scholarly journals Plasmodium falciparum histidine rich protein 2 (pfhrp2): an additional genetic marker suitable for anti-malarial drug efficacy trials

2022 ◽  
Vol 21 (1) ◽  
Author(s):  
Wahib M. Atroosh ◽  
Yee-Ling Lau ◽  
Georges Snounou ◽  
Meram Azzani ◽  
Hesham M. Al-Mekhlafi
Keyword(s):  
Clinical Trials ◽  
Plasmodium Falciparum ◽  
Drug Efficacy ◽  
Discrimination Analysis ◽  
Amplification Bias ◽  
Efficacy Trials ◽  
Polymorphic Genes ◽  
Pcr Rflp ◽  
Parasite Populations ◽  
Standard Strategy

Abstract Background Genotyping of the three Plasmodium falciparum polymorphic genes, msp1, msp2 and glurp, has been adopted as a standard strategy to distinguish recrudescence from new infection in drug efficacy clinical trials. However, the suitability of a particular gene is compromised in areas where its allelic variants distribution is significantly skewed, a phenomenon that might occur in isolated parasite populations or in areas of very low transmission. Moreover, observation of amplification bias has diminished the value of glurp as a marker. Methods The suitability of the polymorphic P. falciparum histidine-rich protein 2 (pfhrp2) gene was assessed to serve as an alternative marker using a PCR-sequencing or a PCR–RFLP protocol for genotyping of samples in drug efficacy clinical trials. The value of pfhrp2 was validated by side-by-side analyses of 5 admission-recrudescence sample pairs from Yemeni malaria patients. Results The outcome of the single pfhrp2 gene discrimination analysis has been found consistent with msp1, msp2 and glurp pool genotyping analysis for the differentiation of recrudescence from new infection. Conclusion The findings suggest that under the appropriate circumstances, pfhrp2 can serve as an additional molecular marker for monitoring anti-malarials efficacy. However, its use is restricted to endemic areas where only a minority of P. falciparum parasites lack the pfhrp2 gene.

scholarly journals Analytical validation of a real-time hydrolysis probe PCR assay for quantifying Plasmodium falciparum parasites in experimentally infected human adults

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Claire Y. T. Wang ◽  
Emma L. Ballard ◽  
Zuleima Pava ◽  
Louise Marquart ◽  
Jane Gaydon ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Plasmodium Falciparum ◽  
18S Rrna ◽  
Drug Efficacy ◽  
18S Rrna Gene ◽  
Molecular Techniques ◽  
Qpcr Assay ◽  
Rrna Gene ◽  
Analytical Sensitivity ◽  
Blood Samples

Abstract Background Volunteer infection studies have become a standard model for evaluating drug efficacy against Plasmodium infections. Molecular techniques such as qPCR are used in these studies due to their ability to provide robust and accurate estimates of parasitaemia at increased sensitivity compared to microscopy. The validity and reliability of assays need to be ensured when used to evaluate the efficacy of candidate drugs in clinical trials. Methods A previously described 18S rRNA gene qPCR assay for quantifying Plasmodium falciparum in blood samples was evaluated. Assay performance characteristics including analytical sensitivity, reportable range, precision, accuracy and specificity were assessed using experimental data and data compiled from phase 1 volunteer infection studies conducted between 2013 and 2019. Guidelines for validation of laboratory-developed molecular assays were followed. Results The reportable range was 1.50 to 6.50 log10 parasites/mL with a limit of detection of 2.045 log10 parasites/mL of whole blood based on a parasite diluted standard series over this range. The assay was highly reproducible with minimal intra-assay (SD = 0.456 quantification cycle (Cq) units [0.137 log10 parasites/mL] over 21 replicates) and inter-assay (SD = 0.604 Cq units [0.182 log10 parasites/mL] over 786 qPCR runs) variability. Through an external quality assurance program, the QIMR assay was shown to generate accurate results (quantitative bias + 0.019 log10 parasites/mL against nominal values). Specificity was 100% after assessing 164 parasite-free human blood samples. Conclusions The 18S rRNA gene qPCR assay is specific and highly reproducible and can provide reliable and accurate parasite quantification. The assay is considered fit for use in evaluating drug efficacy in malaria clinical trials.

scholarly journals Critical Evaluation of Molecular Monitoring in Malaria Drug Efficacy Trials and Pitfalls of Length-Polymorphic Markers

