Dr Manish Shah (Host): Welcome to Weill Cornell Medicine, CancerCast
conversations about new developments in medicine, cancer care, and research.
I'm your host, Dr.
Min Shaw, and today we will be talking about prostate specific
membrane antigen or PSMA.
Therapy for prostate cancer.
Our guest today is Dr.
Scott Tagawa.
Dr.
Tagawa is a friend of mine for many years.
He is the director of the Genitor Urinary Oncology Program and medical Director
of the Genitor Urinary Oncology Research Program at Weill Cornell Medicine.
New York-Presbyterian Hospital.
He's a global leader of drug development and PSMA, targeted
therapies for prostate cancer and has led numerous clinical trials in
prostate, kidney, and bladder cancer.
Dr.
Tag's work has led to several therapies receiving FDA approval,
and he is a key opinion leader.
Genital urinary malignancies and he actually led a very pivotal phase three
study that was recently published in a conference in Germany, last year.
So, Dr.
Tagawa Scott, welcome.
Dr Scott Tagawa: Thank you very much for the invitation.
Happy to be here.
Dr Manish Shah (Host): So let's start off with, just some
basics about prostate cancer.
and, how it develops, how it's initially treated.
just for our general, audience.
Dr Scott Tagawa: for the general audience, for those that don't know, the
prostate is a gland that sits between.
The bladder And the urethra, that's how we urinate, kind of coming
out of there next to the rectum.
and, outside of, skin cancers that are associated with sun is the most common
site for cancer to develop in someone who was born with a prostate, generally talk
about men with, with prostate cancer.
fortunately.
most of the patient's that actually are diagnosed do not actually die
of prostate cancer, although because it is the most common cancer, it
is always in the top two to three in terms of, cancer deaths in men.
The main point is that the majority of patient's actually are diagnosed, either
I diagnose with a cancer that we can watch closely called access surveillance
or intervene and treat with typically surgery or radiation or something that's
to the prostate itself that then leads to control for the rest of their life
And the patient dies of something else.
But unfortunately.
Some of them walk in the door with cancer That is already spread or develop
recurrent disease And that that can lead to death and just 'cause of the
numbers, of being the most common, is almost always in the top two to three.
causes of cancer, death due to cancer in men in the United States.
Dr Manish Shah (Host): I'll take a step back and, walk through that a little bit.
So, through the last several podcasts, I don't think we've
actually defined what cancer is.
it is essentially, an uncontrolled growth and There are some cancers
that are benign, meaning that you have uncontrolled growth, but it's
really self-limited to that area.
It doesn't spread anywhere.
and there are some cancers that are very aggressive.
Where, even a little bit of growth And then it starts to spread And then grow
in those other places that it spreads.
And I think what you heard Dr.
Tawa say is that, the prostate, this gland that it lies, in the pelvis
between the bladder And the urethra.
and as your urine flows, it goes through the prostate.
So, oftentimes people.
They may have what we call benign prostatic hypertrophy, so a little
bit of growth in the prostate.
It's not cancer, but it can cause a little bit of blockage, And so
people may have difficulty urinating.
So that's a very common thing that happens when there's cancer in the prostate.
It can be.
quite indolent and low grade.
and that's what, I think he meant by saying that you might have cancer, but
it won't actually, change your survival.
you'll die of other diseases, heart disease or whatever else because,
the cancer itself is very indolent.
It's not gonna spread.
Or it could be managed very directly with.
Local treatments, but, because it's so prevalent, a small proportion of patient's
who develop, more aggressive prostate cancer, that's actually the main topic of
what we're gonna, be speaking about today.
because prostate cancer is so prevalent, small number of patient's
that have the more aggressive type, is still relatively prevalent.
Is that right?
Dr.
Tagawa
Dr Scott Tagawa: that's correct.
I would say most of the time we can tell, which category A.
Tumor slash patient is going to fall into.
and that's partly because of development through research, in terms of looking
at new things under the microscope, new things in terms of, genes and new
things in terms of imaging or scans.
now we get it right the majority of time, but it's not a hundred percent
and which is one of the reasons we wanna continue the research.
