Mechanism of Action
Endogenous pulmonary surfactant reduces surface tension at the air-liquid interface of the alveoli during ventilation and stabilizes the alveoli against collapse at resting transpulmonary pressures.
A deficiency of pulmonary surfactant in preterminfants results in Respiratory Distress Syndrome (RDS) characterized by poor lung expansion, inadequate gas exchange, and a gradual cöllapse of the lungs (atelectasis).
CUROSURF compensates for the deficiency of surfactant and restores surface activity to the lungs of these infants.
Activity
In vitro - CUROSURF lowers minimum surface tension to ≤ 4mN/m as measured
by the Wilhelmy Balance System.
In vivo - In several pharmacodynamic studies, CUROSURF improved lung
compliance, pulmonary gas exchange, or survival in premature rabbits.
Pharmacokinetics
CUROSURF is administered directly to the target organ, the lung, where biophysical effects occur at the alveolar surface.
No human pharmacokinetic studies to characterize the absorption, biotransformation, or excretion of CUROSURF have been performed. Non-clinical studies have been performed to evaluate the disposition of phospholipids present in CUROSURF.
Animal Metabolism
In both adult and newborn rabbits, approximately 50% of the radiolabeled component
was rapidly removed from the alveoli in the first three hours after single intratracheal
administration of CUROSURF-14C-DPPC (dipalmitoylphosphatidylcholine).
Over a 24-hour period, approximately 45% of the labeled DPPC was cleared from the lungs of adult rabbits compared to approximately 20% in newborn rabbits.
In newborn rabbits, CUROSURF-14C-DPPC passed from the alveolar space
into the lung parenchyma and then was secreted again into the alveoli, whereas
in adult rabbits, most of the DPPC was not recycled. The half-life in the lung
appeared to be about 25 hours in adult rabbits and 67 hours in newborn rabbits.
The Concentration of 14C-DPPC in alveolor macrophages was ≤ 2%
of that in the lung in newborn and adult rabbits. Of the total 14C-DPPC
recovered in newborn rabbits, < 0.6% was found in the serum, liver, kidneys,
and brain, respectively, at 48 hours.
No information is available about the metabolic rate of the surfactant-associated
proteins in CUROSURF.
Clinical Studies
The clinical efficacy of CUROSURF was demonstrated in one single-dose study
(Study 1) and one multiple-dose study (Study 2) in the treatment of established
neonatal RDS involving approximately 500 infants. Each study was randomized,
multicenter, and controlled. In Study 1, infants 700-2000g birth weight with
RDS requiring mechanical ventilation and a Fi02 ≥ 0.60 were enrolled.
CUROSURF 2.5 mL/kg single dose (200 mg/kg) or control (disconnection from the ventilator and manual ventiation for 2 minutes) was administered after RDS developed and before 15 hours of age.
The results from Study 1 are shown below in Table 1.
TABLE 1
| EFFICACY PARAMETER |
SINGLE DOSE CUROSURF
n=78
% |
CONTROL
n=67
% |
P-VALUE |
| MORTALITY at 28 DAYS (ALL CAUSES) |
31 |
48 |
≤ 0.05 |
| BRONCHOPULMONARY DYSPLASIA * |
18 |
22 |
N.S. |
| PNEUMOTHORAX |
21 |
36 |
≤ 0.05 |
| PULMONARY INTERSTITIAL EMPHYSEMA |
21 |
38 |
≤ 0.05 |
N.S.: not statistically significant
* Bronchopulmonary dysplasia (BPD) diagnosed by positive x-ray and supplemental
oxygen dependence at 28 days of life. |
In Study 2, infants 700-2000g birth weight with RDS requiring mechanical ventilation
and a Fi02 ≥ 0.60 were enrolled.
In this two-arm trial, CUROSURF was administered after RDS developed and before
15 hours of age, as a single-dose or as multiple doses.
In the single-dose arm, infants received CUROSURF 2.5mL/kg (200mg/kg). In the
multiple-dose arm, the initial dose of CUROSURF was 2.5mL/kg (200mg/kg) and
subsequent doses of CUROSURF were 1.25mL/kg (100mg/kg). The results from Study
2 are shown below in Table 2.
TABLE 2
| EFFICACY PARAMETER |
SINGLE-DOSE CUROSURF
n=184
% |
MUL TIPLE-DOSE CUROSURF
n= 173
% |
P-VALUE |
| MORTALITY at 28 DAYS (ALL CAUSES) |
21 |
13 |
0.048 |
| BRONCHOPULMONARY DYSPLASIA |
18 |
18 |
N.S. |
| PNEUMOTHORAX |
17 |
9 |
0.03 |
| PULMONARY INTERSTITIAL EMPHYSEMA |
27 |
22 |
N.S. |
| N.S.: not statistically significant |
Acute Clinical Effects
As with Qther surfactants, marked improvements in oxygenation may occur within minutes of the administration of CUROSURF.
Last updated on RxList: 12/4/2008