Oct 25, 2019
Ryan W. Bonvillain, PhD is the Senior Manager for Tissue Engineering, Research Regenerative Medicine at United Therapeutics Corporation. Kelly Guthrie, MS is the Associate Director BioScaffolds, Regenerative Medicine at United Therapeutics Corporation. In this episode Ryan and Kelly discuss work that UT is doing in the realm of regenerative medicine for the purpose of increasing the number of lungs that are available for organ transplant for patients who need them.
My name is Ryan Bonvillain. I'm a senior manager for tissue engineering research at United Therapeutics. I was trained in pulmonary biology as a PhD student. I went on to do a postdoctoral fellowship in pulmonary tissue engineering, which is actually a very similar work to the work that regenerative medicine at United Therapeutics is working on now. When the regenerative medicine department at United Therapeutics was formed, and they built a laboratory, I was fortunate enough to apply for a job and be selected for the position, and I've been here with regenerative medicine since 2014, which was essentially the inception of the lab. So, I've been around since the beginning of the efforts at United Therapeutics.
My name is Kelly Guthrie, and I'm the associate director for bioscaffolds here in the regenerative medicine lab. I've been in regenerative medicine, although not involved with lungs, since 2005, and my background is not lung specialized, but I have focused on improving outcomes for patients through novel therapeutic approaches, and I've been really lucky to be part of the team here since 2015. My group works to decellularize (or remove the cells from porcine lungs) to form the basis of a regenerative lung.
Today, we'd like to tell you about the work that United Therapeutics is doing in the realm of regenerative medicine for the purpose of increasing the number of lungs that are available for organ transplant for patients who need them. There is a tremendous unmet need for lung transplants. The number of people who go on to waitlists for organs is increasing every year, but the number of donated organs has largely remained stagnant for the last 15 years or so. So, there's this ever increasing disparity between what's available and the number of patients who those therapies can go to. So, United Therapeutics is really interested in transplant, because it's currently the only cure, if you will, for pulmonary arterial hypertension. We have a handful of FDA-approved medicines on the market to treat pulmonary hypertension, but none of them are really cures.
So, in order to make these curative therapies more available to patients, United Therapeutics is really committed to figuring out ways to make more lungs, and either we do that through an approach like ours, which is regenerative medicine in which we are literally taking a tissue engineering approach where we are trying to make a lung in the laboratory that gets transplanted into patients or whether there's an alternative approach, for example, some other technologies that are in the works, like ex vivo lung perfusion (EVLP) in which lungs are reconditioned. If they don't meet the criteria for transplant, they are reconditioned, and then, several of them go on to meet the criteria for transplant. We also have at United Therapeutics a subsidiary company who is working on genetically modifying pigs to remove, what are called, xenoantigens. They are the parts of the parts of the porcine cells that are hyper-stimulatory to the human immune response. What they're trying to do is remove those genes from the pig's genome so that the pig tissues that are produced don't have those molecules that result in rejection of those organs.
So, here in regenerative medicine, if you think about creating a lung from the ground up, where do you have to start? You have to produce some structure onto which you can grow the lung. So, we start with pig lungs, and we treat them with a process called decellularization, and it's pretty much exactly like it sounds, where we are treating tissues with chemicals, mainly detergents and salts and antibiotics, et cetera, to remove all the living porcine material. What's left is just the structural protein component, what's known as the extracellular matrix. So, it's the framework that every organ and tissue in our bodies is made from, and we're essentially isolating that from the tissue.
We can then take that resulting scaffold, as we call it, and repopulate it with human cells. So, we're using the framework of a pig lung and re-populating it with human cells to generate what is, for all intents and purposes, a human tissue. We can do this because the proteins that are left in the porcine scaffold, the structural proteins that we talk about, are things that are very common, that most people hear of, things like collagen and elastin and fibronectin. And as it turns out, those molecules are what's known as genetically conserved, which means that the genes that produce those proteins in pigs are very similar to the genes that produce those proteins in humans. So, when the human cells are seeing the pig-derived, extracellular matrix proteins, they really can't tell the difference between pig and human protein. So, the human cells will attach to the porcine scaffold and set up a niche or a micro-environment and start to live in that structure. So, by very carefully putting cells throughout the structure and giving it the appropriate biochemical and mechanical cues, we can start to build the tissue from a molecular and cellular level, and then, hopefully, extrapolate that out to building the entire organ, such that the cells we put down are producing functions that give us the overall organ function.
So, for example, in lungs, what we really need to achieve is a gas exchange barrier where we can perfuse blood through the vasculature for the organ, and we can put air into the airway and facilitate a transfer of oxygen from the air into the blood to be carried to the rest of the body and also to take waste products from the blood, like carbon dioxide, for example, and then deliver that across the blood into the air to be expired by a patient. So, the classic definition of gas exchange is what we're trying to achieve in the lung. The way that we're doing this, so, we have a big group of people that are in excess of 65 people, all dedicated to working on this project, and we've sort of subdivided to put the best people on tackling specific issues.
