Pre-Clinical Developments (STR-325)

Regular use of contact lens without proper hygienic maintenance can lead to multiple pathologies of the eye, including microbial keratitis. Current commercial multipurpose disinfection solutions (MPDS) for contact lens are developed for regular cleaning and antimicrobial disinfection to minimize the risks of potential adverse reactions associated with contact lens wear.

A properly formulated MPDS ideally combines antimicrobial disinfection without inducing ocular cytotoxicity. Our novel formulation MPDS (STR-325) was specifically developed to be broadly effective against multiple microbial pathogens by inclusion of multiple chemical stressors rather than a single disinfection agent while simultaneously exerting minimal cytotoxicity upon tissues upon contact. Relative antimicrobial disinfection and cytotoxicity using ISO testing protocols 14729 (antimicrobial) and 10993 (cytotoxicity) was performed using STR-325 in conjunction with three commercially available MPDS as comparators.  ISO-required battery of microorganisms (S. aureus, P. aeruginosa, S. marcesens, C. albicans, and F. solani) with contact times of 1 and 4 hours were used to assess disinfection potential of each. Vero76 monkey kidney cells and XTT proliferation assay were used to assess in vitro cytotoxicity of each MPDS. The disinfection potential of STR-325 in the ISO-specific antimicrobial assay demonstrated no bacterial/fungal plate growth for any of the microorganisms tested as early as 1h contact time. All comparator MPDS, in contrast, showed significant growth at 1 hour contact times, with only slight reductions of bacterial or fungal growth after the maximum contact time (4 hr) attempted. The results of the cytotoxicity assays showed two of the three comparator MPDS exceeded 90% cell death at 25%, and required a 12% solution concentration dilution in order to minimize cytotoxicity from contact; STR-325 showed minimal cell death at approximately the same dilutions as comparator solutions.

The newly formulated MPDS STR-325 combines broad-spectrum antimicrobial killing against an array of microorganisms while maintaining minimal cytotoxicity on target tissues as demonstrated in vitro. The performance of STR-325 in the two ISO-recommended standard assays exceeded the three commercially available comparator MPDS in antimicrobial activity, yet maintained a similar cytotoxicity profile. Future development of STR-325 for maintaining hygiene of contact lens wearers may further reduce unwanted toxic effects and ocular infections from inadvertent microbial contamination.