ASO Therapies 2/3: How It Works At The Molecular Level

From Gene to Protein: The Normal Journey

To understand ASO therapy, you first need to grasp how our cells make proteins. It all starts in the nucleus with DNA, our permanent "recipe book." When a cell needs a protein, it doesn't read the DNA directly. It makes a temporary copy called messenger RNA (mRNA), like photocopying a recipe to take to the kitchen.

Between DNA and mRNA, splicing occurs: the cell cuts out the useless parts (introns) and keeps the useful parts (exons). It's like editing a video: keep the good scenes, remove the rest. Finally, the mRNA is translated into protein that does the actual work in the cell.

The Three ASO Strategies

🟣 Block Translation

The ASO binds to the mRNA and prevents it from being read.

Result: less or no protein produced. Useful when the mutated protein is toxic.

🟠 Modify Splicing

The ASO can mask or reveal specific sequences to change how exons are included or excluded. This produces a modified but partially functional protein.

Two approaches:

Exon skipping: Force exclusion of a problematic exon to create a shorter but functional protein

Duchenne example: Skip the mutated exon to produce shortened but usable dystrophin

Exon inclusion: Force inclusion of a beneficial exon that would normally be skipped

Spinraza example (SMA): Modify SMN2 gene splicing to include exon 7, producing more functional protein

🟢 Degrade mRNA

The ASO recruits an enzyme (RNase H) that completely destroys the mRNA. Radical approach to eliminate a toxic protein.

Technical Challenges

Delivery: ASOs must reach the right cells. For the brain, intrathecal injection directly into the cerebrospinal fluid.

Specificity: Risk of binding to other similar mRNAs. Researchers design very precise sequences and test extensively.

Duration of action: ASOs degrade over time. Spinraza requires injections every 4 months for life after the initial phase.

What's Needed to Design an ASO Therapy

The prerequisites:

🟢 Know the exact gene sequence

🔴 Understand the mechanism: gain or loss of function?

🔴 Identify relevant splicing sites

🔴 Have cellular and animal models for testing

🔴 Know which tissues are affected

What About LMBRD2?

What we have:

🟢 The gene sequence

What we're missing:

🔴 The function of LMBRD2 protein

🔴 The mechanism: gain or loss of function?

🔴 Reliable cellular/animal models

🔴 Understanding of affected tissues

Why this is blocking? Without knowing the mechanism, it's impossible to choose the right ASO strategy. Loss of function ≠ gain of function = completely different strategies.

Why we're not blocked forever: Modern technologies like RNA sequencing, CRISPR screens, and induced pluripotent stem cells (iPSCs) are accelerating our ability to answer these questions. The fundamental research phase that once took decades can now progress much faster.

Other Therapeutic Options

ASOs are just one tool among others:

🟣Gene therapy → Deliver a functional copy of the gene (for loss of function)

🟠Small molecules → Classic drugs, simpler administration

🔵CRISPR → Directly correct the mutation in DNA (still in development)

🟢Alternative therapies → If we understand what's missing, provide it differently

Conclusion

ASOs intercept messenger RNA to modify protein production. It's powerful, but requires precise understanding of the disease biology. For LMBRD2, fundamental research remains the priority: understanding gene function, mutation mechanisms, and affected tissues. Only then can we evaluate whether ASOs are the appropriate approach. This fundamental research isn't wasted time: it's the foundation on which any future treatment will be built.