The metabolic chiral inversion and dispositional enantioselectivity of the 2-arylpropionic acids and their biological consequences

Bioequivalence risk assessment of oral formulations containing racemic ibuprofen through a chiral physiologically based pharmacokinetic model of ibuprofen enantiomers

The characterization of the time course of ibuprofen enantiomers can be useful in the selection of the most sensitive analyte in bioequivalence studies. Physiologically based pharmacokinetic (PBPK) modelling and simulation represents the most efficient methodology to virtually assess bioequivalence outcomes. In this work, we aim to develop and verify a PBPK model for ibuprofen enantiomers administered as a racemic mixture with different immediate release dosage forms to anticipate bioequivalence outcomes based on different particle size distributions. A PBPK model incorporating stereoselectivity and non-linearity in plasma protein binding and metabolism as well as R-to-S unidirectional inversion has been developed in Simcyp®. A dataset composed of 11 Phase I clinical trials with 54 scenarios (27 per enantiomer) and 14,452 observations (7129 for R-ibuprofen and 7323 for S-ibuprofen) was used. Prediction errors for AUC0-t and Cmax for both enantiomers fell within the 0.8-1.25 range in 50/54 (93 %) and 42/54 (78 %) of scenarios, respectively. Outstanding model performance, with 10/10 (100 %) of Cmax and 9/10 (90 %) of AUC0-t within the 0.9-1.1 range, was demonstrated for oral suspensions, which strongly supported its use for bioequivalence risk assessment. The deterministic bioequivalence risk assessment has revealed R-ibuprofen as the most sensitive analyte to detect differences in particle size distribution for oral suspensions containing 400 mg of racemic ibuprofen, suggesting that achiral bioanalytical methods would increase type II error and declare non-bioequivalence for formulations that are bioequivalent for the eutomer.

Variation of Activation Volume as an Indicator of the Difference in Clusterization Phenomenon Induced by H-Bonding and F-Π Stacking Interactions in Enantiomers and a Racemate of Flurbiprofen

In this paper, X-ray diffraction (XRD), differential scanning calorimetry (DSC), broadband dielectric (BDS), and Fourier transform infrared (FTIR) spectroscopy supported by molecular dynamics (MD) simulations and quantum chemical computations were applied to investigate the structural and thermal properties, molecular dynamics, and H-bonding pattern of R-, S-, and RS-flurbiprofen (FLP). Experimental data indicated various spatial molecular arrangements in crystalline forms of examined systems, which seemed to disappear in the liquid state. Surprisingly, deeper analysis of high-pressure dielectric data revealed unexpected variation in the activation volume of pure enantiomers and a racemate. MD simulations showed that it is an effect of the clusterization phenomenon and a higher population of small associates in the former samples. Moreover, theoretical consideration exposed the particular role of unspecific F-Π interactions as a driving force underlying local molecular arrangements of molecules in the liquid and the crystal lattice of R-, S-, and RS-FLP.

Comparative Pharmacokinetics and Safety Studies of Dexibuprofen Injection and a Branded Product Ibuprofen Injection in Healthy Chinese Volunteers

Ibuprofen, a nonsteroidal anti-inflammatory drug, is considered a safe and effective analgesic for treating different types of pain and joint disorders. Dexibuprofen, S-(+)-ibuprofen, is the single pharmacologically active enantiomer of ibuprofen. It is more potent than the racemic formulation of ibuprofen in terms of analgesic and anti-inflammatory properties and causes less acute gastric damage. For the first time, in the present single-dose, randomized, open-label, 2-period crossover study, the safety and pharmacokinetic (PK) characteristics of a single-dose dexibuprofen injection (0.2 g) were evaluated in healthy Chinese subjects and compared with the PK characteristics of a 0.2-g ibuprofen injection. Five consecutive men and women were randomly administered a single dose of the 0.2-g ibuprofen or 0.2-g dexibuprofen injection after fasting in every period during the 5-day interval. Then, plasma samples were collected for liquid chromatography-tandem mass spectrometric analysis. WinNonlin software was used for calculating the PK parameters. The geometric mean ratios of the 0.2-g dexibuprofen injection/ibuprofen injection for maximal plasma concentration, area under the plasma concentration-time curve (AUC) from time 0 to the last quantifiable time point, and AUC from time 0 to infinity were 184.6%, 136.9%, and 134.4%, respectively. The dexibuprofen plasma exposure of the 0.15-g dexibuprofen injection was comparable to that of the 0.2-g ibuprofen injection, calculated using AUC from time 0 to infinity.

