Brief Introduction About Biological Analysis Of Gene Therapy

Biological analysis of gene therapy is the scientific evaluation of gene therapy products in terms of pharmacokinetics, pharmacodynamics, immunogenicity, safety, and other aspects in vivo. Gene therapy products are a new type of drugs that use exogenous genes or gene editing techniques to treat genetic or acquired diseases, with the characteristics of high specificity, long duration, and potential efficacy. Currently, gene therapy products mainly include naked DNA, RNA, vector-mediated gene transfer, and gene editing.

Vector-mediated gene transfer is the use of viral or non-viral vectors to deliver the target gene into the target cells, making it express or integrate into the host genome in the cells. Vector-mediated gene transfer is the most commonly used gene therapy method, and one of the most promising methods for clinical applications. Among them, adeno-associated virus (AAV) vector is a non-enveloped, single-stranded DNA defective virus, with the advantages of high safety, low immunogenicity, wide host range, and stable expression. It is considered to be one of the most ideal gene therapy vectors.

The bioanalytical strategy for AAV-based gene therapy drugs needs to be formulated according to its special drug mechanism and drug characteristics. Generally speaking, the following aspects need to be considered:

1. Drug exposure: The concentration or copy number of AAV vector and target gene in blood or other biological samples, reflecting the distribution and clearance of the drug in vivo. Usually real-time quantitative PCR (qPCR) method is used for detection.
2. Biodistribution: The distribution of AAV vector and target gene in different tissues and organs, reflecting the targeting and tissue specificity of the drug in vivo. Usually qPCR or in situ hybridization (ISH) method is used for detection.
3. Persistence and clearance: The survival time and elimination pathway of AAV vector and target gene in vivo, reflecting the stability and metabolism of the drug in vivo. Usually qPCR or ISH method is used for detection.
4. Viral shedding: The possibility of AAV vector being excreted or secreted out of the body through excreta or secretions, reflecting the potential risk of the drug to the environment and others. Usually qPCR or infectious assay method is used for detection.
5. Immunogenicity: The possibility of AAV vector and target gene causing immune response in the body, reflecting the impact of the drug on the body's immune system. Usually ELISA or electrochemiluminescence (ECL) method is used to detect anti-AAV antibody or anti-target protein antibody, and ELISPOT or flow cytometry method is used to detect cellular immune response.
6. Immune toxicity: The possibility of AAV vector and target gene causing immune-related adverse reactions in the body, reflecting the impact of the drug on the body's safety. Usually Bio-Plex or ECL method is used to detect cytokines or inflammatory factors, and hematological or biochemical methods are used to detect blood or liver function.