Rationalisation of the purification, formulation and packaging of anti-Staphylococcus aureus therapeutic phage suspensions for human use

The resurgence of phage therapy must overcome historical challenges intrinsic to phage suspensions, amongst which the long-term preservation of therapeutic concentrations of purified phage suspensions. To secure and accelerate the downstream processing (purification, formulation) of therapeutic phages, various properties of phages - and impurities - are rationalised to optimise the purification process, formulation and packaging, ensuring these methods can be applied to multiple phages and are compatible with human use. In this regard, the physicochemical properties of phages are considered to optimise the separation of the virions from bacterial impurities. The proteinaceous and colloidal (particles of 1 nm to 1 µm dispersed in a continuous medium) nature of phages is factored in to design and understand the thermodynamic interactions that lead to phage degradation mechanisms. When applied to anti-Staphylococcus aureus phage suspensions, this approach enabled the successful purification of one podovirus and three myoviruses. In parallel, a suspension medium was also developed and tested on one of the myovirus. It preserved the infectious titre of the phage under shelf-life conditions for a least a year (ongoing study) and for fourteen days under agitation. This work presents a theory-based methodology addressing pharmaco-technical challenges related to the purification and stabilisation of various phages to accelerate and secure phage development for therapeutic applications.