Gene Therapy

Gene therapy, where a defective gene is replaced to restore normal gene function, holds great promise as a treatment for a wide range of diseases. However, early setbacks and unclear regulations meant that many pharma companies paused their development. In recent years, gene therapy has made a comeback and has finally begun to deliver on its potential with the release of several FDA-approved gene therapy treatments for a variety of disorders.

The rapid development in molecular biology over the last few decades has revolutionized how we think of disease. A wide range of disorders have been found to have a genetic basis, and many of the underlying gene mutations have been identified.

Gene therapy holds great promise as an effective treatment for these diseases. Over the coming decades, gene therapy treatment of a wide range of disorders, such as inherited diseases, cancer, and viral infections, may be commonplace.

How it works

The principle of gene therapy is straightforward: deliver a functional gene to target cells in the patient to restore normal gene function. This is most commonly achieved using a recombinant Adeno-Associated Virus (AAV) vector where some of the viral genetic material has been replaced by a therapeutic cargo. Once the virus has infected the target cell, it uses the cell's molecular machinery to produce the therapeutic protein.

aav principle

Principle of AAV-mediated gene therapy. Recombinant AAV vectors carrying transgenes cross the cell membrane and deliver their cargo into the cell of the nucleus. Here, the transgenes persist in a circular episomal state. Following the transcription of the episome DNA, therapeutic protein is expressed in the cytoplasm of the cell. 


In gene therapy, recombinant AAV vectors which lack viral DNA are used. They have been engineered to cross the cell membrane and deliver their DNA cargo into the cell nucleus. The transgenes are flanked by inverted terminal repeats (ITRs) that allow them to form episomes in the nucleus of the cells. Since the episomes do not integrate into the cell genome and have no way of self-replicating, they will be diluted to a point where they are eventually lost over multiple rounds of cell replication.

The importance of immunogenicity testing

Since most gene therapy projects use a recombinant AAV vector, where some of the viral genome has been replaced by a therapeutic cargo, immunogenicity testing is essential. Patients previously infected by naturally occurring AAVs may carry neutralizing antibodies (NAbs) that prevent the gene therapy vector from transfecting the host cell and delivering its cargo.

This can eliminate the therapeutic effect and potentially lead to other more severe cases of unwanted immunogenicity effects.



Neutralizing antibodies (NAbs) can block AAVs from entering the cell. Patients who have been infected by naturally occurring AAVs in the past may have developed NAbs against the capsid, which may render the treatment ineffective.

The importance of accurately assessing Potency

As stipulated by regulatory guidelines, a potency assay for a gene therapy drug must reflect the MOA, demonstrating that the genetic transfer into the cell (transduction) and subsequent transcription and translation of the AAV genetic cargo has the desired biological effect.

By using cell-based potency assays for gene therapy, the goals of demonstrating the genetic transfer into the cell (transduction and that the AAV genetic cargo has the desired biological effect that can be achieved. This requires cell-based solutions, entirely tailored to the specific drug compound/genetic cargo, thus generating MOA-reflective assays where transgene functionally could be assessed.


Our unique custom-specific quantitative cell-based potency assay ensures a truly MOA-reflective process every step of the way: expression, protein modifications, proper localization of the protein product, and protein function. 

How we can help

We have extensive experience in gene therapy projects – from developing cell-based assays for immunogenicity and potency testing to providing a full service through our CRO Services.

Immunogenicity testing

We offer a unique assay-ready two-component system for measuring NAbs against AAV serotypes 2, 5, 6, 8, and 9, as well as custom capsids. A packaging cell line is used to generate AAVs, and an iLite® reporter-gene cell line expresses luciferase upon transduction of AAVs.

NAbs against the AAV vector will affect the level of luciferase expression. A second normalization gene can be used to detect matrix effects and enhance the accuracy of the assay.

Read about our products for immunogenicity testing


Potency testing

We can develop custom-made reporter gene cell lines for potency assays of a wide range of targets. Over the years, we have helped many customers with assays for complicated projects – including retinal gene therapy development.

Our unique cell-based iLite® technology is a powerful cell-based technology that is ideal for measuring and quantifying gene therapy targets. With our in-house expertise and processes, we have a high success rate and can create an iLite cell line for almost any biopharmaceutical target.

In addition to our custom-made cell lines, we also offer off-the-shelf products for many targets.

Read about our custom cell-based assays


CRO services

Our CRO Services offer assistance throughout your gene therapy drug development process. We can develop and validate assays, perform sample analysis, and provide a final report for regulatory approval.

Our CRO Services have long experience in creating assays for a wide range of projects and can help you create the optimal assay for your target.

The laboratory is GLP-compliant and operates according to GCP. Bioassay method development, transfers, and validations are available under GMP. This enables a fully integrated chain from assay development to a fully validated potency assay for drug batch release.

Read about our CRO Services


Contact us

Discuss your project with our gene therapy experts