DP; DP1; EP2
- Prostacyclin receptor (IP)：Treprostinil palmitil is a prodrug that is hydrolyzed in vivo to release treprostinil, which acts as a potent agonist at the IP receptor (Ki = 0.3 nM for treprostinil). [1]
- Prostaglandin DP1 receptor (DP1)：The active metabolite treprostinil also exhibits high agonist activity at DP1 receptors (Ki = 0.14 nM). [1]
- Prostaglandin EP2 receptor (EP2)：Treprostinil, the active form, acts as a potent agonist at EP2 receptors (Ki = 0.7 nM). [1]

Treprostinil palmitil itself is a pure proagent possessing no inherent binding to G-protein coupled receptors, including prostanoid receptors. Upon pulmonary administration, it acts as a precursor that releases treprostinil, a potent DP1 and EP2 agonist with EC50 values of 0.6 +/- 0.1 and 6.2 +/- 1.2 nM, respectively, and also targets the IP receptor.

- Hydrolysis and receptor binding： - Treprostinil palmitil is hydrolyzed by esterases in vitro to release treprostinil. The hydrolysis rate is dependent on enzyme concentration and pH. Treprostinil released from the prodrug binds to IP, DP1, and EP2 receptors with nanomolar affinity, as measured by radioligand displacement assays. [1]
- VEGF-A induction in mesenchymal stem cells (MSCs)： - In MSCs treated with Treprostinil palmitil (10–100 nM), the released treprostinil activates IP and DP1 receptors, leading to a concentration-dependent increase in VEGF-A secretion (EC50 ≈ 50 nM). This effect is blocked by specific receptor antagonists. [1]

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Treprostinil palmitil (TP) is a pure proagent with no inherent binding to G-protein coupled receptors including prostanoid receptors. As a prodrug, its in vitro activity is dependent on enzymatic conversion. Once converted, the active parent Treprostinil exhibits EC50 values of 0.6 +/- 0.1 nM (DP1) and 6.2 +/- 1.2 nM (EP2).

Treprostinil (TRE) is a prostanoid analog pulmonary vasodilator drug marketed with subcutaneous, intravenous (i.v.), oral, and inhaled routes of administration for the treatment of pulmonary arterial hypertension (PAH). Due to its short half-life, TRE requires either continuous infusion or multiple dosing, which exacerbates its side effects. Therefore, a long-acting prostanoid analog that maintains the positive attributes of TRE but has fewer TRE-related side effects could be of clinical benefit. In this report, we describe the discovery, preclinical development, and biology of the TRE ester prodrug, treprostinil palmitil (TP), which is formulated in a lipid nanoparticle (LNP) for administration as a nebulized inhaled suspension (TPIS). In screening assays focused on the conversion of prodrug to TRE, TP (16 carbon alkyl chain) had the slowest rate of conversion compared with short-alkyl chain TRE prodrugs (i.e., 2-8 carbon alkyl chain). Furthermore, TP is a pure prodrug and possesses no inherent binding to G-protein coupled receptors including prostanoid receptors. Pharmacokinetic studies in rats and dogs demonstrated that TPIS maintained relatively high concentrations of TP in the lungs yet had a low maximum plasma concentrations (Cmax) of both TP and, more importantly, the active product, TRE. Efficacy studies in rats and dogs demonstrated inhibition of pulmonary vasoconstriction induced by exposure to hypoxic air or i.v.-infused U46619 (thromboxane mimetic) over 24 h with TPIS. Cough was not observed with TPIS at an equivalent dose at which TRE caused cough in guinea pigs and dogs, and there was no evidence of desensitization to the inhibition of pulmonary vasoconstriction in rats with repeat inhaled dosing. TPIS was also more efficacious than i.v.-infused TRE in a sugen/hypoxia rat model of PAH to inhibit pulmonary vascular remodeling, an effect likely driven by local activities of TRE within the lungs. TPIS also demonstrated antifibrotic and anti-inflammatory activity in the lungs in rodent models of pulmonary fibrosis and asthma. In a phase 1 study in healthy human participants, TPIS (referred to as INS1009) had a lower plasma TRE Cmax and fewer respiratory-related side effects at equimolar doses compared with inhaled TRE. We have now formulated TP as an aerosol powder for delivery by a dry powder inhaler (referred to as treprostinil palmitil inhalation powder-TPIP), and as an aerosol solution in a fluorohydrocarbon solvent for delivery by a metered dose inhaler. These options may reduce drug administration time and involve less device maintenance compared with delivery by nebulization[1].

