Dr Thomas Pouplin

Research Area: Global Health
Technology Exchange: Mass spectrometry
Scientific Themes: Tropical Medicine & Global Health and Clinical Trials & Epidemiology

I am a senior scientist at the Mahidol-Oxford Tropical Medicine Research Unit (MORU) in Thailand since 2011. During 2007-2011, I worked at the Oxford Research Unit in Vietnam. I have conducted research in Vietnam and Thailand for the past 7 years and have extensive analytical experience from working with liquid chromatography (LC) coupled with UV detection and low resolution mass spectrometry (Triple Quadrupoles). I also have experience from high resolution Mass Spectrometry (Q-TOF) and 1/2D NMR acquired during my PhD-training.

My research focuses on developing bioanalytical methodologies to evaluate drug quality of locally produced pharmaceuticals, and the pharmacology of clinically used anti-infectious drugs in dengue fever, viral encephalitis and tuberculosis (TB). For this purpose we benefit from the ISO certified analytical laboratories at MORU. All bioanalytical LC-MS methods are developed and validated under a QA/QC system which is unique to the South East Asia Wellcome Programme.

Recently, I have focused my research interest on infections in the central nervous system and in particular Tuberculous Meningitis (TBM). By using liquid chromatography coupled with tandem MS, I have developed an ultra-sensitive simultaneous quantification of the four first-line anti-TB drugs rifampicin, isoniazid, pyrazinamide and ethambutol in both plasma and cerebrospinal fluid (CSF). This allows us to investigate the exposure of anti-TB drugs in CSF, but reliable markers are lacking for diagnostics and treatment response monitoring in TBM. Only a non-targeted lipidomics will allow apprehending novel information about CSF lipids specifically present in patients. To estimate the feasibility of capturing low concentrations of many distinct lipid species from a small volume of a complex mixture, I have launched a pilot research project analysing  selected CSF samples on a high accuracy MS system. The outcome of this pilot study will allow adjusting the design of the lipidomics of CSF in TBM by powering the sample size, optimising the detection and inform us on a pragmatic choice for the control groups.

There are no collaborations listed for this principal investigator.

Van Toi P, Pouplin T, Tho NDK, Phuong PN, Chau TTH, Thuong Thuong NT, Heemskerk D, Hien TT, Thwaites GE. 2017. High-performance liquid chromatography with time-programmed fluorescence detection for the quantification of Levofloxacin in human plasma and cerebrospinal fluid in adults with tuberculous meningitis. J Chromatogr B Analyt Technol Biomed Life Sci, 1061-1062 pp. 256-262. | Show Abstract | Read more

An accurate and reliable high-performance liquid chromatography with time-programmed fluorescence detection was developed and validated to measure levofloxacin in human plasma and cerebrospinal fluid (CSF). After solid phase extraction process using Evolute®ABN 96 fixed well plate; levofloxacin and internal standard-enoxacin were separated using a mobile phase consisting of phosphate buffer 10mM with 0.025% triethylamine pH 3.0 - acetonitrile (88:12, v/v) on a Purosphere RP-8e column (5μm, 125×4.0mm) at a flow rate of 1.2mL/min at 35°C. The excitation/emission wavelengths were set to 269/400nm and 294/500nm, for enoxacin and levofloxacin, respectively. The method was linear over the concentration range of 0.02 to 20.0μg/mL with a limit of detection of 0.01μg/mL. The relative standard deviation of intra-assay and inter-assay precision for levofloxacin at four quality controls concentrations (0.02, 0.06, 3.0 and 15.0μg/mL) were less than 7% and the accuracies ranged from 96.75% to 101.9% in plasma, and from 93.00% to 98.67% in CSF. The validated method was successfully applied to quantify levofloxacin in a considerable quantity of plasma (826) and CSF (477) samples collected from 232 tuberculous meningitis patients, and the preliminary intensive pharmacokinetics analysis from 14 tuberculous meningitis patients in Vietnam is described in this paper.

