No primary protease inhibitor (PI) resistance was reported in anti-retroviral-naïve patients taking a Kaletra (lopinavir/ritonavir)-based regimen through six years (300 weeks) of therapy, according to the data, presented at the 44th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

The results also showed the majority of patients taking Kaletra in combination with other antiretroviral agents maintained an undetectable viral load, (amount of virus in the blood) of less than 50 copies per milliliter, as measured by HIV RNA, through six years of therapy, a release from Abbott said here.

Constance Benson, professor of medicine, University of Colorado Health Sciences Centre, Division of Infectious Diseases said, "Kaletra, as part of an initial treatment regimen, is a good example of how far we have come in being able to provide patients with long-term HIV treatment options that include durable viral suppression and a favourable resistance profile."

"There are few HIV clinical trials with six years of data, and we are encouraged that no primary protease resistance has been seen in patients taking Kaletra as part of their initial treatment regimen over the extended duration of this trial," Scott Brun, divisional vice president, Infectious Disease Development, Abbott said adding, "Approaching six years of clinical study, a Kaletra-based regimen demonstrated its ability to meet the pressing needs in HIV therapy, long-term viral suppression, immunological benefit and tolerability."

Patients in this open-label study, in which there was no comparator group, were given one of three doses of Kaletra in addition to the nucleoside analogues stavudine and lamivudine. After 48 weeks of therapy, all patients were converted to the same dose of Kaletra (400/100 mg twice-daily) with stavudine and lamivudine.