# Precision Medicine vs Persuasion Medicine: Measuring vs Reading HER2

February 22, 2023## Information

Yale Cancer Center Grand Rounds | February 21, 2023

Presented by: Dr. David Rimm

ID9544

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- 00:00I'm, I'm iron crop.
- 00:02I'm the CTO director here and it's
- 00:06my pleasure to introduce David Rimm,
- 00:08who has many of you know is the Anthony Brady
- 00:11Professor of Pathology and medicine here.
- 00:14He is a Hopkins alum, did an MD PhD there,
- 00:18then came here for for pathology residency
- 00:21and then did a psychopath fellowship
- 00:24at the Medical College of Virginia.
- 00:27He's actually now been at
- 00:29Yale for almost 30 years.
- 00:31That's impressive.
- 00:32He's the director of the Pathology
- 00:35tissue service here and serves as
- 00:38director of Translational Pathology.
- 00:40You know, I think David has been
- 00:42at the forefront of.
- 00:44I guess I don't need to as in the
- 00:47forefront of quantitative pathology
- 00:49for for many years and he's well
- 00:53known throughout the the, the.
- 00:55The field for this he developed
- 00:57many novel assay techniques for
- 01:00identifying predictive markers to
- 01:02determine which tumors are sensitive
- 01:05to which targeted therapies.
- 01:07And this has become increasingly
- 01:09important as the number of targeted
- 01:11therapies has increased and our
- 01:12use of those drugs has increased.
- 01:14And today he's going to focus on the
- 01:16development of companion diagnostics
- 01:18for her two directed therapies.
- 01:20I think this is particularly timely as
- 01:23the first her two targeted therapy for non.
- 01:26Fish amplified breast cancers was
- 01:28just approved six months ago and how
- 01:31exactly we identify which patients
- 01:32are going to benefit from this therapy
- 01:35I think is a huge question and the
- 01:37one the field is struggling with and
- 01:39David's made a lot of inroads into that
- 01:41and I think he's going to focus on,
- 01:42on on that today.
- 01:44So thank you for bringing this
- 01:46timely discussion to us.
- 01:51OK, great. Thanks, Diane, and thanks to
- 01:54the leadership for inviting me today.
- 01:56But thanks especially for
- 01:57Ian for introducing me.
- 01:58He's a world leader in this space
- 01:59that I'm going to talk about.
- 02:00That is the her two.
- 02:0480C or antibody drug conjugate space.
- 02:07I'll start by my title is precision
- 02:09medicine versus persuasion medicine and
- 02:11I'll get to what persuasion medicine
- 02:13is a little bit more at the end.
- 02:15And reading versus measuring.
- 02:17And measuring is what you do quantitatively.
- 02:20Reading is what pathologists do
- 02:22when they look at slides and
- 02:24difference between subjective and
- 02:25objective assessment of tissue.
- 02:30Let's see. Let's start with my disclosures.
- 02:33As you can see, I do a fair bit of consulting
- 02:36and a lot of the research in my lab,
- 02:38including the work that led to this.
- 02:40Most of what I'm going to present
- 02:42today was sponsored by companies
- 02:43including Sephylon and Kanika Minolta.
- 02:47So today I want to spend the next 55
- 02:50minutes or so talking about first and
- 02:52quick introduction to the new drugs.
- 02:54If you've heard Ian speak,
- 02:55I don't need to give this part,
- 02:56but maybe you didn't a proposed new assay
- 02:59for these new drugs high sensitivity
- 03:01would call the assay high sensitivity
- 03:04or HS or two and then CAP CLIA,
- 03:06what take, what does it take to get
- 03:08something from your research lab so
- 03:10that into a lab where we can deliver
- 03:12information to patients and put the
- 03:14results in the patient's chart.
- 03:15That's what cap CLIA is taking the new.
- 03:18Say to the clinic and then finally I'll
- 03:20talk about precision medicine versus
- 03:21persuasion medicine and try to talk all
- 03:23of you who are oncologists in the room
- 03:25and to not using persuasion medicine
- 03:27and focusing on precision medicine.
- 03:31So this is the, the big drug that got
- 03:33the first standing ovation in 25 years
- 03:35as I understand at ASCO and it it's,
- 03:38it's the same old drug,
- 03:39it's trastuzumab underneath,
- 03:41but they've conjugated 8 topoisomerase
- 03:44inhibitor payloads to the trastuzumab that
- 03:47gives you especially some special tricks.
- 03:50First of all, it brings these highly
- 03:52toxic payloads right to the cell.
- 03:53So it doesn't have the toxicity that
- 03:56giving the drug and the dosages that
- 03:58it would be given cause would cause.
- 04:00All kinds of toxicity.
- 04:02But if you bring it right to the
- 04:03salad it causes less toxicity.
- 04:05Whereas if you, and not only that,
- 04:07when it gets uncoupled in the
- 04:09cell it can spill out of the cell
- 04:11and kill neighboring cells.
- 04:13The so the the sort of neighborhood effect
- 04:16or proximity effect of the therapy.
- 04:20It worked really well and that's
- 04:21why we've all heard about it that
- 04:23you can see very few patients were
- 04:26resistant but most patients had
- 04:27some response and there were eleven
- 04:29CR's in the early trials and in
- 04:32fact it worked at for all patients,
- 04:35but especially in patients that
- 04:36were not amplified for her too.
- 04:38So the initial trials were all in
- 04:40patients that had her two amplification,
- 04:42but then they started trials on
- 04:44patients with low her two IHC 2
- 04:46plus and HC1 plus and you can see
- 04:48the curves look pretty similar.
- 04:50And in fact in those low,
- 04:51low patients in the Destiny 4 trial,
- 04:54ultimately the survival curve
- 04:55looks like great, looks like this,
- 04:57which is really a great improvement
- 04:59in the survival curve for advanced
- 05:01breast cancer and changing median
- 05:02survival from 5 to 9 months.
- 05:04And that's I think what ultimately
- 05:07has led to the popularization of this
- 05:09drug and the success of the drug.
- 05:11And they said we concluded a
- 05:13randomized 2 group open label phase
- 05:15two trial with her too low.
- 05:17What does that mean?
- 05:18So that's what we'll examine the rest, but.
- 05:20Before we go there,
- 05:21what about her 20?
- 05:22What about if they don't express
- 05:24any her two at all and can we tell
- 05:26the difference between her 20 and
- 05:27her two low and in fact in her two
- 05:30zeros and this there is a trial
- 05:31going underway that's her two less
- 05:33than one but greater than zero.
- 05:35That's the Destiny 6 trial
- 05:37hasn't reported yet.
- 05:38But there's also the her 20 equal 0
- 05:40Daisy trial which was a small trial
- 05:42in France where there was clearly
- 05:44in these waterfall plots clearly
- 05:46patients that benefited from drug
- 05:48even though they had a hurt 2 = 0.
