A Scale to Assess Activities of Daily Living in Pantothenate Kinase-Associated Neurodegeneration

Study design challenges and strategies in clinical trials for rare diseases: Lessons learned from pantothenate kinase-associated neurodegeneration

Substantial challenges in study design and methodology exist during clinical trial development to examine treatment response in patients with a rare disease, especially those with predominant central nervous system involvement and heterogeneity in clinical manifestations and natural history. Here we discuss crucial decisions which may significantly impact success of the study, including patient selection and recruitment, identification and selection of endpoints, determination of the study duration, consideration of control groups including natural history controls, and selection of appropriate statistical analyses. We review strategies for the successful development of a clinical trial to evaluate treatment of a rare disease with a focus on inborn errors of metabolism (IEMs) that present with movement disorders. The strategies presented using pantothenate kinase-associated neurodegeneration (PKAN) as the rare disease example can be applied to other rare diseases, particularly IEMs with movement disorders (e.g., other neurodegeneration with brain iron accumulation disorders, lysosomal storage disorders). The significant challenges associated with designing a clinical trial in rare disease can sometimes be successfully met through strategic engagement with experts in the rare disease, seeking regulatory and biostatistical guidance, and early involvement of patients and families. In addition to these strategies, we discuss the urgent need for a paradigm shift within the regulatory processes to help accelerate medical product development and bring new innovations and advances to patients with rare neurodegenerative diseases who need them earlier in disease progression and prior to clinical manifestations.

Measuring health-related quality of life in patients with rare disease

Background

There has been a growing emphasis on health-related quality of life (HRQoL) as an important outcome in rare disease drug development, although its assessment may be useful outside the drug development context, including in clinical applications or natural history studies. Central to assessing quality of life in health research is utilizing outcome measures that capture symptoms and impacts of the disease and treatment that are important and relevant to patients. Identifying and implementing valid and reliable tools to measure HRQoL in rare diseases poses unique challenges that often require creative solutions.

Main body

In this commentary, we explore some of the challenges in HRQoL assessment in rare disease, propose solutions, and consider regulatory issues. Some of the solutions discussed entail the use of item banks, adapting existing measures from phenotypically similar disease contexts, use of multi-domain measurement indices, and adapting methods for assessing content validity of existing measures. Current regulatory considerations are discussed and resources outlined.

Conclusion

Quality of life may be the most important endpoint for patients with rare diseases, and the challenges of valid assessment require effort and innovative thinking specific to each context to improve measurement and clinical outcomes.

Fosmetpantotenate Randomized Controlled Trial in Pantothenate Kinase-Associated Neurodegeneration

BACKGROUND

Pantothenate kinase-associated neurodegeneration (PKAN) currently has no approved treatments.

OBJECTIVES

The Fosmetpantotenate Replacement Therapy pivotal trial examined whether treatment with fosmetpantotenate improves PKAN symptoms and stabilizes disease progression.

METHODS

This randomized, double-blind, placebo-controlled, multicenter study evaluated fosmetpantotenate, 300 mg oral dose three times daily, versus placebo over a 24-week double-blind period. Patients with pathogenic variants of PANK2, aged 6 to 65 years, with a score ≥6 on the PKAN-Activities of Daily Living (PKAN-ADL) scale were enrolled. Patients were randomized to active (fosmetpantotenate) or placebo treatment, stratified by weight and age. The primary efficacy endpoint was change from baseline at week 24 in PKAN-ADL.

RESULTS

Between July 23, 2017, and December 18, 2018, 84 patients were randomized (fosmetpantotenate: n = 41; placebo: n = 43); all 84 patients were included in the analyses. Six patients in the placebo group discontinued treatment; two had worsening dystonia, two had poor compliance, and two died of PKAN-related complications (aspiration during feeding and disease progression with respiratory failure, respectively). Fosmetpantotenate and placebo group PKAN-ADL mean (standard deviation) scores were 28.2 (11.4) and 27.4 (11.5) at baseline, respectively, and were 26.9 (12.5) and 24.5 (11.8) at week 24, respectively. The difference in least square mean (95% confidence interval) at week 24 between fosmetpantotenate and placebo was -0.09 (-1.69 to 1.51; P = 0.9115). The overall incidence of treatment-emergent serious adverse events was similar in the fosmetpantotenate (8/41; 19.5%) and placebo (6/43; 14.0%) groups.

