Novel approaches to the pharmacological blockade of gastric acid secretion

LC-MS/MS method for quick detection of vonoprazan fumarate in human plasma: Development, validation and its application to a bioequivalence study

A liquid chromatography-tandem mass spectrometry method with vonoprazan fumarate-d4 as a stable isotope-labeled internal standard was developed and validated aiming at quantification of vonoprazan fumarate in human plasma for a bioequivalence study. Chromatographic separation was achieved by acetonitrile one-step protein precipitation using a gradient elution of 0.1% formic acid aqueous solution and acetonitrile with a run time of 3.65 min. Detection was carried out on a tandem mass spectrometer in multiple reaction monitoring mode via a positive electrospray ionization interface. The multiple reaction monitoring mode of precursor-product ion transitions for vonoprazan fumarate and vonoprazan fumarate-d4 were m/z 346.0 → 315.1 and 350.0 → 316.0, respectively. The linear range was 0.150-60.000 ng/ml. This method was fully validated with acceptable results in terms of selectivity, carryover, lower limit of quantification, calibration curve, accuracy, precision, dilution effect, matrix effect, stability, recovery and incurred sample reanalysis. A successful application of this method was realized in the bioequivalence study of vonoprazan fumarate tablet (20 mg) among healthy Chinese volunteers.

Carcinogenicity assessment of tegoprazan in Sprague-Dawley (Crl:CD) rats and ICR (Crl:CD1) mice

Tegoprazan is a novel potassium-competitive acid blocker (P-CAB) that reversibly inhibits the proton pump in gastric parietal cells and has been approved for the treatment of acid-related diseases in Korea. This study aimed to evaluate the carcinogenic potential of tegoprazan in Sprague-Dawley rats and CD-1 mice. Tegoprazan was administered daily by oral gavage to rats for up to 94 weeks and mice for up to 104 weeks. Evidence of carcinogenic potential of tegoprazan was identified in rats only and was limited to benign and/or malignant neuroendocrine cell tumors at exposures >7-fold of the recommended human dose. Glandular stomach findings were considered secondary to the expected pharmacology of tegoprazan, characterized by their location in the fundic and body regions of the stomach. Overall, tegoprazan induced gastric enterochromaffin-like (ECL) cell tumors in SD rats, but did not produce any treatment-related statistically significant increase in the incidence of neoplasms relevant to humans when administered to SD rats and CD-1 mice by gavage at doses up to 300 and 150 mg/kg/day, respectively. Gastric ECL cell tumors are thought to be induced by the exaggerated indirect pharmacological effect of tegoprazan, similar to that reported for proton pump inhibitors (PPIs) and other P-CABs.

Randomised clinical trial: Safety, tolerability, pharmacodynamics and pharmacokinetics of zastaprazan (JP-1366), a novel potassium-competitive acid blocker, in healthy subjects

BACKGROUND

Zastaprazan (JP-1366) is a novel potassium-competitive acid blocker with favourable preclinical safety and efficacy profile being developed for the treatment of acid-related diseases.

AIMS

To investigate the safety, tolerability, pharmacodynamics and pharmacokinetics of zastaprazan.

METHODS

A randomised, open-label, placebo- and active-controlled, single and multiple ascending dose clinical trial was conducted in healthy Korean male subjects. Intragatric pH and serum gastrin were measured to assess the pharmacodynamics, while serial blood and urine samples were collected to assess the pharmacokinetics. Pharmacogenomic evaluation was conducted to explore genetic variants, which can affect the pharmacodynamics and pharmacokinetics. Safety and tolerability including hepatotoxicity were evaluated.

RESULTS

Suppression of gastric acid secretion increased as the dose of zastaprazan increased. The percentage of time that gastric pH was over 4 (%Time pH >4) with zastaprazan 20 mg (85.19%) and 40 mg (91.84%) were similar to or greater than that with esomeprazole 40 mg (72.06%). Zastaprazan was rapidly absorbed within 2 h and eliminated with a half-life of 6-10 h. Pharmacogenomic analysis found no genetic variant of drug metabolising enzymes including CYP2C19 or drug transporters associated with the exposure of zastaprazan. Zastaprazan was well tolerated with no clinically significant changes in safety and tolerability assessments.

CONCLUSIONS

Zastaprazan was safe and well tolerated after a single oral dose up to 60 mg and multiple oral doses up to 40 mg. It also showed rapid, potent suppression of gastric acid secretion. Pharmacodynamic and pharmacokinetic profile of zastaprazan was suitable for treatment of patients with acid-related diseases.

Design, synthesis and biological evaluation of novel 5-methyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazole derivatives as potent potassium-competitive acid blockers

With the aim to discover a novel potent potassium-competitive acid blocker (P-CAB) agent, a series of 5-methyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazole derivatives were synthesized, and their H⁺/K⁺-ATPase inhibitory activities and inhibitory action on histamine-stimulated gastric acid secretion in rats were evaluated. Among the compounds synthesized, compound 3'-((3-(2-fluorophenyl)-5-methyl-5,6-dihydropyrrolo[3,4-c]pyrazol-2(4H)-yl)methyl)-[1,1'-biphenyl]-3-carboxamide not only exhibited potent H⁺/K⁺-ATPase inhibitory activity but olso showed potent inhibitory action in vivo on histamine-stimulated gastric acid secretion. In addition, the lead compound displayed favourable oral pharmacokinetic properties in rats, which was worthy of further study as a novel P-CAB agent.