- 05:51So is this the why is it important
- 05:53to understand this and have good
- 05:55diagnostics for it because this
- 05:56drug is the tip of the iceberg.
- 05:58Here's a list of other drugs
- 05:59which there's no way you can read,
- 06:01but all of these drugs are,
- 06:02are all these are targets for
- 06:04ADC's in clinical trials.
- 06:06So I think ADC's may become very
- 06:08important for oncology in the next
- 06:10few years and equally important
- 06:12will be companion diagnostics that
- 06:13actually pick the right patients as
- 06:15opposed to giving the drug because
- 06:17unlike when we know the tiger it so
- 06:19well and we know how the drug works.
- 06:21It's really important to be able to
- 06:22pick the right target or to pick
- 06:24the right patients that express
- 06:25the right amount of target.
- 06:26So what do we do now?
- 06:27So this is the standard practice guidelines,
- 06:29ASCO CAP guidelines in 2018 and
- 06:32these guidelines are how we practice
- 06:35as pathologists in assessment
- 06:37of her two expression.
- 06:38And this is the algorithm for what
- 06:41we look at when we look at the slide
- 06:43circumferential staining that is complete,
- 06:45intense and greater than 10% of the cells.
- 06:48That makes the three plus
- 06:49and then we have a 2 + 1 +.
- 06:50I won't go through them all,
- 06:52but they're kind of summarized
- 06:53here where one no staining,
- 06:55no membrane staining observed is a 0 +
- 06:571 is faint partial membrane staining
- 07:00and weak to moderate staining is +2.
- 07:02That's kind of subjective. In fact.
- 07:05How well can we do that and
- 07:07how important is it?
- 07:07Well.
- 07:08It used to be important to tell
- 07:10the heart threes the the three
- 07:12pluses from the others and the
- 07:14two pluses were they the reflex.
- 07:16But now it's important to have this CAD.
- 07:18The new category is far too low.
- 07:20And how many are there?
- 07:21There's a lot,
- 07:22maybe as many as 65 or 70% of the
- 07:25patients are thought to fall into this low,
- 07:27her two low category which means
- 07:28a lot of patients could get drug,
- 07:30but it also means that we need to be
- 07:32as accurate as we can and assigning
- 07:34those patients because we don't want
- 07:36the her two zeros to get the drug
- 07:38if they aren't going to benefit.
- 07:39Well, maybe we do.
- 07:40We'll talk about that later.
- 07:41But so how do we know how,
- 07:43how well do we do at this?
- 07:44Her too.
- 07:45So I'm fortunate to be on the
- 07:47immunohistochemistry committee of
- 07:48the College of American Pathologists.
- 07:50And so I get access to the
- 07:52surveys that make Clea labs,
- 07:54what CLIA labs are.
- 07:55That is,
- 07:55for a CLIA lab or clinical lab
- 07:57to return data to the chart,
- 07:58they have to do a survey twice a
- 08:00year to show that they're competent
- 08:02and effective at doing the assay.
- 08:04And here's the surveys for anatomic
- 08:06pathology for her two using a tissue
- 08:09microarray. This is her to a 2020.
- 08:11So it was the fall survey or the
- 08:13spring survey from 2020 from the
- 08:15College of American Pilot Pathologists.
- 08:17And you can see my colleagues here,
- 08:18including myself, who are on this committee.
- 08:20And when we looked at these surveys,
- 08:22we noticed that four, six and seven,
- 08:24that is 3 out of 10 did not reach consensus.
- 08:27That means that of the 1400 labs
- 08:29in the in the world that did this,
- 08:32they couldn't come to an agreement.
- 08:34That is,
- 08:34you need to have 90%
- 08:36consensus to have agreement.
- 08:37In fact, if we look at this one,
- 08:39it's interesting.
- 08:39This is one of the cases that didn't
- 08:42come to agreement and that was
- 08:44because there was a big discordance
- 08:45in the number of called 0 versus
- 08:471 and there were a fair number
- 08:49that even called it two or three.
- 08:50So that's troublesome.
- 08:51If we're testing these labs twice a year
- 08:54and we're assuring that they're giving
- 08:56the right answer for the patients,
- 08:58how can you have that much difference
- 09:00between zero and one that it's almost 5050.
- 09:03So since I I'm on the CAP committee,
- 09:05I could ask for the data from
- 09:07the last few years.
- 09:08And here's the data from
- 09:09the lab from 2019 and 2020.
- 09:12And of the 80 cases,
- 09:14fifteen of those cases showed a
- 09:16discordance of greater than 25%.
- 09:17And that's shown in these pie
- 09:19charts here where the zeros are
- 09:21blue and the ones are red and
- 09:23anything higher than one is black.
- 09:25Two and three,
- 09:26since we're not going to focus on that.
- 09:27So we we did,
- 09:28we thought is this really, you know,
- 09:30this is concerning,
- 09:31but you know what this is tissue microarrays.
- 09:33This is not what happens in the real world.
- 09:35So then we did a study of real
- 09:37world core biopsies.
- 09:38And enrolled 18 pathologists from 15
- 09:40institutions around the United States
- 09:42and ask them to read actual core
- 09:44biopsies that have been read at Yale.
- 09:46We collected 170 cases from Yale
- 09:48and had them score them according to
- 09:51the ASCO CAP guidelines before the
- 09:54publication and the popularization
- 09:55of her two one plus versus 0.
- 09:58So they didn't know they were just
- 10:00doing the ASCO CAP guidelines as
- 10:01they always have, and scoring 0123.
- 10:04And what they did,
- 10:05what they're scoring looked like was this.
- 10:07That is, the Blues were the zeros.
- 10:08This is the percent of pathologists.
- 10:10That scored at 0,
- 10:12so a fair number agreed that
- 10:14that there were zeros.
- 10:15There were 92 cases that were discordant,
- 10:18and of those,
- 10:209269 were discordant between zero and one,
- 10:23and only twenty were discordant
- 10:25between 2:00 and 3:00.
- 10:26So this actually was.
- 10:28Through many reviewers,
- 10:30ultimately got us published in JAMA Oncology.
- 10:34How come it's not advancing now?
- 10:38Oh, hold on. I lost my laser pointer.
- 10:44Microsoft doesn't want me to do this now.
- 10:45It's the screen has turned
- 10:47Gray as it's saying restart.
- 10:49I probably shouldn't.
- 10:50I should probably wait for
- 10:51the program to respond.
- 10:53Very sorry about this,
- 10:54but suffice it to say that I'll skip
- 10:57the next slide so we can keep going.
- 10:59The next slide was after
- 11:00many review rounds of review,
- 11:02we did get this published in JAMA Oncology,
- 11:04but weren't allowed to say
- 11:05what we wanted to say,
- 11:06which is that there's really a
- 11:08great discordance between zero and
- 11:09one and not so much discordance
- 11:11between 2:00 and 3:00.