CONCLUSIONS

Treatment with fosmetpantotenate was safe but did not improve function assessed by the PKAN-ADL in patients with PKAN. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Rational Design of Novel Therapies for Pantothenate Kinase-Associated Neurodegeneration

BACKGROUND

This review highlights the recent scientific advances that have enabled rational design of novel clinical trials for pantothenate kinase-associated neurodegeneration (PKAN), a rare autosomal recessive neurogenetic disorder associated with progressive neurodegenerative changes and functional impairment. PKAN is caused by genetic variants in the PANK2 gene that result in dysfunction in pantothenate kinase 2 (PANK2) enzyme activity, with consequent disruption of coenzyme A (CoA) synthesis, and subsequent accumulation of brain iron. The clinical phenotype is varied and may include dystonia, rigidity, bradykinesia, postural instability, spasticity, loss of ambulation and ability to communicate, feeding difficulties, psychiatric issues, and cognitive and visual impairment. There are several symptom-targeted treatments, but these do not provide sustained benefit as the disorder progresses.

OBJECTIVES

A detailed understanding of the molecular and biochemical pathogenesis of PKAN has opened the door for the design of novel rationally designed therapeutics that target the underlying mechanisms.

METHODS

Two large double-blind phase 3 clinical trials have been completed for deferiprone (an iron chelation treatment) and fosmetpantotenate (precursor replacement therapy). A pilot open-label trial of pantethine as a potential precursor replacement strategy has also been completed, and a trial of 4-phosphopantetheine has begun enrollment. Several other compounds have been evaluated in pre-clinical studies, and additional clinical trials may be anticipated.

CONCLUSIONS

Experience with these trials has encouraged a critical evaluation of optimal trial designs, as well as the development of PKAN-specific measures to monitor outcomes. PKAN provides a valuable example for understanding targeted drug development and clinical trial design for rare disorders. © 2021 International Parkinson and Movement Disorder Society.

Treat Iron-Related Childhood-Onset Neurodegeneration (TIRCON)-An International Network on Care and Research for Patients With Neurodegeneration With Brain Iron Accumulation (NBIA)

In order to improve clinical care, coordinate research activities and raise awareness for the ultra-orphan Neurodegeneration with Brain Iron Accumulation (NBIA) disorders, a group of NBIA clinicians and researchers, industry partners and patient advocacies from six European countries, Canada and the US joined forces in 2010 to set-up the collaborative initiative TIRCON (Treat Iron-Related Childhood-Onset Neurodegeneration). As a research project, TIRCON received funding in the 7th Framework Programme (FP7) of the European Union (EU) from 2011 to 2015. After successful and timely completion of the initial FP7 project, funding and donations from industry and patient organizations have sustained the further development of TIRCON's dedicated clinical research infrastructure and its governance architecture, as well as the ongoing efforts undertaken in the NBIA community to establish a network of care. From the beginning, the University Hospital of the Ludwig-Maximilians-University in Munich, Germany has been coordinating the TIRCON initiative. It consists of 8 work packages, of which the first double-blind, placebo-controlled, randomized, multi-site clinical trial in NBIA (deferiprone in PKAN, completed) and a global patient registry and biobank, currently comprising baseline and follow-up data of > 400 NBIA patients have gained particular importance. Here we describe TIRCON's history with all the challenges and achievements in diagnosing and treating NBIA. Today, TIRCON lays the ground for future clinical care and research. In these times, it may also serve as a good example of well-directed governmental funding and fruitful international scientific collaboration.