Dr Manish Shah (Host): So tell us about, PSA and PSMA because
that can be confusing as well.
Dr Scott Tagawa: Yeah.
So three letters, for PSA And the same three letters in PSMA, just with
one, so prostate specific antigen.
So prostate, we already talked about specific.
Hopefully people know what it is, but just the idea was that This is
going to be specific for prostate.
Possibly prostate cancer antigen just really means it's a protein.
and that's can be very different things when we talk about PSMA, we're
gonna talk about that as a target, but we just think of this as a protein.
And for PSA, it's made inside prostate and prostate cancer cells that may
be secreted, meaning leaves the cells into other fluids so much of the time.
We use that as something that leaves the cell, goes into blood,
And we do a PSA blood test.
That's the main type of blood test that we use for screening for prostate cancer.
For someone with prostate cancer, we tend to use that for monitoring.
So going up, generally speaking, we say That is bad, stable, or going down.
We generally say That is okay.
That's more consistent with.
Cancer control.
so anyway, that's that protein that starts inside the cell And then leaves the cell.
We just add the letter M in the middle of that.
So PSMA, so the PSA still have the same.
Meanings prostate and specific ingen M is for membrane.
So rather than being inside the cell and coming out, it's stuck to the membrane
or that's the surface of the cell.
so the only way that leaves typically is when the cell.
Leaves, And we can detect that in blood.
So if there's a cell That is circulating in blood that we call a, circulating
tumor cell, one of the ways we can identify that as a prostate cancer
cell is by checking for PSMA.
But what we've learned to exploit over the last several decades,
is using that as a way to both diagnose and treat prostate cancer.
for instance, and This is what has been, the first in terms of FDA approvals is we
can inject something into the blood, it circuits it around and only goes to PSMA.
And what is attached to it is something that lights up.
And we can do a scan.
And the most common way we use That is what's called a PEth scan.
And there's PEth scans that look at sugars, PEth scans, look at other things.
This is one that looks at PSMA.
So this was one of the major advances.
It's really shifted almost everything that we have, with this ability to, detect.
that's called I-P-S-M-A PEth, but PSMA.
in terms of defining that it is what we would call a cell surface protein.
So it's again, this protein that's on the cell but doesn't leave the cell.
It's stuck to the membrane, And we can exploit that to target something
that happens to be, for the most part on prostate cancer and prostate
with only limited distribution in the rest of the normal body.
Dr Manish Shah (Host): that's really a great explanation.
So, Is it the exact same protein, That is intracellular and excreted
versus the one that's membrane brown?
Or is it just happens to be, the same letters, but a, a
slightly different protein?
Like if you had an antibody to PSMA, would it also bind to PSA?
Dr Scott Tagawa: Nope.
They happen to use the same letters and words, but they are.
Different.
So there are forms of PSA, we call 'em RINs.
There are forms of PSA that are really restricted to staying on the cell, but
PSA, which most people recognize as a blood test and can think of as a blood
test, is because it does leave the cell.
So that's P-S-A-P-S-M-A.
That m has stuck to the cell and it doesn't leave the cell.
Dr Manish Shah (Host): And it's a different protein entirely
So, It just happens to be either secreted by the prostate, so PSA
or bound to the prostate cell PSMA.
Dr Scott Tagawa: Correct.
Dr Manish Shah (Host): and you were amongst the first to actually develop
PSMA both I think, as a diagnostic tool and as a therapeutic tool.
is that right?
You wanna tell us about that story?
Dr Scott Tagawa: it starts before me, but it really is a New York story.
So the gene.
Was discovered in New York And the first essentially four antibodies or
proteins that were able to identify and bind viable prostate cancer
cells is also a New York story.
So the gene was discovered, by Skip Heston at SSON Kettering and Neil Bander,
who is a urologist, at Weill Cornell now emeritus, invented the first.
Drug, if you will, That is able to bind to viable prostate cancer cells.
And that has been developed, mostly as a therapeutic, but really led the way
for the diagnostic studies as well.
