Cameroon suspended tests of an anti-AIDS pill following protests that the trial was unethical.
Activists criticising the trial's "lack of transparency" claim that sex workers on whom the drug was being tested were not made fully aware of the potential risks involved in participation, and that they were not being provided with adequate healthcare.
The one-year study of 400 sex workers, which was being funded by the Bill and Melinda Gates Foundation and run by Family Health International, began in September 2004 to test whether an existing antiretroviral drug called tenofovir could prevent HIV infection.
Tenofovir, made by US pharmaceutical company Gilead Sciences, has been used in several countries, including Canada, France and the United States, to treat HIV infection for the past three years.
Half of the trial participants — who were only enrolled if they were not infected with HIV at the start of the trial — were given the drug, and the other half were given a placebo.
AIDS activists protesting against the trial, including French organisation Act-Up Paris, called for the research to be suspended because of concerns that sex workers taking part in the study were not being provided adequate healthcare, or counselling on safe sex.
Last year, protests by Act-Up Paris led to the suspension of the same trial when it was being run in Cambodia (see Cambodia's prime minister halts AIDS drug trial).
A statement on Act-Up Paris's website describes the trial's alleged provision of five counsellors and one doctor for all 400 participants as "clearly insufficient, even ridiculous".
The organisation also condemns the trial's current strategy of referring women who become infected during the trial to the state health system for treatment, and says the participants should be given free antiretroviral drugs.
Act-Up Paris questioned the ethics of targeting a vulnerable population who would agree to participate in the trial for little in exchange.
Last month, the government of Cameroon set up an independent commission to investigate the allegations. The study had received ethics approval from Cameroon's Ministry of Health and from international review boards in Cameroon and the United States.
Health minister Urbain Olanguena Awono, who had agreed to stop the trial if the accusations were validated, announced the suspension of the trial citing "dysfunctions" that had come to light. He added that "certain corrective measures need to be taken by the research team."
Similar trials of the same drug are taking place in Nigeria and Ghana. Act-Up Paris is planning to protest against these as well, and against trials of tenofovir in injecting drug users that are taking place in Malawi and Thailand, according to Khalil Elouardighi, a spokesperson for the organisation.
Elouardighi said Act-Up Paris is opposing the trials in Malawi and Thailand because the US government is paying for the trial but not providing participants with clean needles.
The suspension of the trial in Cameroon comes one month after the launch of an initiative designed to boost the role of ethics in medical research undertaken in Africa (see Africa and Europe create ethics network).
Read more about research ethics in SciDev.Net's Ethics of research dossier