Liver Directed Disease

Adeno-associated virus (AAV) is a non-enveloped virus that can be engineered to deliver DNA to target cells, tissues or organs, which has attracted a large amount of attention in clinical-stage therapeutic fields. Especially, much of the enthusiasm for liver-directed AAV therapy development has been invested and already gained preclinical and clinical successes in different liver disorders. As a leading company in the gene therapy, Creative Biolabs focuses on the historical context, vector design, and future developments of AAV, as well as provides high-end liver-directed AAV gene therapy to introduce more therapeutic options for more patients.

Overview

AAV is a protein shell that surrounds and protects a small, single-stranded DNA genome of ~4.8 Kb. Its single-stranded genome comprises three genes, Cap (Capsid), Rep (Replication), and aap (Assembly). However, this wide-type AAV is not the form that is used to generate therapeutic outcomes.

Figure 1. Schematic representation of the basic components of a gene insert packaged inside rAAV gene transfer vector. (Aronson, 2019)

The liver is a remarkable target for in vivo gene therapy since hepatocytes can easily access to vectors injected into the circulation through pores in liver capillaries. Recombinant AAV (rAAV), lacking viral DNA, is basically a protein-based nanoparticle modified to traverse the cell membrane, where it can finally traffic DNA cargo into the nucleus of a cell. rAAV vectors target hepatocytes with higher efficiency. A number of clinical trials currently have been planned and are ongoing in the classic mouse and dog models of hemophilia A and B, exhibiting clear and potent long-term benefits from the administration of AAV vectors, along with other rare indications.

AVV Vector Design Services

So far, AAV as one of the most actively investigated gene transfer vehicles for liver-directed therapy has made impressive strides. AAV-mediated vector transfer of a functional copy of clotting factor IX gene into hepatocytes has proven to be safe and shown long-lasting reduction of bleeding episodes in patients with hemophilia B. In addition, this approach has been performed by Creative Biolabs to accomplish many projects in distinct organs, such as retina, skeletal muscle, and central nervous system.

Figure 2. Adeno-associated virus serotype 8 (AAV8)-mediated gene therapy for liver directed diseases. (Aronson, 2019)

Due to multiple conditions affecting hepatocytes and liver function, there's an intense interest in developing AAV gene therapy products for liver-based diseases. Here, we have established a series of platforms to manipulate sustained refinement of AAV vector properties, to discover novel forms of AAV capsids, and to complete valid therapeutic studies in diseased animal models. And our rational rAAV vector design services involve these methods:

• Dual, overlapping vector strategy

To solve the packaging size of the expression cassette (placed between two inverted terminal repeats (ITRs)).

• Self-complementary vector strategy

To bypass a process that single-stranded AAV-delivered transgene needs to be converted into a double-stranded transgene, which is a limiting step in the onset of transgene expression.

Why Choose Us?

As well, we have abundant experience in developing AAV products for some specific liver disorders, including Pompe disease, Alpha-1 antitrypsin deficiency, and Hemophilia A/B. There's a list explaining why our AAV vectors are useful for liver-directed gene therapies, particularly when considering commercial drug development.

• Sample components (vector capsid/protein coat and DNA genome);
• The conserved vector capsid structure and the inherent stability;
• Compared with other vector systems, analysis of purity and identity of the final AAV vector are simpler because no other proteins participate in the vector capsid;
• The vector capsid enables downstream purification unit operations, such as heat inactivation, ion-exchange chromatography, filtration and liquid handling operations.

With the advent of unique capsid serotype and organ-specific promoters, as well as a better understanding of immune responses to AAV administration, the strategy of AAV-mediated gene therapy has rapidly progressed over the past decade. Upon improvements in delivery, capsid and vector genome designs, Creative Biolabs offers the safest rAAV particles without any viral genes and containing DNA sequences of interest to meet customers' needs on therapeutic applications. For more information, please feel free to contact us or directly send us an online inquiry.

References

1. Aronson, S.J.; et al. (2019). Liver-directed gene therapy results in long-term correction of progressive familial intrahepatic cholestasis type 3 in mice. J Hepatol. 71(1): 153-162.
2. Naso, M.F.; et al. (2017). Adeno-associated virus (AAV) as a vector for gene therapy. BioDrugs. 31(4): 317-334.