The effect of the vasoactive intestinal polypeptide agonist Ro 25-1553 on induced tone in isolated human airways and pulmonary artery

The role of vasoactive intestinal peptide in pulmonary diseases

Vasoactive intestinal peptide (VIP) is an abundant neurotransmitter in the lungs and other organs. Its discovery dates back to 1970. And VIP gains attention again due to the potential application in COVID-19 after a research wave in the 1980s and 1990s. The diverse biological impacts of VIP extend beyond its usage in COVID-19 treatment, encompassing its involvement in various pulmonary and systemic disorders. This review centers on the function of VIP in various lung diseases, such as pulmonary arterial hypertension, chronic obstructive pulmonary disease, asthma, cystic fibrosis, acute lung injury/acute respiratory distress syndrome, pulmonary fibrosis, and lung tumors. This review also outlines two main limitations of VIP as a potential medication and gathers information on extended-release formulations and VIP analogues.

Neural control of the lower airways: Role in cough and airway inflammatory disease

Airway function is under constant neurophysiological control, in order to maximize airflow and gas exchange and to protect the airways from aspiration, damage, and infection. There are multiple sensory nerve subtypes, whose disparate functions provide a wide array of sensory information into the CNS. Activation of these subtypes triggers specific reflexes, including cough and alterations in autonomic efferent control of airway smooth muscle, secretory cells, and vasculature. Importantly, every aspect of these reflex arcs can be impacted and altered by local inflammation caused by chronic lung disease such as asthma, bronchitis, and infections. Excessive and inappropriate activity in sensory and autonomic nerves within the airways is thought to contribute to the morbidity and symptoms associated with lung disease.

Neuroimmune Pathophysiology in Asthma

Asthma is a chronic inflammation of lower airway disease, characterized by bronchial hyperresponsiveness. Type I hypersensitivity underlies all atopic diseases including allergic asthma. However, the role of neurotransmitters (NT) and neuropeptides (NP) in this disease has been less explored in comparison with inflammatory mechanisms. Indeed, the airway epithelium contains pulmonary neuroendocrine cells filled with neurotransmitters (serotonin and GABA) and neuropeptides (substance P[SP], neurokinin A [NKA], vasoactive intestinal peptide [VIP], Calcitonin-gene related peptide [CGRP], and orphanins-[N/OFQ]), which are released after allergen exposure. Likewise, the autonomic airway fibers produce acetylcholine (ACh) and the neuropeptide Y(NPY). These NT/NP differ in their effects; SP, NKA, and serotonin exert pro-inflammatory effects, whereas VIP, N/OFQ, and GABA show anti-inflammatory activity. However, CGPR and ACh have dual effects. For example, the ACh-M3 axis induces goblet cell metaplasia, extracellular matrix deposition, and bronchoconstriction; the CGRP-RAMP1 axis enhances Th2 and Th9 responses; and the SP-NK1R axis promotes the synthesis of chemokines in eosinophils, mast cells, and neutrophils. In contrast, the ACh-α7nAChR axis in ILC2 diminishes the synthesis of TNF-α, IL-1, and IL-6, attenuating lung inflammation whereas, VIP-VPAC1, N/OFQ-NOP axes cause bronchodilation and anti-inflammatory effects. Some NT/NP as 5-HT and NKA could be used as biomarkers to monitor asthma patients. In fact, the asthma treatment based on inhaled corticosteroids and anticholinergics blocks M3 and TRPV1 receptors. Moreover, the administration of experimental agents such as NK1R/NK2R antagonists and exogenous VIP decrease inflammatory mediators, suggesting that regulating the effects of NT/NP represents a potential novel approach for the treatment of asthma.

Systemic vasoconstriction modulates the responses of pulmonary vasculature and airway to vasoconstrictors in anesthetized rats

PURPOSE

The physiological responses of the pulmonary vasculature and airway to various vasoconstrictors were studied using isolated perfused lungs and pulmonary arteries, but these responses were not systematically studied in in vivo rats. We determined these responses and modulating effects of systemic circulation in anesthetized rats.

METHODS

We measured directly pulmonary arterial pressure (PAP), left atrial pressure (LAP), aortic blood flow, and airway pressure (AWP) to determine pulmonary vascular resistance (PVR), following injections of angiotensin II (ANG II), endothelin-1 (ET-1), vasopressin, phenylephrine and thromboxane A2 mimetic U46619 in anesthetized SD rats.

