Good day, and thank you for standing by. Welcome to the Ascendis Pharma COACH trial interim topline week 26 data. At this time, all participants are in a listen-only mode. After the speaker's presentation, there will be a question-and-answer session. To ask a question during the session, you will need to press Star one and one on your telephone. That is Star one and one, and you will then hear an automated message advising your hand is raised. To withdraw your question, you can press Star ome and one again. Please be advised today's conference is being recorded. I would now like to hand the conference over to your speaker today, Scott Smith, Executive Vice President and Chief Financial Officer. Please go ahead.
Thank you, Operator, and thank you, everyone, for joining us on today's call. Joining me are Jan Møller Mikkelsen, President and Chief Executive Officer; Aimee Shu, Executive Vice President of Endocrine and Rare Disease Medical Sciences and Chief Medical Officer; Sherrie Glass, Chief Business Officer; and Jethro Acuda, Chief Regulatory and Safety Officer. Before we begin, I would like to remind you that this presentation will contain forward-looking statements that are intended to be covered under the safe harbor provided by the Private Securities Litigation Reform Act. Examples of such statements may include, but are not limited to, statements regarding our continued development of TransCon CNP and TransCon Growth Hormone combination treatment, our pipeline candidates and expectations with respect to their costs, continued progress, potential commercialization success, our strategic plans, and our goals regarding our clinical pipeline, including timing and results of clinical trials.
These statements are based on information that are available to us as of today. Actual results may differ, could differ materially from those in our forward-looking statements, and you should not place undue reliance on these statements. We assume no obligation to update these statements as circumstances change, except as required by law. For additional information concerning the factors that could cause actual results to differ materially, please see our forward-looking statement section in today's press release and the risk factors section of our most recent annual report on Form 20-F filed with the SEC on February 12, 2025. On our website is a presentation that we'll go over, and the speakers will refer to the slides as they go through. I'll now turn it over to Jan.
Thank you, Scott. I will start on a high-level summary of the key findings on the COACH trial 26-week interim analysis that we announced in a press release early this morning here in California. After that, Aimee Shu will go more in-depth to all the different data. Just to remind you, COACH is a phase two trial. It has two elements: our once-weekly TransCon CNP and our once-weekly TransCon Growth Hormone in children with achondroplasia from 2- 11. It is the first-ever conducted phase two trial with the combination of these two products. Before I start, I would like to give you a little bit of perspective of what my own expectations are. Because if I look at untreated achondroplasia children and look at them on the growth charts, seeing them going around, talking with their parents, they have typical annualized growth velocity around 4.0-4.5.
When you compare to height Z-score, obvious reason they are around zero if they develop like a normal achondroplasia child. We saw in our trial, our pivotal trial with monotherapy, an increase in annualized growth velocity. We also saw a lot of positive effect beyond linear growth effect, why we have this unique product opportunity that is now under priority review, really as a background fundament for further treatment. We also wanted to explore the situation. Can we boost all the positive effect we saw with TransCon CNP? Because we will always need TransCon CNP, and I will come back to this. When I not focus on the positive benefit beyond linear growth, but just focus on linear growth, we saw a treatment benefit with monotherapy for moving annualized growth velocity up to 5.5-6. This is generally what you see after one year treatment.
When you look for 52-week achondroplasia-specific height Z-score improvement, it's about 0.3. When I now report the data today, I look on the group coming from the TransCon CNP-naive children that basically started immediately on the combination therapy and saw an annualized growth velocity of 9.1 centimeters. An improvement in achondroplasia-specific height Z-score about 0.53 over 26 weeks compared to what is typically seen with any kind of therapy that addressed the hyperactive tyrosine kinase 3, which are about 0.3 over one year, or as calculated for 52 weeks. I'm really impressed. This is really a boost to growth that we have seen.
When we take the other arm, that is the CNP treatment naive, and Aimee will tell about how long time they have been on treatment and other things like that, we saw an annualized growth velocity of 8.2 cm and improvement in height Z-score about 0.44 over the 26 weeks. Just remember, always look on the age of the children. They have difference, and that is always affecting some kind of the growth velocity. I believe this is a result of a new clinical benchmark for achondroplasia. We saw clearly that it was healthy growth. The linear growth was associated with improvement in body proportionality. Bone age advanced compared to chronological age. One thing I never thought that would happen, the combination therapy, TransCon CNP, TransCon Growth Hormone treatment exceed annualized growth velocity 97% of other average state of children.
