundred percent
and this was about
100
or 200
times more-
We needed about 200 times less drug
that the amount that actually starts showing toxicity
to the cells themselves.
And so this is a very nice therapeutic
window where we don't cause any toxicity
in the area where we're really already blocking the virus.
And so this means that our drug,
if it's delivered to the cells of the right concentration
will definitely block the coronavirus infection.
So what we're doing now is
taking this one step further where we've
worked with our colleague at USC,
she's another professor, her name is Ya-Wen Chen,
and she's a stem cell expert of a different sort.
Remember that as we used stem cells
made from patient's blood to make motor nerve cells,
she specializes in making lung tissue from these stem cells,
and so what she's made are these miniature lungs in a dish,
and she's shown that if she makes a coronavirus that
encodes a little protein that makes
the resulting infected cells green,
you can see that it infects these cells all along here
and makes them bright green.
And so now what we can do is test to make sure
that the drug blocks coronavirus infection
in miniature lungs
from humans,
and we can determine if there's any variability
between different types of people
and the ability of this drug to block infection
into their lung cells.
And coincidence with that,
we're also testing this in some small animal models
like the hamster who-
The hamsters get infected very well by the coronavirus
and so we can make sure that the drug
blocks the ability of the coronavirus to infect the hamsters
and if that looks good,
we will be moving quickly towards clinical trials.
So in conclusion,
the key points are that,
you know, the coronavirus enters cells through both
an early and a late pathway
and blocking an enzyme called PIKfyve
is one of the most potent ways of blocking the late pathway.
And so we've,
unfortunately the drugs that are-
The chemicals that are existing for blocking PIKfyve
are not good drugs,
so we developed a new PIKfyve inhibitor,
although we were planning to use it for ALS patients,
we are now trying to see if we should repurpose it
for blocking the coronavirus infections,
treating COVID-19 patients,
and what we know so far is that
like some of its predecessor chemicals,
it potently blocks coronavirus infection in the dish,
so we've preserved the antiviral activity
and we've given it a better longevity in the body,
so we think it's a drug that could work quite well.
So in conclusion I'd just like to thank the people in my lab
Who've contributed to this work,
Yichen and Manuel have been the major contributors
in my lab.
Monica Zhou and Wen-Hsuan Chang have been key
contributors from AcuraStem
and our collaborator at USC, Ya-Wen Chen,
has now provided us these miniature lungs in a dish
for us to test the efficacy.
And the majority of this work has been supported by CIRM
as well as some of our other funding agencies.
So thank you very much.
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