CRISPR in clinical trials: the future of gene editing

Gene therapy is a relatively new concept. Considering that the idea was only first introduced in a tangible way in 1990, the possibility of actual gene therapies has seemingly catapulted during the last 30 years. This is because of the breakthrough innovation of gene editing. Whereas early gene therapy was focused on adding genes to treat rare genetic disorders, gene editing promises to treat a much more expansive therapeutic array. Gene editing could potentially be the cure for an incredible range of illness — from HIV to cancer — and could even serve as an injection for high cholesterol.^1,2 Of course, this makes complete sense; if you can target and change the DNA inside cells, all systems are affected.

Gene editing technology is currently being explored in disease prevention or treatment. For the most part, it has been applied largely via cells and in animal models.^3,4 The use of gene editing in single cell conditions such as sickle cell disease, cystic fibrosis, haemophilia and more complex diseases such as mental illness, heart disease, HIV and cancer, might prove to be the next forefront in medicine.

The promise of this therapy is magnified by CRISPR-Cas9, which stands for “clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9.”³ The technology is not only less expensive than other gene editing treatments, it is also more effective, accurate and efficacious, which has all worked to contribute to the much-deserved buzz around it in the scientific community at large. CRISPR-Cas9 was developed from a genome editing system that takes place naturally in bacteria. These bacteria are able to sequester pieces of genetic information, or DNA, from viruses threatening the bacteria. This captured DNA is then used by the bacteria to create DNA segments, which are called CRISPR arrays. If the same virus attacks the bacteria again, the bacteria will harness the CRISPR arrays and produce RNA segments that target the DNA of the attacking virus. The bacteria are essentially able to remember all viruses and similar viruses. Using the Cas9 or a related enzyme, the bacteria is able to destroy the DNA of the virus, literally cutting it apart. This renders the virus inoperative and non-viable.³

When applied in a lab scenario, the technology works similarly to these bacteria. To harness the technology, scientists process a segment of RNA with a guiding sequence, which will bind to a specific, targeted DNA sequence present within a genome. As with the bacteria, this altered RNA further attaches to the Cas9 enzyme and is able to target the particular DNA sequence within the genome and, as with the bacteria, cuts it. After the DNA has been cut, the cell, which has a natural ability to heal, is harnessed by scientists for repair. Scientists are then able to add to or edit out genetic information within the DNA sequence. The option to alter the DNA further by replacing an already existent segment with a customised sequence is also possible.³