Good morning, ladies and gentlemen, welcome to the Sarepta Therapeutics Limb-Girdle Muscular Dystrophy Type 2E Data Conference Call. As a reminder, today's program is being recorded. I'll now turn the call over to Doug Ingram, President and Chief Executive Officer of Sarepta Therapeutics. Please go ahead.
Thank you very much. This is Doug Ingram. I'm the Chief Executive Officer for Sarepta. Thank you for joining our webcast this morning to report the results of our first cohort of patients in our Limb-Girdle 2E program. Please understand that we will be making forward-looking statements. I would refer you to our public filings for obviously the various risks and uncertainties that come with making forecasts about the future. We're excited to be reporting results today. This is an extremely important milestone for Sarepta. Our collaborator, Dr. Jerry Mendell, wishes he could be with us today, and he sends his well wishes. He is in Columbus, Ohio, and he's continuing to dose patients in our DMD microdystrophin placebo-controlled trial. This is certainly a good excuse for Dr. Mendell.
Presenting the results for us today will be the inventor and the designer of all five of the microdystrophin gene therapy constructs, Dr. Louise Rodino-Klapac. Dr. Louise Rodino-Klapac also happens to be today Sarepta's Senior Vice President and Head of Gene Therapy. With no further delay, let me turn this over to Dr. Louise Rodino-Klapac .
Thank you, Doug. I'm really pleased to be here today to present the results from our first cohort of our LGMD2E clinical trial. LGMDs are a group of devastating muscular dystrophies. These are all monogenic single gene defect disorders that affect hundreds of thousands globally. These diseases are progressive. They're debilitating muscle wasting diseases. There are no therapies for any of these diseases. There's approximately 30 different subtypes. Most of these are autosomal recessive. Unlike DMD, LGMD affects males and females equally. They all affect skeletal muscle, and in many cases, they also affect cardiac and respiratory muscle. The symptoms often are presented with elevated CK, and in many of the severe forms, the symptoms develop before the age of 10. Severe forms like LGMD2E, which we'll talk about today, have significant cardiac respiratory involvement that often leads to premature death before the age of 30.
When we look at LGMD as a whole, there's some heterogeneity amongst the subtypes and progression. When we look within each LGMD subtype, the progression is relatively predictable. Each of the five Myonexus LGMD programs are caused by a single gene defect. In a sense, we have a very simple procedure. We're simply restoring the missing protein, and in all of these cases, we'll be restoring the full-length protein. We've not modified the gene in any way. This is the native protein that we're delivering back. Each of these proteins is associated with the dystrophin-associated protein complex. Three of our programs, of the Myonexus programs, are caused by mutations in the sarcoglycan complex. The sarcoglycan complex is an important complex embedded in the muscle membrane. It binds to beta-dystroglycan, and it binds to dystrophin.
As we've previously mentioned, this dystrophin-associated protein complex works in concert, and when you lose one of these proteins, you can lose function of the entire complex. The sarcoglycan complex is an important binding complex for dystrophin at the C-terminus or the end of the protein. The other important binding site for dystrophin to the membrane is at the N-terminus or the beginning of the protein through spectrin repeats 1, 2, and 3. As you can see, this is why it was so critical that we included these domains within our microdystrophin construct. Again, all of these proteins work in concert, and when you lose one of the sarcoglycans, you lose assembly of that complex, and you also have a secondary reduction in dystrophin. By simply redelivering one of these normal proteins back, you can restore the complex and restore function.
The other two programs that Myonexus is focused on are dysferlin and anoctamin 5, both of these proteins are important proteins involved in the process of membrane repair. When you have failed muscle membrane repair, this leads to chronic muscle damage and degeneration over time. For the purposes of today, we're focusing on beta-sarcoglycan deficiency, which results in LGMD2E. Beta-sarcoglycan is critical because it forms the core of the sarcoglycan complex. It's the first protein to start assembling this complex. It binds to beta-dystroglycan. This, again, is one of the more severe forms of LGMD with significant cardiac and respiratory involvement. Now I'll describe the outline for the study. Today, we're presenting the first cohort results. The LGMD cohort 1 was an open-label trial design.
The entire trial was designed to nine subjects with LGMD2E between the ages of 4 to 15. These first three subjects received a low dose of 5 times 10 to the 13th vector genomes per kilogram of AAVrh74 MHCK7 beta-sarcoglycan. We were very thoughtful in the design of this construct. Again, we used AAVrh74, which we previously shown to transduce muscle, both cardiac and skeletal muscle, very well. Also the MHCK7 promoter, which clearly, robustly expresses in muscle as well as the heart. This is critical for potent effects within these patients to treat all aspects of the disease. The inclusion criteria included two confirmed beta-sarcoglycan mutations. Patients had to be negative for RH74 antibodies. Also have a greater than 40%, of normal on the 100-meter walk time test.
Patients received a pre-biopsy prior to gene transfer, then a predefined 60-day post muscle biopsy. Unlike DMD, LGMD subjects are not on steroids as a standard of care. There's not been any clinical benefit showed conclusively within the literature of using steroids to treat LGMD. These three subjects were not on steroids prior to gene transfer. We did give the patients prednisone one day prior to gene transfer at one milligram per kilogram. They were continued for 30 days and then tapered. The endpoints for this study, primary endpoints included safety as well as expression. We predefined the threshold for success as 20%, of beta sarcoglycan positive fibers, and I'll talk to you about why in subsequent slides. There was also secondary endpoints, which included a decrease in creatine kinase. Creatine kinase is an enzyme that leaks into the serum when there's muscle damage.
