Prognostic impact of concomitant pH-regulating drugs in patients with non-small cell lung cancer receiving epidermal growth factor receptor tyrosine kinase inhibitors: the Tokushukai REAl-world Data project 01-S1

PURPOSE

This study aimed to examine the prognostic impact of concomitant pH-regulating drug use in patients with epidermal growth factor receptor (EGFR)-mutation-positive non-small-cell lung cancer (NSCLC) receiving EGFR-tyrosine kinase inhibitors (TKIs).

METHODS

We conducted a nationwide retrospective cohort study and reviewed clinical data of consecutive patients with NSCLC treated with the first-line EGFR-TKIs in 46 hospitals between April 2010 and March 2020. Cox regression analyses were conducted to examine the differences in overall survival (OS) between patients treated with and without concomitant pH-regulating drugs, including potassium-competitive acid blockers (P-CABs), proton pump inhibitors (PPIs), and H2-receptor antagonists (H2RAs).

RESULTS

A total of 758 patients were included in the final dataset, of which 307 (40%) were administered concomitant pH-regulating drugs while receiving frontline EGFR-TKIs. After adjusting for basic patient characteristics, patients administered gefitinib, erlotinib, afatinib, and osimertinib with concomitant pH-regulating drugs had lower OS than those without concomitant pH-regulating drugs, with hazard ratios of 1.74 (with a 95% confidence interval of 1.34-2.27), 1.33 (0.80-2.22), 1.73 (0.89-3.36), and 5.04 (1.38-18.44), respectively. The 2-year OS rates of patients receiving gefitinib with or without concomitant pH-regulating drugs were 65.4 and 77.5%, those for erlotinib were 55.8 and 66.6%, and those for afatinib were 63.2 and 76.9%, respectively. The 1-year OS rates of patients receiving osimertinib with or without concomitant pH-regulating drugs were 88.1% and 96.9%, respectively.

CONCLUSION

In addition to the first-generation EGFR-TKIs, the second- and third-generation EGFR-TKIs also resulted in OS deterioration in patients with EGFR mutation-positive NSCLC when used concurrently with pH-regulating drugs.

Putting chirality to work: the strategy of chiral switches

Most of the new drugs reaching the market today are single enantiomers, rather than the racemic mixtures that dominated up to ten years ago. Many of the new single-enantiomer drugs were developed as such, but there are also important examples of new single-enantiomer drugs derived from 'chiral switches' of established racemates. Indeed, a well-timed chiral switch can offer enhanced therapy and further profitability as a 'line extension' of a major racemic drug with patents that are expiring.

Syntheses of 2-[(3,5-dimethyl-4-methoxypyridyl)alkyl]-benzothiazolidine derivatives as a potential gastric H+/K(+)-ATPase inhibitor

A series of 2-[(3,5-dimethyl-4-methoxypyridyl)alkyl]benzothiazolidine derivatives were synthesized and tested their inhibitory effects on gastric H+/K(+)-ATPase. Compound 4d exhibited potent in vitro inhibitory activity.

Review article: the continuing development of proton pump inhibitors with particular reference to pantoprazole

Inhibition of the gastric proton pump is gaining acceptance as the treatment of choice for severe gastrooesophageal reflux disease, and for treatment of duodenal and gastric ulceration. Three of these drugs are now available (omeprazole, lansoprazole and pantoprazole) and more are being developed. Proton pump inhibitors share the same core structure, but differ in terms of substituents on this core. The substitutions are able to modify some important chemical properties of the compounds. For example, pantoprazole is significantly more acid-stable than omeprazole or lansoprazole. E3810 is significantly less stable than the other compounds. We present an explantation for this finding that depends on the relative pK values for the pyridine and benzimidazole nitrogens, especially the former. Pantoprazole formulated in an enteric-coated tablet displays high bioavailability and linear pharmacokinetics whether on single or multiple dose regimens. Although all three proton pump inhibitors provide a similar chemical conversion to sulphenamides, which are highly reactive cysteine reagents, these reagents derivatize different cysteines in the extracytoplasmic or membrane domain of the pump and inhibit the pump at different rates. Whereas the differences in chemical reactivity can be explained by the solution chemistry of the compounds, selective derivatization of different cysteines on the protein argues for an involvement of pump structure in response to the presence of the proton pump inhibitor on its luminal surface. This suggests that the proton pump inhibitors, which were originally designed to take advantage of only the highly acidic space generated in the parietal cell by the production of the sulphenamide, are made even more selective by the protein they target. Pantoprazole is metabolized by a combination of phase I and phase II metabolism, and has also been shown to have a very low potential for drug interaction. Studies of acid secretion in man have shown this compound to be an effective and long lasting inhibitor of acid secretion. The pharmacodynamics explain the cumulative effect of repeated doses and maximal acid secretory capacity with a once daily dosage.

