ICAAC Update

From the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), held in Chicago in September

by Enid Vázquez

One year of Isentress

After one year on Isentress (formerly known as MK-0518), 54% of study participants taking it had less than 50 viral load, compared to 9% of the people taking a placebo (dummy pill).

All participants started the study with more than 5,000 viral load, with half of them having more than 50,000 viral load. All had HIV that was drug-resistant to at least three classes of antiviral medication. They had an average of nine years on HIV therapy.

This study of 178 individuals tested three doses of Isentress against placebo, all in combination with optimized background therapy (OBT), the best drug combination that could be put together for them. Halfway through the study, everyone—including the placebo group—was put on 400 mg of Isentress twice a day. The researchers concluded that, “In patients with limited treatment options, MK-0518 at all doses had potent and durable antiretroviral effect through week 48, and was generally well tolerated.”

Does Selzentry change HIV?

Looking at results with almost 800 individuals in studies of Selzentry (maraviroc), Pfizer company researchers concluded that persons for whom the drug stops working may experience reversible suppression of CCR5-tropic viruses.

Selzentry is FDA approved for use in people with CCR5-tropic HIV. CCR5 is a protein on some cells that HIV uses to enter the cell and infect it. There is another protein, however, that HIV can also use, CXCR4. People with CXCR4-tropic HIV generally have more advanced disease. Thus there is concern that by suppressing CCR5 virus, CXCR4 virus can emerge and even dominate. The results of this study, therefore, are welcome news. They indicate that the more gentle CCR5 virus can come back if treatment with Selzentry fails.

Moreover, T-cell increases were higher in the people taking Selzentry compared to the control group even when there was emergence of CXCR4 virus. The researchers also reported that CXCR4-using virus was not associated with Category C events.

TMC-125

Drug resistance information was presented for the still-experimental but coming soon non-nucleoside drug TMC-125 (it’s in the same class of drug as Sustiva and Viramune). Thirteen genetic mutations in HIV were associated with a smaller chance that TMC-125 (etravirine) would work, along with other non-nucleoside mutations. (Mutations are changes in a person’s HIV that makes a drug less likely to be effective.) People with three or more mutations in their virus had the least success with therapy. This group made up 15% of the people taking TMC-125. The presentation combined 24-week results from the DUET-1 and DUET-2 studies, with more than 1,200 participants altogether.

The rash associated with TMC-125 occurred in 17% of people taking it, was usually Grade 1 or 2 (meaning mild), began within two weeks, went away while treatment continued, and was limited to the skin, not to other organs. It was found to be more common in women.

A year of Selzentry

After a year on Selzentry (maraviroc) along with an optimized background regimen, more than half of the people on therapy had less than 400 viral load (undetectable), compared to 22% of the people taking only placebo (dummy pill) plus optimized therapy.

Results are from the MOTIVATE-1 study, which tested once-a-day and twice-a-day Selzentry in people who were highly treatment experienced and whose HIV had extensive drug resistance. They all had more than 5,000 viral load. The presentation reported that treatment safety was about the same for all three groups in the study. At ICAAC, presenter Jay Lalezari, M.D., reported that those people taking Fuzeon for the first time had an added benefit from their therapy.

Prezista vs. Kaletra

Kaletra is one of those drugs to beat, and the newer Prezista is no wallflower. But is it as good as Kaletra? A two-year study comparing the two, called ARTEMIS, provided results from one year.

Prezista boosted with Norvir was found to be non-inferior to Kaletra. In people taking therapy for the first time, 84% of the boosted Prezista folks had less than 50 viral load (undetectable on an ultra-sensitive test) compared with 78% of those on Kaletra. Presenter Edwin DeJesus, M.D., reported, however, that a different analysis could not find that Prezista was superior. Still, not bad results for Prezista at all, especially when you consider the notorious Kaletra gastrointestinal (GI) side effects, like diarrhea. Both the tablet form of Kaletra as well as the older capsule formula were used.

Almost half of the people on Kaletra experienced GI effects (47%), compared with 23% (almost one in four) of the people taking Prezista. The Prezista group also had fewer lipid elevations, another side effect associated with Kaletra (as well as other of the HIV protease inhibitor drugs).
The report also noted that people who started therapy with more than 100,000 viral load or less than 200 CD4 T-cells did better on Prezista. Everyone in this study (about 700 participants) received Truvada in addition to their Kaletra or Prezista. (See also IAS report.)

For more information, visit www.icaac.org, www.thebody.com, and www.clinicaloptions.com.