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Earnings Call: Q4 2022

Feb 21, 2023

Kylie O'Keefe
Chief Commercial Officer, PTC Therapeutics

Good day. Welcome to the PTC Therapeutics Fourth Quarter 2022 Corporate Update and Financial Results Call. At this time, all participants are in listen-only mode. After the speaker's presentation, there'll be a question and answer session. Instructions will be given at that time. As a reminder, this call is being recorded. I would now like to turn the call over to Kylie O'Keefe, Chief Commercial Officer. You may begin.

Good afternoon and thank you for joining us today to discuss PTC Therapeutics' fourth quarter 2022 corporate update and financial results. I am joined today by our Chief Executive Officer, Stuart Peltz, our Chief Operating Officer, Matthew Klein, our Chief Business Officer, Eric Pauwels, and our Chief Financial Officer, Emily Hill. Today's call will include forward-looking statements based on our current expectations. Please take a moment to review the slide posted on our investor relations website in conjunction with the call, which contains our forward-looking statements. Our actual results could materially differ from these forward-looking statements. As such statements are subject to risks that can materially and adversely affect our business and results of operation.

For a detailed description of applicable risks and uncertainties, we encourage you to review the company's most recent annual report on Form 10-K filed with the Securities and Exchange Commission, as well as the company's other SEC filings. We will disclose certain non-GAAP information during this call. Information regarding our use of GAAP to non-GAAP financial measures and a reconciliation of GAAP to non-GAAP are available in today's earnings release. With that, let me pass the call over to our CEO, Stuart Peltz. Stu?

Stuart Peltz
CEO, PTC Therapeutics

Thanks, Kylie. Good afternoon, and thank you for joining the call. I'm proud to share PTC's fourth quarter and full year results and our expectations for continued strong performance in 2023. PTC treats rare diseases by modulating gene and protein expression. Our strategy is to discover, develop, and commercialize products to build a robust pipeline of potential new therapies. Our goal is to deliver one new therapy every two to three years. I'm honored to report that PTC has been named the winner of the 2023 EURORDIS Black Pearl Company Award for Innovation. This award recognizes and celebrates companies who have undertaken groundbreaking science to advance rare disease research and development, and is a testament to the mission and strategy of PTC. We are planning a very exciting year in 2023, including the celebration of our 25th anniversary, and we're proud of what we've achieved to date.

Our commercial portfolio has five marketed products plus a six product for which we collect collaboration and royalty revenue. In 2022, we achieved $699 million in total revenue, which is a remarkable 30% growth over total revenue in 2021. This revenue achievement was despite substantial FX headwinds, and when calculated at constant exchange rate, it was $740 million, representing a 37% year-over-year growth. In the fourth quarter of 2022, we achieved $167 million in total revenue. We expect our growth to continue to accelerate in 2023. As announced in January, we expect our total revenue guidance in 2023 to be between $940 million to 1 billion, which would represent more than a 30% year-over-year growth.

We are continuing to advance a broad and deep pipeline of new therapies that we expect to provide substantial growth to our commercial portfolio in the coming years. I'm proud that these efforts have led to seven promising development programs focused on treating rare diseases of biomedical need, from which we'll have four important readouts in the first half of 2023, three of which are registration-directed studies. We expect results from the APHENITY study for sepiapterin for PKU, for vatiquinone in both mitochondrial disease-associated seizures and Friedreich's ataxia, and the 12-week data for PTC518 in Huntington's Disease . Matt will go into this in more detail shortly. We're very excited about part one data for APHENITY study with sepiapterin and look forward to the results from part two shortly.

In addition to these studies, we continue to progress enrollment in our SUNRISE-LMS trial for unesbulin in leiomyosarcoma patients and our CardinALS trial for utreloxastat for ALS patients. With solid growth across our commercial portfolio and many new therapies advancing in our pipeline, we continue to generate strong momentum for many years to come. I'll now hand over to Matt for an update on our development programs. Matt?

Kylie O'Keefe
Chief Commercial Officer, PTC Therapeutics

Thanks, Stu. Our teams continue to make progress in advancing important new therapies from our pipeline to patients in need. As Stu noted, in the first half of 2023, we will have results from four of our ongoing clinical trials, three of which are registration-directed studies. Let me begin with an update on APHENITY, our global phase III trial of sepiapterin in patients with PKU. As a reminder, APHENITY is a double-blind, placebo-controlled study in which subjects are randomized to receive sepiapterin or placebo for six weeks. With the primary endpoint being reduction in blood phenylalanine levels. To enrich the randomized population for sepiapterin responders, there is a run-in phase during which all screened subjects receive sepiapterin for two weeks.

Only those subjects who demonstrate a reduction in phenylalanine levels of 15% or more from baseline will be randomized, with the primary analysis population consisting of those who have greater than 30% reduction. Importantly, all subjects entering the placebo-controlled phase will undergo a washout period of at least 14 days. In January, we shared data from the part one run-in phase for the initial cohort of subjects with greater than 30% reduction in phenylalanine levels. I will now provide an update on part one's preliminary data for all subjects. Overall, 156 subjects passed screening and completed the part one run-in phase. Of these 156 subjects, 102 or 65%, had greater than 30% reduction in phenylalanine levels from baseline.

This is a very high responder rate, over three times the responder rate recorded in a Kuvan responder study. When looking at the magnitude of Phe reduction in the 30% sepiapterin responder group, there was a mean reduction of 66%, which is more than twice that recorded in the Kuvan placebo-controlled phase. I want to point out that the 30% responder group includes 15 classical PKU patients who had a mean phenylalanine reduction of 61.5%, which is a very impressive result. I'll add that there were an additional five classical PKU subjects who had a 15%-30% reduction in Phe levels during the run-in phase.

These part one results, including the high responder rate and the mean phenylalanine reduction in non-classical and classical patients, continue to support the premise that sepiapterin can potentially meet the persistent unmet medical need of PKU patients. With the high proportion of subjects achieving an over 30% phenylalanine reduction in part one, the primary analysis population for part two will be over-enrolled by approximately 25% beyond the initial target of 80 subjects. Given the time required for these additional subjects to undergo washout and complete the placebo-controlled portion of the study, last patient last visit is planned to occur in March, and we expect results of part two in May. Let me now move to the two registration-directed trials of vatiquinone, MIGHTY and MOVE-FA.

The MIGHTY and MOVE-FA studies are based on both a strong scientific rationale as well as data from several previous studies in which we have reported evidence of treatment benefit across key disease endpoints. The MIGHTY study is a global registration-directed trial of vatiquinone in patients with Mitochondrial Disease Associated Seizures . The study includes a 24-week placebo-controlled phase with a primary endpoint of change in observable motor seizures from baseline. The placebo-controlled phase will be completed in March, and we now expect results in the second quarter to allow for data cleaning and database lock. The MOVE-FA trial is a global registration-directed study of vatiquinone in patients with Friedreich Ataxia . The study includes a 72-week placebo-controlled phase and the primary endpoint is the change in the validated mFARS rating scale from baseline.

