the Baylor College of Medicine. Infasurf (calfactant) will be provided free of charge for the trial by Forest Pharmaceuticals

Pulmonary surfactant is required for normal lung function and survival. Surfactant is composed of various phospholipids and associated proteins. Two of these proteins, surfactant proteins B (SP-B) and C (SP-C), are intimately associated with surfactant lipids and are crucial for surfactant film formation and function in the lung. SP-B is also required for proper packaging of surfactant in lamellar bodies within type II respiratory epithelial cells. Many premature infants have a developmental deficiency of surfactant at birth and benefit from surfactant therapy. Despite antenatal corticosteroids and postnatal surfactant immediately after birth, some premature infants continue to require intubation and assisted mechanical ventilation beyond the first week of life. Continued mechanical ventilation, with exposure to elevated inspired oxygen concentrations and barotrauma, as well as episodes of inflammation and sepsis, increase the risk for development of bronchopulmonary dysplasia (BPD).

Several investigators have reported alterations of surfactant composition and function with respiratory insults resulting in lung injury. Altered production of surfactant proteins has been reported in both rodent and primate animal studies after exposure to high oxygen concentrations. In a study with mice, intra-tracheal administration of surfactant lipids plus SP-B improved survival and lung histology during exposure to hyperoxia. In a rat model of bleomycin-induced lung injury, respiratory distress was associated with a transient deficiency of surfactant proteins B and C. While phospholipid concentration and composition were similar to controls, mature surfactant protein B concentrations in bronchoalveolar lavage samples were decreased 90% in bleomycin-injured animals, and SP-B and SP-C mRNAs were decreased in lung tissue. The minimum surface tension of injured animal BAL samples after phospholipid extraction remained high, suggesting that inhibitory serum proteins were not responsible for the loss of surfactant function. Furthermore, addition of exogenous SP-B (1%) to the phospholipid extract reconstituted minimum surface tension similar to that seen with controls. Beers and colleagues reported that the minimum surface tension of bronchial lavage specimens from human infants with severe BPD was elevated as compared to normal infants, and was similar to that seen in lavage specimens from infants with inherited surfactant protein B deficiency and respiratory failure.

Premature infants requiring persistent intubation and mechanical ventilation beyond the first week of life often experience episodes of respiratory decompensation necessitating increased inspired oxygen concentration and ventilator support. In an analysis of infants 23 to 30 weeks gestation at birth enrolled in the inhaled nitric oxide NOCLD Trial and/or the SCOR Pathophysiology of BPD Study, respiratory decompensations beyond the first week were quantified using daily respiratory severity scores (severity score = mean airway pressure x FIO2). In a subset of infants with existing tracheal aspirate samples, these decompensations were correlated with in vitro measurements of surface activity and surfactant composition. Data from 332 infants were analyzed. After initial postnatal stabilization with assisted ventilation and surfactant therapy, the infants achieved a mean baseline severity score of 1.6 (95%CI 1.5, 1.7) on mean day of life 4.0 (95%CI 3.8, 4.2). For those infants requiring intubation beyond the first week of life, 70% (234/332) had one or more episodes of respiratory decompensation, defined as an acute rise in severity score of > 1.5 points over baseline, sustained for at least 48 hours. The mean duration of these decompensations was 10 days. Sixty five percent (153/234) of the respiratory decompensations occurred within the second week of life. Tracheal aspirate samples obtained from a subset of these infants beyond the first week of life were analyzed for in vitro surface activity, measured by pulsating bubble surfactometry, and for surfactant composition. Timing of weekly tracheal aspirate sampling was pre-determined by the protocols of the SCOR Pathophysiology of BPD, and the NOCLD inhaled nitric oxide trials.

Sixty eight infants yielded 247 tracheal aspirate samples. Seventy five percent (51/68) of the infants had one or more surfactant samples with abnormal function, defined as minimum surface tension > 5.0 mN/m. Forty four percent (109/247) of tracheal aspirate samples had abnormal surface activity, and the frequency of samples with dysfunctional surfactant was similar between weeks 2 and 5 of life.

There was no change in the total amount of phospholipid, or the relative content of phosphatidylcholine and phosphatidylglycerol. Levels of all three surfactant proteins SP-A, SP-B and SP-C were significantly decreased in the samples with dysfunctional surface activity, with the greatest and most significant difference observed for SP-B content (p=0.0001 by multivariable analysis). Western blot analysis of surfactant pellets showed mature 8 kDa SP-B in varying amounts, without evidence of degradation of protein. In addition, total protein content of tracheal aspirate surfactant pellets was not different between samples with normal and abnormal surface tension, suggesting that a large increase in serum proteins was not contributing to the surfactant dysfunction. On analysis by logistic regression using generalized estimating equation, there was a significant association (p=0.005) between abnormal surface tension of the tracheal aspirate samples and significant respiratory deterioration.

Given these results, we hypothesize that administration of additional doses of surfactant with a high concentration of SP-B after the first week of life in infants who continue to require mechanical ventilation will prevent or ameliorate these respiratory decompensations, and protect the lung from further ventilator-induced injury.

We propose a pilot trial of Infasurf surfactant booster therapy for premature infants less than 1250 gm birth weight requiring intubation and mechanical ventilation, starting at postnatal age 7-10 days. Our hypothesis is that 3 prophylactic booster doses of surfactant given every 3 days during the 2nd and 3rd weeks of life will improve the respiratory status of premature infants requiring persistent intubation and mechanical ventilation during the first 28 days of life.

This pilot trial will provide preliminary efficacy and safety data for the large multi-center, randomized, placebo-controlled trial of booster prophylactic surfactant versus placebo, with the primary endpoint as improved survival without BPD at 36 weeks postmenstrual age.

Drug, Phase II, Multi Center

The potential risks for this study are the standard risks of surfactant administration. The most common adverse reactions associated with Infasurf dosing are cyanosis, airway obstruction, bradycardia, reflux of the surfactant in the endotracheal tube, requirement for manual ventilation and reintubation. These events are usually transient and not associated with serious complications. We will minimize this risk by having neonatology physicians present during surfactant administration. We believe that the risks of surfactant administration to neonates beyond the first week of life are equivalent to those of neonates given routine surfactant in the first 72 hours of life, as evidenced by our experience with a prior prophylactic pilot trial. Of infants enrolled in the SCOR Pathophysiology of BPD study, the mean severity score at birth to day 1 of life was 8.25 (range 2.69-13.82), during which time surfactant is routinely administered. In addition, the studies evaluating surfactant replacement in neonates with early chronic lung disease reported improvement in oxygenation, without untoward effects.

Adverse events will be collected surrounding the surfactant administration, and during the 21 day study period. Study investigators will monitor all adverse events. A neonatologist independent of this study will also monitor adverse events. Serious adverse events will be reported to the IRBs and the FDA by the investigators, which include death, severe respiratory decompensation surrounding each surfactant dose (see stopping rules below), and standard life-threatening events including renal failure with creatinine > 2.0, intractable hypotension, necrotizing enterocolitis with perforation, and severe intracranial hemorrhage. Stopping rules for each individual subject enrolled in the study include a respiratory decompensation after surfactant delivery in which the mean airway pressure increases by 5.0 or greater, sustained for at least 2 hours, or an increase in FIO2 greater than 0.5 above baseline, sustained for at least 2 hours.

Our initial data suggest that there may be improvement in oxygenation and ventilation allowing reduction in airway pressures and inspired oxygen concentration after surfactant therapy. Significant improvement in respiratory status may increase the likelihood of earlier withdrawal of mechanical ventilation, and decrease the risk of developing chronic lung disease.