AEGiS-CATIE: Double Protease therapy?

Double Protease therapy?

TreatmentUpdate84 - Vol. 9, No. 10 - pp. 1-2; December, 1997
Sean Hosein

In an attempt to increase the anti-HIV activity of treatment regimens, doctors are now testing combinations of two protease inhibitors. These drugs interact with one another, usually increasing the amount of at least one of them that gets into the blood, as well as perhaps increasing the time the drugs remain in the blood. Much of the information on double protease combinations comes from small studies.

Ritonavir/Saquinavir

Ritonavir can increase the amount of saquinavir in the blood by twenty times compared to levels seen when saquinavir is taken alone. The most commonly used dose seems to be 400/400 mg; that is, 400 mg of each drug taken twice daily. In a study of 141 subjects who had never used protease inhibitors before, 75% had virus levels that fell below 200 copies. After 1 year of this regimen, which also combined AZT and related drugs in some subjects, 90% of subjects had viral loads of less than 200 copies. Some subjects received larger doses--600/600 mg or 400/400 mg three times daily, but ultimately these were no more effective as the now standard 400/400 mg twice daily regimen.

Nelfinavir and Fortovase

Nelfinavir increases the amount of saquinavir that gets into the blood by nearly 400 percent. One combination currently being tested is nelfinavir 750 mg and saquinavir 800 mg both taken 3 times daily. After 4 months, 9 subjects remained in the study taking just the 2 drugs. In 50% of subjects, the viral load fell to 1/100th of its pre-study level and CD4+ counts increased by 117 cells. All subjects in this study had never used a protease inhibitor before. Other combinations being tested include nelfinavir and the new formulation of saquinavir called Fortovase. More news on Fortovase appears later in this issue of TreatmentUpdate.

Indinavir versus Fortovase

In a Dutch study called CHEESE, PHAs who had never used a protease inhibitor before received AZT/3TC and either indinavir or Fortovase (1200 mg three times daily). After 3 months, viral load fell 200 fold in both groups. Interestingly, 50% of the Fortovase group had an increase of 124 CD4+ cells, while in the indinavir group the increase was 49 cells. The difference was not statistically significant. However, detailed analyses from this trial will be eagerly awaited by doctors and their patients who would like to find out if Fortovase somehow is less toxic to the bone marrow or has a more beneficial effect on the immune system than indinavir.

REFERENCES:

1. Anonymous. Double protease inhibitors--new gold standard in HIV. SCRIP 1997;2274;18-19.

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