The Translational Mixer
The Translational Mixer
Episode 1: Pete Kirkpatrick, mRNA therapeutics and Espresso Martinis
Pete Kirkpatrick, Chief Editor of Nature Reviews Drug Discovery, gives Andy and JC the lowdown on a Nature Conference on RNA therapeutics and what innovations he is seeing in the field of mRNA therapies.
01:44 Nature conference on RNA therapies
08:11 Differences between mRNA therapeutics and mRNA vaccines
14:24 mRNA chemistries
18:08 mRNA manufacturing
22:05 mRNA delivery
27:21 Delivering LNPs to organs other than liver
34:25 Targeting RNA with small molecules
39:35 RNA-guided CRISPR, base and prime editing therapies
48:35 Pete’s tipple
Pete's tipple of choice:
Expresso Martini
1.5 Oz vodka, 1 Oz coffee liqueur, 1.5 Oz espresso.
Shake over large ice cubes for 10-12 sec and strain into a Martini glass.
Garnish with roasted coffee beans.
(N.B. Ideally, 1.5 Oz of espresso should come from ~20 g of ground coffee.)
The Mixer music “Pour Me Another” courtesy of Smooth Moves!
01:44 Nature conference on RNA therapies
08:11 Differences between mRNA therapeutics and mRNA vaccines
14:24 mRNA chemistries
18:08 mRNA manufacturing
22:05 mRNA delivery
27:21 Delivering LNPs to organs other than liver
34:25 Targeting RNA with small molecules
39:35 RNA-guided CRISPR, base and prime editing therapies
48:35 Pete’s tipple
Andy Marshall: Welcome to The Mixer. I'm your host Andy Marshall. I'm here with my friend Juan Carlos Lopez.
Juan Carlos Lopez: Hello Andy, how are you doing?
Andy: So what's the big idea behind the podcast?
JC: Well, Andy, during our tenure at Nature, as editors of Nature Biotech and Nature Medicine, we had the privilege of interacting with a lot of great scientists who have made important contributions to drug discovery, to translational science, and we thought it would be a good idea to sit down with them, share a cocktail, and have an interesting conversation that we can share with our listeners.
Andy: Great. So, who's our first guest?
JC: Today we have Peter Kirkpatrick, an old friend, Chief Editor of Nature Reviews Drug Discovery. He's..fresh from a conference on RNA therapeutics, and he's going to give us the lowdown on that subject.
Andy: Great, let's get stuck in. –
JC: Let's do it. (music) -
Andy: So Pete, such a pleasure to have you here with us. And thanks for coming all the way down to New York from the dark woods of Worcester, Massachusetts. So you've just spent , what is it, a couple of days up at this conference?
Pete Kirkpatrick: Yeah, it's been a couple of days. And thanks very much for the invitation. It's a pleasure to be here on what looks like a day in London.
Andy: Yeah, for our listener, it's kind of pouring down cats and dogs outside. So this meeting essentially was put on by Nature with a couple of companies wasn't it?
01:44 Nature conference on RNA therapies
Pete: yeah , so it was put on by Nature and Alnylam and Moderna, and it was hosted at Worcester Polytechnic Institute which has a quite close relationship with the University of Massachusetts yeah so and I think yeah they had a lot of the kind of pioneers actually over all kinds of RNA platforms.
You know, we had people from siRNA, there was a lot of obviously a lot of people from Alnylam, from John Maraganore, who's recently retired as Alnylam CEO, you know, and there was a strong presence from Moderna as well.
And yeah, and people also working on all types and flavors of base editors, you know, CRISPR, and just a huge diversity of platforms. But also, I guess, you know, this kind of common thread amongst the platforms, which is really how to deliver whatever it is you're trying to, to where it needs to be.
And particularly if that turns out to be beyond the liver, then, that was the kind of key topic of conversation.
Andy: Interesting. How much of the conference do you think was — I'm only asking this because Moderna was one of the organizers — how much of it was about mRNA vaccines and how much about mRNA therapeutics?
Pete: Surprisingly little was about mRNA vaccines. I think perhaps reflecting that there has been so much debate in the past couple of years that if you didn't know about mRNA vaccines now, you've probably been living under a rock. But yeah, there was certainly some discussion on.. the next opportunities for mRNA in various areas where you might be able to apply them as therapies.
