Taysha Gene Therapies, Inc.

Greetings, and welcome to the Tatia Gene Therapy's first quarter 2025 earnings call. At this time, all participants are in listen-only mode. The question and answer session will follow the formal presentation. If anyone should require operator assistance during the conference, please press star then zero on your telephone keypad. As a reminder, this conference is being recorded. I would now like to turn the conference over to your host, Haley Collins, Director, Head of Corporate Communications. Please go ahead.

Thank you. Good morning and welcome to Tayshia's first quarter 2025 financial results and corporate update conference call. Earlier today, Tayshia issued a press release announcing financial results for the first quarter ended March 31st, 2025. A copy of this press release is available on the company's website and through our SEC filing. Joining me on today's call are Sean Nolan, Cassius Chief Executive Officer, Sigmar Nagandran, President and Head of R&D, and Cameron Alam, Chief Financial Officer. We will hold a question and answer session following our prepared remarks. Please note that on today's call, we will be making forward-looking statements 102, including the reproducibility and durability of any favorable results initially seen in the patient's dose to date in clinical trials to positively impact quality of life and alter the course of disease in the patients we seek to treat, our research, development, and regulatory plans for our product candidates, including the timing of additional trials and reporting data from our clinical trials, advice from the FDA on the regulatory pathway for TASHA 102, the potential for the product candidates to receive regulatory approval from the FDA or equivalent foreign regulatory agencies, the market opportunity for our programs, and our current cash resources supporting our planned operating expenses and capital requirements into the fourth quarter of 2026. This call may also contain forward-looking statements relating to TASIA's growth, forecasted cash runway, and future operating results. discovery and development of product candidates, strategic alliances, and intellectual property, as well as matters that are not historical facts or information. Various risks may cause TASHA's actual results to differ materially from those stated or implied in such forward-looking statements. on certainties that we face, please see the reports that we have filed with the Securities and Exchange Commission, including in our annual report on Form 10-K for the full year and the December 31, 2024 that we filed on February 26, 2025, and our quarterly report on Form 10-Q for the quarter ended March 31, 2025 that we filed today. This conference call contains time-sensitive information that is accurate only as of the date of this live broadcast, May 15, 2025. Taysha undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date of this conference call, except as may be required by applicable securities laws. With that, I would now like to turn the call over to our CEO, Sean Nolan.

