New drugs for old.

The use of highly active antiretroviral therapy (HAART) has led to the emergence of viral isolates with resistance-associated mutations. Currently, new cases of highly resistant HIV infections associated with rapid progression to AIDS are being reported. The features of a new drug for HIV treatment must include selective potent activity against wild-type virus as well as against mutant virus that has been selected by the use of current antiretroviral treatment regimens. As patients in industrialised countries may live with HIV infection for decades, new drugs must also encourage adherence with simplified dosing regimens associated with favourable toxicity profiles. The replacement of older therapies with newer drugs that avoid cross resistance, even within the same class of antiretroviral, represents a new hope in retroviral targeting.