An update of pharmacology, efficacy, and safety of vonoprazan in acid-related disorders

INTRODUCTION

Patients with acid-related disorders (ARDs) of the upper digestive tract remain highly prevalent and need to be continuously investigated to improve their management.

AREAS COVERED

This review provides a summary of the most recent advancements in the treatment of ARDs with particular focus on the new drugs available to overcome the unmet needs of traditional therapies.

EXPERT OPINION

Proton pump inhibitors remain the best therapy in treating ARDs, but a consistent proportion of these patients continues to present mucosal lesions or to experience symptoms despite treatment. These cases pertain mainly to the most severe forms of erosive esophagitis or to non-erosive reflux disease. Also, the increasing rate of patients with H. pylori infection not responding to eradication therapy represents a difficult clinical condition. The recent advent of a new class of antisecretory drugs, such as the potassium competitive acid blockers and, among them the most studied vonoprazan, which are characterized by a better pharmacological profile than PPIs (rapid onset of action, longer lasting acid suppression, control of nocturnal acidity), has the potential to overcome the above-mentioned unmet needs. More research should be done to assess their efficacy in Western populations and their safety in patients treated in the long term.

Vonoprazan-Associated Gastric Mucosal Redness in Non-Helicobacter pylori-Infected and Helicobacter pylori-Eradicated Stomach

Vonoprazan-associated gastric mucosal redness is rare, and its endoscopic and pathological features remain poorly described. We report 4 cases of vonoprazan-associated gastric mucosal redness, that is, 2 cases each in non-Helicobacter pylori-infected and -eradicated stomach. In all cases, esophagogastroduodenoscopy demonstrated spotty and linear redness newly appearing in the greater curvature of the gastric body after initiation of vonoprazan but disappearing after its discontinuation. A tissue biopsy taken from the gastric mucosa with redness revealed various pathological findings and included inflammatory cell infiltration, parietal cell protrusions, oxyntic gland dilatations, congestion, focal hemorrhage with congestion beneath the basement membrane, and vacuolar degeneration of parietal cells. To our knowledge, this is the second report describing the endoscopic and pathological features of vonoprazan-associated gastric mucosal redness.

Safety, Tolerability and Pharmacokinetics of Single Ascending and Multiple Oral Doses of Tegoprazan in Healthy Chinese Subjects

BACKGROUND AND OBJECTIVES

Tegoprazan is one of the potassium-competitive acid blockers (P-CABs). It exhibits its anti-secretory effects by competitively and reversibly blocking the availability of K⁺ of the H⁺, K⁺-ATPase. This study was designed to investigate the safety and pharmacokinetics of tegoprazan in healthy Chinese subjects.

METHODS

Thirty-eight healthy Chinese subjects were recruited in this randomized, single-center, double-blind, placebo-controlled study, with a single ascending dose of 50, 100, 200 mg and a multiple dose of 100 mg for 10 days. The plasma concentration of tegoprazan was determined by a validated liquid chromatography tandem mass spectrometry (LC-MS/MS) method. Pharmacokinetics were evaluated via non-compartmental and compartmental model analysis. Safety was assessed by physical examinations, vital signs, clinical laboratory tests, and electrocardiograms.

RESULTS

No serious adverse event was observed in this study. After single-dose administration (50, 100 and 200 mg), tegoprazan was rapidly absorbed with a median maximum measure plasma concentration (T_max) at 0.5 h and declined with a terminal (elimination) half-life (t_1/2) of 3.87-4.57 h. The maximum measured plasma concentration (C_max) for tegoprazan was 813.80, 1494.60 and 2829.00 ng/mL. Meanwhile, the corresponding area under the concentration-time curve (AUC) from time zero to infinity (AUC_0-inf) was 2761.00, 5980.05 and 11,044.72 ng∙h/mL in 50, 100, 200 mg group, respectively. Dose-dependent increase was observed in the value of C_max and AUC after administration of tegoprazan 50 to 200 mg. The two-compartment model well described the pharmacokinetic profile of tegoprazan. In the steady state, no accumulation was found after repeated administration at the 100-mg dose level. No experimental differences were found based on gender.

CONCLUSIONS

Tegoprazan was well tolerated in the dose range of 50-200 mg in single- and 100 mg in multiple-dose studies. Tegoprazan shows dose linearity with oral administration after a single dose of 50 to 200 mg and less drug accumulation after 10 days of continuous administration in 100 mg.

Clarithromycin Versus Metronidazole in First-Line Helicobacter Pylori Triple Eradication Therapy Based on Resistance to Antimicrobial Agents: Meta-Analysis

Background: International treatment guidelines for Helicobacter pylori infection recommend a proton pump inhibitor (PPI)/amoxicillin/clarithromycin (CAM) regimen (PAC) or PPI/amoxicillin/metronidazole (MNZ) regimen (PAM) as first-line therapy based on culture and sensitivity testing. As incidence rates of antimicrobial agent-resistant strains are changing year by year, it is important to reevaluate the efficacy of eradication regimens. We performed a meta-analysis to evaluate the efficacy and safety of PAC and PAM based on different locations categorized by the reported incidence of CAM- and MNZ-resistant strains. Methods: Randomized control trials (RCTs) comparing eradication rates between PAC and PAM first-line treatment up to December 2018 were included. We divided RCTs into four groups based on resistance to CAM (< 15% or ≥ 15%) and MNZ (< 15% or ≥ 15%). Results: A total of 27 studies (4825 patients) were included. Overall eradication rates between PAC and PAM were similar (74.8% and 72.5%, relative risk (RR): 1.13, 95% confidence interval (CI): 0.91–1.39, P = 0.27) in the intention-to-treat analysis. In areas with low MNZ- and high CAM-resistance rates, PAM had a significantly higher eradication rate than PAC (92.5% vs. 70.8%, RR: 0.29, 95% CI: 0.13–0.68). In areas with high MNZ- and low CAM-resistance rates, the eradication rate with PAC was only 72.9%. Conclusions: Overall eradication rates with PAC and PAM were equivalent worldwide. In low MNZ-resistance areas, PAM may be recommended as first-line therapy. However, the efficacy of PAC may be insufficient, irrespective of susceptibility to CAM.

