Modifying Pharmacokinetic Properties of the Gram-Negative Bacteria Targeting Endolysin ML06 Without Affecting Antibacterial Activity

With the rise of antibiotic resistance, there is a need for innovative drugs with alternative mechanisms of action. Endolysins meet most of the requirements, but are limited for parenteral use due to their short blood circulation time. In this article, a number of modifications to the ML06-engineered, lysin-targeting Gram-negative bacteria are proposed to improve its pharmacokinetic parameters. Genetic modification with albumin-binding and dimerization domains ranging from 11-12 aa to 45 aa at both the C- and N-termini has resulted in six enzymes that do not exhibit critically reduced antibacterial properties in vitro, and in the case of the ABP1 modification, an improved antibacterial rate and spectra of enzymes. The ML06-ABP1, ML06-ABP2, and HDD-ML06 modifications also retained activity in blood serum and significantly increased serum stability. A pharmacokinetic study of the three modifications in mice showed that ML06-ABP2 and HDD-ML06 have a prolonged half-life compared to the ML06 half-life. In addition, the serum C_max concentration for HDD-ML06 (22.2 μg/mL) was significantly increased compared to ML06 (C_max < 5 μg/mL). Our results allow for a comparison of the different types of modifications that are useful in the development of parenteral antibacterials.