Exopharm developing novel Plexaris product to deliver anti-cancer drug into target cells

Exopharm ASX EX1 Plexaris anti cancer drug doxorubicin Plexodox
Exopharm’s Plexodox product combined with existing drugs led to greater cancer cell death compared to the drug in isolation.

Clinical stage regenerative medicine company Exopharm (ASX: EX1) has published test results that suggest its Plexaris product, made up of engineered exosomes through “LEAP technology”, can effectively deliver therapeutic drugs into target cells.

Plexaris is already being tested in humans as part of the PLEXOVAL phase 1 trial for wound healing although its multifaceted applications are also being studied in treating cancer.

In February this year, Exopharm received amiable results from Eurofins’ BioMAP testing program indicating that its exosome platform is safe in its mechanism of action and has “different and distinct activities” compared to 4,500 other drugs.

In parallel to the test results published today, Exopharm also announced the launch of its engineered exosome (EEV) development and partnering program, aiming to leverage exosomes’ ability to deliver medicinal cargos to specific cells in various therapeutic applications.

According to a recent in-vitro study, Plexaris loaded with anticancer drug doxorubicin “killed considerably more cancer cells than a similar dosage of the drug by itself”, with Exopharm declaring that results demonstrated the broad potential of its platelet-derived approach, to be harnessed for its anti-cancer drug Plexodox.

Improving existing drugs

Currently, doxorubicin is widely used for in chemotherapy for the treatment of breast, and bladder cancer, lymphoma and acute lymphocytic leukaemia.

The drug was first approved for medical use in 1974 in the US and remains on the World Health Organisation’s list of essential medicines, reputed to be “the safest and most effective medicines needed in a health system”.

Doxorubicin drug sales worldwide exceed US$1 billion annually with the wholesale cost in the developing world currently standing at around US$4–33 per 50mg vial.

However, patients treated with doxorubicin often report severe side effects including myelosuppression, cardiotoxicity, alopecia, nausea and vomiting, which has forced regulators such as the FDA to cap dosage levels in an attempt to limit adverse patient response.

Exopharm is hopeful that its Plexodox product can both increase doxorubicin anti-cancer cell efficacy while reducing unwanted side-effects, thereby increasing the therapeutic window for patients and potentially improving clinical outcomes.

“Cancer tumours are sometimes referred to as internal wounds that never heal. Platelets are drawn to wound sites, so there is good reason to believe that Plexodox will preferentially deliver doxorubicin to tumours,” said Dr Andrew Coley, Head of Innovation at Exopharm.

A key factor that could influence the efficacy of Exopharm’s approach and ultimately decide whether Plexaris is effective, is drug formulation.

Doxorubicin is typically sold in what’s known as a “liposomal formulation” – a method of drug preparation that contains the active drug inside microscopic “fat-like” particles. In this altered form, it is easier for the body to absorb the drug and allows more of the drug to reach the target area of the body, such as a tumour.

Liposomal formulations also extend the drug’s post-administration half-life in circulation and reduce its cardiotoxicity.

Liposome drug-delivery nanoparticles are synthetic, which means they can be targeted by the immune system, triggering an adverse immune response, immunotoxicity and liposome clearance.

“Cancer patients are commonly transfused with platelets to counteract side-effects from chemotherapy already, so we know that allogeneic platelets are not only safe but therapeutic. Plexodox combines two treatments into one,” said Dr Chris Baldwin, chief commercial officer at Exopharm.

“Our approach is, rather than treat the patient for side effects, let’s use platelet EVs to get doxorubicin where it belongs: inside cancer cells,” he added.

The test results published by Exopharm are early stage with in-vitro results yet to be confirmed in animal models while the company confirmed that additional testing as part of a development program would be required before Plexodox would be proposed for human trials.

Exopharm shares were up by more than 30% up to $0.29 in morning trade.

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