Vonoprazan-associated Gastric Mucosal Redness: A Report of Four Cases

To date, no cases of vonoprazan-associated gastric mucosal redness have been reported, and its endoscopic and pathological features remain largely unclear. We report four cases of vonoprazan-associated gastric mucosal redness. In all cases, esophagogastroduodenoscopy (EGD) demonstrated linear or spotty redness that newly appeared in the greater curvature of the middle gastric body after the initiation of vonoprazan, which disappeared after its discontinuation. A tissue biopsy taken from the gastric mucosa with redness revealed inflammatory cell infiltration, parietal cell protrusions (PCPs), and oxyntic gland dilatation. To our knowledge, this is the first report describing the endoscopic and pathological features of vonoprazan-associated gastric mucosal redness.

Optimizing proton pump inhibitors in Helicobacter pylori treatment: Old and new tricks to improve effectiveness

The survival and replication cycle of Helicobacter pylori (H. pylori) is strictly dependant on intragastric pH, since H. pylori enters replicative phase at an almost neutral pH (6-7), while at acid pH (3-6) it turns into its coccoid form, which is resistant to antibiotics. On these bases, it is crucial to increase intragastric pH by proton pump inhibitors (PPIs) when an antibiotic-based eradicating therapy needs to be administered. Therefore, several tricks need to be used to optimize eradication rate of different regimens. The administration of the highest dose as possible of PPI, by doubling or increasing the number of pills/day, has shown to be able to improve therapeutic outcome and has often proposed in rescue therapies, even if specific trials have not been performed. A pre-treatment with PPI before starting antibiotics does not seem to be effective, therefore it is discouraged. However, the choice of PPI molecule could have a certain weight, since second-generation substances (esomeprazole, rabeprazole) are likely more effective than those of first generation (omeprazole, lansoprazole). A possible explanation is due to their metabolism, which has been proven to be less dependent on cytochrome P450 (CYP) 2C19 genetic variables. Finally, vonoprazan, a competitive inhibitor of H+/K+-ATPase present on luminal membrane of gastric parietal cells has shown the highest efficacy, due to both its highest acid inhibition power and rapid pharmacologic effect. However current data come only from Eastern Asia, therefore its strong power needs to be confirmed outside this geographic area in Western countries as well as related to the local different antibiotic resistance rates.

Role of Vonoprazan in Helicobacter pylori Eradication Therapy in Japan

Complete eradication of Helicobacter pylori is important for preventing the development of gastric cancer. The outcome of H. pylori eradication therapy is mainly dependent on bacterial susceptibility to antimicrobial agents and potent neutralization of intragastric pH across 24 h, especially when using acid-sensitive antimicrobial agents such as clarithromycin (CLR), amoxicillin and sitafloxacin. However, conventional regimens comprising twice-daily doses (bid) of proton pump inhibitors (PPIs) are generally insufficient for maintaining the required gastric acid secretion for 24 h for successful eradication in all H. pylori-positive patients. Further, the increasing prevalence of CLR-resistant strains with each year has led to a decrease in eradication rates of first-line PPI- and CLR-containing therapies in developed countries, including Japan. In 2015, the potassium-competitive acid blocker vonoprazan (VPZ) became clinically available in Japan. VPZ competitively inhibits H⁺/K⁺-ATPase activity more potently than PPIs (e.g., omeprazole, lansoprazole, rabeprazole, pantoprazole, and esomeprazole). Therefore, a VPZ-containing H. pylori eradication regimen is expected to increase the eradication rate compared with conventional regimens containing a standard dose of PPI. In fact, a recent meta-analysis that investigated the efficacy of first-line eradication therapy showed that a VPZ-containing regimen achieved a higher eradication rate than a PPI-containing regimen. While the Maastricht V/Florence Consensus Report recommends selecting a bismuth or non-bismuth quadruple therapy and concomitant therapy for patients living in areas with high prevalence of CLR resistance, a VPZ-containing regimen demonstrates effectiveness for patients infected with CLR-resistant strains and patients living in areas where the prevalence of CLR-resistant strains is >15%. As a next step, studies are needed to determine the factors affecting the clinical outcome of VPZ-containing therapy and optimal VPZ-containing alternative regimens for tailored treatments. In this review, we summarize the advantages and disadvantages of VPZ in H. pylori eradication therapy.

Safety, tolerability, pharmacodynamics and pharmacokinetics of DWP14012, a novel potassium-competitive acid blocker, in healthy male subjects

BACKGROUND

A novel potassium-competitive acid blocker, DWP14012, is in clinical development as a potential alternative to proton pump inhibitors for the treatment of acid-related diseases.

AIMS

To evaluate the safety, tolerability, pharmacodynamics and pharmacokinetics of DWP14012 in humans.

