The pharmaceutical quality of freeze-dried tablets containing therapeutic bacteriophages against Pseudomonas aeruginosa and Staphylococcus aureus

The preparation of a solid dosage form containing bacteriophages, which meets pharmaceutical requirements and ensures long-term stability of the phage effect, is significant for implementing phage therapy in practice. A commonly used method for processing phages into a solid form is freeze-drying into a so-called freeze-dried cake; however, to date there have been no studies examining the pharmacopeial parameters of freeze-dried tablets with bacteriophages. In this study, we describe the preparation and properties of freeze-dried tablets containing a cocktail of purified pseudomonal bacteriophage DSM 33593 from the genus Pbunavirus and staphylococcal bacteriophage DSM 33473 from the genus Kayvirus (10⁸ PFU/tablet) as the active ingredient. Maltodextrin was used as a tablet filler, and D-mannitol was used as a cryoprotectant. The tablet preparation process resulted in a decrease in phage titer by no more than 1 log PFU/mL. For Pbunavirus, the titer values in tablet and liquid form were comparable. Kayvirus was more stable in tablet form than in liquid form after six months of storage at 25 °C (a decrease of 1.9 ± 0.8 log PFU/mL and 3.8 ± 0.7 log PFU/mL, respectively). The uniformity of mass of single-dose preparations, uniformity of content of single-dose preparations, and their disintegration complied with pharmacopeial requirements. The uniformity of dosage units of the tablets was maintained over three months. A microscopic examination of the internal part of the tablet revealed a heterogeneous structure, which does not affect the required pharmacopeial properties of the tablets. This study highlights the potential of freeze-dried tablets for long-term preservation of the phage effect at room temperature.