What it is
LSALT is a synthetic tripeptide (Met-Arg-Trp) designed to inhibit DPEP-1, a membrane-bound enzyme on kidney peritubular capillaries and activated neutrophils. It blocks neutrophil adhesion to prevent acute kidney injury after cardiac surgery, with handling and oxidation chemistry specific to peptides.
Key takeaways
- LSALT is a three-amino-acid peptide (Met-Arg-Trp), not a small molecule, so its handling, storage, and oxidation chemistry are peptide-specific.
- DPEP-1 inhibition is an anti-adhesion strategy aimed at the neutrophil-endothelium interface, distinct from vasodilator or antioxidant approaches to AKI.
- Methionine and tryptophan in the sequence are the two residues most prone to oxidation; protect the N-terminal Met by avoiding saline-first reconstitution.
- For tripeptides, demand HPLC purity, MS identity, and a Trp-oxidation check on every Certificate of Analysis, because appearance is not a quality indicator.
- Central IRB approval is a procedural gate, not a clinical result; the real question is whether the Phase II hits its KDIGO-defined AKI incidence endpoint.
In this article
Arch Biopartners has cleared a Central Institutional Review Board (cIRB) approval that lets U.S. clinical sites join its Phase II trial of LSALT peptide (Met-Arg-Trp, also called Dipeptidase-1 / DPEP-1 inhibitor AB-001) for the prevention of cardiac surgery-associated acute kidney injury (CSA-AKI). Central IRB approval is a procedural milestone, not a clinical one, but it is the gate every U.S. site has been waiting on. With it, enrollment can expand beyond Canada, where the trial has already been running, and the dataset grows large enough to actually answer whether blocking DPEP-1 on the kidney's peritubular capillaries protects the tubules after cardiopulmonary bypass.
What LSALT peptide actually is
LSALT is a synthetic tripeptide: methionine-arginine-tryptophan. It was rationally designed to inhibit dipeptidase-1 (DPEP-1), the membrane-bound metallopeptidase that sits on the luminal surface of peritubular capillaries in the kidney and on the surface of activated neutrophils. DPEP-1 is not a receptor in the classical sense; it is a glycosylphosphatidylinositol-anchored ectoenzyme whose normal job is to hydrolyze leukotriene D4 (LTD4) and certain dipeptides. In ischemia-reperfusion, DPEP-1 is upregulated and acts as an adhesion molecule: neutrophils rolling on inflamed endothelium use DPEP-1 to stick, transmigrate, and start the inflammatory cascade that kills tubular epithelial cells in the hours after blood flow is restored.
By blocking DPEP-1, LSALT is intended to stop that neutrophil recruitment at the vascular step, before the cells ever reach the tubule. The peptide itself is short, hydrophilic, and has a short plasma half-life, which is a feature here: a researcher does not want systemic immunosuppression, only a transient block during the surgical window.
What the Phase II is actually testing
Arch's Phase II is a randomized, double-blind, placebo-controlled study in patients at elevated risk of CSA-AKI undergoing cardiac surgery with cardiopulmonary bypass. The primary efficacy endpoint is the incidence of AKI within roughly seven days post-surgery, defined by the standard KDIGO criteria (rise in serum creatinine and/or drop in urine output). Secondary endpoints include length of ICU stay, need for renal replacement therapy, and major adverse kidney events. The cIRB approval announced now lets U.S. centers use a single ethics review rather than negotiating site-by-site IRB approval, which is what had been slowing U.S. activation.
Why the mechanism matters beyond this trial
DPEP-1 as a target is interesting for two reasons that bench researchers should notice. First, it is mechanistically distinct from the usual suspects in AKI: it does not block oxidative injury directly, does not raise renal blood flow, and is not a vasodilator. It is an anti-adhesion strategy aimed at the neutrophil-endothelium interface. Second, the readout of DPEP-1 engagement is unusually clean because the substrate is known: DPEP-1 hydrolyzes a fluorogenic dipeptide substrate (for example, Ala-pNA or Gly-Leu-based reporters), so in vitro IC50 work is straightforward and reproducible across labs. The published preclinical work in rats and pigs showed reductions in neutrophil infiltration and serum creatinine when the peptide was dosed before ischemia. Those numbers are what the Phase II has to beat.
Practical angle for the bench
If you are reconstituting or storing LSALT-class peptides, the rules are unforgiving and worth following. Use sterile, non-pyrogenic water for injection or bacteriostatic water for stock; never reconstitute in saline first, because residual chloride and the lower pH of saline can accelerate oxidation of the methionine residue, and Met oxidation is exactly the degradation you cannot afford on a tripeptide whose N-terminal Met is part of the active pharmacophore. Aim for 1 mg/mL or lower stock concentration, aliquot into single-use vials, and store at -80 °C with no more than two freeze-thaw cycles. Lyophilized powder is stable at 2-8 °C for months and at -20 °C for years, but once reconstituted, plan to use within 30 days at 2-8 °C and always verify by HPLC or LC-MS rather than by appearance. Demand a Certificate of Analysis with each lot showing purity by HPLC (typically ≥95% for research-grade, ≥98% for clinical-grade), identity by MS, and a Trp-related impurity check, because tryptophan oxidation during synthesis or storage is the single most common silent failure mode for any Met-Arg-Trp sequence.
Frequently asked questions
What is LSALT peptide and what does it target?
LSALT (Met-Arg-Trp, also called AB-001) is a synthetic tripeptide that inhibits dipeptidase-1 (DPEP-1), a GPI-anchored ectoenzyme on kidney peritubular capillaries and activated neutrophils that mediates neutrophil adhesion in ischemia-reperfusion injury.
How does blocking DPEP-1 prevent CSA-AKI?
By inhibiting DPEP-1 on inflamed endothelium, LSALT reduces neutrophil rolling, adhesion, and transmigration into the renal interstitium, limiting the inflammatory cascade that damages tubular epithelial cells after cardiopulmonary bypass.
Why is central IRB approval a milestone for this trial?
Central IRB approval means a single ethics review covers all participating U.S. sites, removing the site-by-site bottleneck that had been slowing U.S. activation of Arch's Phase II CSA-AKI trial of LSALT peptide.
Prompted by this coverage at Google News →
Sources
- Bacteriostatic Water for Injection, USP , FDA/DailyMed label (0.9% benzyl alcohol)
- Duerkop et al., Biotechnol J 2018 , Impact of Cavitation, High Shear Stress and Air/Liquid Interfaces on Protein Aggregation
- Sigma-Aldrich (Merck) , Handling and Storage Guidelines for Peptides and Proteins
✔ Reviewed by Bryan Le, PharmD, RPh
Bryan is a licensed pharmacist (Doctor of Pharmacy, Registered Pharmacist). Reconstituting lyophilized preparations is core pharmacy practice, so he reviews The Lab’s content for technical accuracy and to keep it within a research-and-education scope, with no medical or dosing advice. View profile on LinkedIn.
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