Epithelial Lining Fluid Concentrations Research Articles

Case study observational research: inflammatory cytokines in the bronchial epithelial lining fluid of COVID-19 patients with acute hypoxemic respiratory failure

BackgroundIn this study, the concentrations of inflammatory cytokines were measured in the bronchial epithelial lining fluid (ELF) and plasma in patients with acute hypoxemic respiratory failure (AHRF) secondary to severe coronavirus disease 2019 (COVID-19).MethodsWe comprehensively analyzed the concentrations of 25 cytokines in the ELF and plasma of 27 COVID-19 AHRF patients. ELF was collected using the bronchial microsampling method through an endotracheal tube just after patients were intubated for mechanical ventilation.ResultsCompared with those in healthy volunteers, the concentrations of interleukin (IL)-6 (median 27.6 pmol/L), IL-8 (1045.1 pmol/L), IL-17A (0.8 pmol/L), IL-25 (1.5 pmol/L), and IL-31 (42.3 pmol/L) were significantly greater in the ELF of COVID-19 patients than in that of volunteers. The concentrations of MCP-1 and MIP-1β were significantly greater in the plasma of COVID-19 patients than in that of volunteers. The ELF/plasma ratio of IL-8 was the highest among the 25 cytokines, with a median of 737, and the ELF/plasma ratio of IL-6 (median: 218), IL-1β (202), IL-31 (169), MCP-1 (81), MIP-1β (55), and TNF-α (47) were lower.ConclusionsThe ELF concentrations of IL-6, IL-8, IL-17A, IL-25, and IL-31 were significantly increased in COVID-19 patients. Although high levels of MIP-1 and MIP-1β were also detected in the blood samples collected simultaneously with the ELF samples, the results indicated that lung inflammation was highly compartmentalized. Our study demonstrated that a comprehensive analysis of cytokines in the ELF is a feasible approach for understanding lung inflammation and systemic interactions in patients with severe pneumonia.

Effects of Lung Inflammation and Injury on Pulmonary Tissue Penetration of Meropenem and Vancomycin in a Model of Unilateral Lung Injury

Timing and dosing of antimicrobial therapy is key in the treatment of pneumonia in critically ill patients. It is uncertain whether presence of lung inflammation and injury affects tissue penetration of intravenously administered antimicrobial drugs. We determined the effects of lung inflammation and injury on tissue penetration of two commonly used antimicrobial drugs for pneumonia in an established model of unilateral lung injury. In 13 healthy pigs, unilateral lung injury was induced in the left lung through cyclic rinsing - the right healthy lung served as control. After infusion of meropenem and vancomycin, lung tissue, blood, and epithelial lining fluid concentrations were monitored and compared over a period of 6 hours. Median vancomycin lung tissue concentrations as well as penetration ratio were higher in inflamed and injured lungs compared to uninflamed and uninjured lungs (AUC0-6h: P = 0.003 and AUCdialysate/AUCplasma ratio: P = 0.003), resulting in higher AUC0-24/MIC. Median meropenem lung tissue concentrations as well as penetration were not different in inflamed and injured lungs compared to uninflamed and uninjured lungs (AUC0-6 P = 0.094 and AUCdialysate/AUCplasma ratio P = 0.173). Penetration ratio for both vancomycin and meropenem into epithelial lining fluid was not different between injured and uninjured lungs. Vancomycin penetration into lung tissue is enhanced by acute inflammation and injury, a phenomenon barely evident with meropenem. Therefore, inflammation in lung tissue influences the penetration into interstitial lung tissue, depending on the chosen antimicrobial drug. Measurement of ELF levels alone might not detect impact of inflammation and injury.

Population pharmacokinetics and humanized dosage regimens matching the peak, area, trough, and range of amikacin plasma concentrations in immune-competent murine bloodstream and lung infection models.

Amikacin is an FDA-approved aminoglycoside antibiotic that is commonly used. However, validated dosage regimens that achieve clinically relevant exposure profiles in mice are lacking. We aimed to design and validate humanized dosage regimens for amikacin in immune-competent murine bloodstream and lung infection models of Acinetobacter baumannii. Plasma and lung epithelial lining fluid (ELF) concentrations after single subcutaneous doses of 1.37, 13.7, and 137 mg/kg of body weight were simultaneously modeled via population pharmacokinetics. Then, humanized amikacin dosage regimens in mice were designed and prospectively validated to match the peak, area, trough, and range of plasma concentration profiles in critically ill patients (clinical dose: 25-30 mg/kg of body weight). The pharmacokinetics of amikacin were linear, with a clearance of 9.93 mL/h in both infection models after a single dose. However, the volume of distribution differed between models, resulting in an elimination half-life of 48 min for the bloodstream and 36 min for the lung model. The drug exposure in ELF was 72.7% compared to that in plasma. After multiple q6h dosing, clearance decreased by ~80% from the first (7.35 mL/h) to the last two dosing intervals (~1.50 mL/h) in the bloodstream model. Likewise, clearance decreased by 41% from 7.44 to 4.39 mL/h in the lung model. The humanized dosage regimens were 117 mg/kg of body weight/day in mice [administered in four fractions 6 h apart (q6h): 61.9%, 18.6%, 11.3%, and 8.21% of total dose] for the bloodstream and 96.7 mg/kg of body weight/day (given q6h as 65.1%, 16.9%, 10.5%, and 7.41%) for the lung model. These validated humanized dosage regimens and population pharmacokinetic models support translational studies with clinically relevant amikacin exposure profiles.