Thank you, Haley, and welcome, everyone, to our first quarter 2025 financial results and corporate update conference call. I will begin with a brief update on our recent activities. then Sukha Nagendran, president and the head of R&D of Tayshia, will provide an update on our lead Tayshia 102 gene therapy program and clinical development for Rett syndrome. Cameron Alam, our chief financial officer, will follow up with a financial update. And I will provide closing remarks and open up the call for questions. This year has been marked by strong execution across our Tayshia 102 program and clinical evaluation for pediatric, adolescent, and adult patients suffering from Rett syndrome. We are pleased with the significant regulatory and clinical progress that we believe continue to support a clear path to registration. Importantly, our analysis of the natural history data, coupled with the longer-term clinical data from our low-dose cohort and interim high-dose data that we have collected across a broad range of ages and stages of patients, with Rett syndrome in our two Reveal Phase 1-2 trials have further informed the therapeutic potential of TASHA-102 and supported our alignment with the US FDA on key elements of our development plan for Part B, the pivotal phase of our trials. In February, we shared that we completed dosing of the 10 patients in Part A. the dose escalation portion of the Reveal Phase 1-2 adolescent-adult trial and the Reveal Phase 1-2 pediatric trial, with six patients in Cohort 2 evaluating the high dose of TASHA-102 of 1e to the 15th total vector genomes, and four patients in Cohort 1 evaluating the low dose of TASHA-102 of 5.7e to the 14th total vector genomes. As our data shows, further mature, we're pleased that TASHA-102 continues to be generally well-tolerated across the high- and low-dose cohorts with no treatment-related serious adverse events or dose-limiting toxicities as of the April 10, 2025 data cut-off. Recall, patients being evaluated in our REVEAL Phase 1-2 trials are in the post-regression period of the disease. where functional gains or restoration of loss function are not expected to occur in the untreated population. Previously, we shared clinical data from the low-dose cohort in our reveal trials, where pediatric and adult patients with advanced disease not only showed clinical improvements, but also gained functional skills across the domains of fine motor, gross motor, and socialization and communication which represent improvements in activities of daily living. This included beginning to use eating utensils, sitting independently, standing up from a chair independently, and the ability to use an eye gaze communication device. Each of these functional gains reflect meaningful skills that can significantly improve a patient's quality of life by affording greater independence and autonomy. These functional gains, which are not expected to occur in the untreated population of patients with Rett syndrome based on natural history data and the additional clinical data we have collected since from our reveal trials, have supported our interactions with the FDA regarding the optimal regulatory pathway for TASHA-102. Over the past 18 months, we have maintained frequent ongoing discussions with a broad FDA review team, including senior leadership through the regenerative medicine, advanced therapy, or RMAT mechanism. These discussions, which have been rooted in robust data-driven findings, have been aimed at advancing TASHA 102 toward a pivotal trial design in which clinically meaningful functional gains are assessed in a rigorous and bias-mitigated manner across a broad patient population. To date, we believe our interactions with the FDA have consistently been productive and supportive of our development approach. As such, I'm pleased to share that we have obtained written alignment from the FDA on key elements of our pivotal Part B trial design for TASHA-102 and next steps to enable the initiation of the pivotal trial. Importantly, The FDA advised us to proceed directly to submitting our pivotal trial protocol and associated statistical analysis plan as an amendment to the investigation on new drug or IND application, which we expect to submit in the current quarter. This approach eliminates the need for a formal end of phase meeting, which may expedite study initiation and registration. We truly appreciate the clear, constructive, and collaborative interactions with FDA to date and believe this progress on our registrational pathways support the strength of our data-driven approach and further enables our goal to bring TASHA-102 to patients with this devastating disease as expeditiously as possible. We are focused on finalizing the details of our protocol and statistical analysis plan as we prepare to submit the IND amendment this quarter. In the coming weeks, we plan to provide a fulsome update on our pivotal Part B trial design, our Rett Syndrome natural history data analysis, and the clinical data from Part A of our reveal trials as part of a TASHA 102 program update in conjunction with the International Rett Syndrome Foundation's 2025 Rett Syndrome Scientific Meeting taking place June 9th through the 11th. At the IRSF meeting, we will deliver three oral presentations related to Tayshia-102, including one focused on our clinical data. As we approach these critical milestones, our confidence in our differentiated gene therapy candidate continues to strengthen based on the recent developments highlighted today. We believe Tayshia-102 has the potential to provide meaningful benefit to a broad population of patients with Rett syndrome using a minimally invasive delivery approach with a clear path to registration based on the critical alignment reached with FDA. I will now turn the call over to Sukhu to provide more context on these advancements that further support a clear path to registration. Sukhu.

