Overcoming the Limitations of Conventional Cell Engineering

DNA-modified cells can behave unpredictably in the body and there is a risk that they could proliferate uncontrolled, cause severe toxicities, and even survive unchecked for months or years. Cartesian uses its platform technology to engineer RNA into cells, making time-controlled changes. The company is developing treatments for cancer, respiratory conditions, and autoimmune diseases such as myasthenia gravis. We spoke to Murat Kalayoglu, president and CEO of Cartesian, about its RNA-engineered cell therapies, how they work and how the company is pushing the use of cell therapies beyond cancer.

Daniel Levine: Murat, thanks for joining us.

Murat Kalayoglu: Thank you.

Daniel Levine: We’re going to talk about mRNA cell therapy and the potential for this therapeutic approach to treat conditions beyond cancer. I thought it might be useful to begin with a little background, starting with CAR T cell therapies, as we know them today. This has been an important new area for cancer care. How do these therapies work and how are they generally made today?

Murat Kalayoglu: So, CAR T cells are, in essence, a type of engineered cell therapy, whereby T cells are taken either from the patient or, more recently, from healthy donors and engineered outside the body, ex vivo, usually with DNA that translates a protein that is chimeric—chimeric in the sense that half of it is outside the cell and binds to its target antigen, often one that is a protein that’s expressed by cancer cells, and the other half is inside the cell, which upon the outside portion binding, helps activate the cell to go and do its job, which is often to kill that cell. It’s a very powerful technology that has shown amazing clinical benefit in an array of different liquid tumors, in particular, and less effective in solid tumors today. An area obviously of a lot of activity just given the clinical benefit to date.

Daniel Levine: I suspect listeners have heard a lot about mRNA these days with the COVID-19 vaccines, but perhaps you can explain what mRNA is and what it is does.

Murat Kalayoglu: In essence, RNA is the intermediate step between DNA, which is the genetic code, and the protein, which is the functional part that makes up the machinery of life. Cells often take the DNA, which is in the nucleus, and generate a template from it, the RNA, before they make the actual protein. So, the DNA to RNA and then the RNA to protein sequence is preserved throughout life. If you want to modify the cell at the DNA level, you’re making a permanent change to that cell, such that when that cell divides, the daughter cell that’s modified at the DNA level will look identical to the parent cell. When you modify the cell at the RNA level, however in essence what you’re doing is ensuring that when that cell divides that the daughter cell has about half the amount of protein making capability compared to the parent cell. So, you’re not making an irreversible change with RNA as you are with DNA, you’re making a time controlled change by introducing RNA instead of DNA. It’s one of the key differences between engineering cells at the DNA level versus the RNA level.

Daniel Levine: Cartesian has a platform technology that you call RNA Armory to engineer cells. What are you able to do with the platform and how does it work?

Murat Kalayoglu: The RNA Armory is our way of engineering cells with RNA. It’s, in essence, a cell based combination therapy platform. We use the cell as both the factory for producing as well as the vehicle for delivering a combination of RNA therapeutics right to the site of disease where these RNA therapeutics can work in tandem and can be selected rationally in order to exert synergistic benefits towards the disease. It’s an opportunity to leverage the capacity of the cell to produce proteins by modifying them and programming them at the RNA level, outside the body, and then infusing them such that these engineered cells are able to find their way to the site of disease and then deliver their cargo over an extended period of time.

Daniel Levine: How do Cartesian’s cell therapies differ from what people might normally think of today?