In plain Danish or Scottish English, they are growing much, much, much faster than any of the best growing of a normal child. No patient dropped out, and safety and tolerability was really, when we look at the data, comparable to what we saw from the different monotherapy. Summary, week 26 data demonstrates the potential to boost growth three times about the observed CNP monotherapy in the same period. If you have an achondroplasia child, the survey are coming to the situation, "I need more growth." Also, need the effect beyond linear growth that you get with TransCon CNP. I need more growth. You can get a healthy growth by boosting again three to four years treatment in one year. I think that is pretty positive proposition.
I think more important, which are summarized in slide two, it basically moved to the situation science is really the key things in slide four. People have thought it was interesting. I talk about a car with a brake, a car with a speeder. I actually believe what we tried to do in slide four, try to take this simplified manner into the depth of our biological understanding. That was what we did in slide four. The basic principle is the same. When you have a hyperactive tyrosine kinase as you have in achondroplasia, partly in hyperactive tyrosine kinase and other things like that, you basically have a brake on specific part of the development of the speed of a normal bone. This is the brake.
When you release the brake, you really can see the huge stimulation effect on multiple parts of the bone development with growth hormone. Also, going back to the saying, yes, growth hormone has a limited effect when you have the brake on. Obvious. When you have the car sitting with a good brake on, you cannot press a speeder. You still see some positive effect by growth hormone treatment. Specifically, you see a durability of effect. I've seen 40, 50 children up to four, five years now, still positive effect without CNP. But what we do with the combination, we unlock the potential of the positive effect on TransCon Growth Hormone. I will stop now and move it over to Aimee that will start to go through all the data.
Thank you, Jan. Hi, this is Aimee. I will start on slide five, which depicts the design of the COACH trial. We enrolled a total of 21 subjects, including 12 who had not previously received TransCon CNP therapy. That is, they were treatment naive. These patients received a combination of TransCon CNP plus TransCon Growth Hormone together from the outset. That's represented in the purple line. This also includes nine subjects who had been receiving TransCon CNP monotherapy as part of a prior TransCon CNP clinical trial, accomplished or attached. For these subjects, TransCon Growth Hormone was added on top of their TransCon CNP. Today, we're here to talk about the week 26 interim analysis. The COACH trial is assessing a variety of endpoints, as you can see at the bottom of the slide. Here, we are reporting on annualized growth velocity, achondroplasia-specific height Z-score, and body proportionality.
I'll now turn to slide six. Slide six and seven show the baseline characteristics and demographics of the patient population enrolled in the COACH trial. The TransCon CNP treated cohort, reflected in green, was on average older, almost eight years old, as expected. Overall, the children enrolled were representative of the achondroplasia population and consistent with the demographics we have enrolled in prior studies. Again, the treatment naive cohort averaged age 4.67 years, just shy of five years old, and the treatment experienced just shy of eight years old. You see here, we have two-thirds boys, one-third girls. I'll now move to slide seven, where we show additional baseline demographics and characteristics.
One important thing to point out that is different between the two cohorts here is the growth benefit that is observed in the TransCon CNP experienced group, which is reflected in the higher achondroplasia-specific height Z-score at the COACH trial baseline. You see here in the green column, the children who have been on TransCon CNP monotherapy for an average of two and a half years at the 100 microgram per kilogram per week dose have now achieved a height Z-score of 1.28. This is where they are starting the COACH trial. Slides eight and nine contain information about safety. At the week 26 time point here, we have seen an excellent safety profile for the combination of the two therapies through week 26.
In fact, the safety and tolerability profile looks similar to what is observed with each agent individually, and the adverse events were generally mild in nature. Importantly, we saw no symptomatic hypotension and no fractures and no bone issues suggestive of overly rapid growth. There was one serious adverse event, and this was determined to be unrelated to study drug according to the investigator. Now I'll move to the efficacy results, which start on slide 10. This is the most exciting thing. What we see in terms of efficacy at week 26 is unprecedented in achondroplasia. We see an inflection in growth consistent across multiple endpoints looking at growth. Here on slide 10, represented in purple, is the treatment naive cohort, who again were on average 4.7 years old.
