A growing number of HIV patients in Britain are in danger of running out of treatment options because their virus has become resistant to the drug combinations they have been taking, scientists said on Friday. A study of more than 16,000 patients treated between 1996 and 2002 showed more and more are running the risk of exhausting all options after switching drug cocktails several times, and will depend on the development of new drugs. "If you are looking at the number of all patients treated for HIV in the UK, you find 5 to 6 percent who we believe have experienced treatment exhaustion," Professor Caroline Sabin, who headed the study, said. "We need to continue to monitor the situation. There needs to be new drugs that are easier to take and less cross-resistant to other drugs." Most HIV patients are treated with a combination of drugs called highly active antiretroviral therapy (HAART) to help suppress the virus and keep it from damaging the immune system. But resistance develops eventually in most patients. With only three main classes of drugs used in mainstream HIV treatment, combinations can become exhausted said Sabin, an epidemiologist at London's Royal Free and University College Medical School, who reported the findings in the British Medical Journal. "While the patient had it under control at some stage, the drugs may (eventually) fail and the patient will need a different combination," Sabin said. --SP 2315 Local Time 2015 GMT