- 11:12And I don't know if we have
- 11:13should I restart the program?
- 11:14I don't know if we have any IT
- 11:16people here that or how long we're,
- 11:17you know,
- 11:18we'll be here for the next 45 minutes
- 11:20waiting for the computer to come along.
- 11:25Wait to respond or restart the program.
- 11:28Maybe I should restart the program and
- 11:29that will take several minutes too.
- 11:31It's just it's just not rebooting
- 11:33the computer, it's just. Yeah.
- 11:37Let's try again. Yeah, we're good.
- 11:41We're good. Sorry about that. OK.
- 11:43We saw all those things already.
- 11:45Let's go to. The study that was in
- 11:49JAMA Oncology was here and this is
- 11:52what was the this is the figure and
- 11:54and Eileen Fernandez was the lead
- 11:56on this study in my lab and she.
- 11:59Did the analysis that is shown here
- 12:00that shows that there's a lot more
- 12:02discordance between zero and one
- 12:04than there is between 2:00 and 3:00.
- 12:06And for two we have a solution.
- 12:08For two we can do fish,
- 12:09so we have a orthogonal assay.
- 12:11What do we do between zero and one?
- 12:12Well, we don't have a solution yet.
- 12:14That's what I'll show you in a minute.
- 12:16But also you can look at this analysis
- 12:19which which shows you this is a work
- 12:21done by Jack Robbins in the lab with
- 12:24Eileen Fernandez showing the percentage
- 12:26of people that called 0 versus called one.
- 12:29And so if your pathologist #18 and
- 12:31these are all currently signing out
- 12:33pathologists most with more than five
- 12:35years of experience around the country.
- 12:37So these are not residents or not to say
- 12:39that residents can't do this just as well.
- 12:42But these are not residents
- 12:43or or or laboratorians.
- 12:45These are sign up with ologists.
- 12:47And if you're pathologist 18 you only
- 12:49score 15% of the patients with a 0,
- 12:52but if your pathologist number one,
- 12:53you have 44%.
- 12:54So whether or not you get trustors,
- 12:57mab drugs,
- 12:57tecan depends on who your pathologist is.
- 12:59That doesn't sound like a great idea to me.
- 13:02So what we asked is how many people
- 13:04do you need to make sure that
- 13:06an assay agrees with each other?
- 13:08And we, we invented this with gang hand.
- 13:10We invented this system to realize that
- 13:13there's 21,000 pathologists just in the
- 13:14US and at that and 100,000 in the world.
- 13:17So how many do we need to decide
- 13:19whether or not an essay is good?
- 13:20And so we there, there is actually
- 13:23no statistical method for this.
- 13:24So we simply decided to plot
- 13:26the overall percent agreement.
- 13:28That's what overall LPA stands for
- 13:30versus the observers or readers.
- 13:32And what you see is that the more
- 13:35observers you have,
- 13:36the less agreement you have,
- 13:37which makes sense.
- 13:38The more people you ask,
- 13:39the more discordance you're
- 13:40going to get in your answers,
- 13:41just mathematical truism.
- 13:42And so does this actually work and
- 13:45can this be used to assess assays?
- 13:47So here's estrogen receptor.
- 13:48Turns out we're really good
- 13:50at estrogen receptor.
- 13:51If you have a quartet of
- 13:54pathologists read estrogen receptor,
- 13:56all four of them will agree somewhere
- 13:58between 85 and 95% of the time.
- 14:01How do we do for her?
- 14:02Too well, not so well.
- 14:05This is the plot for her.
- 14:062/3 plus or not three plus.
- 14:08We're really good at that.
- 14:09But if you have a quartet of pathologists
- 14:124 decide whether it's zero or not zero,
- 14:15it's between 40 and 80 percent,
- 14:1885%. So this is a new method
- 14:20to approach the analysis,
- 14:21to try to figure out how many we
- 14:23need and how many do we need to make
- 14:24a new assay to make a good study.
- 14:26Well, it's when it plateaus,
- 14:27so in this case we probably need 9 or 10.
- 14:30And this case, no number is sufficient
- 14:31because it goes all the way down to the
- 14:34baseline to tell ones from, not once.
- 14:36So the point is, I think that.
- 14:38I've I hope that I've convinced
- 14:40you that we need a new assay.
- 14:43And so that's what we have done,
- 14:44is propose a new assay that's measured,
- 14:47not red. And so based on that.
- 14:50We start, we started from the beginning
- 14:52with cell lines and these cell lines
- 14:54are all cell lines that are amplified,
- 14:56gene amplified and these cell
- 14:58lines are all gene express.
- 15:00Her too,
- 15:01but are not gene amplified and
- 15:03you can see when you plot them.
- 15:05If you look with the current FDA
- 15:07approved assay you can separate the
- 15:09highs from the lows or the negatives,
- 15:11but you can't stratify the negatives.
- 15:14Whereas if you do the new assay
- 15:15high cut 10 times more antibody,
- 15:17pretty simple new assay.
- 15:18You can then stratify the low cell
- 15:20lines and tell the zeros from the ones.
- 15:23Essentially if you were reading the
- 15:25cell lines but it was the wrong,
- 15:27the wrong the current assay is
- 15:29the wrong tool for the job.
- 15:31Or as was said by a group in France.
- 15:36The current assay now FDA approved,
- 15:38is like weighing mice on a
- 15:40scale for elephants.
- 15:41And I think this is really good
- 15:43because everybody gets this if
- 15:44you have a skill for elephants,
- 15:45it doesn't work for weighing mice
- 15:48and it's all about dynamic range.
- 15:50So here's the assay we did we
- 15:52invented and and this is to have
- 15:54a a series of cell lines and then
- 15:56just do like a Bradford assay like
- 15:58we all did in college chemistry
- 16:00for where we make a standard curve.
- 16:02And we used our tissue microarray to
- 16:04make cell lines and with the help of
- 16:06array science made a standard curve.
- 16:08And then with the help of Crotia we
- 16:10figured out how many animals per
- 16:12microgram there were in each of these
- 16:14cell lines and then converted that
- 16:16using Q path to how many animals
- 16:18per square millimeter there are.
- 16:19So now we have an assay.
- 16:21That can tell us animals per
- 16:22square millimeter.
- 16:23And like all assays,
- 16:24it saturates when it gets too high.
- 16:26So the amplified cases are
- 16:28saturated and we can't use those.
- 16:30But since we don't really care
- 16:31about 2 plus and three plus,
- 16:32we got that pathologists can do just fine
- 16:34in telling 3 plus from not three plus.
- 16:36We need an assay to tell 0 from 1.
- 16:39And so that's this assay works fine.
- 16:40If we get rid of these two,
- 16:42we can now build a very nice
- 16:43standard curve that we can use
- 16:45as a linear assay and then assign
- 16:47each case and animals per square millimeter.
- 16:49And so just to remind you.
