Efficacy of Synthetic Peptide-Containing Surfactant in the Treatment of Respiratory Distress Syndrome in Preterm Infant Rhesus Monkeys

Abstract

Studies were conducted to assess the efficacy and safety of a synthetic peptide-containing surfactant in the treatment of respiratory distress syndrome (RDS) in preterm (approximately 80% of normal gestation) infant rhesus monkeys. Surfactant was prepared consisting of the phospholipids dipalmitoylphosphatidyl choline and palmitoyl-oleoyl phosphatidyl glycerol and a synthetic peptide modeled after surfactant protein B (SP-B), "KL4-Surfactant" contained a peptide having the sequence KLLLLKLLLLKLLLLKLLLLK, where "K" is lysine and "L" is leucine. The peptide was selected because it mimics the repeating stretches of hydrophobic residues with intermittent basic hydrophilic residues seen in SP-B. KL4-Surfactant was shown to have biophysical activity assessed as the ability to lower surface tension at an air-liquid interface in a pulsating bubble surfactometer. Thirty premature rhesus monkeys were treated shortly after birth with one dose of KL4-Surfactant. The arterial to alveolar oxygen partial pressure ratio (a/A) was found to rise from a pretreatment level of 0.11 +/- 0.01 (mean +/- SEM), indicative of severe RDS, to 0.40 +/- 0.02 at 12-13 h post-treatment. The improvement in oxygenation persisted throughout the study period, with a mean a/A at 22-23 h of 0.45 +/- 0.07. Chest radiographs and gross and microscopic examination of the lungs all confirmed the reversal of the atelectasis seen before treatment. Animals treated with a dose of 200 mg/kg showed a faster, more consistent, and greater response than did a group treated with an average dose of 127 mg/kg. There was no evidence of toxicity after treatment with the higher dose as demonstrated by physiologic, hematologic, biochemical, and pathologic data. The importance of the peptide in the synthetic surfactant was apparent from the results obtained with a control group of nine premature monkeys treated with a non-peptide-containing surfactant; the a/A of this group was 0.15 +/- 0.03 at nine hours of age as compared with a value of 0.38 +/- 0.02 for 30 comparable animals receiving KL4-Surfactant.

Surfactant for Pediatric Acute Lung Injury

“…Two important conceptual approaches being followed to develop synthetic exogenous surfactants are: (1) Combining human sequence recombinant proteins or synthetic amphipathic peptides with synthetic biological glycerophospholipids; and (2) combining synthetic amphipathic peptides with novel synthetic lipids designed to have favorable physicochemical properties such as high surface activity and structural resistance to inflammatory phospholipases during lung injury. Surfaxin® (KL4) [87,107,123,[189][190][191][192][193][194][195] and Venticute® (recombinant SPC surfactant) [26,[196][197][198][199][200][201] are two current examples of the first of these approaches (Table 3). However, the 21 amino acid KL4 peptide is only a very rough structural analog to native SP-B, and advances in peptide molecular modeling and synthesis technology support the feasibility of preparing new SP-B peptides with significantly greater sequence and molecular folding specificity, and correspondingly higher activity ( [202][203][204] for review).…”

New Synthetic Surfactants – Basic Science

“…Surfaxin has a gel structure that requires heating at 44 ° C for 15 min and subsequent shaking before tracheal instillation [24] . The surfactant increases dynamic lung compliance and oxygenation when tested in premature monkeys [25] . In a noncontrolled clinical trial KL 4 surfactant at a dose of 200 mg/kg was given to newborn babies with RDS resulting in an improvement of arterialto-alveolar oxygen tension ratio [23] .…”

Synthetic surfactants: where are we? Evidence from randomized, controlled clinical trials

“…This surfactant has greater resistance to oxidation and peroxidation than beractant and was shown to improve pulmonary function in an animal model of RDS and a pilot study involving preterm infants with established RDS. [20][21][22] Lucinactant comes in a solution containing 30 mg of phospholipids per ml for a total recommended dose of 5.8 ml kg -1 or 175 mg of phospholipids. It requires warming to 44 1C followed by vigorous shaking and cooling to body temperature before administration.…”