From Research to Manufacturing to Treatment: A One-Stop CAR T Shop

When Carl H. June, MD, came to the University of Pennsylvania, his theory of manipulating chimeric antigen receptor T-cells remained in “dream” category for many. But with the theories in place, he began to attract a team who believed in that dream.

Don L. Siegel, PhD, MD, was one of the first meetings June had in 1999, when he arrived.

“He and I met to discuss how in an academic institution it could be possible to leverage our experience with conventional 20th-century hospital transfusion medicine facilities – notably an apheresis unit, a blood bank, and a hematopoietic progenitor laboratory – with a university’s research laboratories and Carl’s understanding of T-cells and his vision on how to alter them,” Siegel told Cell Therapy Next. “How could we actually create novel cell therapies from scratch, manufacture them to clinical grade standards, and administer them to patients?”

From a sketch on a pad of paper to one of the most robust programs in the country with multiple manufacturing areas and associated labs, Siegel and June worked in tandem while others followed their own passions to become part of the team.

“It was the situation of being in the right place at the right time,” Michael C. Milone, MD, PhD, told Cell Therapy Next. “I remember as a kid growing up reading the stories of Steve Rosenberg at the National Cancer Institute. They were in the back of my mind, so maybe chance fate prepared me.”

After finishing his clinical pathology residency and transfusion medicine fellowship with Siegel and with his PhD in immunology, Milone was looking for his next lab in 2002, just a few short years after June arrived at Penn.

“Within 6 months, I knew this was the right lab. Carl’s approach to the work he does is incredibly translational. People talk a lot about translational research, but he really does translational research,” Milone said. “You make things, you put them into patients. You learn the most you can from those patients. It’s an iterative cycle that really appealed to me.”

Specifically, Milone looked at the range of designs for CAR T-cells and proposed the one that would best serve the purpose of T-cell immunotherapy, leading Penn to CD19 and the currently approved CAR T therapies for acute lymphoblastic leukemia (ALL) and lymphoma.

“Not only was that an accomplishment in demonstrating that novel cell therapies are feasible to produce, but that they can actually work in a patient,” Siegel said.

In 2011, Saar I. Gill, MD, PhD, arrived at Penn as a clinically trained hematologist-oncologist with a PhD in tumor immunology.

“I moved to Penn, really because I had heard of June and his genetically engineered T-cell approach and I thought it was the most exciting thing I had heard for a long time in science,” Gill said. “People should work on what they’re passionate about and what I’m passionate about is finding cures. ... I wanted to go to Penn, and work with Carl June in order to accomplish something that achieves that effect.”

Day-to-Day Discoveries

After the approval of current CAR T therapies, the focus for Gill, Milone, Siegel and others at Penn are the next discoveries.

Gill’s current focus is “bringing the power of that technology to bear on acute myeloid leukemia (AML),” he said.

“As a physician-scientist, I treat patients with AML,” Gill said. “My work is a constant, almost daily physical and metaphorical joining between the lab and the clinic. I treat patients with AML, go back to the lab where I devise new and improved CAR T-cell approaches to AML. In the early days, it was just me. Then I had one tech and a couple of post-docs. Now, I run a research lab of 15 people.”

Gill and his team are on the cusp of treating patients with AML using anti-CD123 CAR T-cells spending years improving their system; they are looking into anti-CD33 CAR T-cells, which he hopes to get into clinical trials in 2019. Gill explained that the same approach taken with CD19 in ALL does not fit the AML model.

“I’ve always thought we can do better against AML if we use more potent immunotherapies, which is why we need CAR T-cells to improve on the current approaches with chemotherapy, antibodies, or antibody-drug conjugates,” Gill said. “There are normal, healthy cells that express AML antigens like CD33 or CD123, and these cells aren’t dispensable. Therefore, to target AML with potent immunotherapies such as CAR T-cells you need to think outside the box to make this whole process feasible. You need to develop an approach that’s going to give you a higher therapeutic index.”

Recently, Gill and his team published a paper in Cell that outlined using CRISPR to edit hemopoietic stem cells to remove from those cells the CD33 antigen and combine that with anti CD33-targeted CAR T-cells.