Thank you, Sean, and good morning, everyone. As Sean mentioned, we believe we have made significant progress on advancing our TASHA 102 program towards registration. Recall, we have two ongoing Phase 1-2 reveal trials evaluating TASHA 102, an adolescent and adult trial taking place in Canada and the U.S. for females age 12 and older with Rett syndrome and a pediatric trial taking place in the U.S. the UK and Canada, females five to eight years old with Rett syndrome. We are currently evaluating two dose levels of TASHA-102 in Part A, the dose escalation portion of both trials. Our approach from the outset has been to utilize Part A to generate a dataset that informs the key elements of our pivotal Part B trial. There are several key aspects of Rett syndrome that have shaped our development approach for TASHA 102 as we work to align with the FDA on key elements of our pivotal trial design. Rett syndrome is a devastating rare and progressive neurodevelopmental disease that leads to complications in fine and gross motor function, socialization and communication, autonomic function and seizures. The functional impairments and disease features often necessitate 24-7 care and lifelong assistance, leading to a significant caregiver burden and severe impact on quality of life. There is a significant unmet medical need. Additionally, while Rett syndrome is a heterogeneous condition with different levels of clinical severity based on each patient's distinct genetic background, patients generally follow a common trajectory regarding the achievement of functional developmental skills. Following a period of regression, affected individuals typically enter a plateau period around the age of five or six, during which they're highly unlikely to gain new functional skills or regain skills that have been lost to disease progression. As we think about gene therapy for patients in the post-regression population of Rett syndrome, we've already developed the hallmark characteristics of the disease. The ultimate goal is restoration of function and improvement in activities of daily living. is designed as a one-time gene therapy that aims to address the underlying cause of Rett syndrome by restoring MBCP2 protein expression on a cell-by-cell basis across the central nervous system. Therefore, we believe TASHA-102 may provide the opportunity for patients with advanced stage of Rett syndrome to develop new functional skills. Rett syndrome requires an increased in MECP2 protein to activate the neural circuits necessary for gaining function, as well as time for patients to strengthen these reactivated circuits and learn skills that are affected by the disease. Therefore, we believe that early clinical benefit is a strong indicator that MECP2 protein has reached therapeutic levels that in turn create the opportunity for patients to strengthen their neural network over time and learn complex skills. In both our REVEAL trials, we have consistently seen early clinical improvements and functional gains post-treatment that persisted and strengthened over time. That could be highly unlikely based on natural history data. This has been highly encouraging since patients being evaluated in our REVEAL Phase 1-2 trials are in the post-regression period of the disease where, as Sean noted, functional gains or restorations of lost function are not expected to occur in the untreated population. As we prepare to report long-term low-dose data and preliminary high-dose data across the pediatric, adolescent, and adult patients in our two reveal trials, we hope to see a consistent pattern of early response that deepens over time across a broad population of patients with varying genotypes. We believe this could further support the broad treatment potential of TASHA-102 and move us closer to our goal of bringing a potentially transformative treatment to all patients with Rett's syndrome. Overall, these functional outcomes seen thus far in patients treated with TASHA-102 have supported our ability to reach alignment with the FDA on key elements of the pivotal trial design for TASHA-102 and next steps to enable study initiation. Based on our data-driven findings and ongoing discussions with the FDA, we remain steadfast in our conviction that functional outcomes are the most relevant, objective, and clinically meaningful assessments of the treatment effect of TASIA-102 in patients with Rett syndrome. I will now turn the call over to Cameron to discuss our financial results. Cameron.

Thank you, Sukhu. Research and development expenses were $15.6 million for the three months ended March 31st, 2025, compared to $20.7 million for the three months ended March 31st, 2024. The $5.1 million decrease was driven by good manufacturing practices or GMP batch activities with the intended commercial manufacturing process for TASHA 102 performed during the three months ended March 31, 2024. The decrease in expenses was partially offset by higher compensation expenses for R&D employees as a result of increased headcount. General and administrative expenses were $8.2 million for the three months ended March 31, 2025, compared to $7.1 million for the three months ended March 31, 2024. The increase of $1.1 million was primarily due to higher compensation expenses and increases in legal and professional fees. Net loss for the three months ended March 31st, 2025 was $21.5 million or 8 cents per share compared to a net loss of $24.1 million or 10 cents per share for the three months ended March 31st, 2024. As of March 31st, 2025, Taysha had $116.6 million in cash and cash equivalents. We continue to expect that our current cash resources will support planned operating expenses and capital requirements into the fourth quarter of 2026. I will now turn the call back over to Sean for his closing remarks. Sean?

Thanks, Cameron.

We are pleased with the significant regulatory and clinical progress made across our TASHA 102 Rett syndrome program that continues to support a clear path of registration. With written alignment from the FDA on key elements of our Part B pivotal trial design and next steps to enable study initiation, we believe we are strongly positioned for success as we work to rapidly advance our TASHA 102 gene therapy program toward the pivotal trial and bring us closer to our mission of delivering on TASHA 102 to the Rett syndrome community as expeditiously as possible. In the coming weeks, we look forward to providing a fulsome update on our pivotal Part B trial design, our Rett syndrome natural history data analysis, and the clinical data on both the high and low dose cohorts of our reveal trials during a program update in conjunction with the IRSF scientific meeting. With that, I will now ask the operator to begin our Q&A session.

Operator?

