CRM-200: Rational Design of a Brain-Penetrant D-Retro-Inverso Peptide-siRNA Conjugate for Non-Cytolytic Clearance of Intracellular Rabies Virus

Rabies virus (RABV) establishes an invariably fatal encephalomyelitis characterized by immune evasion and active suppression of neuro-inflammatory host defenses within the central nervous system (CNS). While competitive entry inhibitors (such as CRM-101) arrest intercellular spread, post-symptomatic cure fundamentally requires the active elimination of intracellular replication complexes without inducing host neuronal lysis. Here, we introduce CRM-200, a next-generation brain-penetrant peptide-RNA interference bioconjugate engineered for targeted, non-cytolytic viral eradication.

CRM-200 covalently links a protease-resistant D-Retro-Inverso RVG29 transcytosis shuttle (GNSARKGRSNTFIDCPTGPRPNEP[Nle]WITY-NH2) via a self-immolative, glutathione-cleavable hexyl-disulfide linker to a chemically stabilized 21-nucleotide siRNA duplex targeting an ultra-conserved domain of the RABV nucleoprotein (N-gene, nt 340-360). Nearest-neighbor thermodynamic modeling reveals optimal duplex stability (Delta G at 37 C = -33.17 kcal/mol, Tm = 82.66 degrees C, GC content: 47.37%) paired with strict terminal thermodynamic asymmetry (0% GC at antisense 5'-end vs 50% at 3'-end), ensuring selective loading of the guide strand into the Argonaute-2 (Ago2)/RISC complex while avoiding off-target passenger activity. Following alpha7-nAChR-mediated transcytosis across the Blood-Brain Barrier (BBB) and endosomal escape into the neuronal soma, intracellular glutathione (2-10 mM) selectively reduces the disulfide bridge, releasing native siRNA into the cytoplasm (half-life < 30 min) to catalyze sequence-specific catalytic cleavage of the uncapped viral N-mRNA and antigenomic replication intermediates. Furthermore, co-administration with the Antigenic Site III macrocyclic entry inhibitor CRM-101 establishes a synergistic Dual-Lock protocol, concurrently arresting extracellular trans-synaptic spread while catalytically degrading intra-neuronal replication machinery. CRM-200 provides the first modular blueprint for active, non-destructive viral elimination in established rabies encephalomyelitis.

• Project Lead & Conception: Radu-Mihai Clinciu (Independent Project Originator, Romania; Contact: radumihaiclinciu@yahoo.com).
• Computational Workflow: Designed and validated using an automated biocomputing toolchain (Nearest-neighbor RNA thermodynamics, structural modeling, Typst). All raw scripts, 3D coordinate PDB models, and reproducibility protocols are provided in the accompanying open-access research package.