Ascendis Pharma reports 52-week infant data for TransCon CNP at ESPE

Ascendis Pharma has presented the first data from infants enrolled in its reACHin trial of TransCon CNP (navepegritide), reporting that the once-weekly prodrug stabilised or improved a critical neurological risk marker and increased linear growth over 52 weeks in children aged under two years with achondroplasia.

The data, presented by Geneviève Baujat, clinical geneticist at Necker-Enfants Malades Hospital in Paris, were delivered at ESPE 2026, the annual meeting of the European Society for Paediatric Endocrinology. The cohort comprised seven infants with a mean age of 11.7 months at enrolment, forming an open-label sentinel group ahead of the now fully enrolled double-blind portion of the trial.

What the data show

The primary focus of the sentinel readout was the Achondroplasia Foramen Magnum Score, an MRI-based grading system that classifies severity of foramen magnum stenosis, a narrowing of the skull opening through which the brain stem passes. In all seven children, the score was stable or improved from baseline to Week 52. The mean change in sagittal foramen magnum diameter was +3.15 mm, and no decompression surgeries were required during the observation period.

On growth, the mean change from baseline in the achondroplasia-specific supine length Z-score was +0.42, with a mean annualised growth velocity of 9.9 cm/year. The pharmacokinetic profile in infants was consistent with that observed in older paediatric patients, which the company said supports use of the 100 µg/kg/week dose across the age range.

The tolerability picture was clean: no injection site reactions, no deaths, fractures, or bone-related safety events, no symptomatic hypotension, and no treatment discontinuations attributed to adverse events over the 52-week period.

Baujat said the findings demonstrated how early intervention "could help address medical complications and growth limitations in infants with achondroplasia," singling out the foramen magnum data as particularly meaningful in a vulnerable population.

Regulatory and competitive context

TransCon CNP received FDA approval in February 2026 under the trade name YUVIWEL for patients aged two years and older with achondroplasia and open epiphyses. Ascendis has submitted a Marketing Authorisation Application to the European Medicines Agency, with a decision anticipated in the fourth quarter of 2026. Infant data are being collected separately because the approved label begins at age two; a positive reACHin outcome could support a future label extension into the youngest patients.

The infant achondroplasia space is scientifically significant because foramen magnum stenosis poses the most acute risk in the first two years of life. BioMarin's vosoritide, approved in several markets for children aged two and above, does not yet carry an infant indication, leaving early-life management of skeletal and neurological complications largely in the realm of watchful waiting and surgical intervention. The reACHin sentinel results, though drawn from a small cohort of seven children, are the first prospective drug-treatment data to address this gap using a CNP-based mechanism.

Investors will be watching the double-blind, placebo-controlled portion of reACHin, now fully enrolled, for the controlled efficacy and safety data needed to support a regulatory filing for the under-two population. The EMA decision on the adult-and-older-children YUVIWEL application due later this year will also shape the commercial and reimbursement landscape into which any infant label extension would eventually land.