Murat Kalayoglu: The conventional way of doing cell therapy is to engineer the cell at the DNA level. So, 98 percent of what you’ll see out there in terms of cell therapy are cells that are engineered at the DNA level. As you can surmise from the earlier discussion, you are making an irreversible change such that when you modify the cell outside the body and introduce it into the body and then the cell encounters this target antigen and begins to proliferate. Then, every daughter cell looks identical to the parent cell and that creates some problems for the treatment, in particular, around toxicity, because you lose control over the cell, and the cell will begin to proliferate out of control. Often these types of therapies are given at sub-therapeutic doses and are expected to proliferate into a therapeutic window and then stay at the therapeutic window. The cell doesn’t know how to do that and it will continue to proliferate and often cross a toxicity threshold, which is why you get the kinds of toxicities that are synonymous with conventional cell therapies. For example, for CAR T cells: cytokine release syndrome, neurotoxicity, increased risk of infection, long-term risks of transformation, or the cell actually becoming a cancerous cell or causing long-term immunogenicity. While these risks are acceptable when treating patients with the most advanced cancers, often they’re outside of oncology, or even frontline oncology, and for patients with newly diagnosed cancers that have other treatment options these types of toxicities are very limiting and have historically prevented cell therapy from extending beyond oncology. If you do want to go beyond oncology with cell therapy, you have to have a different approach. Our approach is to use RNA instead of DNA, where we make time control changes, and confer upon the cell drug-like properties and pharmacokinetics that allow us to be able to control the exposure. The enhanced safety gives us the ability to move into frontline cancers with cell therapy, as well as beyond oncology, in our case, in autoimmune disease and respiratory disease.

Daniel Levine: In making the case for this type of approach, using RNA to engineer cell therapy, beyond the safety advantages what would you say the advantages are?

Murat Kalayoglu: There’s a number of other advantages. One that immediately comes to mind is the cost of manufacturing is significantly less relative to working with DNA. There’s also indirect cost benefits if you don’t have to manage these toxicities. You don’t have to monitor patients for an extended period of time, over a decade, because the risk of transformation or having these cells turn into a cancer because you’re not modifying them at the genetic level. There’s other benefits. Often with conventional DNA-based therapies you have cargo limits in terms of the number of new molecules that you can introduce at the level of the DNA vector, that really doesn’t exist when you work with RNA. There’s a few others. First and foremost, the safety benefits are significant.

Daniel Levine: You have multiple clinical programs in your pipeline targeting indications that include cancer, autoimmune disease, and respiratory illness. I take it that what these all have in common is that you’re using the cell therapy to modulate the immune system. Is that correct?

Murat Kalayoglu: We’re targeting three disease categories with our clinical programs. We have three assets in clinical development, and three in preclinical that’ll likely matriculate into the clinic in the near term. The disease categories that we’re going after are in autoimmune, in frontline oncology, and then in respiratory diseases. The kinds of therapies that we’re developing within these disease categories are each of them addressing a fundamental key driver in the pathogenesis of each of these diseases. So, from that perspective, yes, we’re in essence modulating the immune system and the immune response to the disease. It’s hard to make generalizations given the different nature of each of these diseases and our approach to each of these diseases, but I think at a high level the way you phrased it is appropriate.

Daniel Levine: Let’s take a deeper dive into the programs. The most advanced program is Descartes-11 which is in development for multiple myeloma. What is multiple myeloma?

Murat Kalayoglu: Multiple myeloma is a disease of a particular type of cell, called a plasma cell, which resides in the bone marrow. So, you can think of it as a disease of the bone marrow. These types of cells, the plasma cells, are essential cells that are producing the antibodies that fight infection. In the case of multiple myeloma, some fraction of these cells undergo a series of mutations that transforms them into cancerous cells. As these cells proliferate in the bone marrow, they occupy space within the bone marrow that is essential for the normal functioning of the bone marrow. Often the disease manifests itself clinically as a reduction in that space within the bone marrow. As you crowd out the other essential cells in the bone marrow, the clinical manifestations of this disease, such as bone fractures, the inability to generate new blood cells, anemia, hypercalcemia, and all sorts of other manifestations of this disease that ultimately begin and end at the level of the bone marrow. It’s really a disease of the plasma cells and bone marrow.

Daniel Levine: There are a number of treatment options available today for multiple myeloma. What’s the prognosis for patients with the condition?