2550. Comparing Efficacy of Serum and Epithelial Lining Fluid Concentrations for Meropenem Against Carbapenem-Resistant Enterobacterales

Abstract Background Carbapenem-resistant Enterobacterales are a CDC urgent threat and need effective free drug concentrations at sites of infection such as epithelial lining fluid (ELF) for pneumonia. Therefore, it’s the goal of this study to compare efficacy of meropenem serum and ELF concentrations while measuring for susceptibility changes in a five day in-vitro pharmacodynamic model. Methods An AmpC β-lactamase producing E. cloacae with porin mutations and a meropenem minimum inhibitory concentration (MIC) of 2μg/mL was used to make a starting model inoculum of 6 log10 CFU/mL. One compartment in vitro pharmacodynamic models were run in triplicate, with inflow media set to the antibiotic half-life of 1.5 hours. Samples were taken from models for CFU/mL counts at 0, 6, 8, 24, 32, 48, 72, 96, and 120 hours with a limit of detection 2 log10 CFU/mL. Antibiotic target peak concentrations for serum was 26.6 μg/mL (71% T >MIC) to emulate free drug concentrations in patients at steady state receiving 2g every 8 hours. For ELF simulation, we targeted concentrations of 17.3μg/mL (58% T >MIC) to reflect ELF to unbound drug in plasma ratio of 0.65. MICs for susceptibility changes were determined via E-test, with samples from models at 24, 48, 72, 96, 120 hours being compared to 0-hour MICs. Bactericidal activity was defined as ≥3 log10 CFU/mL reduction in colony counts from the initial inoculum. CFU/mL counts were compared via t-test and p-values of ≤0.05 were considered significant. Meropenem Target Concentrations Targeted concentrations to simulate percent time of unbound meropenem in serum and ELF above the MIC Results Serum targeted models reached the limit of detection by 24 hours with bactericidal activity through 96 hours (p< 0.05). At 120 hours, bacterial regrowth occurred in 2/3 models but was not accompanied by increased MICs (MIC=0.5μg/mL). ELF targeted models reached the limit of detection by 48 hours for 2/3 models and had significant bactericidal activity through 72 hours (p< 0.05). Regrowth occurred at 96 hours through 120 hours and was accompanied by heterogenous resistant sub-populations (MIC shifts from 2 to 4 and to >32μg/mL). The heterogenous colony formation was first seen at 24 hours in ELF models. Meropenem Antibacterial Activity against E. cloacae Meropenem dosing simulating serum concentrations in sick patients at steady state and in ELF Conclusion With both meropenem targeted concentrations above recommended 40% T >MIC, there was bacterial regrowth. Target site concentrations should be considered as a contributing factor to treatment failure and resistance development. Disclosures jason M. Pogue, PharmD, AbbVie: Advisor/Consultant|Entasis: Advisor/Consultant|Ferring: Advisor/Consultant|GSK: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|Qpex: Advisor/Consultant|Shionogi: Advisor/Consultant Kerry L. LaPlante, Pharm.D., FCCP, FIDSA, FIDP, Abbive: Advisor/Consultant|Abbive: Grant/Research Support|Ferring: Advisor/Consultant|Gilead: Grant/Research Support|Melinta: Advisor/Consultant|Merck: Grant/Research Support|NIH: Grant/Research Support|Pfizer: Grant/Research Support|Seres: Advisor/Consultant|Shionogi inc.: Grant/Research Support|VA-HR&D: Grant/Research Support

Quantification of clesrovimab, an investigational, half-life extended, anti-respiratory syncytial virus protein F human monoclonal antibody in the nasal epithelial lining fluid of healthy adults

BackgroundClesrovimab (MK-1654) is an investigational, half-life extended human monoclonal antibody (mAb) against RSV F glycoprotein in clinical trials as a prophylactic agent against RSV infection for infants. MethodsThis adult study measured clesrovimab concentrations in the serum and nasal epithelial lining fluid (ELF) to establish the partitioning of the antibody after dosing. Clesrovimab concentrations in the nasal ELF were normalized for sampling dilution using urea concentrations from ELF and serum. Furthermore, in vitro RSV neutralization of human nasal ELF following dosing was also measured to examine the activity of clesrovimab in the nasal compartment. FindingsmAbs with YTE mutations are reported in literature to partition ∼1–2 % of serum antibodies into nasal mucosa. Nasal: serum ratios of 1:69–1:30 were observed for clesrovimab in two separate adult human trials after urea normalization, translating to 1.4–3.3 % of serum concentrations. The nasal PK and estimates of peripheral volume of distribution correlated with higher extravascular distribution of clesrovimab. These higher concentration of the antibody in the nasal ELF corroborated with the nasal sample’s ability to neutralize RSV ex vivo. An overall trend of decreased viral plaque AUC was also noted with increasing availability of clesrovimab in the nasal ELF from a human RSV challenge study. InterpretationAlong with its extended half-life, the higher penetration of clesrovimab into the nasal epithelial lining fluid and the associated local increase in RSV neutralization activity could offer infants better protection against RSV infection.

