Blog "Gene Therapy for Rare Diseases: Challenges and Progress"

● Introduction For decades people used to think that rare diseases happen in 1 out of 1 million people and it is hard to cure! I was one of those people, until I read a research paper mentioning the definition of rare diseases, surprisingly! Disease is considered rare when it affects 1 in 2000 people (there are over 300 million rare disease patients in the world), maybe one of them is around you and you don’t know! [1] There are different challenges facing rare diseases, one of them is the lack of treatment options, but recently scientists have finally developed effective and safe drugs for some types of rare diseases (there are more than 7000 rare disease types) [1][2]

● What is gene therapy and how does it work? The reason behind the rare disease is usually a malfunction/changed gene (which is called a mutation), in which a specific protein production is interrupted due to the mutation, in the gene therapy, a correct gene sequence is introduced to the body replacing or repairing the malfunctioning gene or adding a correct copy leading to normal protein production. [3] For example, in a rare disease called Charcot-Marie-Tooth genes that affect substances needed for muscle strength are defective, resulting in muscle weakness.[1] There are different ways of gene therapy to work: In-Vivo gene therapy, in which the correct gene is carried on a virus that doesn’t affect the body in a bad manner, then introduced to the body to replace the defective gene with the functioning correct one. [2] Ex-vivo gene therapy, in which a specific type of cells is taken from the patient, to introduce the correct gene carried on a virus but outside the body then those cells are introduced again in the body distributing and the correct gene replaces the malfunctioned one. Still, this type is more costly and complex than the in vivo. [2]

● Challenges facing gene therapy: There are many challenges facing scientists during their research in gene therapy, one of them is the very high cost, but it is supposed that the increasing competition in this field will decrease its cost over time. Additionally, this cost is lower than trying to treat the patients with other types of drugs. There are many ethical concerns in this field and this is one of the most challenging issues in it. Scientists are still searching to achieve gene therapy to treat diseases with multiple gene mutations (different gene alterations). Safety in the long term is also one of the most important challenges that will be resolved by time and scientists' assessment.[2]

● An example of a disease that has clinically effective gene therapy: You may think that this research is hard to be in our reality, and there is no treatment for a real genetic rare disease, but here is an example of a rare disease that has gene therapy as a treatment option!

Hemophilia A, which is also called factor VIII (8) deficiency or classic hemophilia, in which the patient has a gene mutation leading to malfunction of a clotting factor called factor VIII. [4] Recently, it has been approved to use a gene therapy replacing the defective gene with another one leading to expression of the deficient factor VIII. [5]

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