LGMD subjects, like DMD, have significantly elevated levels of creatine kinase without any treatment. We also had various functional endpoints in the study. We've been designing this program for many, many years, and we're very thoughtful about how we design the construct and the doses that we chose. We always want to make sure that we're delivering effective dose to patients. In early studies, we used vascular delivery in preclinical models. This is the beta sarcoglycan mouse. We delivered a dose of 5 times 10 to the 12 vector genomes per kilogram, this is a low dose, which led to approximately 20%, of muscle fibers expressing beta sarcoglycan. Importantly, this expression of beta sarcoglycan led to a functional improvement in the muscle.
If you look at the purple bar in the right-hand graph, we saw significant improvement in function as compared to the knockout mouse. This really defined our threshold for success. We knew if we could at least get 20%, we would have functional improvement in patients. Now I'll present the preliminary results of this study. This is cohort one of three patients. Looking at the subject demographics at baseline, our three subjects range between the ages of four and 13. We also saw a range in weight. The patients range from 17 to 55 kilograms in the study. CK levels of baseline are shown on the right, which were relatively consistent between 10,000 and 12,000 units. Now looking at the biopsy data.
At 60 days post gene transfer, we are seeing significant levels of beta sarcoglycan in all three subjects at this low dose of 5 times 10 to the 13 vector genomes per kilogram. The beta sarcoglycan expression was robust. It was correctly localized to the muscle membrane in all three subjects. If we look at mean expression, we see 51%, of muscle fibers are expressing beta sarcoglycan. We also see that the intensity is 47%. If we look at the amount of beta sarcoglycan localized at the membrane and compare that to normal, we see it's 47%, of normal. Now looking at the patient-level data, we see consistency among all three subjects. We're ranging from 42%-63%, of positive fibers for a mean of 51%. We also see consistency in mean intensity amongst the subjects.
In summary, this data greatly surpasses our predefined threshold of 20%, expression in the number of positive fibers. We are 31%, greater than this predefined threshold. We also quantified the amount of total protein in the biopsies. Importantly is, remember, we are delivering the full-length protein, and we are seeing a mean of 36.1%, of expression by Western blot in these subjects. It's important to note that when we're looking at the amounts of protein amongst the three subjects, we see very consistent results between the three. Again, very robust high levels of expression at this low dose of 5 x 10^13 vector genomes per kilogram. This is a summary slide of the data.
What is important to note is that we are seeing vector copies in the amount of 8.4 x 10^4 vector genomes per microgram of DNA, equivalent to 0.6 copies per nucleus. This is the amount of vector copies that were delivered to the muscle. These are relatively low numbers, but this really speaks to the potency of our construct. Over many, many years, we're very thoughtful about the serotype that we chose, the promoter that we chose, and the manufacturing strategy, as well as the other elements within the construct. At this relatively low copy number, we are seeing robust expression. That really speaks to the power of our construct. We're, again, seeing 51%, beta-sarcoglycan positive fibers and 36.1%, of normal on Western blot. These high levels of expression are also correlating to functional assembly of the complex.
As I mentioned previously, we see reduction of the other sarcoglycans without an LGMD2E. When we look at the top panels, we see that we have very low levels of alpha-sarcoglycan pre-gene transfer. In the post-gene transfer biopsies, you can see significant upregulation of alpha-sarcoglycan at the membrane that's consistent among all subjects. We are not only restoring the protein, we are restoring its functional complex. This functional complex is protecting the membrane. We can further see that by a very dramatic reduction in creatine kinase post-gene transfer. Again, we're showing these baseline levels of CK between 10,000 and 12,000. At the baseline, after 90 days, we are seeing a dramatic reduction in CK with a mean of 90%, reduction. Very significant levels of reduction following gene transfer.
This reduction is specific to the gene therapy, and this is evidenced by work that we did previously in another form of LGMD at a much lower dose. This was a study that was done just to look at gene therapy in isolated limbs, so not systemic. These patients were given the same steroid protocol that we gave in this LGMD2E trial. What's important to note is that in this trial, looking at the same time course, we saw no impact on CK in LGMD patients. There was no drop using the same steroid protocol. The drop that we're seeing is specific to LGMD2E gene therapy in this patient population. In terms of safety, all the patients are doing very well. Patients one and two have 90 days of follow-up. Patient three has 60 days of follow-up.
In the trial, two patients had elevated liver enzyme elevations. One of these was designated a serious adverse event. This patient presented with mild jaundice and elevated bilirubin. Out of abundance of caution, the patient was admitted and given fluids as well as re-administering steroids. It's important to note that both of these events occurred when the patients were tapered off of oral steroids. When steroids were re-administered, the symptoms resolved within days, and now these patients have been tapered off of steroids and completely back to baseline in terms of their liver enzyme elevations. Because of this, we've modified the protocol that patients will now be on steroids for 60 days before being tapered to eliminate liver enzyme elevations in the future. It's important to note that the evidence of liver enzymes is seen in other gene therapy trials. We've seen it in microdystrophin.
Others like AveXis have seen it too, so it's not unexpected, but we will proactively extend the steroids to avoid this in the future. There were no other clinically significant findings. This included no decreases in platelet counts. Two patients in the study had transient mild nausea that occurred within the first week when steroids were administered. This didn't correlate with liver enzyme elevations or any other abnormalities. Just to summarize, I feel very gratified to present this data to you today. This is after many, many years of work developing this construct and trying to find a meaningful treatment for these patients that we're working so hard for. I'd just like to thank everyone. I'd like to thank Dr. Mendell for a great collaboration. It's very gratifying to see a therapy that has the potential to really change these LGMD patients' lives.
Now I will turn it back over to Doug Ingram.