Thank you, sir. At this time, we will be conducting a question and answer session. If you would like to ask a question, please press star then one on your telephone keypad. A confirmation tone will indicate your line is in the question queue. You may press star and then two if you would like to remove your question from the queue. Please note participants are limited to one question and one follow-up at a time. The first question we have comes from Kristin Kluska of Cantor. Please go ahead.

Good morning and looking forward to IRSF in a few short weeks here. So one question we've been getting is what signals can potentially point to there being a dose response given this is a highly heterogeneous syndrome? Should we be thinking about the time to treatment onset? Are there any specific endpoints or anecdotes where the effects might be easier to measure to see if that dose response is there?

Yeah, Kristen, good question. And Suku, feel free to jump in on this. But I think there's a couple things we can look at. One is, as you mentioned, a temporal aspect. You know, as we think about gains of function, we think about some of the improvements we see on a more qualitative level using metrics like RMBA and CGI that, you know, in what we've reported to date, you see early improvements and strengthening over time. We think there could be, you know, differentiation at the high dose in terms of, you know, the time period to see that and also the magnitude of the response that we're seeing. And so, again, assuming the safety continues to look, you know, like we've seen thus far, you know, we've always had the view that the high dose would be the right dose, you know, and we'll talk through that in a more fulsome manner once we go through the data, but that's how we're thinking of it. Suku, is there anything you'd add to that?

Yeah, Sean, what I would also add is that There is the translational data set, right? So the animal to human translation when it comes to motor function and respiratory function. So we've seen some improvement there between the doses. And then the other thing is, obviously, we are reviewing all the clinical data. And obviously, over time, we think it's going to mature and get better between the doses. But logically, the higher dose also, I think, should add a further advantage purely because the further MECP2 or the higher the levels are in this heterogeneous complex disease, neurologically we think that will also have a better clinical impact in the patient population as well.

Thank you. Thank you.

The next question we have comes from Salveen Richer of Goldman Sachs. Please go ahead.

Hi, this is Lydia on for solving. Thanks so much for taking our question and congrats on the update today. Acknowledging you plan to provide an update later this quarter, could you just frame the bar for success and kind of how you're thinking about that in light of the recent regulatory feedback just in terms of the data that we can expect here? Thanks so much.

Sure. I think what's going to be very helpful, you know, for the market is to, number one, see what the natural history analysis that we've conducted you know, highlights. I think that's something that's been missing, you know, from, frankly, you know, for the disease state for quite some time. And so we'll step through our analysis of that natural history. And truly that underlies both the regulatory strategy and the clinical strategy. And so the reason we want to package everything together is to start with just a clear baseline on what would you expect to see in the natural course of the disease. And even though the disease is heterogeneous, the patients really, at a certain point, have a very clear, you know, type of a trajectory, let's say. Secondly, is we'll then explain what the regulatory details are. You know, we've reached alignment on key framework, which, what does that mean? That means we've reached alignment on what the trial design is. We've reached alignment on the primary endpoint. We've reached alignment on the study population. We've reached alignment on the estimated number of patients that will need to achieve statistical significance. And we'll, you know, we'll work to share that with all of you. And then with that, we'll go through the clinical data, both the long-term low-dose data, and the high-dose data, looking through primarily the lens that the FDA has agreed to as a primary endpoint, which we think will be very predictive of what the success looks like in the pivotal trial. So I think it'll give people a very good insight into the probability of success and also then the timeline to a potential BLA submission. So there'll be a lot there, and that's why we wanted to share with everybody today You know, reaching this congruence with the FDA is fantastic. It obviates the need for an end-of-phase meeting, which, you know, when you add it all up could take potentially another quarter to get that wrapped up. We've already reached that alignment. And now that we can step right into the protocol submission, that effectively is a 30-day clock. And assuming there's no issues, you know, we would be able to then proceed with site activities and initiation. So, a lot to update at the IRSF meeting, but very exciting times for the program, and we're poised to, you know, step into Part B and move this closer to BLA.

Thank you so much.

Thank you. Thank you.

The next question we have comes from Joel Blump of Needham & Co. Please go ahead.

Good morning, and let me add my congratulations on the progress here. So you kind of mentioned the timeline in the previous question. Is there any specific feedback that the FDA may provide still post this 30-day period on the study protocol and SAP?

