Lucinactant
The first fully synthetic lung surfactant with a protein-mimicking peptide, approved for premature babies in 2012 and since discontinued
Babies born very early often lack surfactant, the slippery film that keeps the tiny air sacs of the lung from collapsing. Lucinactant replaces it with a mix of phospholipids and sinapultide, a 21-amino-acid peptide of lysine and leucine built to imitate human surfactant protein B. Unlike the standard surfactants, which are extracted from cow or pig lungs, it contains nothing from animals. In two large trials in very premature infants it prevented respiratory distress syndrome about as well as animal surfactants, and FDA approved it as Surfaxin in March 2012. The product is now listed as discontinued, and later trials of an inhaled form and of use in adults did not lead to approval.
Last FDA label of a product discontinued in the US (not a current US recommendation): 5.8 mL per kg birth weight, Up to 4 doses, no more often than every 6 hours, Intratracheal, in four aliquots Details ↓
Recommended Dosing
Last FDA label of a product discontinued in the US (not a current US recommendation)
From the last US prescribing information of a product discontinued in the US (see the regulatory status on this page). It records what that label said while the product was sold there; it is not a current US recommendation. Other doses studied, if any, are in the full dosing data below.
Used in human trials
No manufacturer dose exists for this use: these are amounts given in published trials, not recommendations.
What is it?
Lung surfactant is a thin layer of fats and proteins lining the air sacs. It lowers surface tension so the sacs stay open when a baby breathes out. Infants born very early make too little of it, and the result, respiratory distress syndrome (RDS), was once a leading cause of newborn death. Surfactant replacement given through a breathing tube changed that. The products that work best come from animal lungs and contain small amounts of surfactant proteins B and C; earlier synthetic surfactants were pure phospholipid and did less well. Lucinactant was built to close that gap without animal material, using a short designed peptide, sinapultide or KL4, that copies the pattern of water-loving and fat-loving parts in surfactant protein B.
The first human study, in 1996, treated 47 premature infants with established RDS; their oxygenation improved to near normal within 12 hours and no infant died of RDS. Two large prevention trials followed, published in 2005. In SELECT, 1,294 infants born at 32 weeks or less were given lucinactant, the protein-free synthetic colfosceril, or the cow-derived beractant within half an hour of birth. Lucinactant reduced RDS at 24 hours compared with colfosceril and reduced deaths from RDS by day 14 compared with both. In STAR, 252 infants born at 24 to 28 weeks received lucinactant or the pig-derived poractant alfa, and survival without bronchopulmonary dysplasia at 28 days was not worse with lucinactant. One-year follow-up of both trials found survival and neurological status at least as good as with the animal surfactants.
FDA approved Surfaxin on March 6, 2012 to prevent RDS in premature infants at high risk. The label gives 5.8 mL per kg of birth weight into the trachea, in four portions with the baby turned between them, up to four doses in the first 48 hours, and requires warming the vial before use. Reflux of the suspension up the breathing tube, pallor, tube obstruction and brief drops in oxygen or heart rate during dosing were the main problems. The European application had been withdrawn in 2006, and Drugs@FDA now lists the single Surfaxin product as discontinued.
Lucinactant was tried in other lung conditions. Dilute lavage helped infants with meconium aspiration and adults with acute respiratory distress syndrome in small pilot studies, but the US label warns that adults with ARDS treated by segmental bronchoscopic lavage had more serious adverse events. In a randomised trial of 165 infants with acute hypoxemic respiratory failure, fewer needed a second dose, but time on the ventilator was not shortened overall. A 2026 study gave it to 19 adults with COVID-19 ARDS without changing oxygenation. An aerosolised version, Aerosurf, delivered through nasal CPAP so babies need not be intubated, was tolerated in a 17-infant pilot and reached the lungs of monkeys, but has not been approved.
Lucinactant is a medicine with genuine phase 3 evidence that is no longer sold. The doses below come from the 2012 US label, marked discontinued, and from the trials; they describe a hospital treatment given through a breathing tube by neonatal teams and have no use outside that setting.
Mechanism of Action
Lucinactant replaces missing lung surfactant; its peptide, sinapultide, stands in for surfactant protein B, which helps the phospholipid film spread and stay stable.
Lowers surface tension
The phospholipid film keeps the air sacs from collapsing on breathing out, expanding the lungs and improving oxygenation in premature infants (PMID 8542150).
Protein B mimic
Sinapultide copies the alternating water- and fat-loving pattern of surfactant protein B (PMID 8542150).
Less inflammation
Reduced lung inflammation and neutrophil influx in lambs and mice and protected human airway cells from high oxygen (PMIDs 22821059, 16871629, 18391844).
No animal material
Entirely synthetic, unlike beractant and poractant alfa, which are extracted from cow and pig lungs (PMID 15805381).
