PackGene’s Advanced Capabilities in AAV Gene Therapy for Rare Diseases

Observed annually on the last day of February—most recently on February 28, 2026—Rare Disease Day serves as a vital global platform to raise awareness for the more than 300 million people worldwide living with over 7,000 identified conditions. While these diseases are individually rare, they are collectively common, with a large fraction caused by single-gene defects that are often genetic, progressive, and life-altering. For most of these patients, conventional pharmacologic approaches and traditional protein replacements have offered limited or no disease-modifying options, frequently failing to reach all affected tissues or proving impractical for long-term care.

To address these unmet needs, adeno-associated virus (AAV) vectors have emerged as a premier solution for monogenic rare diseases. AAVs are uniquely suited for these conditions because they can provide sustained expression of a corrective gene from a single administration, particularly in non-dividing tissues such as the retina, liver, muscle, and central nervous system. Driven by a powerful combination of orphan-drug incentives, genomic breakthroughs, and dedicated patient advocacy, the AAV pipeline continues to expand rapidly, successfully transitioning transformative programs from initial animal models to late-stage clinical trials and regulatory approvals.

Recently approved AAV therapies

A survey cataloged 13 licensed viral gene therapy products worldwide and more than 200 clinical studies, including 137 active AAV trials across ocular, neurologic, metabolic, hematologic, and musculoskeletal conditions (1). Since that time, a large wave of new clinical programs has entered early-stage testing, while regulators have cleared additional AAV-based drugs for hemophilia, Duchenne muscular dystrophy (DMD), and aromatic L-amino acid decarboxylase (AADC) deficiency.

As of late 2024–2025, the FDA has licensed multiple AAV vector-based gene therapies across at least six distinct disease areas: inherited retinal dystrophy (RPE65), spinal muscular atrophy (SMA), hemophilia A, hemophilia B, DMD, and AADC deficiency. Notably, some areas now benefit from more than one approved AAV product, such as hemophilia B and SMA (2). Collectively, these approvals demonstrate the clinical feasibility of one-time in vivo AAV administration; however, because durability and long-term benefits vary by indication, these therapies require ongoing follow-up and rigorous safety monitoring.

Table 1. Recent approved AAV gene therapies.

Hemophilia Therapies

Roctavian (valoctocogene roxaparvovec) from BioMarin treats hemophilia A, marked by low factor VIII. It gained EMA approval in 2022 and FDA in 2023 as the first for this disorder. Using AAV5, it carries a working F8 gene for factor VIII to the liver, where cells make the protein. Long-term factor VIII levels are tracked, with 2024 data from Phase II/III showing benefits lasting years, cutting need for regular infusions.

Hemgenix (etranacogene dezaparvovec) by CSL Behring addresses hemophilia B’s factor IX shortage. FDA-approved in 2022, it’s the initial for this type. AAV5 delivers a boosted FIX gene (Padua variant) with higher activity. Phase III results showed steady FIX at 15-60% normal, slashing bleed rates by 90%.

Beqvez (fidanacogene elaparvovec) from Pfizer and Sangamo also targets hemophilia B. Approved by FDA in 2024 via Phase III BENEGENE-2, it aims for ongoing FIX to lessen bleeds and infusions. Well-tolerated with no major issues. It uses AAVrh74var capsid for liver cells, delivering Padua FIX. But in 2025, Pfizer halted global work on Beqvez due to low uptake, partly from the $3.5 million cost for similar therapies.

Duchenne Muscular Dystrophy Therapy

Elevidys (delandistrogene moxeparvovec) by Sarepta treats DMD, caused by DMD gene flaws affecting dystrophin for muscle support. FDA-approved in 2023 via accelerated path, it’s DMD’s first gene fix. It provides a shortened micro-dystrophin gene in AAVrh74, which favors muscle tissues, given via IV. Biopsies confirm strong expression and some function gains. After three non-walking patient deaths, FDA paused for all in July 2025 but resumed for walkers. By August 2025, updates added warnings for liver risks.

AADC Deficiency Therapy

Kebilidi (eladocagene exuparvovec-tneq) handles AADC deficiency, a rare DDC gene issue impairing neurotransmitter production like dopamine/serotonin. FDA-approved in November 2024, it’s the first brain-direct gene therapy. It inserts working DDC into the putamen for motor control, boosting enzyme to restore dopamine and improve movement.

Disease areas where AAV is most active

Central nervous system disorders

Neurologic disease has become one of the most intensively targeted categories for AAV gene therapy. Many CNS disorders share three attractive features for this modality: they are often driven by a single gene defect, are relentlessly progressive, and currently lack curative options.

AAV9 dominates systemic and broad CNS delivery because it can transduce neurons and glia widely after intravenous injection, especially when administered early in life. The success of Zolgensma in SMA has validated this concept and encouraged programs in ALS, Rett syndrome, and various monogenic epilepsies. At the same time, routes such as intrathecal and intracisternal injection, as well as direct intra‑brain parenchymal delivery (as in Kebilidi), are being explored to boost on‑target expression while potentially lowering total dose and systemic exposure.