Here we saw an annualized growth velocity of 9.14 centimeters per year at week 26, representing an increase of 4.2 centimeters per year in growth velocity compared to baseline. This was statistically significant at P of 0.0063. The substantial improvement in growth velocity was commensurate with an improvement in achondroplasia height Z-score represented here on the right-hand panel, which is a secondary endpoint in the COACH trial. The achondroplasia-specific Z-score in the treatment-naive patients after 26 weeks of therapy was positive 0.99. This reflects a 0.53 increase compared to their baseline coming into the COACH trial. Again, highly statistically significant with a P value of 0.0009. Now on slide 11, this represents the nine children who were treatment-experienced with TransCon CNP, and they are represented in the green bars. It is very similar to what you just saw in the slide prior.
At week 26, these children who are on average almost eight years old had an AGV of 8.25 cm at 26 weeks, representing an increase of 3.1 cm compared to baseline. Again, highly statistically significant at P of 0.0006. On the right side of the screen or the right side of the slide, we see the achondroplasia height Z-score now up to 1.72 after 26 weeks of therapy, reflecting an increase of 0.44 compared to this group's baseline. Again, statistically significant. It is noteworthy that these treatment-experienced children had already reached a mean achondroplasia height Z-score of plus 1.28, represented in the gold bar there after a mean of 2.5 years on TransCon CNP monotherapy. Yet, they still accumulated a mean increase of 0.44 of a Z-score in just 26 weeks.
From these data, we can see that the addition of TransCon Growth Hormone demonstrated a boosted growth in children previously treated with TransCon CNP. Now I'll turn to slide 12, which is really helpful for contextualizing the efficacy data here at week 26. The blue lines represent the annualized growth velocity at the third, 50th, and 97th percentiles for children of average stature based on the CDC database. While the gray and black lines show the range of annualized growth velocity for children with achondroplasia. We have the two AGV normative reference ranges here represented on the same slide. For both the TransCon CNP treatment naive subjects and the TransCon CNP experienced subjects, at baseline, they were within the range observed for growth velocities of children with achondroplasia.
You can see here that the gray circle, the treatment naive children, were as expected right at the 50th percentile for children with achondroplasia. Whereas the gold circle, representing the treatment experienced children, average age almost eight, were already at the top percentiles of growth velocity for children with achondroplasia, again reflecting their multiple years of TransCon CNP monotherapy. The combination of TransCon Growth Hormone on top of TransCon CNP vaulted these children to a level of annualized growth velocity above that of average stature children in both cases. That you can see here in the purple and the green dots, which are both above the 97th percentile line for children of average velocity. This opens up the potential that for children with achondroplasia, that they would be able to achieve new possibilities for healthy bone growth with less comorbidity and fewer complications from their disease over the long run.
This brings us to the slide about body proportionality, which is on slide 13. Here we would like to show you that importantly, the linear growth we are seeing is aligned with significant improvements in body proportionality here, upper to lower body segment ratios in both the treatment naive and the treatment experienced subjects. This is a strong indicator for the breadth of the effect of the combination and the fact that we are achieving healthy bone growth. We know that body proportionality, specifically the healthy growth of the appendicular skeleton, that is the limbs, is of key interest to those living with achondroplasia. The U.S. Food and Drug Administration has also acknowledged that improvements in skeletal proportionality could mitigate complications of the condition. With this, I will now turn it back to Jan for the wrap-up.
Thanks, Aimee, for this walkthrough or this impressive data. For me, when I saw this data, I was really thrilled. I feel we're now in a position that we can expand the treatment options for children with achondroplasia. If there is a desire from the caregiver, the physician, the patients, we have a way we really can boost the effect on what we have seen on linear growth with TransCon CNP. We hope we can see the same improvement in the other elements beyond linear growth. The next step for us, as we said before, is to have the week 52 data, as Aimee said, will come end of the year. We plan to begin a phase 3 trial here in the end of this year to ensure we can get the fastest way at all to get this important treatment out to the patient.