Last patient last visit for the placebo-controlled phase will also be in March, and we continue to expect results of the MOVE-FA study in the second quarter. Moving to our PTC518 Huntington's Disease program, enrollment is ongoing at our global sites for the phase II PIVOT-HD trial. As a reminder, PIVOT-HD is a 12-month placebo-controlled trial in two parts. Part one is 12 weeks in duration and focuses on PTC518 pharmacology and pharmacodynamic effects, as well as biodistribution. Part two is nine months in duration and focuses on blood-based, CSF-based, and radiographic biomarkers of disease. The study initially includes two dose levels, 5 milligrams and 10 milligrams, with the ability to include a third dose level of up to 20 milligrams, leveraging the titratability of the molecule.

As we shared at the J.P. Morgan conference in January, we have initiated additional 5-milligram and 10-milligram dosing cohorts in early stage three patients. We expect results from the 12-week portion of the trial in the second quarter of 2023. Turning now to Translarna. We recently had an informal meeting with the FDA, during which we discussed the potential path to an NDA resubmission. Based on the meeting discussion, we plan to request another Type C meeting to review the totality of data collected to date, including dystrophin and other mechanistic data, as well as additional analyses that could support the benefit of Translarna. We plan to prepare a request for this meeting in the near future. Lastly, for ObsEva, as we previously shared, the FDA requested additional bioanalytical data in support of comparability analyses between the drug product using the clinical studies and the commercial drug product.

We have completed these analyses and have provided the results to the FDA for review ahead of a BLA submission, which we continue to expect will occur in the first half of 2023. I will now hand the call over to Eric to provide an update on our commercial portfolio. Eric?

Eric Pauwels
Chief Business Officer, PTC Therapeutics

Thanks, Matt. It is exciting to see the great progress of our late-stage clinical pipeline. The global commercial team is certainly ready to leverage our expertise and broad geographic footprint to bring these important treatments to patients. Our global customer facing team has delivered yet another strong quarter, continuing the significant momentum built throughout the year and closing out what has been a very remarkable year for PTC. Our launch of Upstaza in Europe is building momentum. The global DMD franchise continues to strengthen, and we see our global commercial expansion delivering significant growth. With a fifth product added to our commercial portfolio, we delivered $128 million of revenue in the fourth quarter and an impressive $535 million for 2022, which represents 25% year-over-year growth for our marketed products. Let me start with Upstaza.

We are pleased with the initial launch of Upstaza following the approval in the E.U. Last year, we treated commercial patients in Germany and patients in France through the early access program. Importantly, we are pleased with the initial interactions with health technology bodies in France and Germany, which will further support pricing and reimbursement in the future. We anticipate continued growth in 2023 by treating patients in other European countries, also enabling cross-border treatment options. Lastly, to continue the growth, we will further focus on geographies outside of Europe with additional registration submissions and named patient programs in Latin America, the Middle East, and Asia-Pacific. Our DMD franchise continues to deliver robust results with one hundred and forty-fourteen million in revenue in the fourth quarter, which brings our 2022 DMD franchise to $507 million, an impressive 20% year-over-year growth over 2021.

This remarkable achievement is despite strong FX headwinds, and when calculated in constant exchange rate, it is $539 million and 27% growth. The fundamentals of the Emflaza business continue to be solid. Revenue in the fourth quarter of 2022 for Emflaza was $58 million. This brings total annual Emflaza revenue to $218 million, which is a remarkable 17% growth over 2021. Operational excellence drove continued new patient starts, broad access, and continued focus on high compliance and lower treatment discontinuations. Turning to Translarna, we achieved $56 million in revenue this quarter, which brings our 2022 revenue to $289 million, which is an outstanding 22% growth over the previous year. Again, despite significant foreign exchange headwinds, we continue to see growth in our main markets now that Translarna is in its eighth year of commercialization.

Additionally, we continue to push forward with our geographic expansion into new markets in Latin America, Middle East, North Africa, and Asia-Pacific. Now turning to Tekturna and Waylivra in Latin America. The focus we have had on building the foundation of these therapies is delivering results. We have strengthened our position in Latin America as the pioneers in rare diseases with our recent approval in Brazil for the second indication for Waylivra in familial partial lipodystrophy or FPL. This is the first treatment for FPL in Brazil and the first approval globally for Waylivra for the FPL indication. As a reminder, Waylivra was previously approved for Familial Chylomicronemia Syndrome and received Category I innovative drug pricing in Brazil.

For Tekturna, we have received our second group purchase order from the Brazilian Ministry of Health, which we expect to fulfill in the first half of this year, and our discussions with CONITEC continues to progress. Across the region, we also continue with our geographical expansion with MAA filings for both Tekturna and Waylivra, and we continue to support and grow our patient base through early access programs. 2022 was a fantastic year for our global customer-facing team and has set us on a solid trajectory for 2023. This has been a transformational year as we continue our launch efforts for Upstaza, launch FPL in Brazil, and continue to grow our DMD franchise ahead of our near-term pipeline readouts. Now let me turn the call over to Emily for a financial update. Emily?

Emily Hill
CFO, PTC Therapeutics

Thank you, Eric. I will take a few minutes to review our fourth quarter and full-year financial results. Please refer to the earnings press release issued this afternoon for additional details. Beginning with top-line results, total revenues for the fourth quarter were $167 million. This consisted of net product revenue across the commercial portfolio of $128 million and Evrysdi royalty revenue of $40 million. Translarna net product revenues in the quarter were $56 million, reflecting strong growth in most geographies despite significant foreign exchange headwinds.

Emflaza had net product revenues of $58 million, representing 22% growth year-over-year. Non-GAAP R&D expenses were $175 million for the fourth quarter of 2022, excluding $14 million in non-cash stock-based compensation expense, compared to $136 million for the fourth quarter of 2021, excluding $13 million in non-cash stock-based compensation expense. This year-over-year increase in R&D expenses reflects additional investment in research programs and advancement of the clinical pipeline. Non-GAAP SG&A expenses were $79 million for the fourth quarter of 2022, excluding $13 million in non-cash stock-based compensation expense, compared to $74 million for the fourth quarter of 2021, excluding $13 million in non-cash stock-based compensation expense. Our total revenue for the full year 2022 was $699 million for year-over-year growth of 30%.

This was impacted by significant ex-FX headwinds, which when calculated at CER, was $740 million and 37% year-over-year growth. This included DMD revenue of $507 million, which represented 20% year-over-year growth, or 27% growth at CER. Evrysdi royalties for the year grew 108% to $114 million year-over-year. Cash, cash equivalents, and marketable securities totaled approximately $411 million as of December 31st, 2022, compared to $773 million as of December 31st, 2021. I will now turn the call over to the operator for Q&A. Operator?

Operator

As a reminder, to ask a question, please press star one one. If your question has been answered and you'd like to remove yourself from the queue, please press star one one again. One moment while we compile the Q&A roster. Our first question comes from Eric Joseph with J.P. Morgan. Your line is open.

