Gene therapy involves the treatment of diseases by introducing genetic material into diseased cells. Although it is mostly used to treat inherited genetic diseases, it can also be used to treat some cancers and viral infections. Implementing a safe and effective gene therapy is complicated because the majority of gene therapies use a modified virus, called a vector, to deliver the genetic material to diseased cells and this viral delivery system still needs a lot of refinement.
Several new gene therapies have been approved by the US FDA and EMA in Europe in the last decade. Notable ones include Zynteglo developed by Bluebird Bio for treating thalassemia (approved by the EMA in 2019), Luxturna developed by Spark Therapeutics for treating inherited retinal disease (approved by the FDA in 2018), and Zolgensma developed by Novartis for treating spinal muscular atrophy (approved by the FDA in 2019). More gene therapy trials are currently underway for HIV, sickle cell anemia, and ADA-SCID, among other conditions.
Some notable genes of interest being investigated and currently in advanced stages of clinical trials include the hemoglobin (β-chain) gene for β-Thalassemia (severe sickle cell), p53 gene for head and neck squamous cell cancer, CTFR gene for cystic fibrosis, Factor VIII gene for Hemophilia A, Factor IX for Hemophilia B, AADC gene for Parkinson’s disease, CCR5-negative CD4 cells for HIV, and SMN1 gene for Spinal Muscular Atrophy (SMA I). Major Pharma players pursuing work in this arena include Bluebird Bio, Spark Therapeutics, Orchard Therapeutics, SiBiono, Biogen, BioMarin, Pfizer, Voyager Therapeutics, Novartis, and American Gene Technology.
Gene therapy is the future
According to a 2020 report by the Pharmaceutical Research and Manufacturers of America (PhRMA), there are 362 investigational cell and gene therapies currently in development. This is a 20% increase from 2018! Many gene therapies, including one for hemophilia, are expected to be approved and reach the market in the next couple of years. Several therapeutic genes such as tumor suppressors, suicide genes, inflammatory cytokines, and micro‐RNA genes are also under investigation.
With hundreds of potential gene therapies in the pipeline, the US FDA expects to see new gene therapy applications double every year. In fact, they predict that the US will be approving 10 to 20 different gene therapies every year by 2025. However, although gene therapies are revolutionizing medicine, there are several technical, logistical, and economic challenges in commercializing and democratizing these treatments. To overcome these challenges, close collaboration with all stakeholders will be key.
Slow and steady progress in gene therapy, focusing on making it affordable to patients, is also crucial. If we can achieve this, it has the potential to eliminate many diseases in the foreseeable future.