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Twenty questions about multiple sclerosis clinical trials methodologies
1Memorial University of Newfoundland, Health Sciences Centre, St. John's, Canada.
Abstract:
The heterogeneity of methods used in multiple sclerosis (MS) clinical trials prevents fair comparison of trials and reduces confidence in the validity of the therapeutic claims made. The validity of recent clinical trials is lessened by the following factors: MS shows variability in type and in rates of disease progression; primary progressive MS may not be the same disease as typical MS, and inclusion of subjects with this condition may have skewed results of trials to date. Using a new model, "relapsing-remitting" and "secondary progressive" MS are considered to represent earlier and later stages of the same disease. The variety of endpoints used in clinical trials impairs comparisons. The differences between EDSS stages vary at different levels and it is concluded that this is no longer the most appropriate tool, although it could be improved by modifying the scoring or scales to assess certain focused items. The clinical significance of a reduction in relapse rate is questioned, as are the inclusion criteria employed in recent trials. Drug doses based upon body mass differ from those based on surface area, making it hard to compare the effects of trial agents. The definitions of "sustained worsening" are not uniform and the concept is complicated by regression to the mean. Trials should continue for long enough to be sure that any beneficial effects noted are permanent. Although extensions provide better long-term data, they are usually statistically underpowered and clinically and demographically imbalanced. Ethically, if benefit is determined to be present, a trial should be stopped so that all subjects may be offered the beneficial agent, but determination of benefit may be imperfect. The "intention to treat" paradigm is a shibboleth, providing data on effectiveness rather than efficacy. The simple listing and addition of unwanted effects (UEs) is unproductive. Trivial UEs detract little from quality of life and are unimportant. The remainder should be separated between the notable and the serious, judging the net benefit of the agent causing them accordingly. Conventional MRI measures the density of hydrogen protons and thus is a map of water, which implies edema and thus the presence of a local inflammatory response, but conventional images do not inform on de- or re-myelination, axonal loss or gliosis and correlate poorly with clinical scores. It is concluded that recent MS therapeutic trials are subject to important criticism.
Insights
Multiple sclerosis (MS) clinical trials face significant challenges in comparing results due to varied methods, endpoints, and outcome measures. These inconsistencies undermine confidence in therapeutic claims and highlight the need for methodological improvements in MS research.
Area of Science:
- Neurology
- Clinical Trials Methodology
- Multiple Sclerosis Research
Background:
- Heterogeneity in multiple sclerosis (MS) trial methodologies hinders comparative analysis and reduces confidence in therapeutic claims.
- Variability in MS disease types, progression rates, and the inclusion of primary progressive MS complicate trial validity.
- Current trial designs often lack standardization in endpoints, disease staging assessments, and definitions of treatment effects.
Purpose of the Study:
- To critically evaluate the methodological limitations of recent multiple sclerosis (MS) clinical trials.
- To identify factors contributing to the reduced validity and comparability of MS therapeutic trials.
- To propose areas for improvement in the design and execution of future MS clinical trials.
Main Methods:
- Analysis of methodological heterogeneity in MS clinical trials, including variations in disease classification, endpoints, and outcome measures.
- Critique of the Expanded Disability Status Scale (EDSS) and proposed modifications for improved utility.
- Examination of inclusion/exclusion criteria, dosing strategies, definitions of sustained worsening, and trial duration.
- Evaluation of statistical paradigms like "intention to treat" and methods for assessing adverse events.
- Assessment of the limitations of conventional Magnetic Resonance Imaging (MRI) in reflecting disease pathology and clinical outcomes.
Main Results:
- Inconsistent methodologies, diverse endpoints (e.g., relapse rate, EDSS), and varied definitions of "sustained worsening" impair trial comparability.
- The clinical significance of reduced relapse rates and the utility of current inclusion criteria are questioned.
- Differences in drug dosing (body mass vs. surface area) and the statistical underpowering of trial extensions complicate interpretation.
- Conventional MRI lacks sensitivity to key pathological changes like de/re-myelination and axonal loss, correlating poorly with clinical scores.
- The "intention to treat" approach may reflect effectiveness rather than true efficacy, and the reporting of adverse events needs refinement.
Conclusions:
- Recent multiple sclerosis (MS) therapeutic trials are subject to significant methodological criticisms.
- Improvements in trial design, endpoint selection, outcome assessment, and MRI utilization are crucial for advancing MS therapeutics.
- Standardization and refinement of methodologies are essential to increase the validity and comparability of MS clinical trial data.