HPi1 is a potent, selective and orally active antimicrobial against Helicobacter pylori with an IC₅₀ of 0.24 μM and an MIC of 0.08-0.16 μg/mL. HPi1 is inactive against other bacteria, including the gut commensals Lactobacillus casei, Lactobacillus reuteri, and Bifidobacterium longum^[1]. IC50 & Target: IC50: 0.24 μM (Helicobacter pylori)^[1]
MIC: 0.08-0.16 μg/mL (Helicobacter pylori)^[1] In Vitro: The MIC against H. pylori isolates ranged from 0.002-0.032 μg/mL (0.01-0.17 μM) in the agar dilution assay. HPi1 is effective against the clarithromycin-resistant strains ARHp172 (MIC of 0.004–0.016 μg/mL) and ARHp246 (MIC of 0.008–0.032 μg/mL)^[1].
HPi1 has some activity against the Bacteroides species, but at concentrations at least 18-fold higher than the H. pylori MIC. More potent activity is detected for Campylobacter jejuni with an MIC of 0.3 μg/mL^[1].
HPi1 has good physicochemical and pharmacological properties, including determining the aqueous solubility (19 μg/mL), human plasma protein binding (93% bound), stability with human liver microsomes (T_1/2 of 1.3 hours) and the ability to passively permeate membranes^[1]. In Vivo: HPi1 (6.25-50 mg/kg; Oral gavage; once a day; for 3 days; female C57BL/6 mice) treatment decreases colony counts below the limit of detection at doses of 25 or 50 mg/kg/day^[1].