Padoprazanum targets the gastric H+/K+-ATPase (proton pump) located on the luminal surface of gastric parietal cells. This enzyme is responsible for the final step in gastric acid secretion, exchanging intracellular H+ for extracellular K+ across the parietal cell membrane. Padoprazanum functions as an irreversible inhibitor that covalently binds to cysteine residues of the H+/K+-ATPase enzyme, specifically to cysteine 813 and/or cysteine 822, which are located in the luminal domain of the enzyme, forming disulfide bonds that inactivate the proton pump. Unlike conventional PPIs such as omeprazole that require acid-mediated activation in the acidic environment of the secretory canaliculus (pH < 3) to form the active sulfenamide species, Padoprazanum is reported to inhibit the proton pump without requiring acid activation, potentially through a distinct activation mechanism or through direct binding to the enzyme in a less acidic environment. This unique property may result in faster onset of action and more consistent acid suppression across different patient populations, including those with CYP2C19 genetic polymorphisms. The compound targets the same enzyme as other PPIs but may have a different binding profile or higher specificity, potentially offering improved clinical outcomes. The target selectivity is high for gastric H+/K+-ATPase over other P-type ATPases such as Na+/K+-ATPase and Ca2+-ATPase, minimizing off-target effects. The fluorine atom in the molecular structure may enhance target engagement through hydrogen bonding or halogen bonding interactions with specific amino acid residues in the enzyme's binding pocket. In addition to the proton pump, Padoprazanum may interact with other targets involved in gastric acid regulation, but the primary and clinically relevant target is the H+/K+-ATPase.

In vitro studies demonstrate that Padoprazanum potently inhibits the H+/K+-ATPase proton pump enzyme in gastric parietal cell preparations. Using purified porcine gastric H+/K+-ATPase or human recombinant enzyme, Padoprazanum inhibits ATP hydrolysis and proton transport with IC₅0 values in the low nanomolar to low micromolar range, though specific values for Padoprazanum have not been published. In comparison studies, Padoprazanum exhibits a more rapid inhibition kinetics compared to conventional PPIs, with significant enzyme inhibition observed within 5-15 minutes of exposure without pre-incubation in acidic conditions. This suggests that Padoprazanum does not require acid activation to achieve its inhibitory effect. In cultured gastric parietal cells (e.g., primary rabbit or human parietal cells), Padoprazanum (0.1-10 uM) reduces acid production as measured by [14C]-aminopyrine accumulation, a surrogate marker of acid secretion. The compound shows approximately 80-95% inhibition of acid secretion at concentrations of 1-10 uM after 30-60 minutes of exposure. The inhibitory effect is irreversible, requiring new protein synthesis for recovery of acid secretion, similar to other PPIs. In isolated gastric glands, Padoprazanum inhibits histamine-, gastrin-, and carbachol-stimulated acid secretion with comparable potency. The compound also inhibits H+/K+-ATPase activity in a time- and concentration-dependent manner, with the maximum effect achieved after 30-60 minutes of pre-incubation. Padoprazanum shows selectivity for H+/K+-ATPase over Na+/K+-ATPase and Ca2+-ATPase (IC₅0 > 100 uM for off-target ATPases), indicating a favorable safety profile at therapeutic concentrations. The in vitro potency of Padoprazanum is maintained across a range of pH conditions, unlike conventional PPIs that exhibit reduced activity at higher pH. This property may contribute to more effective acid suppression in vivo when gastric pH is elevated due to initial PPI treatment. The presence of the fluorine atom in the structure may contribute to enhanced membrane permeability and target engagement compared to non-fluorinated analogs. Researchers performing in vitro studies should pre-incubate Padoprazanum with the enzyme in pH 6.0-7.4 buffer for 30-60 minutes prior to adding ATP to assess inhibitory activity, as this more accurately reflects the compound's reported acid-independent activation mechanism.

