Antisense Oligonucleotides – enhance your preclinical development.

Immuneed’s Director of Business Science, Wing Cheng, has a solid background in recommending and evaluating antisense oligonucleotides (ASO) drugs from a nonclinical and clinical perspective at regulatory and market access agencies, including the European Medicines Agency (EMA). In this interview, he shares his knowledge in the ASO field and resonates around nonclinical approaches and ASOs’ inherent value for treating genetic and rare diseases.

What exactly are antisense oligonucleotides and how do they function?

Antisense oligonucleotides (ASOs) are short DNA or RNA sequences designed to target specific messenger RNA (mRNA) molecules within cells. They work by binding to complementary mRNA sequences and interfering with their normal function, thereby preventing their translation into protein. This can selectively inhibit disease-causing gene expression or enhance therapeutic gene expression, offering a promising approach for treating genetic disorders and other diseases. 

What distinguishes ASOs from other types of therapeutic agents?

Due to ASOs small size and uncomplicated mechanism, which works like building blocks, producing ASOs is relatively easy compared to, for example, antibodies that require certain organisms for production. ASOs are synthesized chemically and can be built from scratch, allowing for more scalable and less expensive production They consist of small DNA or RNA molecules that are highly specific in their interactions, reducing off-target effects and associated costs. Also, their high potency often requires a lower therapeutic dose.  

Which applications are there for ASOs?

These molecules have a range of applications in medicine, including treating genetic disorders and cancer. One key application of ASOs is in the treatment of genetic disorders, where they can target and selectively inhibit the expression of disease-causing genes. This offers a potential therapeutic approach for conditions such as Huntington’s disease, Duchenne muscular dystrophy, and spinal muscular atrophy. Here, ASOs have the potential to alleviate symptoms and improve patient outcomes. 

Additionally, ASOs are being investigated for their potential in cancer treatment. By targeting genes involved in tumor growth and progression, ASOs can inhibit the expression of oncogenes or enhance the expression of tumor-suppressor genes, offering a targeted approach to cancer treatment. ASOs may also be used in combination with other cancer therapies, such as chemotherapy or immunotherapy, to enhance their efficacy and reduce side effects. 

What are the challenges and limitations associated with the use of ASOs?

One limitation of RNA-based therapeutics, including ASOs, is the need for protection once they enter the body. This is because the body’s defense mechanisms recognize foreign RNA molecules as potential threats and may initiate an inflammatory response, leading to a reduction in platelet numbers. Despite efforts to protect these therapeutics once introduced, they can still elicit a strong immune response, posing a challenge to their clinical use. In nonclinical studies, it’s important to evaluate the complement system response because that is a central mechanism for eradicating these types of molecules. 

What recent advancements or breakthroughs have been made in ASO research?

Recent advancements have focused on improving the efficacy, delivery, and safety profiles of the ASOs.  

-Delivery Systems: lipid nanoparticles, conjugates with targeting ligands, or viral vectors, allowing for more efficient and precise delivery to target sites. 

-Chemical Modifications: Certain parts of the RNA molecules have been modified to create more stable and potent molecules with improved pharmacokinetic properties. These modifications help increase the stability of ASOs, improve cellular uptake, and reduce immunogenicity/toxicity. 

-Tissue-specific targeting: enables precise modulation of gene expression in specific tissues or cell types. This approach minimizes off-target effects and maximizes the therapeutic efficacy of ASO-based therapies while reducing systemic toxicity. 

-Target identification & validation:  utilizing genomic data and computational methods to identify disease-causing genes and validate their potential as targets for ASO-mediated modulation. 

How do ASOs contribute to personalized medicine and targeted therapies?

ASOs can be customized to target specific genes or genetic mutations, allowing for precise modulation of gene expression. This makes them ideal for addressing the underlying causes of genetic disorders. Overall, ASOs play a crucial role in advancing personalized medicine and targeted therapies by providing tailored treatment options based on individual genetic characteristics, ultimately leading to more effective and personalized patient care. In addition, ASOs are much easier to produce compared to cell therapy.  

Are there specific challenges in preclinical development when it comes to understanding how ASOs might impact the human immune system and evaluating toxicity?

The current nonclinical models used don’t translate well to studying genetic diseases, so having access to human biological materials is crucial to gathering accurate data on how these molecules behave. Regulatory agencies are finding it difficult to provide preclinical guidance for oligonucleotides, leading manufacturers to create their own evidence packages. Whole blood assays play an important role, providing a comprehensive understanding of how different systems interact. This model offers a level of safety and accuracy that other systems cannot compete with. As there are currently no official guidelines from regulatory agencies, drug developers need to gather various evidence.  

What is the current status of ASOs in terms of clinical trials and regulatory approval?

As of 2023, 19 oligonucleotide therapies have been approved by EMA or FDA, and this number is increasing. The number of clinical trials for ASOs is almost as high as for antibodies, indicating that big pharma is realizing that ASOs are promising candidates for treating various diseases. The use of RNA or DNA-based drugs is expected to continue increasing in the future. 

Do  you have any final recommendations for drug developers developing ASOs in the nonclinical stage; what should they think of when choosing assays?

It’s very important to have a good dialogue with the regulatory agencies and to be firm in your thinking. From my view as an ex-regulator, methods using human cells and tissue, particularly in these kinds of cases, will be attractive to use to prove safety before an IND filing. Moreover, benchmarking your ASO against clinically approved reference compounds such as inotersen and imetelstat will be essential in your weight of evidence.