February 22, 2009
In oral presentations at CROI 2009 in Montreal, Canada, results from two studies show that switching from a stable and effective Kaletra (lopinavir/ritonavir) regimen to one with the new integrase inhibitor Isentress (raltegravir) results in similar (though slightly less robust) levels of HIV suppression, yet improved the levels of blood fats (lipids). The percent of people maintaining optimal viral suppression was slightly higher among those on Kaletra in both studies. Side effects were similar between the groups, though Isentress did not cause the abnormal lipid levels seen in regimens with Kaletra.
The two identical studies (called SWITCHMRK 1 and 2) enrolled 702 people who were on stable regimens with Kaletra. Average CD4 counts were above 400, average age was about 42, and 80% were men. Some volunteers showed resistance mutations for NRTIs, NNRTIs and PIs, and many had extensive therapy experience and had regimens fail one or more times. All were off lipid-lowering drugs for at least 12 weeks before study start.
In both, volunteers took at least 2 NRTIs and either stayed on Kaletra or switched to Isentress. After 24 weeks in SWITCHMRK 1, 81% of those on Isentress and 87% on Kaletra reached undetectable viral loads. In SWITCHMRK 2, 88% of those on Isentress and 94% on Kaletra achieved undetectable viral suppression.
At week 12, Isentress showed better results for changes in total cholesterol and triglycerides. As for suppressing HIV levels at week 24, 88% of those on Isentress had reached undetectable viral loads while 94% of those on Kaletra were undetectable. The rate of side effects were similar between the two drugs (Isentress 13% and Kaletra 20%.)
For those who switched to Isentress, the drug was well tolerated with somewhat milder side effects and improved lipid levels compared to Kaletra. Isentress didn't suppress HIV quite as well as Kaletra, though its suppression was similar.