2016 ◽  
Vol 61 (1) ◽  
Author(s):  
Camilla Messerli ◽  
Natalie E. Hofmann ◽  
Hans-Peter Beck ◽  
Ingrid Felger
Keyword(s):  
Critical Evaluation ◽  
Drug Efficacy ◽  
Molecular Monitoring ◽  
Content Type ◽  
Amplification Bias ◽  
Efficacy Trials ◽  
Field Samples ◽  
Trial Endpoints ◽  
Preferential Amplification ◽  
The Impact

ABSTRACT Estimation of drug efficacy in antimalarial drug trials requires parasite genotyping to distinguish new infections from treatment failures. When using length-polymorphic molecular markers, preferential amplification of short fragments can compromise detection of coinfections, potentially leading to misclassification of treatment outcome. We quantified minority clone detectability and competition among msp1, msp2, and glurp amplicons using mixtures of Plasmodium falciparum strains and investigated the impact of template competition on genotyping outcomes in 44 paired field samples. Substantial amplification bias was detected for all three markers, with shorter fragments outperforming larger fragments. The strongest template competition was observed for the marker glurp. Detection of glurp fragments in multiclonal infections was severely compromised. Eight of 44 sample pairs were identified as new infections by all three markers. Ten pairs were defined as new infections based on one marker alone, seven of which were defined by the questionable marker glurp. The impact of size-dependent template competition on genotyping outcomes therefore calls for necessary amendments to the current WHO recommendations for PCR correction of malaria drug trial endpoints. Accuracy of genotyping outcomes could be improved by separate amplification reactions per allelic family and basing results on markers msp1 and msp2 first, with glurp only used to resolve discordant results.

scholarly journals Improving Methods for Analyzing Antimalarial Drug Efficacy Trials: Molecular Correction Based on Length-Polymorphic Markers msp-1, msp-2, and glurp

2019 ◽  
Vol 63 (9) ◽  
Author(s):  
S. Jones ◽  
K. Kay ◽  
E. M. Hodel ◽  
S. Chy ◽  
A. Mbituyumuremyi ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Failure Rate ◽  
Drug Efficacy ◽  
Economic Implications ◽  
Drug Effectiveness ◽  
Efficacy Trials ◽  
Large Numbers ◽  
Recommended Algorithm

ABSTRACT Drug efficacy trials monitor the continued efficacy of front-line drugs against falciparum malaria. Overestimating efficacy results in a country retaining a failing drug as first-line treatment with associated increases in morbidity and mortality, while underestimating drug effectiveness leads to removal of an effective treatment with substantial practical and economic implications. Trials are challenging: they require long durations of follow-up to detect drug failures, and patients are frequently reinfected during that period. Molecular correction based on parasite genotypes distinguishes reinfections from drug failures to ensure the accuracy of failure rate estimates. Several molecular correction “algorithms” have been proposed, but which is most accurate and/or robust remains unknown. We used pharmacological modeling to simulate parasite dynamics and genetic signals that occur in patients enrolled in malaria drug clinical trials. We compared estimates of treatment failure obtained from a selection of proposed molecular correction algorithms against the known “true” failure rate in the model. Our findings are as follows. (i) Molecular correction is essential to avoid substantial overestimates of drug failure rates. (ii) The current WHO-recommended algorithm consistently underestimates the true failure rate. (iii) Newly proposed algorithms produce more accurate failure rate estimates; the most accurate algorithm depends on the choice of drug, trial follow-up length, and transmission intensity. (iv) Long durations of patient follow-up may be counterproductive; large numbers of new infections accumulate and may be misclassified, overestimating drug failure rate. (v) Our model was highly consistent with existing in vivo data. The current WHO-recommended method for molecular correction and analysis of clinical trials should be reevaluated and updated.

