Dataset Information

Bone turnover and mineral metabolism in adult patients with hypophosphatasia treated with asfotase alfa.

ABSTRACT: There is limited understanding of how asfotase alfa affects mineral metabolism and bone turnover in adults with pediatric-onset hypophosphatasia. This study showed that adults with hypophosphatasia treated with asfotase alfa experienced significant changes in biochemical markers of bone and mineral metabolism, possibly reflecting enhanced bone remodeling of previously osteomalacic bone.

Introduction

Hypophosphatasia (HPP), due to a tissue nonspecific alkaline phosphatase (TNSALP) deficiency, can cause impaired bone mineralization and turnover. Although HPP may be treated with asfotase alfa, an enzyme replacement therapy, limited data are available on how treatment with asfotase alfa affects mineral metabolism and bone turnover in adults with HPP.

Methods

ALP substrates, bone turnover and mineral metabolism markers, and bone mineral density (BMD) data from EmPATHY, a single-center, observational study of adults (≥ 18 years) with pediatric-onset HPP treated with asfotase alfa (NCT03418389), were collected during routine clinical care and analyzed from baseline through 24 months of treatment.

Results

Data from 21 patients showed significantly increased ALP activity and reduced urine phosphoethanolamine (PEA)/creatinine (Cr) ratios after baseline through 24 months of asfotase alfa treatment. There were significant transient increases in parathyroid hormone 1-84 (PTH), osteocalcin, and procollagen type 1 N-propeptide (P1NP) levels at 3 and 6 months and in tartrate-resistant acid phosphatase 5b (TRAP5b) levels at 3 months, with a significant decrease in N-terminal telopeptide of type 1 collagen (NTX) levels at 24 months. Lumbar spine BMD T scores continuously increased during treatment.

Conclusion

Significant changes in bone turnover and mineral metabolism markers after asfotase alfa treatment suggest that treatment-mediated mineralization may enable remodeling and bone turnover on previously unmineralized surfaces. Urine PEA/Cr ratios may be a useful parameter in monitoring treatment during routine care.

SUBMITTER: Seefried L

PROVIDER: S-EPMC8608777 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background. Hypophosphatasia (HPP) is caused by loss-of-function mutation(s) of the gene that encodes the tissue-nonspecific isoenzyme of alkaline phosphatase (TNSALP). Consequently, cell-surface deficiency of TNSALP phosphohydrolase activity leads to extracellular accumulation of inorganic pyrophosphate, a natural substrate of TNSALP and inhibitor of mineralization. Children with HPP can manifest rickets, skeletal pain, deformity, fracture, muscle weakness, and premature deciduous tooth loss. Asfotase alfa is a recombinant, bone-targeted, human TNSALP injected s.c. to treat HPP. In 2012, we detailed the 1-year efficacy of asfotase alfa therapy for the life-threatening perinatal and infantile forms of HPP. Methods. Here, we evaluated the efficacy and safety of asfotase alfa treatment administered to children 6-12 years of age at baseline who were substantially impaired by HPP. Two radiographic scales quantitated HPP skeletal disease, including comparisons to serial radiographs from similarly affected historical control patients. Results. Twelve children receiving treatment were studied for 5 years. The 6-month primary endpoint was met, showing significant radiographic improvement. Additional significant improvements included patient growth, strength, motor function, agility, and quality of life, which for most patients meant achieving normal values for age- and sex-matched peers that were sustained at 5 years of treatment. For most, pain and disability resolved. Mild to moderate injection-site reactions were common and were sometimes associated with lipohypertrophy. Low anti-asfotase alfa antibody titers were noted in all patients. No evidence emerged for clinically important ectopic calcification or treatment resistance. Conclusions. Asfotase alfa enzyme replacement therapy has substantial and sustained efficacy with a good safety profile for children suffering from HPP. Trial Registration. ClinicalTrials.gov NCT00952484 (https://clinicaltrials.gov/ct2/show/NCT00952484) and NCT01203826 (https://clinicaltrials.gov/ct2/show/NCT01203826). Funding. Alexion Pharmaceuticals Inc. and Shriners Hospitals for Children.