Pharmacokinetics of pantoprazole following single intravenous and oral administration to healthy male subjects

The plasma pharmacokinetics of pantoprazole have been investigated following single intravenous infusion and single oral administration at a dose of 40 mg to 12 healthy male subjects in a randomised cross-over study. Both treatments were generally well tolerated and no relevant compound-related adverse events were noted. The plasma pharmacokinetics of pantoprazole following intravenous infusion in this group of subjects were characterised by a total plasma clearance of 0.13 l.h-1 x kg-1 and apparent terminal elimination half-life 1.9 h. The apparent volume of distribution estimated at steady state (0.17 l.kg-1) was compatible with the localization of a major fraction of the compound in extracellular water. Following oral administration as an enteric-coated tablet formulation, a variable onset of absorption was followed by rapid attainment of maximum plasma concentrations of pantoprazole. Pantoprazole was well absorbed following oral administration; the absolute systemic bioavailability of the compound was estimated as 77% (95% CI, 67 to 89%).

Characterization of acid-base transport mechanisms in the kidney cell line RCCT-28A

RCCT-28A cells, a continuous cell line of rabbit cortical collecting tubule origin, have been found to exhibit apical peanut-lectin binding, basal band-3 immunostaining and a transepithelial electrical resistance of 246 +/- 37 omega cm2. For the studies reported, confluent monolayers of RCCT-28A cells were grown on permeable wells and incubated in a control solution or in alkaline solutions by lowering PCO2. Equivalent H+ fluxes (JH+) into the apical solution (nmol.min-1.cm2) were measured in the absence of drugs and in the presence of: amiloride (A, 10(-3) M), N-ethylmaleimide (NEM, 5 mM) and omeprazole (OM, 100 microM) in the apical solution. After preincubation in control solutions JH+ was 21 +/- 2 while A had no effect. Addition of NEM diminished JH+ to 12 +/- 2 (P < 0.005), and OM diminished JH+ to 2 +/- 2 (P < 0.001 vs. control). Monolayers incubated at low PCO2 had a basal JH+ of 11 +/- 5. No effect on JH+ could be demonstrated under these conditions by addition of NEM or OM. Removal of K+ from the apical solution diminished apical acidification by 60%. The inhibitor of H+,K(+)-ATPase Schering 28080 (SCH) was tested at different concentrations and an inhibitory effect was demonstrated (JH+ -2 +/- 1 vs. 18 +/- 1, SCH vs. control, respectively). Probenecid and bafilomycin-A also decreased apical acidification and an apical base-equivalent extrusion was apparent under the inhibitors effect. JH+ was abolished by removal of Cl- from the basolateral solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Pantoprazole: a novel H+/K(+)-ATPase inhibitor with an improved pH stability

The action of the H+/K(+)-ATPase inhibitors pantoprazole and omeprazole was compared in different in vitro test systems. In gastric membrane vesicles under conditions shown to result in acidification of the vesicle interior, pantoprazole and omeprazole inhibited H+/K(+)-ATPase activity with IC50 values of 6.8 and 2.4 microM, respectively. When intravesicular acidification was reduced by inclusion of imidazole (5 mM), a membrane permeable weak base, the inhibitory action of omeprazole was partially lost (IC50 30 microM) and that of pantoprazole almost completely lost. After incubation for 40 min with pumping membrane vesicles, a half-maximal reduction in intravesicular H+ concentration occurred at pantoprazole and omeprazole concentrations of 1.1 and 0.6 microM, respectively. Again, when the intravesicular H+ concentration was reduced by inclusion of imidazole (2.5 mM), pantoprazole (20 and 60 microM) did not reduce the remaining intravesicular proton concentration, whereas omeprazole (10 and 30 microM) did. Both drugs inhibited, with similar potency, papain activity at pH 3.0 and inactivated the enzyme in a similar time-dependent manner; at pH 5.0 omeprazole (IC50 17 microM) was more potent than pantoprazole (IC50 37 microM) and enzyme inhibition was faster than with pantoprazole. These results indicate that pantoprazole is a potent inhibitor of H+/K(+)-ATPase under highly acidic conditions and that it is more stable than omeprazole at a slightly acidic pH such as pH 5.0.