I mean, actually, just coming to that, one thing that was kind of fascinating, so one of the speakers there was Katie Kariko, it was perfect timing. When she agreed to make a presentation there, she hadn't won the Nobel Prize, but obviously quite recently she did. So it was great to see her at the meeting , even though it sounded like she had an incredibly busy schedule doing all of the things she needed to do for the Nobel people.
She mentioned in her presentation, which was a fascinating tour of the past 50 years research on mRNA, that —just before she joined BioNTech in 2013 after a long stream of academic things at UPenn which didn't work out for one reason or other and that people were not recognizing the importance of the work she was doing — that she was one of the organizers of the International mRNA Health Conference. And actually at that point in time in 2013, vaccines didn't feature.
So you know you never really know exactly when things are going to be important and which directions things will go in. But, at that time, everybody was thinking about opportunities for mRNA therapies in various different directions. Yeah, so it was a discussion topic. I mean, I think, most of the things here, I think trying to work out how to optimize various aspects of the mRNA platform. It's fortuitous in some ways that this kind of pseudouridine modification that was discovered by Katie Kuriko and Drew Weissman, is a little bit immunogenic; which in the context of a vaccine is desirable.
But when it comes to an mRNA therapy, you're really, you're really looking to be immunologically silent. And, there's multiple dimensions that people are working to optimize mRNAs, partly to remain hidden to the immune system, but also to deal with the challenges of mRNA stability, which is going to be very important for getting the level of protein expression that you need to make a therapy.
There were some very interesting presentations that talked about this interplay between mRNA structure and mRNA codon optimization and how these two things crosstalk. It's really a multi -dimensional problem. You're trying to control lots of different things. You want to optimize your protein expression, but also you need your mRNA to be stable in a vial as well and to be something that you can manufacture.
And, you know, all of these things and these complex parameters are interlinked in the mRNA structure because mRNA has a tendency to form secondary and tertiary structures. And also the kind of codon chosen, which is something that people have also used to try and optimize protein expression. So it came up in multiple different areas.
And people were very interested in it;. what's the next pseudouridine? I think it seems that most of the mRNA therapeutics at the moment are using a slight modification on the same theme. One is methyl pseudouridine. Somebody specifically asked, "What's the next pseudouridine?" Katie Kariko’s answer to that question was, "It's all about chemistry,". But she didn't have an answer to that specific question. Its work for chemists to do. Yeah chemistry as a theme was a really common thread amongst a lot of the presentations across platforms , particularly some very nice presentations on siRNA, which is an excellent example where the first generation chemistry that got to the clinic is very different from that now. There’s been a tremendous amount of optimization of siRNA chemistry to get it where it is now from where it was in 2003.
08:11 Differences between mRNA therapeutics and mRNA vaccines
Andy: One of the things that I've always found super interesting about mRNA as a therapeutic is — and you were mentioning the secondary structure stuff Pete — its this enormous molecule, yeah? I mean thousands of bases where you have the molecule kind of pairing back on itself, and you have these loops, and this all relates to kind of stability as well. So this kind of secondary structure stuff is part of the equation, together with the different chemistries that you're using, whether it's pseudouridine or 5 methoxy pseudouridine, you know, whichever chemistry that they come upon. But I would ask for our listeners ‘ benefit if we could take a few steps back and kind of think about, you know, what are the main differences in your mind in developing an mRNA therapeutic poses compared with an mRNA vaccine? Because they are really different challenges, yeah?
Pete: That's an excellent question, yeah. I mean, you know, I think there are commonalities and then there are differences, So, yeah, I think with the vaccines the immunogenicity built into mRNA and immune’s system’s ability to amplify the intervention I kind of alluded to a little bit, whereas, in the case of the therapeutics, you're really trying to be immunologically silent. But I guess in both cases, you're looking to achieve a reasonable level of protein expression.
The question, also the difference rather, I guess, really when it comes to mRNA medicines, depends a little bit on what your application is. In the case of the vaccines, you know, the longevity of protein expression maybe doesn't have to be that high or long. Whereas depending on what you're intending to do with your mRNA therapy, you may want to be achieving quite a reasonable length of protein expression. And I guess one way of achieving this is the level of stability of the mRNA construct.
So yeah, I think that's going to be an area of focus; how to improve mRNA stability, but also how to improve the amount of proteins being made.
