A small pilot study has shown that ritonavir-boosted lopinavir (Kaletra) taken alone is effective in controlling HIV after up to a year and a half of follow-up. These findings were presented last week at the Tenth European AIDS Conference / European AIDS Clinical Society in Dublin.
Although combinations of three or more antiretroviral drugs are recommended for the treatment of HIV, the use of simpler treatment regimens has been the subject of considerable interest, as it could reduce the cost and side-effects of HIV therapy. Kaletra is a promising agent for use alone, as it has a long half-life in the body and resistance to the drug develops slowly.
The OK study is a small open-label trial being carried out in Spain. Its aim is to assess the anti-HIV activity of simplifying treatment from a successful three-drug combination to Kaletra alone.
The investigators recruited 42 patients for the study, all of whom were taking Kaletra and two nucleoside reverse trasncriptase inhibitors (NRTIs) and had had viral loads below 50 copies/ml for at least six months. The patients were randomised to remain on their Kaletra-based drug combination or to stop taking the NRTIs but continue with Kaletra monotherapy.
After 72 weeks, 81% of the patients taking Kaletra alone had viral loads below 50 copies/ml. This was similar to the proportion in the three-drug group (91%; p = 0.38). The two groups also had similar rises in CD4 cell count (112 vs. 50 cells/mm3; p = 0.31).
Four patients in the monotherapy arm experienced virological failure, but no consistent pattern of resistance mutations in the protease gene was seen. All four patients managed to re-suppress their HIV to below 50 copies/ml after re-introduction of the NRTIs.
The investigators did not observe any serious side-effects across the two arms.
Although these results require confirmation in larger, blinded studies, they suggest that simplification to a Kaletra-only regimen may be a safe and effective approach to reduce drug costs, and possibly, toxicities in patients with HIV.
Pulido F et al. Lopinavir/ritonavir as single-drug for maintenance of HIV-1 viral suppression. A randomized, controlled, open label, pilot, clinical trial (OK study): 72 weeks analysis. Tenth European AIDS Conference / European AIDS Clinical Society, Dublin, abstract PE7.5/5, 2005.