So diagnostic could be what, we have a biopsy, we're not sure what
it is, and helping the pathologist say, oh, it looks like it actually
is prostate or prostate cancer.
That's one thing, but.
in the real-world for the average patient, the more, important Utility driving.
test is the scan, which we started with antibodies, which arguably
could be better than therapeutics.
We don't actually know this better, we just say different, but for scans it's
a little bit more cumbersome to use the antibody scan where we do the injection
today And we scan several days later.
so the next generation.
Of technology was developing what we call small molecules.
And they're called small molecules 'cause they are literally
smaller than these antibodies.
where we do the injection And then about an hour later we do the scan.
And That is, as I mentioned before, really revolutionized, the
management of prostate cancer and frankly interpretation of all the
other, data we have for therapy.
Dr Manish Shah (Host): this development program, from the
discovery of the antigen And then the application that's spanned over 20
years or so, if I recall correctly.
, Dr Scott Tagawa: Not 30 years in the clinic, but 30 years plus
in terms of discovery And the clinic, really, it's been 25.
Dr Manish Shah (Host): let's talk about, prostate cancer now, And it's treatment.
So, we said, it's an uncontrolled growth and it can, become aggressive and it.
Can require treatment.
We mentioned some treatments already, surgery or radiation
for localized disease.
but then, there are other treatments like androgen deprivation therapy,
chemotherapy, And then even we're gonna get to PSMA directed therapy.
Do you wanna start us off with, how that started, the androgen deprivation And what
that means, and, then go to chemotherapy?
Dr Scott Tagawa: Sure.
Lemme circle back So, one reason that we think um, PSMA imaging
has revolutionized things, is because it really has helped us.
In telling patient's we think it's all in the prostate or not, because
we have a much more sensitive scan.
So I think it's helped both radiation and surgery as well.
But in terms of, drug therapy, as medical-oncologist, what we primarily
do in terms of treatment or, drugs.
What we've, had, led to the Nobel Prize, many decades ago, was, at the time.
Castration.
So initially in mice surgically removing the testicles, And then using estrogens
And then subsequent therapies that will essentially block the production
of the male hormone testosterone.
we use drugs to do that now, both injectable or oral.
Combined, we call that androgen deprivation therapy or a DT,
comes in the bucket of what I would term hormonal therapy.
And when I say that, usually when I say that for the first-time to
a patient, I usually say, well, we call it hormonal therapy.
It really is anti hormonal therapy.
Or overall, either block the production of the male hormone called
testosterone, or we block the binding of that to the main, Problem inside
the cell called the angen receptor.
You can just think of that as the hormone receptor.
Or there's something that circulates in the blood that can stimulate the
cancer to grow, And then something within the cancer that even independence
of the thing that's circulating can cause the cancer to grow and spread.
That is what we call a driver of almost all prostate cancers, especially the ones
that haven't yet been treated and we've learned to block that with different
drugs And that is very successful in terms of, cancer response, where almost a
hundred percent that start off untreated.
We give this type of a treatment, this and/or deprivation or hormone therapy.
And the PSA drops a lot I don't wanna get into the complexities of blocking the
pathway versus actually killing the cell.
It's a little bit of both, but it is successful in that manner almost
all the time that we've now moved on to the next generation of hormone
therapy that we call a RPIs or, RPS for short in case someone's out there.
Listen to one of these that's on the medical parts.
it's just a different way of doing the same thing, either lowering
the production of testosterone or blocking this end receptor pathway.
and nowadays, most often these are combined, so someone
that walks in the door.
With prostate cancer That is spread, it's usually gonna be both
of those types of agents together.
that has been in the last small number of years, traditional backbone of
therapy where sometimes we will also add a third drug and sometimes not.
Dr Manish Shah (Host): so the prostate is a male gland.
it's only in males and So, it kind of makes sense that, endogenous
androgens are like testosterone, for example, but other's as well.
