Examining patient and professional perspectives in the UK for gene therapy in haemophilia

Introduction

With the development of gene therapy for people with haemophilia (PWH), it is important to understand how people impacted by haemophilia (PIH) and clinicians prioritise haemophilia treatment attributes to support informed treatment decisions.

Objective

To examine the treatment attribute preferences of PIH and clinical experts in the United Kingdom (UK) and to develop a profile of gene therapy characteristics fit for use in future discrete choice experiments (DCEs).

Methods

Semi‐structured interviews were conducted with PIH (n = 14) and clinical experts (n = 6) who ranked pre‐defined treatment attributes by importance. Framework analysis was conducted to identify key themes and treatment attributes; points were allocated based on the rankings. Synthesis of results by a multidisciplinary group informed development of a profile of gene therapy characteristics for use in future research.

Results

Key themes identified by PIH and clinical experts included patient relevant features and the importance of ‘informed decision making'. The six top‐ranked treatment attributes were ‘effect on factor level’ (79 points), ‘uncertainty regarding long‐term risks’ (57 points), ‘impact on daily life’ (41 points), ‘frequency of monitoring’ (33 points), ‘impact on ability to participate in physical activity’ (29 points), and ‘uncertainty regarding long‐term benefits’ (28 points). The final treatment characteristics were categorised as therapeutic option, treatment effectiveness, safety concerns, impact on self‐management and quality of life (role limitations).

Conclusion

We identified several gene therapy characteristics important to PIH and clinicians in the UK. These characteristics will be used in a future DCE to further investigate patient preferences for gene therapy.

White matter hyperintensities are seen only in GRN mutation carriers in the GENFI cohort

Genetic frontotemporal dementia is most commonly caused by mutations in the progranulin (GRN), microtubule-associated protein tau (MAPT) and chromosome 9 open reading frame 72 (C9orf72) genes. Previous small studies have reported the presence of cerebral white matter hyperintensities (WMH) in genetic FTD but this has not been systematically studied across the different mutations. In this study WMH were assessed in 180 participants from the Genetic FTD Initiative (GENFI) with 3D T1- and T2-weighed magnetic resonance images: 43 symptomatic (7 GRN, 13 MAPT and 23 C9orf72), 61 presymptomatic mutation carriers (25 GRN, 8 MAPT and 28 C9orf72) and 76 mutation negative non-carrier family members. An automatic detection and quantification algorithm was developed for determining load, location and appearance of WMH. Significant differences were seen only in the symptomatic GRN group compared with the other groups with no differences in the MAPT or C9orf72 groups: increased global load of WMH was seen, with WMH located in the frontal and occipital lobes more so than the parietal lobes, and nearer to the ventricles rather than juxtacortical. Although no differences were seen in the presymptomatic group as a whole, in the GRN cohort only there was an association of increased WMH volume with expected years from symptom onset. The appearance of the WMH was also different in the GRN group compared with the other groups, with the lesions in the GRN group being more similar to each other. The presence of WMH in those with progranulin deficiency may be related to the known role of progranulin in neuroinflammation, although other roles are also proposed including an effect on blood-brain barrier permeability and the cerebral vasculature. Future studies will be useful to investigate the longitudinal evolution of WMH and their potential use as a biomarker as well as post-mortem studies investigating the histopathological nature of the lesions.

•

In genetic FTD white matter hyperintensities (WMH) are found most prominently in symptomatic patients with GRN mutations.

•

Frontal and occipital lobes are the most affected regions.

•

WMH are more likely to occur close to the ventricles.

•

WMH have a more homogenous appearance possibly suggestive of inflammatory rather than vascular lesions.

Residual association at C9orf72 suggests an alternative amyotrophic lateral sclerosis-causing hexanucleotide repeat

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of motor neurons. Single-nucleotide polymorphism rs3849942 is associated with ALS, tagging a hexanucleotide repeat mutation in the C9orf72 gene. It is possible that there is more than 1 disease-causing genetic variation at this locus, in which case association might remain after removal of cases carrying the mutation. DNA from patients with ALS was therefore tested for the mutation. Genome-wide association testing was performed first using all samples, and then restricting the analysis to samples not carrying the mutation. rs3849942 and rs903603 were strongly associated with ALS when all samples were included (rs3849942, p = [3 × 2] × 10(-6), rank 7/442,057; rs903603, p = [7 × 6] × 10(-8), rank 2/442,057). Removal of the mutation-carrying cases resulted in loss of association for rs3849942 (p = [2 × 6] × 10(-3), rank 1225/442,068), but had little effect on rs903603 (p = [1 × 9] × 10(-5), rank 8/442,068). Those with a risk allele of rs903603 had an excess of apparent homozygosity for wild type repeat alleles, consistent with polymerase chain reaction failure of 1 allele because of massive repeat expansion. These results indicate residual association at the C9orf72 locus suggesting a second disease-causing repeat mutation.

Transcranial magnetic stimulation provides means to assess cortical plasticity and excitability in humans with fragile x syndrome and autism spectrum disorder

Fragile X Syndrome (FXS) is the most common heritable cause of intellectual disability. In vitro electrophysiologic data from mouse models of FXS suggest that loss of fragile X mental retardation protein affects intracortical excitability and synaptic plasticity. Specifically, the cortex appears hyperexcitable, and use-dependent long-term potentiation (LTP) and long-term depression (LTD) of synaptic strength are abnormal. Though animal models provide important information, FXS and other neurodevelopmental disorders are human diseases and as such translational research to evaluate cortical excitability and plasticity must be applied in the human. Transcranial magnetic stimulation paradigms have recently been developed to non-invasively investigate cortical excitability using paired pulse stimulation, as well as LTP- and LTD-like synaptic plasticity in response to theta burst stimulation (TBS) in vivo in the human. TBS applied on consecutive days can be used to measure metaplasticity (the ability of the synapse to undergo a second plastic change following a recent induction of plasticity). The current study investigated intracortical inhibition, plasticity and metaplasticity in full mutation females with FXS, participants with autism spectrum disorders (ASD), and neurotypical controls. Results suggest that intracortical inhibition is normal in participants with FXS, while plasticity and metaplasticity appear abnormal. ASD participants showed abnormalities in plasticity and metaplasticity, as well as heterogeneity in intracortical inhibition. Our findings highlight the utility of non-invasive neurophysiological measures to translate insights from animal models to humans with neurodevelopmental disorders, and thus provide direct confirmation of cortical dysfunction in patients with FXS and ASD.