The Quest for Secondary Pharmaceuticals: Drug Repurposing/Chiral-Switches Combination Strategy

Drug repurposing toward new medical uses and chiral switches are elements of secondary pharmaceuticals. The drug repurposing and chiral-switches strategies have mostly been applied independently in drug discovery. Drug repurposing has peaked in the search for therapeutic treatments of the Coronavirus Disease 2019 pandemic, whereas chiral switches have been overlooked. The current Perspective introduces the drug repurposing/chiral-switches combination strategy, overviewing representative cases of chiral drugs that have undergone this combination: ketamine, flurbiprofen, fenfluramine, and milnacipran. The deuterium-enabled chiral switches of racemic thalidomide analogs, a variation of the repurposing/chiral-switch combination strategy, is also included. Patenting and regulatory-exclusivity considerations of the combination strategy in the discovery of new medical uses are considered. The proposed combination creates a new synergy of its two elements, overcoming arguments against chiral switches, with better prospects for validation of patents and regulatory exclusivities. The combination strategy may be applied to chiral switches to paired enantiomers. Repurposing/chiral-switch drugs may be 'obvious-to-try'; however, their inventions may be unexpected and their patents nonobvious. Patenting repurposing/chiral-switch combination drugs is not 'evergreening', 'product hopping', and 'me-too'. The expected benefits and opportunities of the combined repurposing/chiral-switch strategy vis-à-vis its two elements are superior pharmacological properties, overcoming arguments against patent validities, challenges of chiral-switch patents, reduced expenses, shortened approval procedures, and higher expectations of regulatory exclusivities.

Chiral Inversion of 2-Arylpropionic Acid Enantiomers under Anaerobic Conditions

This work examined the chiral inversion of 2-arylpropionic acids (2-APAs) under anaerobic conditions and the associated microbial community. The anaerobic condition was simulated by two identical anaerobic digesters. Each digester was fed with the substrate containing 11 either pure (R)- or pure (S)-2-APA enantiomers. Chiral inversion was evidenced by the concentration increase of the other enantiomer in the digestate and the changes in the enantiomeric fraction between the two enantiomers. Both digesters showed similar and poor removal of 2-APAs (≤30%, except for naproxen) and diverse chiral inversion behaviors under anaerobic conditions. Four compounds exhibited (S → R) unidirectional inversion [flurbiprofen, ketoprofen, naproxen, and 2-(4-tert-butylphenyl)propionic acid], and the remaining seven compounds showed bidirectional inversion. Several aerobic and facultative anaerobic bacterial genera (Candidatus Microthrix, Rhodococcus, Mycobacterium, Gordonia, and Sphingobium) were identified in both digesters and predicted to harbor the 2-arylpropionyl-CoA epimerase (enzyme involved in chiral inversion) encoding gene. These genera presented at low abundances, <0.5% in the digester dosed with (R)-2-APAs and <0.2% in the digester dosed with (S)-2-APAs. The low abundances of these genera explain the limited extent of chiral inversion observed in this study.

Design and synthesis of five-membered heterocyclic derivatives of istradefylline with comparable pharmacological activity

Parkinson's disease (PD) is a common degenerative disease of the central nervous system among the elderly. Istradefylline, an FDA-approved adenosine A_2A receptor antagonist (anti-PD drug), has good efficacy. However, it has been reported that the double bond of istradefylline is easily converted into cis-configuration when exposed to an indoor environment or direct light in a dilute solution. In order to find more stable adenosine A_2A receptor antagonists with similar pharmacological efficacy to istradefylline, the compounds series I-1 (12 compounds) was designed by maintaining the xanthine skeleton of istradefylline unchanged and replacing the trans-double bond with thiazole or benzothiazole and other biologically active heterocyclic compounds. These compounds were synthesized via multi-step experiment and successfully confirmed through different characterization techniques for their ability to inhibit cAMP formation in A_2A AR overexpressing cells. The thiazole derivative of istradefylline (Compound I-1-11, I-1-12) exhibited significant activity (IC₅₀  = 16.74 ± 4.11 μM, 10.36 ± 3.09 μM), as compared to istradefylline (IC₅₀  = 5.05 ± 1.32 μM). In addition, the molecular docking of benzothiazole derivatives I-1-11 and thiazole derivatives I-1-12 with higher inhibition rate were carried out and compared with istradefylline. The molecular docking results showed that I-1-11 and I-1-12 anchored in the same site as that of XAC (3REY) with predicted affinity binding energy -6.63 kcal/mol and - 6.75 kcal/mol, respectively. Validation through dynamics simulation also showed stable interactions, with fluctuations <3 Å and MM/GBSA energy <-20 kcal/mol. Hence, this study could provide a basis for the rational design of adenosine A_2A receptor antagonists with better potency.