Are important for the growth of the prostate gland.
so a cancer that starts in the prostate, it only makes sense, would be driven
by this pathway, the androgens, And so blocking this pathway by.
doing an orchiectomy or by blocking the androgen production or by an
rp, that will, inhibit any cancer that's driven by this pathway.
So I, think that's, really quite fundamental.
And that actually helps a lot of people.
But at some point the cancers become independent of that
pathway, is that right?
Dr Scott Tagawa: they might be, so independence of the pathway happens
in a fraction of patient slash tumors.
that where they can actually even lose the antigen receptor That is there, that
most often they more become resistant to the pathway, where the pathway is there.
But the cancer learns to activate the pathway in different mechanisms.
So there still is.
The AR pathway, there still is PSA, that's the blood test production.
But despite the A DT And the A RPI, these abbreviations that we have
for the, main horal drugs that we have, the cancer learns to grow.
anyway, that's a distinction to totally losing.
the AR pathway where it can turn into something we call small cell or
neuroendocrine, or aggressive variant.
There's different terminologies that are there most often if that happens.
There is very little, at least relatively PSA, that blood production.
And as it turns out, when we get to the PSA target therapy, if there
is a tumor, which is maybe 10 to 20% of the tumors that are PSMA low.
If that happens, they typically are also this hormonal therapy
resistant, or ar low as well.
Dr Manish Shah (Host): Right.
And so what do we do?
I'm sure it's chemotherapy and other things.
But, walk us through that.
Dr Scott Tagawa: I mentioned the word small cell and one of the reasons we
call it small cells is because the cells look small under the microscope
and they're blue with certain stains.
The most common small cell comes in the lung, small cell lung cancer.
and we've, developed, certain drugs, typically we call
platinum drugs that work in that.
And those types of drugs have kind of been extrapolated to
all the small cell cancers.
Of other sites.
That is part of the backbone is extrapolating that.
So, but overall, chemotherapy is, the general rule is what we will, use.
And often it'll be with a platinum drug So the typical Chemotherapy, drugs for
prostate cancer or what called taxanes.
So those docetaxel.
and cabazitaxel are the two FDA-approved drugs.
Sometimes we'll add a platinum drug to that, or sometimes, we'll, do a kind
of a traditional small cell regimen.
Cisplatin, topside, or carboplatin.
Topside.
You don't have to get into the great details, but anyway, you write in terms of
chemotherapy that we have interesting data from Cornell actually that say the taxane
chemotherapies can also work with Theron.
Receptor pathway, but especially when we add these platinum drugs, these
AR independent or neuroendocrin small cell, is often chemotherapy.
the genes There are associated with that are sometimes a little bit different.
So sometimes we'll take other therapies based upon, the genes.
But they also may have different proteins that are there.
And for instance, there's a protein that's called DL three.
that happens to be a protein That is almost always present
on small cell lung cancer.
And there is a DL three treatment.
It's an immune type of therapy where, there's a drug that half
of it recognizes this DL three.
So binds to the.
almost a prostate cancer cell, the small cell lung cancer cell, And also,
activates or at least influences a T-cell with, CD three, that's part of it.
And that target DL three actually through some Cornell data, in this neuroendocrine,
type of prostate cancer, rather than being there maybe 20% of the time.
in a low level with the average metastatic prostate cancer in this neuron type,
it's may be more like 75, 80% of the time there and more to high levels.
So anyway, That is a target of interest, in this disease state.
There's other ones that, you may be interested in as a GI oncologist,
so I don't wanna get too far.
So chem five is an, area of interest for GI cancers that.
Are typically not there in regular prostate cancer, but
then emerge in this other thing.
So it's an area of what we call unmet need because this unfortunately growing
fraction of patient's that may be, one in five or more will lose the typical,
receptors or targets to hormonal things, PSMA and those types of things.
And we're.
Looking to develop whether they're targeted chemo agents, whether they're
targeted immune agents, whether they're targeted particles of radiation, in
this subset that doesn't have that like we have already done for the subset
that has the typical targets there.
Dr Manish Shah (Host): I wanted to, take a step back and conceptually think
about, how do we treat cancer in general?
and using prostate cancer as a framework.
