Study methodology and insights from the palovarotene clinical development program in fibrodysplasia ossificans progressiva.

BACKGROUND: The design of clinical trials in rare diseases is often complicated by a lack of real-world translational knowledge. Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare genetic disorder characterized by skeletal malformations and progressive heterotopic ossification (HO). Palovarotene is a selective retinoic acid receptor gamma agonist. Here, we describe the methodology of three studies in the palovarotene clinical development program in FOP and discuss insights that could inform future research, including endpoint suitability and the impact of trial design. METHODS: PVO-1A-001 (NCT02322255) was a prospective, protocol-specified, longitudinal FOP natural history study (NHS). PVO-1A-201 (NCT02190747) was a randomized, double-blind, placebo-controlled phase II trial; PVO-1A-202 (NCT02279095) was its open-label extension. Trial designs, including treatment regimens and imaging assessments, were refined between PVO-1A-201 and PVO-|1A-202, and within PVO-1A-202, based on emerging data as the studies progressed. Palovarotene doses were administered using a flare-up treatment regimen (higher dose for 2/4 weeks, followed by lower dose for 4/≥8 weeks; from flare-up onset), with or without accompanying chronic (daily) treatment. Flare-up and disease progression outcomes were assessed, including incidence and volume of new HO during flare-ups and/or annually, as well as other clinical, patient-reported, and exploratory outcomes. Safety was monitored throughout all studies. RESULTS: Overall, 114 and 58 individuals with FOP were enrolled in the NHS and phase II trials, respectively. Results of the NHS and PVO-1A-201 were published in 2022; complete results of PVO-1A-202 will be publicly available in due course. Together the studies yielded important information on endpoint suitability, including that low-dose whole-body computed tomography was the optimum imaging modality for assessing HO progression annually and that long study durations are needed to detect substantial changes in functional and patient-reported outcomes. CONCLUSIONS: A flexible clinical development program is necessary for underexplored rare diseases to overcome the many challenges faced. Here, the NHS provided a longitudinal evaluation of FOP progression and interventional trials were based on emerging data. The studies described informed the design and endpoints implemented in the phase III MOVE trial (NCT03312634) and provide a foundation for future clinical trial development. TRIAL REGISTRATION: NCT02322255 (registered 23/12/2014); NCT02190747 (registered 15/07/2014); NCT02279095 (registered 30/10/2014).

The natural history of fibrodysplasia ossificans progressiva: A prospective, global 36-month study.

PURPOSE: We report the first prospective, international, natural history study of the ultra-rare genetic disorder fibrodysplasia ossificans progressiva (FOP). FOP is characterized by painful, recurrent flare-ups, and disabling, cumulative heterotopic ossification (HO) in soft tissues. METHODS: Individuals aged ≤65 years with classical FOP (ACVR1R206H variant) were assessed at baseline and over 36 months. RESULTS: In total, 114 individuals participated; 33 completed the study (mean follow up: 26.8 months). Median age was 15.0 (range: 4-56) years; 54.4% were male. During the study, 82 (71.9%) individuals reported 229 flare-ups (upper back: 17.9%, hip: 14.8%, shoulder: 10.9%). After 84 days, 14 of 52 (26.9%) imaged flare-ups had new HO at the flare-up site (mean new HO volume: 28.8 × 103 mm3). Mean baseline low-dose whole-body computed tomography (excluding head) HO volume was 314.4 × 103 mm3; lowest at 2 to <8 years (68.8 × 103 mm3) and increasing by age (25-65 years: 575.2 × 103 mm3). The mean annualized volume of new HO was 23.6 × 103 mm3/year; highest at 8 to <15 and 15 to <25 years (21.9 × 103 and 41.5 × 103 mm3/year, respectively) and lowest at 25 to 65 years (4.6 × 103 mm3/year). CONCLUSION: Results from individuals receiving standard care for up to 3 years in this natural history study show the debilitating effect and progressive nature of FOP cross-sectionally and longitudinally, with greatest progression during childhood and early adulthood.