Murat Kalayoglu: Historical data, which is outdated now, usually speaks to about 50 percent of patients surviving for about five years. With the advent of new immunomodulatory therapies those data are outdated and patients are living longer and longer. The one exception is a fraction of patients that have what is called high risk multiple myeloma because they have high risk genetic characteristics. This fraction of patients comprises about 15 percent of the population. The kinds of treatment advances happening in the other 85 percent of the population of patients with myeloma haven’t been seen in this group to the same extent. This is an area that we’re very interested in. Our frontline myeloma program is actually targeting this group of patients to clear up any potential residual disease that is left after these patients have undergone their initial induction therapy.

Daniel Levine: What exactly is Descartes-11, and how is it prepared and delivered?

Murat Kalayoglu: Descartes-11 is an autologous, or personalized, CAR T therapy that targets an antigen called B cell maturation antigen, BCMA. It’s one of the key antigens or key proteins that can be targeted effectively in myeloma. It’s a relatively recently identified such protein. It’s just a terrific protein to target because it’s expressed exclusively in plasma cells, which is the type of cell that myeloma is derived from and really not expressed anywhere else. So, it’s a great protein to target because if you can eliminate cells that have a high level of expression of B cell maturation antigen, as these myeloma cancerous cells do, then you’re, in essence, killing the myeloma cell population. Our approach is to do this with our CAR T cells that are engineered with RNA instead of DNA. Given the fact that they’re engineered with RNA, the hope and the expectation, and now the data we’re seeing, certainly shows that they’re quite safe. We don’t see the cytokine release syndrome and neurotoxicity or increased risk of infection, et cetera. In fact, we don’t see any product related adverse events that you would normally expect with the standard CAR Ts that are modified at the DNA level in a conventional manner. The other benefit of our approach is that we don’t need to use a different therapy to create space for the cells to proliferate into. If you recall, the conventional DNA engineered CAR T are often administered along with, what’s called, lymphodepleting chemotherapy. This is toxic therapy that is designed to eliminate a lot of healthy cells that could block the potential proliferation of your CAR T product. If you’re administering a larger numbers of cells, as we are, and doing it repetitively you don’t really need this lymphodepleting therapy. Our study that is currently enrolling is not using any lymphodepleting chemotherapy, which is another safety feature of this type of approach. This is so important in a frontline setting. You want to minimize the amount of toxicity when you’re trying to clear residual disease in patients who were only recently diagnosed.

Daniel Levine: What’s known about the therapy from studies done to date?

Murat Kalayoglu: To date, we have completed a number of safety studies in patients with more advanced cancer and found our treatment to be sufficiently safe to be able to justify their use in a clinical trial in a frontline setting in patients with high-risk, newly diagnosed, multiple myeloma. That study is currently enrolling.

Daniel Levine: You have a second therapy in development Decartes-8, which is for the rare autoimmune condition generalized myasthenia gravis. What is that condition and how is it treated today?

Murat Kalayoglu: Myasthenia is a classic autoimmune disease in that an antibody produced by, again, a plasma cell ends up attacking the body itself in a way that is deleterious to health. As with most auto-antibody driven autoimmune diseases, myasthenia has as its source, this long-lived plasma cell that resides in the bone marrow that is an aberrant clone which is producing an autoantibody. In the case of myasthenia, this autoantibody is attacking the neuromuscular junction, which is the junction at the level of the muscle and the nerve that allows appropriate communication and muscle function. These patients often get very tired and lose overall function, often at first, around the eyes and have a difficult time keeping their eyelids open, but then over time, the disease can often progress into a more generalized form. Hence the term generalized myasthenia gravis that affects the larger muscle groups and, at its worst, affects the overall health and wellbeing of patients with this disease. Before the advent of steroid treatments and other immunosuppressant therapy, about a third of patients actually ended up succumbing to their disease and dying from myasthenia. These days patients are managed relatively effectively with these immunosuppressive therapies. Unfortunately, they have to take them for an extended period of time, and these are toxic therapies. So, there’s a great need to develop new therapies in order to get to the root cause of this disease. In our opinion, our hypothesis is that the source of this disease lies in the plasma cell that is generating these aberrant autoantibodies that are then going and attacking the neuromuscular junction.

