#112 - Ned David, Ph.D.: How cellular senescence influences aging, and what we can do about it

Hey everyone. Welcome to the Drive Podcast. I'm your host, Peter Attia. This podcast, my website and my weekly newsletter all focus on the goal of translating the science of longevity into something accessible for everyone. Our goal is to provide the best content in health and wellness, full stop, and we've assembled a great team of analysts to make this happen. If you enjoy this podcast, we've created a membership program that brings you far more in depth content. If you want to take your knowledge of this space to the next level, at the end of this episode I'll explain what those benefits are. Or if you want to learn more now, head over to peterattiamd.com subscribe Now without further delay, here's today's episode. My guest this week is Ned David. Ned is the president of Unity Biotechnology, a company that he co founded in 2011. In this episode we're going to talk a little bit about Unity, but more importantly we talk about the science upon which Unity is developed, and that is the science of senescence or cellular senescence. We begin this episode by putting that into context. I think if you're interested in the space of longevity, you're listening to this podcast. You've undoubtedly heard the term senescence, but it might not mean much to you. And I think what Ned does a great job of here is explaining not just senescence, but where it fits in the overall lattice, if you will, of all of the different cellular processes that occur during aging. So where does it fit in with the role of MTOR inhibition, caloric restriction, mitochondrial dysfunction, stem cell exhaustion, methylation of DNA and epigenetic change, all of these sorts of things. We also talk quite a bit about Ned's background as a serial entrepreneur in biotechnology. Ned is at least partly responsible for the development of a number of FDA approved comp and he talks openly about what he learned good, bad and indifferent along the way and how that helped him at the beginning of this process of creating this company at Unity. Define sort of the jugular questions that needed to be addressed as sort of a proof of principle. In fact, I found that part of the discussion most interesting and I think you'll know what I'm talking about when we get to that part in the episode, because I found that exercise that he and his co founders went through between about 2011, 2015 to be some of the most interesting thinking around this idea of company creation. Ned is a prolific innovator. I think when he was about 30 he was named to the top 100 innovators in the world by MIT Technology Reviews he holds a PhD from Cal Berkeley, and he got his undergrad degree in molecular biology at Harvard. So without getting into too much more of the details of this, please enjoy my discussion with Ned David. Ned, awesome to see you today. Thank you for coming by.

Oh, thank you for having me.

I feel like I haven't seen you in person in way too long.

Is this true? We tried to get you to come to dinner.

Oh, God, I feel horrible about that. Yes. Sorry.

Yeah, you were distracted. It's all good.

No, you know what I was doing?

You were doing a podcast.

I was doing a podcast, yeah. That I thought would take two and a half hours. It ended up taking six hours.

That must have been an intense experience.

It was a very intense experience, and I felt horrible after. I'm sorry. So I owe you an apology for that.

It's okay. We love you.

There's so much I want to talk with about you. In fact, I've been bugging you for about a year to come on the podcast because what I was hoping we could do, and we can never do it when there's a microphone in front of us, but was sort of reproduce a dinner conversation that we would have ordinarily, which would be pick some topic, and we go way off on a tangent about it, and it could be energy, it could be biotech, it could be whatever. But some of the most interesting discussions we've had over the past five years have been around longevity, something that we both share an interest in. And, God, it's been probably nine years since you talked to me about what became that which you're doing today. Is that about right?

Yeah, that's about right. It was 2011 towards the end. Yeah. Actually, we're in December now, so it's actually been somewhat more than eight years.

So I want to talk a lot about your work. You're always a guy who's got a lot of hats on. Right now, you're mostly wearing one hat, and that's a hat that puts you squarely at the center of a pretty big circle with a bunch of folks working at a company called Unity Biotech, which we'll certainly get to. But I think for listeners to really understand what you do today, what your company does, they need to sort of understand the journey you've gone through over the past several years and how that's sort of shaped your thinking about an interesting problem. You're a serial entrepreneur, and we will likely discuss some of that in your background. But let's just start with how you think about this problem that I think about which is, how do we help people live longer? How do we help people live better? How do you define that, by the way? I don't want to impose my definitions on you. What is longevity to you?

Well, longevity for me would be being able to live without the indignities that I've witnessed. We all witness in our lives, all of these features of aging that seem to be inescapable. So my father, for example, he has profound degenerative disc disease, which makes him functionally immobile. It defines his life. My stepfather died of Alzheimer's at 87. That defined the final chapter of his life. So I have an up close to these things in other people. In addition, we all, and you and I are now, I'm a little older than you, I'm in my 50s now. We are witnessing these changes in ourselves. And for me, longevity would be the ability to use what I know how to do, which is science and biology, and be able to change how we get to live our lives, to be free of these indignities. And I think it's something that we can do, and we are doing it. And so for me, it sort of began as a dream, but now we're generating human data that says this, we can actually do this.

So I remember when this started, Ned, circa 2011, how you really steeped yourself in this field, which at the time was kind of new. You had already done a number of interesting things in biology that had led to the development of drugs, but none quite in this space. I mean, I literally remember many nights I'd be driving home and we'd be talking on the phone and you would be telling me about things that you had just read about. And I saw this paper, and it's 10 years old, but it was. It was almost like you were going through a second postdoc or something, getting up to speed in this. I've always liked the way you've sort of explained your evolution of thought there. Do you want to maybe for the listeners, give them a sense of how you developed a framework around this about.

Sort of aging biology? Yeah.

Why do we age and what can you do about it ultimately?

So maybe it's helpful for me to just create some context. And so the way I think about this and the way I explain it to people that are new to this or people that aren't scientists, is I. I always talk about there these sort of three principles that if you remember nothing else from listening, if you're awakened two weeks from now in the middle of the night, it's these three principles that I think are a good way to think about this. And the first principle is that aging is not a rigid thing. So it's this flexible, malleable thing. And nature has, throughout evolutionary history, sort of bent and twisted aging for its own purposes, to create creatures that have very different lifespans. And this kind of takes us to the second principle, which is that nature has done this with these control knobs. These are sort of biochemical systems that nature twists. And these systems are now something we're learning. And this takes the third principle to turn as people that do drug hunting like us. And so it's these three principles that nature is flexible or that aging is a flexible thing. And nature has then bent and twisted control knobs to make it flexible and that these are turnable stuff. So if you take those three principles as the context, you may ask, well, why do we as scientists, why do I believe these things are true? So if you just look outside at nature and creatures across phylogenetic history, you see very similar creatures with very different lifespans. So if you take the hard clam, so this is this thing you can eat at a clambake. If you don't eat it, it will live about 40 years. And it has a deep ocean dwelling relative called a quohog that lives at least 500 years. And these are very similar creatures. They look very much the same. And no one really knows how long this quahog lives. This 500 year thing was just because that was what the age of the wreck off of which it was pulled was. So these are very similar creatures on the order of 12 fold, different lifespan, similar story. If you flip over to, let's say, the order of rodents. Actually, let's not even go to rodents here. Let's just talk about mammals, because that's us. Of course, rodents are mammals too, but we are mammals as humans. So if you look at the shortest living mammal, which is this thing called the tiny shrew, lives less than a year, then you look at the longest living mammal, so it's called the bowhead whale. And again, no one knows how long a bowhead whale actually lives, so the estimate is at least 200 years. So again, you've got this 200 fold difference at least in creatures that kind of have the same biochemistry. We're both mammals. Now if you flip over to rodents, it's the same phenomenon, okay? You can take a field mouse, which can live somewhere between two and three years, and then you find this naked mole rat, which is this very unusual looking subterranean creature that's blind and hairless. This creature lives 10 times longer, lives on the order, even more than 10 times longer, lives on the Order of 30 years if it doesn't die of some trauma. And again, these are in the same order. And so these are closely related creatures, very, very different lifespans. So nature has clearly gone to town on this and created these marvelous examples of disparate lifespan. Sort of the same creature, the same biochemistry. So this kind of takes us to this idea of that nature has done this, how has it done this? And it's done it with these control knobs. And I'll walk through why we thought there were control knobs and how we turn them. So the first control knob that got discovered molecularly was the work of Cynthia Kenyon. And this was a paper that blew me away. I was first year in graduate school, maybe second year. And Cynthia published a paper that was pretty heretical at the time. And the paper showed that you could knock down the function of a single gene in a worm, C. Elegans. So it's about a millimeter sized little worm. And when you knock down the function of this thing, it doubled the animal's lifespan. And this was a wild result because at the time, aging was thought of as this kind of decay process. But the notion that you could essentially break the function of something, or at least make it function a lot less well and double the lifespan of a creature was just a total mind warp for me and other people. Just like, oh my gosh, you can dent something and it gets better. Now, what's happened in the intervening decades? This has been repeated in flies, it's even been repeated in mice. You can knock down the function of a single gene and calorie restrict an animal and you can double its lifespan. That's like you or me living to 160. Okay? Because this is a creature with really similar biochemistry to ourselves. So this just said that you could take single genes, turn them and do radical things to lifespan.

Now, in fairness with Cynthia's work in C. Elegans, I always felt that it wasn't the best model to extrapolate from because of the division stopping at the germ cell. And therefore, if you take DAF2 and DAF16 and project them forward to mammals, I don't think we've seen the same magnitude of reduction with attenuation of, have we?

No.

And maybe it's worth rather you explaining it than me. Do you want to tell folks what DAF2 and DAF16 do just to bring them along for the ride?

So these were genes that were discovered in Cynthia's screen as receptors and transcription factors associated with what we now talk about as the IGF1 receptor signaling pathway. And if you go in. So this is something that now has been explored in great detail in mice, for example, and the analogous knockdowns in mice of the receptors don't produce the same degree of longevity that you can produce in a worm. Now, interestingly, a paper published somewhat recently, this was Nir Barzilai and actually Pedro Beltran, who I work with now with an antibody that antagonizes the ignorance IGF receptor. Yeah, it extends life, but there's a sex difference, so it only benefits the females. And it's not something that translates perfectly. But I think that's not the interesting piece in terms of the whole kind of story of what we're learning about aging was to us and to me, it was, oh, my gosh, you can damage the function of a single gene. The fact that it still works in mammals is remarkable. The fact that it works less, it's not as cool. It's a little bit of a bummer. But to me, it was really the. It was the DAF to DAF 16 observation that opened up the field and said that there were these knobs that you could turn and you could get these radical impacts on longevity.

And the additive value of DAF 16 plus caloric restriction was also very interesting in Cynthia's worms. And I actually thought that that was perhaps the most extrapolable insight to mammals. But to your point, it was a proof of concept, right? It was, this thing is malleable.

Yeah. And to me at the time, it was just like. It was as though the mask tipped a little bit and you could see the face underneath. Like, oh, my gosh, there's something almost programmatic going along here, as opposed to just this idea that you just decay. And that was exciting. And that paper stuck with me for several decades. It was not something that I chose to work on, although I became friends with Cynthia at some point in the early 2000s, and we continue to be friends and talk all the time. But that particular biology is not. It's more of a marker people use now as opposed to something that people are actively trying to perturb. So going back to this question about of knobs, this goes to our. This third principle, which is that we can turn some of these knobs. The first knob, actually, that got turned in a super aggressive way goes way back to the 1930s. And it was this guy at Cornell named Clive McKay. And he had a colony of rodents, and this is shortly after the Great Depression, and his lab didn't have a ton of money. And in an effort to keep portions of his colony alive, he fed some of the animals all the time, and then other animals he fed infrequently. And what happened was not what he expected. The animals that were restricted with food lived longer. And it was the first time this ever got experimentally demonstrated, albeit by accident. And for me, that was the first time that scientists had sort of set out for a very funny reason and turned a knob that extended life. And it brought forward this idea that as we live, aging, or your biology is making a decision about the rate at which you are aging. Now, flash forward several decades. A molecule is discovered on Easter island made by soil bacteria. It's one of your favorite molecules, rapamycin. Now, the aging effects of rapamycin were not figured out until about 2003. And then the awesome work of David Saptini eventually linked this calorie restriction observation from decades and decades earlier to rapamycin. And it turns out that rapamycin and calorie restriction are both turning the same control knob. And this is pretty wild because biology typically only invents a few ways to do things. And what was really neat was the way in which these two totally different approaches were both touching the same biology. So it's my belief that this biology. So there's this complex called mtor, which is this megadalton complex. It's this master decision maker of whether or not we are choosing to divide and make more biomass because there's enough resources, or are we choosing to fight another day? And this biology, that rapamycin, CHIR restriction and restriction of various other things like methionine, is the single best validated biology across labs, across species. And one of my co workers, who's a sort of incredibly brilliant but cynical guy, always says, if you want to know what the real biology is, it's the stuff that works in every lab, no matter who's doing it. Okay? Rapamycin and calorie restriction definitely have that feature. It works in all these labs.