So we began by saying that, the prostate cancer cells are very dependent on this.
androgen pathway.
so by blocking that pathway, by different means, you can treat cancer that way.
that's the first thing.
But then, Dr.
Tagawa explained that this pathway, even though it may be present, the
cancer cells have learned away.
To no longer depend on the pathway.
so, you need to use different ways to treat the cancer cells.
One way is chemotherapy, And what that does is it, disrupts the
intracellular workings of, key functions.
So we mentioned docetaxel or cabazitaxel.
These are agents that bind to microtubules and stop the function
of microtubules within the cell.
But other chemotherapies might be, agents that actually, target and damage DNA and
DNA is important for cancer cells because.
You need the DNA to replicate, to develop, daughter cancer cells.
So, chemotherapy is another way to, target cancer.
And then the third way, which, we just mentioned very briefly, but we should
spend more time on, is actually radiation, which is high energy, particles or
beams that actually damage DNA directly.
and people have heard of radiation.
what we call external beam radiation where radiation is provided
from an external source And then it's directed into the body.
that's how you treat, for example, localized prostate cancer.
But, one of the exciting things about PSMA.
Is that we're able to now use that target as a way to deliver radiation.
And in fact, that's one of the, most recent therapies that got approved.
first, correct any of this that I got wrong, And then maybe expand on that.
Dr Scott Tagawa: you are notedly correct?
Because while you specialize in gene cancer, you have general knowledge.
so overall, correct.
There is a, type of therapy broadly called targeted radionuclide therapy.
So targeted means it's in some way targeted.
It could be, pushed to a certain area or something that we're gonna
talk about in a little bit, kind of like more of a smart mom where it
circulates and finds certain things.
that's the first t, the second t it is therapy, meaning it's therapeutic,
designed to harm cancer cells.
And then radionuclide just means it's a radio particle, so a small
particle that emits radiation.
And loosely speaking, there's beta emitters, emitters, and al emitters.
I don't think we have to go into that so much, but there's weaker
ones that can travel through tissues and stronger ones that can't really
travel through so many tissues.
to just get, one thing outta the way, the one target is to put it in.
So there's beads, Y 90, but doesn't matter so much that we can infuse into a certain
area, and that's one way of targeting, ignoring that, what most of the, field
is doing now, really coming from eight decades ago, from thyroid cancer learning
that there may be something That is more unique to cancer cells and maybe
an organ such as a thyroid itself.
and something we can put into the body, into the blood and
circulates around and lands in the cells that we really want it to.
And in the case of radioactive iodine, that's thyroid cancer, just
'cause it naturally takes up iodine.
That is the prototypical thing we call in the field of what we call
theranostics, which means that we.
Finds a target that we can take a picture of with a scan And then
use something similar to treat it.
so just to kind of get some terminology outta the way, but PSMA, and there's other
targets that are out there with prostate cancer and other cancers is something
we already talked about, is relatively selected on prostate tissue and prostate
cancer tissue, wherever it is in the body.
We've already talked about that we can inject something that
circuit gets round and only lands in the tumor to light it up.
In terms of scans, well we can attach a therapeutic radionuclide And the approved
one is called Lutetium 1 77 or 1 7 7 lu.
which is one of these be emitters that's relatively weaker, but we get a
bunch together And that can penetrate across cells, And we essentially do
the same thing as we do with a scan.
Except that attached to it is not primarily designed to light up and look
at, And we can look at the therapeutic, but it is designed to go and kill tumors.
So it's a radiation smart bomb that has these tiny radioactive particles
that circulate in the body for some number of hours and wind up in
this PSMA positive prostate cancer.
And doesn't mean there's no side effects, just 'cause it's targeted.
But predominantly the radiation goes into these, tumors.
And the reason it's FDA-approved is because in the first study that
came out in 2021, leading to a 2022 approval, patient's that had
cancers that grew despite the typical drugs such as a minimum of hormone
therapy and chemotherapy, but other's too, the patient's live longer.
And that led to the initial approval of what we call it overall survival benefit.
