DNAtrix founders Drs. Juan Fueyo and David Curiel designed and patented DNX-2401, a novel adenovirus that fulfilled the dual requirements of higher potency with excellent safety. To do this, the scientists engineered two stable genetic changes in the adenovirus dsDNA genome that cause it to (1) replicate selectively in retinoblastoma (Rb)-pathway deficient cells and (2) infect cells that express certain RGD-binding integrins more efficiently. Because virtually all tumor cells, including GB, are defective in Rb function and already in the cell cycle, DNX-2401 replicates in and kills these tumor cells selectively and efficiently. DNX-2401 is vastly superior to wild type adenovirus with respect to killing rapidly growing tumor cells, an unprecedented property for an oncolytic virus.
While DNX-2401 should be effective against multiple tumor types, we are initially focused on high-grade gliomas for three reasons: (1) these tumors remain confined to the brain, so patient assessment is not complicated by the presence of metastatic disease, (2) tumor responses can be accurately documented and presented to the FDA to support product approval, and (3), the path to regulatory approval has already been established for high-grade gliomas.
Adenovirus entry into host cells is mediated by an initial binding step to its primary receptor, the coxsackie-adenovirus receptor (CAR). The particle is then internalized through interaction of the viral penton base protein with cellular αVβ3 or αVβ5 integrins on the cells surface (RGD- binding integrins). However, it is now known that CAR expression is often low on cancer cells, thereby limiting the effectiveness of adenovirus for treating cancer. To improve infectivity, an integrin binding peptide was introduced into the H1 loop of the adenovirus fiber. This RGD-4C peptide (CDCRGDCFC) has been shown to bind with high affinity to the RGD-binding (αVβ3 and αVβ5) integrins present on the surface of many cell types, including tumor cells.
Importantly, RGD-binding integrins have been shown to be expressed in tumor vasculature and on glioma cells but not in normal brain, thereby providing a basis for greatly increased and selective infection of GB by DNX-2401.