Chiral inversion of 2-arylpropionoic acid (2-APA) enantiomers during simulated biological wastewater treatment

This study examined the removal and enantio‑specific fate of a suite of eleven chiral 2-arylpropionic acids (2-APAs) during biological wastewater treatment simulated in a laboratory-scale membrane bioreactor (MBR). Using pure (R)- and (S)- enantiomers in the MBR influent, chiral inversion was determined through the increase in the concentration of the non-dominant enantiomer and changes in the enantiomeric fraction (EF) between the two enantiomers during the treatment process. Effective (>90%) and similar removal rates between (R)- and (S)- enantiomers were confirmed for eight 2-APAs. In this study, 2-APAs exhibited diverse and distinctive chiral inversion behaviours: two 2-APAs showed (R→S) unidirectional inversion, three 2-APAs showed (S→R) unidirectional inversion, and six 2-APAs showed bidirectional inversion. This is the first study to report chiral inversion behaviours of a comprehensive suite of 2-APAs with a variety of functional groups substituted onto the aryl ring. A decrease in effluent EF over time was observed for two 2-APAs. This study shows that chiral inversion of 2-APAs varies significantly from compound to compound, despite the high similarity in their chemical structures.

Detailed Molecular Mechanisms Involved in Drug-Induced Non-Alcoholic Fatty Liver Disease and Non-Alcoholic Steatohepatitis: An Update

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are some of the biggest public health challenges due to their spread and increasing incidence around the world. NAFLD is characterized by intrahepatic lipid deposition, accompanied by dyslipidemia, hypertension, and insulin resistance, leading to more serious complications. Among the various causes, drug administration for the treatment of numerous kinds of diseases, such as antiarrhythmic and antihypertensive drugs, promotes the onset and progression of steatosis, causing drug-induced hepatic steatosis (DIHS). Here, we reviewed in detail the major classes of drugs that cause DIHS and the specific molecular mechanisms involved in these processes. Eight classes of drugs, among the most used for the treatment of common pathologies, were considered. The most diffused mechanism whereby drugs can induce NAFLD/NASH is interfering with mitochondrial activity, inhibiting fatty acid oxidation, but other pathways involved in lipid homeostasis are also affected. PubMed research was performed to obtain significant papers published up to November 2021. The key words included the class of drugs, or the specific compound, combined with steatosis, nonalcoholic steatohepatitis, fibrosis, fatty liver and hepatic lipid deposition. Additional information was found in the citations listed in other papers, when they were not displayed in the original search.

Enantioselective separation of nonsteroidal anti-inflammatory drugs with amylose tris(3-chloro-5-methylphenylcarbamate) stationary phase in HPLC with a focus on enantiomeric quality control in six pharmaceutical formulations containing racemic mixtures or single stereoisomers

In the present study, an accurate, rapid, and simple chiral HPLC-UV method with amylose tris(3-chloro-5-methylphenylcarbamate) as stationary phase was developed and applied for enantiomeric determination of six nonsteroidal anti-inflammatory drugs (NSAIDs) in the commercial pharmaceutical formulations, including (R,S)-ibuprofen, S-ibuprofen, (R,S)-ketoprofen, S-ketoprofen, S-naproxen, and (R,S)-loxoprofen sodium. Experiments on the influence of mobile phase composition, proportion of organic modifier, percentage of acid additives, and column temperature on enantioseparation were conducted to obtain the best separation condition. It was indicated that one mobile phase simply composed of acetonitrile-water (0.1% formic acid, v/v) at the proportion of 50:50 (v/v) with a flow rate of 0.6 ml/min at 22°C could simultaneously provide the excellent enantiomeric resolutions for all selected NSAIDs, which made the enantioseparation process more applicable and operable. The newly developed method was then applied for determination of NSAID enantiomers in pharmaceutical formulations containing racemic mixtures or single stereoisomers. Calibration curve of each enantiomer at the concentration of 5.0-100 ug/ml showed good linearity with the correlation coefficient above 0.9996. Satisfactory recovery (96.54-101.54%), good intra-day precision (RSD 0.52-1.46%), and inter-day precision (RSD 0.13-1.09%) were also obtained. The newly developed method was then applied for determination of NSAID enantiomers in pharmaceutical formulations containing racemic mixtures or single stereoisomers. Quantitative results of the commercial capsules and tablets demonstrated that the difference between the declared and measured values did not exceed 1.52%.

Continuum Crystallization Model Derived from Pharmaceutical Crystallization Mechanisms

The crystallization mechanisms of organic molecules in solution are not well-understood. The mechanistic scenarios where crystalline order evolves directly from the molecularly dissolved state ("classical") and from initially formed amorphous intermediates ("nonclassical") are suggested and debated. Here, we studied crystallization mechanisms of two widely used analgesics, ibuprofen (IbuH) and etoricoxib (ETO), using direct cryogenic transmission electron microscopy (cryo-TEM) imaging. In the IbuH case, parallel crystallization pathways involved diverse phases of high and low density, in which the instantaneous formation of final crystalline order was observed. ETO crystallization started from well-defined round-shaped amorphous intermediates that gradually evolved into crystals. This mechanistic diversity is rationalized by introducing a continuum crystallization paradigm: order evolution depends on ordering in the initially formed intermediates and efficiency of molecular rearrangements within them, and there is a continuum of states related to the initial order and rearrangement rates. This model provides a unified view of crystallization mechanisms, encompassing classical and nonclassical pictures.