Thank you very much, Louise. Louise, let me give you a little self-indulgent here for people in the room. Can we thank Louise Rodino-Klapac, and in his absence, Dr. Mendell, for joining me here? Let me contextualize, if I might, the importance of what is a very significant milestone and what we see as very remarkable but preliminary results for this program. We have been saying for some time that we have a strategy of building an enduring gene therapy engine, a gene therapy platform, that really founded on a couple of premises. The first premise is that the era of gene therapy as a transformative modality is upon us now. It's not something in the future, and we need to move fast.
We also have believed that if we design well, if we choose constructs well, if we choose therapeutic areas well, that we can create a portfolio of therapies that have two very important features. First, that they will individually and in the aggregate, have a greater probability of success than one might see in traditional research and development. Second of all, that we can have faster timelines than one might see in traditional development. One of the very encouraging aspects of not only these results, but the results that we saw last year, is that we are validating the Severi approach to building a gene therapy engine. Let's just quickly preview what we're talking about. We've now seen unprecedented results, preliminary though they may be, in two programs in a very short period of time.
To remind us, in the summer of last year, then in October in Mendoza, we saw the preliminary results from our microdystrophin gene therapy program. I would remind again that Dr. Louise Rodino-Klapac was the designer of that construct as well. We saw what were at the time remarkable results for our first neuromuscular gene therapy program. At 2 times E to the 14th, we had on protein positive fibers, 81%. We had intensity of 96%. On Western blot quantification, we had 96%, across the four patients. We saw what no one had ever seen before at the time, which was this remarkable drop in creatine kinase, or CK, levels of 78%. I think we all understand that CK is closely associated with muscle damage, I think there was a lot of excitement around that.
We believed at the time that there would be read-through from our microdystrophin program into our first limb-girdle 2E program for a host of reasons, including the fact it's the same capsid, it's the same promoter, it's the same inventor. Indeed, that is, we believe, what we are seeing right now. I would remind you that this dose is 5 times E to the 13th. The results we're seeing right now are at a dose of RH74 that is a quarter of the dose that we had with our microdystrophin program. Yet here we're seeing 51%, beta-sarcoglycan-positive fibers where the study design would've said 20%, was a significant functional improvement and success. We're seeing 47%, as you know, on intensity.
On Western blot measurement, I don't think anyone's ever, but for Duchenne Muscular Dystrophy programs, seen quantification on Western blot of the neuromuscular protein at the sarcolemma like this, 36%. Once again, we're seeing striking reductions and very encouraging reductions in CK of 90%. It is becoming clear to us that there is something going on here that is much more, for instance, than just dose. There is something in the elegance of the design of these constructs, the particular promote r that Dr. Louise Rodino has chosen, which appears to be very productive, the way that the capsid is being used and the like, that's explaining to some large extent the early remarkable results we're getting. We saw this read-through from microdystrophin to limb-girdle 2E, then when we consider these preliminary results, it has implications far beyond 2E.
It really does, we believe, have potential read-through to all five of the limb-girdle programs we have. Remember, we are using the same capsid not only in the rest of these programs versus LGMD2E, but also in our Duchenne Muscular Dystrophy and Microdystrophin program. In three of the five limb-girdle programs where it is important to have robust expression in the heart, we're using the same very powerful promoter, MHCK7. Of course, as I've said many times already today, we have a common inventor across these programs. These five programs together, while the epidemiology on this is still evolving, are very likely in the U.S. about the same size of epidemiology and patient population as Duchenne Muscular Dystrophy, and perhaps even larger around the world outside the U.S., given some of the founder effects. The opportunity to do good here is frankly potentially extraordinary. Apologies, everyone.
I'm going to pause for a second while The good news is that has nothing to do with a fire at Sarepta. There should be no sell-off. Okay. Apologies for that distraction. This very next slide is a busy one, it explains all of the various reasons why we have decided to exercise early our option to acquire Myonexus. You've seen that presumably earlier today in a press release, given the results that we've just announced, I sincerely doubt that there's anyone on this call that needs to be convinced of the wisdom of a decision to exercise this option early. I don't think we need to go through all of these slides. We now have full control over these programs, in classic Sarepta fashion, we intend to move with rapidity, I will move on.
Let's talk a bit about the next steps. We have broadly a couple of things that we've got to get done very soon and we've got to report back to you on. The first thing we need to do is to meet as soon as possible with our FDA colleagues and chart a path forward for all five of these limb-girdle programs. To remind us, all five of these programs aim to replace the exact native protein that is missing in the patients that live with these five diseases. These are all very well-characterized monogenic diseases. There may very well be an efficient path forward for these five, but we need to meet with the agency and talk that through and get their insight before we report back.
We also, interestingly enough, have to analyze what the next cohort in the clinical supply might be, this is going to be a very interesting one. The protocol itself provides for the opportunity to dose escalate beyond the dose that we have right now, which is 5 times E to the 13th, we have some work and some thinking to do on that, as you can imagine why. On the one hand, as you've just seen, hopefully would agree with me, we have seen at 5 times E to the 13th very significant and robust expression, both on the protein itself as quantified in a number of different ways, also on related biomarkers. At the same time, interestingly enough, this is actually a dose that is only one-quarter of the dose and the same capsid as, for instance, we've used with our microdystrophin gene therapy program.
We do believe there is an opportunity, if we choose to do it, to go higher. We need to do that analysis, and then we'll come back to you and provide you with an update on it. The good news on that analysis, just so we know, is that there's nothing in the decision about whether or not to do a higher dose in a different cohort that has any impact on the long-term timelines for any of these programs, for a simple reason, which is we can do that with clinical supply as we build out commercial supply. We're well aware that given the discussions we've had with the agency, what we need to do on the commercial supply side is exactly what we did with respect to Duchenne Muscular Dystrophy, and that timeline needs to be built out.