METHODS

A randomised, double-blind, double-dummy, placebo- and active-controlled, single- and multiple-ascending dose (SAD and MAD, respectively) study was conducted in healthy male subjects without Helicobacter pylori infection. Subjects randomly received a single oral dose of 10-320 mg DWP14012, esomeprazole (active comparator) or placebo in the SAD study (n = 72) and once daily doses of 20-160 mg DWP14012, esomeprazole or placebo for 7 days in the MAD study (n = 48; 8:2:2). Tolerability was evaluated using a microRNA-122 assay. Pharmacodynamics were evaluated through 24-hour gastric pH monitoring, and pharmacokinetics were evaluated plasma and urine DWP14012 concentrations.

RESULTS

DWP14012 was generally well tolerated. The liver toxicity of DWP14012 was not higher than that of placebo after multiple oral administrations. DWP14012 showed rapid and sustained suppression of gastric acid secretion for 24 hours after dosing. Clear dose-response and exposure-response relationships were observed. Plasma concentrations of DWP14012 increased in a dose-proportional manner in the MAD study, whereas in the SAD study, DWP14012 did not significantly accumulate in the plasma.

CONCLUSIONS

DWP14012 was well tolerated, and showed a rapid and long-lasting gastric acid suppression effect in healthy subjects. These results justify further investigation of DWP14012 in patients with acid-related disorders.

The Use of Proton Pump Inhibitors in Intensive Care Units

The bleeding from the upper gastrointestinal tract represent a significant medical but also socio-economic problem. A special group of patients et increased risk consists of critically ill patients in intensive care units. Particularly significant cause of bleeding in intensive care unit patients is bleeding resulting from the stress ulcers caused by damage of the mucosa of the stomach and duodenum.

The purpose of this review is to present current experience in prevention of upper gastrointestinal tract bleeding using proton pump inhibitors in intensive care units.

Combination of endoscopic hemostatic methods and proton pump inhibitors represents golden standard in most cases.

Despite some adverse effects treatment with proton pump blockers is essential when upper gastrointestinal tract bleeding appears in critically ill patients in intensive care units. Proton pump inhibitors are more effective in acid suppression, as well as in the prevention of recurrent bleeding after endoscopic hemostasis than histamine 2 receptor blockers. The efficacy of proton pump blockers is higher in the case of a continuous intravenous infusion than in the intermittent mode of administration of the drug. The need for highly elaborate strategy for the prophylaxis of bleeding from the upper parts of gastrointestinal tract in intensive care units is essential, because when it occurs in intensive care units, mortality is high, and therapeutic options become narrow.

Vonoprazan: A Novel and Potent Alternative in the Treatment of Acid-Related Diseases

Although proton pump inhibitors (PPIs) have been used widely, acid-related diseases are still associated with a huge burden on the health care system. Recently, the efficacy and safety of a new acid suppressant named vonoprazan in the treatment of acid-related diseases have been evaluated by a series of studies. As a novel potassium-competitive acid blocker, vonoprazan may provide reversible acid suppression by preventing K⁺ from binding to gastric H⁺/K⁺-ATPase. It has been clinically used for the short-term treatment of gastroesophageal reflux disease (GERD), peptic ulcer disease and Helicobacter pylori (H. pylori) infection in Japan. The healing rate of GERD and gastric ulcers by vonoprazan is more than 95 and 90%, respectively; also, it is effective in curing PPI-resistant GERD. It increases H. pylori eradication rate to more than 88% as part of both first-line and second-line therapy. It is also effective in the eradication of clarithromycin-resistant H. pylori strains. All of these short-term studies show vonoprazan is safe and well-tolerated. As a safe and effective acid inhibitor, vonoprazan might be a novel alternative in the treatment of acid-related diseases.

Substituted methoxybenzyl-sulfonyl-1H-benzo[d]imidazoles evaluated as effective H+/K+-ATPase inhibitors and anti-ulcer therapeutics

Efforts were made to synthesize a series of substituted methoxybenzyl-sulfonyl-1H-benzo[d]imidazole derivatives (8a-l) and investigate their anti-ulcer therapeutics. Prior to evaluating antiulcer potentials of 8a-l, a preliminary binding assay against H⁺/K⁺-ATPase from goat gastric mucosa was carried out, since it plays an important role in the ulcer development. In order to get more insight into the binding mode of the compounds to H⁺/K⁺-ATPase, a molecular docking study was carried out and the best binding affinities were unveiled. Many of the substituted methoxybenzyl-sulfonyl-1H-benzo[d]imidazole derivatives (8a-l) were active for the proposed activity. The key finding was that, least inhibitory constant (ki) values of 8a-l were found between 0.02 and 1.8 μM in the molecular docking study. Almost the same range was reflected/correlated in the H⁺/K⁺-ATPase inhibition assay (IC₅₀ 0.14-1.29 μM). Remarkably, compounds 8a-l showed a relative activity percentage range of 72-92%. Efficient HRBC membrane stabilization activity of 8a-l ensured the non-harm/safety and the suitability/alternative towards anti-ulcer therapy.

Vonoprazan fumarate for the management of acid-related diseases

INTRODUCTION

Proton pump inhibitors (PPIs) display a number of limitations and unmet clinical needs that have prompted the development of novel drugs to improve the outcomes of acid-related diseases, including the eradication of H. pylori. In this context, a new synthesized potassium-competitive acid blocker (P-CAB), vonoprazan, showed higher suppression of gastric acid secretion. Areas covered: This review discusses the current knowledge regarding the efficacy of vonoprazan in the treatment of acid-related diseases, with a particular focus on its use in Helicobacter pylori eradication. Expert opinion: Vonoprazan showed some advantages over PPIs in terms of the pharmacokinetic and pharmacodynamic profile: fast onset of action without requiring acid activation and specific administration timing, more potent and prolonged inhibition of acid secretion, including a better nighttime acid control, and a less antisecretory variability. Recent evidence suggests that vonoprazan can be preferred to PPIs as maintenance therapy for reflux esophagitis and eradication of Helicobacter pylori owing to its stronger antisecretory effect. Moreover, vonoprazan displays favorable safety and tolerability profiles, even though long-term studies on the effects of vonoprazan are required.