The Comparison of Plasma and Cerebrospinal Fluid R(-)- and S(+)-Flurbiprofen Concentration After Intravenous Injection of Flurbiprofen Axetil in Human Subjects

Background: Flurbiprofen axetil is a prodrug that releases the active substance through enzymatic removal of the ester moiety. It is formulated through encapsulation in a lipid microsphere carrier, and widely used to treat perioperative pain. Here, we studied the distribution of R (-)- and S (+)-flurbiprofen in human plasma and cerebrospinal fluid (CSF) after intravenous injection of flurbiprofen axetil. Methods: A total of 70 adult patients undergoing elective lower limb surgery under spinal anesthesia were given a single intravenous injection of 100-mg flurbiprofen axetil. The patients were randomly assigned to 10 groups for plasma and CSF sampling at 10 time points (5-50 min) after subarachnoid puncture and before actual spinal anesthesia. R (-)- and S (+)-flurbiprofen and CSF/plasma ratio were determined by liquid chromatography-tandem mass spectrometry. Results: R (-)-flurbiprofen concentration ranged from 2.01 to 10.9 μg/mL in plasma and 1.46-34.4 ng/mL in CSF. S (+)-flurbiprofen concentration ranged from 1.18 to 10.8 μg/mL in plasma and from 2.53 to 47 ng/mL in CSF. In comparison to S (+)-flurbiprofen, R (-)-flurbiprofen concentration was significantly higher in plasma at all time points (p < 0.05) except at 30 or 40 min, and lower in CSF at all time points (p < 0.05) except at 10, 15 and 40 min. Analysis after correcting drug concentration for body mass index also revealed higher plasma and lower CSF R (-)-flurbiprofen concentration. In comparison to S (+)-flurbiprofen, AUC_0-50 for R (-)-flurbiprofen was larger in plasma and smaller in CSF (p < 0.05 for both), and accordingly smaller CSF/plasma AUC_0-50 ratio (p < 0.05). There was a positive correlation between R (-)-flurbiprofen concentration and S (+)-flurbiprofen concentration in plasma (r = 0.725, p < 0.001) as well as in CSF (r = 0.718, p < 0.001), and a negative correlation between plasma and CSF concentration of S (+)-flurbiprofen (r = -0.250, p = 0.037), but not R (-)-flurbiprofen. Conclusion: Distribution of R (-)- and S (+)-flurbiprofen in plasma and CSF differed significantly. Penetration of R (-)-flurbiprofen into the CNS was lower than S (+)-flurbiprofen.

Evaluating the enantiospecific differences of non-steroidal anti-inflammatory drugs (NSAIDs) using an ecotoxicity bioassay test battery

Wastewater treatment plants are a major pathway for pharmaceuticals to the aquatic environment. Many pharmaceuticals, including non-steroidal anti-inflammatory drugs (NSAIDs), are chiral chemicals and the biological activity of their enantiomers can differ. Few studies have assessed the effects of different NSAID enantiomers on non-target organisms. However, this information is important for environmental risk assessment to ensure that the effects of more potent enantiomers are not overlooked. In the current study, enantiomers of naproxen, ibuprofen, ketoprofen and flurbiprofen were evaluated in bioassays with bacteria, algae and fish cells. All enantiomers induced bacterial toxicity, with (R)-naproxen more toxic than (S)-naproxen (EC₅₀ 0.75 vs 0.93 mg/L) and (S)-flurbiprofen more toxic than (R)-flurbiprofen (EC₅₀ 1.22 vs 2.13 mg/L). Both (R)-flurbiprofen and (S)-flurbiprofen induced photosystem II inhibition in green algae, with (R)-flurbiprofen having a greater effect in the assay after 24 h (EC₁₀ 5.47 vs 9.07 mg/L). Only the (R)-enantiomers of flurbiprofen and ketoprofen induced ethoxyresorufin-O-deethylase (EROD) activity in fish cells, while (S)-naproxen was 2.5 times more active than (R)-naproxen in the EROD assay. While enantiospecific differences were observed for all assays, the difference was less than an order of magnitude. This indicates that the risk of overlooking the effect of more potent NSAID enantiomers is minor for the studied test systems and supports the use of racemic (or single enantiomer) effect data for environmental risk assessment. However, further investigation of the (R)-enantiomer of commonly used NSAID ketoprofen is recommended as it was at least six times more potent in the EROD assay than the inactive (S)-ketoprofen.