What we need to do here. If you look to the right here, we need to do exactly what we've done with microdystrophin. Now that we have complete control over Myonexus, we need to have the INDs for these programs transferred from Nationwide Children's Hospital to Sarepta, and we need to transfer them out of the nationwide facility into our partner of choice. In this instance, it's Paragon. We need to do exactly what we've done with microdystrophin, which is we need to evolve from the clinical supply program, which is a mammalian adherent process, but a HYPERStack process, to a very similar process, which is a mammalian adherent process, but that's a more scalable three-dimensional iCELLis process. We will start that process and that thinking soon. We'll report back. Great. Move forward.
We've talked about the read-through from Duchenne Muscular Dystrophy to the next five therapies that are under this umbrella of limb girdle, and it will continue beyond that. As you know, we have a very significant portfolio in the gene therapy engine. I expect it will continue to grow over the next 24 months. Moving forward, as you know, we will be dosing first patients by the third quarter of this year in Charcot-Marie-Tooth. We're very proud that it's with Dr. Zarife Sahenk over at Nationwide Children's Hospital. To remind us, Charcot-Marie-Tooth, or CMT, is the largest inherited neuromuscular disease in the world. We are very excited about the opportunity to do good there.
We have MPS IIIA, or Sanfilippo disease, a very serious neurological disorder. We have already, with our partner Lysogene, begun dosing patients in what might very well be a pivotal trial with MPS IIIA. With our Pompe A program, where we're working with none other than Dr. Barry Byrne at University of Florida and Lacerta. We're doing the preclinical work for that right now. Our goal is to start dosing in the Pompe A program in 2020. In short, to use a pun based on our concept of a gene therapy engine, it is full steam ahead for us. We are building out this engine to serve patients. These 2E results and our decision to acquire Myonexus and exercise our option only strengthen our resolve and validate our approach. We'll continue to execute across 2019 and provide updates.
With that, I would open the call up for questions.
Thank you. Ladies and gentlemen on the phone lines, if you would like to ask a question at this time, please press star and then the number 1 key on your touchtone telephone. If your question has been answered or you wish to remove yourself from the queue, you may press the pound key. To allow the opportunity for everyone to ask a question, we do ask that you limit yourself to one question. Our first question comes from Salveen Richter of Goldman Sachs. Your line is now open.
Good morning. Congratulations on the data. At these levels of expression, why would you dose escalate as you go into cohort 2 and beyond, and what goes into that decision? Also, I recognize it's early days, but did you see anything in terms of functional benefit?
Let me answer the broad stroke about just sort of the analytics, and then Dr. Louise Rodino-Klapac can provide more granular on that and also I think some of the qualitative information on function. The short answer is we've just got to do some analyses. With the concept of ensuring that you've picked the absolutely most robust dose, particularly in something like gene therapy, which is itself very unforgiving as it stands right now, you get one opportunity to provide a benefit to patients. It's an important one. You can envision in advance why we can't simply give an easy answer right now. On the one hand, we have what appear to be striking results and great expression, and on the other hand, it does appear that we have headroom to safely look at even higher doses, and we can do all of that.
If we choose to do another cohort, it actually has absolutely no impact on the timeline to get to the community with the therapy. We've just got to put some thought into it and reflect on what the right answer is and probably also take some insight from the FDA as well. With that, I'll turn it over to Dr. Rodino-Klapac.
Thank you. I would just echo that we'll be thoughtful about dose escalation. It was pre-contemplated within the protocol. We've discussed this with the DSMB, and they're comfortable in terms of dose escalating if that's the route that we choose to go after careful thought amongst ourselves as well as with the FDA. In terms of functional improvement, it's early days. We're not providing the quantified data, but we are seeing early signs of functional improvement. We've been talking to the patients that are doing activities that they weren't able to do before. We're looking forward to these results, and so far, the early signals look good.
Thank you. Our next question comes from Ritu Baral of Cowen. Your line is now open.
Hey, guys. Thanks for taking the question. Congratulations on the expression levels. My question's on the adverse event, or the SAE rather. Can you talk about the timing of that event versus when you took the biopsy, when you took the CK levels in this patient, and if you followed CK levels? I think the concern is how much the bilirubin was elevated and whether the patient has completely normalized, and whether we should be worried about roll-off of expression or roll-off of function after the transaminitis.
The bilirubin liver enzyme elevation occurred after the patient had been tapered off of steroids. As I said, it quickly resolved within days. The biopsy was taken after this event, so after the patient had normalized, so there was no impact on expression. CK level was taken over time, and we consistently saw this drop in CK.
Thank you. Our next question comes from Alethia Young of Cantor Fitzgerald. Your line is now open.
Hey, guys. Thanks for taking my question, and congrats on the very solid data you've shown here. Just maybe one and maybe one and a half. Can you maybe frame or help us think about what would be reasonable time period to see a functional improvement? How might that manifest itself? Just on the liver enzyme increase, do you think that there was something about this 1 patient that might have led them to be more predisposed? Is there anything you can talk about there, thanks.
Okay, sorry. Actually, this is Gil Ron here. What I'll do is I'll take the question on the liver enzymes. I think the key thing about that is that we don't believe, we don't have evidence that this patient was different from others. I think the key point is that the bump occurred during a taper in steroids. I think the critical point is that with a re-escalation of steroids, that bump resolved within days. I think very importantly, the patient remains at normal levels or at baseline levels off steroids and has been off steroids now for approximately 20, 30 days. I think that's very good, particularly in the context of a therapy that is given once. We're not talking about chronic dosing here. We're talking about one dose here.
