Exopharm Limited announced positive data from an expert animal study conducted by an external group to assess immunogenicity and toxicity of Exopharm's exosomes. Validation of Exopharm's technology further progressed: As mentioned in the Company's Quarterly Activities Report, a batch of exosomes had been manufactured and characterised to support Exopharm's testing of naïve exosomes - a prerequisite for later human studies. As planned, an animal study to test LEAP purified exosomes for safety and immunogenicity has now completed dosing.

The interim study results show that repeated dosing of the exosomes was safe and did not generate an immune response despite up to 10 doses of around 3.4 billion particles per dose over 23 days. Exosomes as a drug-delivery `chassis' hold the prospect of being seen by the person's immune system as harmless and could be dosed many times (they have low immunogenicity). These study results lend support to this thesis.

The positive results back the use of exosomes made from Exopharm's producer-cells and purified by its patented LEAP purification process as a safe and well-tolerated alternative to viral vectors (adeno-associated virus [AAV]) and lipid nanoparticles [LNPs]. Using exosomes as a carrier of the active pharmaceutical ingredient (API) is core to Exopharm's present strategy. Showing that the exosome carrier is 'silent' to the recipient's immune system and non-toxic are important steps in that strategy.

The results from this study indicate that Exopharm's exosomes have these all-important attributes. Key details and outcomes of the study: HEK-293 cells were cultured by Exopharm to produce naïve (no engineering of the cells) exosomes. These exosomes were then purified using Exopharm's LEAP technology at its research centre.

At University of Queensland, around 3.4 billion particles in 100 millionths of a litre (100µL) liquid of solution were injected intravenous under anaesthetic into a cohort of healthy adult wild-type mice at each dosing. Other mice in the study received the same volume of a control substance PBS (phosphate-buffered saline). Another small cohort of mice were administered LPS (Lipopolysaccharide) systemically to create a positive control and for assay validation.

Dosing was over 23 days and there was a total of 10 doses per mouse. Preliminary data obtained included body and organ mass, gross necropsy, haematology, and spleen-cell immunophenotyping - all of which confirmed the absence of an immune response or detectable toxicity levels. The study was performed under ethics approval (University of Queensland Animal Ethics Committee (AE000938)) and animals were monitored for changes in behaviour and health.

In the context of this study, immunogenicity is the ability of the animal's immune system to detect and mount an adverse immune response against the foreign exosomes that were administered. For a drug-delivery technology for therapeutic products, the ideal outcome from such a test is that the exosomes are not subject to an adverse host immune response - which is the outcome seen in these preliminary results. The key conclusion from the preliminary data from this study is that the exosomes are not immunogenic or toxic and the product and the manufacturing process are suitable for clinical pursuit.

This study is a further important step towards the successful development of engineered exosome products.