Delayed diagnosis in children with intracranial germ cell tumors.

OBJECTIVE: To review symptoms and provider history in a large cohort of patients with germ cell tumors (GCTs) to highlight the variety of manifestations and assess the effect of delayed diagnosis on outcomes. STUDY DESIGN: Patients treated for intracranial pure germinoma and nongerminomatous GCTs at Massachusetts General Hospital between 1998 and 2012 were included (n = 70). The primary outcome was time from onset of symptoms to diagnostic imaging. Delay was defined as an interval of ≥ 6 months. RESULTS: The median duration of symptoms before diagnostic magnetic resonance imaging was 6 months (range, 2 days to 72 months). Thirty-eight of the 70 patients (54%) had a delayed diagnosis. Patients with suprasellar tumors presented with symptoms related to endocrinopathies, and patients with pineal region tumors presented with symptoms related to hydrocephalus. Most of the patients were evaluated by a general pediatrician (49%) and/or pediatric subspecialists (66%) before diagnosis. Patients with delayed diagnosis saw a greater number of physicians before diagnosis (P = .006). The majority of patients (63%) with delayed diagnosis were seen by 2 or more physicians, and many (40%) were seen by 2 or more subspecialists. Progression-free survival was similar in the patients with delayed diagnosis and those without delayed diagnosis (P = .90), but the former were more likely to present with disseminated disease at diagnosis (34% vs 6%; P = .007). CONCLUSION: A significant proportion of patients with GCT experience a delay in time to diagnosis, in some cases despite evaluation by general pediatricians and specialists. This delay increases the risk of disseminated disease.

The Pharmacokinetic Profile of Palovarotene: An Open-Label Phase I Trial Investigating the Effect of Food and Potential for Drug-Drug Interaction in Healthy Participants.

BACKGROUND AND OBJECTIVES: Palovarotene is under development for the treatment of fibrodysplasia ossificans progressiva (FOP). The objectives of this study were to evaluate palovarotene pharmacokinetics under fed versus fasted conditions and its induction potential towards cytochrome P450 3A4 (CYP3A4) substrate, midazolam. METHODS: In this phase I, open-label trial (NCT04829773), palovarotene pharmacokinetics were characterized after repeated once-daily dosing. In one cohort, healthy participants received three doses of palovarotene 20 mg on Days 1, 6, and 11, as whole capsules under fasted or fed conditions, or sprinkled on food under fed conditions. In another cohort, individuals received midazolam 2 mg on Days 1 and 15 and a daily dose of palovarotene 20 mg on Days 2-15. Palovarotene and midazolam pharmacokinetics, including area under the concentration-time curve from time zero to infinity (AUC(0-∞)) and maximum observed plasma drug concentration (Cmax), were assessed. Adverse events (AEs) were recorded. RESULTS: Overall, 23 participants completed each part. Palovarotene Cmax and AUC(0-∞) increased by 16.5% and 39.7% under fed versus fasted conditions. Pharmacokinetics were comparable between the whole capsule and sprinkled on food, under fed conditions. Midazolam AUC(0-∞) and Cmax decreased by 13.3% and 9.7% upon palovarotene co-administration over 14 days, less than that required to be considered a weak CYP3A4 inducer. Plasma palovarotene exposures were comparable after single and multiple doses. No serious AEs were reported. CONCLUSIONS: These data support palovarotene administration after a meal, as a whole capsule or sprinkled on food. Palovarotene at 20 mg/day is a not a clinical inducer of CYP3A4. These results provide insights into palovarotene pharmacokinetics, aiding optimization of administration for patients with FOP. CLINICAL TRIALS REGISTRATION NUMBER: NCT04829773.

