Amyotrophic Lateral Sclerosis (ALS) is a relentlessly progressive neurodegenerative condition with considerable clinical, pathological and genetic heterogeneity. Despite tireless research efforts, no effective disease modifying therapies currently exist. In the past couple of years, an array of promising therapeutic targets, pathophysiological pathways, mechanisms of propagation have been identified giving unprecedented impetus to research initiatives worldwide. Two of the main barriers to effective drug development in ALS are the clinical heterogeneity of the condition and the lack of validated biomarkers.

The dual relevance of biomarker development in ALS lies in the characterisation of dynamic pathological process and its application to individualised patient care. From an academic perspective, biomarkers have the potential to elucidate the role of specific pathobiological processes, such as inflammation, cortical hyperexcitability, inhibitory dysfunction, cell to cell propagation and anatomical patterns of vulnerability. From a clinical standpoint, validated biomarkers have the potential to confirm an earlier diagnosis, thus enabling recruitment into clinical trials at an earlier stage. The key advantage of ALS-specific biomarkers however is their potential monitoring role in clinical trials, which currently overwhelmingly rely on functional rating scales and survival. Additionally, biomarkers may act as prognostic indicators which are indispensable both for clinical trial designs and for individualised patient care.

The academic and clinical importance of biomarker development in ALS is universally recognised by ALS consortia and is regarded as a strategic funding priority by ALS charities and funding agencies around the world. MNDA, ALSA, ARSLA, NISALS, NEALS, CALSNIC, RMN, JPND re just some of the many organisations actively engaging in the development of multicentre data repositories, and establishing biobanking infrastructures for ALS. Due to disease heterogeneity and the differing sensitivity profiles of single markers, it is generally accepted that a panel of biomarkers will most likely to aid clinical care and serve as monitoring markers in clinical trials.

The main themes of ALS biomarker research include “dry biomarkers” which centre on clinical, electrophysiological and neuroimaging measures, and “wet biomarkers” which focus on disease-specific biofluid profiles. Hypothesis-driven, targeted and high-throughput methods are both widely used in the so-called “omics” approaches: metabolomics, proteomics, lipidomics, and transcriptomics. One of the alluring aspects of international collaborations is that ALS centres around the world have unique local expertise profiles which complement synergistically the skillset of other centres. Therefore single ALS centres are in a position to provide authoritative reviews on specific aspects of biomarker development efforts. Accordingly, the co-editors of this Research Topic are particularly proud to already have commitments from a number of ALS research groups to contribute papers on their own field of expertise including centres in Athens, Paris, Cleveland, Milan, Norwich, Boston, Washington, Edmonton, Sidney, Brisbane, Ulm, Oxford, Jena, Regensburg, Nottingham, Dublin, Leuven, Utrecht, Toronto, Strasbourg etc. showcasing the geographical spectrum of ALS research initiatives worldwide. The overall objective of this Research Topic is to highlight research efforts around the globe to develop viable biomarkers in ALS paving the way for effective disease-modifying therapies.

Keywords: Amyotrophic Lateral Sclerosis, Neurodegeneration, Biomarkers

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