HIV Drug Resistance Causing Growing Concern and Rush for New Medication Development
A new study confirms the rising trend of resistance to a key drug used to treat and prevent HIV infection. It also seems likely the resistant strain of HIV can be transmitted from person to person, facilitating the spread of resistance. This has serious implications for the management of HIV globally and adds urgency to the drive for development of new drugs.
The antiretroviral drug tenofovir is highly effective and largely free of side effects, which makes it the drug of choice. Tenofovir belongs to a class of drugs called nucleotide reverse transcriptase inhibitors (NRTIs) and works by decreasing the amount of HIV in the patient’s body. With less active virus to fight, the weakened immune system to devote more resources to keeping secondary bacterial infections (which might otherwise be life-threatening) in check.
Tenofovir is used both to treat the virus and prevent the spread of HIV. Experts currently advise HIV-negative homosexuals to take tenofovir in order to protect themselves from infection. If strains of HIV become tenofovir-resistant this would undermine an important strategy for control of the disease.
Alternatives to tenofovir have a greater incidence of side effects and are considerably more expensive. For developing countries, especially where lack of medical care and poverty are already complicating factors, the loss of this drug has major implications for the worldwide control and treatment of HIV.
Drug resistance develops when patients don’t take their medications regularly and skip doses. Compliance below 85–90% creates conditions conducive to developing tenofovir resistance. This problem was first highlighted when researchers from University College, London analyzed data from 2,000 patients who had symptoms of uncontrolled HIV infection despite being on antiretroviral medications.
The analysis revealed that 60% of patients from sub-Saharan Africa and 20% of European patients had a strain of HIV that was resistant to the most common treatment, tenofovir. In addition, these patients had levels of HIV in their blood stream that was high enough to be infectious. This raises the specter of resistant HIV passing between individuals and further spreading drug resistance.
It is believed drug resistance is widespread in sub-Saharan Africa because of the lack of patient monitoring. In that environment, the virus has greater chances to mutate and go unnoticed in its resistant form, which facilitates further mutation. Unfortunately, the prevalence of HIV also means a greater risk of transmission between individuals and resistance spreading.
Scientists are anxious to avoid a similar situations to antibiotic resistance, where first line drugs become useless and therapy depends on stronger, last-resort treatments. Research into new antivirals is ongoing but it will take some years for these new drugs to become available. In the short term, it is essential that all countries implement rigorous monitoring of HIV patients so indicators of resistance are detected early and steps taken to prevent its spread.