And, you know, because of these tightly interlinked things between, you know, the secondary and tertiary structure that the mRNAs are adopting, and also how the, you know, the choice of codons you select interplays with this, I guess. One thing I guess perhaps I didn't mention previously was that the problem with immunogenicity to some extent, you know, arises from the presence of just uridine in an RNA, which is recognized by the immune system as being potentially viral or of viral origin. And, you know, that's really where the sort of pioneering step of replacing uridine is the thing that enables the delivery mRNA exogenously enables you to actually do something constructive. But you know, one way of getting rid of uridines without having to make any modifications to the base is to change codon choice. In some cases, you can change the codon such that you're producing the same amino acid, but you're not using a uridine in the codon.
And so, yeah, people have been focusing on that, I think, correct me if I'm wrong, Andy, I think CureVac, for a long time, had been very much about codon optimization for mRNA vaccines. They didn't want to use modified uridines or anything like this. They wanted to stick on codon optimization as their strategy. But I think, given what I've seen (not at the meeting) relatively recently, it seems that CureVac have opened up to doing both.
Andy: Yeah, it's going to be really interesting to see how the different chemistries work out. I suspect that it's going to be a different chemistry for the mRNA therapeutics compared with the mRNA vaccines. Did you get that impression?
Pete: Yeah, I did. I think there's actually also some other stuff that this is actually interesting that this wasn't a huge topic at the meeting, but it certainly is an important one in the field and I think you know just to kind of paint a picture I guess of the typical mRNA construct you know it's it's got the coding sequence in the middle but then you have these you know modifications but you have a five prime end and a three prime end of these UTRs and also a cap and this you know this five prime cap and you know and what's going on in these UTR sequences these are also really like a heavy area of focus in terms of achieving things with therapeutic mRNAs. So this wasn't a huge topic at the meeting, but certainly things I've seen elsewhere and stories we've covered in the journal, I guess. Just optimizing these things are really a key tool to improving the lifespan of mRNAs, but also what you're doing with them as well.
There were was also one presentation that you know that was kind of fascinating thing you might want to achieve with mRNA therapies using knowledge of miRNAs to achieve like cell type specific expression and you know some quite neat idea where you basically sort of exploit the idea that that microRNA expression varies a lot across cells and you can potentially, you know, can basically harness this using recognition sequences. If you design into your three prime mRNA UTR in your mRNA to interact with miRNAs, you can potentially switch off your mRNA in some cells rather than others. So this, you know, it's a little bit into the future, but this potential to harness and dodging the same RNA is to achieve cell -type specific expression of your mRNA therapeutics seemed like a really interesting opportunity.
14:24 mRNA chemistries
JC: Yeah, I'm quite interested about this in a slightly different way. And I guess I have — I don't know if it's two questions or if it's the same question that we need to answer or unpack. Moderna, as you know, they already have some molecules in clinical development and one of them is pretty close to me because it's for propionic acidemia, right, which is the disorder that my son has. And they've already recruited a few kids for their phase 1/2 study. And the results that they're beginning to share are pretty positive.
So that's quite interesting because this this condition affects a protein comprising two different polypeptides right? So what they have done is to have these dual mRNA construct that expresses both so that you can treat every kid with with the condition. So it's a pretty massive construct right? It's pretty large. But they still went ahead with the current chemistry. So I'm sort of wondering, I'm wondering if the chemistry is really good enough and what people are trying to is just tinkering with it to get a little more stability out of it? Or are we are still looking for something fundamentally better than this? If we are already going into clinical development with the current chemistry, I'm wondering if people find it sufficiently satisfactory and it's only a question of tinkering with it.
Pete: It's an excellent question, JC. I think one thing, certainly from the questions in the audience, I think there were various expert s in the field, I guess, making this analogy with the history of siRNA and antisense oligonucleotides, and what the first generation chemistry there looked like, and just how different, you know, it now looks. And I think if you can achieve more with the chemistry, and actually Katie Kariko and also Anastasia Khovrova, they were all very much kind of like, chemistry is going to be the answer to this, to this question.
There was one really important comment that came from Melissa Moore, who's recently retired as CSO of Moderna, that I really wanted share. I think in a sense, it's a really important difference between mRNA and say, siRNAs and antisense oligonucleotides. With the latter, basically they were able to do a lot of modifications in those cases on the 2 -prime hydroxyl. She made the point that actually, in the case of mRNAs, that 2 -prime hydroxyl is really important for the fidelity of transcription. So essentially, you can't really mess around with that site, or you have to be very careful messing around with it. Otherwise, you're not going to end up with what you hope you're going to end up with as far as the right protein. So I think for mRNA therapies the types of modification chemistries may be different.
