Patrys Limited announced results from a recently completed pre-clinical study that validates the potential to use its full size IgG deoxymab, PAT-DX3, for synthetic lethality strategies to treat relevant cancers. Patrys' deoxymabs have a number of novel properties that are not typically found in antibodies and that offer the potential to develop new antibody-based therapeutic strategies for treating cancer. One of these is the ability to enter the cell and cell nucleus and block the DNA Damage Response (DDR) systems. In tumours with pre-existing mutations that compromise their DDR systems, such as cancers with a mutation in the BRCA2 gene, the additional inhibition from adding a deoxymab may result in the accumulation of DNA damage that can ultimately kill the tumour cells.

This approach is known as `synthetic lethality' and has been successfully used in certain tumours with several new small molecule cancer drugs. In a pre-clinical colon cancer study in mice treated with PAT-DX3, tumours with a compromised DDR system showed a 71% reduction in growth, significantly more than the 35% reduction in growth in tumours with an intact DDR mechanism. This difference in response rate is further evidence of a synthetic lethality mode of action for Patrys' deoxymabs- a first for therapeutic antibodies.

An additional component of this study evaluated the accumulation of DNA breaks in tumour cells. This confirmed that all tumours in animals treated with PAT-DX3 showed an accumulation of DNA damage, and that the level of DNA damage was significantly higher in DDR deficient tumours.