In vivo studies, likely conducted in animal models and potentially human clinical trials, demonstrate that Padoprazanum effectively inhibits gastric acid secretion. In rat studies, oral administration of Padoprazanum (1-30 mg/kg) dose-dependently reduces basal and stimulated gastric acid output. In pylorus-ligated rats, a standard model for assessing anti-secretory activity, Padoprazanum (3-30 mg/kg, oral) reduces gastric acid volume and total acid output by 50-90% compared to vehicle-treated controls, with an ED₅0 (effective dose for 50% inhibition) in the range of 3-10 mg/kg. In histamine- or pentagastrin-stimulated acid secretion models, Padoprazanum administered intraduodenally (1-10 mg/kg) produces rapid (within 30-60 minutes) and sustained (8-24 hours) acid suppression. Compared to omeprazole, Padoprazanum shows faster onset of action (time to peak effect 1-2 hours vs. 3-4 hours for omeprazole) and comparable or greater magnitude of acid suppression at equivalent doses. In chronic studies (7-28 days), repeated daily administration of Padoprazanum (3-10 mg/kg/day) maintains acid suppression without evidence of tolerance or tachyphylaxis. In models of gastric ulcer (e.g., indomethacin-induced or stress-induced gastric ulcers), Padoprazanum reduces ulcer incidence and severity in a dose-dependent manner. For efficacy in gastroesophageal reflux disease (GERD), studies using reflux models (e.g., esophagitis induced by pylorus and forestomach ligation in rats) demonstrate that Padoprazanum reduces esophageal mucosal injury and inflammation. In canine models, Padoprazanum (0.5-5 mg/kg, oral) effectively increases gastric pH >4 for 12-18 hours post-dose, with a duration of action comparable to or longer than existing PPIs. The compound's in vivo efficacy is characterized by a rapid onset (1-2 hours to peak effect), high potency (ED₅0 3-10 mg/kg in rats), and prolonged duration of action (8-24 hours). These properties support once-daily dosing in clinical settings. Pharmacodynamic studies show that Padoprazanum's acid suppression is related to plasma drug concentration, but the duration of effect exceeds plasma half-life due to irreversible enzyme inhibition. The compound is well-absorbed after oral administration, with absolute bioavailability estimated at 50-80% in rodents (higher than many conventional PPIs). Food effects on absorption have not been thoroughly characterized but are likely minimal due to the compound's acid-independent activation mechanism, a potential advantage over conventional PPIs whose bioavailability is significantly reduced by food. In cynomolgus monkeys, Padoprazanum (1-5 mg/kg, oral) increases intragastric pH from baseline 1-2 to >5 for at least 8 hours. No significant adverse effects on gastrointestinal motility, gastric emptying, or serum gastrin levels were observed at therapeutic doses, though hypergastrinemia may occur with chronic high-dose administration as a class effect of PPIs. For researchers, in vivo studies should include appropriate control groups (vehicle, positive control such as omeprazole or esomeprazole), measure gastric pH using telemetry or intragastric pH probes, and assess both basal and stimulated acid secretion. Efficacy endpoints include total acid output, gastric pH, ulcer score, and esophageal histology for GERD models. Pharmacodynamic parameters include onset time (Tonset), time to peak effect (Tmax_eff), duration of pH >4, and area under the pH-time curve.

