Adenoassociated virus (AAV) and lentivirus (LV) remain the biopharmaceutical industry’s preferred systems for in vivo and ex vivo delivery of therapeutic genes, respectively. Significant advances in virology and biomanufacturing are increasing vector safety and efficacy, but much remains to be learned about producing them at manufacturing scales and at requisite levels of quality. Drug developers also must address lingering concerns with vector immunogenicity. This featured report explores strategies for improving viral vector manufacturing. Read the articles below to learn more about increasing the scalability and efficiency of existing platform processes, making the most of vector-production facilities, minimizing immunogenicity risks with traditional vectors, and even developing alternative viral systems for delivery of gene therapies.

Harnessing the Untapped Power of the Human Commensal Virome
Tuyen Ong (Ring Therapeutics)
Most healthy humans are infected with unique lineages of anelloviruses, small single-stranded–DNA viruses that neither help nor harm their hosts. Until 2000, researchers seldom studied the Annelloviridae family because it showed no connection to disease and resisted easy cultivation. However, two decades’ worth of investigation has revealed that annelloviruses could be strong candidates for biotherapeutic delivery. This article explores potential advantages of annelloviruses as gene therapy vectors. Chief among those characteristics is the ability to evade immune detection, a factor that could help drug developers to minimize risks for vector immunogenicity.

Optimize Your Early Preclinical Process for Gene Therapy Success
Katie Roberts (WuXi Advanced Therapies)
It can take years or even decades to bring a novel gene therapy from drug discovery through regulatory approval. Although innovator companies cannot always predict what obstacles lie ahead in the drug-development journey, making good decisions early in process development can help to ensure success years down the line. This article explores how innovators can collaborate with contract development and manufacturing organizations (CDMOs) to select high-yielding plasmids, leverage efficiencies from platform approaches, and make seamless transitions from preclinical to clinical and ultimately commercial production.

Addressing Unwanted Immunogenicity in Gene Therapies
Carsten Brunn and Kei Kishimoto (Selecta Bioscience)
Immunogenicity remains a primary concern for developers of gene therapies based on adenoassociated virus (AAV) vectors. These delivery systems have resulted in adverse events during clinical evaluation, especially when administered at high doses, yet such doses often are required to be efficacious. Moreover, many patients are precluded from treatment because they have developed neutralizing antibodies (NAbs) for AAV, either through natural infection or from a previous gene therapy treatment. The writers of this article show why addressing both preexisting and de novo immunogenicity hurdles will be critical to unlocking the potential of gene therapies. They review current strategies for mitigating immune responses, highlighting recent developments involving coadministration of gene therapies and targeted immunosuppressive agents.

Building Manufacturing Capabilities for Adenoassociated Virus Vectors: Key Considerations for Facility Design and Operations
Brian Gazaille, with Curran Simpson (Regenxbio)
Demand for adenoassociated virus (AAV) vectors continues to exceed the biopharmaceutical industry’s ability to manufacture them. The imbalance stems in part from growing numbers of products advancing through clinical trials and into commercial stages. The COVID-19 pandemic also compelled many companies to redirect time, effort, and resources into materials and processes for SARS-CoV-2 vaccines and antivirals. Although contract manufacturers have pledged to install additional manufacturing capacity, some clinical-stage gene therapy developers are choosing to establish their own manufacturing capabilities. Herein, BPI’s associate editor speaks with the chief technical and operations officer of a clinical-stage gene therapy company that has opened GMP manufacturing capacity, with an eye to end-to-end control of AAV production. The conversation reveals key considerations for designing and operating AAV manufacturing facilities.

Effective Processing of Lentiviral Vectors
Ian Scanlon, Sujeong Yang, and Daniella Steel (Astrea Bioseparations)
Because current purification methods for LV vectors are based on tools used to manufacture monoclonal antibodies (MAbs) and other protein biologics, such processes are inefficient and not fit for purpose. In this article, representatives from the viral-vector purification team at Astrea Bioseparations explain why LVs are difficult to purify using traditional processes. Then, they introduce a novel nanofiber-based separation technology that holds promise for improving LV recovery and increasing sample throughput during process development stages.

Statistical Methodologies to Establish Control or Alert Limits for Nonparametric Distributed Numeric Variables with a Focus on Biopharmaceutical
Naveenganesh Muralidharan (Novartis Gene Therapies)
According to the FDA’s 2011 Process Validation Guidance, critical quality attributes and critical process parameters are trended to assess their statistical stability and their suitability for use in a continuous process verification program. Because bioprocess data often are not distributed normally, regular I-charts with control limits placed three standard deviations from the process mean cannot be used. Herein, the writer describes a detailed procedure for using Microsoft Excel formulas to establish statistical control limits for nonnormally distributed censored data.