Daniel Levine: What is the cell therapy you’re developing here and how does it work?

Murat Kalayoglu: Decartes-08 is similar to Decartes-11, in that it also targets the B-cell maturation antigen that is ubiquitously present at low levels in the long-lived plasma cells that are producing these autoantibodies. It stands to reason that if you can target this cell type with an anti BCMA CAR T therapy, as we’re developing here, you could change the trajectory of disease and the course of disease for these patients.

Daniel Levine: Finally, I’d like to ask you about Decartes-30, your experimental therapy for acute respiratory distress syndrome, a potentially deadly condition that can result from pneumonia, sepsis, and COVID-19. What is Decartes-30, and how does that work?

Murat Kalayoglu: Decartes-30 is our second generation therapy. We talked about our first generation therapies where we’re engineering one RNA into our T cell products in the form of Decartes-11 and Decartes-8 for frontline myeloma and for myasthenia. Our second generation program where we’re engineering two different proteins directly into a cell is represented by Descartes-30. Descartes-30 is an allogeneic therapy, where we’re engineering, not T cells that are personalized and autologous, but rather mesenchymal stem cells that are allogeneic and are derived from a healthy donor instead of from the patient himself or herself. These MSCs are engineered outside the body with a combination of RNA therapeutics that work together synergistically to degrade a key driver in the pathogenesis of not just acute respiratory distress syndrome, but a whole slew of other diseases including autoimmune diseases and cardiovascular diseases. This key driver is called a neutrophil extracellular trap—a net. Think of nets as, in essence, these sticky webs of DNA that are studded with inflammatory proteins that are expulsed by neutrophils as they attempt to control acute inflammation. The problem is that these nets themselves end up serving as a nexus of inflammation and often block alveoli to cause respiratory distress or the microvasculature to cause immune thrombi and clots. It stands to reason that if you can degrade nets, you could have a meaningful clinical benefit in ARDS and some of these other diseases. So, Descartes-30 is our attempt to do that. It’s engineering these MSCs with DNAases that are very powerful at degrading nets. Then this engineered MSC therapy is administered intravenously, it travels and targets the lung, which is where ARDS is happening, and there it’s able to deliver its cargo and degrade nets. That is the hope and expectation. That study, as with our other studies, is currently in early stage clinical trials to test out this hypothesis.

Daniel Levine: As you look at other potential indications, how broadly do you think you can apply this approach?

Murat Kalayoglu: The approach for delivering an anti-net therapy to other diseases, I think, can be applied very broadly. In other words, this same type of cell therapy, if it’s found to be safe and potentially effective in ARDS, then we can potentially apply it to other diseases like autoimmune diseases, other respiratory diseases, and perhaps in cardiovascular diseases.

Daniel Levine: Speaking more broadly about your platform technology are you looking at indications that reach beyond modulating the immune system? Is there a broader potential for programming cells with mRNA?

Murat Kalayoglu: More broadly, we think that the RNA platform is very versatile and extensible. The overarching goal and vision here is to use, in essence, the cell as a very versatile factory and vehicle for delivering to virtually any tissue, any combination of therapy. You can envision a combination therapy delivered to cardiovascular diseases, to diseases of the nervous system, you can think about its use in even dermatology, and the list goes on. We certainly believe that this type of platform technology has the potential to be revolutionary in delivering combination therapies. The drug development field, in general, has recognized the importance of combining therapies because often diseases are very complex and are difficult to treat with a single agent. The ability to combine your therapies into a single product from the very beginning, the design, and then use that approach to deliver, in a very targeted way, that combination right to the site of disease, we think is going to be revolutionary.

Daniel Levine: Murat Kalayoglu, president and CEO of Cartesian Therapeutics. Murat thanks so much for your time today.