Survival.

<p>Kaplan-Meier curves represent the 48 hour survival of preterm lambs which underwent surfactant inactivation when treated either with CHF 5633 (dotted line) or Poractant alfa (continuous line). Analysis by Gehan-Breslow-Wilcoxon test indicated a significant longer survival of lambs treated with CHF 5633 compared to Poractant alfa treated lambs (p<0.05).</p

New Surfactant with SP-B and C Analogs Gives Survival Benefit after Inactivation in Preterm Lambs

<div><h3>Background</h3><p>Respiratory distress syndrome in preterm babies is caused by a pulmonary surfactant deficiency, but also by its inactivation due to various conditions, including plasma protein leakage. Surfactant replacement therapy is well established, but clinical observations and <em>in vitro</em> experiments suggested that its efficacy may be impaired by inactivation. A new synthetic surfactant (CHF 5633), containing synthetic surfactant protein B and C analogs, has shown comparable effects on oxygenation in ventilated preterm rabbits versus Poractant alfa, but superior resistance against inactivation <em>in vitro</em>. We hypothesized that CHF 5633 is also resistant to inactivation by serum albumin <em>in vivo</em>.</p> <h3>Methodology/Principal Findings</h3><p>Nineteen preterm lambs of 127 days gestational age (term = 150 days) received CHF 5633 or Poractant alfa and were ventilated for 48 hours. Ninety minutes after birth, the animals received albumin with CHF 5633 or Poractant alfa. Animals received additional surfactant if P_aO₂ dropped below 100 mmHg. A pressure volume curve was done post mortem and markers of pulmonary inflammation, surfactant content and biophysiology, and lung histology were assessed. CHF 5633 treatment resulted in improved arterial pH, oxygenation and ventilation efficiency index. The survival rate was significantly higher after CHF 5633 treatment (5/7) than after Poractant alfa (1/8) after 48 hours of ventilation. Biophysical examination of the surfactant recovered from bronchoalveolar lavages revealed that films formed by CHF 5633-treated animals reached low surface tensions in a wider range of compression rates than films from Poractant alfa-treated animals.</p> <h3>Conclusions</h3><p>For the first time a synthetic surfactant containing both surfactant protein B and C analogs showed significant benefit over animal derived surfactant in an <em>in vivo</em> model of surfactant inactivation in premature lambs.</p> </div

Study design.

<p>Preterm lambs received a 200 mg/kg bodyweight intra-tracheal dose of either Poractant alfa or CHF 5633. Ninety minutes after birth a mixture consisting of 9.4 mg/kg human serum albumin and either 100 mg/kg Poractant alfa or 100 mg/kg CHF 5633 was given intra-tracheally to simulate surfactant inactivation. If P_aO₂ dropped below 100 mmHg, the lambs received an additional dose of either 200 mg/kg Poractant alfa or 200 mg/kg CHF 5633 every two hours until the P_aO₂ increased above the 100 mmHg threshold. 48 hours after birth the lambs were euthanized.</p

Surfactant administration.

<p>Bw – bodyweight. Data expressed as mean±SEM. * p<0.05, unpaired t-test.</p

Ventilation.

<p><b>A</b> The ventilation efficiency index (VEI) of lambs treated with CHF 5633 was elevated at all time points compared to Poractant alfa treated lambs, but only reached significance at 90 minutes after birth, just before inactivation (t = 0). <b>B</b> The partial oxygen pressure in arterial blood (P_aO₂) of lambs treated with CHF 5633 was elevated at most time points compared to Poractant alfa treated lambs, but only reached significance at 18 hours after surfactant inactivation. <b>C</b> The arterial blood pH of lambs treated with synthetic surfactant was elevated at all time points compared to Poractant alfa treated lambs, but only reached significance at 24 hours after surfactant inactivation. Grey spheres = CHF 5633; Black cubes = Poractant alfa. Data expressed as mean±SEM. *p<0.05, two-way repeated-measures analysis of variance.</p

Parameters defining interfacial performance.

<p>Comparison of parameters defining the interfacial performance in the CBS of films formed by material obtained from the bronchoalveolar lavage of CHF 5633 treated and Poractant alfa treated animals. Data plotted are the minimal surface tension reached after 1 min of initial or post-expansion adsorption (upper panel), and the minimal surface tension, the percent of area reduction required to reach minimal tension and the maximal tension during quasi-static (middle panels) or dynamic (lower panels) compression-expansion cycling. Data expressed as mean±SEM. *p<0.05, two-way repeated-measures analysis of variance.</p

Surface behavior.

<p>Compression-expansion cycling isotherms in the CBS of films formed by original CHF 5633 or Poractant alfa preparations (left panels) and of films formed by material obtained from the bronchoalveolar lavage of CHF 5633-treated or Poractant alfa-treated animal lungs (right panels). Isotherms were obtained either under slow quasi-static (upper panels) or fast dynamic (lower panels) cycling regimes. Quasi-static isotherms include those from the 1^st (closed circles), 2^nd (open circles), 3^rd (closed triangles) and 4^th (open triangles) compression-expansion cycles, while dynamic isotherms are plotted from the 1^st (closed circles), 10^th (open circles) and 20^th (triangles) cycle.</p

Observations of preterm lambs born at 127 days GA which were treated with Poractant alfa or CHF 5633.

<p>Neutrophils were decreased in the lungs of preterm lambs treated with CHF 5633 compared to Poractant alfa treated lambs after surfactant inactivation by albumin. BALF – bronchoalveolar lavage fluid; bw – bodyweight; OD – optical density. Data expressed as mean±SEM. * p<0.05, unpaired t-test.</p

Lung physiology.

<p>Lung tissue stained with hematoxylin and eosin of lambs treated with CHF 5633 (<b>A</b>) and Poractant alfa (<b>B</b>). Alveolar spaces were much larger with less interstitial bleeding in lungs of lambs treated with the synthetic surfactant compared to the lungs of Poractant alfa treated lambs. <b>C</b> Lung compliance at 40 cmH₂O airway pressure was increased in lambs treated with synthetic surfactant, but did not reach statistical significance (p = 0.056, two-way repeated-measures analysis of variance). <b>D</b> Disaturated phospholipids (DSPL) were not significantly different in the bronchoalveolar lavage fluid (BALF) of lambs treated with synthetic surfactant compared to the BALF of Poractant alfa treated lambs. Burgundy red spheres = CHF 5633; Blue cubes = Poractant alfa. Data expressed as mean±SEM. * p<0.05, Mann-Whitney u-test.</p