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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 .

In this study of perinatal and infantile hypophosphatasia, patients received ENB-0040, a bone-targeted, recombinant, human tissue-nonspecific isozyme of alkaline phosphatase that is lacking in this disease. Rickets healed, and developmental milestones and pulmonary function improved. Hypophosphatasia is the inborn error of metabolism that is characterized by low serum alkaline-phosphatase activity from loss-of-function mutations, typically missense, within the gene for the tissue-nonspecific isozyme of alkaline phosphatase (TNSALP). 1 Natural substrates of TNSALP that accumulate in hypophosphatasia include inorganic pyrophosphate, 2 an inhibitor of mineralization, 3 and pyridoxal 5′-phosphate (PLP), the principal circulating form of vitamin B 6 . 4 High extracellular levels of inorganic pyrophosphate block hydroxyapatite crystal growth 3 , 5 and cause rickets or osteomalacia. Hypercalcemia and hyperphosphatemia can develop in severely affected patients. 1 The deranged vitamin B 6 metabolism shows that TNSALP functions as a cell-surface enzyme 6 and explains . . .

Background Centronuclear myopathies are severe rare congenital diseases. The clinical variability and genetic heterogeneity of these myopathies result in major challenges in clinical trial design. Alternative strategies to large placebo-controlled trials that have been used in other rare diseases (e.g., the use of surrogate markers or of historical controls) have limitations that Bayesian statistics may address. Here we present a Bayesian model that uses each patient’s own natural history study data to predict progression in the absence of treatment. This prospective multicentre natural history evaluated 4-year follow-up data from 59 patients carrying mutations in the MTM1 or DNM2 genes. Methods Our approach focused on evaluation of forced expiratory volume in 1 s (FEV1) in 6- to 18-year-old children. A patient was defined as a responder if an improvement was observed after treatment and the predictive probability of such improvement in absence of intervention was less than 0.01. An FEV1 response was considered clinically relevant if it corresponded to an increase of more than 8%. Results The key endpoint of a clinical trial using this model is the rate of response. The power of the study is based on the posterior probability that the rate of response observed is greater than the rate of response that would be observed in the absence of treatment predicted based on the individual patient’s previous natural history. In order to appropriately control for Type 1 error, the threshold probability by which the difference in response rates exceeds zero was adapted to 91%, ensuring a 5% overall Type 1 error rate for the trial. Conclusions Bayesian statistical analysis of natural history data allowed us to reliably simulate the evolution of symptoms for individual patients over time and to probabilistically compare these simulated trajectories to actual observed post-treatment outcomes. The proposed model adequately predicted the natural evolution of patients over the duration of the study and will facilitate a sufficiently powerful trial design that can cope with the disease’s rarity. Further research and ongoing dialog with regulatory authorities are needed to allow for more applications of Bayesian statistics in orphan disease research.