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Evidence: LowProtein, not a peptide Clinical Trials Pipeline & In-Development

Zelpultide alfa

A lab-made copy of the lung's own immune protein SP-D, dripped down the breathing tube of very premature babies to try to prevent the chronic lung disease bronchopulmonary dysplasia. One small safety trial has been published, a 366-infant phase 2b/3 trial is recruiting in Europe, Israel and Argentina, and it is approved nowhere.

Zelpultide alfa (AT-100) is recombinant human surfactant protein D, a 355-amino-acid collectin made in human cells and assembled into 12-chain complexes (FDA GSRS UNII 96HS6QEW3X). In a phase 1b trial of 37 ventilated infants born at 23 to 28 weeks, doses of up to 6 mg/kg given through the breathing tube for up to seven days caused no safety signal the investigators tied to the drug; bronchopulmonary dysplasia occurred in 32.1% of treated infants against 66.7% after an air sham, in a trial too small to test benefit (PMID 41018057). A phase 2b/3 trial of 4 and 6 mg/kg in 366 infants has recruited since February 2025 (NCT06897839). It is approved nowhere.

Used in human trials: 2–6 mg/kg, once daily, up to 7 doses, intratracheal (Studied dose) Details ↓

Mechanism of action

Surfactant protein D is a collectin, an immune protein of the lung lining that latches onto sugars on the surface of bacteria and viruses, clumps them together for clearance and damps down lung inflammation. Animal-derived surfactants given to premature babies contain none of it, and very premature infants make little of their own. The trial investigators' rationale is that topping it up in the first days of ventilation could limit the inflammatory lung injury that leads to bronchopulmonary dysplasia (PMID 41018057). The drug is the full human protein, built in human cells so that its sugar chains and its 12-chain assembly match the native form (FDA GSRS UNII 96HS6QEW3X).

Primary uses

  • Investigational: preventing bronchopulmonary dysplasia in ventilated preterm infants (phase 2b/3, recruiting; phase 1b completed)
  • Investigational: ventilated adults with severe COVID-19 or community-acquired pneumonia (phase 1b, terminated, no results posted)

Typical dosing

Human studyPMID 41018057 2–6 mg/kg once daily, up to 7 doses (intratracheal), phase 1b

Used in human trials: 2, 4 or 6 mg/kg instilled through the breathing tube of ventilated preterm infants, two doses 24 hours apart in the escalation cohorts and once daily for up to seven days at 6 mg/kg in the last cohort (PMID 41018057). Given by neonatal intensive care teams inside a trial; a study amount, not a recommendation, and no trial has yet shown that it prevents lung disease. The recruiting phase 2b/3 trial compares 4 and 6 mg/kg daily for up to seven doses (NCT06897839).

Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, 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.

Regulatory status

Not approved anywhere: Drugs@FDA and the openFDA label endpoint hold no record for zelpultide alfa or AT-100 (searched November 4, 2026). ChEMBL still records a highest clinical phase of 1 (CHEMBL4650375), but Airway Therapeutics has registered three trials: the phase 1b trial in 37 preterm infants at risk of bronchopulmonary dysplasia in Spain and the United States (NCT04662151, completed May 2024, published as PMID 41018057), a phase 1b dose escalation in ventilated adults with severe COVID-19 or community-acquired pneumonia (NCT04659122, five enrolled, terminated February 2023, no results posted), and a phase 2b/3 trial of 4 and 6 mg/kg against an air sham in 366 high-risk preterm infants in Europe, Israel and Argentina (NCT06897839, recruiting since February 2025, primary completion estimated March 2028).

Status as of this entry's last review, November 4, 2026. Approvals, compounding rules and sport rules change; the regulatory tracker is checked more often.

What the studies show

One paper in PubMed names this drug: the phase 1b trial in premature babies. The developer's animal and laboratory papers describe a recombinant SP-D without saying it is this product, and other groups have made different recombinant SP-Ds, so those papers sit in References. The other two cards are registry records: the recruiting phase 2b/3 trial and a small adult study, neither with results.

Human · 2025

Phase 1b in ventilated preterm infants at risk of bronchopulmonary dysplasia

Thirty-seven infants born at 23 to 28 weeks, all on a ventilator and all already given a standard animal surfactant, were randomised three to one to the drug or an air sham through the breathing tube. Early cohorts stepped through 2, 4 and 6 mg/kg for up to two doses; a last cohort got the top tolerated dose daily for up to a week. The investigators judged 6 mg/kg safe. Almost every infant in both groups had at least one adverse event, as is usual at this age. Deaths were 21% on the drug and none after sham, none judged drug-related. Bronchopulmonary dysplasia occurred in 32.1% against 66.7%, bronchopulmonary dysplasia or death in 54% against 67%, and ventilation lasted 17.7 against 25.8 days. With so few infants and more deaths on the drug, those figures point to a larger trial, not to a benefit.

PMID 41018057

Registry · 2025

Phase 2b/3 in high-risk preterm infants, recruiting

A larger, double-blind follow-on trial planned for 366 intubated preterm infants at 49 hospitals in eight countries. In the first part infants are split three ways, 4 mg/kg, 6 mg/kg or an air sham, given through the breathing tube once a day for up to seven days; an independent committee then picks one dose for the second part, which tests it against sham. The main measure is moderate or severe bronchopulmonary dysplasia, or death, at 36 weeks' postmenstrual age (weeks of pregnancy plus weeks since birth). Recruiting since February 2025; the registry estimates primary completion in March 2028.

