Reltecimod (AB103)_Dosage, benefits & legal status
Also known as AB103, AB-103, p2TA, reltecimod sodium, reltecimod TFA
A short piece of the CD28 receptor meant to calm the immune storm in flesh-eating infections. Its phase 3 missed its main goal (48.6% against 39.9%, P=0.135), and it was never approved.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Reltecimod (AB103)?
Plain language first. The technical label stays, but it never stands alone.Overview
Necrotizing soft tissue infection, often called flesh-eating disease, can set off an immune overreaction that shuts down organs even after surgeons cut away the infected tissue, and reltecimod was designed to calm that overreaction with one infusion. In the ACCUTE phase 3 (290 patients), 48.6% met a combined measure of success against 39.9% on placebo, a difference that was not statistically significant (P=0.135); only narrower analyses reached significance, such as a per-protocol analysis (54.3% against 40.3%, P=0.021). The FDA accepted the application for review in 2020, but it was never approved, and the developer reportedly shut down in May 2022.
Reltecimod is a linear decapeptide, H-D-Ala-Ser-Pro-Met-Leu-Val-Ala-Tyr-Asp-D-Ala-OH: residues 8 to 15 of human CD28 (SPMLVAYD) with a D-alanine added at each end. Atox Bio describes it as a CD28 mimetic that binds the dimer interface of CD28 on T cells, dampening the costimulatory signal behind the cytokine surge in severe bacterial infection, though EMA notes the mechanism is not fully understood. Given as a single 0.5 mg/kg intravenous dose in necrotizing soft tissue infection (NSTI), it missed its primary endpoint in the primary analysis of the ACCUTE phase 3, and the US application filed under accelerated approval never led to an approval.
What it's used for
Nothing today. It was tested as a single infusion, alongside surgery and antibiotics, to limit organ failure in flesh-eating soft tissue infections, and was never approved.
How does Reltecimod (AB103) work?
What it does in the body, and where.Reltecimod copies a small piece of CD28, a switch that T cells use to amplify their response, to turn down an immune overreaction.
- 01The overreactionIn severe bacterial infections, bacterial toxins, including superantigens, and the body's own signals overstimulate T cells, partly through CD28, a receptor that works as a pair (a homodimer). The result can be a surge of cytokines that damages organs.
- 02A copied pieceReltecimod is residues 8 to 15 of human CD28, the stretch at the interface where two CD28 molecules meet, with a D-alanine added at each end. Atox Bio says it binds that interface on T cells and calls it host-oriented and pathogen-agnostic: it acts on the immune response, not on the bacteria.
- 03Turning it downOccupying the interface is meant to dampen CD28 signaling rather than block it outright, lowering the cytokine surge while surgery and antibiotics deal with the infection. EMA notes the mechanism is not fully understood. Its half-life is only minutes, so the single dose was meant to act at the start of the inflammatory cascade.
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.
Flesh-eating infection (ACCUTE phase 3)
tested-and-failed- Human trial290 patients: 48.6% (69 of 142) against 39.9% (59 of 148) met the primary composite in the primary analysis (P=0.135).
- Human trialPrespecified per-protocol analysis, 17 excluded before unblinding: 54.3% against 40.3% (P=0.021); organ dysfunction resolved by day 14 in 70.9% against 53.4% (P=0.005).
- No dataOn the primary endpoint, significance came only in subsets, though organ dysfunction resolution, a secondary endpoint, was significant in the full primary population (65.1% against 52.6%, P=0.041); the company's own clinically evaluable subset, with 13 excluded, gave a different figure, 52.6% against 40.3% (P=0.039).
ACCUTE registry results
tested-and-failed- Human trialUS patients only (135 against 138): 67 against 50 met the primary endpoint (P=0.025), listed as a secondary analysis.
- Human trialOrgan dysfunction resolved by day 14 in 87 of 135 against 74 of 138 (P=0.069), not significant; discharge to a favorable location 80 against 64 (P=0.033).
- Human trialDeaths through day 90: 24 of 135 against 29 of 138 (HR 0.85, 95% CI 0.50 to 1.46; P=0.554).