“That’s what I’m most excited about – developing potent therapies, being real sober and clear-eyed about what their toxicities may be and finding a rational approach that goes beyond simply hoping that it will be safe,” Gill said. “It actually ensures that there is a therapeutic index.”

Milone said that with the swell of interest in CAR T-cell therapy, “Right now, it is a great time to be exploring this.”

Currently, Milone’s lab is working to take CAR T-cell therapy outside of oncology, with the first foray into pemphigus vulgaris, an autoimmune skin disease. In this disease, Milone and his colleagues redirected the CAR T-cells to “kill autoreactive B lymphocytes through the specificity of the B-cell receptor.”

“We demonstrated that you could take a CAR T-cell and instead of killing all your B-cells, we target just the pathogenic ones. ... We are taking that same technology and reapplying it in a very focused way outside of oncology.”

When projects like this move past the preclinical roadblocks, it comes back to Siegel, who currently holds five titles at Penn, as he walks through his clinical, bench research, translational, cell manufacturing, and quality control labs.

“If it looks like something is feasible and looks like it could be used in humans, it comes to the product development lab,” Siegel said. “Once those conditions are worked up, the manufacturing lab here will engineer cells first from healthy donors and then from patient material to demonstrate that one can manufacture a product that meets specifications. Then our [investigational new drug application] team can go to the FDA for the required approvals that we need to open a trial. We have a dozen or two trials ongoing with CAR T and other forms of cellular therapy.”

After treatments are manufactured and administered to specific patients, Siegel said many of those patients take the opportunity to return to Penn to visit the manufacturing facilities.

“The patients come here to meet the people who actually made their cells,” Siegel said. “For our employees, it’s not like working for a pharmaceutical company where you are one part of a process that makes a gigantic vat of a drug that provides treatment for 20,000 people. Here, you are handed a bag of apheresis-derived cells from a patient and you’re the person literally hand-crafting a drug that will save another person’s life. And then that person comes back here to say hi and thanks.”

What the Future Holds

Ever on the cutting edge, these physician-scientists each predicted the next steps in CAR T-cell therapy. For Siegel, the next step may have started 4 years ago.

Carlos F. Barbas III, PhD, was a scientist at Scripps who developed antibody engineering technologies and the first clinically-applied gene editing methods. He was also a friend of Siegel’s.

“Carlos was diagnosed 4 years ago with medullary thyroid cancer (MTC), which is not the kind of thyroid cancer you want to get. There currently is no cure,” Siegel said. “Working with Milone and transfusion medicine fellow Vijay Bhoj, MD, PhD, we exploited the advanced state of the required technologies at our disposal and within 2.5 months, we identified an MTC target, made an antibody to it using the approach Carlos had taught me years earlier, and were able to create CAR T-cells that killed that tumor in a dish.”

Siegel was pursuing FDA approval to manufacture these CARs for Barbas just as his friend passed away. But the research continued, and it is anticipated that those CARs will enter clinical trials shortly.

“From a research point of view, I’m interested in expanding the repertoire of CARs by identifying novel targets and developing antibodies that recognize them,” Siegel said.

Milone pointed to his B-cell maturation antigen (BCMA)-directed CAR T for multiple myeloma as one of the next approved CARs for blood cell-derived cancers he hopes to achieve, but said, “The biggest holy grail is how do we get this to work in solid tumors.”

Siegel agreed: “The most success has been in treating liquid tumors because they have represented the low-hanging fruit. They are not large masses of cells that need to be permeated by T-cells.”

Concurrently, Penn and others are working on an ‘off-the-shelf’ CAR T-cell manufacturing process as well as making current processes more efficient.

“Ultimately someday – and that day may be in only a few years – we will collect cells from healthy donors and turn them into so-called ‘universal CAR T-cells’ able to treat a number of different patients all from the same manufacturing lot,” Siegel said.

“To me, the future is going to be figuring out how to engineer these cells more efficiently, maybe even getting away from viral vectors for introducing chimeric receptors,” Milone said. “That could improve the function of these therapies and address the relatively high cost of making these therapies.”

Lastly, Siegel was excited about the prospect of controlling the CARs.

“Right now, you give them to someone and you hope they work, and you hope they last, and you hope they don’t do anything you don’t want them to do,” Siegel said. “What would be ideal is to be able to turn them on and off at will by giving the patient some innocuous drug that modulates their activity. Some have referred to these CAR Ts as ‘switch CARs.’”