Pharmacokinetic Considerations for Optimizing Inhaled Spray-Dried Pyrazinoic Acid Formulations.

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a leading cause of death with 1.6 million deaths worldwide reported in 2021. Oral pyrazinamide (PZA) is an integral part of anti-TB regimens, but its prolonged use has the potential to drive the development of PZA-resistant Mtb. PZA is converted to the active moiety pyrazinoic acid (POA) by the Mtb pyrazinamidase encoded by pncA, and mutations in pncA are associated with the majority of PZA resistance. Conventional oral and parenteral therapies may result in subtherapeutic exposure in the lung; hence, direct pulmonary administration of POA may provide an approach to rescue PZA efficacy for treating pncA-mutant PZA-resistant Mtb. The objectives of the current study were to (i) develop novel dry powder POA formulations, (ii) assess their feasibility for pulmonary delivery using physicochemical characterization, (iii) evaluate their pharmacokinetics (PK) in the guinea pig model, and (iv) develop a mechanism-based pharmacokinetic model (MBM) using in vivo PK data to select a formulation providing adequate exposure in epithelial lining fluid (ELF) and lung tissue. We developed three POA formulations for pulmonary delivery and characterized their PK in plasma, ELF, and lung tissue following passive inhalation in guinea pigs. Additionally, the PK of POA following oral, intravenous, and intratracheal administration was characterized in guinea pigs. The MBM was used to simultaneously model PK data following administration of POA and its formulations via the different routes. The MBM described POA PK well in plasma, ELF, and lung tissue. Physicochemical analyses and MBM predictions suggested that POA maltodextrin was the best among the three formulations and an excellent candidate for further development as it has: (i) the highest ELF-to-plasma exposure ratio (203) and lung tissue-to-plasma exposure ratio (30.4) compared with POA maltodextrin and leucine (75.7/16.2) and POA leucine salt (64.2/19.3) and (ii) the highest concentration in ELF (CmaxELF: 171 nM) within 15.5 min, correlating with a fast transfer into ELF after pulmonary administration (KPM: 22.6 1/h). The data from the guinea pig allowed scaling, using the MBM to a human dose of POA maltodextrin powder demonstrating the potential feasibility of an inhaled product.

The In Vitro, In Vivo, and PBPK Evaluation of a Novel Lung-Targeted Cardiac-Safe Hydroxychloroquine Inhalation Aerogel.

Hydroxychloroquine (HCQ) was repurposed for COVID-19 treatment. Subtherapeutic HCQ lung levels and cardiac toxicity of oral HCQ were overcome by intratracheal (IT) administration of lower HCQ doses. The crosslinker-free supercritical fluid technology (SFT) produces aerogels and impregnates them with drugs in their amorphous form with efficient controlled release. Mechanistic physiologically based pharmacokinetic (PBPK) modeling can predict the lung's epithelial lining fluid (ELF) drug levels. This study aimed to develop a novel HCQ SFT formulation for IT administration to achieve maximal ELF levels and minimal cardiac toxicity. HCQ SFT formulation was prepared and evaluated for physicochemical, in vitro release, pharmacokinetics, and cardiac toxicity. Finally, the rat HCQ ELF concentrations were predicted using PBPK modeling. HCQ was amorphous after loading into the chitosan-alginate nanoporous microparticles (22.7±7.6 μm). The formulation showed a zero-order release, with only 40% released over 30 min compared to 94% for raw HCQ. The formulation had a tapped density of 0.28 g/cm3 and a loading efficiency of 35.3±1.3%. The IT administration of SFT HCQ at 1 mg/kg resulted in 23.7-fold higher bioavailability, fourfold longer MRT, and eightfold faster absorption but lower CK-MB and LDH levels than oral raw HCQ at 4 mg/kg. The PBPK model predicted 6 h of therapeutic ELF levels for IT SFT HCQ and a 100-fold higher ELF-to-heart concentration ratio than oral HCQ. Our findings support the feasibility of lung-targeted and more effective SFT HCQ IT administration for COVID-19 compared to oral HCQ with less cardiac toxicity. Graphical abstract.

Population pharmacokinetic modeling of the influence of chronic and acute biofilm-forming Pseudomonas aeruginosa lung infection on ciprofloxacin free pulmonary and epithelial lining fluid concentrations

We previously reported that ciprofloxacin (CIP) free lung interstitial concentrations are decreased by biofilm-forming Pseudomonas aeruginosa pulmonary chronic (14 d) infection. To get a better understanding on the influence of infection on CIP lung distribution, in the present study free lung interstitial fluid and epithelial lining fluid (ELF) concentrations were determined by microdialysis in biofilm-forming P. aeruginosa acutely (2 d) and chronically infected (14 d) Wistar rats following CIP 20 mg/kg i.v. bolus dosing. A popPK model was developed, using NONMEM® (version 7.4.3) with FOCE+I, with plasma data described as a three-compartment model with first-order elimination. For lung data inclusion, the model was expanded to four compartments and ELF concentrations were described as a fraction of lung levels estimated as a distribution factor (ƒD). Acute infection had a minor impact on plasma and lung CIP distribution and both infection stages did not alter ELF drug penetration. Probability of target attainment of ƒAUC0–24/MIC ≥ 90 using 20 mg q8h, equivalent to 400 mg q8h in humans, showed that CIP free concentrations in plasma are adequate to successfully treat lung infections. However, lung and ELF free interstitial concentrations might be insufficient to result in efficacious treatment of biofilm-forming P. aeruginosa chronic infection. However, lung and ELF free interstitial concentrations might be insufficient to result in efficacious treatment of biofilm-forming P. aeruginosa chronic infection.

