Delivery of PAI-1-targeted intrapleural fibrinolytic therapy for empyema

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Empyema is a bacterial infection of the pleural space, a serious complication of pneumonia that carries a mortality rate of up to 20%, the incidence of which continues to increase worldwide. Intrapleural fibrinolytic therapy (IPFT) involving the delivery of plasminogen activators has been used to expedite drainage of loculated pleural effusions, including empyema. Using a new model of Streptococcus pneumoniae-induced empyema in rabbits we developed a single-dose IPFT with a plasminogen activator inhibitor 1 (PAI-1)-targeted adjunct, which is 8-fold more effective than PA alone for treatment acute empyema. We also validated the ability of our Fibrinolytic Potential Assay (FPA) to predict the success of IPFT in patients with empyema. Interestingly, the efficacy of IPFT in our model of advanced-stage empyema is decreased by 40-50%, similar to what has been observed in patients. This is, in part, due to a significant decrease in the rate of intrapleural fibrinolysis. To mitigate the risk of bleeding complications associated with an increase in the dose of PA, we propose multiple injections of low-dose PAI-1-targeted IPFT to treat advanced-stage empyema. Our objective is to identify effective PAI-1-targeted IPFT for advanced-stage empyema. Our hypothesis is that successful IPFT in advanced-stage empyema requires fibrinolytic activity sustained over a longer period of time and neutralization of PAI-1. The hypothesis will be tested in four Specific Aims: 1. Maximize the efficacy of IPFT in advanced- stage empyema in rabbits by targeting both the slow rate of fibrinolysis and PAI-1, 2. Develop novel PAI-1 targeting peptides to optimize IPFT in advanced-stage empyema, 3. Determine the mechanisms that result in increased resistance to IPFT in advanced-stage empyema, and 4. Using the Fibrinolytic Potential Assay to identify candidates for IPFT prior to treatment. We will select a dosing schedule and use two validated PAI-1 targeting adjuncts (monoclonal antibodies (mAbs), and a docking site peptide) to decrease the dose of PA, test these mechanisms for additivity in PAI-1 targeting to maximize efficacy, and test the efficacy of PAI-1 targeting peptides selected using phage display technology. We will use the FPA to analyze samples from Phase 2 Clinical Trial “A Study to Evaluate LTI-01 in Patients with Infected, Non-draining Pleural Effusions” (ClinicalTrials.gov; NCT04159831). We will use state of the art biochemical techniques to analyze pleural fluid and plasma from human patients and our unique model of empyema to investigate the molecular interactions of fibrinolysis of advanced-stage empyema. Our team has the biochemical, pulmonary and technical expertise to successfully accomplish the proposed work. The project addresses key gaps in our current understanding of the pathogenesis of pleural organization, optimization of IPFT and development of a new diagnostic approach to predict outcomes of IPFT. This project is positioned to shift the paradigm of treatments available for patients with extensive pleural loculation, failed drainage, and advanced-stage empyema.