A full resolution, and then the patient is actually now off steroids and remains well, and laboratory's normal. With regard to the functional data, I think Dr. Louise Rodino-Klapac has disclosed that we are measuring this in the protocol, but we have basically just focused on the expression and by distribution data. Our understanding is that the data, the clinical data, are good. However, it is very early days yet, and we feel that it will be later in the timeline of the protocol that we will actually be confident in describing it.
This is Doug. I don't want to minimize AE, but just to remind us, the concept of elevated liver enzymes is what we see with these infusion-based therapies. Three of the four DMD children had elevated liver enzymes in the AveXis program. A significant number of kids saw elevated liver enzymes. In all of those cases, as well as DMD, currently as well as this program, it seems to be very manageable with steroids. It looks like a very manageable issue. With respect to the functional data, just so we're clear, if Dr. Mendell was here today, I believe he would tell you that the early reads on function are looking very good. It is, I think, fairly risky to, after 60 days of a patient that has a degenerative disease, to be drawing sweeping conclusions on function.
We really need to follow these patients longer and frame it better so that we know that when we're talking, we're not potentially misleading in an accidental way.
I think the key message here is that we are seeing robust expression of a full-length protein that is known to be missing in these patients, and it's actually associated with reconstitution of the dystrophin-associated protein complex. The biology is certainly very compelling.
Thank you. Our next question comes from Brian Abrahams of RBC Capital Markets. Your line is now open.
Hi. Thanks for taking my question, and my congrats as well on the data. On the expression data, can you clarify, did you adjust on the Western for fat content or make any adjustments relative to baseline expression levels? Then maybe if you could clarify whether there's any additional clinical data that you have, for instance, data on carriers that might help you further benchmark what your target levels might be and whether you might consider dose escalating or going forward at this level. Thanks.
I'll take the second question. We're really relying on our preclinical data to guide us in terms of dose escalation, being thoughtful about it. I think we know that 20%, is our threshold for success, but certainly, there's an opportunity to go beyond that.
We do know that carriers have a reduction in protein, so I think there's a strong rationale there as well to be able to know that less than 100%, of protein expression will lead to significant functional improvement. I'm sorry, could you remind me of the first question?
Whether you made any adjustments for fat content on Western or any adjustments relative to any baseline expression levels if that differed among the patients. Thanks.
Right. The Westerns were normalized for fat and fibrosis and then compared as a percentage of normal.
Thank you. Our next question comes from Marty Auster of Credit Suisse. Your line is now open.
Hey, guys. Congratulations on the data this morning. Thanks for hosting the call. Had a question for you on the limb-girdle natural history study you're conducting. I was wondering if you could provide an update and maybe if you have an idea of when findings might be discussed or presented in the future. Thanks.
Of that type. Apologies. Distracted. The question was about the clinicaltrials.gov references of natural history studies for limb-girdle. The question was what's the timing of that?
Right. Yeah. The natural history study that's in clinicaltrials.gov was used to identify patients really as an enrollment study for this as well. That's continuing on for LGMD2E as well as other subtypes in our portfolio.
Thank you. Your next question comes from Anupam Rama of JPMorgan. Your line is now open.
Hey, guys. Congrats on the data, thanks so much for taking the question. What are the plans for publication or presentation to the physician scientific community for these initial LGMD2E data? Any specific conferences you're targeting, how much follow-up could we be thinking about, I guess, dependent on which conference you select? Thanks so much.
In terms of presentation, we'll be presenting these results at the MDA meeting this year. We'll certainly be looking for future scientific conferences to do extended follow-up data as well.
Thank you. Our next question comes from Debjit Chattopadhyay of H.C. Wainwright. Your line is now open.
Hey, good morning, thank you for taking my questions. Just one here. Would you expect similar outcomes in older patients? Where do you think COGS will line up if you go with the current dose versus if you have to scale up higher? Thank you.
This is Doug. I mean, the short answer is we have older patients. Just to remind everyone, one of the interesting things about this program is that we have a child that's 4 and two teenagers with two 13-year-olds, and much heavier. This is additional confirmation both on the safety and the ability to get very consistent expression, at least in the first three children, across a very large age and weight range. The COGS are not an issue. I mean, the COGS are always an issue at some level, but let us remember, this is 5 times E to the 13. This is a quarter of the dose of our microdystrophin program.
We're already in the process of working through our Duchenne Muscular Dystrophy program and the RH74 manufacturing, and we're very confident about where our COGS are going to come out and our gross margins eventually will come out. Within any reasonable range, if we stay where we are, obviously, it would be a lower COGS, but still very comfortable. If we went higher, it wouldn't stress the system in the slightest.
Thank you. Our next question comes from Tazeen Ahmad of Bank of America. Your line is now open.
Hey, good morning. Just to follow up on the question around age. It seems like we saw a relatively similar reduction in patient number 2, who is the younger patient, relative to the teenagers. Is that something that you had expected? Did you potentially think that the earlier you're starting, the more pronounced effect you would see?
Yeah, I think we're seeing very consistent results amongst the ages. I think based on the expression, we see a similar reduction in CK. Really based on similar levels of expression, I don't think we thought prior to this that we would see a difference between ages.
Certainly, one of the hopes that we always have is that as we intervene earlier in a patient's life, the opportunity to catch damage before it occurs and sort of correct in advance is helpful. Of course, the mechanism of action is the same across all of these patients, and it's similar across all of the limb-girdles, and it's similar with respect to this monogenic disease that is Duchenne Muscular Dystrophy. The reason for the patient's degeneration is very well understood. They are missing a particular protein that is a structural protein that is missing at the sarcolemma and is causing this damage. That's the case if you're frankly one year old, and it's the case if you're a 20-year-old or a 25-year-old. This is three patients. I want to be very clear, we need to be thoughtful.
