Identification and Utilization of Upper Motor Neuron Biomarkers for ALS

Background: ALS is both rare and heterogeneous. It involves both the cortical and the spinal component of the motor neuron circuitry. Previously, due to technical challenges, the cortical component of ALS has been somewhat neglected. For example, upper motor neurons (UMNs) are harder to derive from iPSC and UMN clinical signs are more difficult to detect. However, biomarkers of cortical health is required to stratify patients based on the origins of disease and provide an index of the stage and progression of UMN degeneration. Even though peripheral benzodiazepine receptor positron emission tomography (PBR-PET) imaging correlate with UMN dysfunction, currently, there are no biomarkers that allow quantitative and reliable measures to assess the extent of UMN loss in ALS patients. Consequently, clinicians rely solely on reflex examination to establish a diagnosis of ALS. Furthermore, UMN dysfunction may correlate with stages of ALS that would be more or less amenable to a given therapeutic. And, the health and stability of UMNs in ALS could be a trial outcome measure if it were quantitative. The development of quantitative biomarkers of UMN dysfunction could assist with ALS diagnosis, help target novel therapies to an appropriate stage of disease, and act as ALS trial outcome measures, with enough validation. The first step in that pathway is identification of such biomarkers. Objective/Hypothesis: Our objective is to enable the development and deployment of long-term, effective treatment strategies for ALS by integrating UMN status into patient assessment, clinical trial design, and drug discovery. Specific Aims: Specific Aim 1: Determine the protein profile of serum and plasma samples isolated from ALS patients with prominent UMN loss and ALS patients with minimal UMN loss, based on clinical findings, as well as age and sex-matched healthy controls. Determine whether identified “key proteins” are specific to ALS patients with prominent UMN loss, or also observed in HSP and PLS patients. Specific Aim 2: Determine whether serum/plasma protein profiles can be used to reliably and accurately assess disease progression and response to treatment. We will quantitate changes in of key serum proteins and their isoforms over time in alignment with clinical markers of UMN involvement and in response to disease progression and/or therapeutic intervention. Study Design: This proposal is focused on the identification of novel proteins and their proteoforms that can be used as a prognostic and/or pharmacokinetic biomarkers to detect ALS patients with prominent UMN loss and to assess the extent of UMN damage in patients. MGH will provide serum and plasma samples (Table 1) Samples will be blinded and subjected to quantitative bottom up proteomics. Our preliminary studies have previously identified a select set of proteins in ALS patients with prominent UMN loss (Ozdinler Lab, unpublished results, patent applied), the distribution of proteoforms of these proteins will be investigated at different time points of disease progression, by top-down proteomics in comparison to age- and sex matched healthy controls. Results will be analyzed with rigorous statistical measures. Impact: To date, only PBR-PET tracers can identify UMN involvement in ALS. However, PBR-PET only correlates with reflex examination at this point, adding no new information about UMN degeneration and does not progress over the symptomatic course of ALS. This is a limiting factor for clinical trial design and outcome measures. Especially for patients who have prom