We also see this year as a way to build our franchise as the leading company in the area of growth disorder, musculoskeletal health. We are in a unique position with our once-weekly Skytrofa, with our once-weekly TransCon CNP that both have two distinct synergistic effects. We will explore that to a lot of different indications, the more than 20 possible indications that are in this selection of indications. We believe that we can really develop the most adapted treatment to each of these single indications, either with Skytrofa alone or TransCon CNP alone or in combination for this patient group. Thank you a lot for this early morning call. I will now turn it over to Scott.
Thanks, operator. We're now ready to take questions.
Thank you. If you would like to ask a question, you will need to press star one and one on your telephone and wait for your name to be announced. To withdraw your question, please press star one and one again. We do kindly remind analysts to please ask one question and one follow-up and then rejoin the queue. Thank you. We will now go ahead with our first question. This is from Jessica Fye from JP Morgan. Please go ahead.
Hey, guys. Good morning. Congrats on the update, and thanks for taking our question. I guess two here. First, curious how you're thinking about the design of the phase 3 trial you're starting in the fourth quarter. Should we expect that to include both CNP naive and experienced children? Second, just to put a little more context around the combination group here, the children who had been on CNP before adding Skytrofa. It says that the baseline achondroplasia height Z-score was 1.28 here. Just to put that in context, can you remind us what TransCon CNP delivered on achondroplasia height Z-score in approach? Thank you.
Yeah. Jess, that was a lot of questions. I hope I got everyone down here. I think Aimee will likely help me here in all the different elements. Let me first, the first thing, when we look on the combination therapy and see how robust it is, because what we saw when we looked on each single subject, basically everyone benefited from it. Even if you came down with a low annualized height velocity and you came into the trial, everyone got a benefit from it. That really shows us the robustness in the treatment. When we think about opening up for the inclusion-exclusion criteria, we would basically take everyone in. That can be on prior growth hormone treatment before or past when we need a washout period. That could have been on other short-acting vosoritide product.
That could be on other things that really address the hypoactive tyrosine kinase. We would take them in because we know all of them need it. We will be open for that. We think a really single study, we still need the JTOIs here, but we still need to have our discussion with regulatory agencies. We believe it's a simple design with two arms, one with TransCon CNP, one with TransCon CNP plus Skytrofa, and compare them over 52 weeks. We see that as a very, very standard, simple design. It will be open basic for everyone. You went back and talked about, Jess, what I, as I recall it, we have two groups in this trial. We have one that was naive. They come in and started to put both on Skytrofa and TransCon CNP immediately.
If you go to the slide that Aimee somewhere took up where she looked on the demographic, and I can correlate you directly to the slide. That is slide number seven, where she came in and looked at the treatment. You can see when you look at the age one group, the treatment naive is much younger, 4.7, or the other one is 7.9. You can also see that the group have been on a mean treatment with TransCon CNP on 100 micrograms per kilo per week for about 2.6 years. During this year, you can see the effect of that, as Aimee explained, on the height score. That came from basically typical around zero or a little bit positive to it, and then moved up to 1.28. What we generally have seen on height score in monotherapy is around 0.3 on 52 weeks.
I think what Aimee did really excellent, which I really believe is really a beautiful slide, is the slide 12, where you basically can see the difference when we compare to ACH, the Z-score, achondroplasia there. You can basically see how we are having our patient group that was naive just in the middle on the achondroplasia 50 line. We also saw the treatment benefit of the two years where the basic, I am moving up to the high 95% fractal of achondroplasia. That is the benefit on height that you have received with monotherapy for the 2.6 years. Aimee, you can take some of the things I forgot.
Thank you. Hi, Jess. You had asked about our phase 3 trial if we plan to take in both treatment experienced and treatment naive. The answer there is yes, that is the plan. You also asked for context about the change in height Z-score, achondroplasia specific height Z-score in the approach trial, the pivotal approach trial. Jan got it exactly on the head there. Indeed, in approach, as you remember, that was a 52-week trial. The children on average improved their height Z-score by 0.3. They went up a third of a standard deviation over one year. Compare that to what we are seeing in half a year here. We are going up 0.4 and 0.5, regardless of if you are experienced or naive. You can see why we are enthusiastic about this acceleration, this boost in growth.