Van Pham T, Pham Nguyen P, Nguyen Duc Khanh T, Nguyen Thanh Thuy N, Nguyen Thuy Nha C, Pouplin T, Farrar J, Thwaites GE, Tran Tinh H. 2016. An HPLC method with diode array detector for the simultaneous quantification of chloroquine and desethylchloroquine in plasma and whole blood samples from Plasmodium vivax patients in Vietnam, using quinine as an internal standard. Biomed Chromatogr, 30 (7), pp. 1104-1111. | Show Abstract | Read more

A sensitive, simple method for quantification of chloroquine (CQ) and desethylchloroquine (MCQ) in whole blood and plasma from Plasmodium vivax patients has been developed using HPLC with diode array detection (DAD). Solid-phase extraction on Isolute-96-CBA was employed to process 100 μL of plasma/whole blood samples. CQ, MCQ and quinine were separated using a mobile phase of phosphate buffer 25 mm, pH 2.60-acetonitrile (88:12, v/v) with 2 mm sodium perchlorate on a Zorbax SB-CN 150 × 4.6 mm, 5 μm column at a flow rate of 1.2 mL/min, at ambient temperature in 10 min, with the DAD wavelength of 343 nm. The method was linear over the range of 10-5000 ng/mL for both CQ and MCQ in plasma and whole blood. The limit of detection was 4 ng/mL and limit of quantification was 10 ng/mL in both plasma and blood for CQ and MCQ. The intra-, inter- and total assay precision were <10% for CQ and MCQ in plasma and whole blood. In plasma, the accuracies varied between 101 and 103%, whereas in whole blood, the accuracies ranged from 97.0 to 102% for CQ and MCQ. The method is an ideal technique with simple facilities and instruments, bringing about good separation in comparison with previous methods. © 2016 The Authors Biomedical Chromatography Published by John Wiley & Sons Ltd.

Pouplin T, Bang ND, Toi PV, Phuong PN, Dung NH, Duong TN, Caws M, Thwaites GE, Tarning J, Day JN. 2016. Naïve-pooled pharmacokinetic analysis of pyrazinamide, isoniazid and rifampicin in plasma and cerebrospinal fluid of Vietnamese children with tuberculous meningitis. BMC Infect Dis, 16 (1), pp. 144. | Show Abstract | Read more

BACKGROUND: Among the various forms of TB, tuberculous meningitis (TBM) is the most severe, with about 30% mortality and 50% of survivors left with neurological sequelae. Children suffer more frequently from TBM than adults and outcomes are often poor due to difficulties in making the diagnosis and uncertainty regarding the best anti-tuberculosis drug regimen. The aim of this prospective study was to describe the pharmacokinetics of pyrazinamide, isoniazid and rifampicin in plasma and cerebrospinal fluid of children with tuberculous meningitis treated with the standard TBM regimen. METHODS: We performed a prospective observational study of 100 consecutively treated children (≤ 15 years of age) with tuberculous meningitis in Ho Chi Minh City, Vietnam. Children were treated according to the 2006 WHO recommended pediatric treatment regimen consisting of isoniazid (5 mg/kg), rifampicin (10 mg/kg) and ethambutol (15 mg/kg) for 8 months, with the addition of pyrazinamide (25 mg/kg) for the first 3 months and streptomycin (15 mg/kg) for the first 2 months. Pyrazinamide, isoniazid and rifampicin concentrations were measured in plasma at day 14 and in cerebrospinal fluid (CSF) at 1 month by HPLC-UV. A naïve-pooled non-compartmental data analysis was used to describe the pharmacokinetic properties of drugs in the two-age groups of children ≤ 4 years or > 4 years of age. RESULTS: Younger children, when compared to older children, presented a higher body weight-normalized clearance and volume of distribution, and lower median total plasma exposures for the three studied drugs with -14%, -22% and -16% for Pyrazinamide, Isoniazid and Rifampicin, respectively. In CSF, individual concentrations of isoniazid and pyrazinamide were comparable to that in plasma in both age groups; but rifampicin concentrations were lower than the minimum inhibitory concentration of susceptible bacteria in all but two children. CONCLUSIONS: There is an age-dependent variation in the plasma and cerebrospinal fluid pharmacokinetics of rifampicin, isoniazid and pyrazinamide. The safety and efficacy of higher doses of rifampicin should be investigated for the treatment of childhood tuberculous meningitis.

Pouplin T, Phuong PN, Toi PV, Nguyen Pouplin J, Farrar J. 2014. Isoniazid, pyrazinamide and rifampicin content variation in split fixed-dose combination tablets. PLoS One, 9 (7), pp. e102047. | Show Abstract | Read more

SETTING: In most developing countries, paediatric tuberculosis is treated with split tablets leading to potential inaccuracy in the dose delivery and drug exposure. There is no data on the quality of first-line drugs content in split fixed-dose combination tablets. OBJECTIVE: To determine Isoniazid, Pyrazinamide and Rifampicin content uniformity in split FDC tablets used in the treatment of childhood tuberculosis. DESIGN: Drug contents of 15 whole tablets, 30 half tablets and 36 third tablets were analysed by high performance liquid chromatography. The content uniformity was assessed by comparing drug content measured in split portions with their expected amounts and the quality of split portions was assessed applying qualitative specifications for whole tablets. RESULTS: All whole tablets measurements fell into the USP proxy for the three drugs. But a significant number of half and third portions was found outside the tolerated variation range and the split formulation failed the requirements for content uniformity. To correct for the inaccuracy of splitting the tablets into equal portions, a weight-adjustment strategy was used but this did not improve the findings. CONCLUSION: In split tablets the content of the three drugs is non-uniform and exceeded the USP recommendations. There is an absolute need to make child-friendly formulations available for the treatment of childhood tuberculosis.

