The clinical trial finding that a once-daily pill halved HIV infection among people who inject drugs in Thailand is an important development in HIV prevention science, and brings welcome attention to a group often excluded from clinical trials.
The Bangkok Tenofovir Study was the first study of its kind examining a once-a-day HIV prevention method known as PrEP, or pre-exposure prophylaxis, among a population of injection drug users in Thailand. The study gave a single tenofovir pill, along with counseling and risk reduction education to half of study participants, and offered placebo and counseling and risk reduction to the other half. Results showed overall reduction of almost 50 percent among those who received the medicine, and reduction of 74 percent for those who adhered best to the daily regimen.
While the results of this study are striking, so is the difficulty of assessing the relevance of these clinical trial results for most of the world.
Firstly, this study had an ethical obligation to compare the pharmaceutical intervention with needle and syringe programs -- the recognized standard for HIV prevention among people who inject drugs. This standard was not observed, since the government in Thailand fails to offer needles and syringes through government programs. The omission means we lost a real opportunity to see how this daily pill compared to standard harm reduction services.
In countries where people who inject drugs do not even have access to antiretroviral treatment, translating the results of this clinical trial present a number of challenges. Trial participants were paid to come to the clinic and take medicine -- ordinary patients are not. For injecting drug users in many countries, going for an HIV test or even admitting that you have used drugs can result in the addition of your name to government registries shared with police. PrEP would require at least quarterly HIV testing for people who inject drugs offered the medicine.
This trial relied primarily on directly observed therapy, meaning that most study participants had to come daily to receive the medicines. Contrary to Donald McNeil's misleading assertion in the New York Times that justified this approach by noting that addicts are "notoriously unreliable" and might otherwise sell their medication, this is not a sensible requirement of treatment for people who inject drugs. Without building trust or willingness to work with individuals, health services will have no ability to deliver medicines in this way.
The clinical trial also controlled away one of the greatest threats to the health of people who use drugs -- detention and incarceration. Thailand, for example, forces tens of thousands of people who use drugs annually into compulsory drug "treatment" or prison. The Bangkok Tenofovir Study ensured that those imprisoned during the study had continued daily access to medicine. This is a great exception to the rule in much of the world, which is interruption of treatment for those imprisoned or detained.
PrEP also does nothing to prevent hepatitis C infection, abscesses, endocarditis or other ills associated with contaminated injecting equipment. In the US, the Centers for Disease Control and Prevention is urging that PrEP be used in conjunction with other prevention measures such as methadone, and sterile needles and syringes.
This clinical trial was meant to demonstrate efficacy of a medicine -- not to answer all the questions raised by its success. Different kinds of investigation will now be needed to see if prevention in a pill is an idea with practical application, and whether the incentives and flexibilities that helped retain trial participants might also be used to improve HIV services generally for people who inject drugs. Without such reform, we should worry about what PrEP might look like in countries like Russia and Thailand, which have demonstrated no willingness to support needle and syringe programs, but great readiness to punish and incarcerate. Pharmaceuticalization of HIV prevention for injecting drug users without corresponding reform in law enforcement and healthcare delivery is in no one's interest, and will result in money wasted, new infections, and lives lost.