- 16:51I'm going to talk a little bit
- 16:52about limits of detection,
- 16:53limits of quantification,
- 16:54and limits on linearity.
- 16:55A little bit of essay terminology and we
- 16:57and this is the range we want to be in,
- 17:00not this range,
- 17:00which is what the saturation range,
- 17:02which is what the current
- 17:04essay really focuses on.
- 17:06Because really the current
- 17:07assay all you need to tell is.
- 17:09Is it saturated or not?
- 17:11For the new assay we need
- 17:12to tell how much they have.
- 17:14So here's our the current our standard curve.
- 17:17With the higher two assay and
- 17:19you can see there's two positives
- 17:20and the rest are negative.
- 17:22So it works if you just want to
- 17:24tell amplified from non amplified,
- 17:26but what if you want to tell that
- 17:27low range so you can see that you
- 17:29can see the full dynamic range with
- 17:31the new her two low assay antibody
- 17:32concentration or that what we're
- 17:34calling high sensitivity HSV or
- 17:36two you can see in that range.
- 17:38So now we have to talk about a
- 17:39little bit of wonky stuff and
- 17:41that is what are those things.
- 17:42So what is the limit of detection,
- 17:44what is the limit of quantification
- 17:45or what is the limit of linearity.
- 17:47So these are the definitions
- 17:48and this is right.
- 17:49One of the FDA's handbook on how they
- 17:51advise industry to do this and you
- 17:53can see that the limit of detection
- 17:55is the lowest concentration of the
- 17:57analyte that can be detected but
- 17:59not but and reliably to strings
- 18:01from zero but not necessarily
- 18:03quantified that is too low.
- 18:05So what we really want is to know
- 18:07the limit of quantification because
- 18:08then we can do it right every time.
- 18:10But we don't yet know how much
- 18:12her two is required to benefit
- 18:14from trust who's mab drug stcan.
- 18:16So we're going to measure all the
- 18:18way down to beyond the limits of.
- 18:20Our essay to to the LD and below and
- 18:22see what we get and what we got is this.
- 18:25When we did it on tissue microarray we
- 18:27could see that the the zeros are blue,
- 18:30the Reds are one, ones are red, the twos.
- 18:32This is the pathologist read over here
- 18:342 Plus is black and three plus is green,
- 18:36and most of the Greens are
- 18:37above our limit of linearity.
- 18:39But look at how many twos and ones
- 18:41there are in this middle range.
- 18:43That would be called one.
- 18:44And I think this is even further evidence
- 18:46that we need a a quantitative assay.
- 18:48We need a measured assay,
- 18:49not a red.
- 18:50Say,
- 18:50in order to pick the right
- 18:51patients for trastuzumab drugs,
- 18:53tican and surprisingly there are some
- 18:55patients most of whom were called 0,
- 18:57but some were called one or two
- 18:59that are actually below our limit
- 19:01of quantification or even below our
- 19:02limit of detection as I'll show later.
- 19:04So then we did what you have to do in
- 19:06a clear lab is did 40,
- 19:08you have to do 20 positives and 20 negatives
- 19:10according to Fitzgibbons at all in order
- 19:12to bring your assay to the CLIA lab.
- 19:14But we don't have positives and negatives.
- 19:16We have a continuous scale.
- 19:17So we did 40 of them and these
- 19:19are actual core biopsies.
- 19:20Now they're not tissue microarrays,
- 19:22but you can see the same thing.
- 19:23There's a fair bit of Miss Assignment
- 19:25and in fact summarized here,
- 19:27you can see that there's zeros and ones,
- 19:30but there's a broad range of animals per
- 19:32square millimeter for zeros and ones.
- 19:34And the two plus not amplified almost
- 19:37in fact does overlap with the two
- 19:40plus amplifies and the three pluses,
- 19:42which we're good at and we're pretty tight.
- 19:45So how many are there?
- 19:46Well, in our first forty there
- 19:48was about 20% of the cases that
- 19:50appear to be below the limit of
- 19:52quantification for her two protein,
- 19:54but potentially present and as
- 19:57target for a target for TDXD.
- 20:01So just to summarize to this point,
- 20:03about 70% of the cases have low her two
- 20:06defined as above the LQ and below the
- 20:09levels associated with gene amplification.
- 20:11About 8 to 10% are below
- 20:13our LQ or even our LD.
- 20:15It's probably about 6% below our LD.
- 20:18Many of the cases that
- 20:19are called her to zero,
- 20:20as many as 60% are in our studies,
- 20:21maybe 75% have detectable amounts
- 20:23of her too between 3 and 20 animals
- 20:26and the quantitative her two asset
- 20:29could be envisioned as a reflex tax.
- 20:31So that if you pathologist reads
- 20:33an IHC equals zero,
- 20:35they could then reflex to the
- 20:36quantitative test and the same way we
- 20:39reflex to fish today for A2 plus HC.
- 20:43OK, so that's the proposed new assay.
- 20:45Now let's take it to the clinic.
- 20:47So what's involved in the next
- 20:48step of taking to the clinic?
- 20:50And I like to quote a colleague
- 20:51of mine from Brigham and Women's
- 20:53who said once you have the essay
- 20:55working in your research lab,
- 20:56you're 5% of the way there.
- 20:58And I think that's really true.
- 20:59Now having brought this assay
- 21:01with hats off to Trish Gal who's
- 21:03not here and has not left,
- 21:05Nay Chan who was in the audience and Reva
- 21:08come ova who have helped me to bring
- 21:10this assay to the clinical setting.
- 21:12So the things that you have
- 21:14to do are antibody titration,
- 21:15maximization of signal to
- 21:17noise analytic validation.
- 21:18I'll try to go through this stuff fast
- 21:19because it's a little on the wonky side,
- 21:21performance accuracy, precision,
- 21:23sensitivity and specificity and
- 21:25serial core reproducibility.
- 21:26And then how do we tell our colleagues?
- 21:28What do we tell the oncologists?
- 21:29And then so the reporting is
- 21:31part of this as well.
- 21:32So first of all,
- 21:33we looked at the signal to noise
- 21:34and you can see that the peak
- 21:36signal to noise is at 1 microgram
- 21:37per mil for a new antibody.
- 21:38This is a new higher
- 21:40sensitivity antibody for her
- 21:41too than the one that's
- 21:43currently used in the clinic.
- 21:45And we took and we picked the
- 21:46concentration with the maximal signal
- 21:47to noise and then we looked at the
- 21:49accuracy and our accuracy isn't great,
- 21:51it's only 87%. Why is that?
- 21:54That's because we're more sensitive than
- 21:56the status quo assay which we had to
- 21:59compare it to which was HC012 and three.
- 22:02But overall we have quite a quite
- 22:05good concordance especially in the end
- 22:07and more resolution in the low range.
- 22:09And then our intra and intra
- 22:11assay precision is quite high,
- 22:1310% sounds like it might not be great.
