Dr. Darrell Tan

HIV Treatment in the Real World

Clinician Scientist at St. Michael’s Hospital,
Toronto and Assistant Professor University of Toronto

As Dr. Darrell Tan puts it, it was a convergence of many roads that led him to a research career in HIV. As an undergraduate in microbiology and immunology at McGill, Dr. Tan took an interest in international issues. “I found immunology and microbiology interesting and at the same time I became interested in problems of the developing world,” explains Dr. Tan. “I started to see the links between what I was learning in microbiology classrooms and what I was learning in international development and about the challenges that face us.” At the same time, coming out as a gay man and becoming part of a community that was marginalized and deeply affected by the HIV epidemic made the content hit close to home for Dr. Tan. “I realized that research in infectious diseases more broadly and HIV in particular was a career in which I felt I could have impact.”

Today, Dr. Tan’s research looks at HIV/AIDS prevention and treatment, and the management of associated sexually transmitted co-infections and co-morbidities. Currently, Dr. Tan and his colleagues, supported by CIHR, the CIHR Canadian HIV Trials Network, and OHTN, are conducting an open label clinical trial of daily oral Truvada as pre-exposure prophylaxis (PrEP) for MSM (Men Who Have Sex With Men) in Toronto. Its aim is to provide a real-world view on the use of PrEP. “We know from clinical trials that this intervention works to prevent HIV transmission when compared in a randomized placebo controlled fashion,” explains Dr. Tan. “But questions remain about PrEP implementation and uptake. How would people adhere to it? What will their experience with it be? What, as clinicians, can we do to support them?” The study also has a community based component where they will be evaluating the importance of community based organizations in referring patients to study, the type of patients they refer, and the organizations role in the rollout of and adherence to PrEP. The community based portion of the study is key as Dr. Tan feels that people’s realities are not always taken into account in research. “We need to find a way to reach people that is going to resonate with them. We need to find ways to support people in taking up interventions that we know have biologic efficacy.”

Another project that is ongoing for Dr. Tan and his colleagues is a clinical trial studying the anti-herpes medication valacyclovir. Supported by CIHR and the CIHR Canadian HIV Trials Network, he is conducting a placebo controlled randomized trial that is looking at whether valacyclovir slows HIV disease progression in people who are not on antiretroviral therapy. Initially, the study was conceived because herpes was thought to inversely impact HIV disease progression and by treating herpes, HIV progression could be slowed. However, some recent studies have questioned this relationship. But as Dr. Tan explains, “We’ve seen some other studies that suggest valacyclovir may be an anti-HIV drug in and of itself which suggests another mechanism by which it may be helpful.” In cases where antiretroviral therapy is delayed (in certain patients and according to guidelines in other countries), valacyclovir might be a way of treating HIV in the meantime. “It gives people the opportunity to get used to taking medication each day,” says Dr. Tan.

For Dr. Tan, it is still the opportunity to make a difference that inspires his work. “A few decades into this epidemic , STIs among HIV infected and at risk people as well as the HIV epidemic itself continue to be major problems; particularly concentrated in the MSM community,” says Dr. Tan. “I think the fact that this persists despite all the tremendous successes we have had is a real calamity. We can do better... and we should do better.”

The Canadian Association for HIV Research (CAHR), the CIHR HIV/AIDS Research Initiative, the Canadian Foundation for AIDS Research (CANFAR), the CIHR Canadian HIV Trials Network (CTN) and the Canadian HIV Vaccine Initiative (CHVI) Research and Development Alliance Coordinating Office (ACO) would like to thank Dr. Tan and his colleagues for their significant contributions to our understanding of HIV. Their work is part of a larger Canadian effort that is making a difference in the lives of those affected by HIV in Canada and around the world.

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