Enzyme-replacement therapy in life-threatening hypophosphatasia.

BACKGROUND: Hypophosphatasia results from mutations in the gene for the tissue-nonspecific isozyme of alkaline phosphatase (TNSALP). Inorganic pyrophosphate accumulates extracellularly, leading to rickets or osteomalacia. Severely affected babies often die from respiratory insufficiency due to progressive chest deformity or have persistent bone disease. There is no approved medical therapy. ENB-0040 is a bone-targeted, recombinant human TNSALP that prevents the manifestations of hypophosphatasia in Tnsalp knockout mice. METHODS: We enrolled infants and young children with life-threatening or debilitating perinatal or infantile hypophosphatasia in a multinational, open-label study of treatment with ENB-0040. The primary objective was the healing of rickets, as assessed by means of radiographic scales. Motor and cognitive development, respiratory function, and safety were evaluated, as well as the pharmacokinetics and pharmacodynamics of ENB-0040. RESULTS: Of the 11 patients recruited, 10 completed 6 months of therapy; 9 completed 1 year. Healing of rickets at 6 months in 9 patients was accompanied by improvement in developmental milestones and pulmonary function. Elevated plasma levels of the TNSALP substrates inorganic pyrophosphate and pyridoxal 5'-phosphate diminished. Increases in serum parathyroid hormone accompanied skeletal healing, often necessitating dietary calcium supplementation. There was no evidence of hypocalcemia, ectopic calcification, or definite drug-related serious adverse events. Low titers of anti-ENB-0040 antibodies developed in four patients, with no evident clinical, biochemical, or autoimmune abnormalities at 48 weeks of treatment. CONCLUSIONS: ENB-0040, an enzyme-replacement therapy, was associated with improved findings on skeletal radiographs and improved pulmonary and physical function in infants and young children with life-threatening hypophosphatasia. (Funded by Enobia Pharma and Shriners Hospitals for Children; ClinicalTrials.gov number, NCT00744042.).

A prospective short-term study to evaluate methodologies for the assessment of disease extent, impact, and wound evolution in patients with dystrophic epidermolysis bullosa.

BACKGROUND: Standardized assessments for dystrophic epidermolysis bullosa (DEB) are needed. This prospective, multicenter, 4-week, observational study was designed to evaluate DEB assessments for suitability as clinical trial endpoints. METHODS: Patients with confirmed DEB diagnosis and ≥ 5 measurable wounds were included. The primary outcome was change from baseline in wound surface area (WSA) of 5 selected wounds by 3-dimensional imaging. Secondary endpoints were change from baseline in clinician global assessment (CGA) of WSA, wound characteristics, disease-related questionnaires and instruments (disease severity, quality of life [QoL], pain and disability, and itch), and tolerability of procedures. RESULTS: Of 30 enrolled patients, 29 completed the study (of whom, 28 had recessive DEB). Median age was 17.8 years (range, 3.8-58.7). All patients developed new or recurrent wounds during the 4-week study. Of the wounds selected at baseline, 45/150 (30.0%) healed by week 2; an additional 38 healed by week 4, while 8 of those healed at week 2 had recurred by week 4 for a total of 75/150 (50.0%) healed wounds at week 4. Mean values for WSA, CGA, and disease-related questionnaire and instrument scores remained steady during this 4-week observational study. Of the 10 disease-related questionnaires and instruments assessed, the scores for the Epidermolysis Bullosa Disease Activity and Scarring Index (EBDASI) and the Instrument for Scoring Clinical Outcomes for Research of Epidermolysis Bullosa (iscorEB) did not substantially overlap between moderate and severe disease. Between mild and moderate disease, only the EBDASI scores did not substantially overlap. CONCLUSIONS: These results stress the dynamic nature of wounds, even during a 4-week period of observation, and suggest that a combination of clinician-assessed outcomes and patient-/caregiver-reported outcomes is needed to provide a comprehensive assessment of DEB severity and impact. In addition, these results support the use of EBDASI and iscorEB to monitor disease severity as both produced scores that did not substantially overlap between disease severity strata. Clinical trial registration ClinicalTrials.gov, NCT02178969 . Registered 4 June 2014, https://clinicaltrials.gov/ct2/show/NCT02178969 .

X-linked myotubular myopathy: A prospective international natural history study.

OBJECTIVES: Because X-linked myotubular myopathy (XLMTM) is a rare neuromuscular disease caused by mutations in the MTM1 gene with a large phenotypic heterogeneity, to ensure clinical trial readiness, it was mandatory to better quantify disease burden and determine best outcome measures. METHODS: We designed an international prospective and longitudinal natural history study in patients with XLMTM and assessed muscle strength and motor and respiratory functions over the first year of follow-up. The humoral immunity against adeno-associated virus serotype 8 was also monitored. RESULTS: Forty-five male patients aged 3.5 months to 56.8 years were enrolled between May 2014 and May 2017. Thirteen patients had a mild phenotype (no ventilation support), 7 had an intermediate phenotype (ventilation support less than 12 hours a day), and 25 had a severe phenotype (ventilation support 12 or more hours a day). Most strength and motor function assessments could be performed even in very weak patients. Motor Function Measure 32 total score, grip and pinch strengths, and forced vital capacity, forced expiratory volume in the first second of exhalation, and peak cough flow measures discriminated the 3 groups of patients. Disease history revealed motor milestone loss in several patients. Longitudinal data on 37 patients showed that the Motor Function Measure 32 total score significantly decreased by 2%. Of the 38 patients evaluated, anti-adeno-associated virus type 8 neutralizing activity was detected in 26% with 2 patients having an inhibitory titer >1:10. CONCLUSIONS: Our data confirm that XLMTM is slowly progressive for male survivors regardless of their phenotype and provide outcome validation and natural history data that can support clinical development in this population. CLINICALTRIALSGOV IDENTIFIER: NCT02057705.

Outcome of perinatal hypophosphatasia in manitoba mennonites: a retrospective cohort analysis.

Hypophosphatasia (HPP) is the metabolic bone disease caused by loss-of-function mutation within the gene that encodes the "tissue nonspecific" isoenzyme of alkaline phosphatase (TNSALP). Perinatal HPP is usually fatal due to respiratory insufficiency, and infantile HPP often has a similar outcome although no formal study into the natural history of these severe forms of HPP has been undertaken. We reviewed our 80-year (1927-2007) cohort of 15 Canadian patients with perinatal HPP. All had Mennonite heritage. Family linkage studies indicated that nine were homozygous for a TNSALP disease allele, likely Gly334Asp. Three patients had parents who were carriers for the Gly334Asp allele by mutation analysis. One patient was confirmed by mutation analysis to be homozygous for the TNSALP Gly334Asp mutation. One patient who had only one Mennonite parent was a genetic compound for the Gly334Asp mutation and the Val382Ile mutation. This patient's sibling was also affected. All 15 patients had profound skeletal hypomineralization, severe rickets, and respiratory insufficiency. All died by 9 months of age, usually soon after birth, from pulmonary failure.