Pegtarazimod (RLS-0071)_Dosage, benefits & legal status
Also known as RLS-0071, PA-dPEG24, PIC1, Peptide Inhibitor of Complement C1
A 15-residue peptide with a short PEG tail that stops the classical complement pathway at its first step and blunts neutrophil damage. Patient data so far are small and early.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Pegtarazimod (RLS-0071)?
Plain language first. The technical label stays, but it never stands alone.Overview
When a newborn's brain is starved of oxygen, or donor immune cells attack a transplant patient's tissues, part of the damage is thought to come from complement and from neutrophils, white cells that release toxic oxidants. Pegtarazimod is designed to calm both at once. In a placebo-controlled study of 30 healthy volunteers who inhaled a bacterial cell-wall toxin (LPS), the lower dose cut the LPS-driven rise in sputum neutrophils by about 43 to 50% against placebo (p=0.039). Patient data are early: 4 of 7 people with graft-versus-host disease that steroids had not controlled responded in an open-label study with no comparison group, and no controlled patient trial has reported a clinical benefit yet.
Pegtarazimod is a 15-residue peptide (IALILEPICCQERAA) carrying a discrete 24-unit PEG on its C-terminus, engineered from a region of the human astrovirus type 1 capsid (coat) protein by Neel Krishna and Kenji Cunnion's group and developed by ReAlta Life Sciences of Norfolk, Virginia. It binds the collagen-like region of C1q and mannose-binding lectin to block classical and lectin pathway activation, and it also inhibits myeloperoxidase, neutrophil extracellular trap (NET) formation and oxidant activity. It acts upstream of the site's other complement peptides, pegcetacoplan (a C3 blocker) and zilucoplan (a C5 blocker).
What it's used for
Nothing yet outside trials. It is given as an intravenous infusion in the hospital in phase 2 studies of newborn brain injury from lack of oxygen (HIE), steroid-refractory acute graft-versus-host disease and COPD flare-ups.
How does Pegtarazimod (RLS-0071) work?
What it does in the body, and where.Pegtarazimod damps two parts of the early immune response at once: complement and neutrophils.
- 01Stopping complement at the startComplement is a cascade of blood proteins that tags microbes and damaged cells and drives inflammation. Pegtarazimod binds the collagen-like stalk of C1q (and of mannose-binding lectin), so the classical and lectin pathways cannot start. Pegcetacoplan (C3) and zilucoplan (C5) act further down the same cascade.
- 02Disarming neutrophilsNeutrophils release myeloperoxidase, an enzyme that makes hypochlorous acid, and cast sticky DNA nets (NETs) that injure tissue. The peptide blocks myeloperoxidase reversibly and, through its two adjacent cysteines, dampens NET release and acts as an antioxidant.
- 03Fast and short-actingLevels peak at the end of an infusion and fall with an effective half-life of about 2 to 3 hours, and trials dose every 8 hours. After a single 40 mg/kg dose in healthy volunteers, classical complement activity was on average 37% lower at the end of the infusion.
A schematic of the compound's mechanism, not a diagnostic image.
What else is it used for?
Each group carries its own evidence level.Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
Healthy volunteers, first in human
Investigational- human-early56 adults given single doses of 2 to 120 mg/kg or 9 doses of up to 40 mg/kg: no serious adverse events or deaths.
- human-earlyDose-dependent classical complement inhibition (37% on average at the end of a single 40 mg/kg infusion) and myeloperoxidase binding showed the drug reaches its targets; no clinical outcome was tested.
Healthy volunteers, inhaled LPS challenge
Investigational- Human trial30 treated: sputum neutrophils at 6 hours lower on 10 mg/kg than on placebo (p=0.039), with lower myeloperoxidase (p=0.003) and neutrophil elastase (p=0.023).
- No dataStopped at 31 randomized of a planned 48 because of a COVID-19 surge, and the higher dose did no better than the lower one.
Patients, steroid-refractory acute graft-versus-host disease (2025 and 2026)
Investigational- human-earlyAURORA, open-label with ruxolitinib: 4 of 7 evaluable patients (57%) responded at day 28, with no severe drug-related adverse events among 8 enrolled.
- human-earlyIn a 2025 conference abstract, all of the first 6 patients, given 10 mg/kg every 8 hours for 7 days, improved in disease stage, and their plasma myeloperoxidase fell by a median of 68% (P=0.02); in 3 of 5 it rose again after treatment stopped, as gut disease worsened.
- No dataNo control group and background ruxolitinib, so how much of the response is due to pegtarazimod is unknown; the authors say efficacy needs further study.