Anticancer activity of Nelumbo nucifera stamen extract in human colon cancer HCT-116 cells in vitro

The aim of the present study was to investigate the anticancer activities of Nelumbo nucifera (Ba lotus) stamen ethanol crude extract (BLSEE) in human colon carcinoma HCT-116 cells. MTT assay, flow cytometry analysis and reverse transcription-polymerase chain reaction assay were employed to investigate the anticancer mechanisms of BLSEE (100, 200 and 400 µg/ml) in HCT-116 cells. BLSEE reduced HCT-116 cell proliferation in a dose-dependent manner. BLSEE treatment also significantly increased the sub-G1 population in HCT-116 cells (P=0.0020 at 400 µg/ml), as shown by flow cytometry assay. Following treatment with BLSEE, the mRNA levels of the apoptosis-associated factors Fas, Fas ligand, tumor necrosis factor-related apoptosis-inducing ligand, death receptor 4 (DR4), death receptor 5 (DR5), caspases 3, 8 and 9, and B-cell lymphoma-2 (Bcl-2) associated X protein were increased, and the expression of anti-apoptotic Bcl-2 and Bcl-extra large was decreased in HCT-116 cells. The mRNA levels of matrix metalloproteinase (MMP)-2, MMP-9, TIMP metallopeptidase inhibitor 1 and TIMP metallopeptidase inhibitor 2 were also regulated by BLSEE treatment. In addition, BLSEE was able to modulate the expression of inflammation-associated nuclear factor-κB, inhibitory κBα, inducible nitric oxide synthase and cyclooxygenase 2 in HCT-116 cells. The present study clearly indicated the cytotoxicity of BLSEE in HCT-116 cells through induced cellular apoptosis. These results also suggested the BLSEE may be a powerful agent against colon cancer cells.

The First-in-Class Potassium-Competitive Acid Blocker, Vonoprazan Fumarate: Pharmacokinetic and Pharmacodynamic Considerations

Vonoprazan fumarate (Takecab) is a first-in-class potassium-competitive acid blocker that has been available in the market in Japan since February 2015. Vonoprazan is administered orally at 20 mg once daily for the treatment of gastroduodenal ulcer, at 20 and 10 mg once daily for the treatment and secondary prevention of reflux esophagitis, respectively, at 10 mg once daily for the secondary prevention of low-dose aspirin- or non-steroidal anti-inflammatory drug-induced peptic ulcer, and at 20 mg twice daily in combination with clarithromycin and amoxicillin for the eradication of Helicobacter pylori. It inhibits H(+),K(+)-ATPase activities in a reversible and potassium-competitive manner with a potency of inhibition approximately 350 times higher than the proton pump inhibitor, lansoprazole. Vonoprazan is absorbed rapidly and reaches maximum plasma concentration at 1.5-2.0 h after oral administration. Food has minimal effect on its intestinal absorption. Oral bioavailability in humans remains unknown. The plasma protein binding of vonoprazan is 80% in healthy subjects. It distributes extensively into tissues with a mean apparent volume of distribution of 1050 L. Being a base with pKa of 9.6 and with acid-resistant properties, vonoprazan is highly concentrated in the acidic canaliculi of the gastric parietal cells and elicited an acid suppression effect for longer than 24 h after the administration of 20 mg. The mean apparent terminal half-life of the drug is approximately 7.7 h in healthy adults. Vonoprazan is metabolized to inactive metabolites mainly by cytochrome P450 (CYP)3A4 and to some extent by CYP2B6, CYP2C19, CYP2D6, and SULT2A1. A mass balance study showed that 59 and 8% of the orally administered radioactivity was recovered in urine as metabolites and in an unchanged form, respectively, indicating extensive metabolism. Genetic polymorphism of CYP2C19 may influence drug exposure but only to a clinically insignificant extent (15-29%), according to the population pharmacokinetic study performed in Japanese patients. When vonoprazan was co-administered with clarithromycin, the mean AUC from time 0 to time of the next dose (dosing interval) of vonoprazan and clarithromycin were increased by 1.8 and 1.5 times, respectively, compared with the corresponding control values, indicating mutual metabolic inhibition. The mean area under the curve from time zero to infinity obtained from patients with severe liver and renal dysfunction were elevated by 2.6 and 2.4 times, respectively, compared with healthy subjects, with no significant changes in plasma protein binding. Vonoprazan increases intragastric pH above 4.0 as early as 4 h after an oral dose of 20 mg, and the extensive anti-secretory effect is maintained up to 24 h post-dose. During repeated dosing of 20 mg once daily, the 24-h intragastric pH >4 holding time ratios were 63 and 83 % on days 1 and 7, respectively. Because vonoprazan elicited a more extensive gastric acid suppression than the proton pump inhibitor, lansoprazole, it also gave rise to two to three times greater serum gastrin concentrations as compared with lansoprazole. In pre-approval clinical studies for the treatment of acid-related disorders, mild to moderate adverse drug reactions (mostly constipation or diarrhea) occurred at frequencies of 8-17%. Neither severe liver toxicity nor neuroendocrine tumor has been reported in patients receiving vonoprazan.

