New guide for malaria researchers
An expert biostatistician from the Centre for Molecular, Environmental, Genetic and Analytic (MEGA) Epidemiology within the Melbourne School of Population and Global Health is helping to save lives through her work on a new guide for malaria researchers. The World Health Organization (WHO) enlisted Associate Professor Julie Simpson to lead an international team to contribute a key chapter to the guide, which is a world first. Methods and Techniques for Assessing Exposure to Antimalarial Drugs in Clinical Field Studies, an essential tool for any researchers starting new clinical trials of an anti-malarial drug anywhere on the globe, was published in late 2011. Associate Professor Simpson's international standing in malaria research, led WHO to select her to chair the chapter on sampling schemes for pharmacokinetic studies. Pharmacokinetics is the process by which a drug is absorbed, used and eliminated by the body. Associate Professor Simpson's work in this specialty since 1996 includes four years in South East Asia, an experience that enriched her understanding of both the complexities of field work and her own contribution as a biostatistician.
In 2010, malaria infected about 216 million people and killed an estimated 655,000, and clinical malaria researchers may work under extremely difficult circumstances, such as collecting blood samples from patients in remote areas, she says.
The chapter on optimised sampling schemes provides practical recommendations for each drug, offering strategies that cover critical factors like how many patients to test, and the number and timing of samples in order to exploit the most information rich 'sampling window'. These designs for new pharmacokinetic studies are feasible for the researchers in the field and should result in more accurate estimation of the drug concentration profile, an essential research resource that has been lacking until now, she says.Under current WHO dosing regimes, all patients get the same weight-adjusted dose. "There is no adjustment for children or pregnant women or people with HIV, for example," Associate Professor Simpson says. "It would be worth doing more of these studies to know if it's okay to give everyone the same regimen."The poor quality of anti-malarial pharmacokinetic studies was evident from the international literature review done by her team of experts from Thailand, the United Kingdom and South Africa, in preparing the chapter. Over 14 months, they sourced all available studies, extracted all the data from tables, and then simulated profiles for each drug before determining the optimal sampling windows. Associate Professor Simpson says the rise of resistance to the highly effective artemisinin derivatives, the most widely used anti-malarial drugs, has highlighted the need for pharmacokinetics to become a higher research priority, rather than an "add on" to other clinical studies. "I think the new guide will ultimately improve the proportion of patients who are cured from the treatment," she says. "And because we are going to be doing better designed studies, it means we will get more information from the data we collect which, in turn, will improve dosing regimens."And the better our dosing regimens in all study populations, the more effective the treatment will be." Reliable pharmacokinetic data on specific drugs can, when a treatment is proving ineffective, help to distinguish between sub-optimal dosing and drug resistance, with the former contributing to the latter by exposing the malaria parasite to dosages that are too low to effectively eliminate it.