Genetic diseases are a leading cause of death and disability in Canada with immense economic and societal burdens. Gene therapy has emerged as a means to effectively treat genetic diseases; however, current gene therapies are limited by their high manufacturing costs, the inability to re-dose, and the safety concerns of some viral vectors.

CRISPR genome editing is a new therapeutic approach that aims to directly repair the underlying disease-causing mutations. Conventional CRISPR methods are limited as in vivo therapeutics because they introduce DNA breaks and cause frequent off-target edits. Newer base editors and prime editors overcome the limitations traditional CRISPR genome editing methods because they do not introduce DNA breaks.

However, the delivery of genome editors to affected tissues remains a challenge. Viral vectors, such as AAV, are unsuitable for genome editing because their long expression (years) increases the probability of unintended edits. In contrast, the transient expression (hours-days) of RNA encoding genome editors via nanoparticles is well suited for genome editing, and unlike viral vectors, nanoparticles can be readministered. However, nanoparticle delivery of complex genome editing cargos (large mRNA + small gRNA) remains a challenge, especially to extra-hepatic target tissues such as muscle. To address this, we are developing new ways to safely deliver these new editors using lipid nanoparticles.

To efficiently measure the in vivo effectiveness of genome editor delivery via LNPs, we have developed transgenic mice that carry mutations in reporter genes. Precise gene repair of these mutations produce a functional enzyme that emits light (luminescence) that sensitive imagers can detect to precisely measure the location and extent of gene editing in living animals. We have made progress in our goal towards efficient and safe in vivo genome editing that we will share.