Hannah Adeoye
Equity Research Analyst, JPMorgan

Hi, good afternoon. This is Hannah on for Eric. Thanks for taking the questions. Just a few from us. First, can you break down just some of the revenue components in your full year 2023 revenue guidance outside of your DMD franchise? Just wondering how you're thinking about the balance between Evrysdi and Upstaza. I have a follow-up after that.

Stuart Peltz
CEO, PTC Therapeutics

Yeah. Thanks. Thanks, Hannah, for the questions. Emily, you wanna take that?

Emily Hill
CFO, PTC Therapeutics

Yeah, sure. I'm happy to take the question. Thanks. We're looking forward to our guidance for 2023 of $940 million-1 billion. That obviously reflects continued growth expected in the DMD franchise. As you alluded to, also growth in Upstaza, Evrysdi, both royalty and milestone. There's a $100 million milestone expected for crossing a sales threshold for Evrysdi, and then continued contribution of Tegsedi and Waylivra. We haven't broken out specifically the contributions of Upstaza and Evrysdi, but obviously, you know, you can see now that Roche has Evrysdi approved in over 90 countries, quickly becoming the standard of care in SMA, and we expect significant growth going into next year.

Hannah Adeoye
Equity Research Analyst, JPMorgan

Okay, that's helpful. Just moving on to APHENITY, thanks for providing updated data from the run-in portion. Just wondering if you're able to speak to the variance of blood phenylalanine lowering that you were seeing in that run-in study. Should we expect any stratification mechanisms or criteria in place based on magnitude of Phe reduction as part of the phase II patient randomization?

Stuart Peltz
CEO, PTC Therapeutics

Yeah. Yes, I think that's a good point. I mean, one of the things that we always say is that the nice thing about this endpoint is it's a biochemical marker, so we measure the amount of phenylalanine, and it's a relatively stable measurement. Matt, you wanna talk a little bit about the stratification and the measurement?

Matthew Klein
COO, PTC Therapeutics

Yeah, absolutely. Hannah, thanks for the question. You know, first just, you know, obviously we're really excited about the updated Part One data. I think from what we reported in January, we are seeing the overall response rate up from 61 to 65% and the magnitude of free reduction for both the non-classical and classical PKU patients is also higher, which continues to give us a lot of confidence going into Part Two. In terms of your question about genetic variants, I believe that was your question. The enrollment includes really the full spectrum of genetic variants, non-classical and classical. We didn't do any specific stratification or exclusion based on any specific genetic subtypes. In terms of the stratification for Part Two, we did stratify the randomization for above and below 600 micromole per liter.

That was the one strata, as well as stratifying for greater than 30% response in the run-in phase and 15%-30% response in the run-in phase. Of course, the greater than 30% population being the primary analysis population for the study.

Hannah Adeoye
Equity Research Analyst, JPMorgan

Within the greater than 30% patients who are moving on to the primary analysis population, should we assume that there's no further stratification based on what was seen in the run-in portion?

Matthew Klein
COO, PTC Therapeutics

Correct. We predefined the strata as greater than 600 at baseline from below 600 at baseline as they enter the placebo-controlled phase.

Hannah Adeoye
Equity Research Analyst, JPMorgan

Great. Maybe just one more, if I could. Just wondering about the need or the interest in over-enrolling the study relative to your initial study design? Wanted to know if that was born out of feedback from any regulatory agencies?

Stuart Peltz
CEO, PTC Therapeutics

Yes. No.

Matthew Klein
COO, PTC Therapeutics

So it was-

Stuart Peltz
CEO, PTC Therapeutics

Oh, go ahead. Go ahead, Matt.

Matthew Klein
COO, PTC Therapeutics

Yeah. That had nothing to do with regulatory interactions. It was agreed upon. The protocol was agreed upon with the FDA and EMA prior to the start of the study. This really reflected significant interest on the part of the patients and the physicians. I think as we've talked about this, you know, clear unmet medical need and desire for safe and effective therapies, and what we saw was just really significant interest from centers throughout the world. As the over-enrollment and the delays in getting to data really come from the fact that at the end, there was still a large number of investigators, PKOLs, who had patients they really wanted to get into the study. Of course, we believe that the greater number of patients only strengthens or heightens that probability of success in the trial.

Hannah Adeoye
Equity Research Analyst, JPMorgan

Okay, very helpful. Thanks for taking the question.

Operator

Thank you. Our next question comes from Kristen Kluska with Cantor Fitzgerald . Your line is open.

Kristen Kluska
Managing Director, Cantor Fitzgerald

Hi, everyone. Thanks for taking my questions, and congrats on the 25-year milestone. First question I had was for PKU, can you give us your sense or preliminary thoughts on what the payer's response might be, whether there might be a generic Kuvan step edit or perhaps how it could differ across different populations such as those with classical?

Stuart Peltz
CEO, PTC Therapeutics

This, you know, I think this is a good point, and I think it's unique to remember is that while Kuvan, you know, was the first drug, it had a large patient population that it was ineffective to. What we see is that approximately, if you look at maybe Palynziq and Kuvan together, it's still probably close, but not exactly 10% of the overall population. You have a huge patient population of patients that are not satisfied with the current treatments, right? There's 58,000 PKU patients globally. That makes it a really pretty significant opportunity to be able to, you know, bring these, to bring a new therapy, that we believe is highly effective.

You could see that, you know, getting 60%, over 65% in the overall patient population and 61.5% of the classical population, they're nearly the same, just showing you how effective it is when you consider what PKU, what Kuvan was before was it didn't even function on classical patient. We think, you know, it's pretty clear that this is a superior product and there's so many patients where the drugs were ineffective that we think we're in a really good spot for this. We don't think, we don't expect any step edit for classical PKU because it was so well known that it, Kuvan didn't hit it.

Even if there is step edits for patients to walk through Kuvan, there's already a fair number of those patients who've already tried and failed Kuvan, and it's been well documented. Even if they, even if they haven't, it's a very short period of time to show that it is or isn't functional. I think that, you know, you have a real, you know, it I don't think this is gonna be cumbersome or difficult to be able to handle. Kylie, you have anything to say also on... You've done a fair bit of work on payers.

Kylie O'Keefe
Chief Commercial Officer, PTC Therapeutics

Yeah. Thanks, Kristen, for the question. I think it's a really important one. As Stu said, we really do believe in the substantial unmet need that exists in the PKU marketplace. As Stu was talking to, we've started to begin a number of different payer engagements to ensure we understand sort of how they're looking at a data package. From that perspective, as Stu was saying, if you look at the classical PKU patients, Kristen, there has been no effective therapies in that space. From that perspective, we don't foresee any types of step edits or requirements to be able to put these patients on treatments.

As Stu was also saying, in the space where they've previously tried Kuvan, even if there were step edits or generic first plans in the cases of Kuvan being generic, again, we don't see this as a major hurdle because in many cases, they've tried and failed Kuvan, and therefore the documentation has been established. Even if it needed to be reestablished, it is a quick and efficient step in the sense that it's a blood-based biomarker. You're able to put the patients on treatment, establish that the treatment isn't working and move them on to a more effective therapy. From that perspective, we're very confident going into the commercial landscape that we have the right data set and the right data package, assuming success with APHENITY to hit the ground running.

