Systematic studies on stabilization of AAV vector formulations by lyophilization

Nucleic Acid Delivery Nanotechnologies for In Vivo Cell Programming

In medicine, it is desirable for clinicians to be able to restore function and imbue novel function into selected cells for therapy and disease prevention. Cells damaged by disease, injury, or aging could be programmed to restore normal or lost functions, such as retinal cells in inherited blindness and neuronal cells in Alzheimer's disease. Cells could also be genetically programmed with novel functions such as immune cells expressing synthetic chimeric antigen receptors for immunotherapy. Furthermore, knockdown or modification of risk factor proteins can mitigate disease development. Currently, nucleic acids are emerging as a versatile and potent therapeutic modality for achieving this cellular programming. In this review, we highlight the latest developments in nanobiomaterials-based nucleic acid therapeutics for cellular programming from a biomaterial design and delivery perspective and how to overcome barriers to their clinical translation to benefit patients.

Drug product Formulation and Fill/Finish Manufacturing Process Considerations for AAV-Based Genomic Medicines

Adeno-associated viruses (AAVs) have become the delivery medium of choice for a variety of genomic medicine applications i.e., gene therapy, gene editing/regulation, and ex-vivo cell therapy. AAVs are protein-DNA complexes which have unique stability characteristics that are susceptible to various stress exposure conditions commonly seen in the drug product (DP) life cycle. This review takes a comprehensive look at AAV DP formulation and process development considerations that could impact critical quality attributes (CQAs) during manufacturing, packaging, shipping, and clinical use. Additional aspects related to AAV development reviewed herein are: (1) Different AAV serotypes with unique protein sequences and charge characteristics potentially leading to discrete stability profiles; (2) Manufacturing process challenges and optimization efforts to improve yield, recovery and purity especially during early development activities; and (3) Defining and identifying CQAs with analytical methods which are constantly evolving and present unique characterization challenges for AAV-based products.

Analysis of the impact of pluronic acid on the thermal stability and infectivity of AAV6.2FF

BACKGROUND

The advancement of AAV vectors into clinical testing has accelerated rapidly over the past two decades. While many of the AAV vectors being utilized in clinical trials are derived from natural serotypes, engineered serotypes are progressing toward clinical translation due to their enhanced tissue tropism and immune evasive properties. However, novel AAV vectors require formulation and stability testing to determine optimal storage conditions prior to their use in a clinical setting.

RESULTS

Here, we evaluated the thermal stability of AAV6.2FF, a rationally engineered capsid with strong tropism for lung and muscle, in two different buffer formulations; phosphate buffered saline (PBS), or PBS supplemented with 0.001% non-ionic surfactant Pluronic F68 (PF-68). Aliquots of AAV6.2FF vector encoding the firefly luciferase reporter gene (AAV6.2FF-ffLuc) were incubated at temperatures ranging from -20°C to 55°C for varying periods of time and the impact on infectivity and particle integrity evaluated. Additionally, the impact of several rounds of freeze-thaw treatments on the infectivity of AAV6.2FF was investigated. Vector infectivity was measured by quantifying firefly luciferase expression in HEK 293 cells and AAV particle integrity was measured by qPCR quantification of encapsidated viral DNA.

CONCLUSIONS

Our data demonstrate that formulating AAV6.2FF in PBS containing 0.001% PF-68 leads to increased stability and particle integrity at temperatures between -20℃ to 21℃ and protection against the destructive effects of freeze-thaw. Finally, AAV6.2FF-GFP formulated in PBS supplemented with 0.001% PF-68 displayed higher transduction efficiency in vivo in murine lung epithelial cells following intranasal administration than vector buffered in PBS alone further demonstrating the beneficial properties of PF-68.

Fast and efficient size exclusion chromatography of adeno associated viral vectors with 2.5 micrometer particle low adsorption columns

More and more transformative gene therapies (GTx) are reaching commercialization stage and many of them use Adeno Associated Viruses (AAVs) as their vector. Being larger than therapeutic antibodies, their size variant analysis poses an analytical challenge that must be addressed to speed up the development processes. Size exclusion chromatography (SEC) can provide critical information on the quality and purity of the product, but its full potential is not yet utilized by currently applied columns that are (i) packed with relatively large particles, (ii) prepared exclusively in large formats and (iii) built using metal hardware that is prone to secondary interactions. In this paper, we investigate the use of state-of-the-art sub-3 µm particles to address existing limitations. A prototype 2.5 µm column was found to deliver superior kinetic efficiency, significant reduction in run times and increased resolution of separations. No evidence for shear or sample sieving effects were found during comparisons with conventional 5 µm columns. Moreover, use of low adsorption hardware enabled the application of a wide range of mobile phase conditions and a chance to apply a more robust platform method for several AAV serotypes. The resulting method was tested for its reproducibility as well as utility for critical quality attribute assays, including multiangle light scattering based (MALS) measurements of size and molar mass. Thus, a new tool for higher resolution, higher throughput size variant analysis of AAVs has been described.

