AstraZeneca gets FDA priority review for rare bone drug

On 18 September 2026, AstraZeneca announced that the US Food and Drug Administration accepted its filing seeking approval for efzimfotase alfa. The investigational enzyme replacement therapy is designed to treat patients aged two years and older with hypophosphatasia, a rare inherited bone and tooth disorder caused by low alkaline phosphatase activity. The agency granted the application priority review, cutting the review window by four months and setting an expected decision date in the first half of 2027.

The submission rests on three phase III trials. The MULBERRY study met its primary endpoint by showing significant bone health gains in previously untreated children aged two to less than 12 years. The CHESTNUT trial showed that patients switching from AstraZeneca's existing drug, Strensiq, maintained their clinical benefits. Although the HICKORY study missed its primary endpoint in treatment-naive patients aged 12 and older, the company noted numerical improvements, particularly in pediatric-onset cases. Across all three studies, the therapy showed an acceptable safety profile.

Efzimfotase alfa offers lower injection volumes and dosing once every two weeks, compared with Strensiq's three-to-six weekly regimen. Strensiq, which joined the drugmaker via its 2021 Alexion acquisition, generated $1.05 billion in sales during the first half of 2026, marking a 41% year-over-year increase. Competitors are also advancing oral alternatives: BioMarin Pharmaceutical acquired Alesta Therapeutics earlier this month for $275 million upfront and up to $215 million in milestones to gain ALE1, while Recursion Pharmaceuticals is evaluating REC-102 in pre-clinical studies.

Shares of AstraZeneca are down 10% year to date, lagging behind the broader industry's 6% gain.