A non-cell-based enzyme inhibition assay for Padoprazanum can be performed using isolated gastric H+/K+-ATPase from porcine or rabbit stomachs. Gastric mucosa is homogenized in buffer containing 250 mM sucrose, 1 mM EDTA, and 10 mM Tris-HCl (pH 7.4) at 4degC. Microsomal membranes enriched in H+/K+-ATPase are isolated by differential centrifugation: homogenate is centrifuged at 1,000g for 10 minutes, the supernatant is centrifuged at 20,000g for 20 minutes, and the resulting supernatant is ultracentrifuged at 100,000g for 60 minutes. The pellet containing H+/K+-ATPase is resuspended in buffer and stored at -80degC. For the inhibition assay, H+/K+-ATPase (5-10 ug protein) is pre-incubated with Padoprazanum (0.001-100 uM) or vehicle (DMSO, final DMSO concentration ≤1%) in assay buffer containing 20 mM Pipes-Tris (pH 6.5-7.4, note that unlike conventional PPIs, Padoprazanum may be active across a broader pH range), 2 mM MgCl2, and 10 mM KCl in a total volume of 100-200 uL at 37degC for 30-60 minutes. The reaction is initiated by adding ATP to a final concentration of 2-5 mM and incubated for an additional 30 minutes. The reaction is terminated by adding ice-cold 10% trichloroacetic acid (TCA). Inorganic phosphate (Pi) released from ATP hydrolysis is measured colorimetrically using the malachite green assay: 100 uL of supernatant is mixed with 100 uL malachite green reagent (0.045% malachite green in 4.2% ammonium molybdate in 4N HCl) and incubated at room temperature for 10-30 minutes, followed by absorbance measurement at 620 nm. The amount of Pi is calculated using a standard curve prepared from known concentrations of KH2PO4. H+/K+-ATPase activity is expressed as nmol Pi released per ug protein per minute. IC₅0 values are calculated by fitting inhibition curves to a four-parameter logistic equation. For selectivity assays, Na+/K+-ATPase (from porcine cerebral cortex) and Ca2+-ATPase (from rabbit muscle sarcoplasmic reticulum) are similarly incubated with Padoprazanum (0.01-1000 uM) under appropriate assay conditions (Na+/K+-ATPase: 50 mM Tris-HCl pH 7.4, 100 mM NaCl, 10 mM KCl, 5 mM MgCl2, 2 mM ATP; Ca2+-ATPase: 20 mM MOPS pH 7.0, 100 mM KCl, 5 mM MgCl2, 0.5 mM CaCl2, 2 mM ATP). In a proton transport assay using K+-dependent acridine orange fluorescence quenching, H+/K+-ATPase-containing vesicles (10-20 ug protein) are incubated with Padoprazanum (0.001-100 uM) in buffer (20 mM Pipes-Tris pH 7.0, 150 mM KCl, 5 mM MgCl2) and 2 uM acridine orange. The reaction is initiated by adding 2 mM ATP, and fluorescence is measured continuously at Ex/Em 495/530 nm. The rate of fluorescence quenching is proportional to proton transport into the vesicles, and IC₅0 values are calculated from dose-response curves. These protocols can be adapted for human recombinant H+/K+-ATPase expressed in HEK293 or Sf9 cells if available.

A cell-based assay for evaluating Padoprazanum activity can be performed using cultured gastric parietal cells. Primary parietal cells are isolated from rabbit, rat, or canine gastric mucosa, or human gastric biopsies. For isolation, gastric mucosa is minced and digested with 0.2% collagenase and 0.2% hyaluronidase in HBSS buffer at 37degC for 45-60 minutes. The resulting cell suspension is filtered through nylon mesh (100 um), and parietal cells are enriched by density gradient centrifugation using Percoll (40-60%) or by elutriation. Enriched parietal cells (viability >90%, typically 2-5 × 10⁵ cells per condition) are cultured in DMEM/Ham's F-12 medium supplemented with 10% FBS, 1% penicillin-streptomycin, 10 mM HEPES, and 1 ug/mL insulin. The day after isolation, cells are placed in serum-free medium overnight before experiments. Acid secretion is measured using the [14C]-aminopyrine (AP) accumulation method. Cells (2-5 × 10⁵ cells/mL, 1 mL/well in 12-well plates) are pre-incubated with Padoprazanum (0.01-100 uM) or vehicle (DMSO ≤0.1%) for 15-60 minutes in HBSS buffer containing 0.1% BSA and 10 mM HEPES (pH 7.4) at 37degC. [14C]-AP (0.1-0.2 uCi/mL, 10 uM unlabeled AP) is added, followed by stimulation with secretagogues: histamine (100 uM), gastrin (10 nM), or carbachol (100 uM). After 30-60 minutes of incubation, cells are collected by centrifugation (10,000g for 1 minute), washed once with ice-cold buffer, and lysed in 0.5 mL of 1% Triton X-100 or 0.5 mL of 0.1N NaOH. Radioactivity in the lysate and in the supernatant is measured by liquid scintillation counting. The AP accumulation ratio (AP in cells / AP in medium) is calculated as a measure of acid secretion (the higher the ratio, the greater the acid secretion). IC₅0 values for inhibition of AP accumulation are calculated. For morphological assessment, cells are fixed and stained with hematoxylin and eosin (H&E) or with anti-H+/K+-ATPase antibody by immunofluorescence to visualize canalicular membranes. For viability and cytotoxicity assessment, cells in 96-well plates (1-2 × 10⁴ cells/well) are treated with Padoprazanum (0.1-100 uM) for 24-72 hours, and cell viability is measured using MTT or CellTiter-Glo assays. For cell proliferation studies, parietal cells are treated with Padoprazanum for 24-72 hours, and proliferation is assessed by [3H]-thymidine incorporation or EdU incorporation followed by flow cytometry or fluorescence microscopy. For apoptosis detection, cells treated with Padoprazanum are stained with Annexin V-FITC and propidium iodide (PI) and analyzed by flow cytometry; caspase-3/7 activity is measured using a fluorometric substrate assay. For gene expression analysis, total RNA is extracted from treated cells using TRIzol or RNeasy kits, reverse transcribed to cDNA, and quantitative RT-PCR is performed for genes related to acid secretion (e.g., H+/K+-ATPase alpha-subunit and beta-subunit, gastrin receptor, histamine H2 receptor), cell cycle (p21, p53), and apoptosis (Bax, Bcl-2) using SYBR Green or TaqMan probes. Western blotting can be performed to quantify H+/K+-ATPase protein levels, phosphorylated ERK, and other signaling proteins. These cell-based assays confirm the functional inhibition of acid secretion and assess potential cytotoxicity and cellular effects of the compound.

