Extracellular Vesicle Product Developer Creates Potency Assay

Developing potency assays for complex new biologics, such as extracellular vesicle (EV)-based products, can be a challenge, with some manufacturers putting it off until regulators ask hard questions. That’s the view of Evox Therapeutics, who say they’ve succeeded in developing a potency assay that can be hopefully adapted to multiple future products in their pipeline.

According to Rebecca Gavin, PhD, chemistry, manufacturing, and controls (CMC) director at Evox, the assay has already been pre-qualified and transferred into a quality control (QC) laboratory.

The company hopes it can be fully qualified during a planned first-in-human study next year and, in the future, be used for batch QC during commercial production of their products.

“Our product is quite complex, and that’s why people often struggle to develop a potency assay,” Gavin says.

“Sometimes CMC can get kicked down the road a little, with people thinking they’ll worry about it later when they have more funding, so [the fact] that we’ve developed one already is something we’re really proud of.”

Evox’s product encapsulates a ribonucleoprotein (RNP) within an EV that is used as the delivery mechanism. The RNP is coupled to a guide RNA, which targets a specific gene with the aim of reducing protein production, Gavin explains.

Although this could spur lots of complex questions, such as whether the EV is taken up by the cell and whether the editing machinery makes it to the nucleus, she says that this can lead to over-characterization and over-testing.

“You don’t want to have a batch release assay panel that’s 50 assays long, where you’re having to measure and quantify every aspect of a complex product, and need to dedicate 50% of your batch to testing, especially in the gene therapy field where batch yields are already tricky,” she explains.

To get around this, the company developed an assay that simply measures potency, thereby demonstrating that the product is being successfully assembled and delivered to a cell.

The assay doses EV products at different concentrations onto an immortalized adherent cell line, she says. The cells are allowed to grow for a while, and then the cell lysates are tested on a Jess Simple Western system.

“We get a very specific quantitative readout, and that allows us to determine a dose-response curve, which shows how active our product is at reducing our protein of interest,” she explains.

Going forward, the company hopes this simple potency assay can be fully qualified for commercial production and adapted for multiple products in their pipeline.

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