Fibrodysplasia ossificans progressiva, also known as FOP, is a very rare genetic condition where bone forms in places it is not usually found, such as in the muscles, tendons, and ligaments. Retinoids are molecules that the body produces from vitamin A to aid normal bone development. Palovarotene is a therapeutic retinoid that has been developed for the treatment of FOP. This article describes a clinical trial where people without FOP received oral palovarotene to determine how it is absorbed and broken down (metabolized) by the body when taken after a meal or after fasting (a period of not eating) as a whole capsule or when sprinkled on food. The trial also examined how palovarotene might interact with other treatments that are broken down by the body in the same way as palovarotene.The trial found that the amount of palovarotene that circulates in the blood increased more when taken after a meal compared with after fasting. Palovarotene was metabolized by the body in a similar way when taken as a whole capsule or when sprinkled on food. This finding is important as some people with FOP have difficulty swallowing. At a 20 mg dose, palovarotene was unlikely to interact with other treatments that are metabolized in the same way. No serious side effects were reported.These results show that palovarotene should be taken after a meal, either as a whole capsule or sprinkled on food.

Reduction of New Heterotopic Ossification (HO) in the Open-Label, Phase 3 MOVE Trial of Palovarotene for Fibrodysplasia Ossificans Progressiva (FOP).

Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare, severely disabling genetic disorder of progressive heterotopic ossification (HO). The single-arm, open-label, phase 3 MOVE trial (NCT03312634) assessed efficacy and safety of palovarotene, a selective retinoic acid receptor gamma agonist, in patients with FOP. Findings were compared with FOP natural history study (NHS; NCT02322255) participants untreated beyond standard of care. Patients aged ≥4 years received palovarotene once daily (chronic: 5 mg; flare-up: 20 mg for 4 weeks, then 10 mg for ≥8 weeks; weight-adjusted if skeletally immature). The primary endpoint was annualized change in new HO volume versus NHS participants (by low-dose whole-body computed tomography [WBCT]), analyzed using a Bayesian compound Poisson model (BcPM) with square-root transformation. Twelve-month interim analyses met futility criteria; dosing was paused. An independent Data Monitoring Committee recommended trial continuation. Post hoc 18-month interim analyses utilized BcPM with square-root transformation and HO data collapsed to equalize MOVE and NHS visit schedules, BcPM without transformation, and weighted linear mixed-effects (wLME) models, alongside prespecified analysis. Safety was assessed throughout. Eighteen-month interim analyses included 97 MOVE and 101 NHS individuals with post-baseline WBCT. BcPM analyses without transformation showed 99.4% probability of any reduction in new HO with palovarotene versus NHS participants (with transformation: 65.4%). Mean annualized new HO volume was 60% lower in MOVE versus the NHS. wLME results were similar (54% reduction fitted; nominal p = 0.039). All palovarotene-treated patients reported ≥1 adverse event (AE); 97.0% reported ≥1 retinoid-associated AE; 29.3% reported ≥1 serious AE, including premature physeal closure (PPC)/epiphyseal disorder in 21/57 (36.8%) patients aged <14 years. Post hoc computational analyses using WBCT showed decreased vertebral bone mineral density, content, and strength, and increased vertebral fracture risk in palovarotene-treated patients. Thus, post hoc analyses showed evidence for efficacy of palovarotene in reducing new HO in FOP, but high risk of PPC in skeletally immature patients. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Evaluation of Opioid Overdose Reports in Patients Treated with Extended-Release Naltrexone: Postmarketing Data from 2006 to 2018.

INTRODUCTION: After treatment with naltrexone extended-release injectable suspension (XR-NTX), a µ-opioid receptor antagonist, opioid tolerance is reduced from pretreatment baseline. Patients may be vulnerable to opioid overdose if they attempt to override the blockade during treatment, at the end of a dosing interval, after missing a dose, or after discontinuing treatment. OBJECTIVE: We analyzed postmarketing data to characterize reporting rates of opioid overdose during treatment with and after discontinuation of XR-NTX. METHODS: Postmarketing adverse event reports within the XR-NTX safety database, received 2006-2018, for patients treated with XR-NTX for any indication were reviewed for opioid overdose cases. Assessable cases were categorized by timing of the event from the last dose of XR-NTX (latency): ≤28 days (on treatment), 29-56 days, and >56 days from last dose of XR-NTX. Within each latency group, cases were further classified as serious and, of those, cases that had a fatal outcome. RESULTS: During the 12-year period, an estimated 495,602 patients received XR-NTX. Opioid overdose was reported in 161 cases; of these, 66 contained sufficient information to determine latency. Reporting rates of opioid overdose per 10,000 patients treated were similar among latency groups: 0.54 for ≤28 days (0.24 fatal), 0.34 for 29-56 days (0.16 fatal), and 0.44 for >56 days (0.40 fatal) from the last dose of XR-NTX. CONCLUSIONS: Over the 12-year period, the reporting rates of opioid overdose were similar during treatment with or after discontinuation of XR-NTX and <10/10,000 patients exposed. Our findings are limited by the nature of spontaneously reported safety data.