Dr Manish Shah (Host): So, the other analogy is like, almost like a Trojan
horse, So you're using the, binding of the antibody to the target in this
case, PSMA, And then delivering the lethal blow, which is the, in this
case lutetium or the, beta emitter.
but that actually brings up another point.
because I think this will come up in the next several years.
The difference between beta emitters and alpha emitters.
Dr Scott Tagawa: I would say that, their size is a different,
but the important thing is, the properties, and it's two, one is how.
Potent or powerful.
They are, we call that linear energy transfer or let, but that's really just
how powerful are they and when they land, how far away can they do damage.
So the beta emitters, the approved ones are, iodine First and Atrium 90
that I mentioned that can be delivered.
But in terms of the main.
Ones that we target for cancers that happen to be prostate cancer and mostly
GI neuroendocrine tumors is Lutetium 1 77, which is predominantly a beta emitter.
So relatively weak energy.
And when I say relative, This is relative to the alphas that I'm
gonna talk about, but can travel.
Millimeters to centimeters, meaning that not necessarily the particle, but the
effect can go through several cells.
So there's what we call a bystander effect.
So where it lands it could affect that cell, but also cells around it, which can
be good if the cells around it are cancer, even if they don't have the target there.
So a cell that has PSMA can.
Bring that in.
The neighboring cell that doesn't have PSMA can be affected so
that can be the good part, but also can affect normal organs.
And that could be some of the side effects.
the beta versus alpha, relatively the beta, relatively weaker energy, but can
travel through and alpha, depending which one is thousand to several thousand fold.
One particle.
One particle, more potent this energy amount, but typically can only travel.
Through a couple of cells, so not a millimeter, much less than that.
And that's on a high level, the, major differences between that.
As of today, there's one alpha that's approved.
It happens to be in prostate cancer.
It's called radium 2 23, which lands in bone.
Dr Manish Shah (Host): the current approval of, the PSMA directed
therapy is with the beta emitter, but there's research with alpha emitters
and, if I understand correctly, the idea is that you might be able to
deliver, very potent therapy more.
Fally, but, it may not be as broad, so, is it possible that an alpha
miter might be better for a smaller volume disease or something like that?
Dr Scott Tagawa: there's physical properties.
So we work with physicists, I guess, in all types of radiation.
We work with physicists.
and, they look at models and if you have one cell and you put in,
literally, you can inject, an alpha.
Or we can inject the beta.
The alpha has a good chance of killing the cell, the beta, because of two things.
Number one is it's the lower energy, but number two is the energy is actually
going pretty far outside the cell.
So for those two things, I would say yes, what we call micrometastatic disease.
Things that are just millimeter or less type things that we can't
see on scans, based upon those properties, less likely to be.
Cured with a beta emitter more likely to be cured with an alpha emitter,
assuming that we can target the cells.
Dr Manish Shah (Host): so from a drug development standpoint, it may
have implications because you might think of, adjuvant treatment, more
in the, realm of a alpha miter.
but, that's, in the weeds a little bit, I think, you know, just from a,
patient and a caregiver standpoint.
Understanding these differences, gives us a high level understanding.
But what about safety?
you're injecting essentially particles that have radioactivity.
Do, patient's need to worry about their loved ones if they're in the same house,
if they're using the same bathroom?
Like what about those implications?
Dr Scott Tagawa: So You asked should they worry.
I would never tell someone to worry or not, but there can be some risks that are
there that, as far as I know, have never translated to actually any real harm.
So the beta and alpha that we're talking about is the part that
we are interested in oncologists in terms of killing the cells.
However, even the long range betas like I 90.
They're shielding, it's inside the body.
It's not really gonna be harmful to other's.
There's something we call gamma and people have heard about gamma rays.
that's what we see on scans.
So to see in a scan, if, someone thinks about it, we do an injection
And then the scanner is inches the feet away so those can travel.
Um, so particles or radionuclides such as Lutetium 1 77 also have gamma.
We utilize that to be able see where it landed.
We can do scans, but that's the part that could cause harm
or damage to other people.
or other living things.
