Developing a New Class of Therapies Based on a Natural Cargo Carrier
January 6, 2023
One of the greatest challenges emerging therapies face is being able to reach the tissues and cells in the body where they need to go to provide benefit. Rather than using viral vectors or lipid nanoparticles, Evox is harnessing exosomes, a natural transporter within the body, to carry therapeutic cargo to desired targets. The company has developed platform technology to modify exosome so it can load therapeutic cargo into them to reach desired organs, the central nervous system, and intractable tissue. We spoke to Tony de Fougerolles, CEO of Evox Therapeutics, about exosomes, the company’s platform technology, and how it is using this approach to target a range of rare diseases.
Daniel Levine: Tony, thanks for joining us.
Tony de Fougerolles: Perfect. Very nice to be here, Danny.
Daniel Levine: We’re going to talk about exosomes, Evox Therapeutics, and how it’s seeking to harness these extracellular vesicles as vectors for therapeutic targets that are difficult to reach within cells throughout the body. Perhaps we can start with the challenges of delivering RNA therapeutics to various cells. What are the challenges that Evox is seeking to address?
Tony de Fougerolles: Yeah, it’s a great question as you think about RNA therapeutics, right, and you think of all of the advances that have happened over the last 5-10 years particularly, thinking about things like small interfering RNA, we’ve all heard of mRNA technology—all of those RNA therapeutics, and this even extends into gene editing technologies. All of them really rely or need to get those RNA drugs inside cells, right? And so that’s really been the challenge when those technologies were first developed, and I’ve been fortunate to have [had] a hand in developing a bunch of those from the ground up. It was about how do you make the drug and how do you design it and also how you deliver it. That first question, how you design them, is by and large largely solved. And so, it comes back to this other question of how do you effectively and safely deliver a whole variety of these genetic medicines to various parts of the body, right? So, if you think about it as an example, mRNA has been super successful in a vaccine context, but has had much more limited success in using mRNA as a natural therapeutic because it can only really, at the moment, be successfully delivered to one or two types of cells. Likewise with other drugs such as RNA interference, where there are now three or four approved drugs all delivering that siRNA drug to a particular liver cell called the hepatocyte. We could make a drug to all sorts of other targets to treat a variety of other diseases, but at the moment, there’s no way to really get those drugs to other cells. And that’s what we’re doing at Evox is we’ve developed this delivery platform, if you want to call it using exosomes, and we’ll talk a bit more about what they are and so forth. That enables us to get all of these genetic medicines into the exosome. And by using the exosome, we can now deliver these to a variety of different cell types that are at the moment, inaccessible. And so that really then opens up all of these genetic medicines to forward greater use, right? And that’s in essence of what we’re doing from an Evox perspective.
Daniel Levine: Well, what are exosomes and what role do they play in biology?
Tony de Fougerolles: Yeah, so we’ve talked about why we’re doing it—the problem we’re trying to solve. What exosomes are is they’re small vesicles, anywhere from 50 to a couple hundred nanometers in size. And they’re little spheres that are constantly being secreted by cells. And it really represents the cell packaging a bunch of protein RNA molecules, excreting it, and using it as a means to communicate with other cells, right? So it’s really how cells talk to each other. And this is a natural mechanism that occurs on a daily basis. So in our bodies, every cell will probably typically make five to 10,000 exosomes per day per cell. And so, these exosomes containing RNA and protein molecules are circulating and really getting taken up, produced by one cell, and then getting taken up by recipient cells, and providing that recipient cell with some of this information. And it’s a system, as I mentioned, conserved not only from humans down into rodents, [but also] down into plant and fruit species. So wherever you have an organism with more than one cell, this is how cells talk to each other. You can kind of think about it as the body’s FedEx system, right? Where it’s delivering packages, messages safely, effectively from one cell to another cell.
Daniel Levine: If we think about exosomes as vectors, to what extent can they be engineered to target specific cells within the body or have other features added?