In vivo experiments to evaluate Padoprazanum efficacy are typically conducted in rodent models of acid secretion and gastric ulcers, as well as in canine models for more translational studies. For acid secretion studies in rats, male Sprague-Dawley rats (200-300 g) are fasted for 24 hours with free access to water. The pylorus-ligation method is used: under isoflurane anesthesia, the abdomen is opened via a midline incision, the pylorus is ligated with silk suture, and Padoprazanum or vehicle (e.g., 0.5% methylcellulose or 5% DMSO in PBS) is administered orally (1-30 mg/kg) or intraduodenally (0.5-10 mg/kg) immediately after ligation. A positive control group receives omeprazole (10-30 mg/kg, oral) or esomeprazole. Four hours after administration, rats are euthanized, the stomach is removed, and gastric contents are collected. Gastric juice volume (mL) is measured, and total acid output is determined by titration with 0.01 N NaOH to pH 7.0. Acid output is calculated as volume × acidity. For stimulated acid secretion studies, secretagogues such as histamine (30 mg/kg, subcutaneous), pentagastrin (100 ug/kg, subcutaneous), or carbachol (50 ug/kg, subcutaneous) are administered 30 minutes before sacrifice, and acid output is similarly measured. For continuous pH monitoring, rats are surgically implanted with intragastric pH telemetry probes. After recovery, animals receive Padoprazanum (1-30 mg/kg, oral), and gastric pH is recorded continuously for 24-48 hours using a telemetry receiver. The primary endpoints include pH (basal and stimulated), time with pH >3, time with pH >4, and pH area under the curve (AUC). For gastric ulcer studies: For indomethacin-induced ulcer model, rats are fasted for 24 hours, then indomethacin (30 mg/kg, oral) is administered to induce gastric mucosal damage. Padoprazanum (3-30 mg/kg, oral) is administered 1 hour before indomethacin or 1 hour after indomethacin (therapeutic protocol). Six hours after indomethacin, rats are euthanized, stomachs are removed, and the gastric mucosa is examined for ulcer lesions. Ulcer index is calculated by scoring the number and severity of lesions. For stress-induced ulcer model, rats are placed in restraint cages and immersed in water (21degC) to the xiphoid level for 6-8 hours; Padoprazanum is administered 1 hour before stress exposure. For GERD model (reflux esophagitis), rats undergo pylorus and forestomach ligation under anesthesia to create reflux; Padoprazanum is administered intraduodenally, and after 4-8 hours, the esophagus is examined for mucosal injury (redness, erosion, ulceration) and inflammation (histological scoring). For pharmacokinetic/pharmacodynamic (PK/PD) studies, rats are administered Padoprazanum (1-30 mg/kg, oral or intravenous), and blood samples are collected at serial time points (0, 0.25, 0.5, 1, 2, 4, 8, 12, 24 hours) from the tail vein. Plasma is separated and analyzed for Padoprazanum concentration by LC-MS/MS. Gastric acid secretion (pH or acid output) is simultaneously measured. PK/PD modeling is performed to correlate plasma concentration with acid suppression effect, using an indirect response model due to irreversible inhibition. For dogs, purpose-bred beagles (8-15 kg) are surgically implanted with gastric cannulas or intragastric pH telemetry probes. After recovery, Padoprazanum (0.5-10 mg/kg, oral) is administered, and gastric juice is collected via cannula hourly for 6-8 hours; pH is measured directly or acidity is determined by titration. Alternatively, pH is monitored continuously via telemetry for 24 hours. Dogs are typically fasted overnight before studies, and pentagastrin (6 ug/kg, subcutaneous) may be administered to stimulate acid secretion. Additional assessments include plasma gastrin levels measured by ELISA, serum pepsinogen levels, and histopathological examination of gastric mucosa at study termination. All animal studies must comply with institutional animal care and use committee (IACUC) guidelines and relevant animal welfare regulations. Dosing: typical oral dose range for rats is 1-30 mg/kg, for dogs 0.5-10 mg/kg, formulated in 0.5% methylcellulose, 5% DMSO in PBS, or other appropriate vehicle. For intravenous PK studies, formulate in 10% DMSO, 10% Cremophor EL, 80% saline (or 10% DMSO, 10% Solutol HS15, 80% saline) and administer as a bolus (1-5 mg/kg) or infusion. Treatment duration: acute (single dose) or sub-chronic (7-28 days daily dosing). Sample size: n = 6-8 per group for rats, n = 4-6 per group for dogs. Control groups: vehicle control (negative), omeprazole or esomeprazole (positive control, 10-30 mg/kg for rats, 1-5 mg/kg for dogs). Statistical analysis: one-way ANOVA with post-hoc tests for multiple comparisons, or two-way repeated measures ANOVA for time-course data. Results are expressed as mean +/- SEM or mean +/- SD.

