New data reported at the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in Chicago suggest that Norvir (ritonavir)-boosted Lexiva (fosamprenavir) is similar to Kaletra (ritonavir-boosted lopinavir) in terms of long-term safety and effectiveness. The 96-week results from an extension of the KLEAN study help establish Lexiva as a useful treatment option for HIV-positive people beginning antiretroviral therapy for the first time.
The KLEAN study involved 878 American, European and Canadian HIV-positive patients beginning their first HIV drug regimen. The official 48-week results were reported at the 16th International AIDS Conference in Toronto in 2006. The follow-up data, reported at ICAAC, reflect an additional year of treatment among some patients remaining in the study.
The patients were randomly assigned to take one 700mg Lexiva tablet plus one 100mg Norvir capsule or three Kaletra capsules (Kaletra capsules have now been replaced by a tablet formulation and only requires two pills per dose). Both Norvir-boosted Lexiva and Kaletra were taken twice a day. All patients also took an Epzicom tablet (600mg abacavir plus 300mg lamivudine) once a day. A total of 434 patients were in the Lexiva group; 444 patients were in the Kaletra group.
The primary goal of the study was to determine the percentage of patients in each group with viral loads below 400 after 48 weeks of treatment. The researchers also looked at the percentage of patients with viral loads below 50, along with changes in CD4 cell counts (T-cell counts) and side effects.
Upon entering the study, patients had relatively high viral loads, with the majority (54 percent) starting treatment with viral loads above 100,000 copies. The CD4 cell count was relatively low, at an average of 192 (17 percent had a CD4 count below 50).
Patients in Europe and Canada who had viral loads below 400 copies at the 48-week mark were permitted to continue in the study for a total of 144 weeks (U.S. participants completed the study after 48 weeks). The 96-week extended study data reported at ICAAC involved 104 patients in the Lexiva group and 92 patients in the Kaletra group.
Approximately 93 percent of those in the Lexiva group who continued treatment for almost two years had viral loads below 400, compared to 87 percent in the Kaletra group. There was no statistically significant difference between the two groups. Additionally, 85 percent of the 105 patients remaining in the Lexiva group and 75 percent of the 91 patients in the Kaletra group had viral loads below 50.
As for immune recovery, CD4 cell counts increased by 292 in the Lexiva group after 48 weeks of treatment, compared to a 286-cell gain in the Kaletra group. Again, there were no statistically significant differences between the two groups.
In terms of side effects, mild-to-moderate diarrhea was the most common and was seen in 16 percent of patients in the Lexiva group and 11 percent in the Kaletra group. Approximately 2 percent of patients in both groups had moderate-to-severe diarrhea.
Changes in blood fats were also similar in the two treatment groups. Total cholesterol increased by an average of 42 mg/dL over 96 weeks of treatment in the Lexiva group, compared with a 57 mg/dL increase in the Kaletra group. Triglycerides increased by 79 mg/dL in the Lexiva group over 96 weeks, compared with an 82 mg/dL increase in the Kaletra group.
While one patient in each treatment group experienced a viral load rebound during the extension phase of the study, no major drug-resistance mutations were found.
These results, the presenters conclude, confirm the long-term effectiveness and safety of Lexiva/Norvir and Kaletra for up to 96 weeks. Final data, involving 144 weeks of follow-up, will be presented next year.
Source:
Pulido F, Baril JG, Staszewski S, et al. Long-term efficacy and safety of fosamprenavir + ritonavir (FPV/r) versus lopinavir/ritonavir (LPV/r) over 96 weeks [Abstract H-361]. 47th Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, 2007.
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