Published Research
Studies of lucinactant (Surfaxin, KL4 surfactant, Aerosurf) read from their PubMed abstracts: the first infant study, the SELECT and STAR trials and their one-year follow-up, trials in respiratory failure, meconium aspiration and adult ARDS, the inhaled-form pilot, a cost analysis, animal and cell studies, and two reviews. A 2009 bronchopulmonary dysplasia trial whose title does not name the drug is listed under References.
SELECT: against colfosceril and beractant
1,294 infants of 32 weeks or less were randomised to lucinactant, colfosceril palmitate or beractant within 30 minutes of birth. RDS at 24 hours was 39.1% with lucinactant against 47.2% with colfosceril; RDS-related deaths by day 14 were 4.7% against 9.4% (colfosceril) and 10.5% (beractant). Bronchopulmonary dysplasia was less common than with colfosceril.
STAR: against poractant alfa
252 infants born at 24 to 28 weeks were randomised to lucinactant or poractant alfa within 30 minutes of birth. Survival without bronchopulmonary dysplasia at 28 days was 37.8% against 33.1%, meeting the noninferiority margin, with no differences in dosing complications or major complications of prematurity.
One-year follow-up of both trials
Following 1,546 infants to one year corrected age with under 2% lost, survival with lucinactant matched colfosceril and beractant in SELECT and was higher than with poractant alfa in STAR; rehospitalisation, respiratory illness and neurological status were similar. The trials gave lucinactant at 175 mg/kg of phospholipid.
First use in premature infants
Forty-seven premature infants with RDS were treated within four hours of birth. In the 39 analysed, the arterial-to-alveolar oxygen ratio rose from 0.14 to 0.40 by 12 hours, airway pressures fell, the lungs expanded on X-ray, 29 needed only one dose, and none died of RDS.
Infants with acute hypoxemic respiratory failure
In a placebo-controlled trial across 36 paediatric intensive care units, 165 ventilated infants up to two years old received intratracheal lucinactant 175 mg/kg or air. Fewer lucinactant infants needed a second dose (67% against 81%), but ventilation time did not fall overall (4.0 against 4.5 days); brief bradycardia and desaturation during dosing were more common.
Lavage for meconium aspiration
Twenty-two ventilated term or near-term infants with meconium aspiration were randomised two to one to lavage with dilute Surfaxin or standard care. Lavaged infants tended to come off the ventilator sooner (6.3 against 9.9 days) and improve oxygenation faster, without reaching significance, and the procedure was tolerated.
Segmental lavage in adult ARDS
Twelve adults with ARDS received dilute Surfaxin by bronchoscope into all 19 lung segments in three dosing schemes. All tolerated it and no serious adverse event was attributed to the procedure or drug; inspired oxygen fell from 0.80 to 0.52 and PEEP from 10.3 to 7.6 over 96 hours.
COVID-19 ARDS in adults
Nineteen adults with COVID-19-related ARDS received one or two intratracheal doses of about 80 mg phospholipid per kg lean body weight. Oxygenation and lung compliance did not change significantly over five days; seven patients died, six from later infection, and three had brief desaturation or regurgitation during dosing.
Aerosurf through nasal CPAP
Seventeen preterm infants at risk of RDS received aerosolised lucinactant through nasal CPAP for three hours, with up to three repeats in 48 hours. It was tolerated, with transient desaturation but no bradycardia; all survived, 29% later needed surfactant through a tube, and nebuliser output varied.
Reintubation costs
Using reintubation data from the 1,546 infants of the two phase 3 trials and 2010 US ventilation costs, infants given lucinactant were reintubated less often than those given beractant or poractant alfa, which the authors project as $160,013 to $252,203 saved per 100 infants treated.
Less lung inflammation in preterm lambs
Preterm lambs randomised to lucinactant, poractant alfa, beractant or no surfactant and ventilated for four hours all improved compliance with surfactant, but lucinactant lowered lung and blood inflammation markers, needed less ventilation for the same oxygenation and better preserved lung structure.
Protects mouse lungs
In mice exposed to high oxygen or bacterial endotoxin, KL4 surfactant given into the airway, unlike beractant or vehicle, blocked neutrophil entry into the air sacs and reduced lung injury and leakage; in cell assays it reduced neutrophil passage across endothelium.
Where the aerosol lands in monkeys
Radiolabelled aerosolised lucinactant given to three macaques through nasal CPAP for five to nine minutes deposited 11.4% in the lungs and 79.9% in the nose and mouth; within the lungs it spread evenly between central and peripheral regions.
Protects human airway cells from oxygen
Human airway epithelial monolayers treated with lucinactant, beractant or saline and exposed to 60% oxygen kept tighter barriers and better viability with either surfactant; lucinactant-treated cells released less IL-6 and never expressed matrix metalloproteinase 7, and showed less injury than beractant.
