Program: There's been a big CRISPR breakthrough. What does the future hold?

Norman Swan: Coming up here on the Health Report, do we need eight hours of sleep each night? A new study looks at how sleep duration differs across cultures, and suggests that eight hours a night might be a myth. But, Liv, you've been looking at a big development in the gene editing space, it's called CRISPR.

Olivia Willis: I have. So a lot of people probably first heard of CRISPR in 2020 which is when scientists who developed the gene editing technology, they were awarded the Nobel Prize, I think in chemistry. CRISPR is a pretty remarkable tool really. It allows scientists to target specific sections of our genetic code and edit our DNA and therefore potentially correct genetic mutations. 

Norman Swan: It's almost like Word for genes. 

Olivia Willis: That's right, that's right. And doctors have actually been using CRISPR therapies for a small number of genetic conditions for a couple of years. There was a CRISPR therapy approved for sickle cell anaemia in, I think, 2023, and there are several therapies in clinical trials. But last week it was revealed that, for the first time ever, scientists had actually developed and successfully delivered a personalised CRISPR treatment, so a therapy that was customised and created for a single patient, to a baby in the US with an extremely rare genetic disorder. So this little boy had something called CPS1 deficiency. It affects about one in 1.3 million babies, so very, very rare. And essentially the deficiency, it stops a person with it from producing an enzyme that is really important to liver function, and that then leads to dangerous levels of something called ammonia, which builds up in the blood.

Norman Swan: Not good for the baby, in fact it can be fatal.

Olivia Willis: That's right. And what causes this condition, in very, very simple terms, is that a letter in his DNA is wrong or not in the order that it should be. And so, as you're about to hear, the scientists in the US who are involved in this, they took a really novel approach to design a gene editing therapy for this boy. And to better understand it, I spoke with Professor Marco Herold from the Olivia Newton-John Cancer Research Institute. He's the CEO there, and also the head of a laboratory which focuses on CRISPR screening and editing. 

Marco Herold: In order to do this, they were trying to use a genetic engineering trick by exchanging this letter from its wrong into its correct version back. So we had the analogy here you have a book and there is one letter wrong, and you change this one letter from its basically erroneous letter into the normal letter again. And for that, they use the technique which is CRISPR and CRISPR base editing. CRISPR base editing is a second generation CRISPR tool which has been developed to do exactly this, to change a letter from one into the other.

Olivia Willis: And just breaking down this process, because it's obviously very complex. So thinking about firstly the CRISPR element, and then maybe we get to the base editing. So the CRISPR, I've heard it described almost as if the researchers are trying to send a letter in the mail to one house in a city. They put a postcode on it and inject it into the body, and it manages to find that particular house in this enormous city with millions and millions of houses. Can you just explain a little bit how it gets there?

Marco Herold: So the CRISPR is an enzyme, which is a CAS enzyme. And the CAS enzymes, they essentially are programmed by a second molecular piece, which is a little piece of RNA. So this essentially takes a CAS enzyme to the right address where the piece of RNA fits 100% onto that address. So it just searches until it's 100% fitting, and then it stops. And then the CRISPR enzyme, in its original form, will only cut the DNA like it's a molecular scissor, it cuts both strands. And mammalian (so meaning human) DNA or cells have sent a mechanism to repair this so the cell can survive, divide and so on. 

Now, base editing is an advanced addition, so to say, of the CRISPR technology. So what they have done is said the DNA cutting has been partially impaired in this CRISPR enzyme, so it can no longer cut. So you still take this small piece of RNA, it brings it to the right address, but then it doesn't cut fully the DNA, it just does it on one side of the DNA. But that's not as important. But what it has, it is stick together with a so-called base editor. So that's another enzyme which has been stuck to the CRISPR enzyme. And then what it does, it recognises say an A in that position, and will just convert it from an A into its opposing letter, which is a G in that case.

Olivia Willis: Okay, so traditional CRISPR, it sends these kind of molecular scissors to the right address in the body, it makes a cut. This is a new, maybe upgraded version of CRISPR which instead of making that cut, it swaps a letter in the DNA and that corrects the mutation.

Marco Herold: That's correct. 

Olivia Willis: And in the case of this baby, a nine-month-old boy who had the mutation and received the treatment, what happened after this treatment was given? 

Marco Herold: So what happened was that essentially the letter has been exchanged, and so the full protein should be expressed within that boy again, and so the breakdown of the metabolites can happen correctly, and thereby you have the avoidance of damage caused by the accumulation of this ammonium in the body of the baby. So that's exactly what they've done. 

The tricky bit was…I described it to you that you just introduce it into a cell and that's easy, right? But you have to also find now not only the DNA bit, but you have to find the right cell, and you have to bring it into these cells, and in that case it's the liver. And what they have used is a cargo which is essentially a fatty bit, so they're called LNP, lipid nanoparticles, and we know them from the Covid vaccine, because during Covid you got the RNA encapsulated in this LNP cargo. And because LNPs have a tendency when they're given intravenously to go specifically to the liver, and then it was there and it would repair it in the liver cells.

Olivia Willis: Now, one of the reasons this case is significant because it's the first time that scientists have developed a customised CRISPR therapy for a single patient designed to correct their specific disease-causing mutation. How does this approach differ from other CRISPR based therapies that have been approved, for example in the case of sickle cell anaemia or other therapies that are in clinical trials for other genetic conditions?

