Lucinactant, formerly known as KL(4) surfactant, is a novel synthetic lung surfactant containing phospholipids and an engineered peptide, sinapultide, which is designed to mimic the actions of human surfactant protein B. It has been developed for use in the prevention or treatment of respiratory distress syndrome (RDS), a common problem in premature infants, which results from a deficiency or degradation of pulmonary surfactant. Lucinactant is administered intratracheally soon after birth as a replacement surfactant. In the pivotal randomized, double-blind, prophylaxis trial in premature infants, the incidence of RDS at 24 hours after birth was significantly lower in lucinactant recipients than in recipients of colfosceril palmitate, a synthetic non-protein-containing surfactant. RDS-related mortality at 14 days was significantly lower in lucinactant recipients than in recipients of colfosceril palmitate or beractant, a bovine-derived surfactant. In another randomized, double-blind, prophylaxis trial in premature infants, the rate of survival without bronchopulmonary dysplasia at 28 days of age in lucinactant recipients was not inferior to that in recipients of poractant alfa, a porcine-derived surfactant. Lucinactant was generally well tolerated. Adverse events were transient and related to the administration procedure. There were no differences in the incidences of complications of prematurity between lucinactant and the other surfactants.