Did you know that I tried to get a personalized license plate for rapamycin and it got rejected by the DMV in California because rapamycin is a drug and you can't have a license plate that's a drug. So then I tried again, in vain, to get Rapa log as a license plate, and I got thwarted again because apparently someone at the DMV was smart enough to Google Rapalog and figure out that it's an analog of rapamycin, which is also a drug. And I got the same rejection letter from the dmv.

I would just assume, knowing you, you would have done rap a man, which sounds vaguely like a supervillain. Okay. But no, we didn't go stop here.

I'll tell you over dinner what I eventually went with.

Okay, gotcha. So anyway, there's this MTOR thing, which is the best validated control knob. The next knob that got turned is this thing with young blood. So this is something that's been sort of popularized if you watch things like Silicon Valley. But this goes back ways. But the first time that the lifespan effects of this were demonstrated was in the 1970s. And so what you do is you take two animals, one's young and one's old, and you literally suture them together and their circulatory systems join. And it's not a giant mental leap to imagine that crap in old people is bad for you. So the old blood would be bad for the young. The awesome result was that stuff in the young was good for the old and it could extend life by as much as 15%. These are with animals that are sutured together, which is not exactly an optimal way to live. So that tells you that's another knob. There's stuff in young blood that is able to exert biology and do good things. And I think that's going to be an area that will be fruitful. The next sort of control knobs we've learned about. So mitochondria age. So mitochondria are the descendants of ancient bacteria. So they have their own DNA, they have their own genomes. And mitochondria live a really hard life. And so their mutation rate of their own DNA is somewhere between 100 and 1000 fold faster than our nuclear mutation rate. So their DNA just gets all chewed up. And as a consequence, by the time you are in your 70s, you can go into a human being and look in their colonic crypts. And on the order of half of the cells in their colonic crypts don't have functional mitochondria. They can't utilize oxygen to make energy or do all the other things that mitochondria do that are important. And so that's something that we've learned that is clearly part of this aging story. Another thing that could be a knob, and this is an area of some intense debate these days, is this thing called the methylation clock. So this is this ever ticking clock in which these methyl groups, this is a little carbon atom with three hydrogens around it, are attached or detached over time to the various C's in your GATC code. And when you're young, it's essentially these five methyl Cs, these methyl groups on your DNA. It's like a crisp pegboard where everything's lined up perfectly and you've got areas where they are and crisp areas where they are not. And gene expression is not noisy. And as we get old, it's like someone drops the pegboard and suddenly you've got methylations where you're not supposed to have them and you're missing them in other places. And looks as though that might, and I stress the word might give rise to sort of noisy gene expression. And the metaphor I often think of for this is imagine you have a vinyl lp. If you're old enough to know what that is or hip enough to know what that is, it's kind of a hipster thing now, and you play an LP a lot. The actual act of playing that LP takes the little knobs and grooves and wears them down so the LP doesn't sound as good. And it's possible that the act of being alive and that aging actually is modifying these little methyl groups in such a fashion as to cause aging. No one knows if these changes in this epigenetic clock are the cause of features of aging or the result of features of aging, or even a little bit of both. And that's going to be super interesting area of biology.

Yeah. I've spoken with David Sinclair quite a bit about this. He uses an analogy that's similar, but has a couple differences, which is the methylation could be thought of as the scratches one gets in a CD surface. And the question, of course, being, can you restore the CD back to its original form if you have that master template? And that's not exactly the same as the analogy you've used, but it certainly speaks to the music and the disc.

Yeah, it's interesting. So I always think of CDs getting scratched because you're negligent.

Right. As opposed to just putting them in the CD player and using them.

And so there's a nuance. I mean, it's funny, those two metaphors may even, as you note, may speak to different intuitions between me and David about what's going on here. But I don't really have an intuition. I'm sort of reporting out what's sort of known. And it's going to be just very exciting to see when we can actually do experiments that can tease this apart and ask questions, like, if you take these methylation groups away, do you in fact start making cells that are younger functionally? And that's going to be an awesome experiment. David did an experiment recently, and I think you have to be a little cautious with interpretation. So twice in our lives, we press a factory reset your methylome. So you do it once at conception, and so a bunch of gene products get made which erase and reset your methylome back to day zero. Because you're now an embryo, and the program is beginning again. Now, a few weeks into your life, it happens a second time, but only in a little bit of your cells.

Yeah. So let's explain that. So when you start at conception, you have one cell. It goes through about 50 divisions.

So I don't know exactly. So are you talking about when we do the second reset? First of all, it's different in humans and mice, and I apologize, I don't know.

But it's some relatively small number.

It's a small number, and it happens within, I believe it's weeks in the human. I think it's a little over a week in a mouse. But anyone out there that works on this, and I have friends I could call, but not right this second. What happens is there's a second wa. These gene products that are made, and for a second time in your life, and the only second time in your life, you will reset. Because now you are making germ cells for your children, and they are kept in a special spot in your sex organs until you make babies. So those are the only two times that this factory reset gets pressed. And then going back to where I was saying, you have to be a little cautious with interpretation. We now know how to do this artificially. So we can express four factors called the Yamanaka factors. And these four factors, by themselves, if you express them in cells, it's super inefficient, but one in every few thousand cells, you can cause to become a reset cell with a prime.

You know, when did Yamanaka do this? This is in our lifetime. I mean, this is quite recent.

Yeah, he got the Nobel Prize. Alas, I don't have the date. I know a lot about actually how he isolated them. I just don precise dates. But basically, he did this. It was a beautiful experiment Yamanaka did. He initially identified genes, that candidate list of genes that were turned on in this sort of embryological state. And then he started using. He was delivering the genes in various combinations. He ultimately wound up paired down to about two Dozen. And then he then would take various pairwise combinations and figured out how few he could do and still managed to turn on one of these embryonic genes. And he managed to weed it down to four. And he got the Nobel Prize for that. And so what's happened in the intervening years is there's been some efforts to see could you actually impose features of youth. Because it's sort of a simple minded leap to say, oh, if you look embryonic, that's young in fact. And I think that's the little dangerous leap.

Right. Just because you don't have the methyl groups on your DNA doesn't mean they translate into the phenotype that is youth.

That's correct. What I think you do when you do Yamanakta four factor reprogramming is it's a self fate decision. You've entered a very unique cellular state. Now it just so happens to have things that are in common with youth. And so I think that when you do a reprogramming event and you're able to exert something that looks like youthful biology, you may have actually just created new young stem cells that are able to somehow pick up the music developmentally and participate. That's sort of different than youth. It's a bit of a sort of cell transplanty sort of thing, although done by the delivery of genes. So anyway, this whole question about this methyl clock is something that it's an intense area of interest in the biological community. It's evolving a lot. There's a bunch of labs that are working on this and it's going to be a very interesting next five years to see where this drops out. We sort of covered a bunch of things we've talked about.

Yeah, you've got MTOR reduction, caloric restriction, loss of the circulating youth factors, mitochondrial dysfunction, methylation clock, which sort of ties into sort of stem cell exhaustion. And then we've got another big one.

What I wanted to do was I've spent the last, now just a little over eight years working on one of these last knobs that we now know how to turn, which is cellular senescence. But I wanted to place that particular knob in the context of the others because I don't want to sort of overhype this idea, but I do want to explain why I've dedicated a large chunk of my life on planet Earth to this. Because if you look at all of these aging mechanisms and these knots that I've described, they all play a role in this. We don't yet know what the sort of underlying Primordial clock that ticks that makes us age. What we do know is that you have a series of these component mechanisms that work collectively and they create this phenomenon that we call aging. And I want to talk about cellular senescence now, because I work on it, because of all of the mechanisms. It strikes me and struck me as the simplest mechanism to perturb and make medicines that you can use to treat human beings. And I'll get into why that is in a sec, but I'll just tell you about the knob. So we all begin life as a single cell at conception. And then over the arc of our lives, we, the single cell will divide as many as 50 times. And on the road to 50 divisions, the cells that make us up will encounter some form of stress they cannot resolve. They will pull an emergency brake and they will stop dividing forever. And we call this state when you do this, we call cells that do this a senescent cell. And this is something that we find these cells in all of the tissues we've examined. And these cells, they're a very small number most of the time. Typically, it's on the order of hovering around 1% or less. Now, in some disease states we have looked at, that number is dramatically higher. And I'll talk about that a little bit later. Children don't have these cells. No, they can make them, but they don't accumulate. And we don't know why. But as we age, these cells accumulate. Now, before the work of my collaborators and my co founders at the company I work at, no one knew if these accumulating senescent cells were good for you, bad for you, or neither. And so my two co founders and now almost a decade of collaborators, Judy Campisi at the Buck Institute and Jan van Dersen at the Mayo Clinic, both of their laboratories genetically engineered mice where we could eliminate senescent cells from these animals whenever we wanted. And for the first time, we got to ask what happened? And what happens is pretty eye popping. So normally I carry this picture around on my iPhone. So I always show people this is what I work on. But essentially by a podcast, you have to use a little bit of imagination. So imagine two animals, siblings born within seconds of each other from the same mom. These are animals that are 24 months old, so it's kind of equivalent to a 70 year old person. And one of these littermates is blind. It's osteoporotic, it's frail, it has kidney dysfunction, it has cardiac dysfunction. It looks visibly old. Its littermate from whom we eliminated senescent cells from midlife until it dies. This animal lives, on average, about 30% longer, which is cool. But what's more awesome than that is that when this animal dies and when it's similarly treated, animals die, they die with many of the features of aging either absent or reduced. And that is awesome. So we're trying to do at Unity, the company I work at.

Now, before you say there's something interesting, you said, which is they have this knockout of senescence that only occurs in midlife.

No. What we do is we insert into every cell of that animal's body. We genetically engineer the animals so that we can administer a drug weekly which kills senescent cells within that animal.

But do you begin that administration at midlife? And what happens if you begin that administration at birth?

We have not done that experiment in large part because we don't see senescent cells at birth.

I see. Is there a chance that those animals would prematurely get cancer if we eradicated their ability to create stem cells at the beginning of life? Didn't Judith have some data that suggested the importance of senescence early on as a sort of break against cancer as well?

So you bring up a really important point that I should clarify. So whenever I tell people about this result, people often ask, this is an important system. Why are you messing with it? So it turns out the ability to make senescent cells is vitally important to our survival. So if you genetically engineer a mouse that cannot make senescent cells, this animal is born Normally, it's got 10 fingers and 10 toes, but it statistically winds up full of tumors before reaching reproductive age. So it tells you that this emergency brake, the cellular senescence system, is an anti cancer system. And you do not want to mess with the emergency brake. You have to leave it alone. And so in the experiment I described, where we eliminate these cells, we don't touch the brake. We allow the brake to pull completely, and for the cell cycle to stop, we only show up after. Now, I think it's still a reasonable question. You'd say, dude, it's like this is an anti cancer system, and you're kind of screwing around with it. Are you sure this is okay?

Let's take a step way back. So in medical school, we spent all this time learning about different cellular insults, and perhaps the most obvious one, and the one we could use as an example, is DNA damage. So when a cell's DNA is damaged, presumably its first choice is, can I fix this? But if a cell's fate is such that it can't repair its DNA. That's sort of when it has this bifurcated pathway of going down the pathway of apoptosis, which means for the listener, that it has a programmed form of cell death. So it basically kills itself in a programmatic, structured way. Or it goes down this pathway that you've described, which is senescence, effectively saying, I will no longer do anything. I'm still alive, but I don't grow anymore, I don't replicate, I don't reproduce anymore. My DNA is dysfunctional, as we'll talk about. I suspect it still does things. It still secretes factors that wreak havoc. But is that a fair assessment that I've just made of sort of using an example of a cell with DNA damage has that sort of choice?