Inhibitions of acid secretion by E3810 and omeprazole, and their reversal by glutathione

A substituted benzimidazole ([4-(3-methoxypropoxy)-3-methylpyridine-2-yl]methylsulfinyl)- 1H-benzimidazole sodium salt (E3810), is a gastric proton pump (H+, K(+)-ATPase) inhibitor. E3810 and omeprazole inhibited acid accumulation dose dependently as measured with aminopyrine uptake in isolated rabbit gastric glands, their IC50 values being 0.16 and 0.36 microM, respectively. The addition of exogenous reduced glutathione (GSH) to the gland suspension reactivated dose dependently the acid secretion which had been inhibited by 2 microM E3810 or omeprazole as a function of the incubation time. Furthermore, GSH at 1 and 3 mM reversed the antisecretory effect of E3810 more quickly than it did that of omeprazole. The antisecretory effect of E3810 was slightly greater than that of omeprazole in histamine-stimulated fistula dogs in vivo. The duration of the antisecretory activity of E3810 at concentrations of 2 and 4 mg/kg was shorter than that of omeprazole at the same concentrations in pentagastrin-stimulated fistula dogs. The reversal of the antisecretory activity of the inhibitors in dogs is suggested to be due to the action of endogenous extracellular GSH, in addition to de novo synthesis of the proton pump, because bullfrog gastric mucosae were found in the present study to secrete GSH into the mucosal solution at the rate of about 0.25 nmol/min/g tissue.

By 1023/SK&F 96022: biochemistry of a novel (H+ + K+)-ATPase inhibitor

The mechanism by which the substituted benzimidazole sulphoxide BY 1023/SK&F 96022 inhibited the (H+ + K+)-ATPase, the enzyme responsible for hydrogen ion secretion in the stomach, was studied in a variety of in vitro preparations. In gastric preparations that were capable of active hydrogen ion transport with consequent lumenal acidification, BY 1023/SK&F 96022 inhibited with high potency and in a time-dependent manner consistent with the acid-induced conversion of the parent benzimidazole sulphoxide to a covalent inhibitor (cyclic sulphenamide). The following IC50 values were obtained for the inhibition of aminopyrine accumulation: intact gastric glands stimulated with 1 mM dibutyryl cAMP, 1.0 microM; permeabilized gastric glands stimulated with 5 mM ATP, 0.42 microM; intact gastric vesicles stimulated with 150 mM KCl, 9 microM valinomycin and 2 mM MgATP, 3.5 microM. In a preparation that could not generate pH gradients, lyophilized gastric vesicles at pH 7.4, BY 1023/SK&F 96022 inhibited K(+)-stimulated ATPase activity with relatively low potency, 70 microM, indicating its good chemical stability at neutral pH. As assessed by ATPase inhibition, this stability was three times greater than that of omeprazole. Inhibition by BY 1023/SK&F 96022 was not reversed by dilution in either permeabilized gastric glands or intact gastric vesicles. Inhibition could, however, be completely reversed by subsequent incubation with 20 mM beta-mercaptoethanol (intact gastric glands) or 100 mM dithiothreitol (intact gastric vesicles) suggesting a disulphide link between inhibitor and enzyme. The concentration of glutathione needed to protect against inhibition by BY 1023/SK&F 96022 was 10,000 times higher in intact, compared with lyophilized, gastric vesicles indicating an interaction with the lumenal (extra-cellular) face of the (H+ + K+)-ATPase. BY 1023/SK&F 96022 and omeprazole were also found to inhibit acidification in purified kidney lysosomes with IC50 values of 194 and 75 microM, respectively. Protection by 10 microM glutathione suggested that this did not result from intralysosomal activation of these inhibitors. Thus, BY 1023/SK&F 96022 has the combined properties of good chemical stability at neutral pH and effective conversion to the cyclic sulphenamide at acidic pH. In this way the activation to the cyclic sulphenamide may be optimally restricted to the parietal cell canaliculus.