Yeah, Gil. Suku and I can tackle this one. I would say that I'll just start with the framework that the end of phase meeting purpose is generally to align on things or you have a misalignment with the FDA and a meeting is needed to reconcile that. So the good news is we've reached alignment with the FDA on really the key aspects of the trial design, right? So we've got written agreement that The trial design is good. We've gotten written agreement that the primary endpoint is a go. The study population, and we've talked about the statistical analysis plan, and, you know, we're in very good shape there. And so, really, at this point, it's putting the detail into the protocol and making that submission. So, you know, Suga, I'd like you to comment on, if we're at this stage, there could be, you know, potentially a little back and forth, but, They wouldn't have told us to submit the protocol if there was something that could really be a showstopper.

Yeah, so you're correct, Sean. I mean, they would have asked us to come back to further review the protocol, et cetera, if they were uncomfortable with what had been originally proposed. So the odds are that it's highly unlikely that they will have significant further comment. There could be some correspondence if they had a question or two, but it's highly unlikely.

Thank you. Thank you.

The next question we have comes from Morrie Graycroft of Jefferies. Please go ahead.

Hi. Good morning. Congrats on the update and thanks for taking my questions. Realizing there are more details to come on the trial design, can you at least talk about what the primary endpoint will be and if it would include standardized clinical video showing milestone or functional gain? And then I don't know if there's anything additional you could say about the statistical analysis plan as it relates to the endpoints at this point.

Yeah, I mean, I would say that you can expect that the primary endpoint is going to be consistent with what we've been focused on over the last 18 months or so, which has been working towards an endpoint that is objective, it's clinically meaningful, it's very easy to measure, and it's important both to the patients the caregivers, and the clinicians. And, you know, again, without getting too far ahead of ourselves, I would just say, you know, we've always wanted to be in a position where you could have a very efficient, robust clinical study. You know, we've always thought that a placebo was not necessary, that a single arm could work here with the right controls. And so, you know, if that's the case, you would want to make sure that there would be mechanisms in place where you would have, you know, appropriate bias mitigation measures, video assessments, and raters and adjudicators that would be appropriately blinded. So I think, you know, those are the details that we'll provide. But we're in good shape on all of that in terms of, you know, the alignment that we've obtained with the FDA.

Got it. That's really helpful. Okay.

Thanks for taking my question. Thanks, Maury.

The next question we have comes from Yanan Zhu of Wolfago. Go ahead.

Great. Thanks for taking our questions. I was wondering how does the aligned design compare with your proposal or your desired design going into the meeting. And also, it sounds like natural history will be playing an important role. So just wanted to perhaps ask whether this is a single-arm design. And I have one follow-up. Thanks.

Yeah, Yanen. I would say that the design that the company put forward is the design that the FDA endorsed. So we had some discussions around, you know, the previous question from Maury, making sure that from a process perspective, you know, everyone was comfortable with what we were going to do and we achieved that. But there was never any pushback from the agency. They've always been very constructive and open-minded to what we've put in front of them. They've only requested data, which is obviously very justified. And the data was in two areas. One was we told them our premise with the natural history data and what that might show. And we've put that in front of them. And they've, I would say, agreed with what we've put in front of them. And then the second piece was the clinical data. And as our data have evolved, we've continued to update them on what we're seeing. And so, it was really the combination of those two aspects of data that got us to this point where we had the alignment and obviated the need for the end of phase meeting.

Oh, great.

Yeah. So, actually, I would, sorry. I was going to ask you, what was the second part of your question?

Right. I was going to ask what might be the role of any data that, you know, which might have played into the lack of a need for the end of phase meeting. So I think you kind of answered that. But let me also ask, you know, is the lack of the end of phase meeting having anything to do with FDA resource capacity? And also, is it a general action on the indication, which means like for other sponsors, this could also be the case? And lastly, do you expect harmonization of the endpoints across sponsors? Thank you.

