African scientist receives prestigious German research accolade
- Wits University
Alexander Humboldt Award bestowed on pharmacogeneticist Prof. Collen Masimirembwa for dedication to ensuring Africans receive safe, efficacious medicines.
The work of Professor Collen Masimirembwa combines human genetics, drug metabolism, and pharmacokinetics research in predicting drug response.
One important result of his work is a genetic test and dosing algorithm that is being clinically validated across Africa
A Distinguished Professor in the Sydney Brenner Institute for Molecular Bioscience (SBIMB) at Wits, Masimirembwa is among two Africans to have received the Alexander Humboldt Award, which has also been bestowed on 61 Nobel laureates.
Fostering international collaboration in cutting-edge medicine
The award aims to promote collaboration between leading international researchers and their German counterparts. Masimirembwa will build research collaboration between German and African institutions through advanced research in the field of pharmacokinetics and pharmacogenetics. In Germany, he will work closely with his long-time research collaborator, Professor Dr Julia Stingl at the University of Heidelberg.
What is pharmacokinetics and pharmacogenetics?
Pharmacokinetics investigates how the body handles medicines that we take when we are sick. It involves processes such as absorption, distribution, metabolism, and excretion (ADME).
Pharmacogenetics, on the other hand, is a sub-discipline of pharmacokinetics that investigates how a person’s genetic makeup affects their body’s processing of medication.
Bringing African diversity to the heart of medicine development
Over the past 30 years, Masimiremwba’s research has focused on the pharmacokinetics and pharmacogenetics of medicines when used in people of African ancestry. Often, when medicines are used in African populations, there can be adverse effects because almost all drugs on the market have been developed and optimised for safety and efficacy in people of European ancestry.
Masimirembwa’s pioneering work showed that there were different safety and efficacy profiles for Africans regarding the HIV drug, Efaviraz, the breast cancer drug, Tamoxifen, the anti-organ rejection drug, Tacrolimus, the anti-coagulant drug, Warfarin, and others.
“We uncovered the genetic reasons for these responses and therefore advocated for the need to take into account Africa’s genomic diversity in the clinical development of new medicines,” says Masimirembwa.
Unpacking the risk of drug interactions in African patients
When patients take two or more medications, the way one drug is processed in the body can be affected by the other. This is known as a drug-drug interaction. It happens when one drug interferes with enzymes or transporters that handle how another drug is absorbed, broken down, or eliminated.
“In Africa, this issue is particularly concerning. Many people are being treated for infectious diseases like HIV, tuberculosis, and schistosomiasis—all of which often require multiple medications. At the same time, there’s a rising number of patients with long-term non-communicable diseases like diabetes, heart disease, and mental health conditions. As a result, more people are living with multiple health conditions [co-morbidity] and are taking several drugs at once [polypharmacy]. This significantly increases the risk of harmful drug interactions,” he says.
Masimirembwa’s work has helped to uncover how these drug interactions happen in real-world clinical settings across Africa. For instance, he identified the enzyme that breaks down the antimalarial drug amodiaquine and showed how it can create toxic byproducts that harm the liver and blood.
In another recent study, he discovered a dangerous interaction between anti-HIV medications and praziquantel, a drug used to treat schistosomiasis (an acute and chronic disease caused by parasitic worms). Masimirembwa's findings are helping doctors make safer treatment choices by avoiding drug combinations that can cause harm.
A deeper dive into drug-drug-gene interactions
Under the prestigious Alexander von Humboldt Award, Masimirembwa and Stingl are working together to address one of the major challenges in modern medicine: how to safely treat patients who are prescribed many different medicines at the same time—particularly in the African context.
Consider, for example, an HIV patient who also contracts tuberculosis (TB), a common co-infection. Such a patient might be prescribed three drugs for HIV, three to four for TB, and may also have conditions such as diabetes or high blood pressure, which could require an additional four to five medications.
Across the continent, thousands of patients are on between five and fifteen medicines at once. This significantly increases the risk of harmful drug-drug interactions, where one medicine affects how another is processed in the body, leading to changes in effectiveness or causing serious side effects.
The challenge becomes even more complex when drug-gene interactions are also involved. In these cases, a person's genetic makeup influences how their body responds to specific medicines, either accelerating or slowing their metabolism. This can worsen drug-drug interactions and lead to poor treatment outcomes.
Through their collaboration, Masimirembwa and Stingl aim to unravel these overlapping drug and genetic interactions. Their goal is to support safer, more effective treatment strategies that take into account both the number of medicines a patient is taking and their individual genetic profile—helping to improve care for people across Africa who are living with multiple chronic conditions.
A shared vision for science and building African-led genetic research
Masimirembwa is the founding director of the African Institute of Biomedical Science and Technology in Harare, Zimbabwe. As Distinguished Professor at the Wits at SBIMB, he has teamed up with world-class researchers, professors and clinicians to build the pharmacogenomics research theme, ‘From research bench to patient bedside’, in South Africa.
Citation from the Alexander von Humboldt Foundation
The following is the Foundation’s citation for awarding Masimirembwa:
“Professor Masimirembwa is a leading scientist in the field of pharmacogenetics and has made pioneering work deciphering the genomic diversity of African populations and its implications for the safe and efficacious use of medicines. He combines human genetics, drug metabolism and pharmacokinetics research in predicting drug response. One important result of his work is a genetic test and dosing algorithm that is being clinically validated across Africa. During his research stay in Germany, he will explore the implementation of pharmacogenetic diagnostics in patients taking multiple drugs and will adapt it to the needs of African patients. He will also develop training material for the uptake of pharmacogenetics by medical practitioners.”