Reply to "Why Secondary Analyses in Vitamin D Clinical Trials Are important and How to Improve Vitamin D Clinical Trial Outcome Analyses-A Comment on "Extra-Skeletal Effects of Vitamin D", Nutrients 2019, 11, 1460".

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Extra-Skeletal Effects of Vitamin D.

The vitamin D receptor is expressed in multiple cells of the body (other than osteoblasts), including beta cells and cells involved in immune modulation (such as mononuclear cells, and activated T and B lymphocytes), and most organs in the body including the brain, heart, skin, gonads, prostate, breast, and gut. Consequently, the extra-skeletal impact of vitamin D deficiency has been an active area of research. While epidemiological and case-control studies have often suggested a link between vitamin D deficiency and conditions such as type 1 and type 2 diabetes, connective tissue disorders, inflammatory bowel disorders, chronic hepatitis, food allergies, asthma and respiratory infections, and cancer, interventional studies for the most part have failed to confirm a causative link. This review examines available evidence to date for the extra-skeletal effects of vitamin D deficiency, with a focus on randomized controlled trials and meta-analyses.

The Natural History of Adrenal Insufficiency in X-Linked Adrenoleukodystrophy: An International Collaboration.

Context: Primary adrenal insufficiency is an important clinical manifestation of X-linked adrenoleukodystrophy (ALD). Other manifestations include spinal cord disease and/or inflammatory demyelinating cerebral disease. Implementation of newborn screening requires natural history data to develop follow-up recommendations. Objective: To delineate the natural history of adrenal insufficiency in male patients with ALD and to assess associations between the risk for developing adrenal insufficiency, spinal cord disease, or cerebral disease and plasma C26:0/C22:0 and C24:0/C22:0 ratios, which are diagnostic biomarkers for ALD. Design: Retrospective review of medical records. Setting: Two international tertiary referral centers of expertise for ALD. Patients: Male patients with ALD followed at the centers between 2002 and 2016. Main Outcome Measures: The primary endpoint was adrenal insufficiency; secondary endpoints were spinal cord and cerebral disease. Results: Data on 159 male patients was available. The probability of developing adrenal insufficiency was described with survival analysis. Median time until adrenal insufficiency was 14 years (95% CI, 9.70 to 18.30 years). The cumulative proportion of patients who developed adrenal insufficiency was age-dependent and highest in early childhood [0 to 10 years, 46.8% (SEM 0.041%); 11 to 40 years, 28.6% (SEM, 0.037%); >40 years, 5.6% (SEM, 0.038%)]. No association between clinical manifestations and plasma ratios was detected with Cox model or Spearman correlation. Conclusions: Lifetime prevalence of adrenal insufficiency in male patients with ALD is ~80%. Adrenal insufficiency risk is time-dependent and warrants age-dependent follow-up. Besides on-demand testing if symptoms manifest, we suggest a minimum of adrenal testing every 4 to 6 months for patients age ≤10 years, annual testing for those age 11 to 40 years, and solely on-demand testing for those age >40 years.

Catch-up growth after hypothyroidism is caused by delayed growth plate senescence.

