Gene Therapy Anniversary Passes with Little Fanfare
Last month marked the 25th anniversary (14th September 1990) of the first gene therapy procedure to be carried out in a human. The patient was a four-year-old girl who suffered from a rare disease that left her defenceless against any infection. The trial was widely depicted as a huge success, with gene therapy being hailed as one of the greatest advances in modern day medicine. The ability to treat diseases that were hitherto incurable represented the Holy Grail in medicine. The one-off treatment nature of gene therapy, rather than long term, or even life long uses of medicines to treat an illness, is also very attractive to clinicians and patients but not so attractive to the pharmaceutical companies developing these treatments, who need to recoup their development costs. Given the huge potential of gene therapy, as seen in the 1990’s, the passing of this milestone with so little media coverage perhaps emphasises better than any other way its stormy passage over the last two decades. So why has gene therapy struggled to meet its potential, and what is its future in the 21st century as a treatment rare and malignant disease in children and adults?
What Exactly is Gene Therapy?
Many human diseases, including cancer, are caused by defects that occur in our genes. Gene therapy attempts to treat disease by correcting the bad gene or genes. It is relative easy to manufacture, in the laboratory, a healthy functioning gene to replace the diseased one. The problem is that this “good gene” needs to be delivered to the affected cells without causing adverse effects to the patient. In the early days of gene therapy this was achieved by using a relatively harmless virus to deliver the new gene to the patient’s cells. These so called viral vectors are essential “gene vehicles” that allow good genes to be transported into the patients cells to effectively replace the damaged or dysfunctional genes. However, there were unforeseen and tragic consequences to this method of gene delivery that precipitated a spectacular fall from grace for gene therapy.
From Glorious Potential to Disaster
Just nine years after the first application of gene therapy, the promise of using replacement genes to cure hereditary diseases and cancer lay in tatters, following the death of an eighteen-year-old volunteer, Jesse Gelsinger. Who succumbed to multiple organ failure following a gene therapy trial at the University of Pennsylvania. The exact reason behind his death and the link with the adenovirus vector used, still remains a mystery. However, it is likely to have been due to the patient’s immune system overreacting to the viral vector used. This tragic incident was a wake up call for the 1990’s scientists caught up in the hype surrounding gene therapy and its perceived simplicity. Further problems were to follow, in 2003 a French gene therapy patient developed a leukaemia-like condition as direct result of the treatment. This led to the worldwide suspension of gene therapy trials. In this latter incident the viral vector delivered the replacement gene into a normal gene called LMO-2 causing it to miss function. Damage to this gene had previously been linked to a number of childhood cancers. The miracle of gene therapy was, in this instance, dashed by the random way in which the viral vectors used inserted the replacement gene into the cells genome.
Gene Therapy in the 21st Century
Despite these setbacks, scientists and clinicians have been slowly rebuilding the reputation of gene therapy and there is now renewed optimism. Careful regulation of clinical trials involving gene therapy and improved gene technology that can silence overactive genes or repair rather than replace them has revitalised the field. However, as it was in the early years of gene therapy, the burden of this new wave of technological and clinical development has fallen onto the shoulders of those working with rare, so called, orphan diseases, many of which are found in children.
After years of setbacks and false dawns it seems that a resurgence in gene therapy is once again on the horizon. I am sure that patients and clinicians alike will welcome its return to prominence. There are caveats though, such as the potential costs of treatment. A recently licensed European gene therapy treatment comes with an eye watering price tag of around 1 million euros per patient. Other treatments, currently in development, have projected costs of around $1 million per patient. These record breaking treatment costs may well be linked to the small number of patients currently diagnosed with the diseases for which the therapy is targeted and the fact that gene therapy is typically a once only treatment. Yet the temptation to charge phenomenal prices for gene therapies must be fought now by government and public policy groups. The future may be looking brighter for gene therapy in its 25th anniversary year but but the overall costs to patients and healthcare providers, in particular for the treatment orphan diseases in children, need to be addressed as a matter of urgency.
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