- 22:15To interact assay precision and actually
- 22:17the essay that we just bridged to,
- 22:19we're now under 10%,
- 22:20but it's acceptable and the
- 22:22intra assay precision,
- 22:24this means to calculate the precision
- 22:26three slides run on separate
- 22:27trays at the same machine is,
- 22:29is, is about 5%.
- 22:30So these are where we want to be.
- 22:33Our sensitivity compared to the historical
- 22:35essay as 100% and our specificity is 84%.
- 22:39Why is our specificity low?
- 22:40Because we're more sensitive and
- 22:42so we call cases positive that
- 22:45we're called negative by IHC.
- 22:47So here's the proposed clinical
- 22:49future work workflow and this is
- 22:51what we're doing now which is we
- 22:53have we get the labs come to this
- 22:55lab that I've called the qutab lab
- 22:57quantitative diagnostics and anatomic
- 22:58pathology which is a new lab which
- 23:00is now open and open for business.
- 23:02And we've now begun to do this.
- 23:04This is and this is qdap essay #1,
- 23:07the high sensitivity here.
- 23:08Two,
- 23:08we batched the stains and do them
- 23:10in our like a bond stainer so that
- 23:12they're done in an auto stainer
- 23:13and then we read them originally
- 23:15in some old like legacy hardware.
- 23:17But now we're using this,
- 23:18we just recently completed the bridge study,
- 23:21although our license holder
- 23:22hasn't signed off yet,
- 23:23he will see it shortly and uses a
- 23:26much more high throughput device.
- 23:28Instead of an hour this machine would
- 23:29take about four minutes to scan a slide.
- 23:32So we wanted to update our technology
- 23:34a little bit and then we signed
- 23:35it out and Co path as a procedure.
- 23:37And so it ultimately makes it to
- 23:39epic and and clinicians can see it,
- 23:41this is what it looks like.
- 23:43The pathologist has to pick a region.
- 23:44So we're actually not measuring
- 23:46the entire core biopsy.
- 23:47We're measuring a region that is
- 23:49quote UN quote representative and
- 23:51that representative region is
- 23:52then looks like this.
- 23:53This is actually not a brown stain
- 23:55but a pseudo IHC which it shows the
- 23:57pathologist what they what it looked
- 23:59like and then the pathologist actually
- 24:01sees the number of fields of view,
- 24:03in this case 23 and the in this case
- 24:06the rare sight score in this case was
- 24:0915.4 animals per square millimeter.
- 24:11So that will be included in the report.
- 24:13We'd say 15.4 animals require millimeter.
- 24:15We don't know what that means.
- 24:17I mean,
- 24:18we do know that it's detectable
- 24:19and then
- 24:20we can give a choice in our interpretation
- 24:22that it's positive for expression high.
- 24:24That is, it's above our limit of linearity
- 24:26positive expression intermediate,
- 24:28which means that it's like a one
- 24:30or A2 positive for expression low,
- 24:32which means it's.
- 24:33Present, but it might not be reproducible.
- 24:37That is, it's above our LOD but
- 24:39not necessarily above our LOQ
- 24:41and then negative below the LOD.
- 24:43And so these are the reports that we'll
- 24:45issue as as we start to receive specimens.
- 24:48So far we've received a grand total of two.
- 24:51We hope that after this talk and maybe
- 24:54in the future and certainly in the more
- 24:57distant future when we know how much.
- 24:59Is necessary for patients to respond.
- 25:02We hope that this essay will
- 25:03gain some traction.
- 25:04So our vision we currently offer HSR 2 in
- 25:07the QDAP lab test must be requested by an
- 25:10oncologist and the patients are billed.
- 25:11If the test is requested by an oncologist,
- 25:14there are I CD9 codes for all
- 25:16the stuff we're doing.
- 25:18We began a prospective study on all
- 25:20breast biopsies so that we have data of
- 25:23a year's worth of prospective data and
- 25:26we're about seven months into it now.
- 25:28We offer the essay coalitions
- 25:30from to Yale or elsewhere who want
- 25:33quantitative information,
- 25:34but only two so far to date.
- 25:36And then the discussions of the
- 25:38license we will.
- 25:38What we hope to happen is ultimately
- 25:40it won't just be yell that can do this,
- 25:42but we'll license it to some of
- 25:43the big lab companies that provide
- 25:45them the bulk of the service.
- 25:47It's interesting to know and
- 25:48interesting to me anyway,
- 25:49that only 15% of lab tests in the
- 25:52US are provided by academic labs.
- 25:54The other 85% are provided by private labs.
- 25:58And so clearly if we want to.
- 25:59Have this effect patients around
- 26:02the world and be useful and needs
- 26:05to make it into private labs and
- 26:07those discussions are beginning.
- 26:09So the last thing I want to talk about is
- 26:12the precision versus persuasion medicine.
- 26:15And so our original envision for
- 26:17this essay was that we would need
- 26:20to adjudicate the IHC's equal 0.
- 26:21And what we would do is we would get
- 26:24all the HC equals zero and we would
- 26:26measure them and then we tell you if
- 26:28you're above the limit of detection
- 26:30or above the limit of response.
- 26:31We don't know the limit of response yet.
- 26:33Someday we will and I'll show you
- 26:35how we intend to get there.
- 26:36But right now we don't know the
- 26:38limit of response but.
- 26:38You would take all the cases that
- 26:40were called HC0 and maybe the cases
- 26:42that were called HC One and do that.
- 26:45But something happened in the last
- 26:46three or four months and I haven't
- 26:48been able to document it yet,
- 26:50probably because it's not mature enough,
- 26:52but suddenly the IHC equals zero is rare.
- 26:55And that's because pathologists
- 26:57are people too.
- 26:58Pathologists sometimes might be
- 27:00a little more lenient on what
- 27:02they call IHC one and this code
- 27:04called Sympathy vote because
- 27:05then they can get this new drug.
- 27:07Here are real quotes that I've heard.
- 27:09I won't quote the people because to
- 27:12not embarrass them or give them credit,
- 27:14but here's a real quote.
- 27:16Hi doctor pathologist.
- 27:16So I see you called Missus
- 27:18X's biopsy IHC zero.
- 27:19That means I'm going to have
- 27:21to offer her brain radiation.
- 27:22Are you sure it's not H sequels one?
- 27:24Then I could give her her and her two.
- 27:28Should I go look at that slide again?
- 27:30Does that mean that my first view
- 27:32of that slide was not accurate?
- 27:34Or was it accurate and maybe
- 27:36I should change my diagnosis?
- 27:39Because I'm persuaded that
- 27:41that's better for the patient.
- 27:43I'm not sure that's a great idea from
- 27:45West Coast director of pathology service.
- 27:47Yeah, we don't have many
- 27:48IHC's equal 0 anymore.
- 27:50And from a Midwestern oncologist,
- 27:52I'm not seeing the response rates
- 27:53and in her two patients that
- 27:55they saw in the clinical trial.