NCT06897839 · ClinicalTrials.gov record

Registry · 2021

Ventilated adults with severe COVID-19 or pneumonia, stopped after five patients

Airway Therapeutics planned an open-label dose escalation of 75 mg and then 150 mg daily through the breathing tube for up to seven days in adults on a ventilator with severe COVID-19 or community-acquired pneumonia. Five people were enrolled at one Cincinnati site between August 2021 and February 2023 before the study was ended, the registry giving 'study goals reached' as the reason. No results have been posted or published.

NCT04659122 · ClinicalTrials.gov record

References

  1. [clinical-trial] Alonso-Ojembarrena A, et al. "A phase 1b randomized, multicenter, dose determination trial of zelpultide alfa (recombinant human surfactant protein D) in preterm neonates at high risk of developing bronchopulmonary dysplasia." Front Pediatr, 2025;13:1639573. PMID: 41018057.
  2. [pubmed] Arroyo R, et al. "Evaluation of recombinant human SP-D in the rat premature lung model." Ann Anat, 2021;235:151670. PMID: 33444741.
  3. [pubmed] Arroyo R, et al. "Surfactant protein D and bronchopulmonary dysplasia: a new way to approach an old problem." Respir Res, 2021;22(1):141. PMID: 33964929.
  4. [pubmed] Arroyo R, et al. "Full-Length Recombinant hSP-D Binds and Inhibits SARS-CoV-2." Biomolecules, 2021;11(8). PMID: 34439781.
  5. [pubmed] De Luca D, et al. "Early life surfactant protein-D levels in bronchoalveolar lavage fluids of extremely preterm neonates." Am J Physiol Lung Cell Mol Physiol, 2023;325(4):L411-L418. PMID: 37489844.
  6. [clinicaltrials] ClinicalTrials.gov NCT06897839: "Randomized, Double-Blind Parallel-Group, Adaptive, Three-Arm, Phase 2b/3 Multicenter Study to Evaluate the Efficacy and Safety of Zelpultide Alfa in Preventing Bronchopulmonary Dysplasia (BPD) in High-Risk Preterm Neonates Compared to Standard of Care (SOC)" Airway Therapeutics, Inc. 366 infants planned at 49 sites in Spain, France, Italy, Poland, Israel, Argentina, Belgium and Germany; recruiting since February 3, 2025, primary completion estimated March 2028. Part 1 randomises intubated infants one to one to one to 4 mg/kg, 6 mg/kg or an air sham through the breathing tube every 24 hours for up to 7 doses; part 2 compares the chosen dose with sham. Primary endpoint: grade 2 or 3 bronchopulmonary dysplasia or death at 36 weeks' postmenstrual age. Registry record read November 4, 2026.
  7. [clinicaltrials] ClinicalTrials.gov NCT04662151: "A Phase 1b, Randomized, Blinded, Dose-Determined Study Evaluating the Safety and Tolerability Profile of Intervention With AT-100 (rhSP-D) in Preterm Neonates at High Risk for the Development of Bronchopulmonary Dysplasia (BPD)" Airway Therapeutics, Inc. 37 infants at 19 sites in Spain and the United States, September 2021 to May 2024, completed; intubated infants born at 23 to 28 weeks who had received poractant alfa, given intratracheal AT-100 or an air sham once daily for up to 2 doses (dose escalation) or up to 7 doses (top tolerated dose). No results posted; published in Frontiers in Pediatrics in 2025 (the trial paper is cited above). Registry record read November 4, 2026.
  8. [clinicaltrials] ClinicalTrials.gov NCT04659122: "Phase 1b Open-label, Single Arm, Cohort Dose Escalation Study Evaluating the Safety, Tolerability, and Feasibility of Intervention With AT-100 (rhSP-D) in Intubated Patients Receiving Invasive Mechanical Ventilation With Severe COVID-19 Infection or Respiratory Failure Secondary to Severe Community Acquired Pneumonia" Airway Therapeutics, Inc. Adults on mechanical ventilation, intratracheal AT-100 75 mg or 150 mg once daily for up to 7 doses; 5 enrolled at one site in Cincinnati, August 2021 to February 2023, terminated with the reason 'study goals reached'. No results posted. Registry record read November 4, 2026.
  9. [other] FDA Global Substance Registration System, Zelpultide alfa, UNII 96HS6QEW3X (protein; INN 12179, USAN JK-212, CAS 2245003-06-7, NCI Thesaurus C188542; other names AT-100, AT100, recombinant SP-D), read November 4, 2026: human pulmonary surfactant-associated protein D, a non-covalent quadruple trimer of 12 chains of 355 residues each, produced in human myelogenous leukaemia K562 cells (glycoform alfa, human GlycoExpress glycosylation). https://gsrs.ncats.nih.gov/ginas/app/beta/substances/96HS6QEW3X
  10. [other] ChEMBL molecule CHEMBL4650375 (ZELPULTIDE ALFA), read November 4, 2026: molecule type Protein; synonyms AT-100, AT100, recombinant SP-D; highest clinical phase recorded 1, for bronchopulmonary dysplasia (NCT04662151) and severe acute respiratory syndrome (NCT04659122). https://www.ebi.ac.uk/chembl/compound_report_card/CHEMBL4650375/
  11. [other] US FDA, Drugs@FDA and the drug label endpoint (openFDA), searched November 4, 2026: no application and no label record for zelpultide alfa or AT-100.

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Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.