So on the one hand there is the learnings from parallel development of antisense oligonucleotides and siRNAs, which were a little bit separated in time. But siRNAs benefitted from a lot of the chemistry of antisense; some of the same chemistry was taken from one platform to the other. And, you know, there's these things where people have solved the problem and then realized that they can use it in both. But yeah, with mRNA perhaps, I think there may be some novel chemistry that is needed or, you know, ways to, you know, to modify things.
18:08 mRNA manufacturing
Pete: The other difference really between, I guess, mRNAs therapeutics and the siRNAs and ASOs, is length; ASOs and sRNAs are short, you know, that you can make them easily with chemical synthesis. You know, mRNAs are gigantic, and the current way that they're made is through in vitro transcription. How do you manufacture and reliably incorporate chemical modification is another level of challenge I guess, when it comes to mRNA. I'd love to know, actually, this is not something I'm super familiar with, but a couple of people made comments that if you want to make chemical modifications to mRNA, regulatory agencies are going to be nervous if that isn't done consistently. I think you need to be able to have a very strong characterization of whatever chemical modification you're making to your mRNA if it's not something that's done throughout.
It's the early days as far as mRNA chemical structure, optimization, beyond what's been achieved so far, I guess. I mean, I'd love to know how this works, actually, because it's not something I'm super familiar with, but the actual mRNA manufacture process, I mean, I'm assuming you feed your in vitro transcription, the, you know, the components that you're looking for.
Andy: Yeah, that's my understanding, Pete.
Pete: I think there's very little out there where people talk about this stuff. One person from Moderna, you know, said, this is, you know, it's another aspect, actually, of the immunogenicity problem. And I hadn't really appreciated this before. But, just a little bit of a contaminant of double -stranded RNA in a manufacturing cycle, if that gets into the body, then this is going to provoke an immune reaction.
So there's actually a whole in parallel kind of optimization, like sorting out your mRNA manufacturing process. And also, in some cases, people have been working on better polymerases to get a you know, to essentially a better end result in a product that's as free as possible of any double -stranded product. There have at least been a couple of papers put out on this, but I think it's a little bit like the lipid nanoparticle manufacturers; there's a lot of knowledge in the field that just isn't necessarily out there in the public domain in the way that some other stuff is.
Andy: Yeah. Well, I think it's somewhat similar to, if you look at the oligo field, a lot of the kind of proprietary chemical modifications were discovered in Isis, which became Ionis, and then many of those chemists ended up at Alynlam, and as you were saying, Pete, they were able to use those modifications, and they worked very well. But yeah, I think this is going to be really interesting to see how it works out.
JC: I had the opportunity to visit Moderna a few years ago. They were already beginning to think about clinical development of this mRNA for propionic acidemia and COVID was still not in the picture, right? So they had just their labs for this and it was quite striking because when they showed us around the lab, they made the point of showing us their biggest bioreactor and their biggest bioreactor was the size of like a large bucket. It was not one of these massive bioreactors that you see that people have for biologics. So to them that was the power of these that they needed didn't need such big bioreactors that they could do synthesis in a more efficient way. But this doesn't negate the question. of manufacturing. I think that's kind of a challenge.
Andy: It's probably also taken leaps, JC, with what with the COVID-19 vaccines and the number of doses and the kind of attention to scale up, so, yeah.
22:05 mRNA delivery
JC: But you see, the other side of this, and Pete, you were alluding to this at the beginning, is the question of delivery, right? And so, certainly another way to optimize the efficacy of whatever you're delivering is to target it in such a way that it reaches the cells that you're interested in reaching in a much more efficient way so that even if you don't have a lot of the RNA, you may still get a biological response. Was that something that they talked about at the meeting? I've heard, and this is not new, every month somebody solves this problem of delivery but I'm kind of wondering if there was anything there that caught your attention or in just your reading of the literature if there's anything that you'd find particularly exciting in that space
Pete: it's a great question JC and yeah I mean I think you know it was a real common thread at the meeting whether you know whether what was being delivered was siRNA or mRNA or you know or a genome editing therapy , and I think, one thing that's really risen to the fore as a result of the mRNA vaccines, is the lipid nanoparticles (LNPs). And, you know, it's almost got to the point now, you know, like it seems a bit, I don't know, to me, it seems a little bit reminiscent of the, you know, the VHS/Betamax kind of thing. It's like, you know, there are these two platforms now that people are applying, particularly, AAV vectors or LNPs, and there's a lot of cool work going on with both. I'll come to the LNPs because this is relevant to the mRNA therapies. Yeah.
