— An antiviral drug widely used to treat hepatitis B causes some people with HIV to become rapidly resistant to their medication, a new study suggests.
The finding could have major implications for over four million people worldwide who are jointly infected with hepatitis B and HIV.
Chloe Thio and colleagues at Johns Hopkins University in Baltimore, Maryland, US, investigated the drug entecavir, a leading treatment for hepatitis B. Thio had heard reports that the drug sold as Baraclude had demonstrated anti-HIV activity in two HIV patients who were taking the drug for hepatitis B.
Working in the lab, the researchers combined the drug with healthy blood samples and a non-virulent form of HIV. At low concentrations of entecavir, the drug dramatically slashed the number of newly infected cells by 50%.
But the drug also caused a mutation in the virus, they found. This so-called "M184V mutation" inhibited further HIV suppression, even when higher doses of the drug were used. Worse, the mutation stopped other anti-HIV drugs from treating the immunological disease, including lamivudine the mainstay of many HIV drug-combination therapies.
To confirm that entecavir was the culprit, the team then tested blood samples from one of the patients jointly infected with HIV and hepatitis B that had exhibited anti-HIV activity. Blood samples taken from the patient before taking entecavir had no M184V mutations in the HIV. After six months of entecavir treatments, 96% of viral samples from the patients blood had the mutation.
On 24 February, the US Food and Drug Administration posted a letter from Bristol-Myers Squibb, the drug's makers, warning health care providers about potential risks after Thio notified both organisations of her findings.
The drug maker has also recently revised labelling on the drug to state that it has not been evaluated in patients who are infected with both hepatitis B and HIV who were simultaneously receiving HIV treatment.
"Health officials should alert co-infected individuals immediately that they should not be taking entecavir alone, says Thio.
This is really a big blow in terms of hepatitis B and HIV treatment, says Rowena Johnston, vice president for research at the American Foundation for AIDS Research. Johnston, who was not involved in the study, says that for people infected with both viruses, it is best to treat hepatitis B first since it is curable, before tackling HIV.
Moreover, while early treatment of hepatitis B can reduce liver damage, HIV treatments are most effective later on, after the virus has weakened the bodys immune system.
The studys findings were presented at the Conference on Retroviruses and Opportunistic Infections in Los Angeles, California, US, on 28 February.