Yeah. I think it's going back to Aimee's comments and also what is on the next step. When we look at this from the perspective, just focus on linear growth. We are making treatment beyond linear growth. That is our attention, but just looking on linear growth, we look at the same time period, you basically get more than 3x the linear growth in the same time period.
Thank you. We'll now take the next question. This is from Gavin Clark-Gartner from Evercore ISI. Please go ahead.
Hey, guys. Congrats on the very strong data. First, and we'll see how the longer-term data evolves, but do you envision that this combo will be a long-term treatment for all patients until they get up to adult height? Or is there the potential that some patients may go on to the combo for a more fixed duration and then continue on TransCon CNP monotherapy after that? That's the first question. I just wanted to quickly confirm, do you have the ability to co-formulate CNP and growth hormone into a single chamber injection with novel IP and pricing? Thank you.
Let me take the last one, the small sample, because that is clear. Yes, we can co-formulate it. We can make it into one single injection. For that, we have not seen any kind of, you can say, feedback that was negative to these two injections in one week. I think two injections with this system in one week has not given us any kind of concern to anything that really should impact the implementation on such a treatment regime. Co-formulation, yes, I see it more as an LCM activity, and it will be part of our continual LCM discussion in this way.
The first question in some way, I believe, and the question that in some way we cannot come with a definitive answer because I believe there will be parents, there will be patients, there will be physicians that really will sit together and talk about what do we want to achieve in our treatment. I think that all of us want to say, "I want to have TransCon CNP because TransCon CNP is really providing the benefit beyond linear growth we have seen so many places for the parents and the patient and physician." We really have recognized that. You always see TransCon CNP will be the background. I think that the data we provided was the reason why we got a priority review for this product because it is really unique background. There will be parents, there will be patients, there will be physicians when they are discussed.
Do we want to accelerate some element like the linear growth for a period of time or perhaps for longer duration? I think there will be a decision for them some way to go in and discuss related to what is really their wanted treatment outcome, what is the thinking related to height, what is the thinking related to the social impact analytics. What we are providing, we are providing a treatment option. Then it's them to select if they want to take it.
Thank you. We'll move to the next question. This is from Paul Choi from Goldman Sachs. Please go ahead.
Good morning. This is Daniel Ang for Paul. Congrats on the strong efficacy effect. We have two questions. For the HGH, human growth hormone, for the move forward dose, are you thinking about fixed dose or are you still there's flexibility for adjustment there? How should we think about potential efficacy regressions at week 52? What would you think for the bar on this? Thank you.
What we have seen of data, and that was a really nice study, a Japanese study, where I think the number of patients was more than 40 and they were followed up to, was this about four or five years? Five years. What we saw in achondroplasia, we saw a boost in the first two to three years. Then we saw a continued curve that basically continued much higher up than the baseline. When we go to growth hormone deficiency children where they do not have any break on, we also see catch-up growth. Catch-up growth is the biological system you some way have that makes you come up to your genetic potential. When you are coming up to the place in the treatment where you can hit your genetic potential, you go over and more develop as a normal child.
What we saw here is that we really can unlock the catch-up growth. That is what we're doing. We are unlocking the catch-up growth, and this is why when you look on the normal development of a child in slide 11, we are on 97% fractal. This is because you're getting catch-up growth. I actually believe you will see some of the same biology. I do not know yet. The future will see it, but I believe you will likely see the same biology when the body believes, "Now I have done enough catch-up growth that I can go up to my genetic potential," then you start to develop as a normal child.
Thank you. We'll take the next question. This is from Derek Archila from Wells Fargo. Please go ahead.
Hey, good morning, and congrats on the data. Just two from us. I know it's a small data set, but just curious on how the efficacy compares across the age-matched patients in the naive and experienced groups in COACH. That's question number one. Question number two, I know it's very early, but beyond the body proportionality, are there any other improvements that you're seeing on some of the comorbidities in achondroplasia that you can share with us? Thanks.
