A once-daily dose of ritonavir-boosted darunavir (Prezista) may be an option for some treatment-experienced patients, according to a small study published in the October 1st edition of the Journal of Acquired Immune Deficiency Syndromes.
The investigators found that patients taking a once-daily 800/100mg dose of darunavir/ritonavir were as likely as those taking the standard twice-daily dose of 600/100mg to achieve an undetectable viral load. Increases in CD4 cell count were also similar between the patients taking the two darunavir/ritonavir doses. Importantly, the study was restricted to patients who did not have any resistance to darunavir and the researchers are calling for further studies to evaluate the use of once-daily darunavir/ritonavir in such patients.
HIV treatment is becoming increasingly tolerable and easy to take. In late 2007, treatment consisting of one pill, once a day (Atripla, efavirenz, tenofovir and FTC) was approved in the UK and Europe. Once-daily protease inhibitor treatment is also available, with ritonavir-boosted atazanavir (Reyataz) approved for both treatment-naïve and treatment-experienced patients, and there is some evidence that once-daily doses of Kaletra (lopinavir/ritonavir) can also be safe and effective.
Furthermore, information from the ongoing ARTEMIS study suggests that treatment-naïve patients who take once-daily darunavir/ritonavir as part of their HIV treatment are more likely to achieve an undetectable viral load than individuals who take HIV treatment that includes Kaletra.
The use of darunavir/ritonavir in the UK and Europe is currently restricted to treatment-experienced patients (in the US, however, the drug was recently approved for patients starting HIV treatment for the first time). The approved dose of darunavir/ritonavir is 600/100mg twice-daily in combination with other antiretrovirals.
Investigators wanted to see if an 800/100mg once-daily dose of darunavir/ritonavir was effective and safe in treatment-experienced patients who did not have any resistance to darunavir. Darunavir/ritonavir was approved on the basis of the POWER 1 and POWER 2 studies, and researchers looked at the results from the phases of this study that examined the safety and effectiveness of various doses of the drug.
A total of 23 patients took a once-daily 800/100mg dose of darunavir/ritonavir, 29 patients received a twice-daily 600/100mg dose, and 28 patients received a comparator protease inhibitor. All the patients also received other anti-HIV drugs selected after resistance testing. The study lasted 24 weeks.
After this time, 67% of patients who received the once-daily dose of darunavir/ritonavir had an undetectable viral load (below 50 copies/ml) compared to 62% of those who received the twice-daily dose. This 5% difference was not statistically significant, and both doses of darunavir/ritonavir were more likely to yield an undetectable viral load than the comparator protease inhibitors (11%, p
Falls in viral load from baseline were also comparable between the patients who received darunavir/ritonavir once daily (fall of 2.39 log10) and twice daily (fall of 2.35 log10). Once again both doses of darunavir/ritonavir out-performed the comparator protease inhibitors (fall of 0.68 log10, p
Increases in CD4 cell count were comparable between patients receiving darunavir/ritonavir once daily (mean increase, 88 cells/mm3) and twice daily (mean increase, 111 cells/mm3) and were significantly higher than those seen in patients taking other protease inhibitors (mean increase, 33 cells/mm3, p
“Although the numbers of patients in each of the subgroups were relatively small, these results provide a rationale for further studies with darunavir/r[itonavir] 800/100mg once daily as a therapeutic option for treatment-experienced patients who have no baseline darunavir [resistance]”, conclude the investigators.