Stuart Peltz
CEO, PTC Therapeutics

We don't look at this like as if we're competing with a generic. We're competing with a drug that had a very small window of patients to treat, of most of which, the patients weren't successful. We plan on bringing it's in a sense, a new therapy that these patients, we anticipate will have, will be more successful on this therapy. It's very different than fighting with a, you know, You just have a generic, and you're trying to fight to get a piece of that pie. We actually believe that we'll be able to treat patients that weren't able to be treated before.

Kristen Kluska
Managing Director, Cantor Fitzgerald

Okay. Thank you, Stu and Kylie. I think of your late-stage candidates, MDAS perhaps gets less attention compared to especially like PKU and Huntington's Disease . Maybe can you reiterate for us why you remain excited about the program potential here? How you think about the commercial opportunity and ease of finding some of these patients should it be successful and ultimately approved? Thank you.

Stuart Peltz
CEO, PTC Therapeutics

Yeah, we think vatiquinone is a very important new therapy, in part because it really does tackle a new area in terms of treating medicine, that is really sort of mitochondrial dysfunction and the consequences of that. When you think about mitochondrial dysfunction, when you think about the, you know, the amount of ATP that's produced in order to be functional, you know, it's almost like 50 ATP molecules a second. If things go awry during that, and you have dysregulation and enhanced free electrons, that obviously can cause all sorts of stress on the cell. That can cause havoc and obviously neuroinflammation and things like that. The consequence of that is big.

When you think about especially, you know, like in the brain, where, you know, it's only a 3-pound organ, but it uses about 20% of the overall ATP within the body. It could cause dramatic effects, and you can see that with mitochondrial disease, with associated seizures. I think, having a drug that can modulate this and through novel and new mechanisms is quite important. We're excited about that because it could be used really quite broadly. Matt, you wanna talk a little bit about MIT-E and why we're so excited about this?

Matthew Klein
COO, PTC Therapeutics

Yeah, Kristen, thank you again for the question. Look, while maybe it's not getting as much attention, this is a population that's, you know, known. There's over 20,000 patients worldwide with Mitochondrial Disease Associated Seizures. As Stu mentioned, this is just the beginning of populations that could benefit from a drug that targets these fundamental oxidative stress and inflammation pathways that are causes of disease. We have confidence in the study. It's built on a number of previous studies showing that we can have an important effect on seizure activity, both in terms of seizure frequency and other seizure-related morbidity. We believe that this can be a very important therapy, not only for mitochondrial disease patients with Fragile X, but many others.

Kristen Kluska
Managing Director, Cantor Fitzgerald

Thank you.

Operator

Thank you. Our next question comes from Brian Abrahams with RBC . Your line is open.

Brian Abrahams
Managing Director, RBC

Hey, guys. Thanks for taking my question. Stu, my congratulations as well on 25 years.

Stuart Peltz
CEO, PTC Therapeutics

T hank you.

Brian Abrahams
Managing Director, RBC

I was wondering if you guys could expand a little bit more on the nature of your discussion with the agency on Translarna? I'm curious to learn a little bit more about, I guess, what their initial reactions were to the full 041 data plus the STRIDE registry? What seems to be the sticking point? I guess what gives you confidence that dystrophin and some of the other analyses would support approval? Is this something that would be a potential accelerated approval, perhaps? Thanks.

Stuart Peltz
CEO, PTC Therapeutics

Yeah. yeah, we recently had a informal discussion that will allow us to lead to setting up a meeting with them. It really was the notion of us talking about the overall package and the mechanism of action, as well as why we think we have clinical benefit as a consequence of that. Matt, you wanna go through this a little bit?

Matthew Klein
COO, PTC Therapeutics

Yeah, sure. Brian Abrahams, thanks for the question. Just to take a step backwards, as I think most of you recall, after we had the 041 data, we had requested a Type C meeting with the FDA to discuss 041 as well as STRIDE and the pooled analyses from including Study 007 and Study 020. The agency informed us that we would have a meeting with written response only. We had asked to be able to have a live meeting given the volume of data, and they said that they would provide written response only comments, but we would have the ability to talk to them afterwards if we still had questions. Obviously, we did have questions after the initial feedback, which seemed to focus mostly on Study 041 itself not meeting the bar of substantial evidence of effectiveness.

Clearly, there's evidence of benefit in that study and when combined with Study 007 and Study 020 to see highly statistically significant and consistent improvement on the key functional endpoints of disease and then as you mentioned, also the STRIDE registry. This meeting was a live meeting offered as a clarification of the comments that were made in the Type C written comments. Again, a lot of that discussion was about why Study 41 wasn't believed to have substantial evidence of effectiveness.

We talked about totality of data. It was suggested that we could request a separate Type C meeting to discuss totality of data, including the mechanistic dystrophin data because the comments in our meeting was made that we hadn't yet shared those data which as you all know we had those data but actually focused on the functional benefit that was in 041 and came afterwards. We see this as an opportunity to again highlight not only 41 but 41 alongside the other placebo-controlled studies from the STRIDE registry, how the benefits we've demonstrated in the course of a clinical trial are translating into long-term meaningful benefit as far as delaying the key morbid transition states of the disease, loss of ambulation or loss of pulmonary function.

Bring in all the mechanistic data we have from Study 045 and the laboratory data as well, which really confirms that we have a novel mechanism of action in terms of nonsense suppression, and that's yielding dystrophin production which is also associated with the clinical benefits recorded in all of these studies.

Brian Abrahams
Managing Director, RBC

That's really helpful. Thanks so much. If I could just squeeze in a quick follow-up on the PKU program. I think the ways to measure phenylalanine levels in modern studies are more reliable. I was wondering if you could maybe just clarify the way Phe is being measured in the phase III relative to the Kuvan studies, and your confidence that the assessment of Phe is repeated or robust enough such that you wouldn't have pseudo responders whose reductions might drop off between the open label run-in and the randomized portion as had happened with some of the old Kuvan studies? Thanks.

Stuart Peltz
CEO, PTC Therapeutics

Go ahead, Matt.

Matthew Klein
COO, PTC Therapeutics

Yes, sorry. Brian, we're using a blood spot analysis that's done at home. This has been very well validated as a robust measure. I think that we have confidence that obviously we're using the same methodology in both the run-in phase and the placebo-controlled phase. It's important to note the way that we measure these Phe responses, which in the run-in phase are treated for 14 days, but we're averaging three different time points, five, 10, and 14 days, which gives us the value of reduction. It's averaged over three points, which is another effort to ensure we're getting an accurate and precise assessment of the Phe reduction. This is a method that's been well designed, well validated. We have a GLP laboratory consistent measurement in both the run-in and the placebo-controlled phase.

I can't comment on specific differences to the methodology that was used, with Kuvan, but I can provide the confidence that we have a very well, validating method that can provide both accurate and precise assessment of the Phe, changes over time.

