AAV's Exquisite Banquet: Unveiling the Key Players

The realm of biotechnology has witnessed a flourishing period with the rapid development of AAV (Adeno-Associated Virus). As a groundbreaking technology in the field of cell and gene therapy (CGT), AAV has gained immense popularity in recent years. In this article, we delve into the significance of AAV and shed light on the prominent figures driving its success.

The Power of AAV as a Gene Therapy Vector:

When compared to traditional therapies, CGT offers superior efficacy and benefits from a range of regulatory supports, such as priority review, accelerated approval, and conditional approval. AAV, among the widely used viral vectors, stands out as a simple single-stranded DNA virus. It has found application in clinical trials targeting various rare genetic diseases, including eye disorders, blood disorders, and neurological conditions. Despite the industry's cooling trend, AAV continues to maintain its high appeal. Gene therapy typically involves delivering therapeutic genes to cells within the human body, a process that necessitates a vector. Widely employed viral vectors include adenoviral vectors (ADV), lentiviral vectors (LV), herpes simplex viral vectors (HSV), poxviral vectors (PV), and adeno-associated viral vectors (AAV). AAV, the simplest single-stranded DNA virus discovered to date, is regarded as the most promising gene therapy vector and has been employed in clinical trials for numerous rare genetic diseases spanning various fields, such as ocular disorders, hematological disorders, and neurodegenerative diseases. With the involvement of domestic and international enterprises, AAV is currently experiencing a period of rapid growth.

Unveiling the Secrets of AAV:

AAV, an enveloped single-stranded DNA virus, comprises a protein capsid and a 4.7kb single-stranded DNA genome. The capsid consists of three subunits: VP1, VP2, and VP3. Initially detected in laboratory adenovirus preparations in 1965, AAV has undergone over two decades of fundamental research. Subsequently, in 1995, it was first employed in the treatment of cystic fibrosis in humans. In the 21st century, an increasing number of AAV serotypes (AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9) have been discovered. Different serotypes possess distinct capsid proteins and exhibit unique spatial structures, influencing AAV's immunogenicity and tissue tropism. AAV2, the earliest and most commonly used serotype, is closely followed by AAV9. The tissue targeting capabilities of different AAV serotypes vary, with AAV8 primarily targeting the liver, AAV9 predominantly targeting the heart, and AAV1, AAV6, and AAV7 primarily targeting skeletal muscles.

The Dominance of AAV in Gene Therapy:

AAV has emerged as the most commonly utilized vector in current gene therapy endeavors, surpassing other viral vectors such as adenovirus, retrovirus, lentivirus, and herpesvirus. AAV-based gene therapy offers notable advantages, including high safety, long-lasting effects, a broad host range, and minimal integration into the host genome. Once inside the cell, it guides the production (expression) of specific proteins. Compared to other viral vectors, AAV demonstrates remarkable efficacy in delivering specific genes into immune-active cells. According to 2022 data from Cortellis, out of a total of 1,563 individuals utilizing viral and plasmid vectors, 824 were utilizing AAV vectors, either in development or already in the market. Adenovirus vectors accounted for 203, followed by 106 retrovirus vectors, 54 lentivirus vectors, 24 herpesvirus vectors, and 87 plasmid vectors, with the remainder unspecified.

The Pursuit of AAV-Based Therapies:

Given the advantages of AAV as a gene therapy vector, AAV-based therapies have witnessed remarkable progress in recent years. The expanding application areas, improved therapeutic outcomes, and innovative treatment strategies have garnered significant interest. Presently, there are seven globally approved AAV-based gene therapies, all targeting rare diseases. According to Cortellis' 2022 data, there are 152 AAV therapies in development for ophthalmic diseases, 252 for neurological diseases, 170 for metabolic diseases, 65 for skeletal muscles, and 46 for blood disorders. Neuroscience, ophthalmology, and metabolism are the primary focus areas.

Market Highlights and Future Prospects:

While AAV-based therapies have seen remarkable progress, challenges remain. The first approved AAV gene therapy, Glybera, developed by UniQure in the Netherlands, was limited by its high cost, restricted indications, and limited efficacy. Consequently, it was withdrawn from the market due to low patient uptake. However, the year 2022 marked a turning point for AAV therapies, with three drugs (Upstaza, Roctavian, Hemgenix) gaining regulatory approval. Notably, Hemgenix was approved by the FDA in November 2022 for the treatment of B-cell hemophilia in adults. The pricing and commercial success of AAV therapies will continue to shape the landscape of gene therapy.

AAV has emerged as a prominent gene therapy vector, offering unique advantages in terms of safety, efficacy, and tissue targeting. The growing number of AAV-based therapies in development and on the market signifies the potential and demand within the field of gene therapy.