Liquid Metastable Precursors of Ibuprofen as Aqueous Nucleation Intermediates

The nucleation mechanism of crystals of small organic molecules, postulated based on computer simulations, still lacks experimental evidence. In this study we designed an experimental approach to monitor the early stages of the crystallization of ibuprofen as a model system for small organic molecules. Ibuprofen undergoes liquid–liquid phase separation prior to nucleation. The binodal and spinodal limits of the corresponding liquid–liquid miscibility gap were analyzed and confirmed. An increase in viscosity sustains the kinetic stability of the dense liquid intermediate. Since the distances between ibuprofen molecules within the dense liquid phase are similar to those in the crystal forms, this dense liquid phase is identified as a precursor phase in the nucleation of ibuprofen, in which densification is followed by generation of structural order. This discovery may make it possible to enrich poorly soluble pharmaceuticals beyond classical solubility limitations in aqueous environments.

The efficacy of dexketoprofen for migraine attack: A meta-analysis of randomized controlled studies

BACKGROUND

The efficacy of dexketoprofen for migraine attack remains controversial. We conduct a systematic review and meta-analysis to explore the influence of dexketoprofen supplementation versus placebo on pain control in migraine attack patients.

METHODS

We search PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases through March 2019 for randomized controlled trials (RCTs) assessing the effect of dexketoprofen supplementation versus placebo on pain control for migraine attack patients. This meta-analysis is performed using the random-effect model.

RESULTS

Five RCTs involving 794 patients are included in the meta-analysis. Overall, compared with control group for migraine attack, dexketoprofen supplementation is associated with substantially increased pain free at 2 hours (RR = 1.90; 95% CI = 1.43-2.53; P < .0001), pain free at 48 hours (RR = 1.63; 95% CI = 1.07-2.49; P = .02), good or excellent treatment (RR = 1.48; 95% CI = 1.24-1.78; P < .0001) and pain relief at 2 hours (RR = 1.80; 95% CI = 1.17-2.77; P = .007), as well as reduced need for rescue drug (RR = 0.64; 95% CI = 0.43-0.94; P = .02), with no significant increase in adverse events (RR = 1.51; 95% CI = 0.87-2.62; P = .14).

CONCLUSION

Dexketoprofen supplementation benefits to improve pain control at 48 hours and reduce the need for rescue drug in migraine attack patients.

Investigation of intestinal elimination and biliary excretion of ibuprofen in hyperglycemic rats

An in vivo intestinal perfusion model was used to investigate how experimental hyperglycemia affects intestinal elimination and biliary excretion in the rat. Experimental diabetes was induced by administration of streptozotocin (65 mg/kg, i.v.). The intestinal perfusion medium contained 250 μM (±)-ibuprofen. An isocratic high-performance liquid chromatography method with UV-visible detection was developed to quantitate ibuprofen in the intestinal perfusate, while a gradient method was applied to quantitate ibuprofen and ibuprofen-β-d-glucuronide in the bile. The limit of quantitation of ibuprofen was found to be 0.51 μM in the perfusate of the small intestine. In the bile, the limit of quantitation of ibuprofen and ibuprofen-β-d-glucuronide was 4.42 and 10.3 μM, respectively. Unconjugated ibuprofen and ibuprofen-β-d-glucuronide were detected in the bile; however, no β-d-glucuronide of ibuprofen could be detected in the intestinal perfusate. The results indicate that experimental diabetes can cause a decrease in the disappearance of ibuprofen from the small intestine. Excretion of both ibuprofen and ibuprofen-β-d-glucuronide decreased to the bile in experimental diabetes. The results can be explained by the results of molecular biological studies indicating streptozotocin-initiated alterations in the intestinal and hepatic transport processes.

Stereoselective Pharmacokinetics and Chiral Inversion of Ibuprofen in Adjuvant-induced Arthritic Rats

2-Arylpropionic acid (2-APA) nonsteroidal anti-inflammatory drugs are commonly used in racemic mixtures (rac) for clinical use. 2-APA undergoes unidirectional chiral inversion of the in vivo inactive R-enantiomer to the active S-enantiomer. Inflammation causes the reduction of metabolic activities of drug-metabolizing enzymes such as cytochrome P450 (P450) and UDP-glucuronosyltransferase. However, it is unclear whether inflammation affects the stereoselective pharmacokinetics and chiral inversion of 2-APA such as ibuprofen (IB). We examined the effects of inflammation on the pharmacokinetics of R-IB and S-IB after intravenous administration of rac-IB, R-IB, and S-IB to adjuvant-induced arthritic (AA) rats, an animal model of inflammation. The plasma protein binding of rac-IB, glucuronidation activities for R-IB and S-IB, and P450 contents of liver microsomes in AA rats were determined. Total clearance (CLtot) of IB significantly increased in AA rats, although the glucuronidation activities for IB, and P450 contents of liver microsomes decreased in AA rats. We presumed that the increased CLtot of IB in AA rats was caused by the elevated plasma unbound fraction of IB due to decreased plasma albumin levels in AA rats. Notably, CLtot of R-IB but not S-IB significantly increased in AA rats after intravenous administration of rac-IB. These results suggested that AA could affect drug efficacies after stereoselective changes in the pharmacokinetics of R-IB and S-IB.