There were some presentations from a professor at Emory called James Dahlman, who's doing some really, really cool work on LNPs and the ability to kind of screen them for their ability to deliver mRNAs encoding in vivo editing components and you know and I guess yeah the thing that was kind of coming across from his work and you know it was this kind of barcoding approach where you have a you know this ability to assess a large number of lipid nanoparticles and to see you know in a single animal where they're getting to and to kind of optimize them, not just on a one by one basis, but up to 70 or so lipid nanoparticles. And this opportunity to do lipid nanoparticle optimization in vivo at a larger scale suggests that the LNP platform is making substantial progress. I get the impression some people were kind of somewhat confident that, you know, this is about genome editing, but, you know, they were optimistic that, you know, that people had developed lipid nanoparticles that were capable of targeting hematopoietic stem cells in vivo, which would be a breakthrough for this. And If you look at Nature Biotechnology, these days there's quite a few of these kind of barcoding LNP kind of things. That seems to be, a new hot trend.
And actually, commenting on that James Dahlman was basically highlighting the difference between the kind of assays they would use for publications and the kind of assays you'd need for clinical translation. His comment was really that they're not the same thing and there aren't that many people who are selecting their LNPs with the kind of assays that would really work to work for the ideal ones for clinical translation. Also something that wasn't at the meeting, but was a commonet from John Androsavich at Pfizer Ventures, is that basically not that many people are aware that rodent models are not really very good predictors of the efficiency of that LNP delivery in humans. A lot of people are working there and not so aware of it. So you know, I think there's definitely this kind of issue around, you know, finding the right assays to identify the right LNPs if you want clinically relevant molecules.
But there are a few companies out there working on this. James Dahlman founded a company , Guide, that got acquired by Beam Therapeutics. There's another company out there from Mike Mitchell's lab at UPenn, Liberate Bio, that are working on a similar kind of barcoding thing to come up with better LNPs. It sounds like there are any number of other stealth companies out there also working on cool players to develop LNPs.
Andy: Another is ReCode Therapeutics. That was that Nature Nanotech Dan Seigwart paper.
Pete: Yeah. Yeah. there's so much going and the ability to optimize different components, on if people can get the right assays, there's the potential to address some of these delivery challenges.
27:21 Delivering LNPs to organs other than liver
Andy: So it seems to me like with LNPs at least there are some problems that we've solved. So with the mRNA vaccines, it's intramuscular delivery and then we know that they get to lymph nodes and they get to the spleen. So those are two kind of organs that we know we can get to with the existing LNP technology. And then of course everything else goes to the liver yeah? The liver is the sink where everything else gets sucked, but then there are so many other diseases; obviously there's the CNS; obviously there's muscle, there's so many muscle diseases that people are interested in; there is the kidney as well and you mentioned the bone yeah so getting to some of the hematopoietic stem cells in the bone that's an important leap as you said. Or the lung, that's another one .
Pete: There are a couple of things relating to that that question. So Kevin Fitzgerald from Alnylam did a presentation —he was talking about various programs and I think one interesting challenge they have at the moment is so many things they could try and which ones to prioritize —on their program in Alzheimer's disease. So, you know, this is in phase 1 at the moment, you know, and they've demonstrated delivery of an siRNA to the CNS for this. And they can see that it's having an impact on APP levels. So yeah, I mean, I think as far as siRNA delivery to the CNS, they've managed to achieve enough to do something impactful, potentially in Alzheimer's. You know, this is a very early stage clinical trial, but given the challenges of anti amyloid antibodies, the level of knockdown achieved by siRNA is really interesting. You know, he also made an analogy where, siRNAs have shown some impact clinically already in transthyretin (ATTR) amyloidosis with cardiomyopathy and there, if you stop the production of ATTR, you do end up clearing plaques basically. So the hope is that you might be able to achieve the same thing for Alzheimer's and it certainly sounded, you know, like at least they'd achieved the sort of step of the delivery challenge part of this problem.
Andy: And that was LNPs, was it?
Pete: Yeah, this was N-acetyl galactosamine (GalNAc). I actually changed the topic there a little bit because siRNAs have these two different approaches to delivery. And the first, you know, the first siRNA to make it to the clinic was using an LNP for siRNA (Patisiran). But basically the ones that have come since have used GalNAc and have exploited the ability to get across.
Andy: But that's to the liver, yeah?