It does. And we don't understand how cells make the choice between the two?

Yeah, I was going to ask you that. Do we have any sense of what sways that decision?

Well, I'll tell you some anecdotes. So what we do is we in the lab will irradiate cells or treat them with a DNA damaging agent. These are both things that.

Yeah, known things that destroy DNA.

So we have a setting on our irradiator which does both. So it both causes cells to die, and then 99% of the cells that remain will enter senescence. So you know that all those cells in the dish got the same radiation. They're all the same clone of the cell, yet some of them chose death and some of them chose senescence. I think it's a really interesting question for us to try to understand about why did some die and why did some live? Presumably it's driven by some exposure of cell state at the time.

Is there a way post hoc to examine the DNA damage of the cells that died and compare it to the DNA damage of the cells that underwent senescence? Because presumably the actual DNA damage is going to be stochastically distributed across those cells. And even though they are the same cells receiving the same radiation, they probably undergo different degrees of DNA damage. And could it be something as simple as if you damage this portion of the DNA, you lose the ability to undergo apoptosis, but you still retain the ability to undergo senescence or vice versa?

Yeah, I mean, you have to be a little tricky because if you're. So the challenge with asking cells that died what happened is that it requires a bit of a cellular seance. Okay.

I have a cellular Ouija board. We can. No, I'm just kidding. Yeah.

Since we've been talking about this as I've been thinking kind of creatively, there are these. There's moments on the order of minutes to hours after the insult happens in which the cell is kind of going through its sort of pre death throes.

And you still don't know which direction it's gonna go.

This is not something I've ever seen studied. So this could be something that just outside of my personal experience, but I just think about what we do every day in which we insult cells in an effort to make cells become senescent, but a portion of them choose death.

There's gotta be a dozen postdocs thinking about this problem, right?

Yeah, you'd have to be in a kind of hardcore apoptosis. The thing is, yeah, you want to be in sort of an apoptosis lab. I don't know who is actually working on this problem. It's a pretty interesting problem though. I think the way you'd want to get at it would be you might want to be looking quantitatively. For example, if you had some sort of mark dye that could tell you how much DNA damage a cell got. You had some sort of high content imaging and you could look down at a plate and say, oh, these guys that accumulated in the minutes of radiation, three times more of the. They incorporated three times more of the dye. These are the guys that chose death. You could do something like that. And so then you don't need a seance, you just need somebody. It's kind of a. I guess it's more of like a cellular death watch. There's ways that you could start to get at that. It's kind of cool.

Sorry to take us off that track, but now let's focus on the guys that didn't undergo apoptosis. So you've got all these cells that have undergone some insult and they've now committed to sort of a celibate life. They're not going to reproduce anymore. And if they just left it at that, it wouldn't be such a problem. It's this other thing they do that's problematic, which is they sort of poison the well for cells around them that are otherwise not damaged. Is that a fair assessment of senescence?

That is so, in fact, early on in the history of this field, which we can get into in a little bit, it was a real theoretical problem. How could something that's 1% of your cells damage the function of 99% of your cells? Well, as it turns out, these cells have a very active secretome that my co founder Judy Campisi discovered in 2008. And it's this is the means by which these cells exert bad biology. They secrete into the microenvironment around them all this crap that distorts tissue function. And that is how these cells, cells contribute. Both the features of natural aging as well as very particular diseases of aging is via this secretome called the S.A.S.P, which stands for senescence associated secretory Phenotype. And I know it's a mouthful.

Well, SASP is pretty cool. Yeah. And so it's really a paracrine feature. So in medicine we learn about endocrine versus paracrine versus exocrine features. But paracrine is when a gland can actually secrete its hormone and it goes directly to the tissue that it's operating on without having to even pass through the circulation and go around like the way, for example, insulin, when it's secreted by the pancreas, becomes systemic. But this paracrine effect is to secrete it and poison your neighbor right next to you. I guess your point now explains why if you don't have the ability to undergo senescence, that would be bad. Because you take all those cells that are damaged that for whatever and don't choose the apoptotic pathway are now they should be celibate, but they're not and they keep reproducing. And that's why you might be born looking normal, but as you accumulate injury and insult, boom, you're going to develop into tumors. But that's very different from saying, we're going to let you undergo senescence, but we might potentially block your ability to cause toxicity after the fact or other means of targeting those cells. I mean, there's many ways to do this, but. Yeah.

Well, let me just go back to this whole thing, which is that cancer thing. So we know that if you can't make cells become senescent, you dramatically increase tumors in mice. And that's a powerful lesson about what not to do, which is that don't mess with the underlying biology here. Showing up after, however, is a pretty cool idea. And the fact that this paper and I'll come back to how I got involved in all this, but the fact that eliminating these cells can produce a series of youth effects while not increasing cancer risk was very awesome and was actually kind of a theoretical validation of the picture in our minds about how this was all working. So it might be useful to actually sort of, at this moment, sort of talk a little bit about the history of where this actually all came from, and then we'll come Back to what we're doing with this now and how we're making medicines based on it. But I think it's always helpful. Place what you're doing in historical context. So this whole idea of cellular senescence traces itself back to the early 1960s. There was a very clever guy named Leonard Hayflick, who I've actually had the pleasure of meeting very randomly on an airplane. But at the time, in the early 1960s, it was widely believed that cells from us, from mammals, could had infinite capacity to divide. And this was made famous by Alexis Carell, who goes back decades before that. The leaders in the field all believe this. And it turns out this was the result of the fact that the food that was being fed to these cells, which was derived from chickens, was contaminated with chicken cells. So every time cells were fed food, they were also fed other cells. And it gave this impression that these cells were dividing forever. And this Leonard Hayflick showed up and.

And for someone listening, who's listening to this thinking, how can years, decades of dogma come from such sloppiness? It is important to understand that they're basically relying on light microscopes today. You wouldn't make that mistake because you'd be able to look at the DNA of the different cells and realize that, hey, these are chicken cells, those are mouse cells, etc. But it's a beautiful example of both how far biology has come, but also how the simplest mistakes can lead to catastrophic misinterpretation. I write about this in my book, this Story, and I remember the first time I came across it. Like you, I was sort of like, my first thought was, how the hell is that possible? But then upon further reflection, you're like, you're imposing too much of your current worldview on the problem.

Yeah, I think it's important to, to show a little bit of compassion as you have, by pointing out the limitations of their technology at the time and the context that they were living in. What's funny is I will report an interesting mistake that turns out we ordered from ATCC what we thought were mouse cells and they were rat, and as a consequence they weren't behaving properly. This was about a year ago. Okay, so these types of things are still happening.

So Hayflick turns over this 60 year belief, basically.

And so he published this paper in 1961 and it's pretty heretical. And he coins this term. He said, he calls them senescent cells, meaning cells that lose the ability to divide in culture. And he says something very prophetic. He Says this may contribute to features of aging.

Isn't that sort of like Watson and Crick's DNA?

Yeah. The thing about it does suggest a means for replication.

Yeah, exactly. The most understated, which.

I love these things. Here's the great story, is that when I ran into Leonard Hayflick at the Portland airport, having gotten off the plane, I pull out my phone and I show him. He's very old now. And I show him a picture of the mice with and without senescent cells, the term he functionally coined. And I said, this is what happened when we delete these cells that you said may cause aging. And. And it was just a mind warp for him. He hadn't heard of the paper, you know, at the time. The paper had been out for six years. You know, he's very old. Then his. His daughter walks up who lives in.

Portland, and she thinks you're accosting him or something.

No, it was immediately clear that we were.

You were fans.

Exactly. Yeah, we were fanboys. And I show her the picture and I said, this is where your dad's work went. She was like, oh, my God. And then she, like, turns to her dad and said, dad, you realize what this is, right? And so there was this moment, it was one of these great moments where you get to see this person who really architected this major insight in biology, confronted with the historical result right to his face and watching him trying to process it all. It was pretty neat. Anyway, so that's the kind of backstory of where this all came from. Now, flash forward decades now. Judy Campisi was the first individual to find a marker that we could look at in vivo. This is about 1995. So you could actually figure out, because senescence was something that you did in plates, like plastic plates in an incubator. But it was Judy who figured out the first biomarker where you could go into a living creature, into a tissue, and say, aha, there are senescent cells. It was the first time we got to know how many there are. Right. It's not a lot. And her work really raised this larger question which I mentioned earlier, which is how can so few cells do so much bad for so many cells? And it wasn't until 2008 when Judy described for the first time this thing that I mentioned earlier called the sasp, the so called senescence associated secretory phenotype that are how these cells exert bad stuff. And it's over 100 factors that have been characterized that these cells make now that drive their negative Biology. Now it turns out that a lot of what we know about the SASP was all figured out in cell culture in plastic. And what we've been working on the last eight years is doing a lot of this more in vivo. And it turns out the SASP is very different in different tissues. It turns out to be very different from different cells within those tissues in different disease states.

Give folks some of the. I mean, I know there are so many of the SASPs, but, but what's a handful of things that they have in their playbook? How do they sort of wreak this havoc on their peers?

So if you look at the sort of the totality of the sasp, everything that's been labeled a SASP factor, what you will see are kind of usual suspects of badness. Okay, so things like TNF Alpha, which is the target of the most successful drug in the world today, you know, Humira, it's an anti TNF drug. You see a factor like VEGF Alpha, the target of things like Lucentis and iah multi, multi billion dollar drugs for the treatment of diseases of the eye and also use in cancer. But that's a sort of a separate thing. So those are both SASS factors that are the targets of existing massive drugs. There's also some SAS factors that have been clinically validated. So there's one called ctgf, which if you make an antibody against that, you have efficacy in a rare lung disease that's pro fibrotic that we now know is driven by senescence. That's not a marketed drug yet, but it makes the same point, which is antibody.

So taking a step back from this, I mean, let's put some broader strokes on this. Inflammation would result from sasp. Right. So there's lots of things that go out there that basically tell immune cells, hey, let's recruit you to this area. You mentioned fibrosis. What other types of broad destructive categories of things go on out there? And I'm fascinated by this work because it's, it's just a little counterintuitive. I totally get the. And again, this is just my need to teleologicalize everything, if that's even a word. But it totally makes sense why senescence exists. It's a little harder for me to accept the breadth of its destructive capacity to its peers.

My general thinking about teleological discussions.

I know you and I could debate this all night long, which is get over it.

Yeah. Because these things are not testable. Any teleological explanation should be evaluated solely on its entertainment value. Okay, right. But that's not why we're here. I will say that there's an idea that is also teleological, but which I use and is a framework that I think is helpful. So many things that we see in aging biology in particular, they're kind of head scratchers. Like why is the system doing this? This seems bad for the individual. Didn't evolution get rid of vote? Isn't that the whole point of evolution? Well, it turns out that features of aging are manifest post reproductively.

Oh yeah, no, no. I don't think there's going to be an evolutionary explanation for this for exactly that reason. So is your argument that this occurred, call it stochastically and evolution was never there to fix it or catch it, so it just ran amok?

No, it's actually something, it's a cooler idea. So it turns out these decisions, if you want to call them that, these seemingly irrational decisions made by evolution. Of course, evolution doesn't make decisions. It's a votes with the survival of a species to reproduce or an organism to reproduce. Many of these so called decisions are things which benefit the young.

Yeah, so it's basically let's get the post reproductive folks out of the way to conserve resources for the young.

No, I don't think anything so active or sort of sinister. I think mostly it's, let's take cellular senescence for example. It's an awesome mechanism to block tumor formation in young reproductively competent organisms. So if you can make more of those organisms to make more babies.

Yeah, I guess I'm not arguing the senescence. It's the SASP that I'm struggling with.

