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Editorial
. 2025 Apr 21;40(4):463-477.
doi: 10.1093/jbmr/zjaf005.

Preclinical evaluation of the efficacy and safety of adeno-associated virus 8-tissue-nonspecific alkaline phosphatase-D10 in Alpl-/- and AlplPrx1/Prx1 mouse models for the treatment of early and late-onset hypophosphatasia

Flavia Amadeu de Oliveira  1 , Cintia Kazuko Tokuhara  1 , Fatma F Mohamed  2 , Sonoko Narisawa  1 , Elis J Lira Dos Santos  2 , Natalie L Andras  2 , Mohammad Shadid  3 , Koichi Miyake  4 , Brian L Foster  2 , José Luis Millán  1
Affiliations
Editorial

Preclinical evaluation of the efficacy and safety of adeno-associated virus 8-tissue-nonspecific alkaline phosphatase-D10 in Alpl-/- and AlplPrx1/Prx1 mouse models for the treatment of early and late-onset hypophosphatasia

Flavia Amadeu de Oliveira et al. J Bone Miner Res. .

Abstract

We previously documented successful resolution of skeletal and dental disease in the infantile and late-onset murine models of hypophosphatasia (HPP) with a single injection of an adeno-associated serotype 8 vector encoding mineral-targeted TNAP (AAV8-TNAP-D10). Here, we conducted dosing studies in both HPP mouse models. A single escalating dose from 4 × 108 up to 4 × 1010 (vg/b) was intramuscularly injected into 4-day-old Alpl-/- mice (an infantile HPP model) and a single dose from 4 × 106 up to 4 × 109 (vg/b) was administered to 8-wk-old AlplPrx1/Prx1 mice (a late-onset HPP model). Wild-type littermates were used as controls. Serum alkaline phosphatase activity was increased, and PPi levels were decreased in a dose-dependent manner in both the Alpl-/- and AlplPrx1/Prx1 models. Radiographic and μCT analysis of long bones of female and male Alpl-/- mice showed full correction of skeletal phenotype at 4 × 1010 vg/b. We observed full correction of the bone phenotype at 4 × 108 and 4 × 109 in female AlplPrx1/Prx1 mice, but bones remained hypomineralized with the 4 × 106 and 4 × 107 (vg/b) doses after 70 d of treatment. We observed skeletal improvements using the 4 × 109 (vg/b) dose, but the phenotype was not fully corrected in male AlplPrx1/Prx1. Immunohistochemistry using anti-TNAP and anti-D10 antibodies showed high immunolocalization in the femurs of female AlplPrx1/Prx1 mice, while D10 immunolocalization was high in the liver of male AlplPrx1/Prx1 mice at a dose of 4 × 109 (vg/b). This sex-dependent difference was not seen in the infantile HPP model. A serum proteome analysis showed enhanced inflammatory pathways in treated AlplPrx1/Prx1 males compared to treated female mice. We also found a few areas of ectopic calcification in soft organs at the highest tested dose of 4 × 1010 (vg/b) in Alpl-/- or 4 × 109 (vg/b) in the AlplPrx1/Prx1 model. This pre-clinical study will inform the design of clinical trials to develop gene therapy in early-onset and late-onset HPP patients.

Keywords: AAV8-TNAP-D10skeletal mineralization; adult-HPP; gene therapy; hypophosphatasia; infantile-HPP; inflammation.

Plain language summary

We previously showed the efficacy of a single injection of a specially designed viral vector to deliver mineral-targeted TNAP into young and adult mice displaying HPP to prevent/ameliorate their bone and dental defects. In this study, the treatment showed dose-dependent improvements, with higher doses fully correcting bone problems in some cases. However, responses varied by sex and age, with some males showing less improvement and more inflammation. These pre-clinical findings will inform the design of clinical trials using gene therapy in early- and late-onset HPP patients.

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Conflict of interest statement

J.L.M. and K.M. are co-inventors of a patent application for the use of viral-mediated administration of mineral-targeted TNAP for the treatment of HPP and pseudo-HPP. Other authors disclose no conflicts of interest related to this work.

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