Sriboonvorakul N, Leepipatpiboon N, Dondorp AM, Pouplin T, White NJ, Tarning J, Lindegardh N. 2013. Liquid chromatographic-mass spectrometric method for simultaneous determination of small organic acids potentially contributing to acidosis in severe malaria. J Chromatogr B Analyt Technol Biomed Life Sci, 941 pp. 116-122. | Show Abstract | Read more

Acidosis is an important cause of mortality in severe falciparum malaria. Lactic acid is a major contributor to metabolic acidosis, but accounts for only one-quarter of the strong anion gap. Other unidentified organic acids have an independent strong prognostic significance for a fatal outcome. In this study, a simultaneous bio-analytical method for qualitative and quantitative assessment in plasma and urine of eight small organic acids potentially contributing to acidosis in severe malaria was developed and validated. High-throughput strong anion exchange solid-phase extraction in a 96-well plate format was used for sample preparation. Hydrophilic interaction liquid chromatography (HILIC) coupled to negative mass spectroscopy was utilized for separation and detection. Eight possible small organic acids; l-lactic acid (LA), α-hydroxybutyric acid (aHBA), β-hydroxybutyric acid (bHBA), p-hydroxyphenyllactic acid (pHPLA), malonic acid (MA), methylmalonic acid (MMA), ethylmalonic acid (EMA) and α-ketoglutaric acid (aKGA) were analyzed simultaneously using a ZIC-HILIC column with an isocratic elution containing acetonitrile and ammonium acetate buffer. This method was validated according to U.S. Food and Drug Administration guidelines with additional validation procedures for endogenous substances. Accuracy for all eight acids ranged from 93.1% to 104.0%, and the within-day and between-day precisions (i.e. relative standard deviations) were lower than 5.5% at all tested concentrations. The calibration ranges were: 2.5-2500μg/mL for LA, 0.125-125μg/mL for aHBA, 7.5-375μg/mL for bHBA, 0.1-100μg/mL for pHPLA, 1-1000μg/mL for MA, 0.25-250μg/mL for MMA, 0.25-100μg/mL for EMA, and 30-1500μg/mL for aKGA. Clinical applicability was demonstrated by analyzing plasma and urine samples from five patients with severe falciparum malaria; five acids had increased concentrations in plasma (range LA=177-1169μg/mL, aHBA=4.70-38.4μg/mL, bHBA=7.70-38.0μg/mL, pHPLA=0.900-4.30μg/mL and aKGA=30.2-32.0) and seven in urine samples (range LA=11.2-513μg/mL, aHBA=1.50-69.5μg/mL, bHBA=8.10-111μg/mL, pHPLA=4.30-27.7μg/mL, MMA=0.300-13.3μg/mL, EMA=0.300-48.1μg/mL and aKGA=30.4-107μg/mL). In conclusion, a novel bioanalytical method was developed and validated which allows for simultaneous quantification of eight small organic acids in plasma and urine. This new method may be a useful tool for the assessment of acidosis in patients with severe malaria, and other conditions complicated by acidosis.

Nguyen-Pouplin J, Pouplin T, Van TP, The TD, Thi DN, Farrar J, Tinh HT, Wills B. 2011. Dextran fractional clearance studies in acute dengue infection. PLoS Negl Trop Dis, 5 (8), pp. e1282. | Show Abstract | Read more