Right. Well, so it turns out, this is interesting. So turns out the SASP does some other things that are useful. So a paper published by Judy Campisi again and Marco Di Maria, who is a professor in the Netherlands now they got interested in wound healing and what they demonstrated was that if you make a wound in an animal a week or two after you make a laceration wound at the wound site, you will see an accumulation of senescent cells and they are dumping SASS factors into the wound. And the question that Judy and Marco asked was, is this important? And so in this experiment they went in and they eliminated senescent cells in the course of wound healing. And what they saw was that the wound closed less well and more slowly. And it suggested that the SASP had another role, wasn't just, well, the sasp. This is a roll for the SASP here. Its role was to facilitate wound closure, which if you think about it, for most organisms in a naturally evolving organization, ecosystem is super frigging important. And so essentially senescence got co opted into suppressing tumors in one case and in a very different case was co opted into helping heal wound. And so I think that what you see in these diseases of aging is often the sort of unintended consequences of a system that was absolutely awesome for the young at the expense of the old. One metaphor for this that I sort of like is that let's say you innocently write a computer program to fill your bathtub. It also unintentionally becomes a computer program designed to overflow your apartment. It wasn't why you wrote it, but it is the net effect.

Yeah, no, that's an interesting point. Certainly things that favor wound healing could be quite beneficial. Some have even argued that LP lipoprotein, apoprotein little A, which is attached to an ldl. So it makes this thing called lp, has very potent pro thrombotic properties. And even though it's wildly atherosclerotic, you could argue, well, frankly, that's a very favorable phenotype to carry for most of our evolution. It's only recently that we need to concern ourselves with atherosclerosis. But there was certainly an era where having a pro thrombotic factor to help you in periods of trauma would far outweigh the tail effect of knocking off a few elders who managed to survive and die of aortic stenosis or atherosclerosis. So that's an interesting tidbit with respect to the wound stuff. I wasn't aware of that.

By the way, the other example you have, this LP is a perfect comparator to the whether or not either of these teleological explanations matters not. The point is that those are the same logic.

So let's go back to something you said at the outset, which you've now given us enough to put in context. You said, look, you went on this journey of thinking through final common pathways of aging. You sort of arrived at this MTOR CR thing probably matters a whole heck of a lot. In fact, it seems to be the only one that works across organisms, across labs. No ifs, ands or buts. You've got this loss of circulating youth factors. Clearly something is happening to mitochondria as we age that is very problematic. We clearly see this observation of methylation. Whether it's causal or not is unclear. We get a sense of what's happening to stem cells exhausting and senescent Cells. Your view, which you very briefly touched on is the first four things I mentioned are probably harder to drug than the last one. Is that a fair summation of how you kind of arrived at this?

Yeah, that's how I wound up focusing the last eight years of what myself and my colleagues have been working on was that it was how do we make medicines that target a fundamental mechanism of aging. I was not clever enough or knowledgeable enough or both to figure out how to do MTOR and cr. I mean, there are a lot of people who are trying that by trying to get more and more selective molecules. But it was not an area where I had anything creative to add. But the backstory, how I kind of got involved in this was I was sitting around actually in the Calgary airport. A lot of these important things are happening in airports. Okay. For some reason. And I was eating French fries. And in this 20 minute interval of french fry consumption, five different people sent me the same PDF and they were subject lines like, holy shit, you have to read this, this has to be your next company. And I opened up the paper and right on the front page was a figure showing these two animals, siblings, one of which had senescent cells. The other one.

These are the mice you talked about earlier?

Yes.

Now this was Jan or this was Judy. Were they collaborating at the time?

They were collaborating, though Judy was not on this particular paper. And this paper was not exactly those same mice I described. So it had a very similar or had the same means of senescent cell elimination, but there was a difference. This is 2011. These animals also contained a mutation where they made less, far less of a protein called Bubr1, which is an anaphase checkpoint protein. So this is a protein that makes sure that your chromosomes line up on the spindle. And it sort of is like a bit of a schoolmaster and it sort of says you're not dividing until everything's lined up. And so if you don't have bubr one, you just blow right through the checkpoint and you become polyploid. And Jan van der Sen, my other co founder and long term collaborator, he created this animal thinking this animal was going to get tons of cancer because he was a cancer researcher.

So let's just make sure we understand why that's the case. If Bob R1 is there to make sure your spindles line up, it means that you should not be able to divide until all your chromatin is perfectly aligned, everything is in perfect tip top order, and you're ready to undergo mitosis.

That's right.

So if you take away your master, a lot of faulty division should follow.

That's correct.

So Jan's hypothesis is we either attenuate or knock out bub R1 we should get a lot of cancer.

That's right.

Okay, what happened?

That wasn't what happened. The animals were super polyploid, meaning that they wound up with super weird numbers of chromosomes. Too many, too few, all that good stuff. The animals aged quickly, so the animals wound up full of senescent cells. Okay, so there was something about having very wrong numbers of chromosomes and all of the effects of that that caused the animals to be full of senescent cells and to age very rapidly, have features of aging that were onset very rapidly, and die.

So it accelerated the speed with which the record played, but it didn't change the music. In other words, they didn't die sooner because they got cancer. They just died sooner because they sped up their aging.

We don't know the answer to that. So these animals are extremely sick animals. So trying to make a larger statement, I think it's too much to say with an animal like that of the whole record metaphor. What I can say with I think, conviction is that clearly a whole bunch of things that go along with being old happen very quickly in these animals. And these animals die very quickly. They look visibly old. For me, it was an experiment that suggested that it was consistent with the notion that the senescent cells were actually driving these features of aging. And what's so cool about this paper and why it caught so many people's attention, even though there was a somewhat earlier paper that Jan also did, that for many, allowed one to draw the same inference, but it just didn't smell like a drug. I won't get into that paper today, but what was so compelling was that you added senescent cells through this mutation that gave rise to the production of less Bubr1 protein, and then you eliminated those cells or a subset of those cells with this insert into the DNA of every cell of that animal, and you could ameliorate a subset of the effects of senescent cells. Now, you didn't get rid of all the senescent cells, by the way. Interestingly, the animals don't live longer in that particular mutant because it's so sick when you eliminate the cells. But a whole bunch of the features of aging, for example, their bent spines, their organ atrophy, their cataracts in their eyes, these were all severely blunted when the senescent cells were eliminated. And when I saw this Paper, I thought, this feels like a drug. You just eliminate cells that are driving bad things. And so I contacted Jan and Mayo Clinic and 72 hours later we had agreed to meet. And a little time after that I set up the company. But this was a observation in a mutant dance. And I remember the sort of early blogosphere talking about how this paper didn't mean anything and this was exaggerating the role of senescence in humans and it's a mouse and all this stuff. But to me it really felt important. Now, there was a long way between that paper and when you could in ever credibly claim there could be a drug discovery program based on it. And we spent the next four years in stealth mode asking four biological questions. And I had some very patient investors who gave us sort of they spoon fed or dropper fed money into the company. We did not have lots of excess resources. But I will confess that some of the best times in my life have been under resource constraint. Because your decision making is very high quality, because every single resource decision matters. So we had four questions we were trying to ask and answer. And the first question, and none of this stuff got answered in the first 2011 paper was, do senescent cells contribute to natural aging as opposed to some genetically contrived mouse? Second question, could we find a disease, any human disease that we could model in an animal where we could eliminate senescent cells and take that disease and either stop it or even better, send it backwards? Third question, could we find a molecule that could trigger the elimination of senescent cells from a living creature safely? And last question, which is, was getting rid of these cells safe? We know that kids don't have them, but that doesn't mean that getting rid of them from an adult, like what if adults need them for some reason when kids don't? So that was a formal question that really was on our minds.

Now today I look at question four and realize that it's not an equivalence between children and adults because of the following reason. We know that if you prevent kids from being able to make them, horrible things happen. We don't know that if kids make them and you nuke them, horrible things happen, which is what you're trying to do with adults. Correct?

We don't know that.

Those could be two different things.

Yeah. So kids naturally nuke them. So we know kids can make them because you can do experiments in young animals and they make sense cells and then the synthes are gone. So in effect, that is your living, breathing experiment. Right.

That's Right. The superpower of kids is the ability to make them, which prevents the replication of a cell that shouldn't replicate. And then it has the good sense to get rid of it before it harms anyone. The adult retains the ability to make it, but keeps it around. I want to go back to your second question. It seems obvious. Now, your second question, just for the listener, if I recall, was, could we find the right disease in which to study this?

Could we find any disease? Because if you think about it, that first mouse, all the first and second mouse experiments that Jan did, both 2008 and then 2011 publications in Nature, those weren't diseases the way.

Right. They were sort of poly death.

Well, they were sort of like this animal has these features of being old. They weren't things that the FDA would label a disease like a bent spine, like who's going to develop a drug for that?

But your intuition was, of course, you can't study lifespan here. It has to be health span related. Because if you have an interest in taking this to humans, mortality is a very difficult endpoint.

Yeah. It's not the way we develop drugs.

I mean, unless you're tackling conditions that kill people quickly, mortality is a reasonable endpoint for cancer and heart disease drugs.

But sure. So in fact, I would even make us even ruthlessly more practical. We wanted to find very diseases of being old diseases, things that the FDA has regulatory paths for and endpoints that you can get drugs approved on. And so we wanted to do that, and that's what we did.

So tell me about number one. Number one, again, we take that for granted today, but it was a very reasonable question eight years ago, right?

Yeah. So again, Jan Van der Sen to the rescue here.

So, Ned, at this point, it's just you and Jan and Judy.

So it was myself, Jan Van Dersen, Judy Campisi, and a guy named Dao Hong Jo who helped us discover one of the early senolytic molecules. Also, Darren Baker, who's a professor at Mayo Clinic, was also instrumental. He was first author on the 2011 paper, and he also was the first author on the paper I'm about to describe as it relates to question one, which is how did we figure out that senescence was driving features of natural aging? And so that was what Darren Baker and Jan Van der Sen spent the next few years after 2011 doing. And that paper took five years before it published in 2016. And what they did in this paper was they took natural mice. Mostly natural. Okay. They contained one difference. We mated into natural mice that same Construct that piece of DNA that was wound up in every cell of their body so we could eliminate senescent cells whenever we wanted. And so now we got to do that in a very slow multi year experiment. But these were naturally aging creatures. And that paper took, as you know, a half decade to happen. And when we got that result, which was in 2016, we managed to also ask the other three questions by then. But that was really the trigger for us de stealthing the effort and speaking openly about what we were doing. Because if it didn't contribute to natural aging and it didn't cause a particular disease of aging and we couldn't find molecules, there was no company.

So you basically were processing question 1 and 2, 3, 4 in parallel.

That's correct. We had a small team, was relatively virtual. For a few years we were just living at Arch, the venture fund. And then we moved. When we got too big, we moved up to the Buck Institute. So we were camped out right over Judy's lab or a floor up and a few doors over.

No pun intended.

Yeah. And we essentially went to town with a small group. It was just a few people supported very intimately by Jan's group, with Darren's support and with Judy's group. And so we had this sort of virtual research group where every week we'd get together and review all the data for each of the four questions. And we had work streams for each of questions one through four. And it was a great time.

So I want to kind of pause on this journey and take a parallel or orthogonal journey for a moment because I suspect that at least one person listening, and likely more, also have some sort of entrepreneurial bent in them. And as it pertains to biology or biotechnology, I think I'd love to figure out a way to extract from you some of the lessons that you've learned along the way. You've done this over and over and over again in many companies. And I'm just sort of wondering what. Well, let's start with a broad question. You already alluded to the fact that you enjoyed that period of time. Right. It was really less of a company and more of a lab at that point. It was sort of a virtual postdoc that you guys were doing.

Yeah, it was a coalition of the willing doing an incredibly hard project. And it was far more likely that we were going to fail than succeed.

Well, that's actually the question I wanted to pose to you. So we don't talk enough about sort of what the graveyard looks like, like of these ideas gone wrong. It's quite possible that 2011 to 2016, you spent all of that time working on something and it didn't work. In fact, that would be the expected outcome of this type of endeavor. But that said, no one goes into something with a belief that it's going to fail without getting too much into the rose colored glasses that inevitably bias our ability to look back. What proof points did you look to to say there's a biological plausibility here that if it wasn't there, would have had you less likely to consider it. And if you can, Ned, try to answer it in a broad enough way that it would be applicable to other endeavors that maybe don't deal with senescent cells. In other words, I'm asking this through the lens of somebody who's considering finishing their lab or finishing their time in their lab, or even graduating from undergrad and wanting to join a company. How can they think through handicapping the odds of success, which you've done a number of times.

