Invion Limited announced the positive screening results from in vitro studies of PhotosoftTM on the inhibition of the Zika virus. The results from the in vitro studies, which were undertaken by leading contract research and clinical laboratory service company Viroclinics-DDL and Virology Research Services Ltd, showed selected PhotosoftTM compounds to be effective against the virus and more efficacious than Monensin. Monensin is an antibiotic which is known to have activity against Zika in vitro laboratory tests and was used as a control (benchmark) in this study, but due to its in vivo toxicity cannot be used in humans.

Zika virus is primarily transmitted by the Aedes Aegypti mosquito, which also transmits yellow fever and dengue. Symptoms associated with Zika include headache, skin rash and joint pain. Further, Zika has been linked to birth defects and other neurological complications.

Invion holds the exclusive rights to the PhotosoftTM technology in Asia Pacific3 for the treatment of infectious diseases and atherosclerosis through its agreement with the technology licensor, RMW Cho Group Limited. Selected PhotosoftTM compounds demonstrated potent (over 99% inhibition) antiviral activity against Zika when exposed to specific light wavelengths. In addition to the potent activity of several PhotosoftTM compounds, low levels of cytotoxicity were observed.

When assessed in combination, a resulting therapeutic index4 is calculated, which is a quantitative measurement of the potential efficacy relative to safety of the compound. Selected PhotosoftTM compounds were found to have a therapeutic index over 190 times higher than the control, Monensin. A recent report by CSIRO titled "Strengthening Australia's Pandemic Preparedness" identified the development of novel antivirals as a key science and technology area for strengthening Australia's pandemic preparedness.

In vitro susceptibility of viruses to an antiviral agent was assessed using a quantitative assay to measure virus replication in the presence of increasing concentrations of the product (PhotosoftTM compounds) and a control compound (Monensin) compared to replication in the absence of the product. The primary screening assay utilised in this compound screening program was an immunofluorescence-based assay against Zika Strain MP1751 (African lineage) obtained from the contracted organisation, using the Vero E6 cell line. Compounds were serially diluted (8 concentrations) in a 96-well plate and added to the cells.

Zika was then added, exposed to a specific light wavelength (660nm), and plates incubated for 48 hours . Additionally, compounds were assessed for cellular toxicity in Vero E6 cells. At the conclusion of incubation, infected cells were identified and counted via microscopy; lower percentages of stained cells compared to an untreated control represented cell protection from virus infection.

Half maximal effective concentration (EC50) and half maximal cytotoxic concentration (CC50) were calculated by linear regression.