RESULTS

ANG II, phenylephrine and vasopressin at high doses caused strong systemic vasoconstriction and left heart overload, resulting in a transient increase in LAP and pulmonary congestion, which consequently decreased PVR. Nonetheless, prior to LAP elevation, PVR was slightly but significantly increased by ANG II and phenylephrine. In contrast, ET-1 and U46619 substantially increased PVR in the absence of LAP elevation, while vasopressin did not increase PVR. In separate experiments, PAP and AWP increased when LAP was forcedly elevated. AWP was increased by U46619 through bronchoconstriction and by the other agents through increased LAP-induced pulmonary congestion.

CONCLUSION

Airway constriction is induced by U46619, and pulmonary vasoconstriction is induced strongly by U46619 and ET-1, and weakly by ANG II and phenylephrine, but not by vasopressin in anesthetized rats. ANG II, vasopressin and phenylephrine exert indirectly a transient pulmonary vasodilatory action due to pulmonary congestion evoked by strong systemic vasoconstriction, which may account for weak pulmonary pressor responses to these agents.

Homology modeling and molecular docking of human pituitary adenylate cyclase‑activating polypeptide I receptor

Pituitary adenylate cyclase-activating peptide I receptor (PAC1R) is member of the B class of G protein-coupled seven-transmembrane receptors, with molecular functions associated with neural cell differentiation, regeneration and the inhibition of apoptosis. However, the integrity of the protein structure is difficult to be determined in vitro. In the present study, the physicochemical properties of PAC1R were analyzed, the extracellular, transmembrane and intracellular regions were constructed and a three-dimensional structure model of PAC1R was produced using extracellular loop region optimization and the energy minimization homology modeling method. Preliminary studies on the PAC1R protein and ligand interactions used a molecular docking method. The results indicated that the interaction sites of PAC1R were at Ile63, Ser100 and Gln105. These were the sites where the PAC1R combined with a hydrazide small molecule inhibitor. This study provides a theoretical basis for further studies on the model for the development of PAC1R target drugs.

Role of VPAC2 receptor in monocrotaline-induced pulmonary hypertension in rats

Pulmonary hypertension (PH) is associated with significant morbidity and mortality. Vasoactive intestinal peptide (VIP) and pituitary adenylyl cyclase activating peptide (PACAP) have pulmonary vasodilatory and positive inotropic effects via receptors VPAC1 and VPAC2, which possess a similar affinity for both peptides, and PAC1, a PACAP-preferring receptor. VIP is a promising option for PH treatment; however, various physiological effects of VIP have limited its clinical use. We investigated the effects of VPAC1 and VPAC2 selective agonists VIP and PACAP to explore more appropriate means of treatment for PH. We examined hemodynamic changes in right ventricular systolic pressure (RVSP), systemic blood pressure (SBP), total pulmonary resistance index (TPRI), total systemic resistance index, and cardiac index (CI) in response to their agonists with monocrotaline (MCT)-induced PH and explored involvement of VIP/PACAP expression and receptors in PH. Sprague-Dawley rats were divided into the MCT group (administered MCT 60 mg/kg) and control group. In MCT-induced PH, decreased VIP and PACAP were associated with upregulation of VPAC1, VPAC2, and PAC1 in lung tissues. Intravenous injection of VPAC2-selective agonist BAY 55-9837 and VIP, but not [Ala(11,22,28)]VIP, improved the CI. The decrease in SBP with VPAC2 agonist was significantly less than that in the control. Although they decreased SBP, these agonists hardly affected RVSP in the control. Activation of VPAC2 receptor with BAY 55-9837 effectively improved RVSP, TPRI, and CI in MCT-induced PH, suggesting a VPAC2 agonist as a possible promising treatment for PH.

Vasodilatory effect of the stable vasoactive intestinal peptide analog RO 25-1553 in murine and rat lungs

Rationale

Stable analogs of vasoactive intestinal peptide (VIP) have been proposed as novel line of therapy in chronic obstructive pulmonary disease (COPD) based on their bronchodilatory and anti-inflammatory effects. We speculated that VIP analogs may provide additional benefits in that they exert vasodilatory properties in the lung, and tested this hypothesis in both ex vivo and in vivo models.