Thalamic deep brain stimulation for acquired dystonia in children and young adults: a phase 1 clinical trial

OBJECTIVE

The aim of this study was to evaluate the feasibility and preliminary efficacy and safety of combined bilateral ventralis oralis posterior/ventralis intermedius (Vop/Vim) deep brain stimulation (DBS) for the treatment of acquired dystonia in children and young adults. Pallidal DBS is efficacious for severe, medication-refractory isolated dystonia, providing 50%-60% long-term improvement. Unfortunately, pallidal stimulation response rates in acquired dystonia are modest and unpredictable, with frequent nonresponders. Acquired dystonia, most commonly caused by cerebral palsy, is more common than isolated dystonia in pediatric populations and is more recalcitrant to standard treatments. Given the limitations of pallidal DBS in acquired dystonia, there is a need to explore alternative brain targets. Preliminary evidence has suggested that thalamic stimulation may be efficacious for acquired dystonia.

METHODS

Four participants, 3 with perinatal brain injuries and 1 with postencephalitic symptomatic dystonia, underwent bilateral Vop/Vim DBS and bimonthly evaluations for 12 months. The primary efficacy outcome was the change in Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and Barry-Albright Dystonia Scale (BADS) scores between the baseline and 12-month assessments. Video documentation was used for blinded ratings. Secondary outcomes included evaluation of spasticity (Modified Ashworth Scale score), quality of life (Pediatric Quality of Life Inventory [PedsQL] and modified Unified Parkinson's Disease Rating Scale Part II [UPDRS-II] scores), and neuropsychological assessments. Adverse events were monitored for safety.

RESULTS

All participants tolerated the procedure well, and there were no safety concerns or serious adverse events. There was an average improvement of 21.5% in the BFMDRS motor subscale score, but the improvement was only 1.6% according to the BADS score. Following blinded video review, dystonia severity ratings were even more modest. Secondary outcomes, however, were more encouraging, with the BFMDRS disability subscale score improving by 15.7%, the PedsQL total score by 27%, and the modified UPDRS-II score by 19.3%. Neuropsychological assessment findings were unchanged 1 year after surgery.

CONCLUSIONS

Bilateral thalamic neuromodulation by DBS for severe, medication-refractory acquired dystonia was well tolerated. Primary and secondary outcomes showed highly variable treatment effect sizes comparable to those of pallidal stimulation in this population. As previously described, improvements in quality of life and disability were not reflected in dystonia severity scales, suggesting a need for the development of scales specifically for acquired dystonia.Clinical trial registration no.: NCT03078816 (clinicaltrials.gov).

The FOsmetpantotenate Replacement Therapy (FORT) randomized, double-blind, Placebo-controlled pivotal trial: Study design and development methodology of a novel primary efficacy outcome in patients with pantothenate kinase-associated neurodegeneration

BACKGROUND/AIMS

Pantothenate kinase-associated neurodegeneration is a rare neurodegenerative disease with a variable clinical phenotype. Fosmetpantotenate is in clinical development as a replacement therapy that targets the underlying cause of pantothenate kinase-associated neurodegeneration. The FOsmetpantotenate Replacement Therapy pivotal trial-an ongoing phase 3, randomized, double-blind, placebo-controlled, multicenter trial-examines the efficacy and safety of fosmetpantotenate in patients with pantothenate kinase-associated neurodegeneration aged 6-65 years. The FOsmetpantotenate Replacement Therapy trial required the development and validation of a novel patient-reported outcome measure specifically relevant to pantothenate kinase-associated neurodegeneration. The Pantothenate Kinase-Associated Neurodegeneration-Activities of Daily Living scale was developed to assess activities of daily living related to motor functioning in patients with pantothenate kinase-associated neurodegeneration to evaluate clinically meaningful change as the primary efficacy endpoint in clinical trials. This article describes the design of the FOsmetpantotenate Replacement Therapy pivotal trial and the development of the Pantothenate Kinase-Associated Neurodegeneration-Activities of Daily Living scale.