Comparative efficacy of esomeprazole and omeprazole: Racemate to single enantiomer switch

Background

Both omeprazole and its S enantiomer (esomeprazole) have been available and used to treat  symptoms of gastroesophageal reflux disease (GERD) and conditions associated with excessive stomach acid secretion for more than a decade. Controversy exists over improved efficacy of S enantiomer (esomeprazole) over parent racemate (omeprazole). However, a comparison of the clinical outcomes of these products may reveal the rationale for switching from the racemate to single enantiomer. Since enantiomers of omeprazole are equipotent, we compared the outcomes of equal doses of each product to see if both actually differ in their efficacy’s or the reported superiority of S enantiomer is just a dose effect.

Methods

A web search was carried out for randomized controlled trials with head-to-head comparisons of omeprazole and S-omeprazole. The data were abstracted and after calculating theodd ratios (OR) for the outcomes reported in each study, the combined overall odd ratios (OR’) were estimated. The random effect inverse variance method with omeprazole as the reference (OR” = 1) was used.

Results

Out of 1171 studies, 14 were deemed eligible. There was no significant difference in the therapeutic success between omeprazole and S-omeprazole as a part of triple therapy for the treatment of H. pylori in both intention-to-treat (OR’, 1.06; CI, 0.83, 1.36; p = 0.63) as well as per-protocol analysis (OR’, 1.07; CI, 0.84, 1.36; p = 0.57). For the treatment of gastro-oesophageal reflux disease, S-omeprazole was significantly but marginally superior to the racemate (OR’, 1.18; CI, 1.01, 1.38; p = 0.04). The two products were equipotent in all metrics used to assess intragastric pH except for the % patients maintaining a 24 h gastric pH above 4 (1.57; CI, 1.04, 2.381; p = 0.03).

Conclusion

The therapeutic benefit of chiral switch of omeprazole is questionable considering the substantially greater economic burden involved.

Improved enantioselectivity of thermostable esterase from Archaeoglobus fulgidus toward (S)-ketoprofen ethyl ester by directed evolution and characterization of mutant esterases

Thermostable esterases have potential applications in various biotechnology industries because of their resistance to high temperature and organic solvents. In a previous study, we isolated an esterase from Archaeoglobus fulgidus DSM 4304 (Est-AF), which showed high thermostability but low enantioselectivity toward (S)-ketoprofen ethyl ester. (R)-ketoprofenor (S)-ketoprofenis produced by esterase hydrolysis of the ester bond of (R,S)-ketoprofen ethyl ester and (S)-ketoprofen has better pharmaceutical activity and lower side effects than (R)-ketoprofen. Therefore, we have generated mutants of Est-AF that retained high thermostability whilst improving enantioselectivity. A library of Est-AF mutants was created by error-prone polymerase chain reaction, and mutants with improved enantioselectivity were isolated by site-saturation mutagenesis. The regions of Est-AF containing amino acid mutations were analyzed by homology modeling of its three-dimensional structure, and structure-based explanations for the changes in enantioselectivity are proposed. Finally, we isolated two mutants showing improved enantioselectivity over Est-AF (ee% = -16.2 ± 0.2 and E = 0.7 ± 0.0): V138G (ee% = 35.9 ± 1.0 and E = 3.0 ± 0.1) and V138G/L200R (ee% = 89.2 ± 0.2 and E = 19.5 ± 0.5). We also investigated various characteristics of these mutants and found that the mutants showed similar thermostability and resistance to additives or organic solvents to Est-AF, without a significant trade-off between activity and stability.

Bioanalysis of chiral compounds during drug development using a tiered approach

Significant differences in the pharmacodynamic activity and pharmacokinetic properties could exist for a pair of enantiomeric drugs. In order to evaluate the activity, toxicity, absorption, distribution, metabolism, and excretion properties of the individual enantiomers, and any potential for chiral inversion caused by the biotransformation process, chiral bioanalytical assays are necessary for individual enantiomers and/or their metabolites for in vivo samples. However, development and validation of chiral quantitative assays are highly challenging in comparison to typical nonchiral assays. Therefore, a tiered approach should be used to address specific needs arising in different scenarios of chiral drug development, including development of racemate or fixed-ratio (nonracemic) enantiomers, development of a single enantiomer, racemic switches, and quantitation of enantiomeric metabolites. The choice of a nonchiral quantitative assay, a chiral qualitative assay, or a chiral quantitative assay should be based on the development strategy and on the molecular properties of the drug candidate.

Comparison of frovatriptan plus dexketoprofen (25 mg or 37.5 mg) with frovatriptan alone in the treatment of migraine attacks with or without aura: a randomized study

BACKGROUND

Drugs for migraine attacks include triptans and NSAIDs; their combination could provide greater symptom relief.