Single-dose pharmacokinetics and lung function of nebulized niclosamide ethanolamine in sheep

PurposeNiclosamide is approved as an oral anthelminthic, but its low oral bioavailability hinders its medical use requiring high drug exposure outside the gastrointestinal tract. An optimized solution of niclosamide for nebulization and intranasal administration using the ethanolamine salt has been developed and tested in a Phase 1 trial. In this study we investigate the pulmonary exposure of niclosamide following administration via intravenous injection, oral administration or nebulization.MethodsWe characterized the plasma and pulmonary pharmacokinetics of three ascending doses of nebulized niclosamide in sheep, compare it to intravenous niclosamide for compartmental PK modelling, and to the human equivalent approved 2 g oral dose to investigate in the pulmonary exposure of different niclosamide delivery routes. Following a single-dose administration to five sheep, niclosamide concentrations were determined in plasma and epithelial lining fluid (ELF). Non-compartmental and compartmental modeling was used to characterize pharmacokinetic profiles. Lung function tests were performed in all dose groups.ResultsAdministration of all niclosamide doses were well tolerated with no adverse changes in lung function tests. Plasma pharmacokinetics of nebulized niclosamide behaved dose-linear and was described by a 3-compartmental model estimating an absolute bioavailability of 86%. ELF peak concentration and area under the curve was 578 times and 71 times higher with nebulization of niclosamide relative to administration of oral niclosamide.ConclusionsSingle local pulmonary administration of niclosamide via nebulization was well tolerated in sheep and resulted in substantially higher peak ELF concentration compared to the human equivalent oral 2 g dose.

The development, validation, and in vivo testing of a high-precision bronchial epithelial lining fluid sampling device.

Analysis of respiratory biomarkers or pharmaceutical drug concentrations in bronchial epithelial lining fluid (bELF) using a high-precision sampling method is crucial for effective clinical respiratory diagnostics and research. Here, we utilized a cellulose matrix as an absorptive probe for bELF sampling, subsequently testing the design of a device and sampling technique in vivo. The absorptive matrix [Whatman® qualitative filter paper (Grade CF-12)] was first tested through tissue-contact experiments on porcine airway tissue. The absorption and elution capacity of the matrix, as well as the laboratory processing and analysis method, was validated with a range of Interleukin-8 (CXCL8) and C-Reactive protein (CRP) stock solutions. Subsequently, the device's design was optimized for universal in-house production and both, safe and efficient sampling. The airway sampling method was then tested in a group of 10 patients with Chronic Obstructive Pulmonary Disease (COPD). For each patient, a bELF sample was obtained using the newly developed bELF probe, as well as a reference 20 mL saline bronchial wash sample. Supernatants were assessed, using an immunoassay, for levels of the pro-inflammatory markers CXCL8, Myeloperoxidase (MPO), and CRP. The bELF samples were compared to bronchial wash. The Whatman® qualitative filter paper (Grade CF-12) bELF probes adhered to porcine airway tissue, softening slightly upon wetting. The material maintained architectural integrity following the removal of the probes, leaving no residual fibers on the porcine airway mucosa. The bELF probe design was optimized for bronchoscopic delivery and in-house production. On average, a fully saturated bELF probe carried 32 μL of protein-rich fluid. The mean return of CXCL8 and CRP from samples collected from a serial dilution series (1, 5, 10, 20 ng/mL) was 69% (range 48%-87%). The bELF probe detected, on average, 7 (MPO), 14 (CRP), and 59 (CXCL8) times higher equivalent inflammatory protein concentrations in the collected bELF probe samples compared to the bronchial wash. The bELF probe is an effective absorptive technology for high-precision bELF sampling without dilution. With a simple in-house production procedure and bronchoscopic sampling technique, this method can be introduced in any bronchoscopic center for a consistent sampling of bELF.

Early life surfactant protein-D levels in bronchoalveolar lavage fluids of extremely preterm neonates.