METHODS

A systematic, iterative process consistent with the US Food and Drug Administration guidance and advice from the Committee for Medicinal Products for Human Use at the European Medicines Agency was used to evaluate and adapt or remove scale items of an existing widely used instrument for movement disorders to be pantothenate kinase-associated neurodegeneration-specific, and to create new items. Modification of scale items was based on input from international experts, patient advocacy leaders, and primary caregivers. A clinimetric study of the Pantothenate Kinase-Associated Neurodegeneration-Activities of Daily Living scale conducted in patients with pantothenate kinase-associated neurodegeneration or their caregivers (N = 40 at first assessment; N = 39 at second assessment) demonstrated high content and construct validity and excellent test-retest reliability over an approximately 2-week period. The Pantothenate Kinase-Associated Neurodegeneration-Activities of Daily Living scale was developed to be broadly useful within clinical and research settings in the examination of patient response to pantothenate kinase-associated neurodegeneration therapies.

RESULTS

Approximately 82 patients will be enrolled in the ongoing FOsmetpantotenate Replacement Therapy pivotal trial. Change from baseline in Pantothenate Kinase-Associated Neurodegeneration-Activities of Daily Living score over the 24-week double-blind period is the primary efficacy endpoint for the FOsmetpantotenate Replacement Therapy trial. Treatment effect will be evaluated using a mixed model for repeated measures analysis to assess data from all visits simultaneously.

CONCLUSION

The development and implementation of the Pantothenate Kinase-Associated Neurodegeneration-Activities of Daily Living scale in the FOsmetpantotenate Replacement Therapy trial illustrates the feasibility and potential patient benefit of putting into practice the current regulatory guidance on the use of patient-reported outcomes in clinical trials. These processes can be broadly applied to clinical trial methodology that requires newly created or revised patient-reported outcome measures to evaluate outcome change as a primary efficacy endpoint. The goal of such measures in patients with pantothenate kinase-associated neurodegeneration is to facilitate development of disease-modifying therapeutics in multiple drug development programs.

Diagnostic and clinical experience of patients with pantothenate kinase-associated neurodegeneration

BACKGROUND

Pantothenate kinase-associated neurodegeneration (PKAN) is an autosomal recessive neurodegenerative disorder with brain iron accumulation (NBIA).

OBJECTIVES

To assess PKAN diagnostic pathway, history, and burden across the spectrum of PKAN severity from patient and/or caregiver perspectives.

METHODS

Caregivers of patients (n = 37) and patients themselves (n = 2) were interviewed in a validation study of the PKAN-Activities of Daily Living (ADL) scale. The current study used quartiles of the PKAN-ADL total score to divide patients by severity of impairment (Lowest, Second Lowest, Third Lowest, Highest). Diagnostic and treatment history, healthcare utilization, disease burden, and caregiver experience were compared between groups.

RESULTS

The analyses included data from 39 patients. Mean age at PKAN symptom onset (P = 0.0007), initial MRI (P = 0.0150), and genetic testing (P = 0.0016) generally decreased across the PKAN severity spectrum. The mean duration of illness did not differ among PKAN severity groups (range, 9.7-15.2 years; P = 0.3029). First MRI led to diagnosis in 56.4% of patients (range, 30.0-90.0%). A mean (SD) of 13.0 (13.1) medical and 55.2 (78.5) therapy visits (eg, physical, speech) occurred in the past year. More patients in the higher PKAN severity groups experienced multiple current functional losses and/or earlier onset of problems (P-values < 0.0500). Over half (56.8%) of caregivers experienced a change in employment because of caregiving. The percentage of patients requiring full-time caregiving increased across the PKAN severity spectrum (range, 11.1-100%; P = 0.0021).

CONCLUSIONS

PKAN diagnosis was often delayed, most probably due to low awareness. Considerable burden of functional impairment and high healthcare utilization were found across the PKAN severity spectrum.