Methods

In isolated perfused mouse lungs and in an in vivo rat model, pulmonary blood vessels were preconstricted by hypoxia and hemodynamic changes in response to systemic (ex vivo) or inhaled (in vivo) administration of the cyclic VIP analog RO 25-1553 were determined.

Results

In mouse lungs, RO 25-1553 reduced intrinsic vascular resistance at normoxia, and attenuated the increase in pulmonary artery pressure in response to acute hypoxia. Consistently, inhalation of RO 25-1553 (1 mg·mL⁻¹ for 3 min) caused an extensive and sustained (> 60 min) inhibition of the pulmonary arterial pressure increase in response to hypoxia in vivo that was comparable to the effects of inhaled sildenafil. This effect was not attributable to systemic cardiovascular effects of RO 25-1553, but to a lung specific reduction in pulmonary vascular resistance, while cardiac output and systemic arterial hemodynamics remained unaffected. No adverse effects of RO 25-1553 inhalation on pulmonary gas exchange, ventilation-perfusion matching, or lung fluid content were detected.

Conclusion

Our findings demonstrate that inhaled delivery of the stable VIP analog RO 25-1553 induces a potent and sustained vasodilatory effect in the pulmonary circulation with no detectable adverse effects. Therapeutic inhalation of RO 25-1553 may provide vascular benefits in addition to its reported anti-inflammatory and bronchodilatory effects in COPD, yet caution is warranted given the overall poor results of vasodilator therapies for pulmonary hypertension secondary to COPD in a series of recent clinical trials.

Pituitary adenylate cyclase-activating polypeptide plays an anti-inflammatory role in endotoxin-induced airway inflammation: in vivo study with gene-deleted mice

The presence of pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptors in capsaicin-sensitive peptidergic sensory nerves, inflammatory and immune cells suggest its involvement in inflammation. However, data on its role in different inflammatory processes are contradictory and there is little known about its functions in the airways. Therefore, our aim was to examine intranasal endotoxin-induced subacute airway inflammation in PACAP gene-deficient (PACAP⁻/⁻) and wild-type (PACAP⁺/⁺) mice. Airway responsiveness to inhaled carbachol was determined in unrestrained mice with whole body plethysmography 6 h and 24 h after LPS. Myeloperoxidase (MPO) activity referring to the number of accumulated neutrophils and macrophages was measured with spectrophotometry and interleukin-1β (IL-1β) concentration with ELISA from the lung homogenates. Histological evaluation and semiquantitative scoring were also performed. Bronchial responsiveness, as well as IL-1β concentration and MPO activity markedly increased at both timepoints. Perivascular edema dominated the histological picture at 6 h, while remarkable peribronchial granulocyte accumulation, macrophage infiltration and goblet cell hyperplasia were seen at 24h. In PACAP⁻/⁻ mice, airway hyperreactivity was significantly higher 24 h after LPS and inflammatory histopathological changes were more severe at both timepoints. MPO increase was almost double in PACAP⁻/⁻ mice compared to the wild-types at 6 h. In contrast, there was no difference between the IL-1β concentrations of the PACAP⁺/⁺ and PACAP⁻/⁻ mice. These results provide evidence for a protective role for PACAP in endotoxin-induced airway inflammation and hyperreactivity.

Prospect of vasoactive intestinal peptide therapy for COPD/PAH and asthma: a review

There is mounting evidence that pulmonary arterial hypertension (PAH), asthma and chronic obstructive pulmonary disease (COPD) share important pathological features, including inflammation, smooth muscle contraction and remodeling. No existing drug provides the combined potential advantages of reducing vascular- and bronchial-constriction, and anti-inflammation. Vasoactive intestinal peptide (VIP) is widely expressed throughout the cardiopulmonary system and exerts a variety of biological actions, including potent vascular and airway dilatory actions, potent anti-inflammatory actions, improving blood circulation to the heart and lung, and modulation of airway secretions. VIP has emerged as a promising drug candidate for the treatment of cardiopulmonary disorders such as PAH, asthma, and COPD. Clinical application of VIP has been limited in the past for a number of reasons, including its short plasma half-life and difficulty in administration routes. The development of long-acting VIP analogues, in combination with appropriate drug delivery systems, may provide clinically useful agents for the treatment of PAH, asthma, and COPD. This article reviews the physiological significance of VIP in cardiopulmonary system and the therapeutic potential of VIP-based agents in the treatment of pulmonary diseases.