Surfactant protein-D (SP-D) is a hydrophilic protein with multiple crucial anti-inflammatory and immunological functions. It might play a role in the development and course of pulmonary infections, acute respiratory distress syndrome, and other respiratory disorders. Only few small neonatal studies have investigated SP-D: we aimed to investigate the links between this protein, measured in the first hours of life in extremely preterm neonates, and clinical outcomes, as well its relationship with pulmonary secretory phospholipase A2 (sPLA2). Bronchoalveolar lavage fluids were obtained within the first 3 h of life. SP-D and sPLA2 were measured with ELISA and radioactive method, respectively; epithelial lining fluid concentrations were estimated with urea ratio. Clinical data were prospectively collected. One hundred extremely preterm neonates were nonconsecutively studied. SP-D was significantly raised with increasing gestational age (24-26 wk: 68 [0-1,694], 27 or 28 wk: 286 [0-1,328], 29 or 30 wk: 1,401 [405-2,429] ng/mL, overall P = 0.03). SP-D was significantly higher in cases with clinical chorioamnionitis with fetal involvement (1,138 [68-3,336]) than in those without clinical chorioamnionitis with fetal involvement (0 [0-900] ng/mL, P < 0.001). SP-D was lower in infants with bronchopulmonary dysplasia (BPD) (251 [0-1,550 ng/mL]) compared with those without bronchopulmonary dysplasia (BPD) or who died before its diagnosis (977 [124-5,534 ng/mL], P = 0.05) and this was also significant upon multivariate analysis [odds ration (OR): 0.997 (0.994-0.999), P = 0.024], particularly in neonates between 27- and 28-wk gestation. SP-D significantly correlated with the duration of hospital stay (ρ = -0.283, P = 0.002), invasive ventilation (ρ = -0.544, P = 0.001), and total sPLA2 activity (ρ = 0.528, P = 0.008). These findings help understanding the role of SP-D early in life and support further investigation about the role of SP-D in developing BPD.NEW & NOTEWORTHY Surfactant protein-D increases with gestational age and is inversely associated with BPD development. These results have been obtained in the first hours of life of extremely preterm neonates with optimal perinatal care.

Pharmacokinetics of SPR206 in Plasma, Pulmonary Epithelial Lining Fluid, and Alveolar Macrophages following Intravenous Administration to Healthy Adult Subjects.

SPR206 is a next-generation polymyxin being developed for the treatment of multidrug-resistant (MDR) Gram-negative infections. This Phase 1 bronchoalveolar lavage (BAL) study was conducted to evaluate SPR206's safety and pharmacokinetics in plasma, pulmonary epithelial lining fluid (ELF), and alveolar macrophages (AM) in healthy volunteers. Subjects received a 100 mg intravenous (IV) dose of SPR206 infused over 1 h every 8 h for 3 consecutive doses. Each subject underwent 1 bronchoscopy with BAL at 2, 3, 4, 6, or 8 h after the start of the third IV infusion. SPR206 concentrations in plasma, BAL, and cell pellet were measured with a validated LC-MS/MS assay. Thirty-four subjects completed the study and 30 completed bronchoscopies. Mean SPR206 peak concentrations (Cmax) in plasma, ELF, and AM were 4395.0, 735.5, and 860.6 ng/mL, respectively. Mean area under the concentration-time curve (AUC0-8) for SPR206 in plasma, ELF, and AM was 20120.7, 4859.8, and 6026.4 ng*h/mL, respectively. The mean ELF to unbound plasma concentration ratio was 0.264, and mean AM to unbound plasma concentration ratio was 0.328. Mean SPR206 concentrations in ELF achieved lung exposures above the MIC for target Gram-negative pathogens for the entire 8-h dosing interval. Overall, SPR206 was well tolerated; 22 subjects (64.7%) reported at least 1 treatment-emergent adverse event (TEAE). Of the 40 reported TEAEs, 34 (85.0%) were reported as mild in severity. The most frequent TEAEs were oral paresthesia (10 subjects [29.4%]) and nausea (2 subjects [5.9%]). This study demonstrates pulmonary penetration of SPR206 and supports further development of SPR206 for the treatment of patients with serious infections caused by MDR Gram-negative pathogens.

Estimating Unbound Drug Concentrations in Simulated Human Lung Fluid: Relevance to Lung Antibiotic PKPD.

The use of unbound drug concentrations is crucial for the prediction of efficacious doses. Hence, dose predictions for antibiotics targeting respiratory pathogens should be based on free, rather than the currently used, total drug concentrations in epithelial lining fluid (ELF). In this work, we describe an assay to estimate the percent unbound of drugs in ELF using simulated epithelial lining fluid (sELF) containing the most abundant components of ELF in healthy humans. A diverse set of 85 compounds showed a broad range of unbound values ranging from <0.01 to 100%. Binding in sELF was influenced by ionization, with basic compounds typically resulting in a stronger binding than neutral and acidic compounds (median percent unbound values 17, 50, and 62%, respectively). A permanent positive charge further increased binding (median percent unbound 11%), while zwitterions showed a lower binding (median percent unbound 69%). In lipid-free sELF, the binding of basic compounds was less pronounced, while compounds of other ionization classes were less impacted, indicating that lipids are involved in the binding of bases. A reasonable correlation was found between binding in sELF and human plasma (R2 = 0.75); however, plasma binding poorly predicted sELF binding for basic compounds (R2 = 0.50). Bases are an important compound class for antibacterial drug development since positive charges affect permeability into Gram-negative bacteria, which are important in terms of bacterial pneumonia. To evaluate in vivo activity, we selected two bases, for which strong sELF binding was observed (percent unbound <1 and 7%) and conducted an analysis of antibacterial efficacy in the neutropenic murine lung efficacy model and total vs free ELF drug concentrations. In both cases, the total ELF resulted in an overprediction of expected efficacy, while the corrected free ELF explained the observed in vivo efficacy. This supports that free, and not total, ELF concentrations should be used for the efficacious dose prediction for pneumonia and highlights the importance of determining binding in this matrix.

