The U.S. Food and Drug Administration (FDA) has extended its review of Ascendis Pharma A/S’s therapy for children with a rare genetic disorder that causes dwarfism, the company said on Nov. 25. The FDA moved the review deadline to Feb. 28, 2026.
Extension follows submission of additional information
The health regulator extended the review after Ascendis submitted supplemental data on Nov. 5 related to a required follow-up study. The submission prompted a significant change to the company’s application, the company said.
Ascendis CEO Jan Mikkelsen said the company had addressed all outstanding questions from the FDA, including a revised plan for the post-approval study. The company will continue collaborating with the agency to finalize study requirements.
TransCon CNP targets achondroplasia growth issues
The therapy, called TransCon CNP, is designed to treat children with achondroplasia, a rare disorder caused by a mutation in the fibroblast growth factor receptor 3 (FGFR3) gene. The mutation disrupts normal bone growth, resulting in dwarfism.
TransCon CNP uses a naturally occurring peptide, C-type natriuretic peptide (CNP), which research shows can counteract the growth-inhibiting effects of the FGFR3 mutation and stimulate growth in affected children.
Company progress and clinical context
Ascendis has previously reported positive results from clinical trials of TransCon CNP, showing increased growth velocity in children with achondroplasia. The therapy is delivered via weekly injections and is currently being studied in multiple international trials to evaluate long-term efficacy and safety.
Achondroplasia is the most common form of dwarfism, affecting about one in 25,000 births worldwide. Children with the disorder often face complications including disproportionate limb growth, spinal stenosis, and delayed motor development. Current treatment options are limited, and no therapy specifically targeting the FGFR3 pathway has received full FDA approval.
The FDA typically reviews new drug applications within a set timeline but can extend the review period if additional information is required or if major changes to the application are submitted. In this case, the agency’s three-month extension reflects the need to evaluate the new data and revised study plans.
Ascendis, based in Denmark, specializes in developing therapies for rare endocrine and growth disorders. The company has several investigational therapies in its pipeline, including treatments for adult growth hormone deficiency and other rare pediatric conditions.
Mikkelsen said the company remains committed to providing therapies for children with rare growth disorders and will continue working with regulatory authorities to ensure TransCon CNP meets safety and efficacy standards.
Also read: FDA Approves Novartis Gene Therapy for Rare Muscle Disorder
