Before the discovery of DNA only seventy years ago, researchers and physicians alike had no idea how to tackle genetic disorders. Now, with the discovery of a new method of treatment called gene editing, scientists have gained the means to make revolutionary progress. As opposed to a great deal of treatments which involve medication to alleviate symptoms or even those that target the cause of the symptoms, gene therapy is revolutionary in that its mark is the root cause - the genetic DNA.
This method of treatment involves the introduction of genes into a particular cell using a vector. Viruses, which are commonly utilized as vectors, can be edited to be benign to the patient and instead be used solely as a delivery mechanism. The vector can be delivered either through direct injection into the patient, or cells can be withdrawn from the patient and injected with the vector-carrying gene before being reinjected into the patient. Once in the patient’s cells, the new gene can function in one of two ways: (1) serve as a healthy, functional gene in place of the original, mutated gene causing the disease or (2) provide new genes for the body to attack the disease.
The first successful use of gene therapy was on a patient diagnosed with adenosine deaminase (ADA) deficiency. This inherited condition is characterized by a mutation in the ADA gene, which prevents the conversion of a toxic molecule into a harmless one. Ultimately, the condition results in a significantly reduced number of lymphocytes in the individual, leading to an extremely weakened immune system and potentially life-threatening infections. In 1990, the team of Drs. W. French Anderson and Michael Blaese utilized a retrovirus to insert a normal ADA gene into the patient’s white blood cells before reinjecting the cells into her body. Over the course of two years, the patient received this ongoing treatment of infusion of corrected cells and was eventually able to lead a normal life.
Since that first successful case, research in gene therapy has rapidly grown over the decades. There are now hundreds of clinical trials that use similar approaches to treat a variety of diseases, ranging from other immune deficiencies to blood diseases to cancers. Gene therapy carries risks which leave patients questioning whether the potential benefits outweigh the risks. As it is still largely in the research stages, this technique is far from “perfected” to the same degree as alternative forms of medicine. Risks vary from an adverse reaction of the immune system to the virus, to targeting the incorrect cells and causing damage to healthy cells. While a patient’s life can be transformed should the procedure be successful, these risks can just as easily devastate that same patient’s outlook with one mistake.
The ethics surrounding such an innovatively promising yet controversial treatment stretch far beyond a mere debate of whether the risks are worth it; there are numerous questions about the morality of gene therapy as well (more information here). Despite the promise that gene therapy carries for patients and families affected by genetic diseases, there are countless concerns for the future of such procedures. Similar to concerns about CRISPR-Cas9, a technological advancement that allows for the editing of genes and their functions, there is apprehension about which genes should ethically be edited. An example of such is trait enhancement. Should an individual be allowed to edit their height? Their intelligence? Their athletic ability? Coupled with this is the concern of society becoming less accepting of those who either cannot afford or choose not to participate in gene therapy. There is also controversy surrounding germline gene therapy; since this directly targets germ cells, which eventually mature into gametes, the effects of gene editing carry into future generations. Though this could prevent one’s offspring from inheriting and developing a particular disease, the effects of such editing could also produce new mutations, ones that would be passed down in future generations.
Though research in gene therapy has blossomed over the past several decades, it remains a largely unexplored territory. However, with the hundreds of ongoing clinical trials today, both researchers and patients alike are hopeful for therapeutic, and maybe one day preventative, treatments in the near future.