METHODS

A total of 314 subjects with history of migraine, with or without aura, were randomized to frovatriptan 2.5 mg alone (Frova), frovatriptan 2.5 mg + dexketoprofen 25 mg (FroDex25) or frovatriptan 2.5 mg + dexketoprofen 37.5 mg (FroDex37.5) and treated at least one migraine attack. This was a multicenter, randomized, double-blind, parallel-group study. The primary end point was the proportion of pain free (PF) at two hours. Secondary end points were PF at one and four hours, pain relief (PR) at one, two, four hours, sustained PF (SPF) at 24 and 48 hours, recurrence at 48 hours, resolution of nausea, photophobia and phonophobia at two and four hours, the use of rescue medication and the judgment of the treatment.

RESULTS

The results were assessed in the full analysis set (FAS) population, which included all subjects randomized and treated for whom at least one post-dose intensity of headache was recorded. The proportions of subjects PF at two hours (primary end point) were 29% (27/93) with Frova compared with 51% (48/95 FroDex25 and 46/91 FroDex37.5) with each combination therapies ( P < 0.05). Proportions of SPF at 24 hours were 24% (22/93) for Frova, 43% (41/95) for FroDex25 ( P < 0.001) and 42% (38/91) for FroDex37.5 ( P < 0.05). SPF at 48 hours was 23% (21/93) with Frova, 36% (34/95) with FroDex25 and 33% (30/91) with FroDex37.5 ( P = NS). Recurrence was similar for Frova (22%, 6/27), FroDex25 (29%, 14/48) and FroDex37.5 (28%, 13/46) ( P = NS), meaning a lack of improvement with the combination therapy. Statistical adjustment for multiple comparisons was not performed. No statistically significant differences were reported in the occurrence of total and drug-related adverse events. FroDex25 and FroDex37.5 showed a similar efficacy both for primary and secondary end points. There did not seem to be a dose response curve for the addition of dexketoprofen.

CONCLUSION

FroDex improved initial efficacy at two hours compared to Frova whilst maintaining efficacy at 48 hours in this study. Tolerability profiles were comparable. Intrinsic pharmacokinetic properties of the two single drugs contribute to this improved efficacy profile.

Analysis of ketoprofen enantiomers in human and rat plasma by hollow-fiber-based liquid-phase microextraction and chiral mobile-phase additive HPLC

A simple, inexpensive, and efficient preconcentration and cleanup three-phase hollow fiber liquid-phase microextraction method (HF-LPME) was developed for the extraction of the anti-inflammatory ketoprofen (KTP) from human and rat plasma and HPLC enantioseparation of its enantiomers using vancomycin as a chiral mobile-phase additive with an achiral C8 column. The effects of different parameters influencing the efficiency of extraction were optimized for aqueous samples. Under optimized conditions, KTP enantiomers were extracted from 0.5 mL of plasma diluted to 5 mL with salinated and acidified deionized water (pH = 2) with 25 μL of alkalinized acceptor phase (pH = 11) during 30 min at room temperature. The mean recoveries of (−)-(R)- and (+)-(S)-KTP were 72.8% and 70.9%, respectively. The quantification limit was 20 ng/mL with linear response over the 20–2000 ng/mL concentration range for both enantiomers. Assay precision was studied within-day and between-day using 100 ng/mL KTP solutions. For both KTP enantiomers, relative standard deviations were lower than 12%. The proposed microextraction method was applied for the extraction of KTP enantiomers from human and rat plasma samples after oral administration of pure (±)-KTP in 4 mg/kg dosage for rats and 50 mg dosage for humans to assess the enantiospecific bioavailability of KTP enantiomers in their plasma. In vivo inversion studies revealed that the bioavailability of S-KTP is higher than that of the R enantiomers in rat, but they are similar in human plasma. The developed method showed that HF-LPME is a promising technique for sample preparation for the analyses of chiral drugs in biological samples.

Dexibuprofen for fever in children with upper respiratory tract infection

BACKGROUND

The aim of this study was to investigate the safety and efficacy of dexibuprofen compared to ibuprofen.

METHODS

This double-blind, double-dummy study enrolled patients from January 2008 to May 2009 presenting at one of five tertiary care centers in Seoul, Korea with febrile illness who were then given one of three active treatments: one dose of dexibuprofen 2.5 or 5 mg/kg (DEX 1); dexibuprofen 3.5 or 7 mg/kg (DEX 2); or ibuprofen 5 or 10 mg/kg (control) syrup. Those with a temperature <38.5°C were given the lower dose. Temperature was measured every hour for 4 h. Primary study outcome was mean change in temperature 4 h after one dose.