Tony de Fougerolles: Yeah. That’s really where a lot of the genesis of what we’re doing at Evox comes from is. There’s this natural communication delivery system, right? So, call it nature’s lipid nanoparticle system and we’ll talk more about how that might differ, but what we’ve been able to do at Evox is really understand how cells decide what to put into an exosome and what not to put in it. And it’s a very deliberate process cells used to say, okay, I’m going to put this in, I’m not going to put that in. Using that knowledge, we can actively get cells to load our drug of choice, right? And that’s how we load all of these genetic medicines, is using some of that information. And with that information, we can target drugs to be loaded into exosomes or in some cases on the surface of exosomes. And we can even load multiple things at once. Now, not only can we engineer them to contain our drug of choice, but we can also decide to display particular proteins or ligands on the surface of an exosome so that when the cell produces it and secretes it out into the environment that exosome will now have, if you want, a ligand or it could be an antibody fragment, it could be a peptide, could be a variety of things, which will then preferentially target the exosome to a cell type that has, if you want, the cognate receptor, right? So it’s a little bit like putting a zip code onto an envelope, right? So, you’re using FedEx or the mail system, but the zip code is really what’s directing it into the right location. And so, we can engineer exosomes to have enhanced tropism for certain cell types of certain tissues, and we can do it through this engineered approach. The other thing we’ve understood as well is that the cell type that’s making the exosome can also naturally have its own tropism. So, if we make exosomes from two different types of cells, they can go to different places in the body just as a consequence of the cell that they were originated from, right? So, there are really two ways that we can engineer that targeting. One is by picking the cell type that’s producing the exosome and making use of a natural tropism. And the other is a more engineered way where we’re expressing particular ligands or receptors on the exosome that then preferentially directed to our target cell. And we’ve done this and we’re doing this in the context of delivering exosomes across the blood-brain barrier to the central nervous system. We’ve done this in the past to deliver exosomes to muscle. We’re also doing it to deliver exosomes to tumors or to immune cells. But in theory, this could be used to really target exosomes to any cell type within the body.
Daniel Levine: What’s the range of payloads these exosomes can carry, and are there size limits that discount their use in certain cases?
Tony de Fougerolles: Yeah, it’s a good question. We can engineer them and we have a variety of ways to do this where we can load everything ranging from proteins, small molecules, small RNA drugs, that can contain whole AAV genomes, gene editing components, and that can include multiple components. Or we can even do longer RNA drugs like messenger RNA. Now there doesn’t appear to be a size limit to the size of the drug that we can load. For certain drugs we can load these at extremely high copy numbers. For instance, for small RNA drugs, we can typically load 1000 to 2000 of these drugs per exosome. For proteins, it tends to be several hundred copies of a protein per exosome. And in other cases, it’s obviously fewer molecules because oftentimes they tend to be larger. But obviously, the better loading efficiency we have, then the lower number of exosomes are needed to have a therapeutic effect.
Daniel Levine: You were founding chief scientific officer at Moderna and an inventor of the mRNA chemistry and lipid nanoparticle delivery technology that formed the basis of the company’s Covid-19 mRNA vaccines. How do exosomes compare to lipid nanoparticles? What advantages might they offer?