So the approach I take to a bold idea like this idea of making drugs that eliminate senescent cells is I try to picture. It's a simple, beautiful idea. I try to picture the end state, like, what does this look like at the end? And then I say, okay, I can see this in my mind. And then I say, well, what are the existential risks to that beautiful, simple dream? And I try to write them down in the most primitive way I can. And so those four questions, they were the four risks, which is that senescent cells don't contribute to natural aging. I'll use this particular example and I'll back out in a sec. That was a risk. They don't contribute to natural aging. They don't cause a particular disease of aging. You can never find a molecule to eliminate, or eliminating them is unsafe. And those were the four risks we came up with. And you can apply this risk to a beautiful, simple idea in any technological endeavor that I've been involved in.

What's nice about that is one of those is a very clear market risk. Three of those are biologic or technology risks. Your second question is actually a market risk question. In other words, if number one worked. So if number one is this absolutely explains natural aging, if number three was true, you could come up with a molecule that could block it. And number four was true, you could do so safely, but there was no way there was a regulatory pathway that was going to allow you to go from A to B, because Hooke spine disease was never going to show up on the FDA's list of druggable things to think about. It's not to say that it couldn't work, but now you've taken on an enormous regulatory risk that would be almost crushing to any one company. So what I'm hearing you say is embedded in your questions was actually a very thoughtful risk analysis that reverse engineered success, I think.

So it turned out to be a good way for us to focus ourselves.

How long did it take you guys to come up with those four questions? Because it was just five of you. If I did my math right, there.

Was a few orbiting. So my long term business partner, Keith Leonard, he was at the time we had founded a previous company together and he was still being the CEO at that company where I'd previously been the chief science officer. But he was involved in this and a few other just very smart people that I will pull into these things. I need very simple thinkers for this sort of thing because you must, in a very disciplined way, distill out to these primitive risks that can animate behavior over many years. They have to be durable. If you can summon the discipline and the simplicity to distill the next, say four to five years of your life down to call it two to four risks. Because any more than that and your life gets too complicated. And then you can build work plans that systematically remove each of those risks.

Or do not remove them, but at least identify them.

Yeah, identify them and then build plans. Everything we did at the company for four years, everything was those four risks. That was it. And the money we raised was pretty paltry at the time. It was all budgeted around those four risks. And whenever I go after a new thing, I always try to just go back to that simple, beautiful idea and then say, can I write down the risks to this beautiful idea? Then you build plans from them and then you build budgets and then you politely ask people for money, which by the way, almost no one would provide because this idea seems relatively preposterous at the time. The people that stepped forward were people like Bob Nelson from Arch, who has been a visionary across decades of biotech. And it was he who when I explained this to him very rapidly said, yeah, let's do this. There's some other people at Arch like Christina Burrow, who was very supportive early on. So that really was the prime anchor early on in the life of the company and animated all of our behavior. And that was four years of my life.

How long did it take you guys to define those questions now? Because the way you rattle them off, they're so logical, they're so obvious. But my guess is those were not immediately apparent to you in 2011, that those were the four things that had to be wrestled to the ground?

No, we kind of did know them.

Really?

Yeah. So it's funny, I recently went through the early. I was looking through some old files and I found an old PowerPoint where there was six risks. And it was clear that we'd done some kind of pruning down to the most primitive, because I'm kind of a tyrant when it comes down to like, we must have the simplest plan sort of thing. So there had been some pruning, but I know that we initially generated the list of a half dozen or so and then over a period of weeks, I think we managed to just in a disciplined way, shear them down to this relatively streamlined plan.

Now, did you learn this the hard way? Was there a time when you went down the path of trying to do something, lacked this discipline, and found yourself sort of looking back sometime later thinking, we wasted time, we wasted money, we didn't pursue this as linearly as we could have.

Absolutely no one really taught me this. This is something I sort of learned a bit on the fly, kind of in the eras in which I was building companies like Achaogen and Kythera. So those were all early 2000s. So Akajan was 2003, Kythera was around 2005. My first company, which I founded my last year of graduate school, we were strategy free. This was a high throughput structural biology company called Cerex. And we never had any of these intellectual tools. And so these were tools that were really developed through feeling as though we wasted time, which is your most valuable resource, and you wasted people's money, which was also valuable resource. And the net effect of this has been now this disciplined streamlining of idea and risk. Yeah, so it's something that just picked up over time and now it's reflexive. And everybody in my group, everyone thinks this way. And so whenever a new thing comes up, immediately everyone goes to the board and starts writing out risks and then starts writing out, well, this is the de risking plan for this, this and this. And okay, that means it's 18 months and this is kind of the budget.

Do you think that that type of thinking is productive or counterproductive in academia? It's clearly productive in industry. If you tomorrow decided, I want to go back and start a lab and go back to Berkeley and apply for a grant, would you encourage your graduate students and postdocs to think that way? Or would you modify the thinking slightly?

It'd be modified. But I think there is kind of value to this. I think in any setting where you have a problem or a technological thing you're trying to solve, which is being explicit about the failure modes, even if you're an academic, in an academic setting, and I'm speaking specifically of biology or something akin to it, like, I can't talk to you about math or something, because I think it drives a certain degree of honesty when things are failing. So you know what to see. And so if you're looking out for this isn't working, and this isn't working, and only this is working, and all three have to work for this project to go, you can make a go, no go decision in an academic setting and pivot to another project, because there's no end of creative ideas that you could be working on. They're limitless. And so the important thing is to conserve your most valuable resource, which is your time. And so I encourage my academic friends, some of whom listen and some of whom do, not to think similarly and to take a sort of portfolio approach to academic projects, which is. It's okay to prosecute this question for 18 months, but there are certain things we want to have in 18 months, and if you do not have them, we make a formal go, no go decision. Meanwhile, you had two other projects going. And so what you need is only one to raise its hand and say, I'm working.

Yeah, that was super helpful. Let's go back to kind of. You now have the answer to these four questions. Is it safe to say there are still a number of ways to do this? In other words, if you know that senescence is a natural part of aging, if you know that there are specific diseases for which it plays a role, if you know that there are molecules that can be developed that can target it, and you know that it can be done safely, that third question really has many heads. You can have molecules that kill senescent cells. You could have molecules that target the factors they secrete. Presumably, there are other ways you could machinate around this. Had you fixated early on, you alluded to it, that killing cells is something we really know how to do pretty well in biology. Was that the path you guys were on from the beginning, or was that a pivot?

Early on, we honored the possibility that we could either eliminate the cells because that's what was achieved genetically and was our proof of concept, but we could also come up with ways to reduce the pathological S.A.S.P. that these cells were creating, it wasn't so much as a pivot, but a decision to go one way rather than the other. Because in the beginning we thought you could do either. And the decision was driven by a simple idea, which is that were you to make molecules that would simply suppress the secretions of the cells, but not remove the source of all of these factors, you'd have a drug you had to take all the time. And the cool thing about eliminating synesthesis.

And it also assumes you know all the factors. Your approach strikes me as the more logical approach. But there are companies doing the other approach, correct?

Yeah. Well, you could take the position that any antibody therapeutic against one of these pro inflammatories in the SASP is just such an approach. But actually, I was saying something a little bit more.

I understand your point, though.

Primordial. I was suggesting if you understood, for example, the regulatory mechanism that makes the cell decide to secrete all of these factors and you target it, that then, hey, what you've done is you've shut down the secretion. The cells sitting there, not dividing, how bad can it be? But what motivated us was this would be a drug you would have to take all the time. And what we thought was so neat about the idea of making a molecule that could eliminate senescent cells, which we then named, we called them, senolytic molecules. If you could make a senolytic molecule, you could dose it once. And once you eliminate senescent cells, the cells are not there anymore. So these are not drugs you take every day, every week, or every month. These might be dosed once a year until your body makes more senescent cells. And in fact, which maybe we can talk about later in our human clinical data, what we show is that when we eliminate senescent cells from the, the painful knee joint of a human being with osteoarthritis, a single administration of a senolytic medicine eliminates pain dramatically in these humans for as long as we've looked. And so the cells, we don't know if the cells have come back, but we don't think they've come back by that time. This sort of validates the notion that you can now have a drug that's far safer. Because what kills most drugs actually is the fact that they're unsafe. That generally is a result of treatment again and again and again. If you don't have to do that, if you can go in once, surgically eliminate the cells, I mean surgically, metaphorically, here it's not surgical. You can make a safer Drug, at least theoretically. And that's why we went that direction.

So there's another big challenge here, which is how do you identify which cells are the senescent cells in vivo when you don't have the luxury you've had in the animal lab, which is you get to label those cells, you get to put big targets on them. What was the proof of concept that you could go into an organism and without the luxury of having the senescent cells raise their hand and say, here we are, metaphorically, actually send out snipers to get them.

Deep profiling of human tissues for senescence exists, but it's few and far between. And so we undertook a study, and this is after we demonstrated in animals that osteoarthritis, which is the second most prevalent disease of aging and the primary reason it hurts to be old.

What's the first, by the way?

Type 2 diabetes.

Interesting.

So what we did is we knew from animals that if we could induce surgical trauma to an animal's knee, a mouse, and we eliminated senescent cells, that we could eliminate pain and actually repair cartilage in a mouse.

Wait a second. That's counterintuitive.

I know. That's what's so cool.

Well, it's counterintuitive because of the experiment you shared with me earlier that Judith's group did. I think it was Judith's group that did this. Looking at wound healing, you would think if senescent cells were necessary for wound healing, they would be necessary for the non pathologic healing of cartilage following surgical trauma.

And they may be. So our theory about what's going on in osteoarthritis, and this is just one of the ideas we entertain here, and I can explain what data we have that supports this notion, is that senescent cells accumulate at sites of osteoarthritis. In fact, they may be trying to heal.

Got it.

But unlike in the skin, they literally fall off in the context of healing, the cells remain and essentially continue to sound the alarm over and over and over again. And we think it could be giving a sort of flawed attempt at wound healing that could be driving the pathophysiology of disease.

And the margin for error. Sorry to interrupt. Is much smaller in a joint. In other words, you don't have to heal a wound perfectly to achieve a functional outcome that is perfect. You might not have a cosmetically perfect outcome, but functionally you could have a hypertrophic scar, you could have a keloid, you could have this, you could have that. But You've closed the barrier to the outside world. But. But inside of a joint, it's a very delicate balance of one cell layer too many and all of a sudden you have a different outcome than you had prior to the insult.

Yeah.

Coupled with everything you said. I mean, that's. All of these things factor together, I suppose.

So what we were able to show in animals was that when we induced trauma by cutting the acl, which is known to be risk factor for human osteoarthritis of the knee, we got something that looked like osteoarthritis and we eliminated senescent cells, either genetically or with our drug, which we've now taken into human beings. We could, in this trauma induced setting and.

Sorry, that genetic mouse, just to be sure. That's a mouse that has a genetic tag for senescent cells that's easy to turn off.

That's correct.

Okay, one aside question. Is there a mouse model of osteoarthritis that comes from overweight or obesity?

No.

Is that the most common cause of osteoarthritis in humans?

It's a comorbidity. I'm not aware that anyone's established causality, but it would make some sense that it could be causal because of weight bearingness.

Interesting. So the animal model for osteoarthritis is an ACL injury, which is still true in humans, but it's.

