Possibilities of CRISPR Technology

Podcast Transcript

Dale Shepard, MD, PhD: Cancer Advances, a Cleveland Clinic podcast for medical professionals, exploring the latest innovative research and clinical advances in the field of oncology. Thank you for joining us for another episode of Cancer Advances. I'm your host, Dr. Dale Shepard, a medical oncologist here at Cleveland Clinic directing the Taussig Early Cancer Therapeutics program and co-directing the Cleveland Clinic Sarcoma program.

Today I'm happy to be joined by Dr. Faiz Anwer, a hematologist here at Cleveland Clinic. He has been a guest on this podcast in the past to discuss the CAR T-cell therapy for patients with multiple myeloma. That episode is still available for you to listen to. He's here today to talk about CRISPR technology, so welcome back.

Faiz Anwer, MD: Well, thank you, Dr. Shepard. This is a pleasure to come back and speak with you, and through this platform, speak with the people who listen to us.

Dale Shepard, MD, PhD: Absolutely. So, remind us of a little bit about what your role is here at Cleveland Clinic. What do you do?

Faiz Anwer, MD: I'm a hematologist, working at the Taussig Cancer Center. I am, at this point, focusing on the treatment of multiple myeloma, which is a type of blood cancer. And I am also lead on the bone marrow transplant and stem cell transplant and CAR T-cell therapy for multiple myeloma indication. We are a group of seven physicians who specialize in and manage patients with myeloma. And four of us are also doing stem cell transplant and CAR T for multiple myeloma indication.

Dale Shepard, MD, PhD: Excellent. Well, today we're going to talk about something called CRISPR. And so again, we may be having people listen in from lots of different backgrounds. What exactly is CRISPR?

Faiz Anwer, MD: CRISPR is essentially a gene-editing technology. We have many other gene-editing technology, but CRISPR is unique in the sense that it has given us the ability to identify a piece of a target gene which needs to be modified or edited. And the CRISPR-Cas9 system is linked with an RNA, which can go to the targeted DNA, and that's where the Cas9 enzyme protein can cleave the DNA. And after cleavage, we can either remove that gene, or we can infuse another portion of the genetic material into that area, and that will change how the cells will behave differently.

Dale Shepard, MD, PhD: And so first off, you have to have an area in a gene that you know that you want to remove. If you're going to take out a gene, is there a particular limit to how much of a gene you can modify with this technology?

Faiz Anwer, MD: So, I want to step back before we go into the particular mechanism of CRISPR, how it works. In the human body, we have 23 pairs of chromosomes. That is the packets of genetic material. And in the 23 pairs of chromosomes, we have about 20,000 genes in the human body. And with the help of this technology, we can precisely target an area of interest. It could be in any chromosome, and that's where the CRISPR-Cas9 system can be used to edit that area.

And at this point, technology is evolving and getting better. To my knowledge, the potential for this technology is limitless. And we may be able to use multiple gene edits in a particular scenario where we are using multiple RNA to target multiple DNA material inside the cell and change the cells.

Dale Shepard, MD, PhD: And despite the fact there are so many genes, there's enough difference that if you try to utilize this technology, you can, for the most part, get specificity.

Faiz Anwer, MD: For most parts it gets specificity, but that's where the concern is, that we need to be carefully monitor that, that we don't want to do the gene edits in an area where we don't want it to work. So that's where one of the concerns could be that the off-target effect of this technology can be there.

Dale Shepard, MD, PhD: And as a guy who doesn't do CRISPR, I have a ridiculous question. How do you know? How do you know if you have an off target edit?

Faiz Anwer, MD: Well, there are genetic techniques where you can study after treating a cell, and you can identify if you have done damage to an off-target area. Or if you're studying cells, you may see change in their behavior. You may see a change in their cell's protein expression because these genes have a function. They make proteins. And so, by changing the protein function, the protein size, or protein expression, you will identify areas where you have done unnecessary damage.

Dale Shepard, MD, PhD: And I guess again, just for perspective, if there's an error in an off-target part of the DNA, can that get fixed?

Faiz Anwer, MD: I will say if you find that your particular CRISPR-Cas9 system is causing off-target effect, you need to probably use another RNA where it will be more precise, and only cut at the spot where the cut was intended.

Dale Shepard, MD, PhD: Excellent. So, when we think about this technology, it gives us a little bit of a background on how that's been utilized for treating cancer so far.