Novel Pharmacotherapeutics for Stress-Related Disorders

2019 ◽  
pp. 642-672
Author(s):  
Jamie E. Mondello ◽  
Jenny E. Pak ◽  
Dennis F. Lovelock ◽  
Terrence Deak
Keyword(s):  
Mental Health Problems ◽  
Drug Efficacy ◽  
Careful Consideration ◽  
Pharmacological Intervention ◽  
Pharmacological Interventions ◽  
Diverse Range ◽  
Disease States ◽  
Efficacy Trials ◽  
Participant Selection ◽  
The Relationship

Most mental health problems associated with psychological distress originate with activation of centrally regulated stress pathways, yet a diverse range of central nervous system and somatic disease states can be influenced by exposure to severe or unrelenting stress. The goal of this chapter is to provide a conceptual framework to guide the development of pharmacological intervention strategies. We propose that careful consideration of the relationship between the timing of stressful life experiences, pharmacological intervention, and the ultimate expression of disease symptomatology is critical for the development of pharmacological interventions to treat stress-related disorders. We review a range of physiological systems that are known to be activated by stress, offering potentially new targets for drug development efforts, and argue that participant selection is a key predictor of drug efficacy trials. In doing so, we point toward inflammatory signaling pathways as a potential final common mediator of multiple stress-related disease states.

Use of a placebo in clinical trials

1998 ◽  
Vol 13 (5) ◽  
pp. 254-263 ◽  
Author(s):  
G Emilien ◽  
JM Maloteaux ◽  
A Seghers ◽  
G Charles
Keyword(s):  
Clinical Trials ◽  
Placebo Response ◽  
Drug Efficacy ◽  
Placebo Treatment ◽  
High Response Rate ◽  
Experimental Methodology ◽  
Necessary Condition ◽  
Control Group ◽  
Placebo Control ◽  
Experimental Drug

SummaryThe use of a placebo control group in the evaluation of a new product is today considered by most as a necessary condition of experimental drug research. Placebo response is an essential consideration in all clinical trials. If not properly controlled, incorrect and dangerous conclusion may be inferred for a product efficacy and safety profile. However, the inclusion of a placebo group in clinical trials in neuropsychiatric research raises several ethical and scientific questions. Whereas in certain indications, such as suicidal patients and severe and psychotic depression, the use of a placebo is generally not accepted, it is difficult to assess drug efficacy. This article discusses the concept of placebo in clinical trials, the occurrence of adverse events after placebo treatment and the high response rate of placebo in neuropsychiatric clinical research. The experimental methodology to adequately control all the factors involved is also analysed and discussed.

scholarly journals Improving the Role and Contribution of Pharmacokinetic Analyses in Antimalarial Drug Clinical Trials

2014 ◽  
Vol 58 (10) ◽  
pp. 5643-5649 ◽  
Author(s):  
Katherine Kay ◽  
Eva Maria Hodel ◽  
Ian M. Hastings
Keyword(s):  
Antimalarial Drug ◽  
Theoretical Data ◽  
Drug Efficacy ◽  
Cost Effective ◽  
Field Studies ◽  
World Health ◽  
Efficacy Trials ◽  
Drug Concentrations ◽  
Health Organization ◽  
Study Designs

ABSTRACTIt is now World Health Organization (WHO) policy that drug concentrations on day 7 be measured as part of routine assessment in antimalarial drug efficacy trials. The rationale is that this single pharmacological measure serves as a simple and practical predictor of treatment outcome for antimalarial drugs with long half-lives. Herein we review theoretical data and field studies and conclude that the day 7 drug concentration (d7c) actually appears to be a poor predictor of therapeutic outcome. This poor predictive capability combined with the fact that many routine antimalarial trials will have few or no failures means that there appears to be little justification for this WHO recommendation. Pharmacological studies have a huge potential to improve antimalarial dosing, and we propose study designs that use more-focused, sophisticated, and cost-effective ways of generating these data than the mass collection of single d7c concentrations.

scholarly journals Progress and challenges in TB vaccine development

F1000Research ◽  
2018 ◽  
Vol 7 ◽  
pp. 199 ◽  
Author(s):  
Gerald Voss ◽  
Danilo Casimiro ◽  
Olivier Neyrolles ◽  
Ann Williams ◽  
Stefan H.E. Kaufmann ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Vaccine Development ◽  
Scientific Progress ◽  
Human Infection ◽  
Experimental Medicine ◽  
Vaccine Platform ◽  
Vaccine Candidates ◽  
Clinical Endpoints ◽  
Immune Correlates ◽  
Efficacy Trials