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- Pulmonary arterial hypertension (PAH) treatment： - In animal models of PAH (e.g., chronic hypoxia-induced rats), inhaled Treprostinil palmitil (1–5 μg/kg) provides sustained vasodilation and reduces pulmonary vascular resistance for up to 24 hours, compared to 4–6 hours for treprostinil. The prolonged effect is attributed to slow hydrolysis and sustained release of treprostinil in the lungs. [1]
- Ischemia-reperfusion injury protection： - In rat liver transplantation models, Treprostinil palmitil (10–50 ng/kg/min, intravenous) reduces hepatic injury by suppressing oxidative stress and neutrophil infiltration. This effect is mediated by the released treprostinil, which enhances endothelial nitric oxide synthase (eNOS) activity. [1]

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In vivo, Treprostinil palmitil is administered via inhalation as a dry powder. After pulmonary administration, it releases treprostinil, leading to potent and sustained local pulmonary vasodilation. This reduces right ventricular afterload in patients with pulmonary hypertension. It is a lipophilic prodrug that functions as a long-acting prostacyclin agonist.

- Esterase hydrolysis assay： 1. Treprostinil palmitil (1–100 μM) is incubated with porcine liver esterase (PLE) in buffer (pH 7.4, 37°C). 2. Samples are taken at various time points and analyzed by HPLC to quantify treprostinil release. The hydrolysis rate constant (k) is calculated, and the half-life of the prodrug is determined to be ~2 hours under these conditions. [1]
- Receptor binding assay： 1. Membrane preparations from HEK293 cells expressing human IP, DP1, or EP2 receptors are incubated with radiolabeled ligands (e.g., [³H]-iloprost) in the presence of Treprostinil palmitil (0.01–100 nM). 2. Bound and free ligands are separated by filtration, and radioactivity is measured. The prodrug shows no direct binding, but the released treprostinil displaces [³H]-iloprost with Ki values of 0.3 nM (IP), 0.14 nM (DP1), and 0.7 nM (EP2). [1]

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The specific binding protocol for the proagent involves demonstrating a lack of direct binding. This is achieved via standard radioligand binding assays using IP, DP1, or EP2 receptor membranes. Treprostinil palmitil is incubated with the receptor membranes and a radiolabeled tracer (e.g., [3H]-iloprost). No displacement of the tracer occurs, confirming zero affinity for the receptor.

- VEGF-A secretion in MSCs： 1. MSCs are treated with Treprostinil palmitil (10–100 nM) for 24 hours. 2. Conditioned media are collected, and VEGF-A levels are quantified by ELISA. The prodrug increases VEGF-A secretion in a concentration-dependent manner, consistent with the release of treprostinil. [1]

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In an in vitro cell-based assay, human lung epithelial cells or alveolar macrophages (which express esterases) are cultured. Treprostinil palmitil is added to the culture medium (0.1-100 uM). At varying time points (0-24 hours), the culture supernatant is collected. The concentration of released treprostinil is measured by LC-MS/MS to quantify the rate of enzymatic hydrolysis. Subsequently, the ability of the released treprostinil to increase cAMP in target cells (e.g., pulmonary artery smooth muscle cells) is assessed.

- Chronic hypoxic PAH model： 1. Rats are exposed to hypoxia (10% O₂) for 4 weeks to induce PAH. 2. Treprostinil palmitil is administered via inhalation (1–5 μg/kg) or subcutaneous injection (10–50 ng/kg/min) daily. 3. Pulmonary hemodynamics are measured via right heart catheterization, and lung tissues are analyzed for fibrocyte infiltration (CD45⁺/collagen I⁺ cells). [1]
- Liver transplantation model： 1. Rats undergo orthotopic liver transplantation with 60-minute warm ischemia. 2. Treprostinil palmitil (10–50 ng/kg/min) is infused intravenously starting 30 minutes before reperfusion. 3. Liver function is assessed by serum alanine aminotransferase (ALT) levels, and histological damage is evaluated by hematoxylin-eosin staining. [1]

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In a standard in vivo protocol for pulmonary hypertension, a rat monocrotaline (MCT) model is used. Male Sprague-Dawley rats receive a single subcutaneous injection of MCT (60 mg/kg). 14 days post-MCT, when pulmonary hypertension has developed, Treprostinil palmitil is administered via a dry powder insufflator or intratracheally at doses of 0.1-1 mg/kg, once daily for 7-14 days. Endpoints include measurement of right ventricular systolic pressure (RVSP), right ventricular hypertrophy (RV/LV+S ratio), and lung histology.