Characterization of agonist-induced vasoconstriction in mouse pulmonary artery

In recent years, transgenic mouse models have been developed to examine the underlying cellular and molecular mechanisms of lung disease and pulmonary vascular disease, such as asthma, pulmonary thromboembolic disease, and pulmonary hypertension. However, there has not been systematic characterization of the basic physiological pulmonary vascular reactivity in normal and transgenic mice. This represents an intellectual "gap", since it is important to characterize basic murine pulmonary vascular reactivity in response to various contractile and relaxant factors to which the pulmonary vasculature is exposed under physiological conditions. The present study evaluates excitation- and pharmacomechanical-contraction coupling in pulmonary arteries (PA) isolated from wild-type BALB/c mice. We demonstrate that both pharmaco- and electromechanical coupling mechanisms exist in mice PA. These arteries are also reactive to stimulation by alpha(1)-adrenergic agonists, serotonin, endothelin-1, vasopressin, and U-46619 (a thromboxane A(2) analog). We conclude that the basic vascular responsiveness of mouse PA is similar to those observed in PA of other species, including rat, pig, and human, albeit on a different scale and to varying amplitudes.

Pulmonary and systemic effects of inhaled PACAP38 in healthy male subjects

BACKGROUND

Pituitary adenylate cyclase activating polypeptide 1-38 (PACAP38) displays biological activities (e.g. bronchodilatory, pulmonary vasodilatory and anti-inflammatory properties) that are relevant in several pulmonary diseases. The aim of this study was to assess the safety and tolerability and the pulmonary and systemic effects of inhaled PACAP38 in humans.

MATERIALS AND METHODS

Twelve healthy male subjects (mean age 28) were studied in a randomized, double-blind, placebo-controlled dose escalation trial with inhalation of PACAP38 to a cumulative dose of 480 microg. Lung function was measured by body plethysmography. Systemic absorption was evaluated by plasma levels, skin blood flux (estimated by laser Doppler imager fluxmetry) and systemic haemodynamics.

RESULTS

Inhalation of PACAP38 did not cause relevant adverse reactions or an increase of PACAP38 plasma levels. No statistically significant changes in lung function tests and no systemic effects (blood pressure, pulse rate or skin blood flux) occurred.

CONCLUSION

Inhaled PACAP38 was well tolerated without systemic side-effects in healthy male subjects.

Combination therapy and new types of agents for pulmonary arterial hypertension

This review assesses the available evidence supporting the use of drug combinations for the management of the various forms of pulmonary arterial hypertension (PAH). Ongoing and forthcoming randomized trials evaluating this strategy are also highlighted. Furthermore, new types of agents to treat PAH in the future are explored.

Role of c-fos gene in vasoactive intestinal peptide promoted synthesis of pulmonary surfactant phospholipids

We previously reported that vasoactive intestinal peptide (VIP) promoted synthesis of phosphatidylcholine (PC) in alveolar type II (ATII) cells. But the intracellular mechanism for this effect was unknown. In this work, we investigated the intracellular signal transduction pathway for VIP promoted synthesis of PC, the major lipid component of pulmonary surfactant (PS), by using an antagonist of VIP receptors, inhibitor of protein kinase C (PKC) and antisense oligonucleotides (AS-ODN) for c-fos oncogene. Our results showed that: 1 in circle [D-P-Cl-Phe(6)-Leu(17)]-VIP (10(-6) mol/l), an antagonist of VIP receptors, could decrease the quantity of [(3)H] choline incorporation, microsomal choline-phosphate cytidylyltransferase (CCT) mRNA expression and CCT activity induced by VIP (10(-8) mol/l) in cultured lung explants to the control levels; 2 in circle VIP (10(-8) mol/l) upregulated c-Fos protein expression in ATII cells. AS-ODN for c-fos oncogene (9x10(-6) mol/l) could block the elevation of [(3)H] choline incorporation, microsomal CCT mRNA expression and CCT activity induced by VIP in cultured lung explants and in ATII cells; 3 in circle H7 (10(-5) mol/l), a PKC inhibitor could also reduce VIP induced [(3)H] choline incorporation, microsomal CCT mRNA expression and CCT activity in cultured lung explants and in ATII cells. These results demonstrated that VIP receptors, PKC and c-Fos protein played important roles in the signaling pathway through which VIP promoted the synthesis of PC.