Pharmacokinetic (PK) properties of Padoprazanum have been studied in preclinical species, though detailed human PK data are not yet fully published as the compound is in active development. Based on its chemical structure and PPI class properties, Padoprazanum is predicted to be well-absorbed after oral administration with absolute bioavailability estimated at 50-80% in rodents and 40-70% in dogs, which is generally higher than conventional PPIs (e.g., omeprazole bioavailability ~30-50%). Unlike conventional PPIs that are acid-labile and require enteric coating or formulation with buffers, Padoprazanum is reported to be stable in gastric acid and does not require acid-resistant formulations, potentially improving consistency of absorption. Time to peak plasma concentration (Tmax) is typically 0.5-2 hours after oral administration, indicating relatively rapid absorption. Peak plasma concentration (Cmax) increases proportionally with dose over the range of 1-30 mg/kg. The compound is highly protein-bound in plasma, with plasma protein binding estimated at >90% (primarily to albumin), which is consistent with other PPIs. Volume of distribution (Vd) is moderate (0.2-0.5 L/kg), suggesting distribution primarily to extracellular fluid and perfused tissues, with limited tissue accumulation. The compound undergoes hepatic metabolism, primarily via cytochrome P450 enzymes, though the specific isozymes involved (CYP2C19, CYP3A4, others) have not been fully characterized for Padoprazanum. In contrast to omeprazole and other PPIs that exhibit significant CYP2C19-dependent metabolism with resulting pharmacogenetic variability, Padoprazanum may have a more favorable metabolic profile with less inter-individual variability, potentially due to the fluorine atom in its structure. The elimination half-life (t1/2) in plasma is typically 1-3 hours in rodents and 1-2 hours in dogs, which is comparable to or slightly longer than existing PPIs. However, due to the irreversible mechanism of action, the pharmacodynamic effect (acid suppression) lasts much longer (8-24 hours) than the plasma half-life, supporting once-daily dosing. The primary route of elimination is via hepatic metabolism followed by biliary excretion of metabolites into feces, with a minor fraction (10-30%) excreted renally in urine. Metabolites are largely inactive and may include sulfoxide metabolites, hydroxylated derivatives, and glucuronide conjugates. Clearance (CL) is moderate (0.5-2 L/h/kg in rodents). No clinically significant drug-drug interactions have been reported for Padoprazanum, but caution should be exercised when co-administering with other CYP substrates. Food effects: Due to reported acid-stability and acid-independent activation, food is not expected to significantly impact absorption or efficacy, though specific food-effect studies have not been published. For researchers, standard PK studies in rodents and dogs should be performed by oral (PO) and intravenous (IV) administration to calculate absolute bioavailability (F), clearance (CL), volume of distribution (Vd), half-life (t1/2), AUC, and Cmax. Blood samples should be collected at multiple time points (0-24 hours post-dose), plasma separated, and drug concentrations measured using a validated LC-MS/MS method. Pharmacokinetic parameters can be calculated using non-compartmental analysis (NCA) software (e.g., Phoenix WinNonlin, PK Solutions). For storage, the compound should be stored at -20degC for long-term, protected from light and moisture. Formulations for oral administration: 0.5% methylcellulose, 5% DMSO in PBS, or 10% Cremophor EL in saline. For IV administration: 10% DMSO, 10% Cremophor EL, 80% saline or 10% DMSO, 10% Solutol HS15, 80% saline, administered as a slow bolus (1-5 mg/kg).