There are a few different models for osteoarthritis. And so really, one of the things we've learned is that when you attempt to model disease, there are lots of off the shelf models that people have built for things like osteoarthritis because they're making a painkiller. So they do things like hurt the animal's knee and then give it a painkiller. How relevant is that to osteoarthritis in a human? It's not. You inject iodoacetate into the joint, it hurts like hell, and then you give them painkillers. So we had to search around for models that happen fast because that's the way we do experiments in which senescence played a role. And the ACLT model. So this was work we did collaboratively with Jennifer Ellisif, who's a professor at Johns Hopkins of Bioengineering. And she was someone, an old friend, and she'd been thinking about osteoarthritis and had the model in her lab. And I called her up one day and I said, we have this crazy idea. We think that senescent cells could be Driving this disease. Do you want to try to figure this out with us? And she was an awesome collaborator. Some of the first senolytic molecules we found we shared with her. And she had her model in operation. And very quickly in her laboratory, we were able to demonstrate the senolytic molecules that we'd identified at the Buck Institute in Judy's group. One of them was active in Jennifer's model of osteoarthritis. And so for the first time, we actually had a disease, a human disease, the second most prevalent disease of aging. The primary reason it hurts to be old. I can't overstate that enough. It's like being in pain sucks. And this is the reason old people are in pain mostly. And we could drive that disease backwards in a mouse. So we were just overjoyed by this because we could achieve it genetically, which says it's really senescent cells. And the second thing is we could also achieve the same result with a drug like. Like molecule. It was the confluence of those two results that convinced us. This is really cool. It seems that we got the idea right.

How does the drug actually target the senescent cell when you don't have the luxury of a genetic tag?

We spent the first. Remember, that was question three of the big four questions. We spent the first two and a half years of this whole effort searching fruitlessly and not finding a senolytic molecule. And the first molecule we identified followed swiftly by the second, and then a series of others that were very related to the second one. The first molecule identified was a MDM2P53 interaction inhibitor. And so normally, MDM2 is this ubiquitin ligase. So it walks around, and it's like a meter maid who goes around marking cars with chalk for getting a parking ticket. But what MDM2 does is it walks around and it marks proteins with. With a little molecule called ubiquitin, and it marks them for destruction. And P53 is one of its client proteins. And so if you break up the interaction between MDM2 and P53, P53 doesn't get marked for destruction, so its concentration in the cell goes up. And discovered in Judy's lab by a few people, including Remy Martin LaBerge, who was a postdoc in Judy's lab at the time, he discovered that when you did this to senescent cells, senescent cells died preferentially.

By the way, is there anything on the outside of a senescent cell that identifies it?

There are some things on the inside. And we've been searching, but it's not.

Like you have an antibody or anything that would render it externally identified.

We are searching now, and we don't have any universal external marker of senescent cells. We do have some that we just haven't talked about openly yet in various disease states. Where the senescent cells in a disease state have a markers that's on the outside, we've not found. And people like Ned Sharpless have been searching for over a decade for such a marker.

Wow. So, just to add to the complexity of the biology, if you were on a little mini nano spaceship and you were inside the joint of a person with osteoarthritis, you wouldn't be able to look out and see which of the cells are actually senescent and which ones are normal, which ones are simply injured. You wouldn't be able to make that distinction. So even if you had a special gun to shoot senescent cells, you wouldn't know which cells to shoot based on just the observation of the cell optically.

No. Now, if you had a little bit of a sniffer, eyes would not be useful if you were very small. A nose, however, would be useful. So if you could just sort of swim up the gradient of pro inflammatory and pro fibrotic markers, you would find yourself.

You'd find your source.

Yeah, yeah. Right. So I do think that the little mini spaceship thing is often very illuminating to think about biology. I use that a lot.

Your drug then targets P53.

Oh, that's right. Yeah. So P53 goes up in these cells, so it doesn't target P53. It actually binds on the MDM2 side, thereby relieving.

Yeah, okay.

And then so P53 goes up in concentration. The senescent cells die selectively. And then. And this turned out to work very well in our trauma osteoarthritis models. And another very cool result, and this is something else that Jennifer did, wound up in our Nature paper, our Nature medicine paper in 2017, was Jennifer Got knees from patients undergoing total knee arthroplasty. So these are people that don't need their knees anymore because they're getting a metal one. And she would take the cartilage at the site of the osteoarthritic lesion, and she would digest out the extracellular matrix and she'd take the cells, the cells that actually make your cartilage, and she would grow them in 3D culture, and she would either expose those little blobs of baby cartilage to either vehicle or our drug that's now in phase 2 clinical trials in humans. And she observed something awesome, which is that exposure to the drug eliminated senescent cells that were very prevalent from this site of damage.

You talked earlier about how you might see 1 to 2% senescent cells in an organism, but when you talk about a very local spot of damage like that, how highly concentrated were they?

So it's a little hard because I'll tell you a slightly different number because the cartilage stuff. So basically it's very. There are a lot of them at the site where you have the osteoarthritic injury, and you go millimeters away and then it drops way down. So it's got more puncta of it in that setting. If you look to the synovial membrane, which is. I'll talk to you about another study we did in humans where we actually counted senescent cells. In patients with osteoarthritis, the number hovers around 1 to 2%, even in patients with osteoarthritis. But it scales with, you have more senescent cells when you have more disease.

And when you say, do you mean synovial fluid? Like, if you did a joint aspiration on somebody with osteoarthritis, you're saying 1 to 2% of the CE in the synovial fluid is senescence.

So we actually did tell you what. I'll come back to this a little bit later. Let me just finish up and then we'll immediately flip to that.

Sorry.

Okay. Is that we did this experiment where we soaked the cartilage from the patients that had osteoarthritis in our drug and eliminated senescent cells. But another really cool thing is they started growing cartilage in the plastic dish. So these are cells that came from the sick person's knee.

Knee.

They had the capacity to make cartilage, but they just didn't. But once you eliminated the cells, all of a sudden they were producing cartilage again. And so that was super cool. We have yet to prove in a human being that this drug can grow cartilage when it's still in your knee. But that experiment is kind of cool because it suggests that you have this innate capacity if you are unburdened by these cells and their bad stuff they're making. So this next question about how many synapse cells do you have in the disease?

I'll tell you why I'm asking the question, which is not just general curiosity. It's really to get A question of how difficult is it to target these things in vivo? Are they ubiquitous enough that you can whack these things with an injection? Because obviously when you're doing this in a person, you're not going to have the luxury of taking their knee out to do it. That's sort of the, the etiology of my question.

So I'll tell you a little bit of what we've done in the clinic. So in human beings, we have eliminated senescent cells from patients knees with a single injection of this drug. And we can not only eliminate or dramatically reduce pain, but we can also eliminate factors that senescent cells are making. So the quick answer to your question is that this molecule is safe enough, selective enough and potent enough that we can do it. So it doesn't just work in a plastic dish, but it works actually within the knee of a patient suffering from osteoarthritis.

So this was your phase one trial with your first agent. This is the 101?

Yeah, that's right.

I've seen the phase one data, maybe explain a little bit of what was done. Phase one, for people who aren't familiar with drug studies, is mostly to ensure safety. But sometimes you'll see efficacy, sometimes you'll see that the drug actually does something beneficial. And that's a bonus if you can see both efficacy and safety, but you're typically escalating the dose. And again, you want to see if more drug leads to more toxicity. But if there's efficacy and the efficacy improves with dose, that makes you a bit more confident that it's not the placebo effect or not the effect of the vehicle that you use to deliver the drug.

That's correct. So the experiment we did, and this was all the result of what we saw in animals. The result of what we saw in a phase zero study in which we went into patients with osteoarthritis. No drugs, but we biopsied little bits of their synovial membrane and counted senescent cells. And we saw that the more senescent cells they had, the worse osteoarthritis they had, the more bone deformation they had in the knee, the more pain they had. So, emboldened by these results, we then took the drug to humans. And as you noted, phase one studies are typically for safety. We realized, though, that we couldn't really do the right safety study in patients that didn't have a senescent cell burden. Because if you're asking the question, is it safe to eliminate senescent cells from an Osteoarthritic knee, you need to have the cells to eliminate. And so that was our kind of logic in the design. And so the way we did the study was 48 patients where we did a three to one randomization, meaning three people would get drug versus one person getting placebo. And as you noted, we stepped up in dose, and it was a single dose of the drug at day zero injected into the knees of patients with painful osteoarthritis. And we then followed these patients for three months, and we checked in with them every week, and they checked in with themselves every day on a little iPhone device. And we monitored their pain.

And the investigators were blinded as well?

Oh, yes. It's called a double blind study, which means nobody knows who's got drug, who's got placebo, or what dose of drug you are on.

So there's 12 placebos, 36 treatments treated patients. And those 36 treated patients were about six per dose.

They were six per dose. Yeah. So we had six dose levels. And so they were marched up from essentially a group of a series of doses, three of them, which we, based on some modeling we did in cell culture, we thought would be subpharmacologically active doses. So we thought they'd be semi inactive or inactive entirely. And then we moved into the dose range where we thought we'd be doing biology in the knee. And we saw what happened. And we asked the patients, they had once a week meetings with their physician where they answered questionnaires about their pain, about their functional state. Then every day they would go and they'd enter On a little iPhone device, they'd answer one question, which is, how much pain am I in on a scale of 1 to 10? And what we saw when we unblinded the data was that there was a dose dependent, meaning as you go up in dose, you get more and more pain reduction and durable impact in pain for as long as we looked. When we got to three months, the pain is not returning, it's completely flat.

Do you remember what the placebo group experienced? How much of a reduction in pain did they achieve relative to their baseline?

It depends on which of the endpoints we're using. But I'll just summarize by saying that injections into the knee placebo effect is a big deal. In fact, if you did not see a placebo effect that looked like other clinical trials, you would scratch your head and wonder what's wrong. We saw a very similar placebo effect to what is seen with the injection of steroids. Into the knee. And that was actually good.

Meaning if you do a trial with steroids and with saline, for example, you saw the same placebo effect. You didn't see the same effect as you saw with steroids.

Correct. You see, the placebo groups in a steroid trial had comparable benefits. Look like the placebo effect in our trial. And that is something that one must. The placebo effects in pain studies is absolutely important, but what we saw was that we vastly exceeded anything looking like the placebo effect. So in fact, at our highest dose of drug, again because it's a phase one study, the N number of patients was small. At the highest dose, we saw patients who were entering. So this is this scale of 1 to 10 thing. Okay, it's actually 0 to 10 patients were entering on average at about a 6.2. And at the highest dose they were dropping to just over 1.

Is that comparable to what patients experience with steroids? I know it's not apples to apples.

And by the way, the reason it's not apples to apples that I actually learned on this clinical study, the reason you don't compare across studies is that different studies enroll different patients, different inclusion exclusion criteria, Even if you use the very same clinical instrument, it's really not an apples to apples comparison. That said, okay, the effect looks very large in terms of what we are doing in terms of approaching our highest dose, getting some patients close to pain free.

Now, I know that the phase one trial was a three month study. What's the average duration that patients have now been since their injections?

I don't have the answer to that question. We are not monitoring the patients in that study going forward because we didn't consent them for that. What we are doing now is we're actively dosing patients in our phase two study.

So presumably the duration will be extended in phase two.

That's right. So because we only went three months in the phase one study and we didn't consent patients to keep watching them, we really wanted to answer this question, which is, if you eliminate senescent cells from somebody's knee, how long does the pain stay away? And so the phase two study goes out to six months. So it's 24 weeks. And we're trying to replicate the phase one study as much as we can. So we're using the same clinical instruments to measure pain and function. We're similar dose levels. So we're doing placebo half mg, 2 mgs, 4 mgs. Okay. Which was the highest dose that we explored in the phase one study. And it's 45 patients per dose level, as opposed to six. So we should have sufficient statistical power to really see this really clearly. And in terms of the criteria of the patients that are coming in, they have to have painful osteoarthritis of the knee. And so there is a score, this thing called the NRS, which is this numerical rating scale. This is this 0 to 10. So it's an 11 point scale and you have to be between a 4 and a 9.

And are these patients that typically have already tried corticosteroids and only achieved limited or short term response? Like I'm trying to understand clinically somebody listening to this who should and shouldn't be excited about this type of work on the horizon.

So I think all of us should be excited about this work because not only is this a solution, so if our phase two replicates the phase one and which we all hope and believe it ought to, not only is this a means to treat the primary reason it hurts to be old, but it's a read through to this whole idea of medicine, which is, could you treat diseases of aging by eliminating these cells at sites of disease? This is just the beginning of something.