This is three patients, these are preliminary results. Certainly, it's gratifying to us that these results are very consistent across all of these three patients and that the patients themselves have some validating aspects. One's four, two are 13. The weights are different among these patients, yet we're getting very good expression even at five times E to the 13.
Thank you. Our next question comes from Danielle Brill of Piper Sandler. Your line is now open.
Hi, guys. Good morning, and congrats on the data. I'm just curious, was the steroid regimen employed in these patients different from the microdystrophin program? Looking at age from a safety perspective, could the LFT effects be more pronounced in older patients?
The steroid regimen was the same for the microdystrophin trial, but it's important to note that the DMD patients were already on steroids as a standard of care, whereas in LGMD, they're not on steroids. When you're tapering them off, they're going to zero steroids versus DMD, where they're still on a maintenance dose of steroids. That's the difference. The steroid regimen for the trials were exactly the same.
It should also be noted, and I know Dr. Rodino-Klapac said this before, but it bears reminding that with respect to these patients, because standard of care historically is not to have long-term maintenance of steroids. That's one issue on them coming into the trial and getting on steroids, but also know that two of the three patients have already gotten to the point where they're fully off of steroids. They've gone back. Their liver enzymes are back to normal, and they're not on steroids at all now. These issues look very manageable with a good steroid protocol in connection with infusion.
Thank you. Our next question comes from Gena Wang of Barclays. Your line is now open.
Thank you for taking my questions. I have two very quick parts. First question is, are there any differences in baseline Western blot and any differences in vector genome copy per nucleus, particularly in the young patient versus the two older patients? Another related question is, did you check dystrophin expression on the membrane?
The baseline levels were relatively low consistently across the three patients. In terms of vector copies, we saw no trend with age, and they were relatively consistent amongst the patients. As far as dystrophin, we haven't done a quantitative look at increases in dystrophin yet.
Thank you. Our next question comes from Christopher Marai of Nomura. Your line is now open.
Hey, congratulations on the data. I was wondering if maybe you could walk us through thoughts on potentially how you may move to a higher dose and specifically what you've been seeing in non-human primate models. Did this dose sort of scale linearly if you had looked at it in those models? Secondarily, just could you comment on the self-complimentary constructs and the potential for durability there versus the other constructs? Thank you.
In primate models, we certainly have safety at much higher doses, up to 2 to the 14th vector genome copies. I think we'll just be thoughtful about it. We have dosing studies in preclinical models that suggest that we can move up, but we just have to look at the entire picture, discuss it with the DSMB and FDA, and decide whether we're going to go up where these results are spectacular. We're in a conundrum. We have fantastic reduction in CK, do we need to go up? That's just a discussion that we have to have. In terms of the self-complementary construct, you don't have to wait for the second-strand synthesis in self-complementary vectors. That just allows you to get expression earlier. We start seeing expression within the first week. Presumably, that doesn't lead to any increase in expression over time.
It's just a more efficient process because you don't have to wait for that second-strand synthesis. Really, in terms of durability, it has no difference versus a single-stranded construct.
Thank you. Our next question comes from Brian Skorney of Baird. Your line is now open.
Hey, good morning, guys. Thanks for taking my question. I guess maybe to just get a little more color on your thoughts around regulatory strategy here. Obviously, you have EXONDYS 51 approved as a neuromuscular disorder drug based on low levels of protein expression that's similar to a wild-type protein, and we sort of discussed the FDA strategy in terms of microdystrophin gene therapy and regulatory, not concerns, but considerations around using an engineered protein that's distinctly different from the wild-type protein. Here you have a wild-type protein. Just what are your high-level thoughts, given that you just went to the FDA to discuss microdystrophin gene therapy in regards to the potential for this to be approved on just expression alone? Do you think that you're going to be pushed to show functional endpoints in a randomized controlled manner?
Just thoughts on how the regulatory agencies are looking towards monitoring durability of this. Will you look at additional biopsies down the line? Is CK a good measure? Just stemming from that, have you looked at continued CK levels on the microdystrophin-treated patients, and do they remain suppressed below 10,000 units per liter? Thanks.
Yeah, thanks for this question. I'll give you the most direct answer on that, which is we really have to sit down with the agency and talk to them, and anything that we say right now about the pathway forward with the limb-girdle programs is, until we speak to the agency, speculation on our part. Your points are very well taken, which is we know that CDER's perspective on the pathway for truncated dystrophin. We also know the agency's perspective on the importance of showing the functional correlate of microdystrophin when you've engineered the protein. This is neither of those.
This is the native protein, to your very good point. Certainly the agency has made some public comments recently about the pathways for potentially curative gene therapies, particularly when you're dealing with an actual correction of the underlying disease like we would theoretically be doing with all of these 5 programs. One could envision a world in which the agency may see accelerated approval as the appropriate pathway for these rare diseases where you're getting robust expression of the native protein. I really do want to caution all of us that the good answer to that question comes only after we sit down, we have a thoughtful discussion with the agency, we take their insight, we'll come back and talk about it. We will do that, by the way.
We will come back and talk about it, we'll be able to give you a much better view on the pathway forward and the value of various biomarkers as well. We'll line that up as well with essentially a form of Gantt chart on the commercial process to get to commercial supply. Because as will be the case with these limb-girdles, I think the gating item is going to be tech transfer over to Paragon, process development, and commercial supply for commercial supply dosing as well for all these 5 trials, just as it is over at Brammer with microdystrophin. These are really interesting questions. I think that there are differences between an engineered gene and these genes. We need to take some advice from the agency and come back thoughtfully after we've done that.