I know some people worry about their pets.
so yes.
In terms of radiation safety, this common dogma is time and distance.
So the closer someone is or something is, And the longer
it's close, the higher the risk.
there's two instructions that we'll give.
One has to do with.
The time and distance thing.
So depending on the dose and other things, we'd say loosely, especially
for the first couple of days, not within a foot for more than an hour,
that's kind of a loose type of a thing, giving someone a hug, no problem
even giving a baby a hug, no problem.
But not spending so much time, especially within the first
couple of days of treatment.
the time part is also not just how long someone is, but these all decay.
So the amount of radiation today versus tomorrow is different, and it depends
on what drug we're talking about.
But lutetium is a week, so half of it's gone in a week.
So we know that, several days out, there's a lot less that is there.
The other part is at least these small molecules, the way they leave
the body is through the urine.
And even though the urine will have much less radiation than what's actually in
the body, there's nothing shielding it.
There's no natural thing.
So we really worry about the urine that comes out, especially
the first couple of voids.
so that same-day.
We make sure that people have flush to toilet, et cetera, and if there's any
incontinence, we make sure that the, linens or the, diapers, whatever else are,
taken care of a little bit separately.
So that That is something that's a little bit different.
So all of our drugs that we have can be harmful to the patient and
other's if they happen to get exposed.
But This is something that can be passive exposure.
It's not someone taking their cancer pill by accident or on purpose.
It is just being near someone for a long time.
So, It is something that we, discuss, and, counsel with this type of therapy.
Dr Manish Shah (Host): that's so helpful.
And it makes so much sense, the way you explained it.
we've covered a lot of ground.
I wanted to make sure we got in.
the key things is that, both of us are in drug development.
You led a pivotal, phase three trial, and, it was presented at one of the
international meetings last year.
I just wanted to make sure that you had a chance to talk about that
and, how does that play a role with what we talked about today?
Dr Scott Tagawa: the first drug that was approved in terms of PSMA
happened to be this drug that we call Lutetium PSMA six one seven.
It's.
Branded as PTO was first, FDA, approved in patient's with metastatic or spread cancer
that was beyond all the normal therapy.
So at least beyond hormonal therapy and chemotherapy.
that was 2022.
And then another trial again in patient's that had, cancer or treatment resistance.
This one to only hormonal therapy called PSMA four.
so once someone had this disease, actually, I'll take 30 seconds to mention
this, what we now call A PMR or Amgen Pathway modulator resistant therapy.
We used to call this castration resistance.
But castration has a negative connotation and it is not patient friendly.
So we've eliminated that term from the jargon.
But anyway, in this hormone or A-A-A-P-M resistant patient population,
there's benefit and f FDA approval.
What we did, literally us, cause it started in the cooperative groups
And then it was taken over by a drug company, said, well, what about upfront?
And there's multiple scientific reasons why this should work.
It should pair well with hormone therapy.
Hormone therapy can make more psma, some more target.
Again, we call radios sensitized, so there's multiple scientific reasons for
this, but we simply ask the question, okay, we have the standard of care That
is these two hormonal drugs when someone walks into with metastatic disease, what
if we also add in this lutetium PSA.
At the very beginning, This is called the PSMA edition study, what we
call the primary endpoint, or the first main read out of how well this
worked called efficacy was called radiographic progression-free survival.
So basically, how long was it until cancer grew on scans or the patient died?
That combination and, and it turned out to be a positive study, presented,
in Germany, as you mentioned at esmo.
the early addition of Lutetium PMA 6 1 7 to initial therapy with
that hormone therapy doublet was better led to a longer time until
scans get worse or someone died.
If we added this Lutetium patient, basic seven early.
it was already standard to do later, And in fact in the trial, if a
patient entered and was assigned or randomized only the two drugs, when
the scans get worse, they were offered
Dr Manish Shah (Host): It's the same treatment.
it was the crossover.
so congratulations.
It's, no small feat to do that study.
And, it's an important point.
So, This is a theme that we've had in other episodes as well.