Well, let me go back and make sure I understand a few things because I'm already doing what you're doing, I think, which is sort of extrapolating to the. What it means. Is radiographic evidence a way, because you can certainly look at a person's knee on an X ray and examine the loss of of cartilage and appreciate an osteoarthritic knee. You could do the same thing on an mri. Do you know if the reverse is true? Do you know if the level of cartilage that's making its way back into the knee as a result of the loss of senescent cells is radiographically evident as well? Or is it possible that some of the amelioration of pain is due to the reduction of the circulating factors there, but not so much an increase in the structural integrity of the knee.

So what we saw in terms of the speed of pain resolution in the phase one was that within two weeks of the injection, you achieved most of your pain reduction. So it seems pretty implausible to me that that is the result of a structural change to your joint. It seems far more likely that this is the result of getting rid of factors that are driving pain acutely.

And it's possible, like my questions are probably so ignorant and I'm sure there's some orthopedic surgeon listening to this cringing we would assume that some of the pain that people experience in osteoarthritis is due to the structural part of this. But your evidence would suggest that at least part of the pain is not.

It's consistent with that idea, but who's to say? So we're going to know because we're also doing MRI and X ray in the phase two study. And so we're going to be able to not only follow pain, but we will follow structure as well. Well, but we have no idea if you will see improvements in the structure of the joint over what timescale you would see changes and improvements to the structure of the joint. This is the cool thing about doing cutting edge biology in clinical science.

I mean, I would love to take a group of patients if resources were no object, and we could continue to be absolutely sure of the safety of this. You know, you imagine take a bunch of people our age and you do a bunch of T2 weighted images MRIs of their spine and you look at These signal loss L4, L5, L5 S1 discs. Many people our age myself certainly have these blown out blackened discs that just aren't taking up water anymore.

I have them.

Yeah. It would be very interesting to note if you did directed injections of senolytic agents like this, if you could restore this signal, could you, by eradicating enough senescent cell, create an environment where the existing cell could proliferate into a healthy enough place where it takes up water? Something as simple as that. That again, it's a slippery slope in the spine to go after indications because it's not as clean as the knee, I don't think. But again, just a great proof of concept.

Yeah. I will say that I suffer from degenerative disc disease. It's. Well, everyone does at some point, but it's particularly prevalent in my family. There was a result, I did not mention earlier from mice that when we eliminate senescent cells from mice from midlife until death and we do X ray on their spines, we see a 41% improvement in the maintenance of the intervertebral disc volume.

Now, do you see a restoration or a reduction in decline?

We only measured reduction in decline, so we do not know if you could see restoration.

So that's still an unknown question in the senescent space.

Absolutely.

So it's possible you, me, and all the other folks that are in the senior category here won't necessarily reap the benefits nearly as much as the people like your kid, my kid, Right now, where you figure this out and when you're 20, you start to prophylactically take these things to reduce the glide rate of decline.

That might be true structurally, but I would say that what we saw in our phase one study study was you can take people with frank painful osteoarthritis of the knee, dose them, and two weeks later they have profound pain reduction at the highest dose. So that tells you that you are taking a big feature of that disease, the one that you get to feel on a minute to minute basis and you are sending it backwards. Now, whether or not that becomes a structural change is something we hope to understand in the phase two study.

And the other thing we I guess just don't understand, and it might take even more than a phase two study to understand is with corticosteroids we have problems, which is excessive use of corticosteroids is not a viable option. No, they themselves become destructive and or potentially lose efficacy over time. And so they're a great once in a while tool, but not a great maintenance tool. It will be interesting to know if this, if you become tachyphylactic to this, or if the efficacy increases with use as you start to increase the amount of cartilage laying tissue that exists and you tip the battle in favor of the chondrocyte over the senescent cell.

Yeah, that would be the kind of prediction one would make from the simple sort of zero order prediction would be that, I think.

Is there an example in biopharmacology where the good guy ends up winning with progressive dosing?

Well, I would say oncology, if you think about cancer as a gain of function.

Only in the cancers that don't spread though. But that's sort of. That almost seems binary, doesn't it? I guess you're right. I guess you could say that.

So because if you think of cancer as a sort of pitted battle between you, the organism and cancer, which is sort of a gain of function, separate organism based on you living in you, but not you. When you successfully treat cancer through the elimination of those cells, the good guy won.

Yeah, I guess, I guess that's true some of the time, but most of the time that's not true. It's sort of a tautology, right? It's true when it's true, but when it's not, it's not. But most of the time it's not true is the problem. But it could certainly be the case here. There's certainly a case. But even if the worst case scenario is you need a drug injected every six months or every 12 months. It's certainly interesting. Let's go one step further because this is obviously a critical piece of health span. In fact, you could argue that along with cognition, there's no more important piece of health span than the structural integrity of your body. As you age, have you, in your leisure time had the ability to think about how this might impact lifespan vis a vis atherosclerosis, cancer, or other diseases that actually shorten life?

Well, we know that atherosclerosis is another disease in which senescence plays a role. Now, we are not currently working on that. One of the things you may have noticed is that osteoarthritis, the way we approach the disease, even though it affects many of the 360 joints in your body, we treat the local version of the disease with local therapy. Atherosclerosis is about as systemic as it gets. And Jan van Dersen at Mayo Clinic published a paper. Actually, it was Jan van Dersen and a guy named. Very excellent young scientist named Bennett Childs. And this is a paper in Science in which he showed in rodents that senescent cells accumulate in the atherosclerotic plaques that form in high fat diet. Mouse, which is a model that can predict, say, statin efficacy to some extent, although it exaggerates it somewhat. Compared to the human case and what Bennett showed, these plaques are full of senescent cells. And if you eliminate those cells, what.

Are the cells that have become senescent? What's their origin?

So they appear to be macrophage in origin.

I see. So it's not the endothelial cell.

Well, no, there's three cell types. It's basically, there's a senescent endothelium, there is a myofibroblastic type of cell that's in there, and then there are macrophages.

So it's all three. It's basically the barrier. The immune cell that came to the rescue and the fibroblast that attempted to repair the damage.

Yeah, all of them. And when you eliminate these senescent cells, either genetically or with a drug, first of all, you can reduce plaque volume, which is cool. But what might even be cooler is that. And again, it's in a mouse. And so you just gotta wonder, what is that really saying about the pathophysiology of the human disease? But there is this fibrotic cap that forms on the surface of an atherosclerotic plaque plaque. And one of the ideas in the literature is that the thinning of that plaque gives rise To a unstable plaque that is clinically dangerous and that interventions that can thicken that plaque might be a therapy because you could take a plaque that you have and now convert it into something clinically more innocuous. And what Jan showed was that genetically and with drug that he can thicken the plaques of atherosclerotic plaques.

In a mouse, that would seem to counter the idea that you could lessen plaque volume. Do you have to pick between one of those two strategies? Because typically if you thicken the plaque, wouldn't you likely increase the volume?

No. So if you look at the sort of relative partitioning of how much of the plaque volume is kind of the cap and then how much is this sort of bulk, sort of lipid deposit with macrophages in it, eyeballing it, it's, you know, 90% is this kind of lipidy sort of macrophage blob. And then there's this thin little kind of veneer on top that is the cap. And so the thickening of that cap doesn't dramatically contribute to the overall volume of the atheroscleric plaque, at least in a mouse.

But both are happening. You're thickening the cap and reducing the. The subendothelial portion of the. Reducing the foam cell.

So athero is. It's a very tough place to do drug development. I mean, we've seen the PCSK9 story has been a multi billion dollar battle that has given rise to relatively moderate uptake of those drugs.

You could argue that's just due to the cost of the drug.

It's also the fact that it's a relative cost issue going up against statistics. So switching people and all this sort of thing, but it's not been. It's caused a sort of downward pressure on people's enthusiasm for doing cardiovascular drug discovery. Just the. Because now we have to. You're not using surrogate markers anymore. You're using outcome studies. You're actually following people until they die or have a serious cardiac event.

Do you see an application here in oncology? I mean, it seems like there should be.

Well, it's an area of interest of ours. So one of the things we saw in jan van Dersen's 2016 paper was that these mice from whom we eliminated senescent cells from midlife until death, they had the same cancer prevalence. So 85% of them die of lymphoma with and without senescent cells. The difference is that when you eliminate the cells, the animals from whom these cells were eliminated get cancer 30% later in their lives. So you have to kind of head scratch for a moment, like what does that mean?

And if I recall, you said they got a 30% lifespan extension.

Yeah.

So you basically created centenarians. You just phase shifted chronic disease by a third.

And some of the diseases were just dramatically reduced. So the effects on kidney function, the age effects of kidney function were reduced dramatically. Cataracts were reduced dramatically. So there's a whole bunch of behavior stuff that we don't know at that means. But these animals seem to preserve features of youthful behavior. Their spinal lordosis looks youthful. So there's a whole set of things. But one of the things that people often ask about the experiment is do they die of different things when you live 30% longer? And the answer is no, they die of the same thing mostly. Now that could have to do with the fact that it's mice and these lab strains of mice.

Yeah, they just get cancer like crazy. And it's less interesting to me that it's how much lymphoma they get. It's more interesting to me that you could phase shift it.

So we don't know why that is. But an explanation that makes some sense to me is that there is something perverse that senescent cells do to the tissue microenvironment. So this system, which is an anti cancer system in the young, could become a pro cancer system in the old by doing something to the tumor microenvironment that makes it more amenable to tumor genesis. And that would be consistent with what you see where the rate of tumor formation across the animal's life is unchanged, but its ability to take root is delayed. So you could imagine applications in oncology, but you would require something in which you had some sort of highly sort of tumor prone situation where you could intervene. There's also an idea where, if you could make cells senescent, which is what chemotherapy does in many cases, and then do a sort of a two hit strategy where you drive the cells into senescence and then you exploit a senescence associated Achilles heel. So it could be a strategy in which you deliberately are trying to drive tumor cells into senescence and then killing them. And then there are a series of cancers that we think that are age associated, that may be essentially the product of a highly senescent environment. So cancers of the skin, what if you could. Or cancers of say the bladder or something like this. These things that older people get. Could you go in and eliminate senescent cells and change trajectory of disease? That's an idea that's very cool that you could think about. But I would say that the most powerful read through from our results so far in humans are these other diseases of aging for which we have no treatments. So let us take something like the dry version of macular degeneration. This is a disease for which there is no treatment and it's Eightfold more prevalent than the wet disease that you can treat with anti vegfs. This is a disease that appears to have senescence associated with it.

What's the distribution of those two?

So people that have age associated macular degeneration, one in eight has the wet disease. And only that one out of eight people is treatable with the anti VEGF antibodies. Seven out of eight of those people are untreatable. Now, that disease, the dry disease, moves more slowly, but it makes you just as blind. And so that is an area in which senescence and senolytic medicines may play a role. But we'll have to find out in the clinic. And next year we are going with our first molecules into the eye.

Do you have an animal model for that?

No. So you have animal models of the wet disease, and our molecules work in that model. And so you could say that that's pretty neat. This is a giant opportunity. But I am personally attracted. First of all, I just want to say that when we talked about the.

Four risks defined your work stream.

Yeah. For four years. We live in a different risk set now. So if you think about it, chapter one of this entire effort really was demonstrating a human being that eliminating senescent cells could take a feature of aging that otherwise was untreatable and sent it backwards. Our phase one study, certainly if the phase two replicates, that was the end of chapter one. And we're sort of living in this chapter two moment where we're seeing how broad can we make this work? And if you think about what, what risks live in chapter two, for me, and I think anybody, would be that the risk is you have your biological disease hypothesis wrong. And animal models, they only ask and answer the questions they're built to ask and answer. And the only way you get to really ask and answer the question you want to ask ends in a clinical setting in human beings. So the way I think about diseases of the eye is you have a series of these untreatable diseases that make you blind. Where we think senescence could play a role. And we're going to explore each of these in the clinic. So essentially being able to ask in the relevant setting that can we intervene in these Diseases of aging using the very same approach that we took to osteoarthritis, albeit with different drugs.

Now, you won't be doing a real phase one here. You're going to go directly into a phase two. Right.