Brian Abrahams
Managing Director, RBC

No, that's super helpful. Thanks, Matt.

Operator

Thank you. Our next question comes from Joseph Thome with Cowen . Your line is open.

Joseph Thome
Managing Director and Senior Equity Research Analyst, Cowen

Hi there. Thank you for taking my question. Maybe just one. We're gonna see some registrational data sets here in the first half, which is great. Hopefully, some of these are, or all of them are successful. As you did, you know, bring these in, is there anything else that you would need outside of the registrational data before a regulatory submission? Essentially, can you just comment on your comfort with the CMC as it stands right now, and the size of the safety database for, sort of the next three that are coming up here? That would be great. Thank you.

Stuart Peltz
CEO, PTC Therapeutics

Yeah. Matt, you wanna take that?

Matthew Klein
COO, PTC Therapeutics

Yeah, sure. Thanks for the questions, Joe. Obviously both compounds, sepiapterin for PKU as well as vatiquinone have been in development for a number of years, which has really given the opportunity for the other components of the package when you think about CMC and you think about non-clinical clin pharm for those portions of the package to get filled out, right? We obviously are conducting a fairly large study in PKU now with sepiapterin, and we believe based on this trial and the other data that have been collected in other sepiapterin studies that we'll have the sufficient database to support submission with a positive trial.

With vatiquinone, I think one of the really foundations of that therapy is the extensive safety record that's been recorded in kids over the past decade, including patients who've been on drug continuously for over a decade with very strong safety profile. Taken together for both therapies, we believe we have all the components of the package. Obviously, with positive data, we'll meet with the agency to align on the details of the NDA submission, and then move forward as quickly as possible.

Joseph Thome
Managing Director and Senior Equity Research Analyst, Cowen

Great. Maybe just a quick follow-up, maybe on the financial side. In terms of the financial spend guidance for 2023, is there any additional build in the U.S. marketing force anticipated this year, or would that be more of a 2024 spend item? Thank you.

Stuart Peltz
CEO, PTC Therapeutics

Yeah, yeah, Emily?

Emily Hill
CFO, PTC Therapeutics

Yeah, sure. I'll take that one on the spend side and then if commercial wants to add anything on the infrastructure. We're pretty well sized on the commercial force, so there's no significant change in the spend on the U.S. sales force.

Joseph Thome
Managing Director and Senior Equity Research Analyst, Cowen

Great. Thank you very much.

Operator

Thank you. Our next question comes from David Lebowitz with Citi. Your line is open. David Lebowitz with Citi, your line is open.

David Lebowitz
Managing Director, Citi

Sorry, I. The name fell out for a moment, so I missed it. I guess, question number one on the PTC923 data, how should we benchmark response rate compared to Kuvan, given that patients were on a Phe-restricted diet, which would be expected to deepen the overall response?

Stuart Peltz
CEO, PTC Therapeutics

Yeah. I think what we're asking for is for people, whatever diet's on, that they keep a consistent diet of what they're on. You know, I think overall what you're seeing within the results are pretty dramatic results of greater than 60%, both in the classical as well as the other forms of PKU. I think you're seeing consistent activity of the molecule. I feel we're in a... If it's deeper in the other way, at least here, I think you're still seeing pretty high response rate. Matt, you have?

Matthew Klein
COO, PTC Therapeutics

Yeah. I think in general.

Stuart Peltz
CEO, PTC Therapeutics

I think you all are.

Matthew Klein
COO, PTC Therapeutics

Yeah. You know, thank you for the question. In general, these patients all tend to be on feed restricted diets, and the key in both studies obviously is to have them on consistent diets that's not a confounding variable. I think what we're seeing in terms of differences in magnitude and effect is quite impressive. If you look at the phase I, which was the Kuvan responder study, where they recorded a greater than 30% change in 20% of the patients, obviously now we're looking at 65% in this study. I think this is, you know, clearly a much higher response rate. Again, what we've talked about is really what you'd expect from a more bioavailable and co-potent cofactor, and obviously in the, in the face, as you said, of a continuous diet.

David Lebowitz
Managing Director, Citi

Thank you for that. Do you expect to specifically report a response rate for classical PKU patients?

Stuart Peltz
CEO, PTC Therapeutics

Yeah, you mean overall? At the end of the day, yeah, we'll break that out as well.

Tazeen Ahmad
Managing Director, Bank of America

Excellent. Thanks for taking my question.

Operator

Thank you. Our next question comes from Kelly Shi with Jefferies. Your line is open.

Kelly Shi
SVP and Senior Research Analyst, Jefferies

Thank you. So for MIT-E data now in Q2, could you help to set an expectation on what kind of reduction of the seizure frequency would be considered clinically meaningful? What other measures we should also focus on to evaluate the clinical benefit of vatiquinone. Lastly, given that a mitochondrial disease is a very heterogeneous disease, would you expect some groups of patients with certain like genotypes to see greater benefit, based on the mechanism of action of vatiquinone? Thank you.

Stuart Peltz
CEO, PTC Therapeutics

Sure. Hey, Matt, do you wanna take that?

Matthew Klein
COO, PTC Therapeutics

Sure. Thank you again for the question. When we talk about benefit in these patients, you know, first we have to think about the disease itself. Obviously, mitochondrial disease-associated seizures are a highly morbid and common aspect of the disease. About half the patients with mitochondrioses have seizures, these seizures don't tend to respond to typical antiepileptics because the typical antiepileptics don't target the energetic pathways that cause seizures in these patients. In fact, many of the traditional antiepileptics are mitochondrial toxins, they actually make the disease worse. These kids have seizures that are refractory to typical meds. They can have tens, hundreds, even up to thousands a month. You know, high seizure volume.

It's a highly morbid aspect of the disease, which frequently leads to aspiration pneumonia and other infections and often can be the cause of death for these patients. When we think about meaningful reduction, you know, most of the physicians we speak to think that even a 20%-25% reduction in seizure frequency in these patients can be important. We've powered the study for a 40% differential reduction between the treatment group and placebo group with a hypothesized reduction of 50% in seizure frequency in the active population and 10% in the placebo population. In terms of differences between genotype and response, you know, given the fact that vatiquinone is targeting 15-lipoxygenase, which is a common response pathway, outside of the mitochondria, the treatment effect should be agnostic to underlying genotype.

And might there be other patient characteristics such as age and stage of disease that could contribute to differential therapeutic response? That's possible. One of the things we've observed in previous studies is there's no specific relationship between genotype or disease subtype and response. Again, because we're targeting an element common or response pathway common to all different causative genotype defects.

Kelly Shi
SVP and Senior Research Analyst, Jefferies

Thank you. Super helpful.

Operator

Thank you. Our next question comes from Tazeen Ahmad with Bank of America . Your line is open.

Tazeen Ahmad
Managing Director, Bank of America

Hi, good evening. Thanks for taking my question. Maybe one point of clarification for Translarna. I think, Stu and Matt, you've talked about the totality of data as being the premise for a lot of your discussions recently with the agency. I guess as it relates specifically to dystrophin, if the agency looks for dystrophin as part of the package, can you just remind us when the last time dystrophin was measured in any of your trials to date and how many patients worth of data you might have on that?

