Challenges & Risks
Safety
One of the greatest challenges in gene therapy is safety. Each delivery method has its set of issues. Cell-based delivery requires the removal and insertion of stem cells or organ-specific cells, which would increase the possibility of infection and inflammation. Viral delivery could also cause inflammation as a result of a immune response to the virus. If the virus regains its pathogenicity, it could cause disease in the patient. In addition, the gene could be incorporated into the wrong area of the genome, leading to cancer. Without an accurate delivery method, there may always be a high risk of incorrect incorporation, making gene therapy extremely dangerous.
Ethics
Another issue that arises with gene therapy is ethics. There are many ethical dilemmas that are the result of gene therapy. Since gene therapy can be used in reproductive cells, the effect of gene therapy on those cells will impact every future generation that comes afterwards. Whether the decision to genetically engineer reproductive cells is ethical or not is still debatable. Another ethical question in the field of gene therapy is whether it should be used to create designer humans. Gene therapy would allow people to choose height, weight, build, and other physiological features. However, many in the field think that gene therapy should be exclusive to medical use, rather than for cosmetic purposes.
Availability
Gene therapy is currently unavailable to the general public. In many countries around the world, it is actually still illegal. Even in the United States, gene therapy is confined to clinical trials in small experimental groups. Much of the unavailability stems from safety and ethical issues. The history of gene therapy safety reveals many missteps and serious consequences from previous gene therapy trials. Since then, there has been bad stigma surrounding the safety and ethics of gene therapy. It is also immensely expensive - up to $1 million per patient in a clinical trial. This also prevents it from becoming a viable medical option in the near future.
Effectiveness
Unfortunately, gene therapy's effectiveness is still unproven. Although the bad stigma is wearing off and recent trials show progress, the majority of diseases still cannot be treated by gene therapy. Currently only a handful of diseases have shown significant progress when treated with gene therapy. There is lots of research that is still ongoing, but the aforementioned barriers still prevent gene therapy from being a great success. However, with further research and investment into gene therapy, its effectiveness should improve significantly over the next few decades.