Urodilatin

Urodilatin was first isolated and structurally characterized from human urine in 1988 by Schulz-Knappe, Forssmann, and colleagues (Klinische Wochenschrift, 1988), who identified it as a distinct 32-amino-acid natriuretic peptide produced locally within kidney distal tubule cells — a genuinely separate processing product of the same precursor (pro-ANP) that also generates circulating atrial natriuretic peptide (ANP), but cleaved at a different site to yield a peptide with four additional N-terminal residues (Thr-Ala-Pro-Arg) compared to ANP itself.

Chemically, urodilatin has molecular formula C145H234N52O44S3, molecular weight approximately 3,506 g/mol, CAS number 115966-23-9, PubChem CID 405116874. Its sequence contains an internal disulfide bridge between cysteine residues 11 and 27, forming the same characteristic ring structure shared across the natriuretic peptide family (including Nesiritide/BNP, also built on this site).

At Verified Peptides, we want to note that urodilatin's synthetic pharmaceutical form was developed under the International Nonproprietary Name (INN) ularitide, and essentially all of the substantial clinical trial literature on this peptide uses that name. We use "Urodilatin" and "ularitide" interchangeably in this profile to reflect how the compound is discussed across both its physiological-discovery literature (which uses urodilatin) and its clinical-development literature (which uses ularitide).

Urodilatin's physiological role was uncovered through a genuinely distinctive research approach: rather than being identified through blood-based hormone assays as most circulating peptide hormones are, it was specifically isolated from human urine, reflecting the research hypothesis (later confirmed) that the kidney itself was locally producing a natriuretic peptide distinct from what circulated in blood, rather than simply filtering and concentrating blood-borne ANP. This urine-based discovery approach is part of why urodilatin's local, renal-specific role took longer to be appreciated than the more straightforward, blood-based discovery of ANP and BNP.

At Verified Peptides, we think ularitide's clinical development history is one of the most instructive, well-documented negative outcomes in this entire catalog, and we want to describe it with the same honesty we apply to compounds with more favorable results. Following encouraging Phase I/II data (including PMID 16338265), ularitide advanced to TRUE-AHF, a large randomized, double-blind, placebo-controlled Phase III trial (Packer et al., New England Journal of Medicine, 2017, PMID 28402745) that enrolled 2,157 patients with acute heart failure — a genuinely large, well-powered trial by the standards of heart failure drug development, and one of the largest trials behind any compound in this catalog.

The results were unambiguous: ularitide produced favorable acute physiological effects (without increasing cardiac troponin levels, addressing a specific safety concern that had been raised about aggressive vasodilator therapy in heart failure), but the 48-hour infusion did not improve the trial's clinical composite endpoint, and critically, did not reduce long-term cardiovascular mortality — 21.7% of ularitide-treated patients died from cardiovascular causes over follow-up compared to 21.0% of placebo patients (hazard ratio 1.03, 96% CI 0.85-1.25, p=0.75), a result indistinguishable from no effect at all on the outcome that mattered most.

We want to be direct about what this means: TRUE-AHF is a genuine, well-designed, adequately powered negative trial, not an ambiguous or underpowered one. It represents one of several prominent acute heart failure drug trials from this general era (alongside nesiritide's more complicated regulatory history, also built on this site) that found short-term hemodynamic improvement did not translate into the long-term mortality benefit researchers had hoped for — a broader, field-wide lesson about the gap between improving how a heart failure patient feels and functions acutely versus improving how long they live, which the natriuretic peptide field has had to reckon with across multiple compounds.

No ularitide/urodilatin formulation has received FDA approval, and clinical development for acute heart failure has not continued following the TRUE-AHF result. At Verified Peptides, we sell research-grade Urodilatin exclusively for laboratory research, and we think its combination of a well-characterized distinct physiological role (local renal natriuretic signaling) and a large, honestly negative Phase III trial makes it a valuable comparison point for researchers studying why acute hemodynamic improvement in heart failure has proven so difficult to translate into mortality benefit.

Urodilatin's local, paracrine renal production and action is a genuinely distinctive feature within the natriuretic peptide family: rather than being released into general circulation from cardiac tissue like ANP and BNP, it is synthesized within the kidney's distal tubule and is thought to act locally on adjacent tubular segments, meaning circulating blood levels of urodilatin do not necessarily reflect its actual local concentration or activity at its site of action — an important methodological consideration for any research attempting to measure or correlate urodilatin levels with its physiological effects.

Ularitide (synthetic urodilatin) reached a very substantial stage of clinical development — a completed, adequately powered Phase III trial with over 2,100 randomized patients — placing it among a small number of compounds in this entire catalog whose clinical failure is documented at this scale of evidence, rather than being an early-phase or small-trial result. This scale of negative data is, in its own way, more informative than a small or ambiguous trial would be, since it substantially rules out anything but a very small clinical benefit.

TRUE-AHF's finding that ularitide did not increase cardiac troponin levels addressed a specific mechanistic safety concern that had been raised about aggressive vasodilator therapy in acute heart failure — the hypothesis that excessive blood pressure reduction could reduce coronary perfusion and cause subclinical cardiac injury. Ruling this out, even in a trial that ultimately found no mortality benefit, is itself a meaningful piece of safety information for the broader field studying vasodilator strategies in acute heart failure.

The broader pattern across nesiritide, ularitide, and other acute heart failure vasodilator/natriuretic peptide candidates tested in large trials during the 2000s-2010s — favorable short-term hemodynamic and symptomatic effects that failed to translate into improved long-term survival — has become an important, field-shaping lesson in heart failure drug development, prompting researchers to reconsider what short-term physiological endpoints reliably predict genuine long-term clinical benefit.

At Verified Peptides, we require independent third-party HPLC purity testing and mass spectrometry identity confirmation for every batch of research-grade Urodilatin we offer, with a Certificate of Analysis (COA) available for each lot. As a 32-residue peptide with an internal disulfide-bonded ring structure shared with the broader natriuretic peptide family, correct folding and disulfide bond formation are essential to biological activity, making identity confirmation beyond simple amino acid composition analysis particularly important.

We source exclusively from manufacturers operating under Good Manufacturing Practice (GMP)-aligned quality systems, and every lot is independently verified rather than accepted solely on a supplier's internal documentation. Researchers should always request and review the specific COA for the lot they receive, confirming purity percentage, molecular identity, and correct disulfide bond formation where analytically verifiable.

Lyophilized Urodilatin is stable when stored at -20°C, protected from light and moisture, and researchers can generally expect the unreconstituted peptide to maintain integrity over an extended period under these conditions. At Verified Peptides, we ship lyophilized peptide with appropriate cold-chain packaging to preserve stability in transit.

Once reconstituted, Urodilatin solution should be stored refrigerated at 2–8°C and used within the timeframe indicated on the product's documentation. Because urodilatin's biological activity depends on maintaining its internal disulfide-bonded ring structure, researchers should avoid conditions such as reducing agents or repeated freeze-thaw cycling that could disrupt this structure and compromise activity.

Researchers should follow the specific storage guidance provided with each lot's documentation to preserve sample validity, and avoid repeated freeze-thaw cycles of reconstituted material.