Marco Herold: Yeah, so sickle cell anaemia is a good example, because it's a first FDA approved CRISPR drug, and so what they do in that case, they are not injecting the CRISPR tools into the body of a patient, they're taking out the cells. In that case these are blood stem cells, and these cells will then be essentially manipulated outside of the body using CRISPR techniques. And then once they are manipulated, they're put back into the patient. And because these cells have been corrected, in the case of sickle cell anaemia it is to produce foetal haemoglobin again, in that case these cells have an advantage over the cells which are defect in the body, and they will then outgrow and will make up normal blood cells again.

Olivia Willis: We're obviously talking about, in this case, a rare genetic condition, but CRISPR therapies are also being trialled in cancer treatment, in your area of expertise. Can you tell me about how researchers are using CRISPR technology in treatments in cancer?

Marco Herold: We are trying at the moment, this is what many people do, is they're trying to use CRISPR technique to, for example, enhance cancer eliminating immune cell function. Another approach which I'm starting to work with is using CRISPR tools to essentially deliver these CRISPR tools to the brain of patients and children with glioblastoma, and then essentially cut out or destroy the gene which causes these cells to grow. The good thing about that is this gene is only in the tumour cells, in the cancer cells, and not found in healthy cells. So if you find the right address, so to say, then that could be a way forward to destroy only the cancerous gene, but not the gene which is healthy in the normal cells. 

Olivia Willis: We've talked a little bit about one of the challenges of CRISPR treatments being getting it to the right place in the body. What are some of the other major roadblocks in developing effective CRISPR therapies? 

Marco Herold: The first thing is, as you said, delivery, obviously. Second thing is you get enough of it into the cell so that you really see an effect. The other thing we are still a bit cautious about is that CRISPR, obviously, while we say we have an address, it could be that, you know, number 43 could be read as number 34 maybe. And then the CRISPR goes unfortunately to the wrong spot and makes a cut. We've come far already to avoid this to most extent. And so in the case of the boy, coming back to there, it was tested extensively. So it was, I would say, relatively safe for that case.

Olivia Willis: And one of the things I read in the commentary of this paper was the speed at which this treatment was developed. I think it was about six months from when they were able to assess the mutation to develop the treatment. Can you just explain why that is remarkable, to develop something in that time?

Marco Herold: That is very remarkable because everybody worked together. So basically industry, clinicians, researchers and the patient, or the patient's parents in that case, worked all together to make this work, and the only way you could do that was through collaboration, and that's something we're really also for. You have to collaborate in order to get these breakthroughs for clinical research.

Olivia Willis: When it comes to the implications of this treatment, one of the things that's been discussed is the potential for it to be used to treat other rare genetic diseases. Can you explain how it might provide a blueprint for making customised gene editing treatments for other patients?

Marco Herold: In essence, if you have a monogenetic disease which is caused by one letter being wrong, you could use a base editing approach again, and what you need to change is just the address essentially. We have the whole thing there lined up that it could be used for many other diseases, if accessible, obviously, for this type of edit or correction. 

Olivia Willis: I think probably one thing to note, though, is with a lot of rare genetic disorders, it's not always just one single mutation, right? There are often a lot of mutations that might contribute to the disease.

Marco Herold: Well, that's why I said monogenetic. So, monogenetic, yes, but if you have four, five, six different of these mutations, which are all equally important, and then it becomes difficult. We are not there yet, but we are working at this because it's not impossible to target all of them as well at the same time.

Olivia Willis: Okay. I just want to finish up by asking you about the significance of this research. The head of gene therapy regulation at the FDA until very, very recently, he wrote that this was one of the most potentially transformational technologies out there. Do you agree with that? What do you think about the significance of this for the future of gene therapies, but also medicine? 

Marco Herold: He's absolutely right, because I reckon we can do a lot preclinically, in the lab and so on, as long as we are not trying to use it in a patient in the end, we don't know whether it really works or not, and so they have done this courageous step of doing it, and it worked. It was important it was safe. And I think that's, just as you said before, the blueprint of the next generation. What else can we do so that we really can use the full plethora of the CRISPR tools in clinical applications?

Olivia Willis: That was Professor Marco Herold, CEO of the Olivia Newton-John Cancer Research Institute, and head of its genome engineering and cancer modelling program. 

Norman Swan: What about safety though?

Olivia Willis: It's a very, very good question. So I actually spoke to Professor John Rasco, he's a haematologist and gene therapy expert at the University of Sydney, and I asked him about this particular paper. He agreed with a lot of what Professor Herold said, that the speed was really remarkable, very impressive research, but he did raise safety as an important thing to mention here, so we don't have long-term safety and efficacy data of the treatment. The other thing that Professor Rasco mentioned is cost. So we don't actually know how much it cost to develop this particular treatment, that wasn't disclosed, but he said that it would have been very, very significant, I suspect hundreds of thousands of dollars, if not more. And he said that even though it could theoretically provide a blueprint, it's an important proof of concept, if we were to use it, the cost of developing treatments for other patients with rare genetic conditions is still likely to be very expensive because it's going to require really rigorous pre-clinical testing. It might need to be targeted to different parts of the body and so on. And so he essentially said, look, gene editing therapies at this point are still going to remain very, very expensive for now and inaccessible to a lot of people unfortunately.