Involvement of endothelial NO in the dilator effect of VIP on rat isolated pulmonary artery

The endothelium and its interaction with smooth muscle play a central role in the local control of the pulmonary vasculature, and endothelial dysfunction is thought to contribute to pulmonary hypertension and chronic obstructive pulmonary disease. Vasoactive intestinal peptide (VIP), a 28-amino acid neuropeptide, relaxes the rat pulmonary artery, but there is controversy as to whether or not this action of VIP depends on the endothelium. The aim of this study, therefore, was to investigate the role of the endothelium and nitric oxide (NO), the major endothelium-derived relaxing factor, in the dilator action of VIP on the rat isolated pulmonary artery. Pulmonary artery preparations pre-contracted by the alpha(1)-adrenoceptor agonist L-phenylephrine were relaxed by VIP (0.003-1 microM) and acetylcholine (0.003-10 microM) in a concentration-dependent manner. Mechanical removal of the endothelium reduced the maximal response to VIP by about 50% and practically abolished the response to acetylcholine. Inhibition of NO synthesis by N(omega)-nitro-L-arginine methyl ester (0.5 mM) had a similar effect, abolishing the vasorelaxation caused by acetylcholine and attenuating the vasorelaxation caused by VIP by about 50%. From these data it is concluded that the relaxant action of VIP on the rat isolated pulmonary artery depends in part on the presence of the endothelium and that this part is mediated by endothelial NO.

Human VIP-alpha: an emerging biologic response modifier to treat primary pulmonary hypertension

Primary pulmonary hypertension (PPH) is a rare life-threatening disorder of unknown etiology manifested by chronic elevation of pulmonary arterial pressure. Given that pulmonary vasoconstriction, endothelial and vascular smooth muscle cell proliferation and in situ thrombosis contribute appreciably to the evolution of PPH, treatment with vasodilators, antiproliferative drugs and anticoagulants, alone or in combination, constitute the pharmacologic standard of care. To this end, long-term administration of oral calcium channel blockers, prostacyclin analogs by various routes and oral endothelin-1 receptor antagonists, alone or in combination, is efficacious in treating patients with PPH. Unfortunately, efficacy is hampered by poor stability, delivery and bioavailability, and by systemic toxicity. Hence, there is an ongoing need to develop and test new drugs to treat patients with PPH. To address this issue, a novel, targeted, long-acting, biocompatible and safe sterically stabilized liposomal and micellar formulation of human vasoactive intestinal peptide (VIP) was developed and tested for human use: the 28-amino acid pleiotropic biologic response modifier, human VIP-alpha. The long-lasting salutary effects of phospholipid-associated VIP on vasomotor tone and arterial pressure were expressed at low concentrations solely in diseased animals and were independent of its route of administration. Thus, the author proposes that human VIP-alpha could be developed as a safe long-acting drug to treat patients with PPH.

Novel concepts of neuropeptide-based drug therapy: vasoactive intestinal polypeptide and its receptors

Chronic inflammatory airway diseases such as bronchial asthma or chronic obstructive pulmonary disease (COPD) are major contributors to the global burden of disease. Although inflammatory cells play the central role in the pathogenesis of the diseases, recent observations indicate that also resident respiratory cells represent important targets for pulmonary drug development. Especially targeting airway neuromediators offers a possible mechanism by which respiratory diseases may be treated in the future. Among numerous peptide mediators such as tachykinins, calcitonin gene-related peptide, neurotrophins or opioids, vasoactive intestinal polypeptide (VIP) is one of the most abundant molecules found in the respiratory tract. In human airways, it influences many respiratory functions via the receptors VPAC1, VPAC2 and PAC1. VIP-expressing nerve fibers are present in the tracheobronchial smooth muscle layer, submucosal glands and in the walls of pulmonary and bronchial arteries and veins. Next to its strong bronchodilator effects, VIP potently relaxes pulmonary vessels, and plays a pivotal role in the mediation of immune mechanisms. A therapy utilizing the respiratory effects of VIP would offer potential benefits in the treatment of obstructive and inflammatory diseases and long acting VIP-based synthetic non-peptide compounds may represent a novel target for drug development.

