Gene therapy for genetic diseases refers to the application of genetic engineering techniques to introduce normal genes into the cells of patients to correct the defects of the disease-causing genes and eradicate the genetic diseases. The way of correction can be to repair the defective gene in situ, or to transfer the functional normal gene into a part of the cell genome to replace the defective gene.

A gene is a basic functional unit that carries biological genetic information, and is a specific sequence located on a chromosome. To introduce foreign genes into biological cells, certain technical methods or vectors must be used. Current methods of gene transfer are divided into biological methods, physical methods, and chemical methods.

Adenovirus vector is currently one of the most commonly used viral vectors for gene therapy. Gene therapy is currently mainly used to treat diseases that pose a serious threat to human health, including genetic diseases (such as hemophilia, cystic fibrosis, family hypercholesterolemia, etc.), malignant tumors, cardiovascular diseases, and infectious diseases (such as AIDS, rheumatoid, etc.).

Gene therapy is different from conventional treatment methods. In general, the treatment of diseases is aimed at various symptoms caused by genetic abnormalities, while gene therapy is aimed at the root of the disease-the abnormal gene itself. There are two forms of gene therapy: one is somatic cell gene therapy, which is being widely used; the other is germ cell gene therapy, which is restricted because it can cause genetic changes.

The trends of gene therapy: genetic modification is still mainstream, gene editing is promising.

Multi-factors contribute to the success of gene therapy

The outbreak of gene therapy began in the early 1990s, and now looking back at the successful cases of gene therapy at that time, more or less with some luck ingredients. After nearly 30 years of scientific and technological development, gene therapy has become more and more mature, and the success rate has continued to increase, mainly due to several factors: (1) The improvement of viral vectors has improved the effectiveness and safety of treatment, such as the most widely used lentiviral vectors and adeno-associated virus vectors; (2) The development of vector preparation and identification technology has greatly improved the purity and efficacy of vectors, which not only improves the success rate of cell transfection, but also reduces the incidence of adverse reactions; (3) The basic biological knowledge continues to increase, making scientists' better understanding of target cells, tissues and organs, can more accurately predict the effects and effects of gene therapy side effects, make a good response plan in advance; (4) more detailed clinical observation and more effective molecular monitoring also help scientists use more accurate evidence to grasp the efficacy and safety of gene therapy; (5) scientists have been more cautious about gene therapy clinical trials and have improved the design of clinical trial protocols.

Technology and talent are the biggest barriers in the industry

Although gene therapy has made some progress in some areas, there are still many problems to be solved. The difficulties in gene therapy technology are mainly how to improve effectiveness and reduce safety risks. Like many emerging technologies, the key technologies and talents that can solve the key points in the industry are currently the biggest barriers in the gene therapy industry.

For gene therapy based on transgenic technology, the technical bottlenecks encountered at this stage are mainly: (1) Most of the viral vectors lack targeting and cannot specifically infect diseased cells, even if different subtypes of adeno-associated viruses are partially selective, which is far from the level of specific identification. Therefore, when "in vivo" treatment is performed, it can only be administered by local injection, which limits the scope of clinical application; (2) Retroviruses and lentiviruses, currently widely used in clinical, will insert their own genome into the host cell genome after infecting the host cell. The insertion position is random, and there is a potential risk of insertion mutation and malignant transformation of the cell; although the adeno-associated virus is non-integrated virus, but there is still the possibility of inserting into the host genome; (3) Ideal gene therapy should be able to regulate the expression of therapeutic genes at an appropriate level or way according to the nature and severity of the lesion, but the existing genes are introduced into the system and the capacity is limited, it cannot accommodate the entire gene or the complete regulatory sequence; (4) The viral vector has certain toxicity and immunogenicity, and is easily immunized by the human body after being injected into the patient's body; (5) The efficiency of gene introduction of viral vectors still need further improvement.

For gene therapy based on gene editing technology, the key technical difficulties are mainly (1) gene editing technology, especially the time of CRISPR technology is too short, there are too many uncertain factors, plus the cognition of function and regulatory networks of scientists on human genes is still very insufficient. Easy gene modification may cause unforeseen safety issues; (2) The efficiency of gene editing system for introducing cells and gene editing is not high, and it has not yet been able to achieve a large clinical Large-scale application; (3) Gene editing systems, like viral vectors, do not have cell targeting.

Regardless of transgenic technology or gene editing technology, to solve the technical problems faced by current clinical applications, optimizing and upgrading vectors and systems is the most direct, most effective, and unavoidable way. In addition, gene therapy is mostly an individualized treatment plan, and real commercialization also requires major optimization and improvement.

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