Almost two-thirds of highly treatment-experienced patients who switched from standard multi-drug antiretroviral therapy to Kaletra monotherapy achieved and maintained an undetectable viral load for over a year, according to a small, single-site study presented to the Twelfth Annual Conference of the British HIV Association in Brighton on March 31st.
A number of studies have provided encouraging results about the potency and safety of monotherapy with the protease inhibitor Kaletra (lopinavir boosted by ritonavir). These studies have been conducted in treatment-naïve and virologically suppressed treatment experienced patients.
Investigators from London’s Chelsea and Westminster Hospital gathered data on treatment-experienced patients who had switched to Kaletra monotherapy outside of a clinical trials setting and within the context of routine HIV care.
In total, 35 patients were identified with a median CD4 cell count of 248 cells/mm3 and a median viral load of just under 55,000 copies/ml. These individuals had taken a median of five previous antiretroviral regimens before switching to Kaletra monotherapy. Five individuals were lost to follow-up and two patients stopped taking Kaletra monotherapy because of side-effect. This meant that data for 28 patients were analysed by the investigators who looked for changes in CD4 cell count and viral load in the twelve-month period following the switch to monotherapy.
A viral load below 50 copies/ml was achieved by 14 individuals (50%) and 73% experienced a 1 log10 reduction in viral load. CD4 cell count increased by a mean of 115 cells/mm3 after switching in patients who achieved an undetectable viral load and by a mean of 73 cells/mm3 in individuals whose viral load remained detectable.
The investigators also looked at the effectiveness of Kaletra monotherapy in patients with pre-existing resistance to protease inhibitors. Resistance tests performed prior to the treatment change identified five individuals with major mutations conferring resistance to protease inhibitors. Of these five patients three had a response to treatment, with two experiencing a fall in their viral load fall to below 50 copies/ml, another a decline in viral load to under 400 copies/ml. These three patients also experienced an increase in their CD4 cell count.
Resistance tests during Kaletra monotherapy were performed on ten additional patients. Of these, two developed new minor protease inhibitor mutations.
Most patients remained on Kaletra monotherapy for the twelve months of the study, but eight individuals switched therapy – three due to virological failure, two because of viral load ‘blips,’ two for unclear reasons, and one for immunological failure.
Of the 20 remaining individuals, twelve (60%) had an undetectable viral load after a mean of 14 months treatment with Kaletra monotherapy.
The investigators believe that this treatment strategy might be particularly useful for treatment-experienced patients with adherence problems.
Waters L et al. Kaletra monotherapy – a real-life experience. HIV Med 7 (Supplement 1), abstract P9, 2006.