Catch-up growth is defined as a linear growth rate greater than expected for age after a period of growth inhibition. We hypothesized that catch-up growth occurs because growth-inhibiting conditions conserve the limited proliferative capacity of growth plate chondrocytes, thus slowing the normal process of growth plate senescence. When the growth-inhibiting condition resolves, the growth plates are less senescent and therefore grow more rapidly than normal for age. To test this hypothesis, we administered propylthiouracil to newborn rats for 8 wk to induce hypothyroidism and then stopped the propylthiouracil to allow catch-up growth. In untreated controls, the growth plates underwent progressive, senescent changes in multiple functional and structural characteristics. We also identified genes that showed large changes in mRNA expression in growth plate and used these changes as molecular markers of senescence. In treated animals, after stopping propylthiouracil, these functional, structural, and molecular senescent changes were delayed, compared with controls. This delayed senescence included a delayed decline in longitudinal growth rate, resulting in catch-up growth. The findings demonstrate that growth inhibition due to hypothyroidism slows the developmental program of growth plate senescence, including the normal decline in the rate of longitudinal bone growth, thus accounting for catch-up growth.

Adrenoleukodystrophy: Guidance for Adrenal Surveillance in Males Identified by Newborn Screen.

Context: Adrenoleukodystrophy (ALD) is a peroxisomal disorder associated with neurologic decompensation and adrenal insufficiency. Newborn screening for ALD has recently been implemented in five states with plans to expand to all 50 states in the United States. Adrenal insufficiency ultimately develops in most males with ALD, but the earliest age of onset is not well established. Objective: These clinical recommendations are intended to address screening for adrenal insufficiency in boys identified to have ALD by newborn screen. Participants: Seven members of the Pediatric Endocrine Society Drug and Therapeutics/Rare Diseases Committee, with clinical experience treating children with ALD and adrenal insufficiency, and a pediatric endocrinologist and laboratory director were selected to be on the working committee. Consensus Process: The authors comprised the working group and performed systematic reviews of the published literature regarding adrenal insufficiency and ALD. The recommendations were reviewed and approved by the larger Pediatric Endocrine Society Drug and Therapeutics/Rare Diseases Committee and then by the Pediatric Endocrine Society Board of Directors. Conclusions: There is limited literature evidence regarding monitoring of evolving adrenal insufficiency in male infants and children with ALD. The recommendations suggest initiating assessment of adrenal function at diagnosis with ALD and regular monitoring to identify boys with adrenal insufficiency in a timely manner and prevent life-threatening adrenal crisis. These recommendations are intended to serve as an initial guide, with the understanding that additional experience will inform future guidelines.

Growth plate biology: new insights.

PURPOSE OF REVIEW: To discuss the most recent findings of growth plate regulation and physiology. The mechanism of endochondrial bone growth is incompletely understood and continues to be an active area of research. RECENT FINDINGS: In this review, new understandings of growth plate chondrocyte regulation of proliferation, differentiation and ossification are discussed. Through genetic studies potential signaling pathways are proposed and new insights into hormonal influences on growth are offered. New potential genetic pathways regulating growth are suggested and finally skeletal dysplasia and potential emerging treatment are considered. SUMMARY: The findings discussed here continue to build the understanding of the mechanisms of growth. As our knowledge increases potential treatments for growth inhibiting conditions can be developed.

Bone health in primary ovarian insufficiency.

The etiology of primary ovarian insufficiency (POI) may be genetic, autoimmune, or iatrogenic. Genetic conditions include 45,X, 46,XX and 46,XY POI, and POI associated with galactosemia and FMR premutations. Women with autoimmune polyglandular syndromes 1 and 2 may develop autoimmune POI, as may those who receive chemotherapy or radiotherapy. Hypogonadism in POI can result in reduced rates of bone mass accrual in adolescents and young women, and low bone density for age in older women. Measures to optimize bone density in women with POI include attention to lifestyle measures and hormone replacement. Resistance training and adequate calcium and vitamin D supplementation are essential, as is replacement of estrogen/progestin. Estrogen/progestin replacement may be problematic in women with estrogen-sensitive breast cancer who developed POI in the course of therapy for cancer. In these instances, bisphosphonates are an option. In particular, zoledronic acid has been used successfully in conjunction with chemotherapy, tamoxifen, and aromatase inhibitors.