Kidney injury from sepsis (phase 3)
tested-and-failed- Human trial58 patients before termination for very slow enrollment: 20 of 28 against 23 of 30 were alive, off dialysis and had lost less than 37% of kidney filtration (eGFR) at day 28 (P=0.649).
Phase 2 safety and blood levels
Investigational- Human trial43 patients with NSTI randomized to 0.25 mg/kg (15), 0.5 mg/kg (17) or placebo (11); at least one adverse event by day 7 in 14 of 15, 16 of 17 and 9 of 11; deaths 1, 1 and 2.
- Human trialMedian half-life 2.61 minutes at 0.25 mg/kg and 4.89 minutes at 0.5 mg/kg; peak levels 899 and 1,484 ng/mL.
FDA review
Investigational- RegulatoryThe FDA accepted the NDA for filing under Accelerated Approval, announced December 10, 2020, with a PDUFA goal date of September 30, 2021.
- No dataNo FDA decision has been made public in a primary source; a 2022 Israeli press report said the FDA asked for another trial and Atox Bio closed.
ACCUTE is often reported as a positive trial, but it missed its primary endpoint in the primary analysis (48.6% against 39.9%, P=0.135); significance on that endpoint came only in narrower analyses: a prespecified per-protocol analysis that excluded 17 patients (54.3% against 40.3%, P=0.021) and a US-only analysis in the registry results (67 of 135 against 50 of 138, P=0.025). The company's July 2020 release used a different subset, a clinically evaluable population with 13 excluded (52.6% against 40.3%, P=0.039), and that figure is sometimes quoted as the trial result. Its human evidence is often described as substantial, while summaries leave out that the FDA accepted an application with a September 30, 2021, goal date and the drug was never approved, that the kidney injury phase 3 was terminated with no benefit, and that the developer reportedly closed in May 2022. That kidney trial is sometimes called a phase 2; the registry lists it as phase 3. Serious adverse events are reported as 20.3% against 17.0% in the company's topline and 30.77% against 27.21% in the later registry results. The 15% mortality in both groups is the paper's day-28 figure; the registry counts deaths through day 90 (16.78% against 19.73%).
The published record
Papers and trials about Reltecimod (AB103)
14 papers tagged human · 6 not reviews or lab · 4 clinical trial publications
4 registered trials · 4 with posted results
Furthest stage reached: Phase 3, results posted
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.
At a glance
Four things to know about Reltecimod (AB103)
Evidence
Investigational
Category
Immune support
Common vial
Varies
Half-life
2.61 to 4.89 minutes (phase 2 medians)
How much, and do you cycle it?
The range, and whether you take breaks.0.5 mg/kg once, as a 10-minute infusion (phase 3 trial), once. Single dose Trial dose
Given once, within hours of diagnosis, to act at the start of the inflammatory cascade; no trial repeated it.
How long does it stay in the body?
The half-life, and where the figure comes from.2.61 to 4.89 minutes (phase 2 medians)Trial protocol
Apparent terminal half-life after a single infusion in patients with necrotizing soft tissue infection: median 2.61 minutes (range 1.28 to 18.99) at 0.25 mg/kg and 4.89 minutes (1.53 to 14.16) at 0.5 mg/kg. Peak levels were 899 and 1,484 ng/mL and clearance 29.42 and 29.55 mL/min/kg. The single dose was meant to act at the start of the inflammatory cascade, not to keep levels up. How it is eliminated has not been reported.
Source: ClinicalTrials.gov, NCT01417780 posted results (phase 2)
You can compare this against the whole library to see where it sits.
How is it given?
Dosing context and source notes.Given in hospital from a prepared product, so there is nothing to mix.
Trial dose: 0.5 mg/kg per dose. ClinicalTrials.gov, ACCUTE (NCT02469857)
A single 0.5 mg/kg dose into a vein as a 10-minute infusion, given within 6 hours of diagnosis in ACCUTE, alongside surgery, antibiotics and intensive care; placebo was saline. The kidney injury phase 3 used the same dose at 1 mg/mL over about 10 minutes, and the phase 2 compared 0.25 and 0.5 mg/kg. No commercial product was ever made, and there is no kidney or liver dose guidance. It was a one-time hospital dose set by body weight in a program that has ended, so the calculator starts with an empty dose field.
How do you store it?