Inhaled amikacin for pneumonia treatment and dissemination prevention: an experimental model of severe monolateral Pseudomonas aeruginosa pneumonia

BackgroundPseudomonas aeruginosa pneumonia is commonly treated with systemic antibiotics to ensure adequate treatment of multidrug resistant (MDR) bacteria. However, intravenous (IV) antibiotics often achieve suboptimal pulmonary concentrations. We therefore aimed to evaluate the effect of inhaled amikacin (AMK) plus IV meropenem (MEM) on bactericidal efficacy in a swine model of monolateral MDR P. aeruginosa pneumonia.MethodsWe ventilated 18 pigs with monolateral MDR P. aeruginosa pneumonia for up to 102 h. At 24 h after the bacterial challenge, the animals were randomized to receive 72 h of treatment with either inhaled saline (control), IV MEM only, or IV-MEM plus inhaled AMK (MEM + AMK). We dosed IV MEM at 25 mg/kg every 8 h and inhaled AMK at 400 mg every 12 h. The primary outcomes were the P. aeruginosa burden and histopathological injury in lung tissue. Secondary outcomes included the P. aeruginosa burden in tracheal secretions and bronchoalveolar lavage fluid, the development of antibiotic resistance, the antibiotic distribution, and the levels of inflammatory markers.ResultsThe median (25–75th percentile) P. aeruginosa lung burden for animals in the control, MEM only, and MEM + AMK groups was 2.91 (1.75–5.69), 0.72 (0.12–3.35), and 0.90 (0–4.55) log10 CFU/g (p = 0.009). Inhaled therapy had no effect on preventing dissemination compared to systemic monotherapy, but it did have significantly higher bactericidal efficacy in tracheal secretions only. Remarkably, the minimum inhibitory concentration of MEM increased to > 32 mg/L after 72-h exposure to monotherapy in 83% of animals, while the addition of AMK prevented this increase (p = 0.037). Adjunctive therapy also slightly affected interleukin-1β downregulation. Despite finding high AMK concentrations in pulmonary samples, we found no paired differences in the epithelial lining fluid concentration between infected and non-infected lungs. Finally, a non-significant trend was observed for higher amikacin penetration in low-affected lung areas.ConclusionsIn a swine model of monolateral MDR P. aeruginosa pneumonia, resistant to the inhaled AMK and susceptible to the IV antibiotic, the use of AMK as an adjuvant treatment offered no benefits for either the colonization of pulmonary tissue or the prevention of pathogen dissemination. However, inhaled AMK improved bacterial eradication in the proximal airways and hindered antibiotic resistance.

Assessment of Epithelial Lining Fluid Partitioning of Systemically Administered Monoclonal Antibodies in Rats

For systemically administered monoclonal antibodies (mAbs) with pharmacological targets in the epithelial lining fluid (ELF), information on the partitioning of mAb between plasma and ELF is instrumental for dose predictions. Bronchoalveolar lavage (BAL) combined with measurements of urea as indicator of sample dilution is often used to estimate ELF concentrations of a drug. However, unbalanced extraction of mAb and urea could potentially lead to a systematic bias in the back-calculated ELF concentration. In the present study 0.5, 1, or 4 mL phosphate-buffered saline was instilled to lungs of rats to obtain lavage samples after systemic dosing of mAb and tool small molecule (n≥4/group). Furthermore, extraction of urea, mAb and the small molecule was assessed by repeatedly lavaging the lung (n = 4). There was no statistically significant difference in the calculated partitioning into ELF between the evaluated instillation volumes. Repeated BAL demonstrated that urea and the small molecule were extracted from other sources than the ELF. In contrast, there was limited to none in-flow of mAb into the lavage fluid. The unbalanced extraction of urea and mAb could theoretically result in underestimated ELF concentrations and the calculated partitioning of 0.17±0.062 might therefore constitute a lower boundary for the true partitioning.

Distribution of enrofloxacin within the bronchoalveolar region of healthy pigs.

This study aimed to elucidate the distribution of enrofloxacin (ERFX) within the bronchoalveolar region of pigs. Six clinically healthy pigs were allocated to intramuscular treatments with either a single dose of 5 mg/kg or 7.5 mg/kg ERFX. Samples of plasma and bronchoalveolar lavage fluid (BALF) were obtained from each pig 0 (before administration), 3, 8, and 24 hr after ERFX administration. The ERFX concentrations in pulmonary epithelial lining fluid (ELF) and BALF cells showed a similar pattern during the experimental period, whereby ERFX concentrations in both ELF and BALF cells were higher than those in the plasma. These results suggest that intramuscularly injected ERFX is well-distributed in the bronchoalveolar region.

