Preclinical Investigation of a Lipoglycopeptide Dry Powder Inhalation Therapy for the Treatment of Pulmonary MRSA Infection

Abstract

The increased prevalence of pulmonary methicillin-resistant Staphylococcus aureus (MRSA) infection in patients living with cystic fibrosis (CF) is concerning due to a correlation with reduced life expectancy and lack of available treatment options. RV94 is a next generation lipoglycopeptide designed for pulmonary delivery that preclinically demonstrated high potency against MRSA in planktonic and protected colonies and improved pulmonary clearance relative to same class molecules. Here, RV94 was formulated into a dry powder for inhalation (DPI) to investigate the localized treatment of pulmonary MRSA presented in a potentially more convenient dosage form. RV94 DPI was generated using a spray-drying process with 12.5 wt% trileucine and demonstrated aerosol characteristics (2.0 μm MMAD and 73% FPF) predictive of efficient pulmonary deposition. In vivo PK from a single dose of RV94 DPI delivered by inhalation to rats yielded lung levels (127 μg/g) much greater than the MRSA minimum inhibitory concentration (0.063 μg/mL), low systemic levels (0.1 μg/mL), and a lung t_1/2 equal to 3.5 days. In a rat acute pulmonary MRSA model, a single dose of RV94 DPI delivered by inhalation either up to seven days prior to or 24 h after infection resulted in a statistically significant reduction in lung MRSA titer.

Keywords: DPI; MRSA; antibiotics; cystic fibrosis; inhalation; lipoglycopeptide.

Figure 1

Chemical structure of RV94 (N^van-2-amino-N-decylacetamide vancomycin).

Figure 2

SEM of RV94 DPI containing 12.5 wt% of trileucine. Scale bar = 2 μm.

Figure 3

RV94 lung (A) and plasma (B) concentration following a single dose of RV94 DPI administered by nose-only inhalation to healthy rats using a VAG dry powder dispenser. Rats in n = 3 cohorts of n = 10 per cohort were dosed for 20 min, and the average mass of drug product aerosolized was 133 ± 14 mg (equivalent to 116 mg RV94 drug substance). The average RV94 dose delivered at the nose as determined by an inline sampling filter was 4.0 ± 0.6 mg/kg. Data were plotted as mean. Error is SEM; n = 5 for immediately post-dose, and n = 3 for all other timepoints. LOD for lung based on the lowest standard curve standard was 0.3 μg/g. LOQ = 0.0015 μg/mL for plasma. Data were fit using a one-phase exponential decay in GraphPad Prism 9.3. R² = 0.85 for lung RV94 and 0.68 for plasma RV94.

Figure 4

A single dose of RV94 DPI administered 7 days or 1 day prior to challenge demonstrates reductions in lung MRSA titer vs. control in an acute pulmonary MRSA (ATCC BAA 1556; USA300) infection in neutropenic rats. The estimated nose dose of RV94 measured from the sampling filter administered on Day-7 was 3.5 mg/kg and on Day-1 was 5.1 mg/kg. Lungs were excised for CFU enumeration at 48 h after infection. Data were plotted as geometric mean. n = 10 for all groups. LOD = 1.9 Log₁₀CFU/lungset. Statistics are based on Mann–Whitney test; p = 0.009 for Day-7 treatment vs. air sham control, p < 0.0001 for Day-1 treatment vs. air sham control. ** Refers to p < 0.01 and **** to p < 0.0001.

Figure 5

A single dose of RV94 inhalation powder administered 24 h after infection demonstrates a reduction in lung MRSA titer vs. control in an acute pulmonary MRSA (ATCC BAA 1556; USA300) infection in neutropenic rats. The estimated nose dose of RV94 measured from the sampling filter was 8.3 mg/kg. Treatment was administered 24 h after infection, and lungs were excised for CFU enumeration at 48 h after infection. Data were plotted as geometric mean. n = 9 for control and 10 for RV94 DPI. In the control group, one rat succumbed to the infection and died. LOD = 1.9 Log₁₀CFU/lungset. Statistics are based on Mann–Whitney test; p = 0.02. * Refers to p < 0.05.