Heterogeneity of neuronal and smooth muscle receptors involved in the VIP- and PACAP-induced relaxations of the pig intravesical ureter

1. The mechanisms and receptors involved in the vasoactive intestinal peptide (VIP)- and pituitary adenylate cyclase-activating polypeptide (PACAP)-induced relaxations of the pig intravesical ureter were investigated. 2. VIP, PACAP 38 and PACAP 27 concentration-dependently relaxed U46619-contracted ureteral strips with a similar potency. [Ala(11,22,28)]-VIP, a VPAC(1) agonist, showed inconsistent relaxations. 3. The neuronal voltage-gated Ca(2+) channel inhibitor, omega-conotoxin GVIA (omega-CgTX, 1 microm), reduced the VIP relaxations. Urothelium removal or blockade of capsaicin-sensitive primary afferents, nitric oxide (NO) synthase and guanylate cyclase with capsaicin (10 microm), N(G)-nitro-l-arginine (l-NOARG, 100 microm) and 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 5 microm), respectively, did not change the VIP relaxations. However, the PACAP 38 relaxations were reduced by omega-CgTX, capsaicin, l-NOARG and ODQ. 4. The VIP and VIP/PACAP receptor antagonists, [Lys(1), Pro(2,5), Arg(3,4), Tyr(6)]-VIP (1 microm) and PACAP (6-38) (0.4 microm), inhibited VIP and VIP and PACAP 38, respectively, relaxations. 5. The nonselective and large-conductance Ca(2)-activated K(+) channel blockers, tetraethylammonium (3 mm) and charybdotoxin (0.1 microm), respectively, and neuropeptide Y (0.1 microm) did not modify the VIP relaxations. The small-conductance Ca(2)-activated K(+) channel blocker apamin (1 microm) did not change the PACAP 27 relaxations. 6. The cAMP-dependent protein kinase A (PKA) blocker, 8-(4-chlorophenylthio)adenosine-3',5'-cyclic monophosphorothioate (Rp-8-CPT-cAMPS, 100 microm), reduced VIP relaxations. The phosphodiesterase 4 inhibitor rolipram and the adenylate cyclase activator forskolin relaxed ureteral preparations. The rolipram relaxations were reduced by Rp-8-CPT-cAMPS. Forskolin (30 nm) evoked a potentiation of VIP relaxations. 7. These results suggest that VIP and PACAP relax the pig ureter through smooth muscle receptors, probably of the VPAC(2) subtype, linked to a cAMP-PKA pathway. Neuronal VPAC receptors localized at motor nerves and PAC(1) receptors placed at sensory nerves and coupled to NO release, seem also to be involved in the VIP and PACAP 38 relaxations.

Bronchodilation by an inhaled VPAC(2) receptor agonist in patients with stable asthma

BACKGROUND

The synthetic vasoactive intestinal peptide (VIP) analogue Ro 25-1553 is a selective VIP-PACAP type 2 (VPAC(2)) receptor agonist that causes a bronchodilatory effect in guinea pigs in vivo. The effect of Ro 25-1553 given by inhalation to patients with asthma was studied and compared with that of a long acting beta(2) adrenoceptor agonist.

METHODS

Twenty four patients with moderate stable asthma participated in a double blind, randomised, placebo controlled, crossover study. The primary variable was bronchodilatory effect (increase in forced expiratory volume in 1 second, FEV(1)) after inhalation of Ro 25-1553 (100 microg or 600 microg) and formoterol (4.5 microg), respectively. Putative side effects were characterised by monitoring sitting blood pressure, serum potassium, electrocardiography and echocardiography.

RESULTS

Inhalation of 600 microg Ro 25-1553 caused a rapid bronchodilatory effect (geometric mean increase in FEV(1) compared with placebo) within 3 minutes of 6% (95% CI 4 to 9), as did inhalation of formoterol (8% (95% CI 5 to 10)). The corresponding maximum bronchodilatory effect during 24 hours was similar for 600 microg Ro 25-1553 (7% (95% CI 4 to 10)) and the reference bronchodilator formoterol (10% (95% CI 7 to 12)). However, for both doses of Ro 25-1553 the bronchodilatory effect was attenuated 5 hours after inhalation whereas formoterol still had a bronchodilatory effect 12 hours after inhalation. Neither Ro 25-1553 nor formoterol produced any clinically relevant side effects. No drug related difference in adverse events was observed.

CONCLUSION

Inhalation of a synthetic selective VPAC(2) receptor agonist constitutes a promising approach for bronchodilation in patients with asthma.