- 27:56They're getting a lot of IHC zeros and
- 27:59maybe IHC zeros really don't respond.
- 28:01We know that eight to 10% of the
- 28:04cases really don't express any target
- 28:06and this is a targeted therapy.
- 28:08I mean we don't definitively
- 28:09know how the drug works,
- 28:10but we think it's a targeted therapy.
- 28:13After all,
- 28:14it's trastuzumab conjugated to toxins.
- 28:16So what's happened is that really
- 28:18now we need to adjudicate the one
- 28:21pluses what we really need because
- 28:23the zeros have minimized, not,
- 28:25I don't want to say they've gone away.
- 28:27If you ask pathologists,
- 28:28they will sternly tell you yes,
- 28:30of course we still call IHC 0.
- 28:32But.
- 28:34Data will set will will tell us
- 28:36in a year or so from now how
- 28:38our IC0 calls changed.
- 28:40But but I see one is now more common
- 28:42and so if it's if it's more common
- 28:44maybe that's the one we should be
- 28:46measuring and in fact that's the plan.
- 28:48So there are a few different ways
- 28:51we're going to study IHC equals one.
- 28:53The first is the Qdap Labs
- 28:56prospective study and this is
- 28:58copied with me by name by Nate Chan,
- 29:01who's the director of the Q dot lab.
- 29:03And you can see we began August
- 29:051 and we'll go till July 2023
- 29:07and today we have 226.
- 29:09I anticipate we'll get around 400.
- 29:12The inclusion criteria will be any
- 29:13case and the primary objective will
- 29:15be to determine the number of H0 cases
- 29:18that have detectable her two expression.
- 29:20So how many IHC zeros?
- 29:21And this study was designed
- 29:23before everything.
- 29:23Name HC One,
- 29:24but how many HC Zeros have above
- 29:26the limit of detection and how many
- 29:28HC ones have below the limit of
- 29:31detection will be interesting as well.
- 29:33That's a secondary,
- 29:34that's a secondary objective of the
- 29:36study and the study is in process
- 29:38and we all just to show you a peak,
- 29:41we've already started doing some
- 29:42quantitative work and in fact
- 29:44you can see from quantitative,
- 29:45this is quantification of prospective
- 29:48tissue from the clinical trial
- 29:50and you can see the lol in this
- 29:53case was 33 and the OD is 3.
- 29:55This is all done on the new platform
- 29:57and you can see that there's a lot
- 29:59of cases that are called zeros that
- 30:01are above our limit of detection.
- 30:02There's not as many.
- 30:03So far it looks like we're going
- 30:05to not have very many that are
- 30:06below our limit of detection,
- 30:08but time will tell as we get
- 30:10as the study
- 30:10matures. There's two other studies
- 30:13that were progressing on one is a
- 30:16TB CRC study report proposal with
- 30:18Ian and Eric's arrival at Yale,
- 30:20we became part of the Translational
- 30:23Breast Cancer Research Consortium,
- 30:24which is a group of 16 or 17.
- 30:26Now institutions that do studies
- 30:29together on translational research
- 30:30and the goal of this study that
- 30:33is still in proposal stage is to
- 30:35evaluate her two measurement in
- 30:36the one plus metastatic cases.
- 30:38So if we get one pluses and we get 2 or
- 30:41300 from 17 institutions around the country,
- 30:44we should be able to tell how
- 30:46frequently we see the patients
- 30:48that have one plus actually don't
- 30:50have any target and vice versa,
- 30:52we should be able to see response
- 30:54since all those patients since they
- 30:55were called one plus will be get.
- 30:57Drug will be getting trustors map drugs
- 30:58he can and be present in the residency.
- 31:00So here's the study a draft of the
- 31:03study objectives to evaluate the
- 31:04real world relationship between
- 31:06quantitative her two expression QIF
- 31:08and objective response in patients
- 31:10with her two IHC plus one and
- 31:13metastatic breast cancer receiving TXT.
- 31:15And then there's a number of secondary
- 31:17objectives that are shown here as well.
- 31:19And then a second study that I,
- 31:21I don't even have a slide for yet
- 31:24is that we proposed a study led by
- 31:26Merriam Lustberg here of patients
- 31:29who get HC0 and then prospectively
- 31:31giving them TXD much the way the
- 31:35Daisy trial worked on that study
- 31:38is not yet completely designed
- 31:40and not yet completely approved.
- 31:42So I don't have any slides to discuss it,
- 31:44but I think those are the kinds of studies
- 31:46we need where we have patient response.
- 31:48Either real-world patient response or
- 31:50clinical trial patient response in order
- 31:52to figure out the animals per square
- 31:54millimeter above which patients benefit.
- 31:56Will it be a cut point?
- 31:57Probably not.
- 31:58Probably there will be patients with
- 32:00high animals per square millimeter
- 32:02that still don't benefit because there
- 32:03are other mechanisms of resistance.
- 32:05And I have and one of the interesting
- 32:07topics that many labs are working
- 32:09on including my own are what are
- 32:11the mechanisms of resistance beyond
- 32:12just not enough her to present.
- 32:14And hopefully next year or a couple
- 32:16years from now I'll come back to you at
- 32:18grand Rounds and talk about mechanisms
- 32:20of resistance and a more complex assay
- 32:22that also doesn't just assay her too,
- 32:25but maybe assays other biomarkers
- 32:27that are associated with resistance.
- 32:29Or other drugs.
- 32:30And in fact the her two trope
- 32:312 assay as well along its way.
- 32:33So we can help clinicians decide
- 32:36between Saskatoon Vova Tican,
- 32:37which is a trope 2 targeting therapy
- 32:41versus trastuzumab Drexel can.
- 32:43So for that my my last slide,
- 32:45overall HSR 2 assay is an LDT,
- 32:47a lab developed test and not FDA approved.
- 32:50So if you only do FDA approved tests,
- 32:52you probably don't do them here
- 32:53since most of our assays are LDT's,
- 32:55but we do have a few FDA approved assays
- 32:59and many FDA approved assays.
- 33:01People don't realize this,
- 33:02but being on the CAP
- 33:03committees you realize this,
- 33:04if you change one step of the
- 33:06protocol of your FDA approved assay,
- 33:08it is then an LDT and you must thus
- 33:11validate it and so most assays.
- 33:13We do are not FDA approved.
- 33:15We might use FDA approved reagents,
- 33:17but most assays we do are actually LDT's in
- 33:19our lab and in all the labs around the world.
- 33:22And that also applies for molecular assays,
- 33:26gene mutation assays.
- 33:27Many of those assays are also not
- 33:29FDA approved assays but rather LDT's.
- 33:32HSR 2 essay is in the correct dynamic range.
- 33:35That is, we're not weighing elephants on or
- 33:37weighing mice on a scale built for elephants.
