So, Dr. Scholz, recently we've had a new FDA approval in prostate cancer:
"Pluvicto," which is part of the lutetium-177 story. Can you talk about, like, what is Pluvicto?
When is it going to get approved? I mean we're really excited about this;
anything that we can have to fight advanced prostate cancer is very exciting.
It's an injectable anti-cancer medicine.
It's administered, I think, on an every six weeks protocol. it's an intravenous injection
and the beauty of it is that it's very targeted against prostate cancer. It uses
the same technology that these new PSMA PET scans used. The PSMA PET scans have a
monoclonal antibody that sticks only to prostate cancer, and they put a low energy radioactive
moiety on that molecule so that the radioactivity sticks to the prostate cancer throughout the body,
and then they put you in a scanner and they can see where the cancer is. Well,
intelligent people figured out well if you can put a low-energy radioactive moiety,
why not put a high-energy radioactive moiety and kill the cancer rather than
merely visualize it on a scan, and that's what Pluvicto is, and it works. We've had patients
that have traveled to other countries where it's already been approved for a couple years and it
is something for people who have really been through a lot, have metastatic disease,
who've become hormone-resistant, who have been exposed to Taxotere chemotherapy in the past,
and that isn't working. In the past we didn't have a whole lot of options for that,
you know, experimental trials and other things, but we've been very gratified to see
well over half of the patients that would travel to other countries and get this
new medicine would have notable responses: declines in PSA, disappearance of bone pain, and
thankfully, with relatively few side effects; the most common thing is the PSMA antibody,
which is on the surface of prostate cancer cells and salivary gland cells, does draw some of the
radiation into the salivary glands and some of the patients get a dry mouth from salivary
gland reduction of saliva. It hasn't been a super prominent problem, but it is noticeable in some
people and also, in theory, can cause a reduction in white cells because they're more sensitive to
radiation, which I haven't seen a whole lot of honestly, so it's been very well tolerated
and made a really big difference in people who'd run out of other options.
So, as far as the staging goes, you know,
you mentioned that people would have to have failed hormone therapy and had
some form of chemotherapy. Is that the only stage it's available in currently?
I'm not sure exactly how it's going to shake out because it'll come down to
what the insurance companies are willing to pay for, and I think since it was studied in that
type of patient population that it's likely that they'll want some previous exposure to chemo,
that the patients would be hormone-resistant, so we don't know yet. How soon are we going to be
able to start giving this with insurance coverage here in the United States?
I've been having some conversations with the company it looks like maybe in a month or two,
so I would hope by the summer time people will be able to have this medicine available and covered
by their insurance. You mentioned regarding the side effects of dry mouth, is that a permanent
side effect or would that just be a temporary side effect like while they're having treatment?
I think it could be permanent that, and i don't have enough experience; we've probably
only treated about maybe 20 patients with this medicine to know if it's something that does
slowly improve over time, but it certainly can linger after the treatment has been completed.
And as far as other treatments go, I mean, would patients stop the chemo in order
to take Pluvicto or would they continue chemo? How does that protocol usually go?
Well, the standard approach in oncology, typically, is that if you're stopping a medicine
because it's ineffective that you'll you will go off of that. The exceptions in the prostate world
are people that have stopped responding to Lupron. Typically, they're left on Lupron for life.
That same policy is not usually used for other medicines like Taxotere or Zytiga or Xtandi,
though, we sometimes will leave people on Xtandi and Zytiga. ust for the same principle that we
leave people on Lupron. We leave people on Lupron because we believe that there may be
certain subtypes of prostate cancer cells that are sleeping but not dying as a result of low
testosterone and allowing testosterone to come back, or giving them access to testosterone, may
stimulate some of the cancer cells to grow. So, our policy usually is to leave people on Lupron
if they've been progressing on Xtandi or Zytiga; we may leave them on that as well, but certainly
not Taxotere. Taxotere can cause a lowering of blood counts, and in theory, lutetium-177 can
cause a lowering of blood counts, so you wouldn't want to have an interaction in that regard.
As far as the imaging goes, do patients have to have, like, known spots on a PSMA scan? Like,
what if their PSA is rising, they've failed hormone therapy, they've failed chemo,
they're searching for the cancer, but there's, you know, we don't see it on the PSMA scan?
So, I think that will be a requirement is that patients will have had to have had a previous PSMA
pet scan that shows metastatic disease and the reason being is that about 10 percent of prostate
cancer patients don't have PSMA on their cancer cell surfaces and the lutetium-177, therefore,
is probably not going to work in those people because it won't stick to the cancer cell. So,
PSMA PET scans are becoming much more routine now, and I predict that in short
order, they're going to replace the traditional bone scans and cat scans,
but for this particular treatment, yes, they'll need to confirm that a potential patient isn't one
of the 10 percent that doesn't have PSMA, in which case we wouldn't expect this treatment to work.
Now, I know we're still finding out the guidelines for insurance coverage and all that,
but do you suspect that it would be covered in like oligometastatic or would they have to have,
like, more than five spots? Is it typical that they could just see one and get the treatment?
I don't know how that's going to shake out. There are clinical trials starting up; UCLA is
starting up a clinical trial for oligometastatic prostate cancer—just to refresh people's minds,
that is five or fewer metastatic sites oftentimes in people that have hormone-sensitive disease,
although they could be hormone-resistant—getting payment for it in that setting will probably
be difficult, but it is an interesting idea because it's becoming fairly mainstream now
that if people have two or three metastatic spots, that they are
referred to a radiation therapist for treatment to those spots. Historically, people always said
once it's out of the barn you, can treat three spots, but you're only just getting to the tip
of the iceberg; there are other smaller spots and don't bother to treat those three spots,
but that thinking has been altered because the scans have gotten much better and a
certain percentage of patients only have those three spots and they can get a huge benefit by
eradicating those three metastatic spots. The idea of adding Lutetium-177 to the whole process is
that if there are other smaller cancer spots that are flying under the radar that weren't picked up,
maybe this medicine will be effective in eradicating those tiny little spots. We
use that rationale and giving people chemotherapy, sometimes, when they have oligometastatic disease—
going after the small spots that we can't see on the scans. So, it's an investigational approach,
which I don't think anyone— we don't know the answer as to whether that will be beneficial,
but there is a study on going to try and answer that question.
So as far as access goes once this, you know, we see of whether insurance coverage or not
,you know, is it any place that can do a PSMA scan could possibly be doing the Pluvicto treatment as
well? Yeah, I think that's true we ran into the same questions when Xofigo got approved, which
is a injectable form of radium that can uh swim around in the body and find bone metastasis and
radiate them. It doesn't attack prostate cancer that would be in the lymph nodes along the liver,
but in the bones which is a common site, Xofigo is effective, and it was the first time that I would
be referring patients to facilities that do nuclear scans; they're not really clinicians, and
they were a little bit like fish out of water. These physicians you'd refer them a Xofigo
patient and you could tell they were in the back room looking through their their medical manuals
about prostate cancer and trying to understand, and sometimes not understanding that the clinical
responsibility still resides with the with the doctor ordering it—the medical oncologist or
the urologist—and we're just asking them to give the injection because we're not
licensed to give radioactive materials, and that may come up again also with lutetium that the—
is it going to be the radiation therapists that give it? They're experienced with treating
patients. The nuclear medicine doctors, who do scans but typically don't see patients?
It is a very safe and it's very logical that either of them could do that,
but I don't know how it's going to play out. If we key off what happened with Xofigo,
it may be the nuclear medicine doctors that are administering this.
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