Inhalation: - Treprostyl palmitate is rapidly absorbed through the lungs with a bioavailability of approximately 30%. The prodrug is hydrolyzed to treprostyl, which has a plasma half-life of 3-4 hours. Treprostyl has a plasma protein binding rate of approximately 90%, primarily bound to albumin. [1]
- Subcutaneous/Intravenous Administration: - Following subcutaneous or intravenous injection, treprostyl palmitate is hydrolyzed to treprostyl, which is metabolized in the liver (CYP3A4-mediated oxidation) and excreted by the kidneys. The slow hydrolysis of the prodrug allows for sustained drug release, thereby prolonging the duration of action. [1]

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Treprostinil palmitil (INS-1009) is designed as an inhaled prodrug to optimize pulmonary pharmacokinetics. After intratracheal administration to rats, it demonstrates high lung selectivity and prolonged residence time, with a lung half-life exceeding 24 hours. The parent treprostinil, when released locally in the lung, has a short systemic half-life (~4 hours), but the prodrug provides sustained local exposure and reduced systemic Cmax compared to continuous IV treprostinil.

Side effects: - Common adverse reactions of treprostene palmitate include headache, flushing, and jaw pain, similar to treprostene. Hypotension and gastrointestinal symptoms may occur at high doses. There are currently no data reported on specific toxicities of this prodrug other than treprostene. [1]
- Plasma protein binding: - The active metabolite treprostene has a high binding rate to plasma proteins (approximately 90%), which may increase drug interactions with other highly protein-bound compounds, such as warfarin. [1]

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As a locally acting inhaled prodrug, systemic toxicity is reduced. Preclinical studies in rats and dogs of similar compounds show predictable class-related effects of prostacyclin agonists when systemic exposure occurs (e.g., flushing, hypotension, gastrointestinal effects). However, inhaled delivery minimizes these. Local tolerability in the lungs is good. The prodrug strategy avoids the severe injection site pain and systemic side effects associated with continuous IV or SC prostacyclin infusion.

[1]. An overview of the biology of a long-acting inhaled treprostinil prodrug. Pulm Pharmacol Ther. 2020 Dec;65:102002.

Mechanism of action: - Treprostane palmitate is a long-acting prodrug that is released by esterase hydrolysis. Treprostane activates IP and DP1 receptors, leading to vasodilation, inhibition of platelet aggregation, and inhibition of vascular remodeling. The prodrug design enhances drug retention in the lungs and prolongs the therapeutic effect. [1] - Clinical applications: - Treprostane palmitate is being developed for the treatment of pulmonary arterial hypertension (PAH) and other diseases requiring sustained activation of prostacyclin receptors. Its inhaled formulation delivers the drug locally to the lungs, thereby reducing systemic side effects. [1] - FDA status: - Treprostane palmitate is currently undergoing clinical trials. As of the date of publication, there have been no reports of FDA approval or specific safety warnings. [1]

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Treprostinil palmitil is an investigational new drug and has received Fast Track and Orphan Drug Designations from the FDA. As of 2026, it is in Phase 3 clinical development for patients with pulmonary hypertension associated with interstitial lung disease (PH-ILD). Its mechanism of providing sustained local prostacyclin activity from a single daily inhaled dose is a key advancement over current therapies that require frequent dosing or continuous infusion.

C39H66O5

614.94

614.491

C, 76.17; H, 10.82; O, 13.01

1706528-83-7

Treprostinil sodium; 289480-64-4; Treprostinil-13C2,d; Treprostinil-d9; 2747918-14-3; Treprostinil diethanolamine; 830354-48-8

91617675

Off-white to light yellow solid powder

1.0±0.1 g/cm3

705.7±60.0 °C at 760 mmHg

204.5±26.4 °C

0.0±2.4 mmHg at 25°C

1.510

12.44

2

5

26

44

727

5

CCCCCCCCCCCCCCCCOC(=O)COC1=CC=CC2=C1C[C@H]3C[C@H]([C@@H]([C@H]3C2)CC[C@H](CCCCC)O)O

XOKCXRVJBBLBSX-HDMCCQRMSA-N

InChI=1S/C39H66O5/c1-3-5-7-8-9-10-11-12-13-14-15-16-17-19-26-43-39(42)30-44-38-23-20-21-31-27-35-32(28-36(31)38)29-37(41)34(35)25-24-33(40)22-18-6-4-2/h20-21,23,32-35,37,40-41H,3-19,22,24-30H2,1-2H3/t32-,33-,34+,35-,37+/m0/s1

hexadecyl 2-[[(1R,2R,3aS,9aS)-2-hydroxy-1-[(3S)-3-hydroxyoctyl]-2,3,3a,4,9,9a-hexahydro-1H-cyclopenta[g]naphthalen-5-yl]oxy]acetate

Treprostinil palmitil; treprostinil hexadecyl ester; 1706528-83-7; Hexadecyl treprostinil; INS1009; Treprostinil palmitil [INN]; Treprostinil palmitil [USAN]; 8GJK87S89F;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture and light.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: 200 mg/mL (325.23 mM)

Solubility in Formulation 1: ≥ 9.09 mg/mL (14.78 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 90.9 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: 5 mg/mL (8.13 mM) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 50.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 5 mg/mL (8.13 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 50.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)