Pete: To the liver, yes. So the conjugate they're using for brain, I don't think he disclosed the conjugate. But in the Nature Biotech paper they used 2′-O-hexadecyl palmitic acid as the right conjugate to get across into the right cells. But that wasn't a focus of his presentation; I think this is an area in which obviously people are coming up with the next target (like asialoglycoprotein receptor (ASGPR) in liver) when it comes to delivery. Its worked out so well for GalNAc just because of the high expression of the ASGPR on liver cells. But yeah, being able to find cell surface receptors that have got similar high concentration to ASGPR in another place. And also the other aspect that he was kind of focusing on was that you're not disrupting some endogenous signaling pathway by jumping on the AGGPR to deliver your siRNAs. So finding similar receptors that are like that elsewhere is you know the challenge.
Andy: Yeah, Moderna had a relatively large team of people when Melissa Moore was there working on the delivery, working on different lipids, amino lipids that have different tropisms to different tissues; It's been a very, very big effort industrially. So when they do find some of these—there's been a few papers kind of talking about these squalene amino lipids that you know have some pretty interesting tropisms for different tissues beyond the liver. To me, this is the kind of the real frontier. If any of these LNP chemistries are something that opens up a tissue — similar to the way in which Alnylam went after the liver and now everybody can get things to the liver — if one of these other organs opens up, then I think it'll be a seminal type of event.
JC: A lot of people already agree that the mouse or the rat or these small animals are not particularly good models for this, and yet people continue testing there. In some of my interactions with the investor community, people worry that unless you've shown that this works in non -human primates, then we're not really interested and one needs to pay attention to that because the amount of work you see in academic institutions in terms of targeting nanoparticles to pretty much every organ and the number of papers and abstracts that get written about this is staggering and people are not paying enough attention.
Andy: It's the same issue with vectorology, with gene therapy. The primate is not the same as a mouse, neither of them are the same as a human. If you're talking about the CNS and then you have like ages, the vasculature changes with age, disease tissue changes. So, I mean, some people are thinking, you know, the best way to go is to start with humans. You can do a lot of work now, analyzing human tissues using single cell RNA seek and work out which things are expressed on the surface of human vasculature in certain tissues and then you choose your target of choice and then you go back into your model and you make your mouse model with that human target and then once you've done that, then you can start to do the work. Yeah. And you hope that that that will be informative. But you know, it's really tricky.
34:25 Targeting RNA with small molecules
JC: So Pete, shifting gears a little bit. Now that we're talking GalNAcs one area that's of great interest to me, at least, and I'm sure that to a lot of other people is this idea of targeting RNA with small molecules, right? So the target in these cases is the mRNA. Was there any discussion of that at the meeting, or is this an area in which you've seen anything exciting that you would like to share with us?
Pete: That's a great question. Actually, there was one speaker there, Chuan He of University of Chicago, who does some work in this general area, but I think he looked at the rest of the program, and he realized that most of it was about either the siRNA or ASOs or gene editing and decided to talk about something else. Yeah, so this topic really didn't come up so much to the meeting. I think just a reflection of the composition of the speakers.
But a couple of people, I guess, highlighted one of the key diseases where it's proven to be possible to come in with a small molecule and target RNA therapeutically. And this is spinal muscular atrophy. Basically there's an antisense oligonucleotide, nusinersen, that has been on the market now for a few years, which promotes the kind of exon skipping in SMN2 that's needed to correct this disease. And very interestingly, phenotypic screening was able to identify a small molecule that gives essentially the end result is the same; it promotes exon skipping.
And I would say, you know, it feeds into a very interesting kind of question. A little bit what we were talking about with assays, I guess, is that if you can come up with good phenotypic screening assays that have meaningful linkage between the screen and the clinical translation, as was the case in SMA and small -molecule screens used at Roche you know, there's really a huge potential still for small molecules targeting RNA to achieve interesting things. So it wasn't a topic that came up at the meeting, but I think we've published an article relatively recently from Matt Disney at Scripps, who's been doing work in this area for a long time, you know, and has also been identifying all sorts of interesting strategies that more rationally target RNA structure with small molecules. And I think there's a huge amount of potential in the area, but it's not something that came up recently.
Andy: Do you think, Pete, that there's a lot of scepticism about it as well, because RNA structures are really tricky to drug?
