At Week 104 of the pivotal ApproaCH trial in children with achondroplasia, once-weekly TransCon CNP (navepegritide) maintained gains in linear growth and showed continued improvement in body proportionality: the observed mean change from baseline in upper-to-lower body segment ratio deepened from -0.04 at Week 52 to -0.10 at Week 104. Children who crossed over from placebo at Week 52 reached a similar -0.10 by Week 104. Height Z-score improvements from Weeks 52 to 104 were consistent with the first year’s effect, and safety remained favorable with no symptomatic hypotension reported and mild injection-site reactions at 0.35 events per person-year. Trial retention was 95% (80/84 completing), with all completers rolling into the long-term AttaCH extension.
The core event is the first 2-year readout from the pivotal program following U.S. FDA approval of TransCon CNP (YUVIWEL) in February 2026 for pediatric patients aged two and older with open epiphyses. The new data, presented at ACMG 2026, reinforce durability of growth and proportionality benefits on the approved 100 µg/kg once-weekly regimen and provide additional safety depth in a class where hypotension monitoring has been central. In Europe, a Marketing Authorization Application is under EMA review with a decision expected in the fourth quarter of 2026; the Week 104 package now becomes a key component of that assessment.
Strategically, Ascendis is positioning weekly CNP exposure as an adherence- and operations-friendly alternative in a market defined to date by a daily injectable CNP analog. The proportionality gains are notable; while centimeters per year remain the regulatory anchor, proportionality is increasingly viewed as clinically meaningful for function and long-term morbidity. The placebo-to-active catch-up effect in Year 2 suggests a consistent pharmacodynamic response independent of start time, supporting flexible initiation in real-world practice. The absence of symptomatic hypotension across two years addresses a historical class concern and could lower monitoring intensity, an operational plus for sites and families.
For sites and CROs, the signal is that weekly subcutaneous administration with routine vitals and adverse event surveillance is feasible with high retention, implying manageable visit schedules and caregiver burden. Sponsors in skeletal dysplasias should note the trial’s use of both achondroplasia-specific and CDC height Z-scores and a proportionality endpoint that may resonate with regulators and HTA bodies seeking functional relevance beyond growth velocity. For payers and European assessors, two-year proportionality and safety continuity strengthen the case for reimbursement, but comparative effectiveness versus daily CNP therapy remains an open question that will likely be addressed through indirect comparisons or real-world evidence rather than head-to-head trials.
Near term, watch for EMA’s Q4 decision, U.S. uptake patterns as specialty pharmacies and pediatric endocrine networks operationalize weekly dosing, and early data from the AttaCH extension on durability past two years. Key risks and unknowns include the trajectory of outcomes beyond anthropometry—sleep-disordered breathing, spinal stenosis, and surgical interventions—and whether proportionality gains translate into measurable quality-of-life and functional advantages recognized by payers. Ascendis will also need to demonstrate reliable supply and streamlined at-home administration support to capture the adherence dividend it is targeting. If real-world data validate the proportionality and safety advantages at scale, competitive pressure could shift toward dosing convenience and long-term functional outcomes rather than incremental gains in growth velocity alone.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