The ice age - A review on formulation of Adeno-associated virus therapeutics

Gene therapies offer promising therapeutic alternatives for many disorders that currently lack efficient treatment options. Due to their chemical nature and physico-chemical properties, delivery of polynucleic acids into target cells and subcellular compartments remains a significant challenge. Adeno-associated viruses (AAV) have gained a lot of interest for the efficient delivery of therapeutic single-stranded DNA (ssDNA) genomes over the past decades. More than a hundred products have been tested in clinical settings and three products have received market authorization by the US FDA in recent years. A lot of effort is being made to generate potent recombinant AAV (rAAV) vectors that show favorable safety and immunogenicity profiles for either local or systemic administration. Manufacturing processes are gradually being optimized to deliver a consistently high product quality and to serve potential market needs beyond rare indications. In contrast to protein therapeutics, most rAAV products are still supplied as frozen liquids within rather simple formulation buffers to enable sufficient product shelf life, significantly hampering global distribution and access. In this review, we aim to outline the hurdles of rAAV drug product development and discuss critical formulation and composition aspects of rAAV products under clinical evaluation. Further, we highlight recent development efforts in order to achieve stable liquid or lyophilized products. This review therefore provides a comprehensive overview on current state-of-the-art rAAV formulations and can further serve as a map for rational formulation development activities in the future.

Characterization of Virus Particles and Submicron-Sized Particulate Impurities in Recombinant Adeno-Associated Virus Drug Product

Characterization of particulate impurities such as aggregates is necessary to develop safe and efficacious adeno-associated virus (AAV) drug products. Although aggregation of AAVs can reduce the bioavailability of the virus, only a limited number of studies focus on the analysis of aggregates. We explored three technologies for their capability to characterize AAV monomers and aggregates in the submicron (<1 µm) size range: (i) mass photometry (MP), (ii) asymmetric flow field flow fractionation coupled to a UV-detector (AF4-UV/Vis) and (iii) microfluidic resistive pulse sensing (MRPS). Although low counts for aggregates impeded a quantitative analysis, MP was affirmed as an accurate and rapid method for quantifying the genome content of empty/filled/double-filled capsids, consistent with sedimentation velocity analytical ultracentrifugation results. MRPS and AF4-UV/Vis enabled the detection and quantification of aggregate content. The developed AF4-UV/Vis method separated AAV monomers from smaller aggregates, thereby enabling a quantification of aggregates <200 nm. MRPS was experienced as a straightforward method to determine the particle concentration and size distribution between 250-2000 nm, provided that the samples do not block the microfluidic cartridge. Overall, within this study we explored the benefits and limitations of the complementary technologies for assessing aggregate content in AAV samples.

Optimized formulation buffer preserves adeno-associated virus-9 infectivity after 4 °C storage and freeze/thawing cycling

Adeno-associated virus (AAV) have long been one of the most common and versatile vectors for in vitro and in vivo gene transfer. AAV production protocols are complex and time consuming, one key concern is the recovery and infectivity of viral vector after purification. The buffer used in the storage of AAV at 4 °C and - 80 °C is a crucial factor and methods to improve it have been thoroughly investigated. Viral core facilities have developed formulas using either 0.001% Pluronic F68 or 5% sorbitol in their storage buffers based on the results of this research. Interestingly, few use formulations that include both a non-ionic surfactant and cryopreservative. In this study, AAV9 stored at 4 °C and at - 80 °C in the standard buffers is compared to a buffer that contains 5% glycerol and 0.001% Pluronic F68. By viral genome quantitation with qPCR, all three formulations show the same extent of viral titer loss at 4 °C, while after several cycles of freeze/thaws at - 80 °C, the viral recovery and infectivity in the preparation with both glycerol and Pluronic F68 was most stable compared to the other buffers.