Patients, COPD flare-ups (2026 abstract)
Investigational- human-early21 hospitalized patients (10 on drug, 11 on placebo): lower oxygen needs in the hospital persisting to 60 days and higher oxygen saturation, with a larger effect when the neutrophil-to-lymphocyte ratio was above 9.
- No dataA conference abstract with no p-values or effect sizes; no full paper yet.
Newborns with HIE (STAR)
Investigational- human-earlyBlood levels at 3 and 10 mg/kg matched animal and adult data, and myeloperoxidase was raised in newborns with HIE (more in severe cases), as was plasma cell-free DNA.
- No dataNo efficacy or safety results released; primary completion is estimated for December 2026.
It is often described as a 15-amino-acid peptide, leaving out the 24-unit PEG tail on its C-terminus that the 'peg-' in its name refers to; the 1,640 Da weight in the FDA substance record covers the peptide alone, so the full molecule is heavier. It comes from an astrovirus coat protein but was rearranged into a sequence not found in nature, rather than cut out of the virus intact. Lists of its trials often give NCT05298787 alongside the phase 2 studies; that is the phase 1 healthy-volunteer study, and the same lists miss the LPS challenge (NCT05351671) and the COPD flare-up trial (NCT06175065). The July 22, 2025 ReAlta announcement is reported as a development step; it covered published rat data in HIE. It is also summarized as having only phase 1 human evidence, but small phase 2 patient results appeared in 2025 and 2026, none yet showing a benefit in a peer-reviewed controlled trial. Site counts for STAR differ: ReAlta says 13 US neonatal units, and the registry lists 15 with one withdrawn. The COPD study planned 24 and enrolled 21.
The published record
Papers and trials about Pegtarazimod (RLS-0071)
9 papers tagged human · 3 not reviews or lab · 0 clinical trial publications
6 registered trials · none with posted results
Furthest stage reached: Phase 2, under way
Counted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count. 10 papers and 6 trials indexed in detail.
At a glance
Four things to know about Pegtarazimod (RLS-0071)
Evidence
Investigational
Category
Immune support
Common vial
Varies
Half-life
About 2 to 3 hours (effective, healthy volunteers)
How much, and do you cycle it?
The range, and whether you take breaks.10 mg/kg IV every 8 hours (phase 2 trials), every 8 hours for 3 to 14 days (trials). Short courses of 3 to 14 days Trial dose
Each trial gives a fixed course during an acute illness: 72 hours in newborns with HIE, 3 to 5 days in a COPD flare-up and 7 to 14 days in graft-versus-host disease.
How long does it stay in the body?
The half-life, and where the figure comes from.About 2 to 3 hours (effective, healthy volunteers)Human study
Effective half-life in the repeated-dose groups. Levels peak at the end of the infusion and follow two-compartment kinetics with rapid spread into tissue; exposure rose in proportion to dose from 2 to 40 mg/kg and more steeply at 120 mg/kg. In the LPS study, median peak levels 5 minutes after infusion were 57.5 µg/mL at 10 mg/kg and 772.0 µg/mL after a 120 mg/kg load. Plasma half-life may not reflect how long it acts in tissue; in rats it acts within 30 seconds and has a functional half-life of about 4 hours. How it is cleared has not been published.
Source: Goss J et al., Translational Medicine Communications 2023
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How is it given?
Dosing context and source notes.Given in hospital from a prepared product, so there is nothing to mix.
Label range: 3 up to 20 mg/kg per dose. ClinicalTrials.gov, AURORA (NCT06343792)
Dosed by body weight as an intravenous infusion over about 8 to 10 minutes (20 minutes for the largest single dose), every 8 hours. Patient trials: 3 or 10 mg/kg for 10 doses over 72 hours in newborns being cooled for HIE (STAR); 10 or 20 mg/kg for 7 or 14 days in graft-versus-host disease, some groups switching to once daily for the second week, most with ruxolitinib (AURORA); 10 mg/kg for 3 to 5 days in COPD flare-ups, added to usual care. Healthy volunteers received single doses of 2 to 120 mg/kg and 9 doses of 2 to 40 mg/kg every 8 hours; the LPS study gave 10 mg/kg three times, or a 120 mg/kg load and then 40 mg/kg twice. The STAR registry lists a unit strength of 10 mg/mL; vial size and other formulation details are not public. A hospital infusion dosed by body weight, so there is no vial draw to calculate.
How do you store it?
Before mixing, and after.Given in a hospital or trial clinic, so the pharmacy stores it.
Pegtarazimod (RLS-0071) goes into a vein and is prepared by hospital, clinic or trial pharmacy staff, following the product label or the trial protocol. Some products like this are ready-made solutions and others are powders mixed just before use, often with hours rather than weeks of shelf life once prepared. It is not a medicine people store at home.