Vonoprazan-based therapy for Helicobacter pylori eradication: experience and clinical evidence

Stable suppression of gastric acid secretion is a crucial factor in Helicobacter pylori eradication. Vonoprazan is a potassium-competitive acid blocker recently approved for use in Japan. As vonoprazan has a long duration of action and causes rapid and strong inhibition of gastric acid secretion, it has gained clinical attention for treating erosive oesophagitis, peptic ulcers, and H. pylori infection. In this review, we discuss the recent knowledge regarding the safety and efficacy of vonoprazan, focusing on its use in H. pylori eradication. The latest literature and our clinical experience have shown that vonoprazan-based therapies have satisfactory eradication rates. Additionally, vonoprazan-based therapies are associated with similar rates of adverse events as standard triple therapies with conventional proton-pump inhibitors.

Potassium-competitive acid blockers: Advanced therapeutic option for acid-related diseases

Acid-related diseases (ARDs), such as peptic ulcers and gastroesophageal reflux disease, represent a major health-care concern. Some major milestones in our understanding of gastric acid secretion and ARD treatment reached during the last 50years include 1) discovery of histamine H₂-receptors and development of H₂-receptor antagonists, 2) identification of H⁺,K⁺-ATPase as the parietal cell proton pump and development of proton pump inhibitors (PPIs), and 3) identification of Helicobacter pylori (H. pylori) as the major cause of peptic ulcers and development of effective eradication regimens. Although PPI treatments have been effective and successful, there are limitations to their efficacy and usage, i.e. short half-life, insufficient acid suppression, slow onset of action, and large variation in efficacy among patients due to CYP2C19 metabolism. Potassium-competitive acid blockers (P-CABs) inhibit H⁺,K⁺-ATPase in a reversible and K⁺-competitive manner, and exhibit almost complete inhibition of gastric acid secretion from the first dose. Many pharmaceutical companies have tried to develop P-CABs, but most of their clinical development has been discontinued due to safety concerns or a similar efficacy to PPIs. Revaprazan was developed in Korea and was the first P-CAB approved for sale. Vonoprazan, approved in 2014 in Japan, has a completely different chemical structure and higher pKa value compared to other P-CABs, and exhibits rapid onset of action and prolonged control of intragastric acidity. Vonoprazan is an effective treatment for ARDs that is especially effective in healing reflux esophagitis and for H. pylori eradication. P-CABs, such as vonoprazan, promise to further improve the management of ARDs.

Potent acid inhibition by vonoprazan in comparison with esomeprazole, with reference to CYP2C19 genotype

BACKGROUND

Acid inhibitory effects of proton pump inhibitors (PPIs) are influenced by CYP2C19 genotype. In contrast, the potent acid inhibition of vonoprazan is not influenced by CYP2C19 genotype.

AIM

To compare the acid inhibitory effects of vonoprazan and esomeprazole in relation to CYP2C19 genotype.

METHODS

Twenty-eight healthy Japanese volunteers [7 CYP2C19 poor metabolisers (PMs), 11 intermediate metabolisers (IMs) and 10 rapid metabolisers (RMs)] received four different regimens in a randomised crossover manner: (i) vonoprazan 20 mg twice daily (b.d.), (ii) vonoprazan 20 mg daily, (iii) esomeprazole 20 mg b.d. and (iv) esomeprazole 20 mg daily. The timing of each dosing was 1 h before a meal. Twenty-four-hour intragastric pH monitoring was performed on day 7 on each regimen.

RESULTS

In the overall genotype group, pH ≥4 holding time ratios (pH 4 HTRs) with vonoprazan b.d., vonoprazan daily, esomeprazole b.d. and esomeprazole daily were 100%, 95%, 91%, and 68% respectively. pH 5 HTRs were 99%, 91%, 84% and 54% respectively. Vonoprazan b.d. potently suppressed acid for 24 h, and was significantly superior to other regimens irrespective of CYP2C19 genotype. Vonoprazan daily was equivalent to esomeprazole b.d. in IMs and PMs, but superior in RMs. CYP2C19 genotype-dependent differences were observed in esomeprazole daily but not in vonoprazan b.d. or daily.

CONCLUSION

Vonoprazan 20 mg b.d. inhibits acid irrespective of CYP2C19 genotype, more potently than esomeprazole 20 mg b.d., pH 4 and 5 holding time ratios reached 100% and 99%, respectively.

Synthetic studies of five-membered heteroaromatic derivatives as potassium-competitive acid blockers (P-CABs)

On the basis of a series of novel and potent potassium-competitive acid blockers represented by 1-sulfonylpyrrole derivative 7, we prepared several five-membered heterocyclic analogues (8) and evaluated their H(+),K(+)-ATPase activities in vitro. We also assessed the role of the methylaminomethyl side chain by comparison with methylamino and ethylamino derivatives. We observed that the five-membered core ring and its orientation affect inhibitory activity and that the methylaminomethyl moiety is the best side chain. On the basis of potency and ligand-lipophilicity efficiency, compound 7 remains the most drug-like of the compounds studied to date. This study revealed the factors necessary for potent H(+),K(+)-ATPase inhibition, such as differences in electron density, the properties of the lone pair at each apical position of the heteroaromatic ring, and the geometry of the substituents.

