Pulmonary and neurobehavioral efficacies of AVR-48, a TLR4 modulator, in a preterm lamb model of bronchopulmonary dysplasia.

BACKGROUND: AVR-48 is a small molecule that modulates toll-like receptor 4 (TLR4) activity, changing macrophage phenotype from pro- to anti-inflammatory and increasing the anti-inflammatory cytokine IL-10. Treatment with AVR-48 via intraperitoneal injection effectively prevented hyperoxia-induced pathology in a newborn mouse model of bronchopulmonary dysplasia (BPD). OBJECTIVE: To evaluate the early and late-stage efficacy of AVR-48 in preventing BPD and associated complications in a mechanically ventilated preterm lamb model that mimics human BPD. DESIGN AND METHODS: Preterm lambs were delivered at 128 days (d; about 85% gestation) following the administration of maternal antenatal steroids, intubated, given surfactant, and managed with invasive mechanical ventilation for seven days, followed by three days of noninvasive respiratory support. Either vehicle or AVR-48 was administered to the preterm lambs via intravenous bolus infusion six hours after birth and continued for seven days (every 12 h). Equivalent early (10 d) and late-stage (90 d) endpoints were selected to model human clinical outcomes at 36 weeks and 12-18 months post-natal age, respectively. Survival, growth, pulmonary pathology, respiratory system function, cardiovascular function, and neurobehavioral parameters were evaluated at both early and late stages. The forced oscillation technique was used to assess the resistance and reactance of the respiratory system. Blood samples were collected to determine the pharmacokinetics of AVR-48 and to measure levels of inflammatory and anti-inflammatory cytokines. Lung homogenates were analyzed for TLR4, cleaved caspase-3, p53, PCNA, VEGF, VEGF-R2, and other biomarkers using immunoblot and RT-PCR. RESULTS: Compared to the vehicle, AVR-48 at 3.0 mg/kg significantly reduced respiratory severity scores, increased lung compliance, decreased lung resistance, and preserved alveolar formation without inflammation or fibrosis at 10d. In the 90d study, AVR-48 improved respiratory system mechanics, alveolar formation, and neurodevelopmental outcomes compared to vehicle controls. A decrease in the pro-inflammatory cytokines (IL-1β, IL-6) and an increase in the anti-inflammatory cytokine IL-10 in lamb plasma collected between days 1 and 10 were noted. Lung tissue showed decreased TLR4 protein and inflammatory cytokines at 90d. CONCLUSION: AVR-48 is a promising novel candidate drug for further development in preventing BPD and has the potential to reduce the associated adverse neurodevelopmental sequelae in preterm neonates.