Scavidin was used to target and concentrate intravenous doses of as little as one-tenth the conventional levels of the radioisotope Yttrium(90) in one model, and the chemotherapy drug paclitaxel in another, to tumors growing under the skin. The results indicate a wide utility for this technology in large markets.
Scavidin is a novel two-part drug targeting technology originating from the DNA that expresses the scavenger receptor on white blood cells. This natural receptor usually collects undesired fats and damaged cells and membranes from the blood, taking them into the white blood cells and releasing them for destruction as part of the body’s natural ‘clean up’ system. By modifying the DNA sequence for such receptor types, Ark has developed a new family of receptors which specifically bind only to the protein biotin, a naturally occurring substance which can easily be attached to therapeutic agents.
The Scavidin DNA is put into the tumor, where it expresses the new drug-targeting receptor. The therapeutic agent, pre-tagged with biotin, is then given intravenously at low doses. As the therapeutic agent circulates round the body, Scavidin extracts it from the blood by binding to the biotin tag, taking it into the cell and releasing it. The receptor then goes back and collects more.
This revolutionary ‘molecular shuttle’ system concentrates the therapeutic agent from a low and ineffective dose in the blood to a high therapeutic dose specifically in the target tissue. In this way, an important and highly effective therapeutic, which could have a poor safety profile at a traditional dose, may be given in a low and safe dose systemically, with Scavidin concentrating it specifically at the disease site.
In the cancer studies, each treatment eliminated tumor growth during the respective 7-10 day study periods with a clear treatment response quickly evident. Tumors in non-treated controls showed a three to five fold increase in size in the same period.
“These results indicate that Scavidin has the potential both to improve the therapeutic effect and to reduce the unpleasant side-effects of a wide variety of drugs, most obviously chemotherapy and other potent anticancer agents, but also in many other therapies where the side-effects are high and thus dose-limiting,” commented Nigel Parker, CEO of Ark.
Ark now plans to optimize the dosing regimes and explore efficacy in other cancer models.