Drug profile at the end of phase 3
This review describes lucinactant, formerly KL4 surfactant, as phospholipids plus a peptide mimicking surfactant protein B, given into the trachea soon after birth, and summarises the two prevention trials; adverse events were transient and related to administration.
After approval
This review states that a meta-analysis found lucinactant as effective as animal-derived surfactants for preventing RDS, that laboratory work suggests it resists inactivation by oxidants and proteins better, and that its synthetic origin lowers infection and inflammation risks.
Dosing Data
The first row is the March 2012 US label for Surfaxin. The product is listed as discontinued, so the label explains the trials and is not a dose anyone can obtain. The other rows are what trials gave. All are given into the trachea or lungs by neonatal or intensive care teams.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
Unknown: we hold no regulator's label that says in what form Lucinactant is supplied. It is prepared and given by clinical staff, not bought and mixed at home: the next part says where.
Mixing a vial: a worked example
Nothing to mix at home, and no syringe units to work out: Lucinactant is prepared and given by clinical staff, in a neonatal intensive care unit.
In the carded trials it was given through a breathing tube into the lungs of premature babies within 30 minutes of birth.
Source: PMID 15805380 and PMID 15805381 (studies carded under Research below).
Storage before and after mixing
Unknown: no label on file says how Lucinactant is stored. It is kept and prepared by the hospital or clinic that gives it (see the part above); the home rules for a mixed vial in the mixing guide do not apply to it.
How it is taken
As the approved label gives it: Intratracheal, in four aliquots (Up to 4 doses, no more often than every 6 hours; Last US label (Surfaxin, discontinued): prevention of RDS in premature infants).
Source: Last FDA label of a product discontinued in the US (not a current US recommendation): the route and frequency of each row in Dosing Data below.
What to expect, and when
How long it stays in the body: a half-life of not studied in people. After about five half-lives almost none is left.
How long the doses were given: Last US label (Surfaxin, discontinued): prevention of RDS in premature infants: First 48 hours of life.
When effects appear: unknown; no source on this page gives a time to effect for Lucinactant. Results reported in the studies are under Published Research.
Source: half-life: Surfaxin (lucinactant) US prescribing information, March 2012 approval labeling (NDA 021746) on Drugs@FDA; not on DailyMed, as Surfaxin is listed as discontinued; Clinical Pharmacology; Last FDA label of a product discontinued in the US (not a current US recommendation), the duration of each row in Dosing Data below.
Side effects, and when to stop or get help
From the Side Effects section: Reflux of the suspension up the breathing tube, pallor, tube obstruction and pauses in dosing were the most common problems (Surfaxin label, 2012); Brief drops in oxygen saturation and heart rate during dosing, more often than with placebo or comparator surfactants (PMID 22791092; Surfaxin label, 2012); Transient desaturation with the aerosolised form (PMID 20455772); Desaturation or regurgitation during dosing in adults with COVID-19 ARDS (PMID 42536986). Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Lucinactant. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“From the trials and the 2012 US label”).
Interactions
Unknown: a PubMed search for human interaction studies of Lucinactant (reviewed 2026-10-28) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of Lucinactant products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Discontinued (US: Surfaxin, NDA 021746, approved March 6, 2012). Sport: Unsettled (S0 may apply).
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
From the trials and the 2012 US label.
Contraindications & Cautions
From the March 2012 US label, which listed no contraindications.
Legal Status
Lucinactant was approved in the US in 2012 and is now listed as discontinued; it was never authorised in the EU.
Frequently Asked Questions
?What is lucinactant?
A synthetic lung surfactant for premature babies: a suspension of phospholipids and the peptide sinapultide, which imitates surfactant protein B. It was sold in the US as Surfaxin.
?How did it compare with animal surfactants?
In the SELECT and STAR trials it prevented respiratory distress syndrome about as well as cow- and pig-derived surfactants, with fewer RDS deaths than beractant in SELECT, and one-year outcomes were at least as good.
?Is it still available?
No. FDA approved Surfaxin in 2012, and its only product is now listed as discontinued. It was never approved in Europe.
?What is Aerosurf?
An aerosolised form of lucinactant given through nasal CPAP, meant to spare babies a breathing tube. It was tolerated in a small pilot study but has not been approved.
?Does it work in adults?
Not convincingly. A small lavage study in adult ARDS was tolerated, but the US label warns of more serious adverse events in adults treated that way, and a 2026 COVID-19 ARDS study found no change in oxygenation.
?Is sinapultide sold on its own?
No approved product contains sinapultide alone. It was developed as part of lucinactant, and its effects in people come from studies of the whole surfactant.
References
- [clinical-trial] Moya FR, et al. "A multicenter, randomized, masked, comparison trial of lucinactant, colfosceril palmitate, and beractant for the prevention of respiratory distress syndrome among very preterm infants." Pediatrics, 2005;115(4):1018-29. PMID: 15805380.