- 33:39The level of target required for trustees,
- 33:41mab drugs decan is still unknown and
- 33:43I speak here before you and I don't
- 33:45want to try to hide that from you.
- 33:46I think it's very clear that we don't
- 33:48know the answer to this question yet.
- 33:50But if we waited until we knew the answer to
- 33:52the question before we started the essay,
- 33:54we would be years behind as as this essay.
- 33:56We've been working on this essay
- 33:58for a couple years now to get it
- 34:00to the point that it's at.
- 34:01And so now that we have.
- 34:03Tools, I am asked that oncologists in
- 34:05the audience ask for measurements,
- 34:07not for readings.
- 34:08And please don't ask the pathologist
- 34:10to change their minds.
- 34:12That's persuasion Madison,
- 34:13not precision medicine.
- 34:15And we all respect our pathology
- 34:16colleagues and I think we all,
- 34:18you know,
- 34:19I know that oncologists really think highly
- 34:21of most of the pathologists they work with.
- 34:23And I think that they don't realize
- 34:25that when they do pursue persuasion
- 34:28medicine that it's actually not
- 34:29what the biologist wants to hear.
- 34:31They don't want to be second guessed.
- 34:33They want to if if if we're giving you
- 34:35a reading, we're giving you a reading,
- 34:37we really believe that's right.
- 34:39And just like you shouldn't go back
- 34:40on the test and change your answer,
- 34:42don't change your answer.
- 34:44It's if.
- 34:45If that was your first impression,
- 34:46it's probably your true impression
- 34:48and probably your best reading.
- 34:50And so with that,
- 34:51I just want to thank the people
- 34:52in lab that do all the work.
- 34:53I get to talk about it,
- 34:54but it's really a crew of people that do
- 34:56all this stuff that I told you about.
- 34:58I especially like to point out mirror
- 35:00to Matafi who started that and started
- 35:02building this essay in the lab over
- 35:05two years ago now and then my Yale
- 35:07collaborators and funding sources etcetera.
- 35:09And then here's the the the key
- 35:12group at our last holiday party,
- 35:14our lab group Aileen has now left.
- 35:16She was involved in a lot
- 35:18of the analytic stuff.
- 35:19Matt Lou helped out with some of the.
- 35:20Analytic stuff as well.
- 35:22And then and Jack and Katie
- 35:24weren't at the party,
- 35:25so they got their picture separate.
- 35:27So with now, I've also left
- 35:28about 20 minutes for questions,
- 35:30if there are questions.
- 35:31Thank you very much.
- 35:40So we have 4 questions in the chat.
- 35:43Maybe while you're warming up,
- 35:44should I start with those?
- 35:45Oh no, there's only two.
- 35:46What about discordance with
- 35:48pathologists reading the same
- 35:49slides after a washout period?
- 35:51So Manju Prasad,
- 35:53a esteemed pathologist in our department,
- 35:55asks a very pivotal question, that is.
- 35:58When you're doing any kind
- 36:00of pathologist study,
- 36:01when you read it once,
- 36:02if you're going to read it again,
- 36:03you should have a washout period.
- 36:04That is so you don't remember
- 36:06that case because surprisingly,
- 36:07pathologists have a really good memory for
- 36:09what the morphology of cases look like,
- 36:11and they can also remember the
- 36:13patient's name on the label.
- 36:14And so a lot of studies have
- 36:16a washout period.
- 36:17We didn't need a washout period in this
- 36:19study because they only saw the slides once.
- 36:21So if we're going to show them to them
- 36:23again and if we're going to do any
- 36:25kind of intra observer reproducibility,
- 36:27which we didn't do and some
- 36:29other studies have done,
- 36:30we would need a washout period.
- 36:31But in this case,
- 36:32a washout period was not required.
- 36:34And then Timothy Robinson asks,
- 36:37is heterogeneity within
- 36:38the tumor important issue?
- 36:39Is it more important to do a small
- 36:41percentage of cancer cells that
- 36:42express a high amount of heart, too?
- 36:43Or is it more important to know that
- 36:45a high number of cells expressed at
- 36:47least the minimum amount of her too?
- 36:48Wow, phenomenal question.
- 36:50That's Jax three, that's his.
- 36:51Thesis project,
- 36:52I think that's a great question.
- 36:54We obviously don't know the answer.
- 36:56All the pathologists in the audience
- 36:57know that her two is very heterogeneous.
- 36:59Not only is it heterogeneous
- 37:01from within a slide,
- 37:03but it's heterogeneous between cuts.
- 37:05And all the pathologists in the audience
- 37:06know that when we sample one core
- 37:08biopsy that's less than 1% of the tumor.
- 37:10And so there's no way for us to actually
- 37:12answer that question about true
- 37:14heterogeneity of the patients tumor.
- 37:16But what we can add,
- 37:17we can ask about heterogeneity
- 37:18on the slide and we can and are
- 37:21asking at that question.
- 37:22That is,
- 37:22how important is high expression
- 37:24in a single cell versus high
- 37:26expression in the average cell?
- 37:28We started with the average.
- 37:29You have to start somewhere,
- 37:30and I don't know that the
- 37:31average is a correct answer.
- 37:33You could argue because of
- 37:34the bystander effect of TDXD,
- 37:36it's actually the highest ones
- 37:38that make the most difference,
- 37:40but we don't know that.
- 37:41That's just speculation at this point.
- 37:45Let's see. Now it's your turn.
- 37:49It doesn't.
- 37:51Say.
- 37:55That's a great question.
- 37:59We can do more.
- 38:00So as soon as I had the assay built,
- 38:02I applied for tissue from AstraZeneca
- 38:05adicci senko from the Destiny 4 trial
- 38:08and was rapidly told I would never see that.
- 38:11And it's, I don't fault them for that.
- 38:14They have their own people that
- 38:16can do quantitative work and they
- 38:19have an FDA approval for IHC 0123.
- 38:21So they don't want to have to
- 38:23change their FDA approval.
- 38:24They're making a lot of money on this
- 38:26drug and it would be detrimental to
- 38:28the shareholders of that company to
- 38:29have me have access to that tissue.
- 38:34My question was how much heterogeneity
- 38:37do you see in the ATOMAL expression?
- 38:39Because you're taking so many fields of
- 38:41view and taking an average, do you see
- 38:43a lot of heterogeneity there or is it?
- 38:46So that's a great question.
- 38:49Heterogeneity within a core
- 38:51biopsy is quite substantial.
- 38:53And as you know when you read them,
- 38:55you see bright areas and not so bright areas.
- 38:57And you know how do we handle that?
- 38:59Well, someday we'll know how you
- 39:01know whether it's the highest sell or
- 39:03the average sell or the lowest sell.
- 39:06That's most important for response
- 39:07to Trump drug seeking.
- 39:09But we don't know that yet.