Gill remains focused on AML.

“What I love about my job is I get to be involved in the care of AML patients almost every step of the way. I get to diagnose them, treat them, and see them through standard of care, which today is a bone marrow transplant, as well as experimental therapies,” Gill said. “What I would love to achieve is bringing forth a new treatment modality, one that has been proven in a similar disease, but also to find a way to deliver this therapy in a tolerable fashion. What I think is really important and what I want to spend my career on is ... to at least show we can cure some patients with this approach that wouldn’t otherwise receive a cure.”

Truly Translational Work

That hope of the cure is the basis for the translational work done at Penn.

“The thing that’s been most fulfilling for me in a big picture sense has been translational research,” Gill said. “Doing something in your lab and seeing it in patients is incredible. ... When it comes to physician-scientists in academia, that only happens in select institutions. ... You have to look for a place with enough likeminded individuals and enough resources to make your dreams a reality where you can actually get your discoveries into patients; I wish that experience on anyone who is even remotely interested in translational research.”

Milone relayed a conversation he had with recent Nobel Prize winner, James P. Allison, PhD, in which Allison said the clinical trials in which he was involved did not glean enough from the patients they treated, something June insists upon with clinical trials.

“That’s an essential underpinning of the work we do here. That’s how we are going to advance these therapies,” Milone said. “Every patient’s tumor is unique and these therapies are so complex. It’s hard to model it in a preclinical setting, ... but the reality is that humans are the real model. We have to do the trials carefully and safely, but also learn as much as we can from each patient we treat.”

And this focus, this consideration of each patient treated comes at a cost.

“To really do this type of translational research successfully, it requires a huge investment from the university,” Milone said. “This is really a convergence of both cell therapy and gene therapy. ... There really has been a wide investment in the periphery of our program that supports our program and is part of that ecosystem and that ecosystem is critical to our success.”

Siegel agreed: “This is an enormous enterprise. ... This is much more complex than a biotech company that produces novel therapies. It is a biotech operation within a university that directly interfaces with a health system and a physician practice.”

Penn took that risk and made those investments and now, its team does the same.

“You need to ask the big questions. That depends on personality and appetite for risk, but I think it’s what makes one’s career and endeavors worthwhile. Ask the big questions knowing that most of them you’re not going to be able to find the answer to but that the one time you do, it will be extremely fulfilling,” Gill said.

Confidence in Moving Forward

As Penn moves forward with the whole of CAR T-cell therapy research, Gill put nicely how the past few years of success has helped everyone.

“It wasn’t a given that this would work. Yet, it works. We are very confident that the platform works,” Gill said. “It gave us and everyone else in the field a huge boost of confidence. And that confidence translates to dollars that come from research grants, investments, and numerous investigations that power the whole enterprise. ... This gives us more and more impetus to do more and to show that this can be generalized well-beyond CD19 and B-cell malignancies.”

This impetus and taste of success, of a cure, motivates researchers and clinicians alike.

“There’s certainly more to come. By studying the limitations, by pushing the envelopes, we are learning where we need to make the tweaks or the major changes that will take us to the next level and more difficult to treat diseases,” Gill said. “I love seeing the fact that other centers achieve the same results we do. This means that our results are not a flash in the pan. It means they are reproducible. It means that they are real. ... That’s what matters the most to a scientist, to a physician. This is not a one-hit wonder. While competition is certainly a good thing, we are more similar than we are different. That’s actually a really good thing.” – by Katrina Altersitz

• References:
• Ellebrecht CT, et al. Science. 2016;doi:10.1126/science.aaf6756.
• Kim MY, et al. Cell. 2018;doi:10.1016/j.cell.2018.05.013.

Disclosures: Gill reports receiving research funding from Novartis and holding patents for CAR T-cells for AML including CART33 and CART123; Milone reports holding patents related to CAR T-cell technology including CTL019 and CART-BCMA that are licensed to Novartis and receiving royalties and research funding from Novartis as well as funding from Cabaletta Bio, for which he is a founder; Siegel reports holding patents related to CAR Ts and receiving funding from Tmunity.