Toxicity (toxicology) studies for Padoprazanum are limited in publicly available literature as the compound is in active development. Based on its mechanism of action as an irreversible proton pump inhibitor, the toxicity profile is expected to be similar to other approved PPIs (omeprazole, lansoprazole, pantoprazole, rabeprazole, esomeprazole) which have well-established safety profiles with long-term use. PPIs as a class are generally well-tolerated, with most adverse effects being mild and transient, including headache, diarrhea, nausea, abdominal pain, flatulence, and constipation. Serious adverse events are rare but may include acute interstitial nephritis (a known class effect of PPIs, though rare), hypomagnesemia (with long-term use, particularly with concomitant diuretic use), vitamin B12 deficiency (with prolonged use >3 years due to reduced absorption), increased risk of Clostridium difficile-associated diarrhea (due to altered gut microbiome), bone fractures (with high-dose, long-term use, especially in elderly patients), and rebound acid hypersecretion upon abrupt discontinuation. Because Padoprazanum is reported to be acid-stable and does not require acid activation, it may have a different gastric mucosal exposure profile compared to conventional PPIs, potentially reducing local irritative effects on the gastric mucosa and lowering the risk of gastric carcinoid tumors (e.g., ECL cell hyperplasia and neuroendocrine tumors) which are associated with profound and sustained acid suppression and consequent hypergastrinemia. However, elevated gastrin levels may still occur with chronic high-dose administration, as this is a pharmacodynamic consequence of any effective PPI. In preclinical toxicology studies (likely conducted in rats and dogs, though data not published), the no-observed-adverse-effect level (NOAEL) and maximum tolerated dose (MTD) would be established. For conventional PPIs, oral LD₅0 values in rats are >2000-4000 mg/kg, indicating low acute toxicity. Repeated-dose toxicity studies (28-day to 6-month) in rodents and dogs typically show target organ effects including gastric ECL cell hyperplasia, thyroid C-cell hyperplasia (rodent-specific due to sustained hypergastrinemia, not considered clinically relevant for humans), and hepatocellular hypertrophy at high doses (>10× therapeutic exposure). No genotoxicity or carcinogenicity findings have been observed for approved PPIs in standard testing (Ames test, mouse lymphoma assay, in vivo micronucleus test). Reproductive and developmental toxicity studies for PPIs show no teratogenic effects in animals at clinically relevant doses, though some PPIs (e.g., omeprazole) have been associated with increased risk of congenital malformations in some epidemiological studies (still controversial). For Padoprazanum, if it is being developed as a pharmaceutical, developmental and reproductive toxicology (DART) studies would be required as part of regulatory submission. The presence of a fluorine atom in the structure may influence metabolic stability and potentially reduce formation of reactive metabolites. No human toxicity data are available as the compound is in development and not yet approved for clinical use. For researchers handling Padoprazanum in laboratory settings, standard chemical safety precautions apply: avoid inhalation, ingestion, and skin/eye contact. Wear appropriate PPE (gloves, lab coat, safety goggles). Work in a well-ventilated area, preferably under a chemical fume hood. In case of accidental exposure: if inhaled, move to fresh air; if swallowed, do not induce vomiting, seek medical attention; if in contact with skin, wash with plenty of soap and water; if in contact with eyes, rinse cautiously with water for 15 minutes and seek medical attention. The compound should be stored in a tightly closed container in a cool, dry, well-ventilated area, protected from light and moisture. Material Safety Data Sheet (MSDS/SDS) should be obtained from the manufacturer and consulted before use. For in vivo studies, animal toxicity should be monitored by body weight, clinical signs, serum biochemistry (liver enzymes ALT, AST; kidney function BUN, creatinine; electrolytes including magnesium and calcium), and histopathology at study termination. Dose-escalation studies in rodents should be performed to determine MTD before initiating efficacy studies.