- [clinical-trial] Sinha SK, et al. "A multicenter, randomized, controlled trial of lucinactant versus poractant alfa among very premature infants at high risk for respiratory distress syndrome." Pediatrics, 2005;115(4):1030-8. PMID: 15805381.
- [clinical-trial] Moya F, et al. "One-year follow-up of very preterm infants who received lucinactant for prevention of respiratory distress syndrome: results from 2 multicenter randomized, controlled trials." Pediatrics, 2007;119(6):e1361-70. PMID: 17533176.
- [clinical-trial] Cochrane CG, et al. "The efficacy and safety of KL4-surfactant in preterm infants with respiratory distress syndrome." Am J Respir Crit Care Med, 1996;153(1):404-10. PMID: 8542150.
- [clinical-trial] Thomas NJ, et al. "A pilot, randomized, controlled clinical trial of lucinactant, a peptide-containing synthetic surfactant, in infants with acute hypoxemic respiratory failure." Pediatr Crit Care Med, 2012;13(6):646-53. PMID: 22791092.
- [clinical-trial] Wiswell TE, et al. "A multicenter, randomized, controlled trial comparing Surfaxin (Lucinactant) lavage with standard care for treatment of meconium aspiration syndrome." Pediatrics, 2002;109(6):1081-7. PMID: 12042546.
- [clinical-trial] Wiswell TE, et al. "Bronchopulmonary segmental lavage with Surfaxin (KL(4)-surfactant) for acute respiratory distress syndrome." Am J Respir Crit Care Med, 1999;160(4):1188-95. PMID: 10508806.
- [clinical-trial] Huang YC, et al. "Lucinactant, a Synthetic Surfactant for the Treatment of Acute Respiratory Distress Syndrome Caused by COVID-19: Phase 1/2A Trial." JMIR Form Res, 2026;10:e77315. PMID: 42536986.
- [clinical-trial] Finer NN, et al. "An open label, pilot study of Aerosurf® combined with nCPAP to prevent RDS in preterm neonates." J Aerosol Med Pulm Drug Deliv, 2010;23(5):303-9. PMID: 20455772.
- [pubmed] Guardia CG, et al. "A pharmacoeconomic analysis of in-hospital costs resulting from reintubation in preterm infants treated with lucinactant, beractant, or poractant alfa." J Pediatr Pharmacol Ther, 2012;17(3):220-7. PMID: 23258964.
- [pubmed] Wolfson MR, et al. "Lucinactant attenuates pulmonary inflammatory response, preserves lung structure, and improves physiologic outcomes in a preterm lamb model of RDS." Pediatr Res, 2012;72(4):375-83. PMID: 22821059.
- [pubmed] Kinniry P, et al. "KL4-surfactant prevents hyperoxic and LPS-induced lung injury in mice." Pediatr Pulmonol, 2006;41(10):916-28. PMID: 16871629.
- [pubmed] Gregory TJ, et al. "Deposition of Aerosolized Lucinactant in Nonhuman Primates." J Aerosol Med Pulm Drug Deliv, 2020;33(1):21-33. PMID: 31436493.
- [pubmed] Zhu Y, et al. "KL4-surfactant (Lucinactant) protects human airway epithelium from hyperoxia." Pediatr Res, 2008;64(2):154-8. PMID: 18391844.
- [review] Moen MD, et al. "Lucinactant: in neonatal respiratory distress syndrome." Treat Respir Med, 2005;4(2):139-45; discussion 146-7. PMID: 15813666.
- [review] Jordan BK, et al. "Lucinactant for the prevention of respiratory distress syndrome in premature infants." Expert Rev Clin Pharmacol, 2013;6(2):115-21. PMID: 23473590.
- [clinical-trial] Laughon M, et al. "A pilot randomized, controlled trial of later treatment with a peptide-containing, synthetic surfactant for the prevention of bronchopulmonary dysplasia." Pediatrics, 2009;123(1):89-96. PMID: 19117865.
- [other] US FDA, Drugs@FDA (openFDA): SURFAXIN, NDA 021746, original approval March 6, 2012; marketing status discontinued. Read October 28, 2026.
- [other] European Medicines Agency, medicines list (JSON report, downloaded October 28, 2026): Surfaxin (sinapultide; dipalmitoylphosphatidylcholine; palmitoyl-oleoyl phosphatidylglycerol): marketing application withdrawn, withdrawal date June 7, 2006.
Sources & Citations
Every study on this page was read from its PubMed record on October 29, 2026. Doses, composition, warnings and adverse reactions come from the March 2012 Surfaxin label on Drugs@FDA; status from Drugs@FDA (openFDA) and the EMA medicines list. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.