An extensive genetic program occurring during postnatal growth in multiple tissues.

Mammalian somatic growth is rapid in early postnatal life but then slows and eventually ceases in multiple tissues. We hypothesized that there exists a postnatal gene expression program that is common to multiple tissues and is responsible for this coordinate growth deceleration. Consistent with this hypothesis, microarray analysis identified more than 1600 genes that were regulated with age (1 vs. 4 wk) coordinately in kidney, lung, and heart of male mice, including many genes that regulate proliferation. As examples, we focused on three growth-promoting genes, Igf2, Mest, and Peg3, that were markedly down-regulated with age. In situ hybridization revealed that expression occurred in organ-specific parenchymal cells and suggested that the decreasing expression with age was due primarily to decreased expression per cell rather than a decreased number of expressing cells. The declining expression of these genes was slowed during hypothyroidism and growth inhibition (induced by propylthiouracil at 0-5 wk of age) in male rats, suggesting that the normal decline in expression is driven by growth rather than by age per se. We conclude that there exists an extensive genetic program occurring during postnatal life. Many of the involved genes are regulated coordinately in multiple organs, including many genes that regulate cell proliferation. At least some of these are themselves apparently regulated by growth, suggesting that, in the embryo, a gene expression pattern is established that allows for rapid somatic growth of multiple tissues, but then, during postnatal life, this growth leads to negative-feedback changes in gene expression that in turn slow and eventually halt somatic growth, thus imposing a fundamental limit on adult body size.

The role of p27Kip1 in the regulation of growth plate chondrocyte proliferation in mice.

p27/Kip1, a cyclin-dependent kinase inhibitor, negatively regulates proliferation of multiple cell types. The goal of this study was to assess the role of p27 in the spatial, temporal, and conditional regulation of growth plate chondrocyte proliferation. p27 mRNA expression was detected by real-time RT-PCR in all zones of the mouse growth plate at levels approximately 2-fold lower than in the surrounding bone. To determine whether this expression is physiologically important, we studied skeletal growth in 7-wk-old mice lacking a functional p27 gene. In these mice, body length was modestly increased and proliferation of proximal tibial growth plate chondrocytes was increased, but tibia length was not significantly greater than in controls. p27 ablation had no measurable effect on growth plate morphology. Treatment with dexamethasone inhibited longitudinal bone growth similarly in p27-deficient mice and controls, indicating that p27 is not required for the inhibitory effects of glucocorticoids on longitudinal growth. p27-deficient mice had increased width of the femoral diaphysis, suggesting that p27 acts normally to inhibit periosteal bone growth. In conclusion, our findings suggest that p27 has modest inhibitory effects on growth plate chondrocyte proliferation but is not required for the spatial or temporal regulation of proliferation or the conditional regulation by glucocorticoid.

Endocrine regulation of the growth plate.

Longitudinal bone growth occurs at the growth plate by endochondral ossification. Within the growth plate, chondrocyte proliferation, hypertrophy, and cartilage matrix secretion result in chondrogenesis. The newly formed cartilage is invaded by blood vessels and bone cells that remodel the newly formed cartilage into bone tissue. This process of longitudinal bone growth is governed by a complex network of endocrine signals, including growth hormone, insulin-like growth factor I, glucocorticoid, thyroid hormone, estrogen, androgen, vitamin D, and leptin. Many of these signals regulate growth plate function, both by acting locally on growth plate chondrocytes and also indirectly by modulating other endocrine signals in the network. Some of the local effects of hormones are mediated by changes in paracrine factors that control chondrocyte proliferation and differentiation. Many human skeletal growth disorders are caused by abnormalities in the endocrine regulation of the growth plate. This review provides an overview of the endocrine signals that regulate longitudinal bone growth, their interactions, and the mechanisms by which they affect growth plate chondrogenesis.