BACKGROUND: Although increased capillary permeability is the major clinical feature associated with severe dengue infections the mechanisms underlying this phenomenon remain unclear. Dextran clearance methodology has been used to investigate the molecular sieving properties of the microvasculature in clinical situations associated with altered permeability, including during pregnancy and in various renal disorders. In order to better understand the characteristics of the vascular leak associated with dengue we undertook formal dextran clearance studies in Vietnamese dengue patients and healthy volunteers. METHODOLOGY/PRINCIPAL FINDINGS: We carried out serial clearance studies in 15 young adult males with acute dengue and evidence of vascular leakage a) during the phase of maximal leakage and b) one and three months later, as well as in 16 healthy control subjects. Interestingly we found no difference in the clearance profiles of neutral dextran solutions among the dengue patients at any time-point or in comparison to the healthy volunteers. CONCLUSIONS/SIGNIFICANCE: The surface glycocalyx layer, a fibre-matrix of proteoglycans, glycosaminoglycans, and plasma proteins, forms a complex with the underlying endothelial cells to regulate plasma volume within circumscribed limits. It is likely that during dengue infections loss of plasma proteins from this layer alters the permeability characteristics of the complex; physical and/or electrostatic interactions between the dextran molecules and the glycocalyx structure may temporarily restore normal function, rendering the technique unsuitable for assessing permeability in these patients. The implications for resuscitation of patients with dengue shock syndrome (DSS) are potentially important. It is possible that continuous low-dose infusions of dextran may help to stabilize the permeability barrier in patients with profound or refractory shock, reducing the need for repeated boluses, limiting the total colloid volume required. Formal clinical studies should help to assess this strategy as an alternative to conventional fluid resuscitation for severe DSS.

Pouplin T, Pouplin JN, Van Toi P, Lindegardh N, Rogier van Doorn H, Hien TT, Farrar J, Török ME, Chau TTH. 2011. Valacyclovir for herpes simplex encephalitis. Antimicrob Agents Chemother, 55 (7), pp. 3624-3626. | Show Abstract | Read more

The recommended treatment for herpes simplex encephalitis (HSE) remains intravenous acyclovir. In resource-poor countries, however, intravenous formulations are usually unavailable or unaffordable. We report the penetration of acyclovir into the cerebrospinal fluid (CSF) in patients with HSE, treated with the oral prodrug valacyclovir at 1,000 mg three times daily. The oral therapy achieved adequate acyclovir concentrations in the CSF and may be an acceptable early treatment for suspected HSE in resource-limited settings.

Heemskerk D, Day J, Chau TTH, Dung NH, Yen NTB, Bang ND, Merson L, Olliaro P, Pouplin T, Caws M et al. 2011. Intensified treatment with high dose rifampicin and levofloxacin compared to standard treatment for adult patients with tuberculous meningitis (TBM-IT): protocol for a randomized controlled trial. Trials, 12 (1), pp. 25. | Show Abstract | Read more

BACKGROUND: Tuberculous meningitis is the most severe form of tuberculosis. Mortality for untreated tuberculous meningitis is 100%. Despite the introduction of antibiotic treatment for tuberculosis the mortality rate for tuberculous meningitis remains high; approximately 25% for HIV-negative and 67% for HIV positive patients with most deaths occurring within one month of starting therapy. The high mortality rate in tuberculous meningitis reflects the severity of the condition but also the poor antibacterial activity of current treatment regimes and relatively poor penetration of these drugs into the central nervous system. Improving the antitubercular activity in the central nervous system of current therapy may help improve outcomes. Increasing the dose of rifampicin, a key drug with known poor cerebrospinal fluid penetration may lead to higher drug levels at the site of infection and may improve survival. Of the second generation fluoroquinolones, levofloxacin may have the optimal pharmacological features including cerebrospinal fluid penetration, with a ratio of Area Under the Curve (AUC) in cerebrospinal fluid to AUC in plasma of >75% and strong bactericidal activity against Mycobacterium tuberculosis. We propose a randomized controlled trial to assess the efficacy of an intensified anti-tubercular treatment regimen in tuberculous meningitis patients, comparing current standard tuberculous meningitis treatment regimens with standard treatment intensified with high-dose rifampicin and additional levofloxacin. METHODS/DESIGN: A randomized, double blind, placebo-controlled trial with two parallel arms, comparing standard Vietnamese national guideline treatment for tuberculous meningitis with standard treatment plus an increased dose of rifampicin (to 15 mg/kg/day total) and additional levofloxacin. The study will include 750 patients (375 per treatment group) including a minimum of 350 HIV-positive patients. The calculation assumes an overall mortality of 40% vs. 30% in the two arms, respectively (corresponding to a target hazard ratio of 0.7), a power of 80% and a two-sided significance level of 5%. Randomization ratio is 1:1. The primary endpoint is overall survival, i.e. time from randomization to death during a follow-up period of 9 months. Secondary endpoints are: neurological disability at 9 months, time to new neurological event or death, time to new or recurrent AIDS-defining illness or death (in HIV-positive patients only), severe adverse events, and rate of treatment interruption for adverse events. DISCUSSION: Currently very few options are available for the treatment of TBM and the mortality rate remains unacceptably high with severe disabilities seen in many of the survivors. This trial is based on the hypothesis that current anti-mycobacterial treatment schedules for TBM are not potent enough and that outcomes will be improved by increasing the CSF penetrating power of this regimen by optimising dosage and using additional drugs with better CSF penetration. TRIAL REGISTRATION: International Standard Randomised Controlled Trial Number ISRCTN61649292.

