The FDA has delayed a decision on Ascendis Pharma’s dwarfism drug candidate TransCon CNP, pushing back the deadline by three months to buy time to review recently submitted information.
Having accepted TransCon CNP for priority review, the FDA originally planned to make an approval ruling by Nov. 30. However, with days to go until the deadline, Ascendis revealed the FDA has delayed its decision. The delay will give the FDA time to review information the company filed Nov. 5 regarding its post-marketing requirement (PMR). The new decision deadline is Feb. 28, 2026.
Ascendis CEO Jan Mikkelsen said in a statement that the FDA’s request for a revised protocol for the post-marketing study was “the lone item for discussion at our late-cycle meeting.” TD Cowen analysts flagged the “lone item” comment as a positive in a note to investors about the prospects of approval in the dwarfism condition achondroplasia.
The analysts said the delay is unexpected, but they continue to expect approval given the FDA’s lone request was a protocol revision for the PMR. The requirement for a post-market study is a condition of the accelerated approval pathway. Based on the absence of a request for clinical data, the analysts said the FDA “is likely comfortable with the efficacy and safety” seen in Ascendis’ phase 3 trial.
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Ascendis’ executives were surprised the Nov. 5 submission was deemed a major amendment, according to the analysts. The analysts surmised that the FDA likely has not had enough time to review the protocol and revert with comments. As the analysts noted, the delay “is somewhat consistent with a recent trend of delays considering staffing cuts at the FDA.”
Days before the delay, the analysts said their base case is that the FDA approves TransCon CNP for use in children aged 2 to 11 years old. In the post-delay note, the analysts said they are encouraged that Ascendis’ management seems happy with the likely future label. The analysts speculated the upbeat outlook of the executives means the FDA could grant approval in a broader age group.
Ascendis’ phase 3 trial enrolled children aged 2 to 11 years. The analysts cited the precedent set by the FDA’s approval of BioMarin’s Voxzogo—which received a broad age label despite not showing statistical significance in people aged 11 to 15 years old—to make the case that the agency might allow TransCon CNP use in older children.
“This is an important age group as the bone plates typically do not fuse until mid-teenage years,” the analysts said. “Hence, we wonder if the PMR will include collecting registry data across various age groups while the label allows for use in a broader age group ≥2 y/o.”
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If approved, TransCon CNP will compete with Voxzogo. TransCon CNP is a once-weekly prodrug of C-type natriuretic peptide (CNP), a molecule that accelerates children’s growth. Voxzogo is a CNP analog that is injected once a day. The analysts said the phase 3 data on TransCon CNP and Voxzogo look similar, but Ascendis’ weekly dosing and absence of hypertension could give it an advantage.
BioMarin is racing to defend its territory. The biotech shared phase 1 data on a once-weekly successor to Voxzogo in August. BioMarin R&D chief Greg Friberg, M.D., said at the time that the drug candidate achieved area-under-the-curve levels greater than three times those reported for another long-acting CNP.