Stuart Peltz
CEO, PTC Therapeutics

Yeah, sure. You gotta remember also the dystrophin was when we measured it, we measured it in Study 004, which was the first, you know, study that we did to take a look to see its proof of concept studies where we showed. That's a published paper, where we showed that you saw increased levels of dystrophin. It was a small study, I think. I don't know, 15, 16 patients, somewhere around there. We did Study 045. We did it again, Study 045. That was, how many patients was that, Matt? Do you remember?

Matthew Klein
COO, PTC Therapeutics

We had 20 overall, and there were 18 in the analysis population.

Stuart Peltz
CEO, PTC Therapeutics

Yeah.

Tazeen Ahmad
Managing Director, Bank of America

Okay.

Stuart Peltz
CEO, PTC Therapeutics

we have those

Tazeen Ahmad
Managing Director, Bank of America

Yeah

Stuart Peltz
CEO, PTC Therapeutics

Of patients. We have, obviously from a clinical point of view, studies from you know, Study 007, Study 020 and Study 041 with you know, large number of patients where, you know, in the ITT population and especially in 41, we saw clinically significant results. Not only was it as Matthew Klein had said before, that not only was it positive there, but it was also positive in the North Star, the time function test. That was true also in Study 020. As well as multiple endpoints in Study 007. There's a large body of data that demonstrates Translarna's activity in terms of treating patients.

That's then consistent with the STRIDE registry that we've done where we've looked at hard endpoints such as loss of ambulation, loss of getting off, being able to get off, you know, to stand from the ground and loss of pulmonary activity. All those results demonstrating that you preserve both the ability to walk, to preserve the ability to get off from the ground and by years and preserve the ability to preserve pulmonary function. You put all that together. I frankly, I have not seen a better clinical package than the one we have. We believe it's pretty clear that patients benefit from it. You can see that patients have been on it for now quite a long time.

We believe, you know, we have patients from, obviously from around the globe getting Translarna. We only think it's appropriate and fair that we should work towards getting patients in the United States this drug. What we're really asking for is, look, we'd like to, you know, we think that we have a strong package. Let's review it. Let's evidence advisory committee, you know, at least give us our, give the patients and their families a fair hearing so that the folks who've been, and frankly, many of them have been on it for over a decade now, that they, you know, that to give them their due on what we think is a highly active drug.

Tazeen Ahmad
Managing Director, Bank of America

Thanks for all of that color. I mean, at this point, what do you think needs to happen to get the agency over the finish line for them to say that you should apply for approval? Have they looked at all of this data already as part of your written interaction?

Stuart Peltz
CEO, PTC Therapeutics

Yeah. Look, what we think is we've had years now of working with the agency and not talking to them. It's not just us. It's been the whole community has only had written discussions. On complicated results, with a large body of data, where, you know, and they have plenty of new people there who may not understand the whole picture and have a whole discussion. Not to actually I simply don't understand this, not to have interactions where you have communication and you talk through it. Just like everything else in that we do in life, you need to be able to go back and forth to give points of view that. That's how you change people's minds or at least have a shot at it. One doesn't have an easy shot at it if it's every three months you get to write a response back to questions.

Tazeen Ahmad
Managing Director, Bank of America

Right.

Stuart Peltz
CEO, PTC Therapeutics

We think that at least what we need to do is have a conversation and see where that goes.

Tazeen Ahmad
Managing Director, Bank of America

Okay. Do you think that that'll be sooner rather than later, or do you have to wait that extra three months just to schedule it?

Stuart Peltz
CEO, PTC Therapeutics

It takes time. You know, this is the nature of regulatory discussions. You put it in, there's time for them to get, fit you in.

Tazeen Ahmad
Managing Director, Bank of America

Right. Okay. Got it. Thanks for that. Appreciate it, Stu.

Operator

Thank you. Our next question comes from Gena Wang with Barclays . Your line is open.

Gena Wang
Managing Director in Biotech Equity Research, Barclays

Thank you for taking the question. I have two questions regarding APHENITY study. First is just clarification. Regarding the 156 patients, were these patients actually passed 50% Phe reduction, screening test, or was that 156 patient is a total patient that you screened? If it's, 156 patient is a passed 15% Phe reduction, what is the total patient number you screened?

Stuart Peltz
CEO, PTC Therapeutics

Matt, do you wanna take that one?

Matthew Klein
COO, PTC Therapeutics

Yes, sure. Hi, Gina. The 156 refers to all those who went through screening and then completed the run-in phase. That's 156 subjects who were received two weeks of sepiapterin. Of those 156, 102 or 65% had a greater than 30% reduction.

Gena Wang
Managing Director in Biotech Equity Research, Barclays

Out of 156, how many of these achieve 15% fee reduction?

Matthew Klein
COO, PTC Therapeutics

We said 102 had over 30% and 13 had between 15% and 30%. In total, that would be 115 or about 75%, 74%, 75% had 15% reduction and above. Obviously far and away, the majority of those, 102 of those were greater than 30% reduction.

Gena Wang
Managing Director in Biotech Equity Research, Barclays

Okay. Very good. Very helpful. My second question is, can you remind us the rationale of dose escalation with two weeks each of a 20 mg, 40 mg, 60 mg for the part two study?

Matthew Klein
COO, PTC Therapeutics

Yeah, sure. One of the things we're studying, obviously that the agency always likes to understand, is exposure-response relationships. By doing the two weeks at 20 milligrams per kilo, two weeks at 40 milligrams per kilo, two weeks at 60 milligrams per kilo, we can have a very nice curve and understand the relationship between exposure and response, which is important for regulatory purposes. We believe the dose will be 60 milligrams per kilogram, and we're also very confident that two weeks is sufficient to understand what the effect at each dose level will be.

Gena Wang
Managing Director in Biotech Equity Research, Barclays

Thank you very much.

Operator

Thank you. Our next question comes from Jeff Hung with Morgan Stanley . Your line is open.

Mike Riad
Equity Research Associate, Morgan Stanley

Hi, this is Mike Riad on for Jeff Hung. Thank you for taking our questions. First one, once the upcoming APHENITY data read out in May, can you remind us how you're thinking about the cadence and timing of regulatory events? We have a follow-up after that.

Stuart Peltz
CEO, PTC Therapeutics

Sure. You know, our goal is, you know, we'll get the results. Based on that, we'll obviously report out the results so publicly. As rapidly as possible, have set up meetings and get ready to do an NDA for the product and get ready, you know, for regulatory guides as fast as possible. You know, obviously we'll do a pre-NDA meeting, and while we're doing that, we'll, you know, be getting all the documents ready to go.

Mike Riad
Equity Research Associate, Morgan Stanley

Awesome. Thank you so much. My second question for the vatiquinone phase II /III MIT-E data, they were expected this quarter, but they're now in the second quarter. Can you talk about any factors that led to the adjustment and timing? Thanks so much.