So, for example, Kelly leads the scaffold production group. So, their job is to make lung scaffolds and then assess them and make sure that they're of a quality that's going to give us the best possible downstream outcome. My team focuses on the recellularization efforts with several colleagues, and then, we have people who are focused on growing human cells and expanding them or isolating human cells from tissue to use for this process. So, we're very early R&D in that we're trying to figure out, what is this process going to look like for a clinical manufacturing process in a facility that can make this product for clinical use.
Yeah. So, we routinely decellularize porcine scaffolds on a weekly basis. So, the process started several years ago with a decellularization process that required 14 days to perform. In the last couple of years, we've been able to reduce that to a 27-hour process. So, that allows us to begin to scale a process that, before, was just a nice science experiment, but it is becoming a much more manufacturable entity in the manner that we're doing it. Decellularization itself has been around in other product forms for a while. So, small intestinal submucosa or some of the vascular patches that are utilized are made out of ECM, but no one has been performing full-scale organ decellularization in a commercial way to date. So, we are working on our process and working on facilities in order to be able to produce a decellularized organ in a manner that is able to be regulated and to meet regulatory requirements of the FDA. What we are doing here is very different from a small molecule type of generation. It is not without its challenges. We don't have years of history of how to develop this type of product.
So, almost everything about what we're doing here is novel in some way. I mean, cells have existed and decellularization has existed and tissue engineering and regenerative medicine have been coined since the '90s or before, but really being able to take these basic foundational sciences and put them together into a functional organ is a tall order. What makes it both interesting and worthy is the fact that it has the potential to improve outcomes for patients, and I think that is the main goal. We're not doing a science experiment, although we have to do experiments to achieve our goal. We're really working toward having a functional lung and contributing that to the field of study and to patients.
What we know from the history of lung transplantation, which is many, many decades now, is that in the beginning of the prognosis, if you receive a lung transplant, was very, very, very poor. Now, we're on average of about six years post-transplant is the expected survival for a double lung recipient. Now, of course there are extenuating circumstances that can make that post-transplant survival be really short, but there are several people who will live 15 or 20 or 25 years with a lung transplant and be relatively healthy. So, it all really depends on the situation and the context of a person's disease. What's true is what we're trying to do here is to, first and foremost, is increase the number of transplants that are available to patients. If we do that, we are, by default, saving lives, because people who are on a waitlist for more than several months, let's say, run an extreme risk of dying. So, if we can just make more organs available and keep people alive longer, perhaps there is a potential to receive some other kind of therapy of a more traditional transplant.
So, that's basically what's called a bridge to transplant idea where if we can give somebody back even five percent pulmonary function, we might improve their quality of life such that they do better on the transplant waitlist, and then, they can receive a better therapy. But what we really want to go after here is to create a lung that essentially belongs to the patient. So, we want to be able to, at the end of the day, take cells from the patient, expand them in culture in a laboratory, seed them into a scaffold, and create a piece of tissue made out of the patient's own cells. If we can do that, we give the patient back an organ that is theirs. We reduce the need for immunosuppression, because we're not giving them a foreign piece of tissue. We're giving them their own tissue back. I believe if we can achieve that, we will not only dramatically increase the post-transplant survival period, but we'll perhaps revolutionize the whole field of transplant by giving people autologous organs, which nobody has really been able to do so far.
It makes my heart beat a little bit faster just thinking about being able to say that and to offer that. The motivation from this mission comes from our leaders up and from the vision that Martine Rothblatt has toward meeting the need for an unlimited supply of organs. To offer that to patients is why we're here. It's a chance to provide the cure and to improve quality of life for people that don't have an endless trajectory. None of us do, but I think it offers a better outcome for them. I think what UT is offering is sort of a four-legged stool or platform from which to improve the lives of patients. So, whether it's from a reconditioned human lung or a genetically engineered lung or a 3D printed lung scaffold or a recellularized porcine scaffold, those are all moon shots toward achieving the goal. I think there's going to be a lot of learning in those realms that is going to lead to improved medicines from what is learned I this effort as well as an unlimited supply of organs.
From our perspective, the mission here is not complete until we get to that day. So, we can do the fanciest science. We can do the hottest topic in biomedical research, but until we are physically helping people, our job is not done. I think that everybody who works at United Therapeutics understands that. What I love about UT is that everybody's on board with the same mission, and we are all working very hard to get there every day.
My name is Kelly Guthrie, and I'm aware that I'm rare.
And my name is Ryan Bonvillain, and I'm aware that I'm rare.
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