A once-weekly combination of navepegritide and lonapegsomatropin maintained annualized growth velocity of approximately 7.7 centimeters per year through 78 weeks in children with achondroplasia, according to updated Phase 2 COACH trial findings from Ascendis Pharma. All 21 enrolled children completed the assessment period and remained on treatment, with the company reporting continued improvements in height measurements and body proportionality without new safety or tolerability signals.
The results extend encouraging findings previously reported at 26 and 52 weeks, but the study remains an open-label trial involving only 21 participants and no concurrent monotherapy or placebo group. The data therefore support the durability of the observed growth response without establishing that the combination is definitively superior to navepegritide alone.
Growth velocity remained near 7.7 centimeters per year in both COACH cohorts
COACH is evaluating once-weekly navepegritide at 100 micrograms per kilogram together with once-weekly lonapegsomatropin, which began at 0.30 milligrams per kilogram. The trial enrolled 12 children who had not previously received navepegritide and nine who had already been treated with the C-type natriuretic peptide therapy for an average of 2.56 years. Participants were between two and 11 years old when they entered the study.
Children in the treatment-naïve cohort recorded a mean annualized growth velocity of 7.73 centimeters per year at week 78. Their mean achondroplasia-specific height Z-score increased from 0.46 at baseline to 1.75, representing an improvement of 1.29 points.
The previously treated cohort achieved a mean annualized growth velocity of 7.67 centimeters per year. Mean achondroplasia-specific height Z-score increased from 1.28 to 2.38, an improvement of 1.10 points despite participants having already received navepegritide for more than two years on average before beginning combination therapy.
Ascendis Pharma said growth velocity in both groups remained at or above the 97th percentile for children of average stature and characterized the height Z-score gains as approximately three times the efficacy associated with navepegritide monotherapy. That interpretation is promising but should be treated cautiously because COACH was not designed as a randomized combination-versus-monotherapy trial. Comparisons with earlier trials or previous treatment periods can be affected by age, baseline growth patterns and differences between study populations.
Annualized growth velocity also does not directly reveal how much additional adult height the combination will ultimately produce. Growth rates change naturally as children age, and longer follow-up will be needed to determine whether the early acceleration is maintained, gradually declines or alters final height.
Body proportionality findings may matter as much as additional height
Ascendis Pharma reported that improvements in body proportionality continued through week 78 and generally tracked with increases in linear growth. Detailed measurements have not yet been released, with additional COACH results expected at a future medical meeting.
This aspect of the study is clinically important because achondroplasia affects skeletal proportions, limb alignment and several anatomical systems rather than height alone. A treatment that accelerates growth without preserving or improving proportionality could have limited value, while changes in lower-limb alignment or segment ratios may eventually influence mobility, pain and the need for orthopedic intervention.
The available data do not yet show whether the anatomical changes translate into better physical function or fewer long-term complications. Those questions will require longer follow-up using functional, surgical and quality-of-life outcomes rather than growth measurements alone.
Navepegritide monotherapy has already produced evidence of effects beyond linear growth. Ascendis Pharma’s 104-week ApproaCH update showed sustained annualized growth and height Z-score gains, together with improvements in tibial-femoral angle and upper-to-lower body segment ratio. Children who crossed from placebo to active therapy after 52 weeks also demonstrated catch-up growth during the extension period.
The United States Food and Drug Administration approved navepegritide under the brand name YUVIWEL in February 2026 for children aged two years and older with achondroplasia and open growth plates. The once-weekly medicine received accelerated approval based on annualized growth velocity, meaning continued authorization may depend on confirmatory evidence establishing longer-term clinical benefit.
The regulator requires Ascendis Pharma to conduct a postmarketing study examining final adult height and disproportionality while monitoring neurological complications, bone deformities, bone age, sleep apnea and other long-term outcomes. The planned completion date for that obligation extends into 2035, illustrating how long it may take to determine the full effect of growth-promoting treatment in achondroplasia.
Full safety data are needed before the combination’s trade-offs are clear
Ascendis Pharma described the dual treatment as generally well tolerated, with a low incidence of injection-site reactions and mostly mild treatment-emergent adverse events. Safety was said to be consistent with the established profiles of the two individual therapies, and no child discontinued during the first 78 weeks.
Complete adverse-event tables were not included in the topline announcement, limiting assessment of event frequency, laboratory changes and dose modifications. The 100% retention rate is reassuring, but rare or delayed adverse effects cannot be excluded in a study involving 21 children.
Navepegritide is a C-type natriuretic peptide analog designed to counteract excessive fibroblast growth factor receptor 3 signaling, the central biological driver of impaired bone growth in achondroplasia. Its approved prescribing information lists vomiting, injection-site reactions, pain in the extremities and nausea among the most common adverse reactions and includes a warning regarding possible transient decreases in blood pressure.
Lonapegsomatropin is a long-acting growth hormone therapy approved for pediatric growth hormone deficiency but remains investigational as an achondroplasia treatment. Combining two growth-promoting mechanisms may produce greater efficacy, although investigators must monitor whether increased growth affects bone maturation, spinal curvature, limb alignment, metabolic measures or other disease-related complications.
The two-injection weekly regimen may also create a greater treatment burden than navepegritide monotherapy. Families and physicians will ultimately need evidence that the additional growth and proportionality benefits are substantial enough to justify adding another medicine.
YUVIWEL uptake and broader trials expand the achondroplasia strategy
Ascendis Pharma reported more than 170 unique U.S. YUVIWEL patient enrollments through June 30, involving approximately 90 prescribing clinicians. More than 65% of enrolled patients had received reimbursement approval, indicating early commercial access several months after the product’s U.S. launch.
The company is also expanding development into additional age groups. Target enrollment has been completed in the pivotal reACHin trial involving children younger than two years, while the teACH study is evaluating adolescents aged 12 to under 18. The AttaCH extension study continues to provide long-term monotherapy follow-up, with 96% of 140 enrolled children remaining on navepegritide or transitioning into COACH. A European regulatory decision on navepegritide is expected during the fourth quarter of 2026.
Ascendis Pharma shares traded near $249.85 during the August 6 session, rising approximately 2.4% and giving the company a market capitalization of about $29.1 billion. The positive but measured reaction suggests investors viewed the durability data and U.S. uptake as supportive without treating the small open-label combination trial as a decisive valuation event. That explanation is an inference from the trading pattern rather than a confirmed account from market participants.
The COACH findings strengthen the rationale for continued combination development. Sustained growth of approximately 7.7 centimeters per year, improvement in height Z-scores and complete participant retention create a credible signal that adding lonapegsomatropin may increase the effect of weekly navepegritide.
The next evidence must show whether the benefit remains durable, improves function and proportionality, and meaningfully exceeds monotherapy without adding unacceptable safety or treatment burden. Until a controlled comparison or larger confirmatory dataset becomes available, the combination should be considered a promising investigational strategy rather than an established new standard.