LB2306. Population Pharmacokinetic (PPK), Pharmacokinetic/Pharmacodynamic attainment (PTA), and Clinical Pharmacokinetic/Pharmacodynamic (PK/PD) Analyses for Sulbactam-Durlobactam (SUL-DUR) to Support Dose Selection for the Treatment of Acinetobacter baumannii-calcoaceticus Complex (ABC) Infections

LB2306. Population Pharmacokinetic (PPK), Pharmacokinetic/Pharmacodynamic attainment (PTA), and Clinical Pharmacokinetic/Pharmacodynamic (PK/PD) Analyses for Sulbactam-Durlobactam (SUL-DUR) to Support Dose Selection for the Treatment of <i>Acinetobacter baumannii-calcoaceticus</i> Complex (ABC) Infections

625. SPR206 Pharmacokinetics (PK) in Plasma, Epithelial Lining Fluid (ELF), and Alveolar Macrophages (AM) in Healthy Adult Subjects

Abstract Background SPR206 is a novel intravenously (IV)-administered next-generation polymyxin being developed for the treatment of multi-drug resistant (MDR) Gram-negative (GN) infections. A Phase 1 bronchoalveolar lavage (BAL) study was conducted to evaluate SPR206 safety and PK in plasma and pulmonary matrices (ELF and AM) in healthy volunteers. Methods Subjects received 100 mg SPR206 administered intravenously over 1 h q8h for 3 consecutive doses. Blood samples were collected pre-dose (second and third dose) and at 2, 3, 4, 6, and 8 h after the start of the last dose. Each subject underwent one standardized bronchoscopy with BAL at 2, 3, 4, 6 or 8 hours after the start of the third IV infusion. Concentrations of SPR206 in plasma, BAL, and cell pellet were measured with a validated LC-MS/MS assay. Plasma, ELF, and AM PK parameters were determined by noncompartmental analysis. SPR206 AUC0–8 in ELF and AM were calculated using the mean concentration values at the BAL sampling times. SPR206 AUC0–8 ratios of ELF and AM to unbound plasma were determined using plasma protein binding value of 8.6%. Results Thirty-four subjects were enrolled and completed the study and 30 of 34 completed bronchoscopy. The mean SPR206 Cmax concentrations in plasma, ELF, and AM were 4395.0, 735.5, and 860.6 ng/mL, respectively. Mean AUC0-8 h values in plasma, ELF, and AM concentrations were 20120.7, 4859.8, and 6026.4 ng*h/mL, respectively--leading to a free ELF to plasma concentration ratio of 0.264 and free AM to plasma ratio of 0.328. Importantly, mean concentrations of SPR206 in the ELF achieved lung exposures above its minimum inhibitory concentration for the targeted gram-negative pathogens for the entire 8-hour dosing interval. Figure 1 displays the mean (±SD) SPR206 total and unbound plasma, ELF, and AM concentrations at the BAL sampling times. Overall, SPR206 was well tolerated; 22 subjects (64.7%) experienced at least 1 TEAE, mostly mild with a few moderate. The most frequently reported TEAEs were oral paresthesia [10 subjects (29.4%)] and nausea [2 subjects (5.9%)], which were reversible. Conclusion This study demonstrates pulmonary penetration of SPR206 and supports further development of SPR206 for the treatment of patients with pneumonia caused by MDR GN infections. Figure 1.Mean (±SD) plasma (total and unbound), epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of SPR206 in healthy adult subjects. This study was conducted in collaboration with, and with financial support from, the United States Department of Defense (Award No. W81XWH1910295). Disclosures Keith A. Rodvold, PharmD, Spero Therapeutics: Advisor/Consultant|Spero Therapeutics: Honoraria Justin Bader, n/a, Spero Therapeutics: Employee Vipul K. Gupta, Ph.D., Spero Therapeutics: Employee Troy Lister, Ph.D., Spero Therapeutics: Employee Praveen Srivastava, Ph.D., Spero Therapeutics: Employee Jon Bruss, M.D., Spero Therapeutics: Employee.

1132. Integrated Quantitative Systems Pharmacology (QSP) Characterizing Viral Dynamics After Intramuscular (IM) Adintrevimab (ADI) Administration in Participants with Mild to Moderate Coronavirus Disease (COVID-19)

