Preclinical development of therapies by modulation of Dynamin 2 expression – DynANR

Centronuclear myopathies (CNM) are rare congenital myopathies characterized by abnormal central position of nuclei in the muscle fibers in absence of muscle regeneration. The three main forms include the X-linked recessive CNM due to Myotubularin (MTM1) mutations, and the autosomal forms due to dominant mutations of Dynamin 2 and recessive mutations of Amphiphysin 2 (BIN1) and Ryanodine receptor 1. Dynamin 2 (DNM2) is a key actor of membrane trafficking and a regulator of both actin and microtubule cytoskeletons. Our two teams developed potential therapies for CNMs based on reduction of the DNM2 expression. The first therapy is based on RNA interference-mediated allele-specific silencing of mutated or non-mutated DNM2 mRNAs. We developed siRNA against the most frequent DNM2 mutation causing the dominant CNM and versatile siRNA able to silence all the DNM2 mutations. Their therapeutic benefit was validated in one animal model and patient-derived cells. The second therapy, devoted to reduce overall DNM2 expression especially using antisense oligonucleotides, successfully rescued animal models of the MTM1-, BIN1-, -and DNM2-linked CNM genetic forms. Based on these first proof of concepts, DynANR aims at proceeding to preclinical development of these two therapies for CNMs and extend their field of application through 4 tasks:

1. Development of the allele-specific therapy. We will optimize the Adeno-Associated Virus as vector for this therapy in a mouse model of classical adult form of dominant CNM and assess therapeutic efficacy of allele-specific silencing in muscle cells from patients and in a second mouse model mimicking the most severe form linked to DNM2 mutations. The benefit of the versatile allele-specific siRNA will be also assessed in MTM1- and BIN1-linked CNMs.

2. Development of the pan-allelic therapy. We will assess the therapeutic benefit of DNM2 overall reduction in another genetic form of CNM. We will also develop a new generation of oligonucleotides using another chemistry and another mode of action.

3. Gene editing. We will assess the efficacy of gene editing by CRISPR/Cas9 as a new technology for reducing DNM2 expression in both allele-specific and pan-allelic approaches. The therapeutic benefit will be assessed in mouse models of the MTM1- and DNM2-linked CNMs.

4. Biomarkers and new application. We will determine biomarkers to follow disease progression and therapy efficiency from transcriptomic profiling of CNM patient muscles. We will also determine the DNM2 level in a panel of neuromuscular disorders to highlight novel indications for DNM2 reduction.

By a reinforced interaction between our two teams, the ambition of DynANR is to accelerate the preclinical development of DNM2 therapies required for clinical trials targeting several forms of CNMs. The four tasks are based on preliminary data and on expertise, concepts, and methodologies already developed by the 2 partners, especially through previous ANR supports.