Background

Destruction of Motor Neurons and Genetic Causes

Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig's disease, is a fatal neurodegenerative disease characterized by the selective death of motor neurons, leading to paralysis. In some patients, mutations in the superoxide dismutase 1 (SOD1) gene are identified as a genetic cause. The mutated SOD1 protein accumulates in cells, causing neurotoxicity.

Emergence of Gene Silencing Therapy and Existing Technical Challenges

To address this, tofersen, an antisense oligonucleotide (ASO)-based therapeutic, has been developed and marketed. However, the frequent administration schedule was burdensome for patients. The relatively short duration of drug efficacy required repeated high-dose intrathecal injections. Small interfering RNA (siRNA), which has a stronger gene silencing effect, has been hindered by its high hydrophilicity and the blood-brain barrier, preventing its delivery to the cerebrospinal fluid.

Key Findings

SCAD Platform and the Development of the Novel Candidate Drug RAG-17

The research team at Ractigen Therapeutics in China published the first Phase 1 clinical trial results of 'RAG-17', a therapeutic candidate that enhances the drug delivery of siRNA, in the international journal 'Nature Medicine' on July 15. This compound is based on the 'Smart Chemistry-Aided Delivery (SCAD)' platform technology, which combines siRNA with a short accessory oligonucleotide (ACO) that induces protein binding in vivo.

Efficacy Demonstrated in Animal Models and Phase 1 Human Clinical Trials

The delivery performance was demonstrated in animal experiments. In non-human primates, a single intrathecal administration of RAG-17 resulted in uniform distribution of the drug throughout the brain and spinal cord, with a maximum reduction in the expression of the target SOD1 mRNA of up to 91% after 72 days. The results were also observed in a late-stage mouse model of the disease. In a severe ALS mouse model (SOD1G93A), the survival time was extended by up to 75.8% compared to the control group. The initial human clinical results were also positive. In a Phase 1 clinical trial involving six patients, no serious adverse events related to the drug were observed. The levels of SOD1 protein in the cerebrospinal fluid (CSF) of the patients decreased by an average of up to 69%, and the concentration of neurofilament light chain (NfL), a biomarker of neuronal damage, also decreased by up to 81%, demonstrating a significant therapeutic effect.

Significance and Prospects

Improved Long-Term Efficacy and Convenience

The results of RAG-17 provide a promising approach to significantly improve the quality of life for ALS patients by providing sustained therapeutic effects. The reduced frequency of administration will alleviate the physical and psychological burden on patients associated with frequent invasive intrathecal procedures. The scalability is also promising. The SCAD delivery platform can be widely expanded to deliver therapeutic agents for other rare central nervous system diseases, such as Parkinson's disease and Huntington's disease, by simply replacing the target sequence.

Remaining Challenges and Future Clinical Plans

There are also challenges to be addressed. This trial was a small Phase 1 clinical trial involving only six patients, and it explored only the safety and early changes in biomarkers. Therefore, further Phase 2 and Phase 3 clinical trials involving a larger number of patients are needed to confirm the ultimate clinical therapeutic effect, such as delaying the progression of physical disability. The potential for long-term neurotoxicity also needs to be monitored.