Yeah, in terms of FDA resources, what I can tell you is we received written alignment, you know, before the announcements with Peter Marks and the departures. We subsequently have had interactions with the FDA where they've maintained that posture. So, we think that there's no relation between not having an end of phase meeting and resources. I go back to Suku's comment earlier, which is the reason for an end-of-phase meeting is generally to either get congruence or you are in opposition. You're not aligned on a key aspect, and so you need to have a meeting to discuss that. Because we've had RMAT, you know, we've already interacted with the FDA three times this year, multiple times last year. We've had a very consistent and, you know, progressive discussion with them. So we've been working towards this for 18 months. And the reality is we got there with them, you know, through this RMAP mechanism, and then there was no need for them to, you know, take the time to have an official meeting. So to us, it highlights the robustness of the data that we've put in front of the FDA, both in terms of natural history and our clinical data to support what we wanted in terms of trial design, endpoints, et cetera. And, you know, we look forward to continue to move things forward. So, you know, it's super exciting. Again, I think keep in mind, usually if you're doing an end-of-phase meeting, I want to say it's a 70-day clock or so. You know, we're now able to submit the protocol, which we say we're going to do this quarter. There's a 30-day wait period. They could ask us for a couple of clarifying, you know, requests. which we would do expeditiously, or they could say nothing. But in a very short period of time, we would anticipate being able to initiate site activities, get the pivotal trial up and running, and, you know, run a very exciting pathway to get to a potential BLA.

Great. Thanks for the cover, and congrats on this update. Thank you.

Thanks, Yannick.

The next question we have comes from . Please go ahead.

Hi, guys. Thanks for taking my questions and congrats on all the progress with 102. Sean, maybe for the Part B portion of the trial, given it's an amendment on IND, how seamless is it going to be to go to the Part B with the current sites that are in the Part A? Or will you need to start with IRB approval for each site, including the Part A sites? And then the second question is, given their significant number of patients in Europe, what are your plans to engage with EMA on the requirements there?

Thanks.

Yeah, in terms of what's nice about the IND amendment, we will leverage existing sites, right? Because we've already been through the contract process. They've already cleared, you know, the initial you know, INDs within their institution. So, you know, we've already prioritized how we want to triage and go through site activation. So definitely, you know, having the, you know, multiple sites up and running and dosing patients is going to be to our advantage. You know, we might add additional sites beyond that, you know, to help make sure that as we open up enrollment for Part B, which we can do in parallel, you know, we'd like to have the most, you know, expeditious enrollment possible. But the fact that we've got multiple sites that are trained on the product that already have a lot of the activities done in the past, we think will facilitate it and allow us to move very, very quickly.

Yeah, and also, Biran, some of these sites have multiple patients who are basically lining up, so we could run multiple patients in parallel as long as they can handle the capacity.

Exactly. And then, Biran, as it relates to EMA, you're right. I mean, there's a nice opportunity over in Europe. You know, when you look at Europe plus UK, it's about the size of the U.S., so it's a very significant patient population. We've got the UK activated. We've got the open CTA there. And we've worked to, I would say, enable the EMA. So we've got that going. And again, with additional capital, you know, potentially down the road, you know, that's where we could expand our footprint. So we've been very disciplined with the resources that we've had. We focus them primarily on the U.S., But in the background, although we haven't said a lot about it, the regulatory team's done a great job of working, you know, in Europe to, you know, put us in a position where we can move forward at the appropriate time.

Thank you.

The next question we have comes from Whitney Ijem of Concord Genuity. Please go ahead.

Hey, guys. I'll add my congrats on all the progress. Just wanted to follow up on the interactions with Astellas. I know you'd previously talked about having kind of the amount of data or the type of data that you'd need to start the clock on a potential opt-in this summer. I guess, is that still on track, or has that been accelerated at all, I guess, given the regulatory outcome here? And then have you been having conversations with them in the meantime, or is it that you'll deliver kind of a final package to them whenever you have it?

Yeah, Cameron, jump in here. But basically, the agreement is very specific in terms of, you know, when things get triggered. And you're correct, there's a data package on pediatric patients that needs to be submitted to them, you know, which is forthcoming now based on the data that we have. You know, I really can't comment on anything. discussions that we may or may not have had with Astellas. I would just simply say that, you know, we'll execute the agreement as it's written.

And, you know, that's part of the process that we're stepping through at this particular point in time.