Design, synthesis and pharmacological evaluation of omeprazole-like agents with anti-inflammatory activity

A new series of novel benzimidazole derivatives containing substituted pyrid-2-yl moiety and polyhydroxy sugar conjugated to the N-benzimidazole moiety has been synthesized and evaluated as orally bioavailable anti-inflammatory agents with anti-ulcerogenic activity. The anti-inflammatory and anti-ulcerogenic activities of these compounds were compared to diclofenac and omeprazole, respectively. In carrageenan-induced paw oedema assay, 2-methyl-N-((3,4-dimethoxypyridin-2-yl)methyl)-1H-benzimidazol-5-amine (12d) and 1-(1,2,3,5-tetrahydroxy-α-D-mannofuranose)-5-(((3,4-dimethoxypyridin-2yl)methyl)amino)-2-methyl-1H-benzimidazole (15d) displayed dose-dependent anti-inflammatory activities by decreasing the inflammation by 62% and 72%, respectively which is comparable to that of diclofenac (73%). In contrast to diclofenac, the anti-inflammatory activity of these compounds was not only free from any side effects on the gastric mucosa but also showed significant anti-ulcerogenic activity in rat pyloric ligation and ethanol-induced gastric ulcer models similar to that of omeprazole. Together, these findings suggest that 12d and 15d are potent anti-inflammatory agents with concurrent anti-ulcerogenic activity and support its clinical promise as a component of therapeutic strategies for inflammation, for which the gastric side effects are always a major limitation.

Discovery of a novel pyrrole derivative 1-[5-(2-fluorophenyl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine fumarate (TAK-438) as a potassium-competitive acid blocker (P-CAB)

In our pursuit of developing a novel and potent potassium-competitive acid blocker (P-CAB), we synthesized pyrrole derivatives focusing on compounds with low log D and high ligand-lipophilicity efficiency (LLE) values. Among the compounds synthesized, the compound 13e exhibited potent H(+),K(+)-ATPase inhibitory activity and potent gastric acid secretion inhibitory action in vivo. Its maximum efficacy was more potent and its duration of action was much longer than those of proton pump inhibitors (PPIs). Therefore, compound 13e (1-[5-(2-fluorophenyl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine fumarate, TAK-438) was selected as a drug candidate for the treatment of gastroesophageal reflux disease (GERD), peptic ulcer, and other acid-related diseases.

1-[5-(2-Fluorophenyl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine monofumarate (TAK-438), a novel and potent potassium-competitive acid blocker for the treatment of acid-related diseases

Proton pump inhibitors (PPIs) are widely used in the treatment of acid-related diseases. However, several unmet medical needs, such as suppression of night-time acid secretion and rapid symptom relief, remain. In this study, we investigated the pharmacological effects of 1-[5-(2-fluorophenyl)-1-(pyridin-3-ylsulfonyl)-1H-pyrrol-3-yl]-N-methylmethanamine monofumarate (TAK-438), a novel potassium-competitive acid blocker (P-CAB), on gastric acid secretion in comparison with lansoprazole, a typical PPI, and SCH28080 [3-(cyanomethyl)-2-methyl,8-(phenylmethoxy)imidazo(1,2-a)pyridine], a prototype of P-CAB. TAK-438, SCH28080, and lansoprazole inhibited H(+),K(+)-ATPase activity in porcine gastric microsomes with IC(50) values of 0.019, 0.14, and 7.6 μM, respectively, at pH 6.5. The inhibitory activity of TAK-438 was unaffected by ambient pH, whereas the inhibitory activities of SCH28080 and lansoprazole were weaker at pH 7.5. The inhibition by TAK-438 and SCH28080 was reversible and achieved in a K(+)-competitive manner, quite different from that by lansoprazole. TAK-438, at a dose of 4 mg/kg (as the free base) orally, completely inhibited basal and 2-deoxy-d-glucose-stimulated gastric acid secretion in rats, and its effect on both was stronger than that of lansoprazole. TAK-438 increased the pH of gastric perfusate to a higher value than did lansoprazole or SCH28080, and the effect of TAK-438 was sustained longer than that of lansoprazole or SCH28080. These results indicate that TAK-438 exerts a more potent and longer-lasting inhibitory action on gastric acid secretion than either lansoprazole or SCH28080. TAK-438 is a novel antisecretory drug that may provide a new option for the patients with acid-related disease that is refractory to, or inadequately controlled by, treatment with PPIs.

Insight into the structural requirements of proton pump inhibitors based on CoMFA and CoMSIA studies

In the present study, a series of 179 quinoline and quinazoline heterocyclic analogues exhibiting inhibitory activity against Gastric (H+/K+)-ATPase were investigated using the comparative molecular field analysis (CoMFA) and comparative molecular similarity indices (CoMSIA) methods. Both the models exhibited good correlation between the calculated 3D-QSAR fields and the observed biological activity for the respective training set compounds. The most optimal CoMFA and CoMSIA models yielded significant leave-one-out cross-validation coefficient, q(2) of 0.777, 0.744 and conventional cross-validation coefficient, r(2) of 0.927, 0.914 respectively. The predictive ability of generated models was tested on a set of 52 compounds having broad range of activity. CoMFA and CoMSIA yielded predicted activities for test set compounds with r(pred)(2) of 0.893 and 0.917 respectively. These validation tests not only revealed the robustness of the models but also demonstrated that for our models r(pred)(2) based on the mean activity of test set compounds can accurately estimate external predictivity. The factors affecting activity were analyzed carefully according to standard coefficient contour maps of steric, electrostatic, hydrophobic, acceptor and donor fields derived from the CoMFA and CoMSIA. These contour plots identified several key features which explain the wide range of activities. The results obtained from models offer important structural insight into designing novel peptic-ulcer inhibitors prior to their synthesis.