Thank you. Our next question comes from Tim Chiang of BTIG. Your line is now open.
Hi, thanks. I think you guys mentioned that you'll most likely present the data at the upcoming MDA meeting in April. Is it possible that you could show some additional functional data at that meeting?
Well, we don't have any current plans. To be very direct, I can tell you, because I don't think I'm misspeaking what Dr. Mendell would say, that he has some functional results, and he has the clinician's view on how the patients are doing, and I'm quite confident that all those answers would be very positive right now. We all must remember that these are two-month biopsies, and we don't want to inadvertently oversell the data until we have more information. April isn't very far away from where we are today. I would suspect that the information that we're going to have at MDA is going to be expression level data, biomarker data, and related information, and we'll await a time when we have more confidence on the functional data before we start really discussing it.
Thank you. Our next question comes from Vincent Chen of Bernstein. Your line is now open.
Congratulations on the data. One quick one. In the patients who were treated thus far, could you provide a bit more color on the types of mutations that they had? I'm particularly curious whether these patients would be primarily missense mutations who would be likely to have some minimal level of sarcoglycan at baseline, or if these would include patients with, for example, frameshift mutations who might be expected to have essentially no detectable sarcoglycan. Are there specific mutation types which are being included in the trial?
The patients in this trial were missense mutations.
Yeah.
Yeah.
It's worth pointing out that in this disease, the great majority are missense mutations that are described to this disorder. It's a different span of mutations that we see in this disorder than you do, for example, in dystrophin, from whence I think you're taking the frameshift question.
Thank you. Our next question comes from Joel Beatty of Citi. Your line is now open.
Good morning. Thank you for taking my questions. This is Sean Egan calling in for Joel. Maybe just two quick housekeeping questions, then maybe just your thoughts on high-level thoughts. Could you maybe comment whether this modified steroid regimen, the 60-day regimen, has been transferred to the microdystrophin program? Could you comment whether all patients in this trial were from the same drug batch? Could you provide just your high-level comments? This is the second indication and second construct where you've exceeded your preliminary and preclinical expectations regarding expression. Could you maybe comment how you teased that through and maybe what could be driving that?
First, I'm sorry. It was three questions there.
I tried to write it down.
I'm so sorry. The first question, I believe, was the steroid protocol for what I call study 2.
microdystrophin.
Yeah. On microdystrophin, I believe the answer to that is that the investigator, Dr. Mendell, has the flexibility to do 30 or 60 days. He has the ability to adapt to steroid use as he sees fit over the course of 30 or 60 days. I'm really sorry about this. Can you repeat your other two questions?
I think the second question was expression levels. Are these expression levels we're seeing predicted by the non-clinical?
Yeah. These were predicted by the non-clinical data in both this program and our other programs with RH74 at this dose. I think you also asked about the vector lot, this was a single vector lot used in all three patients, it's consistent among the patients.
Perfect. Thank you so much.
Yeah. Thank you.
Thank you. Our next question comes from Liisa Bayko of JMP Securities. Your line is now open.
Hi. Just thinking a little blue sky, by the way, congratulations on all this. It's great. Can you maybe comment on where else beyond DMD and limb-girdle muscular dystrophy, where else this kind of an on-target vector promoter could make sense and what you're thinking, I guess, for the rest of the limb-girdle portfolio? I know you're going to speak with FDA, sort of how close are you to maybe starting some initiatives there? Thanks.
Thank you. The short answer is we want to start initiatives across all of these five constructs as rapidly as is possible. We've got a lot going on at the same time, we really want to get to it because the read-through from this 2E program to these other programs is, on the face of it, enormous. As I said many times, this is the same capsid. Three of the five are the same promoter. These are all monogenic diseases. They're all neuromuscular. They all are associated with the dystrophin-associated protein complex. The opportunity to do a lot of good across these constructs is enormous. Beyond that, I don't want to overpromise right now, Louise and her team have a center of excellence that we were building out in Columbus, Ohio. We have an 85,000 sq ft facility that we have.
We're looking at exactly the kinds of questions you're asking, which is with the opportunity to do so much good with 7,000 rare diseases, 80% of which are monogenic and one approved in vivo gene therapy, where do we go with this engine and what other constructs should we be looking at? We'll have additional targets, at least aspirationally, internally, identified by the end of this year. Of course, we continue to look externally as well to see if there are external opportunities that align with our thesis around gene therapy, that have the same clever concept and design and approach. Again, we favor monogenic diseases that have the greatest opportunity for both speed and probability of success.
Without overpromising, I would say at the end of this year, it will not surprise us, and it probably doesn't surprise external folks either, that we may have additional opportunities to bolster our gene therapy approach.
Thank you. Our next question comes from Yun Zhong of Janney. Your line is now open.
Hi. Thank you for taking the question and congratulations on the data. Are you able to provide a little more details on the magnitude of liver enzyme elevation? Then, based on the study design posted on ClinicalTrials.gov, looks like three patients are to receive placebo in the high-dose cohort. If you do decide to dose escalate, would there be any patient receiving placebo, or would that be dependent on your discussion with the FDA? Thank you.
We adapted our thinking. The original design of the study had envisioned maybe we'd have a placebo patient in some of these cohorts. We looked carefully at it. There's really very little additional insight one would get from that. For instance, with this cohort, this original cohort had initially been designed to do two actives and one placebo. As we took a careful look at it, there was no good reason not to get more data and do three patients. Until we get to the point where we're designing something to ensure that this is for approval, we're going to adapt ourselves so that we're moving as fast as is possible. The short answer on the liver enzymes is we had elevated liver enzymes. They very rapidly responded to reinitiation of steroids and resolved.