Ocular indications

The eye remains a showcase organ for AAV. Its small volume and relative immune privilege permit local dosing at modest vector copy numbers, limiting systemic risks. AAV2, and capsids closely related to it, continue to be the mainstay for subretinal and intravitreal delivery in inherited retinal diseases like Leber congenital amaurosis, retinitis pigmentosa, and X‑linked retinoschisis.

Luxturna’s clinical performance in RPE65‑mediated Leber congenital amaurosis—sustained improvements in functional vision measures following a single subretinal injection—has set a benchmark that newer programs strive to match or exceed. Current investigational work includes novel capsids optimized for intravitreal delivery, the use of different promoters to target specific retinal cell types, and dual‑vector strategies aimed at genes too large to fit into a single AAV genome.

Metabolic liver diseases

Inborn errors of metabolism are a natural fit for liver‑directed AAV therapy because many disease‑causing enzymes are normally produced in hepatocytes, and relatively modest levels of restored activity can be clinically meaningful. Ongoing trials are exploring AAV therapy for glycogen storage diseases, urea cycle disorders such as ornithine transcarbamylase deficiency, and disorders like phenylketonuria.

AAV8, and increasingly AAV9, are favored capsids here thanks to their strong liver tropism and ability to drive long‑term expression in largely non‑dividing hepatocytes. The main challenges are balancing sufficient dose for therapeutic benefit against the risks of acute liver toxicity and immune‑mediated responses, especially in adults with pre‑existing liver conditions.

Hematologic conditions

Coagulation disorders illustrate how AAV can be used to convert a severe lifelong disease into a more manageable condition. In hemophilia A and B, liver‑directed AAV5 or AAV8 vectors carrying F8 or F9 transgenes enable continuous endogenous production of clotting factors. Clinical data from both Roctavian and Hemgenix show that a sizable proportion of treated patients can transition off prophylactic factor replacement and experience far fewer spontaneous bleeds.

Beyond classical hemophilia, AAV strategies are beginning to be applied to rarer clotting factor deficiencies and complement pathway disorders, again using the liver as a biofactory for systemically secreted proteins. Inter‑patient variability in expression and uncertainties about expression half‑life remain important considerations that are being addressed by long‑term follow‑up and by refinements in promoter choice and vector design.

Capsids, genome design, and platform specialization

Serotype use across indications

When one tallies the serotypes used in current AAV trials, a pattern emerges: AAV9 is now the workhorse for systemic and CNS‑oriented applications; AAV8 and AAV5 are dominant for hepatic delivery; and AAV2 remains the default choice for ocular and certain localized CNS routes. Alongside these classical serotypes is a growing cohort of proprietary or unspecified engineered capsids, often referred to only by internal designations.

Disease area strongly shapes capsid selection. Neurologic programs lean heavily on AAV9 and engineered neurotropic capsids, while eye programs still revolve around AAV2‑like vectors. Hematology and metabolic liver programs frequently use AAV5 or AAV8, where there is substantial human experience and robust liver transduction. Muscle‑targeted therapies, such as Elevidys, make use of capsids like AAVrh74 that show strong affinity for striated muscle.

Engineered capsids and computational design

Natural serotypes have important limitations, including susceptibility to pre‑existing neutralizing antibodies and suboptimal tissue selectivity. To address this, multiple groups are now applying directed evolution, deep mutational scanning, and machine‑learning‑assisted design to create new AAV variants.

These engineered capsids are evaluated in high‑throughput in vivo screens for properties such as enhanced CNS penetration, reduced liver capture, or restricted tropism to particular cell types. Machine learning models, trained on large sequence–function datasets, increasingly guide which mutations to combine to yield multi‑trait optimization (for example, combining high AAV packaging efficiency with low immunogenicity). Some of these new capsids have already entered human trials, although many are still described only generically in public registries.

Genome architecture and transcriptional control

Parallel innovation is happening at the level of the vector genome. Self‑complementary AAV designs are used where rapid onset of expression is critical, accepting the trade‑off in payload size. Enhancer–promoter combinations are chosen to boost expression in the intended cell type while minimizing leakiness elsewhere. Insulator sequences and removal of bacterial backbone components reduce the risk of unwanted activation of host genes.

More sophisticated regulatory designs employ microRNA target sites to silence transgene expression in off‑target lineages, such as antigen‑presenting cells, thereby dampening immune activation without sacrificing expression in therapeutic target cells. Other approaches incorporate logic‑gate‑like promoter systems or drug‑inducible switches to provide external control over transgene expression.

