Optimising Optimer Delivery Vehicles for Targeted Precision Therapies

Many diseases arise from mutations or imbalances in protein expression and can be corrected through changes to the gene transcript with RNA therapies.

RNA-based therapies modify disease pathways in the body by reinterpreting DNA’s instructions. They alter function by interfering with the expressed genes in a cell by silencing expression, increasing expression or changing the expressed form through gene splicing.

RNA-based therapies can potentially target any gene of interest as long as the exact sequence on the target RNA has been identified and there is an established method for delivering the RNA to the right place in the body – which is where is where the trouble starts.

The delivery challenge

Targeted delivery remains a major translational challenge for RNA therapies, with three major hurdles:

1. Targeting to the specific cell type

2. Allowing the RNA therapy to penetrate the target cell

3. Ensuring the therapy is functional once in the cell

Development of Optimer non-viral vectors can include stages to help overcome each of these hurdles.

Tuning Optimer delivery vehicles

The discovery and development process for Optimer delivery vehicles is tailored for precision targeting, affinity, cell internalisation, functionality in blood, half-life and conjugation to RNA therapies to enable intracellular functionality.

Hit the target or the phenotype

For development of Optimer delivery vehicles we can take two approaches.

If a specific receptor is known, we can develop Optimer delivery vehicles to that receptor initially using protein discovery and then continuing the discovery process using cells expressing the protein to ensure the delivery vehicle binds to the receptor in its cell-expressed form. These selection processes include the target of interest and counter-targets to remove cross-reactivity. This is all performed in a specific matrix e.g. plasma to remove any cross-reactive binding within the plasma.

If a receptor is not known or you would like to explore novel biomarkers, it is possible to perform discovery for specific phenotypes. Screening against e.g. healthy vs disease or different cell types we are able to discover Optimer delivery vehicles that are specific to the required cell type e.g. cancer vs healthy. The specific receptor that the Optimer delivery vehicle binds can then be identified following discovery.

Ensuring internalisation

Internalisation is built into the Optimer discovery process. During discovery Optimer delivery vehicles are discovered for the ability to selectively bind the target receptor as a protein and on the cell surface, whilst also ensuring internalisation to target cells with Optimer delivery vehicles that don’t internalise removed from the discovery process.

Optimer internalisation into target cell types can be optimised for cell-specific internalisation of the vector, specific timeframes of internalisation to allow rapid uptake or slower uptake, and also for the internalisation of the entire Optimer-RNA conjugate, making sure the therapeutic is internalised along with the non-viral vector unit.

Vector stability and half-life

Optimer delivery vehicles can be tuned for flexibility in in vivo stability and half-life according to different therapeutic strategies.

Stability can be tuned to allow degradation once the therapy has reached its site of action and achieved therapeutic effect. Incorporation of 2’-fluoro or 2’ O-Methyl groups in the Optimer backbone reduce endonuclease degradation, while capping of termini or circularisation of the Optimer delivery vehicles reduce exonuclease degradation. These modifications can be scaled to optimise stability.

To alter circulating half-life Optimer delivery vehicles can be fitted with a half-life extension module, that can extend half-life for longer residency times. On the other hand, for rapid hit-and-run strategies the small size of the Optimer alone allows for renal filtration, removing the Optimer-RNA from the body, which can cut off-target effects.

Balancing affinity for tissue penetration

Affinity requirements for Optimer delivery vehicles depend on the target receptor expression in specific tissues.

For highly expressed receptors, delivery vehicles with an intermediate affinity have been shown to improve tissue penetration and stop the conjugate forming a halo on the outside of tissues, particularly such as in the case of solid tumours. Whereas, for receptors with low expression delivery vehicles with high affinity are required to be to effectively locate the receptor in the tissue.

The small size of Optimer vectors (10th-15th of standard antibody) also supports improved tissue penetration.

Escape from the endosome

Optimer delivery vehicles ?are compatible with both cleavable and non-cleavable linkers, and can be conjugated using diverse site-directed chemistries. Using different linkers in Optimer-RNA conjugates enables different strategies for therapeutic release and testing of multiple linkers can easily be incorporated into Optimer development processes.

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Activity and interest in RNA-based therapies continue to expand, though targeted delivery remains a significant challenge to their effective use. Optimer non-viral vectors can be tuned according to the disease and drug requirements to deliver increased on-target and reduced off-target effects. For more information get in touch at [email protected].