Precision Medicine vs Persuasion Medicine: Measuring vs Reading HER2

Transcript

• 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.