PROJECT SUMMARY—In this Direct-to-Phase II SBIR application, Cogentis Therapeutics proposes to advance the development of CT526, a synthetic, cell-permeable peptide inhibitor of pathogenic CDK5-p25 as a treatment for neurodegeneration in amyotrophic lateral sclerosis (ALS). Cogentis has shown that CT526 normalizes the pathological activity of CDK5 in a mouse model of ALS while preserving essential CDK5 functionality, but additional work is needed to characterize its performance in phenotypically diverse mouse and clinically relevant human iPSC models. In addition, companion biomarkers are needed to track early responsiveness to CT526 in preclinical / clinical studies and to eventually support clinical decision-making, including drug titration. Given that the two FDA-approved drugs for ALS only provide modest benefit, further development and commercialization of CT526 and its companion biomarkers may substantially advance drug therapy for ALS, potentially providing the first treatment that slows, stops, or reverses neurodegeneration and its devastating effects on patient quality of life and survival. Aim 1. Demonstrate CT526 efficacy in a phenotypically diverse mouse model of ALS. Milestones: In the treatment group, 1) Demonstrate significant delay in disease onset, prolonged lifespan, and/or improved gait and kyphosis score progression; 2) Demonstrate normalization of CDK5 hyperactivity phenotype and p25 generation within 10% of the wildtype control level; 3) Demonstrate reduction of P-TDP43 and NF-L in cerebrospinal fluid; and 4) Demonstrate reduction of P-TDP43 and inflammatory markers in spinal cord. (P<0.05 for all differences.) Aim 2. Demonstrate the protective effect of CT526 in human iPSCs from patients with the most common molecular subtype of ALS. Milestones: 1) Validate CDK5 phenotype in iPSC cell lines by demonstrating ≥ 20% increase in CDK5 hyperactivity or ≥ 20% or more increase in p25/p35 ratio in ALS vs. healthy donor iPSCs; 2) Demonstrate dose-responsive protection of iPSCs in glutamate toxicity assays when treated with CT526. Aim 3. Characterize the response of neural-derived exosome (NDE)-based biomarkers to CT526. Milestones: 1) Demonstrate ≥ 20% increase in any of the CDK5 activity readouts in any subgroup of ALS postmortem brains compared to non-ALS age-matched controls. 2) Categorize ALS patient subtypes by CDK5 hyperactivity and degree of change in biomarkers. 3) Correlate biomarkers from postmortem brain and from NDE analysis with rho > 0.65, ≥ 20% difference between disease and control subgroups, and AUC ≥ 80%. 4) Detect ≥ 20% reduction in CDK5 hyperactivity-related NDE biomarkers in response to CT526 treatment of mouse/iPSC models in Aims 1 and 2. Impact—This project is expected to confirm CT526 efficacy in phenotypically diverse and clinically relevant models and identify an NDE-based biomarker(s) that can be used to track drug responsiveness in preclinical and clinical studies for an ALS therapeutic. In future work, Co...