What are ALS biomarkers, and what significance do they have for research?
Biomarkers are molecules that can be detected in blood serum,cerebrospinal fluid (CSF ), urine, or other tissues. In a broader sense, imaging data (MRI data) or movement patterns (recorded by sensors) can also be considered biomarkers. Biomarkers are biological “signals” that are closely correlated with the progression of ALS.
A biomarker for ALS is expected to offer three advantages: 1) confirming the diagnosis by distinguishing ALS from other diseases that share similarities with it (aiding in diagnosis), 2) indicating the progression of the disease, and 3) assessing the response to effective treatment.
The primary purpose of the biomarker is to assist in cases where diagnosing ALS using conventional clinical criteria and diagnostic tests is difficult. In such cases, the biomarker can help distinguish between ALS and other conditions in the differential diagnosis.
The second and third objectives (correlation of the biomarker with disease progression and response to therapy) are of crucial importance for clinical research. These properties of a biomarker allow clinical trials to be completed more quickly and conducted more efficiently. Ideally, a biomarker (e.g., in the blood) would indicate shortly after the start of therapy whether the drug is leading to a reduction in nerve cell death. This therapeutic effect could be detectable in the blood earlier than it is detectable in clinical examinations (which are conducted at intervals of several months).
Since 2017, the biomarker neurofilament light chain (NfL) has been established as an indicator of nerve cell death in blood serum and cerebrospinal fluid. The biomarker is not specific to ALS, but it is helpful in distinguishing between ALS and other motor disorders. Intensive research since 2020 has demonstrated the importance of NfL in determining disease progression. Furthermore, NfL serves as a biomarker for assessing the therapeutic efficacy of new ALS drugs that are still under investigation.