Tony de Fougerolles: Yeah, it’s a great question. And again, it’s really great to see a bunch of that technology that we developed at Moderna over 10 years ago now come into, well I would say, widespread use, right? And mRNA really, as you mentioned, relies on these lipid nanoparticle delivery systems. And that’s something that some of the original work I was also fortunate in developing while I was with Alnylam and with folks like Pieter Cullis at UBC (University of British Columbia). And lipid nanoparticles are, if you want a synthetic manmade nanoparticle, roughly the same size as exosomes. They contain three or four components. But mechanistically they operate very differently than exosomes. The way lipid nanoparticles act, they’re a particle, they get taken up by cells like exosomes, but they seem to traffic to a different part of the cell. They go into what’s called an endosome, which is where the body often, if things come in that aren’t natural, will bring stuff in and then decide what to do with it. It’s a bit of a protective holding pen, for lack of a better word, for these things. And what the lipid nanoparticle does is, as part of that internalization process, it changes shape a little bit, and it disrupts these internal compartments called endosomes. And that’s what really allows these kinds of materials like mRNA and siRNA to get inside cells. Now the endosome is filled with immune sensors, right? Because this is how really the cells are sorting out what can be let and what can’t be. And obviously the LNP, by virtue of how they work, tend to be toxic to cells, right? And so that’s why you have to introduce chemical modifications into mRNA molecules partly to avoid the immune system from recognizing them as foreign. But it means whenever you use lipid nanoparticles, you get some not insignificant side effects in the context of a vaccine that’s relatively manageable if you’re only giving one or two doses. But obviously, in the context of a therapeutic, you may need to give multiple doses over and over again. And so, that poses some potential risk. On the other hand, exosomes seem to get into cells as well, but because it’s a natural mechanism that’s constantly in use, it’s a bit like going through the back door, right? You don’t have all of these defenses up and you are able to deliver all of these genetic medicines through a natural mechanism that really appears to be safe in non-immunogenic. So, one difference is immunogenicity and the fact that we’re able to deliver payloads really in a safe way where with lipid nanoparticles, through their mechanism of disrupting this endosome, tend to be quite toxic. The other piece is that because exosomes have a plethora of things on their surface, they tend not to home to a particular cell type, but it also means that you can now direct them to multiple cell types. Whereas lipid nanoparticles, one of the reasons they’re very successful is they get taken up by hepatocytes and by macrophages very effectively, and that’s really where their use has been limited, right? But it also means it’s very difficult to skew those lipid nanoparticles to other tissues for a whole bunch of biologic reasons that we uncovered at Alnylam about 10, 12 years ago. We don’t have that same limitation with exosomes. So, we feel we can really deliver these to a range of new tissues in a way that at the moment is still not possible with lipid nanoparticles. So, a long-winded answer, but I hope that offers some contrast: it’s safety, non-immunogenicity, and the ability to target exosomes to new tissues in a way that you can’t with lipid nanoparticles.
Daniel Levine: Evox has identified three internal programs on which it’s working. These address three different rare genetic disorders that involve enzyme deficiencies. Two are urea cycle disorders. On the third, phenylketonuria is a metabolic disorder that results in an inability to break down proteins prevalent in food. It would seem these conditions all involve liver enzymes. The liver is an accessible target today for nucleic acid delivery. Why start with these conditions, which on its face wouldn’t seem to benefit from the ability to use exosomes to target hard to reach cells?
Tony de Fougerolles: Yeah, it’s a good question, and obviously you are correct that all of these targets deliver, but I think the important thing to remember here is that these enzymes themselves all need to be delivered either into the cell membrane, like NPC, or Neiman-Pick type C, or inside the cell cytoplasm, like is the case for some of the urea cycle disorders or for PKU. And so at the moment that’s really difficult to do with other technologies. You can deliver things like short interfering RNA inside cells, but that’s only really useful to turn off expression of something. What we’re doing here is using exosomes to deliver functional copies of all of these enzymes to correct the deficiency that these patients have. So really at the moment, there’s really no good way to really deliver a gain of function into this cytoplasm longer term. I think what we’re working on are a range of ways we can target exosomes to new cell types. And that’s what we’re working on with Eli Lilly, where we’re using exosomes to deliver small interfering RNA drugs into the brain via a systemic route of administration. And that’s why we’re working on targeting exosomes to a variety of, if you want, non-liver cell types, but obviously even in the context of the liver with certain of these sorts of approaches, there’s still a huge unmet need. There really is no good way to get some of these enzymes into the cells either in the membrane of cells or in the cytoplasm of cells.
Daniel Levine: What’s the development path forward for your pipeline?
