The U.S. Food and Drug Administration (FDA) has extended its review period for Ascendis Pharma’s TransCon CNP, a treatment for achondroplasia, by three months. The decision follows Ascendis’ submission of additional information regarding post-marketing requirements earlier in November. The FDA classified this as a “major amendment,” prompting the extension. Ascendis now expects a final decision on or before February 28, 2026, rather than the original November 30, 2025 target.
Ascendis CEO Jan Mikkelsen commented on the delay, stating that the company has addressed “all outstanding requests from the FDA.” He added that Ascendis will continue to work with regulators to make TransCon CNP available to patients who need it “as soon as possible.”
Achondroplasia is a rare genetic disorder affecting bone development and is recognized as the most common cause of dwarfism worldwide. It affects between 15,000 and 40,000 newborns globally. TransCon CNP—also known as navepegritide—is designed to treat achondroplasia caused by an overactive FGFR3 gene, which can also lead to neurological and cardiorespiratory complications.
The therapy works by delivering C-type natriuretic peptide (CNP) to counteract mutated FGFR3 activity and promote bone growth. Results from the Phase II ACcomplisH study published in The Lancet in November 2023 indicated improved growth rates among patients treated with TransCon CNP.
This regulatory delay offers BioMarin more time without competition for its drug Voxzogo—the only FDA-approved treatment for achondroplasia since November 2021—which also targets FGFR3 signaling through mimicking CNP action. During BioMarin’s third-quarter earnings call in October, CFO Brian Mueller noted concerns about future competition from products like TransCon CNP and other investigational therapies such as BridgeBio’s infigratinib. As a result, BioMarin abandoned its previous goal of reaching $4 billion in revenue by 2027 due to anticipated impacts from new entrants into the market.