A randomized, comparative study of three doses of AZD0865 and esomeprazole for healing of reflux esophagitis

BACKGROUND & AIMS

AZD0865 belongs to a new class of acid-suppressing agents with rapid onset of action and potent acid inhibition. We evaluated its effectiveness for healing reflux esophagitis.

METHODS

One thousand five hundred twenty-one patients with Los Angeles A-D esophagitis and heartburn of moderate or severe intensity for > or = 4 days/week were randomized to AZD0865 25, 50, or 75 mg or esomeprazole 40 mg once daily for 4-8 weeks. The primary end point was esophagitis healing by AZD0865 at 4 weeks. Healing and control of heartburn were also assessed at 2, 4, and 8 weeks for AZD0865 and esomeprazole.

RESULTS

After 4 weeks of treatment, healing rates were similar among AZD0865 doses (76.9%; confidence interval [CI], 72.4%-81.1%); 78.2% (CI, 73.7%-82.3%), and 81.1% (CI, 76.7%-84.9%) for 25, 50, and 75 mg, respectively). The healing rate with esomeprazole at 4 weeks was similar (81.9%; CI, 77.6%-88.7%), and healing rates also were comparable among all treatments at 2 and 8 weeks. There were no significant differences in heartburn control among treatments. AZD0865 and esomeprazole were well-tolerated, although reversible increases in transaminases occurred in a small number of patients receiving AZD0865, especially at the 75-mg dose.

CONCLUSIONS

AZD0865 25, 50, and 75 mg provided similar efficacy to esomeprazole 40 mg in terms of esophagitis healing and heartburn control. These findings suggest that increasing the degree of acid inhibition beyond that already achieved by esomeprazole 40 mg (or AZD0865 25 mg) does not translate into increased clinical efficacy in esophagitis patients.

Preparation of tetrahydroimidazo[2,1-a]isoquinolines and their use as inhibitors of gastric acid secretion

A series of novel tetrahydroimidazo[2,1-a]isoquinolines was prepared based on a hetero Diels-Alder reaction between an enamine and 1,2,4-triazine as key step. A structure-activity relationship was established focussing on the influence of the substitution pattern in position 3 and 6 of the heterocycle on antisecretory activity, lipophilicity, and pK(a) value. Potent inhibitors of the gastric acid pump were identified.

Systematic expression profiling of the gastric H+/K+ ATPase in human tissue

OBJECTIVE

The potassium-competitive acid blockers (P-CABs), comprise a new, innovative group of competitive and reversible inhibitors of the gastric H+/K+ ATPase. Our aim was to identify sites of expression of the H+/K+ ATPase that are potential targets of these compounds by examining the expression profile of the gastric H+/K+ ATPase in the human body from a broad range of tissues.

MATERIAL AND METHODS

Expression profiling was done by quantitative mRNA analysis (TaqMan PCR). Tissues that were mRNA-positive for the alpha subunit were investigated further by Western blot and immunohistochemistry (IHC) for the presence of gastric H+/K+ ATPase protein.

RESULTS

In addition to the very high expression levels in the stomach, the adrenal gland, cerebellum and pancreas gave unexpectedly positive mRNA signals for the alpha subunit of gastric H +/K+ ATPase. However, they were negative for mRNA of the beta subunit, and Western blot and IHC were negative for alpha and beta subunit protein. Another group of tissues with low alpha subunit mRNA expression including the frontal cortex, cortex grey matter, testis, thymus and larynx submucosa were also found negative for both alpha and beta subunit protein. In contrast to mouse kidney, no gastric H+/K+ ATPase could be detected in human kidney.

CONCLUSIONS

We therefore conclude that the only organ in humans expressing significant levels of the P-CAB target gastric H+/K+ ATPase is the stomach.

Novel indanyl-substituted imidazo[1,2-a]pyridines as potent reversible inhibitors of the gastric H+/K+-ATPase

A series of novel 8-indanylamino- and 8-indanyloxy-substituted imidazo[1,2-a]pyridines with reduced lipophilicity was synthesized from easily accessible starting compounds. The anti-secretory activity of these compounds has been assessed in a competitive binding assay against H(+)/K(+)-ATPase from hog gastric mucosa. Some of the compounds proved to be potent inhibitors of the gastric acid pump.

Role of CCK/gastrin receptors in gastrointestinal/metabolic diseases and results of human studies using gastrin/CCK receptor agonists/antagonists in these diseases

In this paper, the established and possible roles of CCK1 and CCK2 receptors in gastrointestinal (GI) and metabolic diseases are reviewed and available results from human agonist/antagonist studies are discussed. While there is evidence for the involvement of CCK1R in numerous diseases including pancreatic disorders, motility disorders, tumor growth, regulation of satiety and a number of CCK-deficient states, the role of CCK1R in these conditions is not clearly defined. There are encouraging data from several clinical studies of CCK1R antagonists in some of these conditions, but their role as therapeutic agents remains unclear. The role of CCK2R in physiological (atrophic gastritis, pernicious anemia) and pathological (Zollinger-Ellison syndrome) hypergastrinemic states, its effects on the gastric mucosa (ECL cell hyperplasia, carcinoids, parietal cell mass) and its role in acid-peptic disorders are clearly defined. Furthermore, recent studies point to a possible role for CCK2R in a number of GI malignancies. Current data from human studies of CCK2R antagonists are presented and their potential role in the treatment of these conditions reviewed. Furthermore, the role of CCK2 receptors as targets for medical imaging is discussed.