What are the side effects and cautions?
Known cautions and warnings for this compound.Solubility, computed: 33% charged residues, 73% hydrophobic. Water usually sufficient.
A first-pass rule from peptide manufacturers' guidance. It does not account for disulfide bridges, salt form or how the powder was dried, and it predicts what should be easy rather than what will happen in your vial.
Who should avoid it
- Not studied in people allergic to polyethylene glycol (PEG): excluded from the graft-versus-host disease and COPD trials
- Not studied in pregnancy or breastfeeding
- Not studied in active sepsis, uncontrolled gut infection, severe kidney disease or dialysis
- Not studied in people on a ventilator, with severe COPD flare-ups or with asthma
- Not studied in newborns born before 36 weeks or weighing 1,800 g or less
Stop and get help
- Swelling of the face or throat, wheezing or a widespread rash during an infusion
- Pain or swelling where the drip enters the vein (one healthy volunteer stopped for fluid leaking at the catheter site)
Common effects
- Headache was the most common side effect in the first-in-human study (56 healthy adults, 42 on drug), with side effects similar to placebo
- In the LPS challenge study, 5 of 10 on the lower dose and 8 of 10 on the higher dose had a side effect, against 9 of 10 on placebo; all were mild to moderate and none serious, but events judged related to the drug affected 3 and 7 of 10 on the two doses against 4 of 10 on placebo
- One volunteer stopped for fluid leaking around the drip; one given 120 mg/kg had a QTc rise of over 30 ms that stayed under 450 ms
- Antibody tests were positive in 5 healthy volunteers (4 confirmed), including at baseline and on placebo, possibly because the test also detects anti-PEG antibodies; one arose on treatment and cleared by day 90
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Pegtarazimod (RLS-0071) approved?
And where the numbers on this page come from.No. Pegtarazimod (RLS-0071) is not approved anywhere and is currently in company-run clinical trials. There is no legal route to obtain it outside a trial.
- Approval statusInvestigational
- RouteInto a vein (short infusion every 8 hours)
- Checked16 October 2026
- DoseFrom published clinical trials. Not approved by a regulator for this dose.
- Vial sizeFrom what vendors typically list; not a recommendation.
- SourcesFDA GSRS substance record, pegtarazimod (UNII 7AUD376O4W)FDA orphan drug designation, neonatal HIE (January 29, 2020)Goss J et al., Translational Medicine Communications 2023;8:1Hair P et al., ERJ Open Research 2024;10(4):01006-2023Holzmuller V et al., Journal of Clinical Investigation 2026;136(19):e205864Zeiser R et al., Blood 2025;146(Suppl 1):2462 (ASH abstract)Criner GJ et al., American Journal of Respiratory and Critical Care Medicine 2026;212(Suppl 1) (ATS abstract)Krishna NK, Cunnion KM, Parker GA, Frontiers in Immunology 2022;13:752315ClinicalTrials.gov, STAR (NCT05778188)ClinicalTrials.gov, AURORA (NCT06343792)ClinicalTrials.gov, NCT06175065ReAlta Life Sciences, FDA Fast Track for HIE (June 23, 2022)ReAlta Life Sciences, FDA Orphan Drug and Fast Track for graft-versus-host disease (August 19, 2024)EMA orphan designation EU/3/25/3111
What has happened recently
Not approved anywhere. The FDA granted orphan drug designation for neonatal hypoxic-ischemic encephalopathy on January 29, 2020, under the name Peptide Inhibitor of Complement C1, and ReAlta announced Fast Track for the same use on June 23, 2022; the company also reports an EU orphan designation for HIE. On August 19, 2024, ReAlta announced FDA Orphan Drug and Fast Track designations for hospitalized patients with steroid-refractory acute graft-versus-host disease, and the EU granted orphan designation for graft-versus-host disease (EU/3/25/3111) on August 22, 2025. First human dosing was in January 2021 (announced February 16, 2021), and phase 2 trials followed in HIE (STAR, from July 27, 2023), COPD flare-ups (from January 25, 2024) and graft-versus-host disease (AURORA, from August 31, 2024). The INN pegtarazimod was proposed in WHO list 128 (published January 20, 2023) and is also a USAN. ReAlta closed a $40 million financing on April 8, 2026, to advance the HIE program.
You can compare this against the whole library, or read how to check a seller.
What else is like Pegtarazimod (RLS-0071)?
Others in Immune support, side by side.If you're weighing Pegtarazimod (RLS-0071), it's worth reading Pexiganan, Splenopentin, and Thymopentin (TP-5) in the same class.