Project description:In adult hypophosphatasia (HPP) patients, elevated lumbar spine dual X-ray absorptiometry (DXA) values are associated with markers of disease severity and disease-specific fracture risk while femoral bone mineral density (BMD), being largely unaffected by the disease severity, may still be useful to monitor other causes of increased fracture risk due to low BMD.IntroductionHypophosphatasia (HPP) is a rare inherited metabolic disorder due to deficient activity of the tissue-nonspecific alkaline phosphatase (TNAP). Clinical manifestation in adult HPP patients is manifold including an increased risk for fractures, but data regarding clinical significance of DXA measurement and associations with fracture risk and disease severity is scarce.MethodsRetrospective single-center analysis of DXA scans in patients with confirmed HPP (documented mutation, clinical symptoms, low alkaline phosphatase activity). Further data evaluation included disease-related fractures, laboratory results (alkaline phosphatase, pyridoxalphosphate, phosphoethanolamine), and medical history.ResultsAnalysis included 110 patients (84 female, mean age of 46.2 years) of whom 37.3% (n = 41) were harboring two mutations. Average T-Score level at the lumbar spine was - 0.1 (SD 1.9), and mean total hip T-Score was - 1.07 (SD 0.15). Both lower ALP activity and higher substrate levels (pyridoxalphosphate and phosphoethanolamine) were significantly correlated with increased lumbar spine T-Score levels (p < 0.001) while BMD at the hip was not affected by indicators of disease severity. Increased lumbar spine BMD was significantly associated with an increased risk for HPP-related fractures, prevalent in 22 (20%) patients (p < 0.001) with 21 of them having biallelic mutations.ConclusionBMD in adult HPP patients is not systematically reduced. Conversely, increased lumbar spine BMD appears to be associated with severely compromised mineralization and increased risk for HPP-related fractures while BMD at the hip appears unaffected by indicators of disease severity, suggesting suitability of this anatomic location for assessing and discerning disorders with increased fracture risk owing to reduced BMD like osteoporosis.Trial registration numberGerman register for clinical studies (DRKS00014022) DATE OF REGISTRATION: 02/10/2018 - retrospectively registered.

Project description:Hypophosphatasia (HPP) is a rare, inherited, metabolic disease characterized by tissue-nonspecific alkaline phosphatase deficiency resulting in musculoskeletal and systemic clinical manifestations. This observational study evaluated the effectiveness of enzyme replacement therapy with asfotase alfa on physical function and health-related quality of life (HRQoL) among adults with pediatric-onset HPP who received asfotase alfa for 12?months at a single center (ClinicalTrial.gov no.: NCT03418389). Primary outcomes evaluated physical function with the 6-minute walk test (6MWT), timed up-and-go (TUG) test, Short Physical Performance Battery (SPPB), and handheld dynamometry (HHD). Secondary outcome measures included the Lower Extremity Functional Scale (LEFS), pain prevalence/intensity, and pain medication use; HRQoL was evaluated using the 36-Item Short-Form Health Survey version 2 (SF-36v2). Safety data were collected throughout the study. All 14 patients (11 women) had compound heterozygous ALPL gene mutations and??1 HPP bone manifestation, including history of ?1 fracture. Mean (min, max) age was 51 (19 to 78) years. From baseline to 12?months of treatment, median 6MWT distance increased from 267?m to 320?m (n = 13; p = 0.023); median TUG test time improved from 14.4?s to 11.3?s (n = 9; p = 0.008). Specific components of the SPPB also improved significantly: median 4-m gait speed increased from 0.8?m/s to 1.1?m/s (n = 10; p = 0.007) and median repeated chair-rise time improved from 22?s to 13?s (n = 9; p = 0.008). LEFS score improved from 24 points to 53 points (n = 10; p = 0.002). Improvements in HHD were not clinically significant. SF-36v2 Physical Component Score (PCS) improved after 12?months of treatment (n = 9; p = 0.010). Pain level did not change significantly from baseline to 12?months of treatment. There were significant improvements on chair-rise time and SF-36v2 PCS by 3?months, and on TUG test time after 6?months. No new safety signals were identified. These results show the real-world effectiveness of asfotase alfa in improving physical functioning and HRQoL in adults with pediatric-onset HPP. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.