- 39:10And so in the same vein of OK,
- 39:13we're just going to take a core biopsy and
- 39:15say that that represents the whole tumor,
- 39:17we're going to just take the
- 39:18average and say that that.
- 39:19Represents the expression of her too.
- 39:22And the second question
- 39:23moved for the clinician.
- 39:25We see situations with heterogeneity
- 39:27where we have a clear 3 plus tumor where
- 39:31the patient gets you know trastuzumab
- 39:33and there's complete response and
- 39:35there's another tumor which was her
- 39:37to negative and was zero or you
- 39:40know one plus which didn't respond.
- 39:42So what will these patients benefit
- 39:45from a second round of DXD or
- 39:48when they have two distinct?
- 39:52Her two profiles to maybe I can use the
- 39:55microphone since there's 71 people online.
- 39:58Yeah, when I but I, I do want
- 40:00to clarify the question because,
- 40:01I mean we wouldn't use.
- 40:05We wouldn't have used a standard her
- 40:07two therapy if they were one plus.
- 40:13Why don't we choose?
- 40:18Do we use her two therapy, I mean. Yeah.
- 40:25But the patient?
- 40:29Patient had complete response
- 40:31to that through. So it was our CB0,
- 40:34but then the tumor which was
- 40:36one plus still extensive.
- 40:39Yeah so I mean it depends
- 40:41on the clinical situation.
- 40:42We know pretty clearly now that with
- 40:45before you know with the previous
- 40:47generation of her two therapies that
- 40:49you do not see any benefit with non
- 40:51her 2/3 plus or amplified cancer.
- 40:54So the her two lows do not respond
- 40:55to the previous generation any of the
- 40:57previous generation of her two therapies.
- 40:59So but with now with Tristan Madrox
- 41:01taken you know I think you could
- 41:04you know make a case that you know
- 41:06you might you would see potentially
- 41:08could see benefit both.
- 41:09And that clearly amplified in
- 41:11the her two lows.
- 41:12But prior to that we would look
- 41:14at a case like that on a case by
- 41:16case basis and say well let's use
- 41:18the her two therapy to get rid of
- 41:20that usually more aggressive her
- 41:22two her two positive cancer and
- 41:24then we'll worry about the her two
- 41:26negative or her two low cancer later.
- 41:28But it's it's you know again the
- 41:30the field is evolving now that we
- 41:32have these drugs that work across
- 41:34different levels of her too.
- 41:35I mean getting to in your earlier point
- 41:37that the two questions were brought
- 41:39up about her two heterogeneity and
- 41:40I think that's really interesting.
- 41:42Again with the first generation,
- 41:44her two therapies, it was very clear.
- 41:46We actually did a prospective,
- 41:47big prospective trial with with the other,
- 41:51the first antibody drug conjugate
- 41:53that doesn't have bystander effect
- 41:56and in that study a heterogeneous
- 41:58cancer responded much work much less.
- 42:01Effectively to a heterogeneous cancer
- 42:02than it did to a non heterogeneous
- 42:05cancer and and quantitatively that
- 42:07the to your specific question what
- 42:10mattered was the percent of her two
- 42:12negative cells not the intensity
- 42:15of her two on themselves.
- 42:18Again with a drug that has bystander
- 42:21effect as as I think David was alluding
- 42:23to that might be switched and maybe
- 42:25just if you just need to have a
- 42:27certain number of her two strongly
- 42:29positive cells to get the drug in.
- 42:31And then the and then the bystander effect
- 42:32will take care of the her two negative cells.
- 42:34We like to test out
- 42:35prospectively with we haven't.
- 42:38Had the funding yet to do that trial.
- 42:42Yeah. And I enjoy your talk, David.
- 42:46Is any do you have any information?
- 42:50The conjugate drug can get activated.
- 42:54In the extracellular and
- 42:56microenvironment of tumor cells.
- 42:58So I I would again defer to Ian,
- 43:01who's much more of an
- 43:02expert on this than I am.
- 43:03But it's my understanding that the drug,
- 43:05once it comes off,
- 43:06it has to be cleaved inside the cell.
- 43:09But once it comes off,
- 43:10it survives in the extracellular environment.
- 43:13And that's how the bystander effect works.
- 43:14That's how it can kill neighboring cells.
- 43:16Bystander effect doesn't really require.
- 43:20To go into the cells as long as it's a.
- 43:25Present in the microenvironment of the
- 43:28tumor cell in the enriched fashion
- 43:31you you will have some activities.
- 43:33Well the drug is an inhibitor
- 43:35of topoisomerase,
- 43:36so it has to get to the nucleus somehow.
- 43:38I guess to have its effect
- 43:40you can get activate.
- 43:42Outside
- 43:42of the cells. You don't have to take
- 43:45anybody to go inside the cells.
- 43:48Right, but that that that but
- 43:50the antibody doesn't necessarily
- 43:52take the the drug I guess can get
- 43:54into cells without the antibody,
- 43:55but the reason they conjugated to
- 43:57antibodies so you can increase
- 43:59the dose locally to the tumor.
- 44:02Michael environment.
- 44:03We have a more protease type.
- 44:07To break up the linkage between
- 44:11conjugate drug and the conjugate ohh,
- 44:13that'd be fine.
- 44:15That that that means you read that
- 44:18could partly explain why the the
- 44:23heterogeneity potential difficult
- 44:25involvement as well as you may
- 44:29have another interesting parameter
- 44:31to assess now today with the.
- 44:36Mass Effect. We could look into.
- 44:40Whether they're saying reached?
- 44:43Do you conjugate?
- 44:45Drugs.
- 44:45And in that case you would
- 44:46argue that it worked.
- 44:48It would work without trustors
- 44:49maybe even being present.
- 44:51You could you get the deconjugation
- 44:53even if there's no target present.
- 44:55That's that's why you get a negative.
- 44:57Right without right without her two
- 44:59present if if the if if it's a true her
- 45:0220 the drug could still work because
- 45:04it could get deconjugation and be effective.
- 45:07Everywhere in the body.
- 45:09Anywhere in the exercise room.
- 45:12Have unreached.
- 45:14That particular,
- 45:15yeah,
- 45:16I I think that you know,
- 45:17the the question is the toxicity
- 45:18then and that's actually the problem.
- 45:20I didn't go into that.
- 45:21But one of the problems with this
- 45:22drug is it has pulmonary toxicity
- 45:24and that patients get interstitial
- 45:26lung disease about 10% of the time.
- 45:28And that's another reason why
- 45:29you need a companion diagnostic.
- 45:31And one wonders if perhaps the
- 45:33interstitial lung disease is due to extra,
- 45:36you know,
- 45:37extracellular environment cleaving the
- 45:39drug even in the absence of her too,
- 45:42although we've also found
- 45:43that her two is present.
- 45:45Normal Airways at about the level it is in,
- 45:47low in low in about at about
- 45:491/4 UN quote one plus level,
- 45:51or between four and six
- 45:53animals per square millimeter.