Before mixing, and after.Given in a hospital or trial clinic, so the pharmacy stores it.
Reltecimod (AB103) 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: 30% charged residues, 70% 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 children under 12: ACCUTE enrolled patients aged 12 and up
- Not studied in pregnancy or breastfeeding: no data exist
- Not studied without surgery or without organ dysfunction: ACCUTE required surgically confirmed infection and a modified SOFA score of 3 or more
- Not studied as repeated doses: every trial gave a single infusion
- Use outside a trial: it was never approved, and what is sold online is a research chemical (a TFA salt), not a medical product
Stop and get help
- Swelling of the face or throat, a rash or trouble breathing during the infusion
- Spreading pain, swelling or skin discoloration, fever or confusion: signs the infection is advancing and needs surgery and antibiotics, not this drug
Common effects
- Any adverse event in 104 of 143 on reltecimod against 96 of 147 on placebo, in critically ill patients after surgery (ACCUTE registry results)
- Serious adverse events in 44 of 143 (30.77%) against 40 of 147 (27.21%); the company's 2020 topline gave 20.3% against 17.0%
- Anemia 5.59% against 4.08%, atrial fibrillation 4.90% against 5.44%, diarrhea 4.20% against 5.44% and pneumonia 3.50% against 7.48%
- Deaths 24 of 143 (16.78%) against 29 of 147 (19.73%); secondary infections in 30 against 32
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Reltecimod (AB103) approved?
And where the numbers on this page come from.No. Reltecimod (AB103) was never approved, and its development has ended. There is no legal route to obtain it as a medicine.
- Approval statusInvestigational
- RouteInto a vein (single 10-minute infusion), trial only
- Checked21 October 2026
- DoseFrom published clinical trials. Not approved by a regulator for this dose.
- Vial sizeFrom what vendors typically list; not a recommendation.
- SourcesBulger EM et al., Annals of Surgery 2020;272:469-478 (ACCUTE)ClinicalTrials.gov, ACCUTE (NCT02469857)ClinicalTrials.gov, phase 2 (NCT01417780)ClinicalTrials.gov, sepsis kidney injury phase 3 (NCT03403751)FDA GSRS substance record, reltecimod (UNII U00J02UY29)EMA, orphan designation EU/3/14/1294FDA orphan drug designation, reltecimodAtox Bio, NDA accepted for filing (PR Newswire, December 10, 2020)Atox Bio, ACCUTE topline (BioSpace, July 10, 2020)NCBiotech, FDA accepts Atox Bio's application (December 22, 2020)Arix Bioscience, interim results (2021)Startup Nation Central, Atox Bio company pageDrugs.com, reltecimod approval history
What has happened recently
Never approved anywhere. Atox Bio of Ness Ziona, Israel, founded in 2003 on research by Raymond Kaempfer and Gila Arad at the Hebrew University of Jerusalem, developed it with BARDA funding under a 2014 contract worth up to $24 million. The FDA granted orphan drug designation for necrotizing soft tissue infections on October 12, 2011, the EU granted orphan designation EU/3/14/1294 on July 29, 2014, and the FDA also gave it Fast Track status. After the ACCUTE phase 3, Atox submitted an NDA under the Accelerated Approval program, with resolution of organ dysfunction as the basis, for suspected organ dysfunction or failure in patients 12 and older with NSTI; on December 10, 2020, it announced that the FDA had accepted the application for filing, with a PDUFA goal date of September 30, 2021. The FDA's decision has not been made public in a primary source. An Israeli press report in Globes on May 25, 2022, cited by Startup Nation Central, said the FDA had asked for an additional trial and that Atox Bio ceased operations in May 2022; the investor Arix Bioscience had already cut the value of its holding by GBP 4.1 million to GBP 1.8 million in the half-year to June 30, 2021. A separate phase 3 in sepsis-associated kidney injury was terminated for slow enrollment, with primary completion on December 14, 2019.
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What else is like Reltecimod (AB103)?
Others in Immune support, side by side.If you're weighing Reltecimod (AB103), it's worth reading Voclosporin (Lupkynis), Cyclosporine (Sandimmune, Restasis), and Omiganan (MBI-226) in the same class.