The potency of substituted benzimidazoles such as E3810, omeprazole, Ro 18-5364 to inhibit gastric H+, K(+)-ATPase is correlatedwith the rate of acid-activation of the inhibitor

The half maximal inhibitory concentrations (IC50) of substituted benzimidazoles for the H+, K(+)-ATPase in hog gastric vesicles were measured by using the pyruvate kinase-lactate dehydrogenase-linked system in which hydrolysis of ATP was coupled with the oxidation of NADH. The vesicles were incubated in a solution containing a high concentration of KCl, valinomycin and Mg-ATP, and the intravesicular medium was acidified. The inhibitor was activated in the acidic medium and reacted with SH groups on the luminal (intravesicular) side of the ATPase. The active compound formed in the extravesicular medium (pH 6.11) was quenched by GSH. Under these conditions, IC50 of new compound E3810, 2[(4-(3-methoxypropoxy)-3-methylpyridine-2-yl)methyl-sulfinyl]-1H- benzimidazole sodium salt, was 0.072 microM and that of omeprazole was 0.47 microM at 25 degrees. On the other hand, the rates of formation of active compounds, tetracyclic sulfenamide derivatives, from original substituted benzimidazoles in 0.1 N HCl (k) were determined by measuring optical density at the characteristic wavelengths of the active compounds. There was a good correlation between IC50 and k for various substituted benzimidazoles including E3810, methoxy derivative of E3810, omeprazole, Ro 18-5364, H compound, picoprazole and timoprazole. This fact suggest that the rate of the formation of the acid-activated compound is a main factor determining the potency of the inhibitor.

Acid activation of omeprazole in isolated gastric vesicles, oxyntic cells, and gastric glands

Omeprazole, a potent inhibitor of gastric hydrogen ion transporting, potassium-stimulated adenosine triphosphatase, was found to be transformed into an SH-reactive strong fluorescent molecule (excitation and emission wavelengths of 370 and 560 nm, respectively) in an acidic medium. The addition of glutathione- or protein-containing sulfhydryl groups such as pepsin to the medium decreased the fluorescence. Also, the increase in the pH of the medium decreased the fluorescence. The fluorescent molecule was identified to be an acid-activated planar cyclic sulfenamide derivative of omeprazole. The transformation was studied in H+-preaccumulated hog gastric vesicles, which contain the hydrogen ion transporting, potassium-stimulated adenosine triphosphatase. The addition of omeprazole to the vesicle suspension induced a rapid increase in the fluorescence intensity, indicating that omeprazole was activated in the intravesicular space. Then, the intensity biphasically decreased with time. The slower small decrease was due to the reaction of the sulfenamide with sulfhydryl group(s) located on the acid secretory side of the hydrogen ion transporting, potassium-stimulated adenosine triphosphatase. Omeprazole was also activated in the acidic lumina of isolated rabbit gastric glands that were stimulated with histamine. Furthermore, direct evidence was obtained from the imaging of the fluorescence that omeprazole was activated in the acidic compartments of the isolated Xenopus oxyntic cell.

Omeprazole, SCH 28080 and doxepin differ in their characteristics to inhibit H+/K+-ATPase driven proton accumulation by parietal cell membrane vesicles

The effects of omeprazole, SCH 28080 and doxepin were studied on H+/K+-ATPase mediated H+ accumulation in parietal cell membrane vesicles. Omeprazole had no effect on the initial rate of H+ accumulation and the initial steady state concentration of H+; an inhibition was found after the vesicles were acidified. This inhibition was counteracted by the SH reducing agent dithioerythritol. SCH 28080 inhibited the initial rate of H+ accumulation and the steady state H+ concentration. The inhibitory effect of SCH 28080 was counteracted by KCl. Doxepin (3-100 microM) reduced the initial steady state H+ concentration. Doxepin concentrations lower than 0.5 microM had no such effect but dissipated the proton gradient after the vesicles were fully acidified. This doxepin effect was partially counteracted by KCl and was also obtained in vesicles in which the pump reaction was stopped by EDTA. These data show that (i) omeprazole is an acid-activated compound which interferes with SH groups of the H+/K+-ATPase localized inside the vesicles; (ii) SCH 28080 interferes with the K+ site of the H+/K+-ATPase; and (iii) doxepin interacts by a K+ antagonistic activity at the H+/K+-ATPase site and in addition by intravesicular neutralization and/or a protonophoric mechanism with the process of H+ formation.