Abstract Background ADI is a fully human IgG1 monoclonal antibody engineered to have an extended half-life with high potency and broad neutralization against SARS-CoV-2 and other SARS-like coronaviruses. The goal of our analysis was to develop a QSP model in which ADI concentrations in upper airway (UA) epithelial lining fluid (ELF) were linked to a viral dynamic model to describe the impact of ADI on SARS-CoV-2 viral load relative to placebo. Methods The QSP model was fit in NONMEM Version 7.4 using PK data from a Phase 1 study (N=24, IV and IM) and from Phase 2/3 COVID-19 prevention (EVADE; N=659, IM) and treatment (STAMP; N=189, IM) studies. Saliva and NP samples were collected from STAMP study participants (pts) infected with the delta or omicron variants. The viral dynamic model was based on a published model and was modified to include both active (V) and deactivated (DV) virus (Fig). The viral dynamic model was fit to the NP swab viral load data (2 samples/pt) standardized to time since infection based upon recorded symptom onset. Saliva data (7-8 samples/pt) was fit sequentially using a biophase compartment given the peak viral load was modestly lower and peaked later than Day 1. Viral dynamic model (A) and simulated median (90% PI) NP viral load reduction in ADI-treated or placebo participants for delta (B) and omicron (C) variants Results The QSP model provided an excellent fit to serum ADI concentration-time data after estimation of a transit rate to account for IM absorption, plasma volume, and the ADI-neonatal Fc receptor dissociation rate constant. The linked viral dynamic model captured the NP swab viral load data after estimating differences in within-host replication factor (R0) and viral production rate (p) by variant. Maximal ADI-induced effect (Smax) on stimulating viral clearance (c) was fixed to 0.43 based upon prior modeling. ADI concentration in UA ELF resulting in 50% of Smax (SC50) was estimated to be 0.086 for delta and 1.05 mg/L for omicron. Figure B and C show model-based simulated median (90% PI) viral load reduction in ADI-treated or placebo pts for delta and omicron variants. Conclusion This QSP model, in conjunction with information on new variants available early in outbreaks (IC50, infectivity (R0), viral production rate [each a model parameter]), allows for rapid dose identification in response to emerging variants. Disclosures Evan Tarbell, PhD, Adagio Therapeutics: Advisor/Consultant|Adagio Therapeutics: Grant/Research Support Scott A. Van Wart, PhD, Adagio Therapeutics: Advisor/Consultant|Adagio Therapeutics: Grant/Research Support Myra Popejoy, PharmD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Kristin Narayan, PhD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Ellie Hershberger, PharmD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Xia Pu, PhD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Jean Gong, PhD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Christopher M. Rubino, PharmD, Adagio Therapeutics: Grant/Research Support|Amplyx Pharmaceuticals, Inc: Grant/Research Support|AN2 Therapeutics: Grant/Research Support|Antabio SAS: Grant/Research Support|Arcutis Biotherapeutics, Inc: Grant/Research Support|B. Braun Medical Inc.: Grant/Research Support|Basilea Pharmaceutica: Grant/Research Support|Boston Pharmaceuticals: Grant/Research Support|Bravos Biosciences: Ownership Interest|Celdara Medical LLC: Grant/Research Support|Cidara Therapeutics Inc: Grant/Research Support|Cipla USA: Grant/Research Support|Crestone Inc: Grant/Research Support|CXC: Grant/Research Support|Debiopharm International SA: Grant/Research Support|Entasis Therapeutics: Grant/Research Support|Evopoint Biosciences Co.: Grant/Research Support|Fedora Pharmaceuticals: Grant/Research Support|GlaxoSmithKline: Grant/Research Support|Hoffmann-La Roche: Grant/Research Support|ICPD: Ownership Interest|ICPD Biosciences, LLC.: Ownership Interest|Insmed Inc.: Grant/Research Support|Iterum Therapeutics Limited: Grant/Research Support|Kaizen Bioscience, Co.: Grant/Research Support|KBP Biosciences USA: Grant/Research Support|Lassen Therapeutics: Grant/Research Support|Matinas Biopharma: Grant/Research Support|Meiji Seika Pharma Co., Ltd.: Grant/Research Support|Melinta Therapeutics: Grant/Research Support|Menarini Ricerche S.p.A: Grant/Research Support|Mutabilis: Grant/Research Support|Nabriva Therapeutics AG: Grant/Research Support|Novartis Pharmaceuticals Corp.: Grant/Research Support|Paratek Pharmaceuticals, Inc.: Grant/Research Support|PureTech Health: Grant/Research Support|Sfunga Therapeutics: Grant/Research Support|Spero Therapeutics,: Grant/Research Support|Suzhou Sinovent Pharmaceuticals Co.: Grant/Research Support|TauRx Therapeutics: Grant/Research Support|Tetraphase Pharmaceuticals: Grant/Research Support|tranScrip Partners: Grant/Research Support|Utility Therapeutics: Grant/Research Support|Valanbio Therapeutics, Inc.: Grant/Research Support|VenatoRx: Grant/Research Support|Wockhardt Bio AG: Grant/Research Support Andrew Santulli, BSE, Adagio Therapeutics: Advisor/Consultant|Adagio Therapeutics: Grant/Research Support Paul Ambrose, PharmD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds|Institute for Clinical Pharmacodynamics: President.

Epithelial lining fluid concentrations of ceftriaxone in children with community-acquired pneumonia.

Ceftriaxone is widely used in children with community-acquired pneumonia. Currently, there are no available data regarding epithelial lining fluid (ELF) concentrations of ceftriaxone in children. Thus, blood and bronchoalveolar lavage fluids samples were collected by using an opportunistic sampling design, then we determined plasma and ELF concentrations in 22 children (0.5-11.7 years), with a total of 36 plasma and 22 ELF samples available for analysis. Ceftriaxone plasma and ELF concentrations ranged from 1.07 to 138.71 mg/L and from 0.61 to 26.69 mg/L, respectively. Ceftriaxone concentration in ELF was 12.18 ± 5.15 (mean ± standard deviation) times higher than that in plasma, ranging from 1.29 to 20.44.