Stuart Peltz
CEO, PTC Therapeutics

Yes. I think it's just finishing up the last patient up. Matt, do you have any thoughts on this?

Matthew Klein
COO, PTC Therapeutics

Yes, it's, Yeah, Michael, it's really a question of having now knowing exactly when that last patient last visit is gonna be, which is gonna be in March, and then having sufficient time to do all the database cleaning, the database lock in, and getting to data. It's really refinement of the timeline now that we know the definitive last patient last visit date.

Mike Riad
Equity Research Associate, Morgan Stanley

Awesome. Thank you.

Operator

Thank you. Our next question comes from Paul Choi with Goldman Sachs . Your line is open.

Paul Choi
Biotechnology Analyst, Goldman Sachs

Hi. Thank you. Good afternoon, and thank you for taking our questions. I have two pipeline questions. First is on APHENITY. Can you just maybe elaborate on the updated timing from May of this year versus your prior guidance? Can you maybe speak to any geographical differences with regard to practice and clinical treatment of PKU patients in the US versus OUS that we might look for as you top line the results later this year?

Stuart Peltz
CEO, PTC Therapeutics

Sure. I'll just take the first one. I think we've talked about this. The refinement of the timing of when we would complete the trial had a lot to do with just, you know, there were a lot of patients at the end of the when we were nearing ready to close the trial. What we decided to do is, and it was a number of people that we wanted to make sure that some of their patients got in, some of the KOLs and would be able to do that. As such, we actually brought in more than we thought we would, and that extended the timeline that led to us getting the results, which we think now by May.

Everyone's in the trial now, we were able to give a pretty refined time on when we would be able to complete the trial. We feel pretty good about now that we know exactly where we're at, when we'll complete the trial. In terms of the geographical differences, you know, Matt, any comments you wanna make on that?

Matthew Klein
COO, PTC Therapeutics

Yeah, you know, Paul, we really don't expect geographical differences. While there may be different guidelines in terms of target Phe reduction region to region, the practice is fairly consistent worldwide. Obviously this is a disease where the cornerstone of management is, for now, diet modification that starts at birth. Newborn screening is in place in many places around the world. We can certainly look at whether there's differential response based on geography, but it's not one that we would expect a priori.

Paul Choi
Biotechnology Analyst, Goldman Sachs

Okay. Thank you for that. As a follow-up on PTC518 for Huntington's, can you maybe comment or update us on what feedback or data you've provided to the FDA and just, you know, what your current expectation is for getting the clinical hold lifted there?

Stuart Peltz
CEO, PTC Therapeutics

Yeah, sure. I think, you know, as we've discussed in the past, our goal, you know, is to share with them some data that we're getting with current patients and go back to them on that with that, which, you know, we will be doing. We think that, you know, so it's having enough clinical data on the set of patients that we can then go back and talk to them on. That's what we're doing in terms of that. You know, we've opened up obviously, a fair number of sites around the globe. You know, patients are coming in. We even expanded to take an additional cohort of patients. So we feel pretty good about bringing them in.

We'll, you know, we'll bring in at some point, you know, when we have a set of data that we'll go talk to the FDA about and show them that we're in pretty good shape. You know, just to remind everyone, we're doing the 5 mg and 10 mg data that will then we'll be able to go to the 20 milligram data, and we'll be able to bring forward data to the FDA at some point, so we open it up in the U.S. That's our game plan.

Paul Choi
Biotechnology Analyst, Goldman Sachs

Okay. Thank you. Congratulations on 25 years.

Stuart Peltz
CEO, PTC Therapeutics

Thank you.

Operator

Thank you. Our next question comes from Danielle Brill with Raymond James . Your line is open.

Danielle Brill
Biotechnology Research Analyst, Raymond James

Hi, guys. Good evening. Thanks so much for the questions. Just a couple clarifying ones for me. I think, last month at JP Morgan, the unaudited four key revenues for Upstaza were $13 million. Is that number still accurate? Should we be expecting the spillover from the $20 million-40 million you previously guided for in Q4 to be reflected in Q1? Just a clarification on Translarna as well. The Type C meeting that you plan to request, will this one be in person, or are you expecting just a written meeting as well? Thank you.

Stuart Peltz
CEO, PTC Therapeutics

Yeah. Thanks. Thanks for the question. Let me take Translarna up. We anticipate this to be a means where it will have conversation, so it's not gonna be, it's not gonna be written. I believe it's gonna be a Zoom call. Isn't that right, Matt?

Matthew Klein
COO, PTC Therapeutics

We'll request a live interaction, obviously, and I know that the agency has now started having in-person meetings again. The exact details, Danielle, whether this is Zoom, whether it's phone, whether it's live, whether they wanna do it another way, obviously it'll be up to them, and we'll know better once we submit the request and get their response.

Stuart Peltz
CEO, PTC Therapeutics

Yeah.

Matthew Klein
COO, PTC Therapeutics

Obviously, we would be happy with in-person. We believe that's the most effective form of discussion, but, you know, obviously this is gonna be up to the agency and their schedule.

Stuart Peltz
CEO, PTC Therapeutics

Yes. In terms of, obviously the patient finding, you know, in terms of the Q1, obviously, you know, most of what we do is focused on identifying and treating patients. We, you know, certainly we remain confident that we want to move those in. In terms of the numbers, I don't think there are any changes in the 2022 numbers. We'll probably provide more color about how we're doing. You know, we're very early within the launch, right? I think we'll be able to provide more color on the at each of the quarterly calls. You know, certainly at the Q1 earnings call, we'll provide more color on that. Kylie, you have anything else to add to that one?

Kylie O'Keefe
Chief Commercial Officer, PTC Therapeutics

Thanks, Stu. Yeah. As he said, Danielle, there is no changes to the number for Upstaza from unaudited to audited. As Stu said, we're continuing to focus on patient identification and continuing to focus on securing pricing and reimbursement in a number of different countries across Europe, as well as we talked about in January, focusing on looking at 9 patient programs outside of Europe. That's continuing according to plan. As Eric mentioned earlier, we're seeing strong engagement with payers across a number of different HTA bodies, and we look forward to being able to continue that pricing and reinvestment step to treat more patients in this. We plan to provide more updates at upcoming quarter earnings.

Danielle Brill
Biotechnology Research Analyst, Raymond James

Understood. Helpful. Thank you.

Operator

Thank you. Our next question comes from Robyn Karnauskas with Truist . Your line is open.

Alex Xenakis
Equity Research Associate, Truist

Hi, this is Alex in for Robyn. We had a question on if there had been any updates into the patient findings for patients identified for AADC for Upstaza, but it sounds like we're all gonna wait till the first quarter to get some more results on that. Correct me if I'm wrong. We also wanted to know, turning towards the U.S., can you remind us of the pre-launch initiatives that are ongoing for Upstaza and what additional initiatives may still be needed as we approach BLA submission and anticipated future launch? Thanks.

Stuart Peltz
CEO, PTC Therapeutics

Yeah, sure. Eric, you wanna take that one?