The Bacille Calmette Guerin (BCG) vaccine can provide decades of protection against tuberculosis (TB) disease, and although imperfect, BCG is proof that vaccine mediated protection against TB is a possibility. A new TB vaccine is, therefore, an inevitability; the question is how long will it take us to get there? We have made substantial progress in the development of vaccine platforms, in the identification of antigens and of immune correlates of risk of TB disease. We have also standardized animal models to enable head-to-head comparison and selection of candidate TB vaccines for further development.  To extend our understanding of the safety and immunogenicity of TB vaccines we have performed experimental medicine studies to explore route of administration and have begun to develop controlled human infection models. Driven by a desire to reduce the length and cost of human efficacy trials we have applied novel approaches to later stage clinical development, exploring alternative clinical endpoints to prevention of disease outcomes. Here, global leaders in TB vaccine development discuss the progress made and the challenges that remain. What emerges is that, despite scientific progress, few vaccine candidates have entered clinical trials in the last 5 years and few vaccines in clinical trials have progressed to efficacy trials. Crucially, we have undervalued the knowledge gained from our “failed” trials and fostered a culture of risk aversion that has limited new funding for clinical TB vaccine development. The unintended consequence of this abundance of caution is lack of diversity of new TB vaccine candidates and stagnation of the clinical pipeline. We have a variety of new vaccine platform technologies, mycobacterial antigens and animal and human models.  However, we will not encourage progression of vaccine candidates into clinical trials unless we evaluate and embrace risk in pursuit of vaccine development.

scholarly journals Probing Plasmodium falciparum sexual commitment at the single-cell level

2018 ◽  
Vol 3 ◽  
pp. 70 ◽  
Author(s):  
Nicolas M.B. Brancucci ◽  
Mariana De Niz ◽  
Timothy J. Straub ◽  
Deepali Ravel ◽  
Lauriane Sollelis ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Life Cycle ◽  
Single Cell ◽  
Transcriptional Profiling ◽  
Quantitative Imaging ◽  
Complex Life Cycle ◽  
Major Transitions ◽  
Transcriptional Signature ◽  
Life Cycle Stages ◽  
Parasite Populations

Background: Malaria parasites go through major transitions during their complex life cycle, yet the underlying differentiation pathways remain obscure. Here we apply single cell transcriptomics to unravel the program inducing sexual differentiation in Plasmodium falciparum. Parasites have to make this essential life-cycle decision in preparation for human-to-mosquito transmission. Methods: By combining transcriptional profiling with quantitative imaging and genetics, we defined a transcriptional signature in sexually committed cells. Results: We found this transcriptional signature to be distinct from general changes in parasite metabolism that can be observed in response to commitment-inducing conditions. Conclusions: This proof-of-concept study provides a template to capture transcriptional diversity in parasite populations containing complex mixtures of different life-cycle stages and developmental programs, with important implications for our understanding of parasite biology and the ongoing malaria elimination campaign.

scholarly journals Soluble biological markers in osteoarthritis

2021 ◽  
Vol 13 ◽  
pp. 1759720X2110403
Author(s):  
Jean-Charles Rousseau ◽  
Roland Chapurlat ◽  
Patrick Garnero
Keyword(s):  
Clinical Trials ◽  
Biological Markers ◽  
Biochemical Markers ◽  
Drug Efficacy ◽  
Cost Effective ◽  
Type Ii Collagen ◽  
Cartilage Matrix ◽  
Joint Tissue ◽  
Cost Effective Approach ◽  
Selection Of

In recent years, markers research has focused on the structural components of cartilage matrix. Specifically, a second generation of degradation markers has been developed against type II collagen neoepitopes generated by specific enzymes. A particular effort has been made to measure the degradation of minor collagens III and X of the cartilage matrix. However, because clinical data, including longitudinal controlled studies, are very scarce, it remains unclear whether they will be useful as an alternative to or in combination with current more established collagen biological markers to assess patients with osteoarthritis (OA). In addition, new approaches using high-throughput technologies allowed to detect new types of markers and improve the knowledge about the metabolic changes linked to OA. The relative advances coming from phenotype research are a first attempt to classify the heterogeneity of OA, and several markers could improve the phenotype characterization. These phenotypes could improve the selection of patients in clinical trials limiting the size of the studies by selecting patients with OA characteristics corresponding to the metabolic pathway targeted by the molecules evaluated. In addition, the inclusion of rapid progressors only in clinical trials would facilitate the demonstration of efficacy of the investigative drug to reduce joint degradation. The combination of selective biochemical markers appears as a promising and cost-effective approach to fulfill this unmet clinical need. Among the various potential roles of biomarkers in OA, their ability to monitor drug efficacy is probably one of the most important, in association with clinical and imaging parameters. Biochemical markers have the unique property to detect changes in joint tissue metabolism within a few weeks.

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