A short piece of the CD28 receptor meant to calm the immune storm in flesh-eating infections. Its phase 3 missed its main goal (48.6% against 39.9%, P=0.135), and it was never approved.
- Dose
- 0.5 mg/kg once, as a 10-minute infusion (phase 3 trial)
- How often
- Once
Cyclosporine with one extra carbon on its first residue, approved in the US in 2021 for lupus that attacks the kidneys. Added to standard treatment, it nearly doubled full kidney responses at one year.
- Dose
- 23.7 mg (three 7.9 mg capsules) per dose (label)
- How often
- Twice daily, about 12 hours apart, on an empty stomach
A ring of 11 unusual amino acids from a soil fungus, approved for transplants in 1983 and as dry-eye drops since 2002. The drops barely reach the blood; the capsules and infusion carry boxed warnings.
- Dose
- One drop in each eye (eye drops, label)
- How often
- Twice daily
A short, tryptophan- and arginine-rich peptide gel that disrupts microbial membranes. Two catheter-site phase 3 trials missed their primary endpoints, and its two rosacea phase 3 trials split, one positive and one negative.
- Dose
- 1% gel at catheter sites, 1.6% gel on rosacea (phase 3 trials)
- How often
- Each dressing change (catheters) or once daily (rosacea)
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
- Bulger EM et al., Annals of Surgery 2020;272:469-478 (ACCUTE)(2020)290 patients with NSTI: 48.6% against 39.9% responders in the primary (mITT) analysis (P=0.135); 54.3% against 40.3% per protocol (P=0.021); organ dysfunction resolved by day 14 in 65.1% against 52.6% (P=0.041).
- ClinicalTrials.gov, ACCUTE (NCT02469857)(2021)Single 0.5 mg/kg IV dose; 143 against 147 treated; serious adverse events 30.77% against 27.21%; US-only analysis 67 of 135 against 50 of 138 (P=0.025).
- ClinicalTrials.gov, phase 2 (NCT01417780)(2021)43 patients randomized to 0.25 or 0.5 mg/kg or placebo; median half-life 2.61 and 4.89 minutes; earlier code p2TA.
- ClinicalTrials.gov, sepsis kidney injury phase 3 (NCT03403751)(2021)Terminated for slow enrollment after 58 patients; 20 of 28 against 23 of 30 free of lasting kidney damage at day 28 (P=0.649).
- FDA GSRS substance record, reltecimod (UNII U00J02UY29)(2026)D-alanyl-CD28(8-15)-D-alanine; C46H72N10O15S, MW 1037.19; CAS 1447799-33-8; target CD28; codes AB103 and AB-103.
- EMA, orphan designation EU/3/14/1294(2014)Sequence H-D-Ala-Ser-Pro-Met-Leu-Val-Ala-Tyr-Asp-D-Ala-OH as the sodium acetate salt; designated July 29, 2014, for necrotizing soft tissue infections; mechanism not fully understood.
- FDA orphan drug designation, reltecimod(2011)Designated October 12, 2011, for treatment of necrotizing soft tissue infections (Atox Bio); not approved for that use.
- Atox Bio, NDA accepted for filing (PR Newswire, December 10, 2020)(2020)NDA under the Accelerated Approval program; PDUFA goal date September 30, 2021; proposed for patients 12 and older with NSTI; Fast Track and orphan status.
- Atox Bio, ACCUTE topline (BioSpace, July 10, 2020)(2020)Clinically evaluable population with 13 excluded: 52.6% against 40.3% (P=0.039); single 10-minute infusion; serious adverse events 20.3% against 17.0%.
- NCBiotech, FDA accepts Atox Bio's application (December 22, 2020)(2020)Founded in 2003 on Hebrew University research; BARDA contract worth up to $24 million; septic shock named as a possible future indication.
- Arix Bioscience, interim results (2021)(2021)Described the NDA as filed in December 2020; holding cut by GBP 4.1 million to GBP 1.8 million, citing the likelihood of gaining approval.
- Startup Nation Central, Atox Bio company page(2022)Ceased operations in May 2022 after the FDA asked for an additional trial, citing Globes (May 25, 2022). Secondary source.
- Drugs.com, reltecimod approval history(2026)Not FDA approved.
Beyond these, 32 records are indexed. Browse the records