February 1, 2010
Simplifying HIV regimens by using one HIV drug (monotherapy) instead of regimens with drugs from different drug classes is seeing more progress. Fewer side effects may be the result with this simplification, as well as less cost and resistance with other drug classes. Proving that monotherapy is once again safe and effective remains difficult, especially since using only one drug to treat HIV disease has been proven much less effective due to resistance ever since the second NRTI came to market in the 80s.
However, there has been great interest in using boosted PIs as monotherapy since they are generally more potent in controlling HIV. More than a dozen monotherapy studies are ongoing or have been completed. Most of the results so far have not been promising, though they have mostly come from using Kaletra (lopinavir/ritonavir). Prezista (darunavir) and Reyataz (atazanavir) are two other PIs now under study.
Early 48-week data from the 144-week international MONET study were released in January 2010 and show relatively good results. MONET followed 256 people who had been on stable regimens for at least 24 weeks (<50 copies viral load) and had never had to change regimens due to drug failure.
Half the participants switched their regimens to boosted Prezista monotherapy while the other half switched to boosted Prezista + 2 NRTIs. Four out of 5 in the study were men and 9 in 10 were white. Average age was 44 years and the average CD4 count was 574. After 48 weeks, both arms controlled HIV below 50 copies equally. CD4 counts remained stable in both groups. Surprisingly, the monotherapy group had a similar level of side effects as those taking 3 drugs. Two of the reasons for these results could be contributed to boosted Prezista's long half-life and its ability to better control HIV than other PIs.
More studies need to be done before HIV monotherapy can be a viable option. PIs generally do not penetrate the central nervous system as well as other HIV drug classes, which may be important for controlling HIV in the brain. Also, using monotherapy as a person's first regimen is now being followed in the MONOI study, though early data differ somewhat from MONET.
Studies in other situations are also needed as people with a serious co-infection like hepatitis C seem to not do as well on HIV monotherapy. The biggest concern, drug resistance, will not be known for some time, so the effectiveness of this type of therapy needs to be confirmed in larger studies with longer-term follow-up.