Faiz Anwer, MD: So, this is very timely because we just initiated a phase 1 clinical trial with a pharmaceutical company. It's a multi-institute study where we're using a cancer-fighting T cell, and T cells are immune cells. Their main job is to fight against infections as well as cancers. And through this CRISPR technology, the allogeneic cells which came from a healthy donor were modified. Those T cells are now able to find and attack and kill cancer cells. And we are using it for the treatment of multiple myeloma.

In this particular case, this cell is modified in four different ways where they have removed a T-cell receptor and inserted a new receptor, which can find a cancer target called the BCMA protein. And on the other end, through this technology, they have modified the cell, so it does not attack the patient's body, so it does not cause graft versus host disease.

And they have also modified the cell in a way that the patient's host immune system does not attack and kill the donor cell. So, it is protected from the rejection of these cells. So, through these edits, now, these cells can stay in the body and potentially be very effective in eradicating cancer from the body.

Dale Shepard, MD, PhD: So just from an educational standpoint sort of, somebody starts reading something about CRISPR and these technologies. So, you just described sort of adding something and taking away things, knock-in, knockout as sort of terms?

Faiz Anwer, MD: Right. So, the knock-in will be once CRISPR-Cas system breaks the DNA. You can insert a new piece of DNA material, and that new piece of DNA material will be responsible for making different proteins and newer proteins. And knockout will be if there's a defective gene, and you want to remove it. And that's where you use the term knockout, that the piece of DNA material can be removed from the patient's genome.

Dale Shepard, MD, PhD: Give us some examples of how this has been successfully used so far. So, you mentioned we're starting an early-phase trial with multiple myeloma with this, what are some of these successes so far?

Faiz Anwer, MD: So, when we are recording this, New England Journal of Medicine came out with a publication, where in a study they used autologous stem cell from sickle cell patients and modified it and infused back into the patient body, so this is like doing an autologous stem cell transplant. And they have done that in three patients, who were in their early twenties and had severe sickle cell disease and found significant improvement in their disease by doing that.

Dale Shepard, MD, PhD: So, it's impressive.

Faiz Anwer, MD: So, this is an example and a window into the future, how we are going to see these types of therapies being used in humans.

Dale Shepard, MD, PhD: And when we think about this as a technology, previous trials, have there been some notable failures that have helped guide these current studies and things? Have there been things we've learned along the way from efforts to do this that have not been successful?

Faiz Anwer, MD: We have seen gene technology have failed in the past. We have seen these types of gene-editing technologies have led to unnecessary edits and caused cancers or other diseases or other dysfunction in the patient body. So, we need to be careful as we are developing these techniques and using them in humans. So that will be an area of concern.

It is possible that once you are using any gene-editing technology, it can go to the germline and can change sperms or ova. And then these genetic changes can become transmittable to the next generations. So that can enter into the human race in the future. And similar concern can exist for if you're making changes in animal models or if you're making changes in crops. That can be a concern.

Dale Shepard, MD, PhD: So, if we think about it, we're in an era where there's lots and lots of new ways to treat. We have previously talked about CAR T therapies, for instance. What are some examples of when this CRISPR technology utilizing gene editing as a treatment might have advantages or disadvantages over some of these cellular therapies or sort of the older stem cell transplants, things like that? Why would one choose this over the others? What are we trying to overcome?

Faiz Anwer, MD: This is a great question. So, the promise with the technology is now we can use our own immune system and use it as a targeted therapy against cancer. We can also develop universal cell products, which are off-the-shelf, can be potentially available the moment a patient needs it. These therapies are available to use, as compared to the current technology where we have to collect patient's own cells, and there's a delay of four to six weeks to generate their CAR T cells, and then they need to be infused back into the patient body. We can also target tumor microenvironment. We can also target cancer directly. So, these are the advantages of this current technology.

Dale Shepard, MD, PhD: And then, I guess, you also mentioned things like minimizing graft versus host.

Faiz Anwer, MD: Right. So, there are a lot of implications that we can now use stem cell and modify them, and the therapy can be safer without causing graft versus host disease. And it is possible for some diseases, now, that we don't have to rely on the allogeneic stem cells, where the stem cells come from a healthy donor.

Dale Shepard, MD, PhD: When we think about sickle cell, as an example, we think about multiple myeloma, as an example, a lot of CAR T therapies, a lot of the cellular therapies have been more hematologic malignancies. What's the current status, the future for utilizing CRISPR technologies with solid tumors?