Great. Thanks. Thank you.

Thank you. The next question we have comes from Jack Allen of Baird. Please go ahead.

All right, thanks for taking the questions and congratulations on all the progress made over the course of the quarter. I just wanted to ask about some of the recent FDA interactions. You had mentioned that you had spoken with the administration in the preceding Dr. Marx's departure. I'd love to hear any color you maybe have as it relates to discussions post-Peter Marx's departure, how consistent the people you've been talking to have been at the FDA. And if you plan to have any even informal interactions given the recent addition of Vinay Prasad to CBER.

Yes, Sukhu, help me out here. You know, from the beginning, our team has been very consistent with FDA since we submitted the IND in terms of the review team and things of that nature. Because we have RMAT, Nicole Verdun has certainly been, you know, at the official meetings, you know, she's been there in her capacity. So we've had, you know, again, consistent senior leadership review. I can say, because we've gotten a question, you know, particularly during, you know, when Peter departed. But, you know, Peter was never in any of the meetings. Like, that's not, you know, his role. He leaves that up to Nicole and the teams, you know, beneath her. So that part's been very consistent. And there really has been no departure, no deviation from the conversations that we had, you know, going back to, you know, call it, uh april of last year everything's been consistent and what we wanted to do the strategy that we outlined and all again all they've ever asked for is to see you know additional data and the natural history analysis which we've we've provided so so i would say um you know through the process things have been very very consistent in the interactions that we've had after the departure of peter um you would not have known that peter had left so the team was you know still very focused on on what we were working towards there was no um pause the meetings that we had were on schedule the team was fulsome that showed up um and and everyone was very engaged highly professional and we continued down the path so We haven't seen any impacts with these changes at FDA. I think in terms of additional interactions, The next interaction would be when we submit the protocol and the SAP to the IND. And then there may or may not be back and forth. If they have some questions and, you know, we need to jump on the phone and work things through, we'll do that. But it's also possible that they're comfortable with everything and we just proceed. So that's a little difficult to answer that question. And I would just say, you know, as it relates to, you know, I think as time has gone on and he said more publicly, his comments seem to dovetail in with what, you know, Dr. Macari has said and that there's a high degree of understanding that rare disease is different than large chronic markets. They understand that not all programs need a placebo control. It's not appropriate, particularly for, you know, some of the rare disease programs programs. What's really important is context and a robust clinical trial design. And we think context is important. That makes a lot of sense to us. And that's why, you know, I think the natural history data will make a lot of sense to people in terms of, you know, its importance on how we ultimately, you know, have gotten to this point and hopefully beyond with the agency. So, you know, we feel right now we're in a really good spot. You know, the agency and all these new players continue to talk about the importance of innovation. They specifically mentioned gene therapy. They talk about the fact that, They want to move therapies forward as quickly as possible. And we don't see that there's going to be any impediments based on our interactions today. And I'd ask Suku to give some color as well, because he's the one in the meetings.

Yeah, Sean, what I would say is that when it comes to the FDA and CBER, the team that has been reviewing the RET program for gene therapy has stayed consistent. So it's the clinical team or the biostats team. So no concern there when it comes to any variability in evaluations over time. When it comes to Dr. Prasad, I think he's a very bright young individual who's done a lot of good research. And the focus here is, you know, You know, disease, one disease at a time, give me appropriate data, and then it will obviously proceed rapidly through the FDA review process. So even though there was a lot of noise, I think when he was initially chosen, it's very clear recently that he is going to really make a difference when it comes to the whole rare disease review process.

Got it. Thanks so much, Dr. Culler.

And congratulations again on all the progress. Thanks, Jack.

Thank you.

Ladies and gentlemen, just a reminder, if you would like to ask a question today, please press star and then one now. The next question we have comes from June Lee of Truist Securities. Please go ahead.

Hey, thanks for the update and for taking our questions. Aside from clinical data, do you have any biomarker data from CSF or others that inform you that your construct is auto-regulating like P2 has designed? And are you able to indirectly at least approximate the level of MEKP2 being produced in these patients corresponding to the doses being administered and relative to the wild type individuals? And as a quick follow-up, what would be the timelines for Part B enrollment and study completion after you amend the IND this quarter? Thank you.