Yeah. Let me just start with the first question, and Aimee can add in. Yes, everything what we have looked at, we have seen the same development, positive development that we wanted to see. Some of them, we wait for the 52 weeks because this is where we basically have the key primary endpoint, and that will be reported at that time. We also would like to see how the development going over one year. When we look and analyze high velocity, we actually see it pretty stable between three to six and other things like that. It's not like we see a huge difference between the different elements on that. Aimee, will you describe some of the classical things we also have done in the monotherapy, but we will basically look on some of the same things, Aimee?
Yeah. Just as Jan said, we're waiting to see some of these things at week 52, but these do include radiographic endpoints such as are the legs growing straighter, and then additional anthropometric measurements, which is measuring leg length, right, the appendicular skeleton, leg length, arm span, as they compare to the axial skeleton, that's the spine. Back to the radiographic endpoints, we will also continue to be looking at the spinal canal dimension. Thank you.
I think the question that you were asking too was when we look on the two age groups, do we see the same improvement in age group? I had to think why I like the slide that you saw in that now I'm referring back to the same slide again, but it's basically illustrated well. When you go to slide 11, you basically can see, yes, there is an impact on, sorry, slide 12. Scott really came with a good comment today. If you go to slide 12, you basically can see that when you look on children with achondroplasia, that is a natural development during the different ages. When I look on the different age group, the 8 and the 4.5 group, I actually think I see some of the same response in this way. I'm really feeling confident.
When we look on each single subject, there was not one single subject that did not have a boost, really, really a triple boost on them, really show that it is a robust response.
Thank you. We'll take our next question. This is from Yaron Werber from TD Cowen. Please go ahead.
Great. Thanks so much and congrats on really nice data for me as well. I have two questions. The first one is on body proportionality. Was the baseline one point? I'm just trying to put the 0.04 and 0.05 in context. It looks to be similar. I mean, this is 26 weeks. It looks to be similar to what CNP does alone, but that's at 52 weeks. Maybe you can kind of address that. Secondly, I was under the impression, perhaps incorrectly, perhaps I misunderstood, that you were able to add a control arm at some point later on in the study because you had so much interest in the study. Can you discuss that and whether we can see that data at some point? Thank you.
We don't have any control arm. We only have the 21 children, and that two arm is pretty, pretty clear. Just referring back to you, I think if I look on the TransCon CNP monotherapy arm and then look on 52 week, I get it to be, now I'm eyeballing, but it's something between 0.03-0.04. It's perhaps 0.38 that basically got improved compared to 52 weeks. This is a benchmark we had in that if I go back and look on slide, now Scott is helping me. This is slide 13. I see this is over 26 weeks, meaning half of the time, half of the time, you basically, when you look on the treatment naive, you have at least 0.04, and for TransCon CNP treated, you have at least 0.05.
Whatever I look at that, it's more double up, perhaps it's triple up the improvement in the element of body proportionality. I would call it an acceleration of the positive part of body proportionality. This is how I see on the data.
Thank you. We'll take the next question. This is from Joe Schwartz from Leerink Partners. Please go ahead.
Great. Thanks very much, and congratulations. I was wondering if you've done any payer work to test their receptivity to combination treatment, and then what kind of a label would you expect? Would this be an sNDA for Skytrofa, and can you get any unique claims on the TransCon CNP label, which you can use to encourage people to reach for TransCon CNP over legacy CNP? Also, just a clarification, can you provide any color on why patients are receiving 0.3 mg per kg per week of TransCon Growth Hormone versus the FDA label, which for growth hormone, which is like 0.24 mg per kg, I believe?
Yeah. Let me take the last one first, Joe, because when you look on an achondroplasia child, we basically we will call it they have a normal IGF-1 growth hormone axis. This is the same as you saw in a Turner child. It's the same as you've seen in some of the other growth hormone indication. When you go into, for example, ISS, HGA, or all of them, you basically use a higher concentration of growth hormone compared to growth hormone deficiency. When you look on our Turner trial, it actually also was done on 0.30 milligram per kilo per week. It's mainly just reflecting on that in achondroplasia, you all have a normal IGF-1 growth hormone axis. You can still look on the data, and if you look at the data, they actually have lower IGF-1 compared to a normal population.