Tony de Fougerolles: As you mentioned, we’re working on a variety of things. I think our lead program at the moment, the phenylketonuria program, as you mentioned, this is a rare disease, but it affects actually tens of thousands of patients in the U.S. and Europe. So, it’s not that that rare. As you mentioned, these patients lack the ability to convert phenylalanine, which is an amino acid. So, the path forward there is we’ve developed a range of data around this program where we’re using gene therapy that expresses the enzyme in its functional form. Our goal is to use exosomes to deliver this gene therapy to basically correct the disease. The sorts of lead candidates we have now, it’s still in preclinical testing, but they appear to be 10, 20, possibly more-fold more potent than other AAV gene therapy compounds that are in clinical trials. So, with this PKU program, it’s using exosomes to deliver gene therapy that encodes for the enzyme; again, 10 to 24 times more potent. We think it can be far more effective. It can allow repeat dosing and can be non-immunogenic and can allow us to treat every patient. At the moment, only about two-thirds of patients could even take gene therapy due to some pre-existing antibodies that AAV. So, we’re in the process of finalizing the development, and then completing optimization of the manufacturing, kind of purification process. And again, the goal for that program is to file the necessary paperwork called the CTA filing, or in the U.S. the IND filing—file a CTA towards the end of 2024 for that program.
Daniel Levine: You touched on one of your collaborations earlier. I want to talk about those for a moment. You announced two that I’m aware of. The first is with Takeda, a five target rare disease focused agreement. Walk us through that.
Tony de Fougerolles: Yeah, so both the Takeda and the Lilly deals, and we can talk about both of them, are multi target deals, both five targets. Takeda are really interested in rare disease, and they’re interested in using exosomes to deliver either protein or mRNA payloads. and again you know these are things where the exosome can offer real advantages over what’s out there. We focus on Nieman-Pick type C as one of those programs. We’ve done work with them on another program, which unfortunately we can’t talk too much about. But basically we do most of the preclinical exosome design and testing, and then they will take over as we get closer to the clinic. For the Lilly collaboration, it’s a multi target deal. As we had talked a bit before, it’s using exosomes, loading them with this type of drug called Mullin interfering RNA drugs that can silence or turn off production of particular genes on a temporary basis. And we’re using exosomes to deliver these drugs into the central nervous system, into the brain, but doing it via a systemic route of administration, which at the moment is impossible to do at all. And so, this is really a long-term project. If it works, it’s going to open up this whole new class of drug to a variety of neurologic diseases. And so obviously we’re working with Lilly on a range of these. They’re providing the siRNA drug. We are loading those into exosomes, engineering the exosomes to improve their ability to cross the blood-brain barrier. And ultimately if not successful, as we get closer to going into the clinic and trial testing, then Lilly will take over.
Daniel Levine: The company has described both of these collaborations as transformative. What makes them so?
Tony de Fougerolles: Yeah, so what’s transformative is obviously, with Lilly for instance, the ability to deliver these sorts of drugs into the central nervous system via a systemic route of administration, which means intravenous or subcutaneous delivery is at the moment impossible. And it’s one of the holy grails of all pharmaceutical development or the drug industry—how do you get things across the blood brain bar barrier? So obviously, if we can do it with this type of drug class, that in and of itself is transformative because it now opens up a whole slew of diseases—things like Parkinson’s and Alzheimer’s and a variety of things that you could potentially treat. But it also opens up the possibility of using that same technology to deliver other types of drugs, whether it’s gene therapy or so forth using the same type of approach.
Daniel Levine: The company raised about $95 million in 2021 in a series C financing. How far will that take you and what’s the plan for raising additional capital?
Tony de Fougerolles: Yeah, it’s a great question. And you know, obviously we raised that about 18 months ago. That really extends our cash runway into the first half of 2025. So we’re in a very fortunate position to have a very healthy runway per se. It allows us to move not on only our own programs but our partner programs forward. We will likely do an additional financing sometime over the next 12 to 15 months. But again, as I said, we’ve got more than two years of cash to move forward. And again, all of that is really making no assumptions about new business development deals or milestone payments, et cetera, that we get from our existing partners. So, it’s very much a worst case scenario, much more likely is that we will also be able to raise some additional non-dilutive capital over the next 12 months as well. But very likely, as I said, we will want to raise some amount more in the next 12 to 15 months.
Daniel Levine: Tony de Fougerolles, CEO of Evox Therapeutics. Tony, thanks so much for your time today.
Tony de Fougerolles: Perfect. Thank you very much for having me.
This transcript has been edited for clarity and readability.
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