Pete: I think this is one where the tools for characterizing work going on is really pivotal to achieving something constructive, but also, I guess in the case of the drug for SMA it feeds into something that is quite peripheral to this meeting but actually is very important for therapeutics in general. I mean, we published an article from a guy called Jack Scannell in Nature Reviews Drug Discovery recently, you know, that emphasized the predictivity of your screening tools, you know, wherever they are in the screening process. This is a kind of fundamental thing to the ultimate success of your project. But it's just amazing how little sometimes people question the predictability of the stuff they're working on, you know, they carry on using the same assays the field has used for a long time. And, you know, not surprisingly, at the end, sometimes things don't work yet again. And, you know, I mention this because it perhaps doesn’t get the traction it needs from funders and it's, it was just calling for, you know that I guess that's all. mine was the,
Andy: The two that always come to my mind are Everysdi (risdiplam); that was the SMA drug from Roche (NOT PTC Andy!). And then ataluren (Translarna) for Duchenne from PTC? And they weren’t super convincing.
Pete: Yeah. They weren't super convincing. I think particularly ataluren is approved only in Europe and still not yet approved anywhere else. I guess with so many different platforms out there now, the question is in which diseases would you choose to go after them with a small molecule targeting RNA when you can see the emergence of all of these alternatives that are really heading for the root cause in a much more direct way?
Andy: There's another wrinkle on that, isn't there, which kind of speaks to JC's question, which is this idea of using a drug to inhibit an RNA -modifying enzyme or protein. So I know Storm Therapeutics in the UK is one of the pioneers going after METTL3 which depletes methyl 6 adenosine (M6A). They've been going after that in cancer. And there seems, correct me if I’m wrong, but it seems there’s been a bit of activity there yeah?
39:35 RNA-guided CRISPR, base and prime editing therapies
Pete: Yeah, this wasn’t one of the commons themes, but one other real strong theme at the meeting was the various different flavours of genome editors. It's a really exciting year; we've seen the submission of the first therapeutic based on CRISPR to the FDA earlier this year. I guess there's a possibility that this year may see the approval of the first CRISPR -based therapy for these hemoglobinopathies (https://www.fda.gov/news-events/press-announcements/fda-approves-first-gene-therapies-treat-patients-sickle-cell-disease). I'm going to stick with sickle cell disease and beta thalassemia rather than try and say hemoglobinopathy again. But yeah, if this happens, I mean speed, from the kind of CRISPR papers in 2012 to a potential drug on a new platform just over a decade later; it's incredible.
But you know, saying that, you know, the thing that was also very interesting at the meeting is just how quickly the field has moved on from the kind of first generation CRISPR strategies to various different flavors, which I'm sure you're very familiar with at Nature Biotech Andy; and all the types of base editors and prime editors as well.
And these next generation platforms and their ability to take things to the next level, and particularly beyond the first application that CRISPR Cas9 is good at: disrupting the function of a gene. And in the case of the (Bluebird and Vertex CRISPR sickle cell) case, it's quite a neat idea of knocking out the function of BCL11A, and in that way, essentially, what you're doing is leading to the reactivation of the fetal hemoglobin, and this is what's enabling the treatment of sickle cell disease and beta thalassemia.
What's really exciting, I think, was really like a common theme among several talks at the meeting was the huge potential of particularly base editors because these are the ones that are entering the clinic at the moment. There were some really nice stories there to fix particular diseases with a known root cause in a much more precise way.
David Liu gave an absolutely fantastic presentation. He's really been a pioneer in the field of base editing and prime editing. He talked about various generations of these.
He gave a really, it's quite recent paper in the New England Journal of Medicine (DOI: 10.1056/NEJMoa2300709)) talking about this trial, it's been run in the UK for quite a rare cancer, T cell leukemia; and essentially he just presented a case study that I think was part of this NEJM paper. You know, a young girl who really had just exhausted all existing options for this T -cell leukemia. And, you know, she, as part of this trial, received a base -edited CAR -T that, you know, had three different modifications made to it, and it was so cool to be able to do these three things in a very precise way with a base editor, and as a result, essentially she was basically terminal, and now she's back at school. It's one patient, but it's completely transformed her life in this case, and I think it illustrates the potential of this base editing approach to do things that just haven't previously been possible.
There was also the other area where base editing has been taken into the clinic. Recently, the company, Verve Therapeutics, who have been very ambitiously looking to…
Andy: Cardiovascular, isn't it?