So this is something that we haven't really talked about yet, but notionally we're going to be going into patients because obviously your eye is something that's super, super important and you can't mess with it. We're going to be going into a very select population, first demonstrating safety and then branching outwards into multiple diseases of the eye.

How do you deliver the vehicle? Is it an injection?

Yeah. So it's very similar to clinical practice for anti veg.

Anti veg after delivery.

So it goes right into the vitreous fluid of the eye and our drug then takes up. We naturally know exactly where the drug goes into the various sub compartments within the eye, and we know where senescent cells are in these different diseases. And our drug gets there. And the clinical hypothesis is that one or more of these essentially progressive diseases of the aging eye, when we eliminate the cells, will stop.

And can you speak about the drug? What is it targeting? It's not targeting P53, is it?

No. So we have two molecules that we're advancing toward the clinic. Both of them are inhibitors of the BCL2 protein family. So these are molecules that inhibit inhibitors of apoptosis. So they cause cells to enter programmed cell death. But interestingly, we've shown in animals that they don't cause that to happen in normal healthy eyes. They only target cells that have been damaged by the disease process and the stress associated with disease process.

And so why is that?

There's something about. So senescent cells, when they enter this state, do a variety of things. They turn up proteins that are pro apoptosis and they also turn up proteins in terms of our expression that are anti apoptosis. So what we do is we go in with a drug and just give a little shove in one direction.

I see. But you're saying if you give that same shove to someone who has not upregulated or down regulated either of those factors, it doesn't seem to matter too much. Yeah.

And so we have a beautiful experiment in mouse where we have a disease condition. Okay. And we have a normal condition, mice are identical, but for the. And we put the drug in and we can see the drug molecularly going in and engaging its target because it actually breaks up two proteins that are stuck together. And you can see in these animals, both of them are equally engaging target. But the apoptosis program only turns on in the disease state. And it was a pretty awesome result because you can see the selectivity of the molecules in a living creature's eye.

Does that same molecule work in the osteoarthritic scenario?

No. So we couldn't get it to work either. In the trauma models in mice, we couldn't get it to work. When we took the cartilage out of human knees, it didn't work there either. And so it never raised its hand.

What do you think that says about the biology?

There's something about cells and their fate that determines which apoptosis vulnerability you have. They have different achilles heels, and we don't understand mechanistically why that is. We've sort of figured this out empirically and picked molecules based on their behavior against the cells that we find to be senescent in these human diseases.

So 15 years from now or 20 years from now, we will likely look back and companies like unity, and presumably there will be many like unity. You will have an entire suite of targets. You will say, well, here's the playbook. In this type of cell or this scenario, going after the anti. Anti apoptotic pathway is the way to go. In this case, we're going to go after P53 and you might have a dozen of these different targets.

Well, we're not sure yet. I think it's too early to say how this is going to play out.

Oh, so you don't think it's a fait accompli? I mean, you think it might be that there's a very small number of ways to go about doing this.

I doubt that. I doubt it will be dozens, though. I think it's going to be a small number. I think it'll be context specific. I think there'll be super creative ways that we and others come up with to exploit these different vulnerabilities. I don't think biology's Gonna have made 24 different keys to this lock. I think it's gonna to make a half dozen. And we actively search for these.

It's just interesting to me that you can turn one key and get a benefit. I mean, think about how often that doesn't work. Think of the futility of that in chemotherapy, where you target this one piece of cell cycle replication, and very quickly the cell mutates away around that drug.

So cancer, cancer is incredibly hard, okay. Because cancer exploits the single best tool biology has, which is variation. Cancer cells can divide and mutate and become anything to avoid death. They live under selective pressure, particularly in the context of drug. Senescent cells can't divide by definition, so their ability to access variation is dramatically reduced. Now that's not to say that there couldn't still be selection without division, but boy, it's way harder when you can't make a million progeny with tiny variants and test them all in parallel, which is what cancer does.

Yeah, it's sort of funny, isn't it? Cancer is the ultimate AB tester.

Yeah. We like to think of senescent cells as cancer cells that can't divide is one way. I've heard that said semi humorously, but that's actually really neat.

Right. Which is sort of funny because it's like take the top 100 most valuable traits of cancer and take away 99 of them.

Right. By the way, I was saying that in somewhat joking.

No, I understand. Yeah, yeah.

In the sense that senescent cells become senescent. Well, first of all, in vivo we don't often know why they became senescent. But one of the mechanisms by which cells can become senescent is activation of a cancer causing gene. But that could be very rare event compared to mitochondrial failure or high concentration glucose or telomere shortening.

I mean, I was going to actually ask you exactly about that example, which is do we have any reason to believe that the increase in age associated type 2 diabetes could be resulting from some sort of pancreatic senescence where beta cells become less and less robust due to senescent beta cells in the proximity?

There is some data in support of senescence in that cellular niche, but it's very complicated biology and there's even some talk about a compensatory mechanism where senescent cells actually may improve the function of some of those cells within the niche. It's an area of intense literature debate. The other challenge we have there is we don't have good models in animals of studying this. And so it's been hard for us to get our heads around. What I will say about type 2 diabetes in humans is that there was a large meta analysis of a genome wide association studies looking for the genetic correlation between grievous illness of aging and loci. Where did these mutations map? And what you saw is the that one of the very big peaks for diseases of aging maps into the control system for the establishment of cellular senescence. It's this P14ARF locus and you look at and this is where this very important gene that people use for senescence all the time called P16, which is this part of the emergency brake. Its gene lives in this locus and what you see is diseases like type 2 diabetes, mutations that give rise to that live there, mutations that give rise to late onset Alzheimer's live there, frailty lives there, atherosclerosis lives there. So a whole bunch of these diseases where we saw phenotypes in mice, you see the natural genetic variation of humans also shows a kind of tie in to senescence. And so type 2 diabetes caught my eye there because you see that in the GWAS studies.

And lastly, what about Alzheimer's disease? We have to believe that astrocytes are losing some functionality to protect neurons. Right?

So this is what my group works on. And it's something that animates a lot of us at the company. We know that astrocytes or glia, just call them glial cells. So if you guys don't know what glia is, that's it's actually derived from the word glue. So this is the cells that are not your neurons in your brain that seem to hold the rest of it.

Together, which outnumber neurons tremendously, vastly.

I think the number is on the order of 10 to 1, 8 to.

10 to 1 or something like that.

Guys got to look that number up, but it's on that order of magnitude. And what was known before we got involved was that as human beings aged, there's a dramatic increase in senescent glial cells, specifically astrocytes and microglia, which are the sort of macrophages of the brain and stuff we've been working on. If we've been looking at that trend in rodents. And we see a very similar trend now. We have not talked about doing on this yet because it's still early days, but it's hard to imagine that the pro inflammatory environment created by this vast number of senescent glial cells is good for you. One needs to ask the question, what would happen if you could eliminate senescent glial cells? Would that enhance cognition? Would it harm cognition? And this is something that we are actively looking into. But all of the work we've done over the last eight years, everything going from the mutant animals to the wild type animals to human data in osteoarthritis, and now moving into human data soon with in the eye, it would just be very hard to imagine that senescence is not playing a role in aspects of cognition loss as we age. And this is something, when I think about why we do what we do, that is something that there could be very few greater contributions that myself and my colleagues could make than making a contribution there. Because it has been an unsolved problem and a scourge to humanity.

I mean, do you get the sense that doing what you've done now, it would be very difficult for you to go back in time and do something like Kythera over again? And I'm not saying that to be critical or in any way, shape or form. I'm just saying, like, I mean, maybe tell people what Kythera did. That was a very successful company for you, but there's no comparing the nature of the two problems you're trying to solve.

Yeah, actually, thank you for actually pulling me out of. Would otherwise be a kind of of like overly sort of sappy discussion about contribution. Okay. So Kythera is actually a total kind of opposite sort of thing. And Kythera was a company myself and two co founders founded now almost 15 years ago. It's about as opposite as you can get from doing Unity. And so it was basically this idea that all this biology that's been explored for oncology and inflammatory disease, taking molecules from that and applying it to the biology of aesthetics. And we did this. And I had these great business partners that continue to be partners with me today. One of them is Keith Leonard, who's CEO at Unity and very close friend. And he's been my big brother for 15 years and continues as of this morning, calling me and giving me feedback on things. And I've just grown. And the reason I did Kythera was it was sort of a cute idea, but it was mostly because of people was these guys said, hey, let's do something together. And it was a great decision because I learned so much, in a sense, because. So the drug we ultimately got approved. We took four things into the clinic, and one out of the four things worked. And it was a molecule that causes fat cells to explode. So we went from an in vitro observation all the way to a launched commercial product called Kybella. You can go get it. Your dermatologist and Allergan acquired the company. And it was a great learning experience of just how to develop pharmaceuticals in something that didn't have historical resonance at all. And so it was a great sort of. It was a great moment where the stakes weren't as high for whether you succeeded or failed. And as a consequence, it allowed you to hone your skills of kind of. Of making really high quality decisions on risk and making drug development decisions in a way that's actually, frankly, a little more dispassionate and it was a great growth experience for me.

I mean, is it safe to say that if you had not had the experience at Kythera, because then you would have been coming from a Chaogen, right? Basically, yeah. Would you have had a more difficult time doing what you and the early co founders did at Unity?

It would have been impossible. I would have none of the intellectual or emotional toolkit to do what we did. I mean, that whole Risk thing, that was stuff we built. I mean, it was a little bit when we put together a Cajun, but it had become a kind of ritualized practice by the time we were doing Kythera projects, this dimensionalization of risk and creating work plans based on it. And so, yeah, I would say that. That there would be no Unity without there being Kythera.

Last question, Ned. What? Actually, I have two questions for you. I'm sorry. Now that I think about it, first question is, what advice do you give for a person who's studying science and trying to decide between the entrepreneurial pathway that you've been on versus a more academic pathway? What would you offer them as an insight or a set of questions that they could pose to themselves to further delineate that?

Well, I would say two things. First, don't create a false choice. All right, so I have friends that are academics that have founded as many companies as I have, and I do from time to time have career jealousy over some of the freedoms and some of the responsibilities, frankly, that they have as people who have academic appointments. There are wonderful things that you can do from the seat of academia in company creation if you are so lucky and so positioned to do so. So first, don't fall into this idea of a false choice. And I see people do that, I think out of some emotional discomfort, this desire to just move and confuse action with progress. And I'd say just slow down, take a deep breath, don't rush, you have your life. That'd be the first thing. The second thing is animated, what you do with a single beautiful idea. So something that moves you, that makes your, gives you, literally gives you goosebumps, that weird tingling sensation when you think about it, when you think how cool it is and oh my God, if we could actually make this work. I mean, few things in life rival that feeling. When a hard fought battle for data that was 18 to 24 months and the experiment finally works and you're looking at the data and you feel like the future taking root in the present, the only thing I can compare it to is love from your kids. That is the only thing that has the same emotional gravitas. Finally. Third thing, learn from people that are better than you, that are more experienced than you, that will have patience with you. I mean, the Kythera experience was that, I mean, good heavens, I was may still be sort of unemployable in normal corporate settings, yet the people there saw that I knew how to do certain things and I learned from them and I learned how to do the things that allowed us to build unity because people were patient and took time to teach. I learned from real experts. And I don't claim to be an expert at much of anything, but I do claim to have a deep appreciation for learning from people who are better and more skilled than myself. So three things.

Well, I'm going to leave it at that. I was going to ask you another question, but I think this was the more interesting question and so we'll leave it at that. And grateful Ned, for the time that you've set aside today to talk about this stuff. I think this is a super interesting topic when I think of all the pillars of longevity going back to your initial framework, right, which is things that inhibit tor, things that target mitochondrial function, things that may set back the methylation clock, slow down time in that regard. In this problem, it's not a zero sum game and it's very likely we need to be pursuing all of these strategies in parallel. But the data so far with respect to a very tangible problem like osteoarthritis is pretty exciting. So I suspect there's going to be a lot of people listening to this who are going to be very eager to follow the results of the technology that you guys are trying to bring to market, along with presumably some others down the line.

Thank you, Peter. It's been really a treat and an honor to share this with you and I've always and shall always. I love your questions. They're awesome.

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