Outcome Measures and Biomarkers for Clinical Trials in Hereditary Spastic Paraplegia: A Scoping Review

Preclinical alternative drug discovery programs for monogenic rare diseases. Should small molecules or gene therapy be used? The case of hereditary spastic paraplegias

Patients diagnosed with rare diseases and their and families search desperately to organize drug discovery campaigns. Alternative models that differ from default paradigms offer real opportunities. There are, however, no clear guidelines for the development of such models, which reduces success rates and raises costs. We address the main challenges in making the discovery of new preclinical treatments more accessible, using rare hereditary paraplegia as a paradigmatic case. First, we discuss the necessary expertise, and the patients' clinical and genetic data. Then, we revisit gene therapy, de novo drug development, and drug repurposing, discussing their applicability. Moreover, we explore a pool of recommended in silico tools for pathogenic variant and protein structure prediction, virtual screening, and experimental validation methods, discussing their strengths and weaknesses. Finally, we focus on successful case applications.

Metabolite profile in hereditary spastic paraplegia analyzed using magnetic resonance spectroscopy: a cross-sectional analysis in a longitudinal study

Background

Hereditary Spastic Paraplegias (HSP) are genetic neurodegenerative disorders affecting the corticospinal tract. No established neuroimaging biomarker is associated with this condition.

Methods

A total of 46 patients affected by HSP, genetically and clinically evaluated and tested with SPRS scores, and 46 healthy controls (HC) matched by age and gender underwent a single-voxel Magnetic Resonance Spectroscopy sampling (MRS) of bilateral pre-central and pre-frontal regions. MRS data were analyzed cross-sectionally (at T0 and T1) and longitudinally (T0 vs. T1).

Results

Statistically significant data showed that T0 mI/Cr in the pre-central areas of HSP patients was higher than in HC. In the left (L) pre-central area, NAA/Cr was significantly lower in HSP than in HC. In the right (R) pre-frontal area, NAA/Cr was significantly lower in HSP patients than in HC. HSP SPG4 subjects had significantly lower Cho/Cr concentrations in the L pre-central area compared to HC. Among the HSP subjects, non-SPG4 patients had significantly higher mI/Cr in the L pre-central area compared to SPG4 patients. In the R pre-frontal area, NAA/Cr was reduced, and ml/Cr was higher in non-SPG4 patients compared to SPG4 patients. Comparing "pure" and "complex" forms, NAA/Cr was higher in pHSP than in cHSP in the R pre-central and R pre-frontal areas. The longitudinal analysis, which involved fewer patients (n = 30), showed an increase in mI/Cr concentration in the L pre-frontal area among HSP subjects with respect to baseline. The patients had significantly higher SPRS scores at follow-up, with a significant positive correlation between SPRS scores and mI/Cr in the L pre-central area, while in bilateral pre-frontal areas, lower SPRS scores corresponded to higher NAA/Cr concentrations. To explore the discriminating power of MRS in correctly identifying HSP and controls, an inference tree methodology classified HSP subjects and controls with an overall accuracy of 73.9%, a sensitivity of 87.0%, and a specificity of 60.9%.

Conclusion

This pilot study indicates that brain MRS is a valuable approach that could potentially serve as an objective biomarker in HSP.

Study on Genotypes and Phenotypes of Neurodegenerative Diseases

Neurodegenerative diseases are a heterogeneous group of age-related disorders that are characterised by the gradual degeneration or death of neurons in the central or peripheral nervous system [...].

Development and validation of TreatHSP-QoL: a patient-reported outcome measure for health-related quality of life in hereditary spastic paraplegia

BACKGROUND

Hereditary spastic paraplegia (HSP) is a rare neurodegenerative disease that lacks specific and validated patient-centered outcome measures (PCOMs). We aimed to develop and validate a health-related quality of life (HRQoL) questionnaire specific to HSP ("TreatHSP-QoL") that could be used as a PCOM.

RESULTS

The pilot-items of the TreatHSP-QoL (45 five-level Likert scale items, with values per item between 0 and 4) were developed based on a qualitative data analysis of 54 semi-structured interviews, conducted in person with 36 HSP patients and 18 caregivers. It was then reduced and modified through the validation process to 25 items. The main validation was performed using the online questionnaire in 242 HSP patients and 56 caregivers. The exploratory factor analysis defined five subdomains. Cronbach's alpha ranged from 0.57 to 0.85 for the subdomains and reached 0.85 for the total score. The test-retest Pearson correlation reached 0.86 (95% Confidence Interval (CI) [0.79, 0.91]). Pearson correlations with the EuroQol-5 Dimension (5 levels) (EQ-5D-5L) and Friedreich Ataxia Rating Scale-Activities of Daily Living (FARS-ADL) questionnaires varied strongly among the subdomains, with the total scores reaching 0.53 (95% CI [0.42, 0.61]) and -0.45 (95% CI [- 0.55, - 0.35]), respectively. The caregiver-patient response Pearson correlation ranged between 0.64 and 0.82 for subdomains and reached 0.65 (95% CI [0.38, 0.81]) for the total score.

CONCLUSIONS

TreatHSP-QoL can be used in high-quality clinical trials and clinical practice as a disease-specific PCOM (i.e., HRQoL measure) and is also applicable as a proxy questionnaire. Score values between 0 and 100 can be reached, where higher value represents better HRQoL. The Pearson correlations to the EQ-5D-5L and FARS-ADL support the additional value and need of HSP-specific PCOM, while non-specific QoL-assessment and specific clinical self-assessment tools already exist. All in all, the results demonstrate good validity and reliability for this new patient-centered questionnaire for HSP.