Pete: Cardiovascular disease. You think a lot of the time when it comes to new platforms, people go for things like cancer because the risk benefit gives a lot more of a window than in the case of something like cardiovascular disease. But, there was a really nice presentation , almost following in the path of the statins many, many years ago, but looking at a really severe form of familial hypercholesteremia . I think there was an 11 year old girl who'd had three heart bypass operations by the age of 11, you know, and it's like, they've administered a base editor now. And I think, as I understand it, the first clinical data from Verve's VERVE-101 trial of a base editor that permanently deactivates PSCSK9 in the liver should be being reported this year (https://www.nature.com/articles/d41586-023-03543-z). So I think this is going to be very exciting for the field of base editing.
I come back to David Liu because he's just been such a powerhouse of cool innovation. But, you know, he was actually primarily talking about prime editing, and I think base editing is super cool. It's a little bit further behind, but if you can make prime editing work I think people are kind of comparing CRISPR as a pair of scissors and prime editing as a word processor, you can do so much with it.
And, there's this potential to just completely transform the way that some diseases are treated. There's a really, really interesting kind of concept. At the moment, cystic fibrosis is a rare disease where, you know, Vertex as a company have done an amazing job kind of almost going in mutation-by -mutation in some cases, coming up with a pool of drugs that can treat the majority of the pool of people who have cystic fibrosis. But just imagine if you could go into the coding region of the gene that's got most of these mutations in it and just replace that with you know, a functional cystic fibrosis transmembrane conductance regulator (CFTR). And, you know, this is the kind of thing that could be feasible if you can get prime editing to work.
Andy: Yeah, it's very far in the future though.
Pete: It seems very far in the future. Talking to the people at the meeting, it seems it's far into the future, but maybe not as far as it has been in the past with analogous platforms. I think if you think about the pace of innovation, and you know, an antisense or siRNA, I guess, you know. I'll come to it. There was a really nice presentation from John Maraganore about the history of Alynlam. It took about 16 years or so maybe to get from the formation of the company to the first drug on the market, whereas antisense oligonucleotides took considerably longer. I suppose actually the first one made it in 1998, which is not, you know, it's probably like 20 years after publication of first papers, but for the platform to really kind of, you know, to reach the point where you say, yeah, this is like, you know, it's relatively mature, it was longer. And, you know, now you look at CRISPR and you see like, you know, the pace between pioneering studies and, you know, the potential approval of a drug is getting to be more than a decade.
So, you know, I'm sorry, right, just a little bit more than a decade. And, you know, prime editing is futuristic, but, you know, perhaps with the pace of innovation, it's maybe not so far into the future as has been in the past with innovative platforms, if some of the challenges, particularly the delivery challenge, can be ironed out.
Because what he was talking about was something really very cool;
He's basically coupled, you know, prime editing technology with something else he invented in his lab many years ago, which is this phage directed evolution strategy called PACE, and he was using PACE to optimise components of the prime editor. This ability to kind of harness directed evolution to improve the quality of your prime editors is something that might lead to a much more rapid development of the prime editors with desirable properties that might have been previously possible.
48:35 Pete’s tipple
JC: I certainly agree that it won't be that long before some of these, some of these therapeutics reach the market. I think that there are a few challenges that have to be sorted out, such as again, manufacturing some of the aspects in regulatory science and other things that are not necessarily related to the innovation itself. But I think that that's an important area to look into. Pete, this has been a very thoughtful conversation as we knew it would be. We're already coming to be to the end of the recording. I wonder how many people are still listening, but one last question, Pete, before we let you go. So, as you know, our podcast is called The Mixer. So, our question to you is what is your go-to drink?
Pete: At the moment, it's an espresso martini. I find this is a particularly when traveling. It's what I need in the evening.
Andy: Good for jet lag!
JC: I have never been into espresso martinis, but we can certainly make one. Somebody told me about a secret to get more foam and the secret to get more foam. when you prepare it is apparently to use larger pieces of ice that something I didn't know. I haven't tried it because I don't make this drink too often at home but it's something for a future episode of The Mixer Andy and if you're game for an espresso martini.
Andy: So there you go JC, seminal insights as always. Alright Pete, thanks so much for your talk, it was a really great talking with you and really informative.
Pete: Thanks so much for the invitation, it's really been a pleasure.
JC: Well on that note, I think it's time to call it a day. I must confess I'm not really partial to the Expresso Martini, but for those of you who like the Expresso Martini, we have the perfect recipe down in the description below. Anything you want to add Andy?
Andy: No, this was great. Thanks a lot everybody for listening, until next time. Cheers!.
