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FDA Grants Priority Review to AZN's Filing for Rare Bone Disease Drug
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Key Takeaways
AstraZeneca secured FDA priority review for efzimfotase alfa in HPP patients aged two and older.
MULBERRY improved bone health, while CHESTNUT maintained benefits after patients switched from Strensiq.
Efzimfotase alfa requires dosing every two weeks, versus Strensiq's three- or six-times-weekly regimen.
AstraZeneca (AZN - Free Report) announced that the FDA accepted its regulatory filing seeking approval for its investigational enzyme replacement therapy (ERT) efzimfotase alfa to treat patients aged two years and older with hypophosphatasia (HPP).
The FDA has granted the filing priority review, shortening the review period by four months. A final decision is expected during the first half of 2027.
HPP is a rare inherited metabolic disease caused by low activity of the alkaline phosphatase (ALP) enzyme, which is essential for healthy bone and tooth development. The condition can lead to poorly mineralized bones, skeletal abnormalities, muscle weakness, fatigue and pain, with symptoms ranging from mild to severe and appearing at any age.
The filing is supported by data from three phase III studies — MULBERRY, CHESTNUT and HICKORY. While MULBERRY met its primary endpoint in treatment-naïve children (aged two to less than 12 years old), demonstrating a significant improvement in bone health, CHESTNUT showed that patients switching from Strensiq could maintain the benefits of treatment.
HICKORY, however, did not meet its primary endpoint in treatment-naïve individuals aged 12 years and older. Still, AstraZeneca reported a numerical improvement among patients following treatment, particularly those with pediatric-onset disease (those whose HPP began in childhood). Overall, treatment with efzimfotase alfa across the three studies was generally well-tolerated and had an acceptable safety profile.
AZN Stock Performance
Year to date, shares of AstraZeneca have lost 10% against the industry’s 6% growth.
Image Source: Zacks Investment Research
Potential Approval Could Expand AZN’s HPP Opportunity
The commercial angle is particularly interesting because Strensiq is an established HPP treatment marketed by AstraZeneca. Approved by the FDA in 2015 as the first bone-targeted enzyme replacement therapy for HPP, Strensiq became part of AstraZeneca’s portfolio through the company’s acquisition of Alexion in 2021.
The commercial opportunity in HPP is already substantial. Strensiq generated $1.05 billion in sales in the first half of 2026, up 41% year over year, driven by continued demand from patients.
Efzimfotase could potentially build on this established market while addressing some of the treatment burden associated with Strensiq. The investigational therapy is designed to require lower injection volumes and substantially less frequent dosing — once every two weeks, compared with Strensiq’s three- or six-times-weekly regimen.
Other Companies Are Also Targeting HPP
BioMarin Pharmaceutical (BMRN - Free Report) entered the HPP space through its acquisition of Alesta Therapeutics, which was completed earlier this month. The deal added ALE1, an oral small-molecule therapy for HPP that is currently being evaluated in a phase I/IIa study in healthy volunteers and adults with HPP. BioMarin paid $275 million upfront for Alesta, with additional milestone payments of up to $215 million tied to the program.
Recursion Pharmaceuticals (RXRX - Free Report) is also developing an oral approach for HPP through REC-102, an ENPP1 inhibitor formerly known as REV102. Recursion acquired full rights to the program from Rallybio last year, and the candidate remains in IND-enabling studies. A data-driven decision on whether to initiate a phase I study of the candidate is expected before this year’s end.
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FDA Grants Priority Review to AZN's Filing for Rare Bone Disease Drug
Key Takeaways
AstraZeneca (AZN - Free Report) announced that the FDA accepted its regulatory filing seeking approval for its investigational enzyme replacement therapy (ERT) efzimfotase alfa to treat patients aged two years and older with hypophosphatasia (HPP).
The FDA has granted the filing priority review, shortening the review period by four months. A final decision is expected during the first half of 2027.
HPP is a rare inherited metabolic disease caused by low activity of the alkaline phosphatase (ALP) enzyme, which is essential for healthy bone and tooth development. The condition can lead to poorly mineralized bones, skeletal abnormalities, muscle weakness, fatigue and pain, with symptoms ranging from mild to severe and appearing at any age.
The filing is supported by data from three phase III studies — MULBERRY, CHESTNUT and HICKORY. While MULBERRY met its primary endpoint in treatment-naïve children (aged two to less than 12 years old), demonstrating a significant improvement in bone health, CHESTNUT showed that patients switching from Strensiq could maintain the benefits of treatment.
HICKORY, however, did not meet its primary endpoint in treatment-naïve individuals aged 12 years and older. Still, AstraZeneca reported a numerical improvement among patients following treatment, particularly those with pediatric-onset disease (those whose HPP began in childhood). Overall, treatment with efzimfotase alfa across the three studies was generally well-tolerated and had an acceptable safety profile.
AZN Stock Performance
Year to date, shares of AstraZeneca have lost 10% against the industry’s 6% growth.
Image Source: Zacks Investment Research
Potential Approval Could Expand AZN’s HPP Opportunity
The commercial angle is particularly interesting because Strensiq is an established HPP treatment marketed by AstraZeneca. Approved by the FDA in 2015 as the first bone-targeted enzyme replacement therapy for HPP, Strensiq became part of AstraZeneca’s portfolio through the company’s acquisition of Alexion in 2021.
The commercial opportunity in HPP is already substantial. Strensiq generated $1.05 billion in sales in the first half of 2026, up 41% year over year, driven by continued demand from patients.
Efzimfotase could potentially build on this established market while addressing some of the treatment burden associated with Strensiq. The investigational therapy is designed to require lower injection volumes and substantially less frequent dosing — once every two weeks, compared with Strensiq’s three- or six-times-weekly regimen.
Other Companies Are Also Targeting HPP
BioMarin Pharmaceutical (BMRN - Free Report) entered the HPP space through its acquisition of Alesta Therapeutics, which was completed earlier this month. The deal added ALE1, an oral small-molecule therapy for HPP that is currently being evaluated in a phase I/IIa study in healthy volunteers and adults with HPP. BioMarin paid $275 million upfront for Alesta, with additional milestone payments of up to $215 million tied to the program.
Recursion Pharmaceuticals (RXRX - Free Report) is also developing an oral approach for HPP through REC-102, an ENPP1 inhibitor formerly known as REV102. Recursion acquired full rights to the program from Rallybio last year, and the candidate remains in IND-enabling studies. A data-driven decision on whether to initiate a phase I study of the candidate is expected before this year’s end.
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AZN’s Zacks Rank
AstraZeneca currently has a Zacks Rank #5 (Strong Sell). You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.