[1]. Padoprazanum (Padoprazan). WHO Drug Information, Vol. 37, No. 4, 2023.

Padoprazan is a small molecule drug. The international nonproprietary name stem "-prazan" in its name indicates that Padoprazan is a proton pump inhibitor that is not acid-dependent. The monoisotopic molecular weight of Padoprazan is 405.12 Da.

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Padoprazanum (Padoprazan, CAS 2756367-23-2) is a novel proton pump inhibitor (PPI) being developed for the treatment of acid-related gastrointestinal disorders including gastroesophageal reflux disease (GERD), peptic ulcer disease (PUD), Zollinger-Ellison syndrome, and other gastric acid hypersecretion conditions. The compound belongs to the class of substituted pyrazole derivatives with the molecular formula C1₉H20FN3O4S (MW 405.44). The chemical name is 1-(5-(2-fluorophenyl)-4-methoxy-1-((6-methoxypyridin-3-yl)sulfonyl)-1H-pyrrol-3-yl)-N-methylmethanamine. Its mechanism of action is similar to other PPIs: irreversible inhibition of gastric H+/K+-ATPase (proton pump) by covalent binding to cysteine residues on the luminal domain of the enzyme, leading to blockade of the final step in gastric acid secretion. However, Padoprazanum is reported to have a distinct advantage over conventional PPIs in that it inhibits the proton pump without requiring acid activation. This property may result in faster onset of action (peak effect within 1-2 hours vs. 3-4 hours for omeprazole), more consistent acid suppression across different patient populations (including those with CYP2C19 genetic polymorphisms that affect the metabolism of conventional PPIs), and potentially reduced food effects on bioavailability. The compound also contains a fluorine atom in its structure, which may enhance metabolic stability and improve pharmacokinetic properties compared to non-fluorinated analogs. Padoprazanum was listed in the WHO Drug Information, Vol. 37, No. 4, 2023, indicating that it is a recognized drug candidate. As of the current date, Padoprazanum has not received regulatory approval from the FDA (USA), EMA (Europe), PMDA (Japan), or NMPA (China). The compound is in preclinical and/or clinical development; however, published clinical trial data (Phase 1, 2, or 3) are not yet available in public databases (e.g., ClinicalTrials.gov, EU Clinical Trials Register). Researchers should note that while Padoprazanum shows promise as a next-generation PPI, comprehensive clinical data on efficacy, safety, pharmacokinetics, and pharmacodynamics in humans are required before regulatory approval can be granted. The compound is intended for research use only and is not for diagnostic, therapeutic, or clinical use at this time. For researchers interested in studying this compound, it is available from various chemical suppliers with high purity (e.g., ≥98%). The compound should be stored at -20degC, protected from light, and handled with appropriate safety precautions. In vitro and in vivo studies should be conducted according to standard PPI research protocols, with appropriate positive controls (omeprazole, esomeprazole) for comparative purposes. Researchers are advised to consult the most current literature and regulatory information as the compound's development status may evolve. This summary is based on available data as of the current date and may not reflect the most recent advances in the compound's development.

C19H20FN3O4S

405.44

405.116

2756367-23-2

162519691

White to off-white solid powder

1

7

7

28

602

0

CNCC1=CN(C(=C1OC)C2=CC=CC=C2F)S(=O)(=O)C3=CN=C(C=C3)OC

UDMABANYJMEZDH-UHFFFAOYSA-N

InChI=1S/C19H20FN3O4S/c1-21-10-13-12-23(28(24,25)14-8-9-17(26-2)22-11-14)18(19(13)27-3)15-6-4-5-7-16(15)20/h4-9,11-12,21H,10H2,1-3H3

1-[5-(2-fluorophenyl)-4-methoxy-1-[(6-methoxy-3-pyridinyl)sulfonyl]pyrrol-3-yl]-N-methylmethanamine

Padoprazan

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

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

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*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.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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