As it stands right now, two of the three patients, the two earlier of the three patients, have fully cycled all the way off of steroids, and their liver enzymes are staying stable. We haven't talked about this, but I'm sure everybody, I think, is well aware of this, but just for the avoidance of any doubt, both in this program and our microdystrophin program, we have never seen any drops in platelet counts. We've said that in the slides, no one's asked about it, so I think everybody understands that. In case there was a concern, there's never been a platelet count drop in any of our trials.
Thank you. Our next question comes from Tim Lugo of William Blair. Your line is now open.
Hi, it's Myles. Tim, thanks for taking the question. Congrats on the data. It's great to see. My question is just on the 25%, of the dose that you've given in the microdystrophin program, yet you're getting this very robust expression, and it's very consistent across the board, it looks, by Western blot here. I know that we saw some variability in between the four patients on the microdystrophin program. I'm looking at seeing the same capsid, the same promoter, but are you thinking that the differences we're seeing expression between the programs are a function of expressing full-length versus a truncated protein? Or are we getting better at infusion sites that Dr. Mendell's done with a lot of patients now? Or is it still just inherent unexplained variability? I'd love to hear your thoughts on that as we move forward in a potential dose escalation.
Well, in the microdystrophin program, as you recall, we had three patients that were very high expression and similar, then we had one super responder. We have some thoughts on that super responder, which we're excited about, but we're not ready to disclose right now. As it relates to this dose, we're seeing very robust expression. There is a general dose response, I think the one thing that we see out of this that's interesting is it's not all dose. That there is something in the design, the construct, and for the capsid graphs, and maybe even significantly the promoter, that shows us that even at a quarter of the dose, we're getting very robust expression. I think that is meaningful for the future.
Thank you. Your next question comes from Gil Blum of Needham & Company. Your line is now open.
Hello, everyone. This is Gil on for Chad, again, congratulations for your results.
Could you speak up?
Sorry. We're having difficulty hearing you. You're very faint.
Sorry. Can you hear me now?
That's better. Thank you.
All right. Could you perhaps discuss some preclinical data assessing the stability of expression over time with these constructs?
Sure. We have preclinical data in the beta-sarcoglycan knockout mouse out to 27 months with this construct and saw no diminishment in expression. So far preclinical data is very suggestive of a long durable effect.
Remember with our microdystrophin program also, the sarcoglycan, the replacement of a protein, same capsid, same promoter, across a number of animals, non-human primates in with our other partner, the golden retriever muscular dystrophy animal, as well as the mice. We're seeing very robust durability for as long as we've been able to watch these animals, which gets out to sort of seven and eight years. So far, at least the preclinical models, we're seeing very significant durability.
Thank you. Our final question comes from the line of Ritu Baral of TD Cowen. Your line is now open.
Thanks for taking the follow-up, guys. Going back to your comment, Doug, on manufacturing, the fact that you're in HYPERStack now and you want to move back up to iCELLis. Why not think of suspension for limb-girdle? How much could that improve your COGS or would it just be offset by complicating scale up? Can you address that a little bit?
Yeah. It's very interesting. There's a number of different approaches one can take to scale up a manufacturing to your very good point. We could do iCELLis. We could do suspension. People talk about baculovirus as an even more efficient approach. The short answer for us is that we've got to do two things at the same time. Well, three things. Number one, we've got to be able to have a process that scales. It can scale up and can fully serve the community, and that's what we're doing with microdystrophin first of all. The second one is speed. We need to get to the community. When you see results like this, it does place upon us a feeling of enormous obligation to move as fast as possible.
While people talk about suspension and the like, the truth is that we can scale up with iCELLis, and we can do it at a cost of goods that is very compelling. We would much rather scale as fast as possible on something that is as similar as is possible to what we have already seen. The nice thing about iCELLis versus suspension is we are moving from HYPERStack, but adherent in mammalian to iCELLis, which is a three-dimensional process, but adherent in mammalian, and so we can move with much more rapidity. We can lean heavily on what we have already done with microdystrophin to help inform what we are doing here. The similarities are obviously more than a little striking. The final thing, of course, is probability of success.
Our goal is to, frankly, at every stage, people internally are tired of hearing me talk about this all the time, essentially shave risk wherever there is the ability to shave off risk. Choosing iCELLis, I think, is a much higher probability of getting to the right place at the right time than suspension. As I have said, I think before, the very idea of what we are doing in manufacturing is itself a moonshot. We are going from clinical supply to, if we are successful, an unprecedented amount of commercial supply to serve very large communities. Taking the path that has the best speed with the highest probability of success, and we can inform ourselves across each program, explains why we are so focused on doing the same thing with limb-girdle at least that we are doing with microdystrophin.
That is not to suggest at all that with respect to other programs, we might not look at other manufacturing opportunities, suspension, baculovirus or otherwise. With our program with Lacerta and University of Florida, they actually have a very interesting thing that they call the OneBac system, which is an even improved version of baculovirus. I think given where we are with limb-girdle and microdystrophin, this is not the time to experiment with those approaches yet.
Thank you. That concludes our question and answer session for today. I would like to turn the conference back over to Doug Ingram for closing remarks.
All I will say is thank you very much for your time this morning. We appreciate it. Hopefully, everyone appreciated that we've divided into two this webcast that we could spend some time really talking about these early results, that we believe, frankly, are significant milestones for the company. Then we will talk to those who are interested in participating later today on our fourth quarter earnings as well as corporate updates. Appreciate it and thank you very much.
Ladies and gentlemen, thank you for participating in today's conference. This does conclude the program. You may all disconnect. Everyone, have a great day.