Pouplin T, Tolon B, Nuhant P, Delpech B, Marazano C. 2007. Synthetic studies towards bridgehead diprenyl-substituted bicyclo[3.3.1]nonane-2,9-diones as models for polyprenylated acylphloroglucinol construction EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, 2007 (30), pp. 5117-5125. | Show Abstract | Read more

The synthesis of bridgehead diprenylated bicyclo[3.3.1]-nonane-2,9-dione, based on a reductive rearrangement of an enol lactone, is presented. The same target could be reached by a one-step sequence involving Michael addition of 2,6-diprenylcyclohexanone onto acrolein and intramolecular aldol reaction. The first method could be extended to the formation of a compound with gem-dimethyl substituents adjacent to the bridgehead position, but the construction of a suitably substituted enol lactone, with a view to polyprenylated acylphloroglucinol elaboration, could not be achieved. © Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Nuhant P, David M, Pouplin T, Delpech B, Marazano C. 2007. Alpha,alpha'-annulation of 2,6-prenyl-substituted cyclohexanone derivatives with malonyl chloride: application to a short synthesis of (+/-)-clusianone. Formation and rearrangement of a biogenetic-like intermediate. Org Lett, 9 (2), pp. 287-289. | Show Abstract | Read more

Conditions were found for the successful Effenberger alpha,alpha'-annulation of 3,3-dimethyl-2,4,6-triprenyl cyclohexanone silyl enol ethers with malonyl chloride to give the corresponding bicyclo[3.3.1]nonane-trione in 35% yield, this result allowing a short synthesis of (+/-)-clusianone. An isomeric rearranged bicyclo[3.3.1]nonane-trione was also isolated in 25% yield, and changing the Lewis acid resulted in formation of a lavandulyl-substituted phloroglucinol derivative in 38% yield. The mechanism of formation of these two last products mimics the biogenetic pathway to PPAPs. [reaction: see text].

Um BH, Weniger B, Lobstein A, Pouplin T, Polat M, Aragón R, Anton R. 2001. Triterpenoid saponins from Isertia pittieri. J Nat Prod, 64 (12), pp. 1588-1589. | Show Abstract | Read more

Two new 27-nor-triterpenoid saponins, pyrocincholic acid 3 beta-O-beta-D-quinovopyranosyl-28-[beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranosyl] ester (1) and pyrocincholic acid 3 beta-O-beta-D-quinovopyranosyl(1-->6)-beta-D-glucopyranosyl-28-[beta-D-glucopyranosyl(1-->2)-beta-D-glucopyranosyl] ester (2) were isolated from the stem bark of Isertia pittieri, together with two known bidesmosidic quinovic acid glycosides. The structures of 1 and 2 were determined on the basis of spectroscopic studies.

Um BH, Pouplin T, Lobstein A, Weniger B, Litaudon M, Anton R. 2001. Saponins from Strasburgeria robusta. Fitoterapia, 72 (5), pp. 591-593. | Show Abstract | Read more

The isolation of three saponins, 24-hydroxytormentic acid ester glucoside (1), niga-ichigoside F1 (2) and niga-ichigoside F2 (3), from the stem bark of Strasburgeria robusta, an endemic plant from New Caledonia, is reported.

Pouplin T, Pouplin JN, Van Toi P, Lindegardh N, Rogier van Doorn H, Hien TT, Farrar J, Török ME, Chau TTH. 2011. Valacyclovir for herpes simplex encephalitis. Antimicrob Agents Chemother, 55 (7), pp. 3624-3626. | Show Abstract | Read more

The recommended treatment for herpes simplex encephalitis (HSE) remains intravenous acyclovir. In resource-poor countries, however, intravenous formulations are usually unavailable or unaffordable. We report the penetration of acyclovir into the cerebrospinal fluid (CSF) in patients with HSE, treated with the oral prodrug valacyclovir at 1,000 mg three times daily. The oral therapy achieved adequate acyclovir concentrations in the CSF and may be an acceptable early treatment for suspected HSE in resource-limited settings.