The basic is you can say low in IGF-1, and it's potential also why we see this amazing effect in it. This is why you use 0.30 in it. Related to pair, we see as we in some way as a first part to the market, and for example, take U.S. We will have Scott over in the market. We will get hopefully as fast as possible TransCon CNP in the U.S. market. This is two independent brands. We will conduct this trial as fast as possible. We know we can get the patient immediately. Like in our pivotal trial, we recruited in three months, unbelievable. We will get the same interest for this trial. As soon as we get that on our labeling, we can go out and promote this combination.
The product will already be available as soon as the monotherapy will be in the market. Related to labeling is, yes, this is effect. You basically only will see with TransCon CNP, which will have its own brand name, and TransCon Growth Hormone. This is product specific. It is not something you can achieve in other things. It needs to be proven if it actually can be achieved with other combinations.
Thank you.
Thank you. We'll take the next question. This is from Li Watsek from Cantor. Please go ahead.
Hey, guys. Congratulations on the data. I wonder if you can maybe just talk about your expectations for the adult height from the combo treatment, and I noticed there's one severe adverse event in the study. Maybe if you can elaborate on that, that would be great?
Aimee, will you take the last one first?
Yeah, sure. Hi, Lee. That was a respiratory tract infection, a viral etiology that required an overnight observation in the hospital and deemed to be unrelated to study drug.
The element of what you ask is some way the idea what we're doing with our combination. We unlock the potential for achondroplasia patient to get catch-up growth. When I look on children, for example, in pediatric growth hormone deficiency, when we unlock the children's potential to get catch-up growth, and we know they're keeping much better off the treatment, we saw basically 50% of them hitting their average, or say it a different way, their average height was exactly matching and a little bit higher than the expected parental height from their parents. Meaning is that you basically can normalize height. You can never do that if you then don't unlock catch-up growth. That is impossible.
It is such a unique advancement in the treatment of achondroplasia, because if the parents or children decide to do it, now there is a treatment option that really unlocks to get catch-up growth. I think that is up to the parents, the patients, to decide what they really want to get out of it. It is not changing my view that you always need TransCon CNP as a backbone to really provide the benefit not only on linear growth, but also on the treatment benefit beyond linear growth.
Thank you. We'll take the next question. This is from Ellie Merle from UBS. Please go ahead.
Hey, guys. Thanks for taking the question. I'm curious your development strategy and indications beyond achondroplasia. There's a lot of data emerging from indications where growth hormone is approved, such as ISS, new mentions of CNP having efficacy from BioMarin. So I'm curious your strategy for development there. Thanks.
Yeah. You're 100% right that there is a unique treatment opportunity for SNDs now, with where we have TransCon Growth Hormone, TransCon CNP, and now we are seeing how we really can, I would not say prove science because we don't prove science. We just unlock science. We really have seen the potential of the combination therapy to unlock new treatment options that never existed before. When I look on the different indications, yes, hypochondroplasia, yes, this is somewhat what Aimee is trying to plan it in. I think we are planning for more than five, six, seven different indications here for the next 18 months to be initiated in late-stage development. And this is our dedication to take each of our single unique opportunities and develop a basic portfolio of indications that will be supported with them.
You will hear much, much more about that, the label expansion strategy we have for our different product opportunities, not only Skytrofa, not only TransCon CNP, but also our TransCon PTH, where we also initiate a lot of label expansion.
Got it. Thanks.
Thank you. The next question is from David Lebowitz from Citi. Please go ahead.
Hello. Thank you for taking my question. When looking towards the pivotal, what do you expect to have to show the agency? Is catch-up growth enough? Do you need to have follow-up long enough to determine that it's catch-up growth plus additional kind of increasing the peak prospective height for a patient? What ultimately do you think they need to see to buy into the combination?
I think to buy in a combination, I think the clearly obvious one is safety. What we saw here in both with the TransCon Growth Hormone was we have seen with TransCon CNP and the combination, we do not see any kind of unexpected safety reaction compared to what we have seen on the monotherapy from both of them. We feel really, really confident with the safety we have seen. We will need to show that in sites that basically the regulatory agencies will someway calculate, and we will justify it for what should be our sample size related to safety. Related to efficacy, it is pretty clear. We will have two independent trials that both have 12 months' data, and we will be part of the filing. This will be typical the way we have seen our filing.