Eric Pauwels
Chief Business Officer, PTC Therapeutics

Yeah. Yeah, sure. Thanks, Alex, for the question. You know, currently are seeing the dynamics in Europe, but we're also preparing for the launch of Upstaza in the U.S. In a similar way, we have a dedicated team that's actually doing that. We have focused on a number of key areas, including we've accelerated disease awareness. We have a number of key programs, including advisory board symposium and publications, key publications and peer review that have been in English, it's also U.S.-based journals.

We're talking to payers as well in the U.S. and preparing for this launch. We're talking to a number of key payers about the design because we know that there are gene therapy currently approved in the U.S., but many of them are replacing standards of care. Will be the standard of care. We're taking an approach to really understand how the payer view will be on this. We have accelerated a number of patient finding activities, particularly in the high enriched populations.

In looking at very... and also ethnic type groups. We have already. Our target is to prepare somewhere between seven and 10 surgical centers to be ready at the time of launch. Importantly, this will be this will be timed, and these centers will be timed with the time of launch, we'll be able to work very closely to bring these patients in. Overall, I think we're very pleased with the progress we're making outside of Europe, but we're also sharing a lot of the knowledge from the launch itself in Europe. We're sharing that continuous learning and execution that we have with the U.S. market. Following the BLA approval, we'll be ready to launch the product in the U.S.

Alex Xenakis
Equity Research Associate, Truist

That sounds great. Also on the same note, now that there have been patients treated, you know, in the real-world setting, do you find that the clinical results, I guess, still early clinical results that you're seeing and details along with the procedure match that of what you saw in the clinical trials, or are there any key differences to note? Thanks.

Stuart Peltz
CEO, PTC Therapeutics

Yeah, I know we're. Look, the nice aspect of AADC deficiency and the gene therapy that we have is it's truly a transformational, a transformational therapy where, you know, as you're seeing that, you know, all of the patients perform better and there are patients that obviously, while they were growth arrested, you know, and weren't able to hold their head up, turn over, sit up, stand or talk, have changed. Clearly you can see some patients where, you know, we have one patient who speaks three languages. That's been exciting and we continue to see substantial improvement in these patients.

There's, you know, as we always say, there's nothing more gratifying, than, you know, being part, of a, of drug therapy and bringing it to patients and having such transformational effects on it. I think that's, you know, it's great for the family to see what it does for the families, the patients, and, for our own community for, you know, just being part of bringing it to them. We're excited about it, and it continues to be a transformational product.

Alex Xenakis
Equity Research Associate, Truist

Yeah, that sounds fantastic. Well, congrats, and thanks for taking my question.

Stuart Peltz
CEO, PTC Therapeutics

Yeah. Thanks.

Operator

Thank you. Our next question comes from Colin Bristow with UBS . Your line is open.

Yihan Li
Associate Director in Biotech Equity Research, UBS

Hi, this is Yihan on for Colin . Thanks for taking our questions. We have two clarification questions. The first one is on the PKU data. Congrats on the part one data. Could you please give us some more detailed colors on the primary reason for the top line delay to May? We know like you have already said a lot of stuff. It's just like for the part one, the enrollment was as planned, and it has a fixed timing endpoint. I'm just wondering what the, you know, the rationale behind it. The second question is on the PTC518 Huntington's Disease program. We are just wondering, have you heard any updates or more specific requirements from FDA yet? How long will it take to get the data?

In terms of XUS enrollment, have the high dose portion already started the enrollment? Could you please clarify on that? Thank you so much.

Stuart Peltz
CEO, PTC Therapeutics

I think if it was a little muffled. I think you're asking why is it in May? Was that the question? I think the answer, I think as maybe... Just so we're clear, the reason is it was at, you know, the end of the study really occurs when it's the last patient, last visit. You've completed that aspect of the study, and that's when all the patients are completed. You can then go and clean the data and ultimately get it analyzed. Really what happened is, at the end, there was a large number of patients at the end of the study that were going in.

That's always, in a way, a little bit of an air traffic control nightmare to be able to get, A, bring in as many patients as you can and close it as rapidly as possible. So, you know, so that makes it so and, you know, we're balancing, wanting to close the trial, but also wanting to make sure that patients got in and that, patients from multiple physicians get into the trial. So that we don't anger anybody because they weren't part of it, of the trial. That's always. That's, you know, it's always a little difficult sometimes to precisely land the plane at the time you think you're gonna do it. This one was, in particular, much more at the end, had lots of patients.

That's why the timeline moved from where we thought it would be to May. It's a little bit longer, but we've gotten a lot of the patients from people, you know, from all the key opinion leaders and investigators. At the end of the day, it was a small change, but well worth it because we have everybody in this study, and we feel good about it. I think that's, you know, at the end of the day, that's what we're comfortable with. I don't think, you know. Well worth the small amount of time change to get everyone in. That's. In terms of PTC518, you know, we're now collecting data.

We haven't said yet when we're gonna clean the data and go back to the FDA, we plan to do this, and when we do, we'll let everyone know what our plans are. We haven't done that yet. I don't think we've set it up to say when we're gonna complete that. Matt, anything else I have to say on that?

Matthew Klein
COO, PTC Therapeutics

I would just add a couple things, you know. Just as a reminder, right? This was feedback that came from the non-clinical data that we had submitted to the agency that was reviewed at the other agencies. As we've said, all the other countries have allowed us to start the study at 5-10 milligrams for a year and even start at 20 milligrams up to a year. The FDA simply asked for some additional data to support the dosing and duration that we wanted. As Stu said, we're in the process of collecting what we think will be the putative data to do that, which is clinical data. Real data from patients that can give them comfort for the dosing and duration we want in the US.

In terms of your question regarding the initiation of the higher dose, that 20-milligram cohort, that hasn't started yet. As we said, we wanna look at the data from 5 milligrams to 10 milligrams and really make a data-driven decision based on what we're seeing in terms of pharmacodynamic effect, that is reduction in peripheral HTT mRNA and protein, huntingtin protein reductions peripherally and the biodistribution in terms of CSF exposure. Once we have an understanding of what that looks like at 5 and 10 milligrams, we'll then be in a position to make a decision regarding initiation of the 20-milligram cohort. We look forward to having those initial 5 and 10 milligram data to help inform that decision in the near future.

Stuart Peltz
CEO, PTC Therapeutics

Great.

Tazeen Ahmad
Managing Director, Bank of America

Got it. Very helpful. Thank you.

Operator

Thank you. If there are no further questions, I'd like to turn the call back over to Stuart Peltz for any closing remarks.

Stuart Peltz
CEO, PTC Therapeutics

Okay. Thank you, operator. In closing, I'd like to thank all of you for joining the call today and your well wish for our 25 years. We're always excited about that. We're especially excited about where we stand today at PTC, where we have, you know, as you can see, strong and accelerating revenues from our product portfolio. We have four data readouts in the first half of 2023, including three registrational studies. Clearly we're firing on all cylinders, and we look forward to more updates for you over the coming months. With that, thank you for staying on and good evening.

Operator

Thank you for your participation. You may now disconnect. Everyone, enjoy the rest of your day.

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