(T1430-02-08) Spectinamide 1599 Exposure in Lung, ELF and Plasma after Passive Inhalation in Mice

Purpose: Spectinamides are a series of semisynthetic compounds derived from the naturally occurring antibiotic spectinomycin. Spectinamide 1599 is a lead compound under preclinical development for the treatment of multi-drug resistant tuberculosis. Due to its low oral bioavailability, spectinamide 1599 has been tested for administration via the intrapulmonary delivery route, and it has resulted in high pulmonary and systemic exposure and high antibacterial activity.  We have been exploring different types of passive inhalation approaches to optimize the delivery of spectinamide 1599 directly into the lungs. The purpose of this study was to determine the pulmonary and systemic exposure of spectinamide 1599 in mice after dry powder passive inhalation using a recently developed passive inhalation chamber and compare it with the results from our previous experiments performed with intravenous (IV) and intrapulmonary aerosol (IPA) administration.

Methods: Female Balb/c mice were exposed to a previously described dry powder formulation of spectinamide 1599 in a passive inhalation chamber for 30 minutes under isoflurane anesthesia[2]. The inhalation chamber was loaded with 40 mg of drug. Mice were removed from the inhalation chamber and sacrificed at different time intervals, 0.083, 0.25, 0.5, 1, 3 and 8 hours (n=5) after dosing. Blood, BALF (bronchioalveolar lavage fluid) and whole lungs were collected from each animal. Lung tissue was homogenized after adding 4X volume of PBS. Plasma samples were separated immediately from blood by centrifugation at 6000 RPM for 5 minutes. Plasma, lung homogenate and BALF samples were extracted with 8 volumes of methanol containing an internal standard (Spectinomycin, 100 ng/mL). Extracts were then analyzed by LC-MS/MS (AB-Sciex 5500) and drug concentrations were quantified. The epithelial lining fluid (ELF) concentrations were determined based on the measured BALF concentrations corrected for the ratio of urea in plasma and BALF samples, obtained using a colorimetric urea assay (QuantiChrom Urea assay Kit; BioAssay Systems).

Results: Spectinamide 1599 exposure in plasma, lung tissue, and ELF after passive dry powder inhalation to Balb/C female mice were successfully obtained. The measured maximum drug concentration (C_max) in plasma and ELF was 0.50 and 65.6 µg/mL, respectively, whereas C_max in the lung homogenate was 5.66 µg/g. The time to reach the maximum concentration (t_max) in ELF was 5 minutes, while t_max in plasma and lung was 15 minutes. The corresponding drug exposure (AUC_0→∞) in plasma, ELF, and lung was 0.470 h*µg/mL, 76.7 h*µg/mL and 7.82 h*µg/g, respectively. Our previous experiments with IPA administration of 10 mg/kg spectinamide 1599 resulted in a C_max of 5.92 and 627 µg/mL in plasma and ELF, respectively, while the maximum lung concentration was measured to be 83.1 µg/g. A total drug exposure of 5.51, 747 and 162 (h*µg/mL or h*µg/g) was observed in plasma, ELF, and lung, respectively. Previous experiments with intravenous administration of 10 mg/kg resulted in a C_max of 58.3 and 22.5 µg/mL in plasma and ELF, respectively, while the maximum lung concentration was found to be 9.63 µg/g. A total drug exposure of 16.1, 74.5, and 8.33 (h*µg/mL or h*µg/g) was observed in plasma, ELF, and lung, respectively.

Conclusion: We were able to achieve reasonable exposures of spectinamide 1599 in ELF and lung after passive dry powder inhalation. The observed exposures in lung tissue and ELF were similar to those after IV administration of 10 mg/kg, but lower than after IPA administration of the same dose. As expected, and similar to IPA administration, the drug exposure in ELF and lung were higher in comparison to plasma after passive dry powder inhalation. Plasma and lung concentrations showed low variability which indicates a good efficiency and reproducibility of the experimental inhalation procedure. The total drug exposure in the investigated organs/body fluids indicates that passive inhalation is a promising alternative to IV administration for spectinamide 1599.

References: Gonzalez-Juarrero, M., et al., Preclinical Evaluation of Inhalational Spectinamide-1599 Therapy against Tuberculosis. ACS Infectious Diseases, 2021. 7(10): p. 2850-2863.
Stewart, I.E., et al., Development and characterization of a dry powder formulation for anti-tuberculosis drug spectinamide 1599. Pharmaceutical research, 2019. 36(9): p. 1-13.
Rodvold, K.A., J.M. George, and L. Yoo, Penetration of anti-infective agents into pulmonary epithelial lining fluid. Clinical pharmacokinetics, 2011. 50(10): p. 637-664.

Acknowledgments: The authors would like to acknowledge Keyur Parmar, Zaid Temrikar, and Amarinder Singh at the University of Tennessee Health Science center for their valuable input. This work was supported by NIH and ALSAC, St. Jude Children’s Research Hospital.

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Pharmacokinetic parameters



1599 drug concentration profile in plasma, ELF and lung