RESULTS

A total of 264 children (aged 6 months-14 years) with febrile illness due to upper respiratory tract infection were consecutively sampled and screened, with 260 randomized. No patients withdrew due to adverse effects. Mean temperature change after 4 h (mean ± SD: DEX 1, 0.99 ± 0.84°C; DEX 2, 1.12 ± 0.92°C; control, 1.38 ± 0.84°C) differed only between DEX 1 and controls (P = 0.007, 95% confidence interval [CI]: -0.61 to -0.15). When groups were subdivided according to initial temperature, there were no significant differences in mean temperature change after 4 h between DEX 2 subgroups (<38.5°C, 0.88 ± 0.86°C; ≥38.5°C, 1.46 ± 0.90°C) and controls (1.07 ± 0.84°C and 1.72 ± 0.91°C, respectively), but there was a significant difference between DEX 1 (≥38.5°C, 1.25 ± 0.76°C) and controls (P = 0.0222, 95%CI: -0.80 to -0.13). There were no significant differences in adverse events among groups.

CONCLUSION

Dexibuprofen (3.5 or 7 mg/kg) is as effective and tolerable as ibuprofen for fever caused by upper respiratory tract infection in children.

Determination of (S)-(+)- and (R)-(-)-ibuprofen enantiomers in human plasma after chiral precolumn derivatization by reversed-phase LC–ESI-MS/MS

Background: A selective, sensitive and high-throughput LC–ESI-MS/MS method has been developed and validated for the chromatographic separation and quantitation of (S)-(+)-ibuprofen and (R)-(-)-ibuprofen after derivatization with (S)-(-)-1-(1-napthyl)ethylamine using 1-hydroxybenzotriazole as the activator of the carboxylic acid group and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide as the coupling reagent in human plasma. Results: Both the analytes were chromatographically separated with a resolution factor of 1.27 on a Kinetex PFP (50 × 4.6 mm, 2.6 µm) analytical column. The method was validated over the concentration range of 0.10–32.0 µg/ml for both the enantiomers. The magnitude of matrix effect was assessed by post-column analyte infusion and also by precision (%CV) values for the calculated slopes of calibration curves. The mean extraction recovery was >91% for both the enantiomers. Conclusion: The method was successfully applied to a bioequivalence study in 34 healthy human subjects. The assay reproducibility was confirmed by reanalysis of 130 subject samples.

Enantiospecific ketoprofen concentrations in plasma after oral and intramuscular administration in growing pigs

Background

Ketoprofen is a non-steroidal anti-inflammatory drug which has been widely used for domestic animals. Orally administered racemic ketoprofen has been reported to be absorbed well in pigs, and bioavailability was almost complete. The objectives of this study were to analyze R- and S-ketoprofen concentrations in plasma after oral (PO) and intra muscular (IM) routes of administration, and to assess the relative bioavailability of racemic ketoprofen for both enantiomers between those routes of administration in growing pigs.

Methods

Eleven pigs received racemic ketoprofen at dose rates of 4 mg/kg PO and 3 mg/kg IM in a randomized, crossover design with a 6-day washout period. Enantiomers were separated on a chiral column and their concentrations were determined by liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were calculated and relative bioavailability (F_rel) was determined for S and R –ketoprofen.

Results

S-ketoprofen was the predominant enantiomer in pig plasma after administration of the racemic mixture via both routes. The mean (± SD) maximum S-ketoprofen concentration in plasma (7.42 mg/L ± 2.35 in PO and 7.32 mg/L ± 0.75 in IM) was more than twice as high as that of R-ketoprofen (2.55 mg/L ± 0.99 in PO and 3.23 mg/L ± 0.70 in IM), and the terminal half-life was three times longer for S-ketoprofen (3.40 h ± 0.91 in PO and 2.89 h ± 0.85 in IM) than R-ketoprofen (1.1 h ± 0.90 in PO and 0.75 h ± 0.48 in IM). The mean (± SD) relative bioavailability (PO compared to IM) was 83 ± 20% and 63 ± 23% for S-ketoprofen and R-ketoprofen, respectively.

Conclusions

Although some minor differences were detected in the ketoprofen enantiomer concentrations in plasma after PO and IM administration, they are probably not relevant in clinical use. Thus, the pharmacological effects of racemic ketoprofen should be comparable after intramuscular and oral routes of administration in growing pigs.

A new method for production of chiral 2-aryl-2-fluoropropanoic acids using an effective kinetic resolution of racemic 2-aryl-2-fluoropropanoic acids

We report a new method for the preparation of chiral 2-aryl-2-fluoropropanoic acids, including 2-fluoroibuprofen, a fluorinated analogue of non-steroidal anti-inflammatory drugs (NSAIDs), by the kinetic resolution of racemic 2-aryl-2-fluoropropanoic acids using enantioselective esterification. By applying pivalic anhydride (Piv₂O) as a coupling agent, bis(α-naphthyl)methanol [(α-Np)₂CHOH] as an achiral alcohol, and (+)-benzotetramisole (BTM) as a chiral acyl-transfer catalyst, a series of racemic 2-aryl-2-fluoropropanoic acids were kinetically separated to afford the optically active carboxylic acids and the corresponding esters with good to high enantiomeric excesses. This technology can provide a convenient approach to furnish the chiral α-fluorinated drugs containing quaternary carbons at the α-positions in the 2-aryl-2-fluoropropanoic acid structure.