Antenatal N-acetylcysteine to improve outcomes of premature infants with intra-amniotic infection and inflammation (Triple I): randomized clinical trial

Background: Intrauterine infection and/or inflammation (Triple I) is an important cause of preterm birth (PTB) and adverse newborn outcomes. N-acetylcysteine (NAC) is a Food and Drug Administration (FDA)-approved drug safely administered to pregnant women with acetaminophen toxicity.

Methods: We conducted a single-center, quadruple-blind, placebo-controlled trial of pregnant women with impending PTB due to confirmed Triple I. Participants (n = 67) were randomized to an intravenous infusion of NAC or placebo mimicking the FDA-approved regimen. Outcomes included clinical measures and mechanistic biomarkers.

Results: Newborns exposed to NAC (n = 33) had significantly improved status at birth and required less intensive resuscitation compared to placebo (n = 34). Fewer NAC-exposed newborns developed two or more prematurity-related severe morbidities [NAC: 21% vs. placebo: 47%, relative risk, 0.45; 95% confidence interval (CI) 0.21-0.95] with the strongest protection afforded against bronchopulmonary dysplasia (BPD, NAC: 3% vs. placebo: 32%, relative risk, 0.10; 95% CI: 0.01-0.73). These effects were independent of gestational age, birth weight, sex, or race. Umbilical cord plasma NAC concentration correlated directly with cysteine, but not with plasma or whole blood glutathione. NAC reduced the placental expression of histone deacetylase-2, suggesting that epigenetic mechanisms may be involved.

Conclusions: These data provide support for larger studies of intrapartum NAC to reduce prematurity-related morbidity.

Impact: In this randomized clinical trial of 65 women and their infants, maternal intravenous NAC employing the FDA-approved dosing protocol resulted in lower composite neonatal morbidity independent of gestational age, race, sex, and birthweight. Administration of NAC in amniocentesis-confirmed Triple I resulted in a remarkably lower incidence of BPD. As prior studies have not shown a benefit of postnatal NAC in ventilated infants, our trial highlights the critical antenatal timing of NAC administration. Repurposing of NAC for intrapartum administration should be explored in larger clinical trials as a strategy to improve prematurity-related outcomes and decrease the incidence of BPD. Fig. 1 FLOWCHART OF ELIGIBLE PARTICIPANTS WITH INCLUSION AND EXCLUSION CIRCUMSTANCES.: PTL preterm labor, PPROM preterm prelabor rupture of membranes, r/o rule-out, GA gestational age, NAC N-acetylcysteine. *Thirteen patients who were ineligible for the trial based on negative assessment for Triple I contributed placental samples as reference for immunohistochemistry experiments. Fig. 2 IMMUNOHISTOCHEMISTRY OF PLACENTAL VILLOUS TISSUE FOR HISTONE DEACETYLASE-2.: Representative micrographs of immunohistochemical staining for histone deacetylase-2 (HDAC2) in placental villous tissue from women with idiopathic preterm birth (iPTB, a, b) absent Triple I or PTB in the context of Triple I who were enrolled in the trial and received either placebo (c, d) or N-acetylcysteine infusion (e, f). Vector NovaRed was used as peroxidase substrate and tissues were imaged and scored blindly for staining intensity without counterstaining. Negative slides (g) were exposed to nonimmune serum. Higher magnification inserts are shown in each lower right corner. All tissues available from the subjects in the trial were analyzed (NAC: n = 32; placebo: n = 33). **P < 0.01; ***p < 0.001. The cases presented in a, c, e, and g were delivered at 28 weeks of gestation. The cases illustrated in b, d, and f were delivered at 32 weeks of gestation. The scale bar (50 μm) denotes the magnification for the panels, which were photographed at ×200. Insets were imaged at ×600 magnification.