Faiz Anwer, MD: There are multiple possibilities. We are just starting with this technology. Many genetic disorders such as blindness, cystic fibrosis, liver conditions, viral infections, bacterial infections, the challenge of overcoming bacterial or viral antibiotic and antiviral drug resistance issues. Similarly, so far it appears that heme malignancies, we are making more advances by using these adoptive-cell therapies and genetically engineered cell therapies.

But at the same time, we're now seeing a lot of those therapies are being developed against solid tumors, ovarian cancer, lung cancer, liver cancer. There are multiple clinical trials which look at the early phases of drug development and how to best treat by using these cellular therapies.

Dale Shepard, MD, PhD: Particularly things like CAR T therapies, one of the big barriers is the heterogeneity in solid tumors compared to most of the hematologic malignancies. Is that something, that by being able to edit genes and add receptors or some sort of specificity to the therapy, we'll be able to be maybe a little bit more successful in solid tumors?

Faiz Anwer, MD: So, I think with this technology we can actually attack cancer using three different uses of this technology. We can make better products with more specificity. We can change the microenvironment such as checkpoint inhibitors, which are being inhibited. Cells are inhibited through the checkpoint inhibitors. And we can also highlight the cancer cells by expressing new targets and new proteins inside the cancer as well. So, it is possible to use this technology in different ways to target cancer.

Dale Shepard, MD, PhD: What do you think are the biggest barriers right now to developing these treatments?

Faiz Anwer, MD:So, a lot of these treatments are still very early in the development phases. Off-target effects will be my concern. Undesirable mutations that can lead to serious consequences such as leukemias will be a concern. And we need to be very careful about if the germline mutations are happening and how that will be impacting the future generation. We need to be careful if this technology is used in animals and in crops, and ultimately the gene pool or the mutations will be released in the environment. So, we need to be careful about that.

Dale Shepard, MD, PhD:When we think of a patient getting one of these treatments, what sort of toxicities? We've talked about the sort of genetic changes that could occur, but patients that get these kinds of therapies, what would the anticipated toxicity be?

Faiz Anwer, MD: So, I can talk about the T-cell based therapies in patients who receive T cell because these are millions of cells, which are capable of finding and killing cancer cell quickly. So that can lead to a certain set of conditions such as cytokine release syndrome where these infection-fighting cells become excited, releasing a lot of proteins. And the cancer cells die and release a lot of proteins, so that can make patients sicker very quickly.

And those patients may have a symptom to suggest they may have a fever, trouble breathing, or blood pressure issues. Because we're using immune system to fight against cancer, we may see some immunosuppression where a patient's body is not able to fight against bacterial and viral infections. So, we need to be careful about that.

Dale Shepard, MD, PhD: And so really, the toxicity is more based on what gets modified by the CRISPR technology, like a T cell rather than any changes that have happened?

Faiz Anwer, MD: That is correct. So I think the other challenge may be there are some diseases, where instead of making changes in the cell outside the body, you want to inject this edited gene into the patient body such as if person has a liver disorder or a lung condition where you cannot take the tissue out and fix it and put back into the body. So, if you're injecting a CRISPR-Cas9-based therapy into the patient body, that can lead to some unique toxicities. And we are still learning from the early-phase clinical trials.

Dale Shepard, MD, PhD: From the beginning really, the DNA cutting part that Cas9 part has been pretty consistent, right? And then you mentioned before about changing the specificity with changes in RNA. Are there changes that are being studied in terms of either of those kinds of mechanisms that might lead to a new plateau of efficacy or benefit? Are there better ways to modify either of those to make for better treatments?

Faiz Anwer, MD: So, I gave the reference of a study, which was just published, and it used the CRISPR-Cas9 system, and they studied multiple RNA molecules, which were used as a guide to their DNA focus where the change was ultimately made. And through that constant study and testing of different RNA models, they were able to make this therapy more effective. And for each unique disease and its indication, that's where most of the studies will be done, that how to make use of this therapy and make it safer and more effective and precise. And the cost should come down.

Dale Shepard, MD, PhD: Well, this is certainly something that it's good to see is coming into sort of clinical trial, as you mentioned, in sickle cell actually showing benefit. And good luck with your study, and I appreciate all your insights today.

Faiz Anwer, MD: Well, thank you so much. It was a pleasure talking to you.

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