A 15-residue peptide with a short PEG tail that stops the classical complement pathway at its first step and blunts neutrophil damage. Patient data so far are small and early.
- Dose
- 10 mg/kg IV every 8 hours (phase 2 trials)
- How often
- Every 8 hours for 3 to 14 days (trials)
A magainin-based antimicrobial cream, tested twice for diabetic foot infections and never approved.
- Dose
- 0.8% cream twice daily (last trials)
- How often
- Twice daily for 14 days (trials)
A five-amino-acid spleen peptide, sold on an evidence base almost nobody has read.
- Dose
- Research only
- How often
- Not established
Five amino acids that carry the whole activity of a thymus hormone.
- Dose
- 50 mg per dose
- How often
- 3x per week
Guides for this compound
- How to Reconstitute a Peptide
Mix peptide powder with bacteriostatic water, step by step.
- How to Read an Insulin Syringe
Read the units, convert to millilitres, and draw the exact dose.
- mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
- How to Read a Peptide COA
What the purity number does and does not tell you, and how to spot an edited report.
- How to Vet a Peptide Vendor
Independent COAs, HPLC purity, and the red flags that mean walk away.
Sources
- FDA GSRS substance record, pegtarazimod (UNII 7AUD376O4W)(2026)Sequence IALILEPICCQERAA with a C-terminal PEG-24 in its chemical names; CAS 2056232-82-5; INN list 128 and USAN; codes RLS-0071 and PA-dPEG24; formula and weight for the peptide only.
- FDA orphan drug designation, neonatal HIE (January 29, 2020)(2020)Designated as Peptide Inhibitor of Complement C1; sponsor ReAlta Life Sciences, Norfolk, Virginia.
- Goss J et al., Translational Medicine Communications 2023;8:1(2023)56 healthy adults given 2 to 120 mg/kg IV: no serious adverse events, headache most common; effective half-life about 2 to 3 hours; classical complement inhibition and myeloperoxidase binding.
- Hair P et al., ERJ Open Research 2024;10(4):01006-2023(2024)Inhaled LPS challenge, 30 treated: sputum neutrophils at 6 hours lower on 10 mg/kg than placebo (p=0.039); myeloperoxidase lower (p=0.003).
- Holzmuller V et al., Journal of Clinical Investigation 2026;136(19):e205864(2026)Limited graft-versus-host disease death and severity in mice; in AURORA, 4 of 7 evaluable patients responded at day 28, open-label, with ruxolitinib.
- Zeiser R et al., Blood 2025;146(Suppl 1):2462 (ASH abstract)(2025)First 6 graft-versus-host disease patients at 10 mg/kg every 8 hours for 7 days: disease stage improved in 6 of 6; plasma myeloperoxidase down 68% (P=0.02).
- Criner GJ et al., American Journal of Respiratory and Critical Care Medicine 2026;212(Suppl 1) (ATS abstract)(2026)21 hospitalized patients with COPD flare-ups (10 on drug): lower oxygen needs persisting to 60 days; no p-values reported.
- Krishna NK, Cunnion KM, Parker GA, Frontiers in Immunology 2022;13:752315(2022)Engineered from the human astrovirus type 1 coat protein; a C-terminal PEG24 made it soluble and kept full activity; targets C1q, myeloperoxidase and NETs.
- ClinicalTrials.gov, STAR (NCT05778188)(2026)Phase 2 in newborns with moderate or severe HIE: 3 or 10 mg/kg every 8 hours for 72 hours with cooling, against placebo; estimated 70; recruiting.
- ClinicalTrials.gov, AURORA (NCT06343792)(2026)Open-label phase 2 in hospitalized steroid-refractory acute graft-versus-host disease: 10 or 20 mg/kg every 8 hours for 7 or 14 days; estimated 66.
- ClinicalTrials.gov, NCT06175065(2026)Phase 2a, placebo-controlled: 10 mg/kg every 8 hours for 3 to 5 days in hospitalized COPD flare-ups.
- ReAlta Life Sciences, FDA Fast Track for HIE (June 23, 2022)(2022)Fast Track for HIE in newborns; FDA and EU orphan designations for HIE held.
- ReAlta Life Sciences, FDA Orphan Drug and Fast Track for graft-versus-host disease (August 19, 2024)(2024)Both designations for hospitalized patients with steroid-refractory acute graft-versus-host disease.
- EMA orphan designation EU/3/25/3111(2025)Pegtarazimod designated for treatment of graft-versus-host disease on August 22, 2025.
Beyond these, 16 records are indexed. Browse the records