How PackGene empowers rare AAV gene therapy programs to succeed

1.Addressing Cost and Scalability Challenges with PackGene Innovations

The production of AAV vectors plays a crucial role in determining how widely gene therapies can be adopted and brought to market. In cases of extremely rare disorders, where the number of affected individuals is minimal, the expense of limited-scale manufacturing might be acceptable, yet the narrow market potential poses serious hurdles to viable commercialization. Absent strong economic motivations, biotech firms might hesitate to commit resources to these areas. To broaden the reach of gene therapy to widespread conditions, major reductions in expenses are essential, calling for advancements in production yields, operational streamlining, and uniform protocols. In light of these obstacles, PackGene’s developments in AAV technology are focused on boosting affordability and expanding capacity.

1a. The π-Alpha 293 Platform for High-Yield AAV Production from PackGene

PackGene’s proprietary AAV manufacturing system boosts output levels through an exclusive cell line we’ve engineered. It incorporates a unique Rep/Cap (RC) plasmid that amplifies yields by a factor of 3 to 8 for different AAV variants. Additional refinements, based on Quality by Design (QbD) methodologies across both initial cultivation and purification stages, can push improvements to a 10x level. This capability allows for batches yielding up to 1E+17 vector genomes, sufficient to handle the rigorous needs of both trial phases and full-scale production, effectively tackling core limitations in advancing AAV treatments. Moreover, the system minimizes contaminants and boosts the proportion of full capsids, enhancing overall safety and potency. As illustrated in Figure 1, PackGene’s advanced RC plasmid markedly elevates AAV yields while maintaining an excellent full-to-empty capsid balance.

Figure 1. a. Enhanced AAV yields driven by PackGene’s innovative RC plasmid in various serotypes under adherent conditions. b. Boosted production for AAV8 and AAV9 using the RC plasmid in suspension setups. c. Post-purification full capsid percentages ranging from 76% to 96% via anion exchange methods.

Link: π-Alpha 293 AAV High-yield Production Platform | PackGene Biotech

1b. PackGene’s π-Omega System for Elevated Plasmid DNA Yields

Our exclusive platform refines plasmid structures through targeted backbone adjustments, achieving over a threefold surge in output. This upgrade streamlines subsequent steps by alleviating shortages in plasmid supply. The system’s expandable nature supports runs up to 200 liters, with individual batches delivering as much as 100 grams of material. Such robust scaling makes it ideal for high-volume demands in fields like therapeutic vector creation and extensive scientific investigations.

Link: π-Omega Plasmid DNA High-yield Production Platform | PackGene Biotech

1c. The π-Icosa Platform for AAV Capsid Optimization from PackGene

This specialized system focuses on developing and evaluating modified AAV capsids with superior traits, including better organ selectivity, increased transduction rates, and lower unintended impacts, tailored for therapeutic gene delivery. It seeks to overcome drawbacks of standard AAV types, which may fall short in accuracy or performance for varied clinical scenarios. By combining logical engineering, evolutionary techniques, and rapid assessment methods, the platform crafts customized vectors, serving as a key resource for refining delivery in both experimental and medical contexts. Through its application, we’ve pinpointed the AAV-PG008 variant, which shows heightened expression in neural tissues (see Figure 2).

Figure 2. Compared to AAV9, AAV-PG008 yields stronger GFP signals in spinal and cortical regions.

Link: https://www.packgene.com/services/aav-services/aav-capsid-engineering/

2. PackGene’s Contributions to Rare Disease Therapies

PackGene is advancing efforts against uncommon disorders by leveraging its specialized manufacturing capabilities and key partnerships. We prioritize delivering economical production options for essential components like AAV, mRNA, plasmids, and lentiviral vectors. In addressing hearing impairment linked to OTOF mutations, PackGene supplied vital viral materials for the RRG-OTOF therapy, aiding its receipt of FDA Orphan Drug status. This strategy, using two vectors, targets restoration of hearing by introducing the otoferlin sequence into inner ear cells. For SPG56, a highly uncommon neural condition, PackGene collaborates with Genetic Cures for Kids and Weill Cornell Medicine to produce clinical-quality treatments, committing to cost support and faster timelines.

3. Conclusion:

PackGene is dedicated to enhancing the availability and cost-efficiency of gene therapies, especially for overlooked ultra-rare ailments in the broader drug development landscape. Through our specialized services in plasmid and vector production, we facilitate quicker progress in customized interventions for limited patient groups. We strive to assist therapy innovators, medical experts, advocacy organizations, and rare disease support networks in their collective battle against these challenges. Our initiatives underscore that combining top-tier research with empathy can extend advanced treatments to even the most isolated conditions, establishing a model that could transform care for numerous untreatable genetic issues.

Reference:

1. Park KS, et al. Viral vector-based gene therapies in the clinic: An update. Bioeng Transl Med. 2026;11(1):e70106.
2. Rieske A, et al. The new wave of gene and cell therapies across diseases. J Clin Med. 2026;15(4):1122.