VectorBuilder Announces Highly Stable MuteFree™ AAV for Gene Therapy
VectorBuilder has developed the MuteFree™ AAV vector to solve ITR sequence instability in gene therapy manufacturing. This technology reduces the mutation rate to 0% using standard E. coli, significantly improving viral yield and reliability.
📋 Article Processing Timeline
- 📰 Published: April 14, 2026 at 15:30
- 🔍 Collected: April 14, 2026 at 07:01
- 🤖 AI Analyzed: April 19, 2026 at 19:22 (132h 20m after Collected)
Summary
VectorBuilder announced the development of the highly stable MuteFree™ AAV vector to solve the instability of the ITR sequence of AAV vectors, a challenge in gene therapy development. The MuteFree™ AAV vector is compatible with standard manufacturing workflows and common E. coli strains, and reduces variations in viral yield and gene expression effects. By adopting this technology, the reliability of gene medicine development will be improved, maintaining consistency from research to clinical manufacturing. A paper introducing this technology has been published on bioRxiv, and the research results will also be presented at the ASGCT Annual Meeting in the United States.
Chicago (April 14, 2026) — VectorBuilder, a global leader driving the field of gene delivery technologies and CDMO solutions, today announced "MuteFree™ AAV", a highly stable AAV vector designed to improve the instability of ITR sequences, which is one of the major research challenges in gene therapy development. A research paper on this technology has been published on the preprint server bioRxiv.
Adeno-associated virus (AAV) is currently the most widely utilized gene delivery vector in gene therapy development. However, on the other hand, challenges such as heterogeneity between manufacturing lots and variations in therapeutic efficacy are major barriers to clinical development and practical application. One of the main factors is the instability of the inverted terminal repeat (ITR) sequence of the AAV vector, which determines the success or failure of packaging the viral genome and expressing the transgene.
Figure 1. Sanger sequencing was performed on the ITRs of more than 300 AAV plasmid vectors received from research institutions and our partners in the industry. These plasmid DNA vectors had passed quality control (QC) tests by restriction enzyme digestion upon receipt. Sequence analysis revealed that base sequence mutations had occurred in approximately 40% of the ITRs of the AAV transfer vectors (Nucleic Acids Res. 2025. doi: 10.1093/nar/gkaf697).
VectorBuilder independently analyzed hundreds of AAV plasmid vectors collected from academic institutions and industrial laboratories worldwide, revealing that base mutations were present in approximately 40% of the ITR sequences (Bai et al., Nucleic Acid research. 2025 Jul 19;53(14) doi: 10.1093/nar/gkaf697). It is known that incomplete ITR sequences directly affect the efficiency of viral packaging and the expression level of delivered genes. Therefore, it is suggested that mutations in the ITR sequence lead to a decrease in viral yield, heterogeneity in the manufacturing process, and furthermore, a decrease in the reproducibility of the gene therapy effect. In some cases, to obtain sufficient therapeutic effects, higher doses of virus administration were required, which brought about new challenges such as increased manufacturing costs and elevated toxicity risks due to high-dose administration.
Various approaches have been attempted so far to improve the instability of ITR sequences. Examples include using special E. coli strains, controlling the amplification behavior of plasmid DNA by adjusting E. coli culture conditions, or modifying the ITR sequence itself. These efforts have shown a certain effect in reducing the mutation rate to the ITR; however, they tend to complicate the manufacturing process of plasmid DNA, and have still not led to a fundamental improvement in sufficient plasmid stability or viral yield.
MuteFree™ was developed to overcome the limitations of these conventional methods. The highly optimized MuteFree™ AAV vector system achieves high compatibility with widely used E. coli strains and standard manufacturing workflows while maintaining the integrity of the ITR sequence at a high level. As a result, it enables more stable and highly reproducible AAV manufacturing without changing the existing manufacturing pipeline, strongly supporting everything from research and development to manufacturing scale-up.