If I go to TransCon CNP, they have never asked anything else than 12 months' data. This is what we have. We have long-term open label extension data. When I look on the efficacy part, it's 12 months where you have a placebo control. There has never been a discussion about anything else. It was the same thing with Skytrofa. There was no discussion about anything else. I think we will see the same, and I expect the same thing also be taken up from the regulatory agencies that you will see the same routine, the same standard that they have used on all our other products will also be the same for the combination therapy.
Thank you for taking my question.
Thank you. Next question is from Kelly Shi from Jefferies. Please go ahead.
Congrats on the strong data. Maybe from a biology perspective, how does Skytrofa, our growth hormone, work synergetically to TransCon CNP so the combo can actually boost the growth three times above the CNP monotherapy, given that historically growth hormone therapy seems to have very limited effectiveness on growth velocity in achondroplasia patients? Thank you.
Yeah. I actually think that was why we developed this really nice slide that Scott will find out now what slide number it is. It's slide number four. And it's really what we call the expanding the treatment paradigm. Because you are right, growth hormone, even we have 40, I talked about the 40, 50 children that have been treated for five years where we give some effect. The problem is it's pretty logical. It will have limited effect because if you have a break on all the stimulatory effect of growth hormone, growth hormone makes a stimulation of many places inside the growth plate by different levels. If you have a break, that basic break, all the stimulatory effect on it, then you don't see the key element of that.
This is why when you take growth hormone and give it to growth hormone deficient children, but do not have a break. This is why you get the catch-up growth. What we basically are doing with TransCon CNP as a base or background treatment is that you unlock this break. You remove the break. You more have children looking more like growth hormone deficients. Then you can get the catch-up growth. I think this is pretty elegant biology, but it is really simple. It is following everything we know from biology. It is not like we are coming with I do not think Scott will get a Nobel Prize for this year.
Basically, we will get a lot of elements that are in a situation that we are proving that what really are following the biology, following the science, it really always gives the expected results. When we sometimes do not get the right results, it is because we did not understand the biology well enough. This year is really, really well understood how when you have a hyperactive tyrosine kinase, you basically have a break in the system, and you cannot boost something that really has a break. This is where the car came in and everything like that. If you have the hand brake on it, you can really turn on the speed a lot, but it is not really moving the car a lot. Scott telling me that.
What do you take the hand brake off, you basically can get it really to move forward. Think about in catch-up growth, think about the catch-up growth you see with growth hormone deficiencies because they do not have a brake. We are basically unlocking the brake that is, and therefore you see this high, high growth.
Thank you.
Thank you. The last question today is from Luca Issi from RBC. Please go ahead.
Oh, great. Thanks so much. Thank you for squeezing me in and congrats on the data. Maybe just circling back on a prior question, just to be clear, will the co-formulation be available and ready to go for the phase three that you're starting in Q4, or is this more of a lifecycle management at some point down the line? And then maybe Aimee, could you just talk about the powering for the phase three? How many patients do you think you'll need in order to hit the stack given the signal here? I think the approach trial was 84 patients. Should we assume a trial of similar size? Any thoughts there? Much appreciated.
As you said, Aimee will answer the last one. I will take the first one. This is clearly an LCM activity. For example, if you see in the U.S., we have basically already TransCon Growth Hormone in the market as Skytrofa. We will have TransCon CNP in the market on a different brand name, but it will also be in the market before there will be a fixed dose combination. Aimee?
Sure. Hi, Luca. And your question to me was about sample size calculation. We will start having some ideas now at week 26. Ultimately, we will wait till week 52 because that would also be the main endpoint for the confirmatory pivotal trial. We will take a look at the treatment effect and then the standard deviation. That is how much variability we have around the effect. Using that with the expectation of what mix we have of aged kids and things like that, we will make a sample size determination. Right now, could not say more than that until we see the data.
Basically what Aimee is saying is that when we do the final element of the sample size, we will initiate the trial now. We will have a calculated sample size where we've used the parameter we have seen on the 26-week to estimate it. When we basically are getting the 52 weeks, we can confirm that sample size. It's a typical why we're starting the trial as fast as possible so we basically can get this out to the patients as fast as possible.
Great. Thanks so much.
Thank you. That is all the time we have for questions today. This does conclude the conference call for today. Thank you for participating and to your.