If you think of targeted therapy, we've mentioned this before, that,
if you have a target and you're able to attack that target, we've
learned through many different trials and many different cancers.
The earlier you hit the target, the more successful you're going to be.
and I'll just, 10 seconds.
Talk about BRAF, which is a very important target in colon cancer.
the first drugs that got approved were approved in the second line setting.
There was a modest benefit in survival when we, applied
it in the first-line setting.
Patient's lived much longer And the survival benefit was much more.
And in some respects, this, trial that Dr.
Tagawa led is exactly the same way the PSMA, lutetium targets.
PSMA, we have a target.
It is expressed on prostate cancer cells, and if you apply that early, so before
progression on the standard therapies, he showed that The rate of progression
on scans was much longer with the use of the lutetium, PSMA treatment.
So it is a common theme and I think it's an important thing, and I think it
maybe even addresses the way that drug development is going to go where instead
of developing these targeted therapies in.
At the metastatic setting, their application may be most before the cancer
has spread, where, in earlier stage or, in what we call neoadjuvant treatments.
What are your thoughts on that?
Dr Scott Tagawa: I totally agree.
there's some implications just one of the topics we talked about
before in terms of the betas.
In micrometastatic, so adjuvant or neoadjuvant.
So talking about drugs versus let's say the knife with surgery.
The knife is pretty good for everything that's within that part, but we wanna take
care of everything that's outside of that part or we call micrometastatic disease.
So some of these things can work really well.
Like most of our drugs can.
Even chemotherapy just poisons that preferentially harm the cancer cell.
they work and improve cure rates and most of the time.
the difference between cure versus just getting a few more years.
It's, a much different type endpoint.
So there is a caveat with these radionuclide that maybe some of them will
be suboptimal in that particular setting.
But in terms of earlier, yes, most effective therapies, rather than
measuring outcome in months, we're measuring the outcome in years
because they're just more effective.
generally speaking, I think just, the cancer cells are more sensitive
or less likely to be resistant when we move them in earlier.
Dr Manish Shah (Host): that's a, whole other topic.
So I think this has been terrific and I wanted to thank you very much, Dr.
Tagawa.
we covered a lot.
We covered.
what prostate cancer is, the dependence on the androgen pathway, the treatments
from, hormonal treatment, to, chemotherapy and radiation, different
types of radiation, the, Trojan Horse of Lutetium and PSMA versus PSA.
it's really quite amazing.
I'll, ask you one final question.
what's.
The most exciting thing about the future in terms of, treatment for
prostate cancer or other GU cancers?
this, podcast is gonna land, just around the time of gu, asco.
So I think it's gonna be well timed.
Dr Scott Tagawa: Well, to stick with a theme, is that we have number one
identified these targets, which are much more on cancer cells than the normal body.
And now with technology have paired those.
With therapeutics and or diagnostics that can target them.
And those could be targeted chemotherapy, we call them antibody conjugates.
And that has, made huge changes, really huge paradigm shifting
things where now we have actually gone to increase the cure rate.
Bladder cancer.
and we're working on some of those drugs in prostate cancer.
We can attach a radionuclide And that really change the, way we
diagnose and stage as well as treat patient's with prostate cancer.
and there's a new agents that are about to be FDA-approved in terms of
imaging with, kidney cancer as well.
So it's great that we have those essentially now, 20 26, 20 25,
and now we can leverage that.
Because we have identified additional targets that are there, And the
pathway, now that we know how to do it, should be much quicker to
develop these agents against, all these different types of tumors.
And not just in geo, but across the board, a more selective fashion.
Dr Manish Shah (Host): absolutely.
I think we've had, some podcasts on, the ADCs, the, antibody drug conjugates,
and, it's actually an exciting time.
I think that you're absolutely right.
we are identifying more targets.
We're identifying.
therapies that can target those, proteins or, targets biomarkers, and we're
learning how to use them in better ways.
I'd like to thank you very much for your time.
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That's it for CancerCast, conversations about new developments in medicine,
cancer care, and research.
I'm Dr.
Mind Shah.
Thanks for listening.
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