Our group continued the activities related to the project aimed at developing an effective gene therapy for Charcot-Marie-Tooth disease type 2A (CMT2A), a genetic disease caused by mutations in the Mitofusin 2 (MFN2) gene. Clinically, the disease manifests itself as a sensory-motor polyneuropathy. The MFN2 protein, located in the mitochondria, is essential for the survival of the cells and for their correct functioning. Among the possible therapeutic approaches, gene therapy aimed at correcting the underlying cause of the disease represents a rational therapeutic approach. This type of strategy has given promising results in clinical trials with adeno-associated vectors type 9 (AAV9) for different neurodegenerative diseases (www.clinicaltrials.gov), even coming to be approved as a drug for example for Spinal Muscular Atrophy associated to SMN1 gene mutations. Hence, taking advantage of the growing knowledge in this sector, we set out to use the same type of approach also for CMT2A. However, in the case of this disease, not only the lack of the “healthy” gene, but also the presence of the “sick” MFN2 protein are the cause of the disease. For this reason, to set up a therapy for patients, it is necessary to introduce the “healthy” gene, as in the case of SMA, but also to switch off the “diseased” gene. Therefore, the development of a gene therapy for CMT2A requires additional efforts which result in a greater number of experiments and in longer times.

In this perspective, we have generated two AAV9 vectors, one to turn off the “sick” MFN2 gene and one to allow the expression of the “healthy” one. This type of strategy was effective in the cellular model of the disease consisting of neurons derived from CMT2A patients cells. Treatment with AAV9 vectors led to a significant improvement in the pathological phenotype in these cells. The results of these experiments have been recently submitted to an indexed international scientific journal for publication.

In addition to the results obtained in cellular models, the evaluation of the effectiveness of this strategy in pre-clinical models is necessary before a clinical trial can be proposed to the FDA / EMA. In this perspective, the availability of animal models capable of reproducing the symptoms of the disease is essential in order to evaluate the effectiveness of a strategy. Unfortunately, the only animal model available for several years was unable to reproduce the disease, making it difficult for us to use it for our research purposes. Recently in 2019, Zhou and collaborators generated a new model of CMT2A (Tg (Thy1-MFN2 * R94Q) 44Balo / J; Zhou et al., 2019). Unlike the previous model, the animals show symptoms and neuropathological characteristics typical of this disease, thus making it a much more reliable model than the previous one, especially for studies aimed at evaluating the effectiveness of a therapeutic strategy. In particular, our group began to monitor animals which, in line with what has been described in the literature, are significantly smaller in size than healthy animals and show signs of muscle weakness that limits their ability to move. Unfortunately we have observed a considerable variability between animals, an aspect that will require a greater number of experiments to achieve statistically significant results. In these past weeks, we started treating the first animals with AAV9 vectors and we are monitoring the phenotype of the animals to see any improvements in the symptoms of the disease.

Since July 2020, our research group is also collaborating with an American company for the production of our AAV9 vectors with features suitable for clinical trials in patients.

All these results that we have been able to achieve in recent years represent the necessary steps to arrive at an effective clinical trial in patients in the shortest time possible.

Updated 20th September, 2022