Yeah, on the second part, we would, we will give more

guidance on that once we hear back from FDA, or we don't, once we get through the 30-day period. But I would say if that's the case, June, then we would be initiating sites right away and, you know, potentially getting into dosing, you know, the fourth quarter of this year, you know, first quarter of next year. So it's a very short timeline to make that happen. As a result, as it relates to the MECP2, I'll turn it over to Suku.

Yeah. So, Jun-Li, I mean, that's a good question. It's asked all the time. At the present time, there is no way to measure MECP2 levels in the CSF bloodstream or cell. And in the cell, I'm talking about the neuron on the astrocyte. It's intranuclear proteins that is there and then I think gets turned over very quickly. So, thankfully, when it comes to our product, given how quickly these patients respond, To our gene therapy given intrathecally, and because our construct is also self-complementary, clinically, you know, as you probably know, we help restore sleep abnormalities, autonomic dysfunction, fine and gross motor abnormalities, usually within the first four to six weeks post-dosing. And the clinical measures, I think, are going to be the biomarker at this point in time.

Thank you. Thank you.

The next question we have comes from Sylvan Takokan of Citizens. Please go ahead.

Thank you very much, and congrats on the update, and thanks for taking my question. Maybe to follow up on Maury's earlier question, I just want to see if there's any more color you can give us on the FDA feedback on the endpoint, you know, before you actually reveal the endpoint. Did they specifically agree that it's not effort-based and not objective?

Thank you. It's not effort-based. It is objective.

And it's very clinically meaningful. So, again, we've highlighted, Sylvan, I think over the last year plus that gains of function or restoration of lost function is really something that's critically important to these patients. It's meaningful to the doctors. And it's also something when you start to think about even the payers, if you're able to demonstrate that people are functionally improving, that is going to be meaningful to that particular stakeholder group as well. So we'll outline specifically what this means and also how we would collect this data, but we've been doing it. in a very analogous way in Part A, and we'll step through that when we present the data. But I think it, our view will be it should give a good lens, the Part A data should give a good lens of what you can predict Part B to look like. And, you know, we're excited to do that. So, again, we're pleased with FDA's, you know, alignment with this. They've never been misaligned. It's only been get us a little bit more data. And, really, it was they hadn't seen the natural history data until, you know, this year. So, again, onwards for us, and great, great question. Great.

Thank you. Thanks so much, and congrats. Sounds like a great update. Thanks.

Thank you. The final question we have comes from Evan Sigerman of BMO Capital Markets. Please go ahead.

Hi, Malcolm Hoffman on for Evan, and thanks for taking our question. Do you characterize your level of confidence in Tayshia 1 and 2's safety at this time? With no DLPs or serious AEs to date, it feels like we're getting to a point where there is less risk. but just wanted to get your thoughts there. And just to follow up to that, can you indicate when the most recently dosed patient was dosed again? Appreciate it.

Yeah, on the safety piece, you know, Suku, maybe you can take this question.

I would just say that keep in mind we've now dosed More high-dose patients than low-dose patients, you know, which is also, you know, comforting. But, Sukhu, perhaps you can give more color from, given all your experience.

Yeah, I mean, based on our data set as of April, there is no treatment emerging adverse events or dose-limiting toxicity. So we have no concern, given that the intrathecal approach is pretty benign. And efficacy is pretty obvious based on the data that we've already revealed for the low-dose. The benefits far outweighs the risk.

Thank you. Thank you.

Ladies and gentlemen, we have reached the end of our question and answer session. And I would like to turn the call back over to Sean Nolan for closing remarks. Please go ahead, sir.

Thank you very much, operator, and thanks for everyone taking the time this morning. Again, I just want to say how pleased we are with the alignment we've obtained with the FDA. We look forward to the next steps. The team is working hard right now to finalize the protocol and the SAP. We are on track to make that submission this quarter, again, which can enable us to begin to start site activation as early as summertime. So look forward to the updates at IRSF.

And again, thanks for all your time. Take care.

Thank you. Ladies and gentlemen, that then concludes today's conference. Thank you for joining us. You may now disconnect your lines.