Figure 2. By switching to MuteFree™ AAV, the base mutation rate of the ITR sequence after 10 consecutive subcultures in E. coli (more than 160 population doublings) decreased from 48.1% to 0% for single-stranded AAV (ssAAV) and from 31.8% to 0% for self-complementary AAV (scAAV). The ITR sequences were analyzed by Sanger sequencing.
VectorBuilder announced the development of the highly stable MuteFree™ AAV vector to solve the instability of the ITR sequence of AAV vectors, a challenge in gene therapy development. The MuteFree™ AAV vector is compatible with standard manufacturing workflows and common E. coli strains, and reduces variations in viral yield and gene expression effects. By adopting this technology, the reliability of gene medicine development will be improved, maintaining consistency from research to clinical manufacturing. A paper introducing this technology has been published on bioRxiv, and the research results will also be presented at the ASGCT Annual Meeting in the United States.
Chicago (April 14, 2026) — VectorBuilder, a global leader driving the field of gene delivery technologies and CDMO solutions, today announced "MuteFree™ AAV", a highly stable AAV vector designed to improve the instability of ITR sequences, which is one of the major research challenges in gene therapy development. A research paper on this technology has been published on the preprint server bioRxiv.
Adeno-associated virus (AAV) is currently the most widely utilized gene delivery vector in gene therapy development. However, on the other hand, challenges such as heterogeneity between manufacturing lots and variations in therapeutic efficacy are major barriers to clinical development and practical application. One of the main factors is the instability of the inverted terminal repeat (ITR) sequence of the AAV vector, which determines the success or failure of packaging the viral genome and expressing the transgene.
Figure 1. Sanger sequencing was performed on the ITRs of more than 300 AAV plasmid vectors received from research institutions and our partners in the industry. These plasmid DNA vectors had passed quality control (QC) tests by restriction enzyme digestion upon receipt. Sequence analysis revealed that base sequence mutations had occurred in approximately 40% of the ITRs of the AAV transfer vectors (Nucleic Acids Res. 2025. doi: 10.1093/nar/gkaf697).
VectorBuilder independently analyzed hundreds of AAV plasmid vectors collected from academic institutions and industrial laboratories worldwide, revealing that base mutations were present in approximately 40% of the ITR sequences (Bai et al., Nucleic Acid research. 2025 Jul 19;53(14) doi: 10.1093/nar/gkaf697). It is known that incomplete ITR sequences directly affect the efficiency of viral packaging and the expression level of delivered genes. Therefore, it is suggested that mutations in the ITR sequence lead to a decrease in viral yield, heterogeneity in the manufacturing process, and furthermore, a decrease in the reproducibility of the gene therapy effect. In some cases, to obtain sufficient therapeutic effects, higher doses of virus administration were required, which brought about new challenges such as increased manufacturing costs and elevated toxicity risks due to high-dose administration.
Various approaches have been attempted so far to improve the instability of ITR sequences. Examples include using special E. coli strains, controlling the amplification behavior of plasmid DNA by adjusting E. coli culture conditions, or modifying the ITR sequence itself. These efforts have shown a certain effect in reducing the mutation rate to the ITR; however, they tend to complicate the manufacturing process of plasmid DNA, and have still not led to a fundamental improvement in sufficient plasmid stability or viral yield.
MuteFree™ was developed to overcome the limitations of these conventional methods. The highly optimized MuteFree™ AAV vector system achieves high compatibility with widely used E. coli strains and standard manufacturing workflows while maintaining the integrity of the ITR sequence at a high level. As a result, it enables more stable and highly reproducible AAV manufacturing without changing the existing manufacturing pipeline, strongly supporting everything from research and development to manufacturing scale-up.
Figure 2. By switching to MuteFree™ AAV, the base mutation rate of the ITR sequence after 10 consecutive subcultures in E. coli (more than 160 population doublings) decreased from 48.1% to 0% for single-stranded AAV (ssAAV) and from 31.8% to 0% for self-complementary AAV (scAAV). The ITR sequences were analyzed by Sanger sequencing.