PL-3994
Also known as: Cys(Et)-c[Lys-Asp-Arg-Ile-c(Cys-Phe-Gly)], PL-3994, PL3994
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Summary
PL-3994 is an investigational cyclic peptide that acts as a selective agonist of the natriuretic peptide receptor‑A (NPR‑A). Pre‑clinical work shows it relaxes airway smooth muscle and reduces bronchoconstriction in animal models, suggesting possible use as a bronchodilator for asthma or other obstructive lung diseases. The compound is not yet approved for any therapeutic indication.
Mechanism of Action
PL‑3994 binds with high affinity to NPR‑A on airway smooth‑muscle cells, stimulating the receptor’s intrinsic guanylyl‑cyclase activity. This raises intracellular cyclic GMP, which activates protein kinase G and leads to relaxation of smooth‑muscle fibers. The peptide is resistant to degradation by neutral endopeptidase, prolonging its activity compared with endogenous natriuretic peptides. It shows negligible activity at NPR‑B and low affinity for NPR‑C, and no measurable off‑target effects in broad screening assays.
What the Research Shows
In vitro, PL‑3994 displayed nanomolar affinity for human, dog, and rat NPR‑A and generated cGMP at low nanomolar concentrations. It relaxed pre‑contracted guinea‑pig trachea (IC50 ≈ 43 nM) and produced modest relaxation of human precision‑cut lung slices. In vivo, intratracheal administration to guinea‑pig models produced dose‑dependent inhibition of methacholine‑induced bronchoconstriction without measurable changes in heart rate or blood pressure. The peptide remained >90 % intact after two hours in the presence of human neutral endopeptidase, indicating metabolic stability. No human clinical data have been published.
Reported Benefits
Pre‑clinical evidence suggests PL‑3994 could provide a longer‑acting bronchodilator effect than native natriuretic peptides, owing to its resistance to neutral endopeptidase. Its selective NPR‑A activation and lack of cardiovascular impact in animal studies point to a favorable therapeutic profile for asthma or related airway disorders, pending human testing.
Limitations of the Evidence
All data are limited to in vitro assays, ex vivo human lung tissue, and animal models; no human pharmacokinetic, efficacy, or safety studies have been reported. The magnitude of airway relaxation in human tissue was modest, and the optimal dosing route and schedule remain undefined. Potential long‑term effects and immunogenicity of the cyclic peptide are unknown.
Safety Considerations
Animal investigations reported no significant alterations in cardiovascular parameters and no activity against a panel of 75 diverse molecular targets, suggesting a low off‑target risk. However, comprehensive safety evaluation in humans has not been performed, so adverse‑event profiles, tolerability, and immunogenic potential remain uncharacterized.
How It Is Administered
Pre‑clinical work has employed intratracheal delivery in guinea‑pig models to assess bronchodilatory activity. The compound is also listed for potential intravenous, subcutaneous, and topical ophthalmic administration, but formulation and dosing details for these routes have not been disclosed in the literature.
Routes of Administration
Goals & Uses
- Dry eye diseaseOphthalmologyModerate
- Bronchodilation / asthmaPulmonaryLow
- Dry mouth (xerostomia)Salivary Gland DisorderLow
- Acute decompensated heart failure treatmentCardiovascularModerate
- Blood pressure reduction / hypertensionCardiovascularModerate
- Diuresis / natriuresisRenalModerate
Contraindications
- Severe renal impairmentOrganModerateKidney function concerns
- Known hypersensitivity to PL-3994 or componentsImmunologicHigh
- Hypotension or cardiogenic shockCardiovascularHigh
- HyponatremiaElectrolyte/MetabolicModerate
Adverse Effects
- Injection site reactionsLocalUncommon
- HeadacheNeurologicUncommonPain in the head or upper neck
- Ocular irritationLocalCommon
- HypotensionCardiovascularCommonLow blood pressure
- FlushingVascularUncommonWarmth and redness of the skin
- Blurred visionVisualUncommon
Drug Interactions
- Antihypertensive agentsModerate
- DiureticsModerateMay worsen dehydration or electrolyte imbalance
- Phosphodiesterase-5 inhibitors (e.g., sildenafil)High
- DesmopressinModerate
Population Constraints
- PregnancyReproductive SafetyRelative
- Pediatric patientsAgeRelative
- Elderly patientsAgeRelative
- Pregnant womenReproductiveRelative
- Children <12 yearsAgeRelative
Regulatory Status
- European UnionInvestigationalNo EMA marketing authorization.
- United StatesInvestigationalPhase II clinical trials ongoing; not FDA‑approved.
- United KingdomInvestigationalUnder clinical investigation; not licensed.
No approved indication in any major jurisdiction. Investigated in Phase I/II clinical trials. Developed by Palatin Technologies.
Evidence & Sources
- Journal ArticleLowEdelson JD, et al.2013-01-01T00:00:00.000000Z
- Journal ArticleLowTomillero A, Moral MA2009-01-01T00:00:00.000000Z
Frequently Asked Questions
What type of drug is PL‑3994?
PL‑3994 is a synthetic cyclic peptide that selectively activates the natriuretic peptide receptor‑A, a receptor involved in smooth‑muscle relaxation.
Has PL‑3994 been tested in humans?
No. Published data are limited to laboratory experiments, human lung‑slice assays, and animal studies; no clinical trials in people have been reported.
Could PL‑3994 replace current asthma inhalers?
It is too early to say. While animal studies show bronchodilation without cardiovascular effects, human efficacy, safety, and optimal delivery method must still be demonstrated.
Why is resistance to neutral endopeptidase important?
Neutral endopeptidase rapidly degrades natural natriuretic peptides. PL‑3994’s resistance to this enzyme means it remains active longer, potentially providing a more sustained therapeutic effect.
What are the known side effects of PL‑3994?
In the animal studies reported, no significant side effects, especially cardiovascular changes, were observed. However, side‑effect information in humans is not yet available.
What is PL-3994?
PL-3994 is an investigational cyclic peptide that acts as a selective agonist of the natriuretic peptide receptor‑A (NPR‑A). Pre‑clinical work shows it relaxes airway smooth muscle and reduces bronchoconstriction in animal models, suggesting possible use as a bronchodilator for asthma or other obstructive lung diseases. The compound is not yet approved for any therapeutic indication.
What is PL-3994 used for?
PL-3994 is educationally associated with: Dry eye disease, Bronchodilation / asthma, Dry mouth (xerostomia), Acute decompensated heart failure treatment, Blood pressure reduction / hypertension, Diuresis / natriuresis. Educational only — not medical advice.
How is PL-3994 administered?
Recorded routes of administration: Intravenous, Subcutaneous, Topical Ophthalmic.
What are the potential side effects of PL-3994?
Reported adverse effects include: Injection site reactions, Headache, Ocular irritation, Hypotension, Flushing, Blurred vision. This list is not exhaustive — consult a qualified clinician.
Who should avoid PL-3994?
Recorded contraindications: Severe renal impairment, Known hypersensitivity to PL-3994 or components, Hypotension or cardiogenic shock, Hyponatremia. Consult a qualified clinician before use.