Studies on the mechanism of action of the omeprazole-derived cyclic sulphenamide

The inhibitory effects of omeprazole and omeprazole-derived metabolites were studied on Escherichia coli glutaminase activity at pH 2.5 which might represent the conditions present at the target enzyme (K+/H+-ATPase) in the secretory membrane of the intact parietal cell. Omeprazole and the omeprazole-derived cyclic sulphenamide inhibited glutaminase at pH 2.5 with identical potency (IC50 36 microM). The substrate, glutamine as well as the mercaptane, dithiothreitol, protect the enzyme. Furthermore, dithioerythritol was found to reverse inhibition. This indicates that an SH-group localized in the substrate binding center of glutaminase is most likely involved in the reaction leading to enzyme inhibition. Glutaminase inhibition by both compounds was less pronounced at pH 5.0. Omeprazole radical, the metabolite generated from the cyclic sulphenamide at more neutral pH values, failed to affect the enzyme. These findings were in contrast with the properties of the omeprazole-derived cyclic sulphenamide and radical at the K+/H+-ATPase preparation. This enzyme was inhibited by both compounds at pH 7.5 with a high potency, and reversal experiments with dithiothreitol demonstrate that these agents interfere with SH-groups of the K+/H+-ATPase. From these data it is suggested that the cyclic sulphenamide and the radical interfere by different reaction pathways with enzymatic SH-groups.

Effect of omeprazole on eicosanoid formation in and release from guinea-pig gastric mucosal cells

Guinea-pig gastric mucosal cells isolated by collagenase and pronase digestion were used to study the release of prostanoids prostaglandin I2 (PGI2; measured as 6-keto PGF1 alpha), PGE2, PGF2 alpha and thromboxane A2 (TXA2; measured as TXB2). Lysophosphatide acyltransferase (LAT) and phospholipase A2 (PLA2) were measured in the microsomal fraction of isolated but not separated gastric cells and isolated and enriched parietal and mucous cells. In all cell preparations PLA2 activity was approximately 5 times higher than that of LAT. Acid-activated omeprazole inhibited LAT in a concentration-dependent manner with similar IC50 values in gastric, parietal and mucous cells. It had no effect on PLA2. Gastric cells constantly produced PGI2, PGE2, PGF2 alpha and TXA2. The main prostaglandins released were PGI2 and PGE2. PGF2 alpha and TXA2 were released in smaller quantities. Omeprazole dissolved in polyethylene glycol 400 (PEG) pH 2 inhibited spontaneous PGI2 release in a concentration-dependent manner with an IC50 of 14.3 +/- 4.8 microM. Only concentrations as high as 100 microM produced a significant reduction in PGE2 release by 60%. No significant changes could be detected in the spontaneous release of PGF2 alpha and TXA2. Omeprazole dissolved in PEG pH 7 had no effect on PGI2 release except at 100 microM which led to an insignificant decrease by 40%. These data suggest that omeprazole beyond its inhibitory effect on parietal cell K+/H+-ATPase also affects gastric mucosal prostanoid formation and release. The inhibitory effect on PGI2 does not support the view that omeprazole protects the gastric mucosa by increasing prostanoid formation.

The specificity of omeprazole as an (H+ + K+)-ATPase inhibitor depends upon the means of its activation

Omeprazole (OME) is a novel acid secretion inhibitor, believed to act directly on the gastric proton pump, the (H+ + K+)-ATPase. Inhibition of ATPase activity is associated with an incorporation of [14C]OME into gastric vesicles containing the (H+ + K+)-ATPase, and both processes are greatly enhanced if the OME is exposed to acidic pH. This, and other evidence, suggests that the acidic environment of the (H+ + K+)-ATPase generates from OME a reactive intermediate which covalently inhibits the pump. We have compared the means by which the OME was acid-activated with the specificity of inhibition (amount of incorporation of omeprazole required to produce 100% inhibition of K+-stimulated ATPase activity). The stoichiometry of incorporation has been related to the number of detectable catalytic phosphorylation sites in each preparation (an index of the number of functional pumps). In lyophilised gastric vesicles, where the membrane barriers separating the cytoplasmic and luminal faces of the enzyme are substantially destroyed, incubation with OME at pH 6.1 produced a progressive inhibition and incorporation over 120 min. Complete inhibition of K+-ATPase required 13 +/- 3 (SEM; N = 4) moles of OME incorporation per phosphorylation site. In intact gastric vesicles, under conditions shown independently to result in proton pumping and the acidification of the vesicle interior (150 mM KCl, 9 microM valinomycin, 2 mM Mg-ATP pH 7.0), inhibition and incorporation occurred more rapidly (15 min). Complete inhibition of K+-ATPase required only 1.8 +/- 0.15 (SEM; N = 3) moles of OME per phosphorylation site.(ABSTRACT TRUNCATED AT 250 WORDS)