Aberrant accumulation of misfolded proteins and insoluble aggregates within motor neurons (MNs) is a pathological hallmark of Amyotrophic Lateral Sclerosis (ALS), contributing to cellular stress and neurodegeneration. Autophagy, a tightly regulated lysosomal degradation pathway, plays a central role in maintaining neuronal proteostasis. Given the impairment of autophagy observed in ALS, its targeted activation via rationally engineered peptide therapeutics presents a promising disease-modifying strategy.
In this study, we designed and synthesised a series of Beclin-1–derived peptide analogues, incorporating backbone cyclisation to enhance structural stability, resistance to proteolytic degradation, and conformational constraint. These peptides were site-specifically conjugated to a proprietary blood-brain barrier (BBB)-penetrating cell-penetrating peptide (CPP), enabling efficient CNS delivery following systemic administration. Among these, CPP-BCN4 emerged as the lead candidate, exhibiting potent autophagy-inducing activity at low micromolar concentrations (5 µM) in MNs, surpassing the efficacy of known small-molecule autophagy modulators.
Mechanistic studies demonstrated that CPP-BCN4 significantly reduced intracellular aggregation of ALS-linked mutant SOD1 and C9ORF72-derived polyGR dipeptides, accompanied by suppression of caspase-3 activation. In autophagy reporter mice, intravenous administration of CPP-BCN4 (10 mg/kg) robustly enhanced autophagic flux and lysosomal biogenesis in spinal MNs. In the SOD1-G93A mouse model of ALS, repeated systemic dosing delayed disease onset, extended survival, and decreased circulating neurofilament light chain levels, a biomarker of axonal damage and neurodegeneration.
This work establishes a novel class of BBB-permeable, autophagy-inducing peptide conjugates as a viable therapeutic modality for ALS. Current efforts are focused on the application of artificial intelligence (AI)-driven peptide design and structure-based optimisation to develop next-generation analogues with enhanced affinity, selectivity, and metabolic stability. These advances are expected to facilitate broader translation into other neurodegenerative disorders, such as Alzheimer’s disease, where defective proteostasis and delivery across the BBB remain key therapeutic challenges.